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<?rfc toc="yes"?> <rfc xmlns:xi="http://www.w3.org/2001/XInclude" ipr="trust200902" docName="draft
<?rfc tocdepth="4"?> -ietf-rats-tpm-based-network-device-attest-14" number="9683" submissionType="IET
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<rfc ipr="trust200902" docName="draft-ietf-rats-tpm-based-network-device-attest- 14" category="info">
<front> <front>
<title abbrev="Network Device RIV">TPM-based Network Device Remote Integrity <title abbrev="Network Device RIV">Remote Integrity Verification of Network
Verification</title> Devices Containing Trusted Platform Modules</title>
<seriesInfo name="RFC" value="9683"/>
<author initials="G. C." surname="Fedorkow" fullname="Guy Fedorkow" role="ed <author initials="G. C." surname="Fedorkow" fullname="Guy C. Fedorkow" role=
itor"> "editor">
<organization>Juniper Networks, Inc.</organization> <organization>Juniper Networks, Inc.</organization>
<address> <address>
<postal> <postal>
<street>10 Technology Park Drive</street> <street>10 Technology Park Drive</street>
<city>Westford</city> <city>Westford</city>
<region>Massachusetts</region> <region>Massachusetts</region>
<code>01886</code> <code>01886</code>
<country>US</country> <country>United States of America</country>
</postal> </postal>
<phone></phone> <phone/>
<email>gfedorkow@juniper.net</email> <email>gfedorkow@juniper.net</email>
</address> </address>
</author> </author>
<author initials="E." surname="Voit" fullname="Eric Voit"> <author initials="E." surname="Voit" fullname="Eric Voit">
<organization abbrev="Cisco">Cisco Systems</organization> <organization abbrev="Cisco">Cisco Systems</organization>
<address> <address>
<email>evoit@cisco.com</email> <email>evoit@cisco.com</email>
</address> </address>
</author> </author>
<author initials="J." surname="Fitzgerald-McKay" fullname="Jessica Fitzgeral d-McKay"> <author initials="J." surname="Fitzgerald-McKay" fullname="Jessica Fitzgeral d-McKay">
skipping to change at line 53 skipping to change at line 48
<postal> <postal>
<street>9800 Savage Road</street> <street>9800 Savage Road</street>
<city>Ft. Meade</city> <city>Ft. Meade</city>
<region>Maryland</region> <region>Maryland</region>
<code>20755</code> <code>20755</code>
<country>US</country> <country>US</country>
</postal> </postal>
<email>jmfitz2@nsa.gov</email> <email>jmfitz2@nsa.gov</email>
</address> </address>
</author> </author>
<date year="2024" month="November"/>
<area>sec</area>
<workgroup>rats</workgroup>
<date year="2022" month="March" day="22"/> <keyword>Attestation</keyword>
<keyword>TPM</keyword>
<area>Security</area>
<workgroup>RATS Working Group</workgroup>
<keyword>Internet-Draft</keyword>
<abstract> <abstract>
<t>This document describes a workflow for remote attestation of the integr
<t>This document describes a workflow for remote attestation of the integrity of ity of firmware and software installed on network devices that contain Trusted P
firmware and software latform Modules (TPMs), as defined by
installed on network devices that contain Trusted Platform Modules <xref target= the Trusted Computing Group (TCG), or equivalent hardware implementations that i
"TPM1.2"/>, <xref target="TPM2.0"/>, as defined by nclude the protected capabilities, as provided by TPMs.</t>
the Trusted Computing Group (TCG)), or equivalent hardware implementations that
include the protected capabilities, as provided by TPMs.</t>
</abstract> </abstract>
</front> </front>
<middle> <middle>
<section anchor="introduction" numbered="true" toc="default">
<section anchor="introduction" title="Introduction"> <name>Introduction</name>
<t>There are many aspects to consider in fielding a trusted computing devi
<t>There are many aspects to consider in fielding a trusted computing device, ce,
from operating systems to applications. Mechanisms to prove that from operating systems to applications. Mechanisms to prove that
a device installed at a customer’s site is authentic (i.e., not counterfeit) and a device installed at a customer's site is authentic (i.e., not counterfeit) and
has has
been configured with authorized software, all as part of a trusted supply chain, been configured with authorized software, all as part of a trusted supply chain,
are just a few of the many aspects which need to be considered concurrently to are just a few of the many aspects that need to be considered concurrently to h
have confidence that a device is truly trustworthy.</t> ave confidence that a device is truly trustworthy.</t>
<t>A generic architecture for remote attestation has been defined in <xref
<t>A generic architecture for remote attestation has been defined in <xref targe target="RFC9334" format="default"/>. Additionally, use cases for remotely atte
t="I-D.ietf-rats-architecture"/>. Additionally, use cases for remotely attestin sting networking devices are discussed within Section 5 of <xref target="I-D.ric
g networking devices are discussed within Section 6 of <xref target="I-D.richard hardson-rats-usecases" format="default"/>. However, these documents do not prov
son-rats-usecases"/>. However, these documents do not provide sufficient guidan ide sufficient guidance for network equipment vendors and operators to design, b
ce for network equipment vendors and operators to design, build, and deploy inte uild, and deploy interoperable devices.</t>
roperable devices.</t> <t>The intent of this document is to provide such guidance. It does this b
y outlining the Remote Integrity Verification (RIV) problem and then by identify
<t>The intent of this document is to provide such guidance. It does this by outl ing the necessary elements to get the complete, scalable attestation procedure w
ining the Remote Integrity Verification (RIV) problem, and then identifies eleme orking with commercial networking products such as routers, switches, and firewa
nts that are necessary to get the complete, scalable attestation procedure worki lls. An underlying assumption is the availability within the device of a crypt
ng with commercial networking products such as routers, switches and firewalls. oprocessor that is compatible with the Trusted Platform Module specifications <x
An underlying assumption will be the availability within the device of a Trust ref target="TPM-1.2" format="default"/> <xref target="TPM-2.0" format="default"/
ed Platform Module <xref target="TPM1.2"/>, <xref target="TPM2.0"/> compatible c > to enable the trustworthy, remote assessment of the device's software and hard
ryptoprocessor to enable the trustworthy remote assessment of the device’s softw ware.</t>
are and hardware.</t> <section anchor="requirements-notation" numbered="true" toc="default">
<name>Requirements Notation</name>
<section anchor="requirements-notation" title="Requirements notation"> <t>
The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
<t>The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL NOT</bcp14>
“SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “NOT RECOMMENDED”, “MAY”, and ",
“OPTIONAL” in this document are to be interpreted as described in "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, th "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
ey appear in all "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to
capitals, as shown here.</t> be
interpreted as described in BCP&nbsp;14 <xref target="RFC2119"/> <xref
</section> target="RFC8174"/> when, and only when, they appear in all capitals, as
<section anchor="terminology" title="Terminology"> shown here.
</t>
<t>A number of terms are reused from <xref target="I-D.ietf-rats-architecture"/> </section>
. These include: Appraisal Policy for Evidence, Attestation Result, Attester, E <section anchor="terminology" numbered="true" toc="default">
vidence, Reference Value, Relying Party, Verifier, and Verifier Owner.</t> <name>Terminology</name>
<t>A number of terms are reused from <xref target="RFC9334" format="defa
<t>Additionally, this document defines the following term:</t> ult"/>. These include Appraisal Policy for Evidence, Attestation Result, Attest
er, Evidence, Reference Value, Relying Party, Verifier, and Verifier Owner.</t>
<t>Attestation: the process of generating, conveying and appraising <t>Additionally, this document defines the following term:</t>
<dl>
<dt>Attestation:</dt>
<dd>The process of generating, conveying, and appraising
claims, backed by evidence, about device trustworthiness characteristics, includ ing supply chain trust, claims, backed by evidence, about device trustworthiness characteristics, includ ing supply chain trust,
identity, device provenance, software configuration, device identity, device provenance, software configuration, device
composition, compliance to test suites, functional and assurance evaluations, et composition, compliance to test suites, functional and assurance evaluations, et
c.</t> c.</dd>
</dl>
<t>The goal of attestation is simply to assure an administrator or auditor that <t>The goal of attestation is simply to assure an administrator or audit
the device configuration and software or that the device's configuration and software
that was launched when the device was last started is authentic and untampered-w were authentic and unmodified when the device started.
ith. The determination of software authenticity is not prescribed in this document, b
The determination of software authenticity is not prescribed in this document, b ut it's typically taken to mean
ut it’s typically taken to mean
a software image generated by an authority trusted by the administrator, such as the device manufacturer.</t> a software image generated by an authority trusted by the administrator, such as the device manufacturer.</t>
<t>Within the context of the Trusted Computing Group (TCG), the scope of
<t>Within the Trusted Computing Group (TCG) context, the scope of attestation is attestation is typically narrowed to describe the process by
typically narrowed to describe the process by
which an independent Verifier can obtain cryptographic proof as to the identity which an independent Verifier can obtain cryptographic proof as to the identity
of the device in question, and evidence of the integrity of software loaded on of the device in question, evidence of the integrity of the device's software th
that device when it started up, and then verify that what’s there matches the at was loaded upon
startup, and verification that the current configuration matches the
intended configuration. For network equipment, a Verifier capability can intended configuration. For network equipment, a Verifier capability can
be embedded in a Network Management Station (NMS), a posture collection server, be embedded in a Network Management Station, a posture collection server,
or other network analytics tool (such as a software asset management solution, or other network analytics tool (such as a software asset management solution,
or a threat detection and mitigation tool, etc.). While informally referred or a threat detection and mitigation tool, etc.).
to as attestation, this document focuses on a specific subset of attestation tas This document focuses on a specific subset of attestation tasks, defined here as
ks, defined here as Remote Remote
Integrity Verification (RIV). RIV in this document takes a network-equipment-ce Integrity Verification (RIV), and informally referred to as attestation. RIV in
ntric perspective this document takes a network-equipment-centric perspective
that includes a set of protocols and procedures for determining whether a that includes a set of protocols and procedures for determining whether a
particular device was launched with authentic software, starting from Roots particular device was launched with authentic software, starting from Roots
of Trust. While there are many ways to accomplish attestation, RIV sets of Trust. While there are many ways to accomplish attestation, RIV sets
out a specific set of protocols and tools that work in environments commonly out a specific set of protocols and tools that work in environments commonly
found in network equipment. RIV does not cover other device characteristics found in network equipment. RIV does not cover other device characteristics
that could be attested (e.g., geographic location, connectivity; that could be attested (e.g., geographic location or connectivity;
see <xref target="I-D.richardson-rats-usecases"/>), although it does provide evi see <xref target="I-D.richardson-rats-usecases" format="default"/>), although it
dence of a secure infrastructure does provide evidence of a secure infrastructure
to increase the level of trust in other device characteristics attested to increase the level of trust in other device characteristics attested
by other means (e.g., by Entity Attestation Tokens <xref target="I-D.ietf-rats-e by other means (e.g., by Entity Attestation Tokens <xref target="I-D.ietf-rats-e
at"/>).</t> at" format="default"/>).</t>
<t>In line with definitions found in <xref target="RFC9334" format="defa
<t>In line with <xref target="I-D.ietf-rats-architecture"/> definitions, this do ult"/>, this document uses the term Endorser to refer to the
cument uses the term Endorser to refer to the
role that signs identity and attestation certificates used by the Attester, whil e Reference Values are signed role that signs identity and attestation certificates used by the Attester, whil e Reference Values are signed
by a Reference Value Provider. Typically, the manufacturer of a network device would be accepted as by a Reference Value Provider. Typically, the manufacturer of a network device would be accepted as
both the Endorser and Reference Value Provider, although the choice is ultimatel y up to the Verifier Owner.</t> both the Endorser and Reference Value Provider, although the choice is ultimatel y up to the Verifier Owner.</t>
</section>
</section> <section anchor="document-organization" numbered="true" toc="default">
<section anchor="document-organization" title="Document Organization"> <name>Document Organization</name>
<t>The remainder of this document is organized into several sections:</t
<t>The remainder of this document is organized into several sections:</t> >
<ul spacing="normal">
<t><list style="symbols"> <li>The remainder of this section covers goals and requirements, plus
<t>The remainder of this section covers goals and requirements, plus a top-lev a top-level description of RIV.</li>
el description of RIV.</t> <li>The Solution Overview section (<xref target="solution-overview" fo
<t>The Solution Overview section outlines how Remote Integrity Verification wo rmat="default"/>) outlines how RIV works.</li>
rks.</t> <li>The Standards Components section (<xref target="standards-componen
<t>The Standards Components section links components of RIV to normative stand ts" format="default"/>) links components of RIV to normative standards.</li>
ards.</t> <li>The Privacy and Security Considerations sections (Sections <xref t
<t>Privacy and Security shows how specific features of RIV contribute to the t arget="privacy-considerations" format="counter"/> and <xref target="security-con
rustworthiness of the Attestation Result.</t> s" format="counter"/>) shows how specific features of RIV contribute to the trus
<t>Supporting material is in an appendix at the end.</t> tworthiness of the Attestation Result.</li>
</list></t> <li>Supporting material is in an appendix (<xref target="appendix" for
mat="default"/>).</li>
</section> </ul>
<section anchor="goals" title="Goals"> </section>
<section anchor="goals" numbered="true" toc="default">
<t>Network operators benefit from a trustworthy attestation mechanism that provi <name>Goals</name>
des <t>Network operators benefit from a trustworthy attestation mechanism th
assurance that their network comprises authentic equipment, and has loaded softw at provides
are assurance that their network comprises authentic equipment and has loaded softwa
re
free of known vulnerabilities and unauthorized tampering. In line with the over all goal of assuring integrity, attestation can be used to assist in asset manag ement, vulnerability and compliance free of known vulnerabilities and unauthorized tampering. In line with the over all goal of assuring integrity, attestation can be used to assist in asset manag ement, vulnerability and compliance
assessment, plus configuration management.</t> assessment, plus configuration management.</t>
<t>The RIV attestation workflow outlined in this document is intended to
<t>The RIV attestation workflow outlined in this document is intended to meet th meet the following high-level goals:</t>
e following high-level goals:</t> <ul spacing="normal">
<li>Provable Device Identity - This specification requires that an Att
<t><list style="symbols"> ester (i.e., the attesting device) includes
<t>Provable Device Identity - This specification requires that an Attester (i. a cryptographic identifier unique to each device. Effectively, this means that
e., the attesting device) includes the device's TPM
a cryptographic identifier unique to each device. Effectively this means that t must be provisioned with this during the manufacturing cycle.</li>
he device’s TPM <li>Software Inventory - Key goals are to identify the software releas
must be so provisioned during the manufacturing cycle.</t> e(s) installed
<t>Software Inventory - A key goal is to identify the software release(s) inst on the Attester and to provide evidence that the software stored within hasn't
alled been altered without authorization.</li>
on the Attester, and to provide evidence that the software stored within hasn’t <li>Verifiability - Verification of the device's software and configur
been altered without authorization.</t> ation shows
<t>Verifiability - Verification of software and configuration of the device sh that the software that the administrator authorized for use was actually launche
ows d.</li>
that the software that the administrator authorized for use was actually launche </ul>
d.</t> <t>In addition, RIV is designed to operate either in a centralized envir
</list></t> onment, such as with a central authority that manages and configures a number of
network devices, or "peer-to-peer", where network devices independently verify
<t>In addition, RIV is designed to operate either in a centralized environment, one another to establish a trust relationship. (See <xref target="peer-to-peer"
such as with a central authority that manages and configures a number of network format="default"/>.)</t>
devices, or ‘peer-to-peer’, where network devices independently verify one anot </section>
her to establish a trust relationship. (See <xref target="peer-to-peer"/> below <section anchor="RIV-desc" numbered="true" toc="default">
)</t> <name>Description of Remote Integrity Verification (RIV)</name>
<t>Attestation requires two interlocking mechanisms between the Attester
</section> network device and the Verifier:</t>
<section anchor="RIV-desc" title="Description of Remote Integrity Verification ( <ul spacing="normal">
RIV)"> <li>Device Identity is the mechanism that provides trusted identity, w
hich can reassure network
<t>Attestation requires two interlocking mechanisms between the Attester network
device and the Verifier:</t>
<t><list style="symbols">
<t>Device Identity, the mechanism providing trusted identity, can reassure net
work
managers that the specific devices they ordered from authorized manufacturers fo r managers that the specific devices they ordered from authorized manufacturers fo r
attachment to their network are those that were installed, and that they continu e to attachment to their network are those that were installed and that they continue to
be present in their network. As part of the mechanism for Device Identity, be present in their network. As part of the mechanism for Device Identity,
cryptographic proof of the identity of the manufacturer is also provided.</t> cryptographic proof of the manufacturer's identity is also provided.</li>
<t>Software Measurement is the mechanism that reports the state of mutable sof <li>Software Measurement is the mechanism that reports the state of mu
tware components table software components
on the device, and can assure administrators that they have known, authentic on the device and that can assure administrators that they have known, authentic
software configured to run in their network.</t> software configured to run in their network.</li>
</list></t> </ul>
<t>By using these two interlocking mechanisms, RIV, which is a component
<t>Using these two interlocking mechanisms, RIV is a component in a chain of pro in a chain of procedures, can assure a network operator that the equipment in
cedures that can assure a network operator that the equipment in their network can be reliably identified and that authentic software of
their network can be reliably identified, and that authentic software of
a known version is installed on each device. Equipment in the network includes a known version is installed on each device. Equipment in the network includes
devices that make up the network itself, such as routers, switches and firewalls devices that make up the network itself, such as routers, switches, and firewall
.</t> s.</t>
<t>Software used to boot a device can be identified by a chain
<t>Software used to boot a device can be identified by a chain of measurements, anchored at the start by a Root of Trust for Measurement (RTM)
of measurements, anchored at the start by a Root of Trust for Measurement (see < (see <xref target="root-of-trust" format="default"/>). An attestation function e
xref target="root-of-trust"/>), each measuring the next stage and recording the mbedded in each stage, verified by the previous stage, measures the next stage
result in tamper-resistant storage, and records the result in tamper-resistant storage.
normally ending when the system software is fully loaded. A measurement signifies the identity, integrity, and version of each
A measurement signifies the identity, integrity and version of each software component registered with an Attester's TPM <xref target="TPM-1.2" form
software component registered with an Attester’s TPM <xref target="TPM1.2"/>, <x at="default"/> <xref target="TPM-2.0" format="default"/> so that a
ref target="TPM2.0"/>, so that a
subsequent verification stage can determine if the software subsequent verification stage can determine if the software
installed is authentic, up-to-date, and free of tampering.</t> installed is authentic, up-to-date, and free of tampering.</t>
<t>RIV includes several major processes, which are split between the Att
<t>RIV includes several major processes, split between the Attester and Verifier ester and Verifier:</t>
:</t> <ol spacing="normal" type="1"><li>Generation of Evidence is the process
whereby an Attester generates cryptographic
<t><list style="numbers">
<t>Generation of Evidence is the process whereby an Attester generates cryptog
raphic
proof (Evidence) of claims about device properties. In particular, the proof (Evidence) of claims about device properties. In particular, the
device identity and its software configuration are both of critical importance.< device identity and its software configuration are both of critical importance.<
/t> /li>
<t>Device Identification refers to the mechanism assuring the <li>Device Identification refers to the mechanism assuring the
Relying Party (ultimately, a network administrator) of the identity of devices t Relying Party (ultimately, a network administrator) of the identities of devices
hat make up their network, , and the identities of their manufacturers, that make up their network.</li>
and that their manufacturers are known.</t> <li>Conveyance of Evidence
<t>Conveyance of Evidence reliably transports the collected Evidence from the Attester to a Verifier to a
reliably transports the collected Evidence from Attester to a Verifier to allow llow a management station to perform
a management station to perform
a meaningful appraisal in Step 4. The transport a meaningful appraisal in Step 4. The transport
is typically carried out via a management network. is typically carried out via a management network.
While not required for reliable attestation, an encrypted channel may be used t o Although not required for reliable attestation, an encrypted channel may be use d to
provide integrity, authenticity, or confidentiality once attestation is complet e. provide integrity, authenticity, or confidentiality once attestation is complet e.
It should be noted that critical attestation evidence from the TPM is signed by a key known only to TPM, and is not It should be noted that critical attestation evidence from the TPM is signed by a key known only to TPM, and is not
dependent on encyption carried out as part of a reliable transport.</t> dependent on encryption carried out as part of a reliable transport.</li>
<t>Finally, Appraisal of Evidence occurs. This is the process of verifying th <li>Finally, appraisal of evidence occurs. This is the process of ver
e Evidence received by ifying the Evidence received by
a Verifier from the Attester, and using an Appraisal Policy to develop an a Verifier from the Attester and using an Appraisal Policy to develop an
Attestation Result, used to inform decision-making. In practice, this means c Attestation Result, which is used to inform decision-making. In practice, thi
omparing s means comparing
the Attester’s measurements reported as Evidence with the device configuration the Attester's measurements reported as Evidence with the device configuration
expected expected
by the Verifier. Subsequently, the Appraisal Policy for Evidence might by the Verifier. Subsequently, the Appraisal Policy for Evidence might
match Evidence found against Reference Values (aka Golden Measurements), which represent match Evidence found against Reference Values (aka Golden Measurements), which represent
the intended configured state of the connected device.</t> the intended configured state of the connected device.</li>
</list></t> </ol>
<t>All implementations supporting this RIV specification require the sup
<t>All implementations supporting this RIV specification require the support of port of the following three technologies:</t>
the following three technologies:</t> <ol spacing="normal" type="1"><li>Identity: Device identity in RIV is ba
sed on Device Identity (DevID) defined by IEEE Std 802.1AR <xref target="IEEE-80
<t><list style="numbers"> 2-1AR" format="default"/>,
<t>Identity: Device identity in RIV is based on IEEE 802.1AR Device Identity (
DevID) <xref target="IEEE-802-1AR"/>,
coupled with careful supply-chain management by the manufacturer. The coupled with careful supply-chain management by the manufacturer. The
Initial DevID (IDevID) certificate contains a statement by the manufacturer that establishes Initial DevID (IDevID) certificate contains a statement by the manufacturer that establishes
the identity of the device as it left the factory. Some applications with the identity of the device as it left the factory. Some applications with
a more-complex post-manufacture supply chain (e.g., Value Added Resellers), a more complex post-manufacture supply chain (e.g., value added resellers),
or with different privacy concerns, may want to use alternative mechanisms for p latform or with different privacy concerns, may want to use alternative mechanisms for p latform
authentication (for example, TCG Platform Certificates <xref target="Platform-Ce authentication (for example, TCG Platform Certificates <xref target="PLATFORM-CE
rtificates"/>, or RTS" format="default"/> or
post-manufacture installation of Local Device ID (LDevID)).</t> post-manufacture installation of Local DevID (LDevID)).</li>
<t>Platform Attestation provides evidence of configuration of software element <li>Platform attestation provides evidence of configuration of softwar
s e elements
present in the device. This form of attestation can be implemented present in the device. This form of attestation can be implemented
with TPM Platform Configuration Registers (PCRs), Quote and Log mechanisms, whic h provide cryptographically authenticated evidence with TPM Platform Configuration Registers (PCRs) and Quote and Log mechanisms, which provide cryptographically authenticated evidence
to report what software was started on the device through the boot cycle. Succe ssful attestation requires an to report what software was started on the device through the boot cycle. Succe ssful attestation requires an
unbroken chain from a boot-time root of trust through all layers of software nee ded to bring the device to an unbroken chain from a boot-time Root of Trust through all layers of software nee ded to bring the device to an
operational state, in which each stage computes the hash of components of the ne xt stage, then updates the attestation log and operational state, in which each stage computes the hash of components of the ne xt stage, then updates the attestation log and
the TPM. The TPM can then report the hashes of all the measured hashes as signe d evidence called a the TPM. The TPM can then report the hashes of all the measured hashes as signe d evidence called a
Quote (see <xref target="using-tpm"/> for an overview of TPM operation, or <xref Quote (see <xref target="using-tpm" format="default"/> for an overview of TPM op
target="TPM1.2"/> and <xref target="TPM2.0"/> for many more details).</t> eration or <xref target="TPM-1.2" format="default"/> and <xref target="TPM-2.0"
<t>Signed Reference Values (aka Reference Integrity Measurements) must be conv format="default"/> for many more details).</li>
eyed from the Reference Value Provider (the entity accepted as the software auth <li>Signed Reference Values (aka reference integrity measurements) mus
ority, t be conveyed from the Reference Value Provider (the entity accepted as the soft
often the manufacturer of the network device) to the Verifier.</t> ware authority,
</list></t> often the manufacturer of the network device) to the Verifier.</li>
</ol>
</section> </section>
<section anchor="solution-requirements" title="Solution Requirements"> <section anchor="solution-requirements" numbered="true" toc="default">
<name>Solution Requirements</name>
<t>Remote Integrity Verification must address the “Lying Endpoint” <t>RIV must address the "Lying Endpoint"
problem, in which malicious software on an endpoint may subvert the problem, in which malicious software on an endpoint may subvert the
intended function, and also prevent the endpoint from reporting its compromised intended function and also prevent the endpoint from reporting its compromised
status. (See <xref target="security-cons"/> for further Security Considerations status. (See <xref target="security-cons" format="default"/> for further Securi
.)</t> ty Considerations.)</t>
<t>RIV attestation is designed to be simple
<t>RIV attestation is designed to be simple to deploy at scale. RIV should work "out of the box" as far as possible,
to deploy at scale. RIV should work “out of the box” as far as possible,
that is, with the fewest possible provisioning steps or configuration databases that is, with the fewest possible provisioning steps or configuration databases
needed at the end-user’s site. Network equipment is often required to “self-con figure”, needed at the end user's site. Network equipment is often required to "self-con figure",
to reliably reach out without manual intervention to prove its identity and to reliably reach out without manual intervention to prove its identity and
operating posture, then download its own configuration, a process which preclude operating posture, then download its own configuration, a process which preclude
s pre-installation configuration. See <xref target="RFC8572"/> for an s pre-installation configuration. See <xref target="RFC8572" format="default"/>
example of Secure Zero Touch Provisioning.</t> for an
example of Secure Zero Touch Provisioning (SZTP).</t>
</section> </section>
<section anchor="scope" title="Scope"> <section anchor="scope" numbered="true" toc="default">
<name>Scope</name>
<t>The need for assurance of software integrity, addressed by Remote Attestation <t>The need for assurance of software integrity, addressed by Remote Att
, is a very general problem that could apply to most network-connected computing estation, is a very general problem that could apply to most network-connected c
devices. However, this document includes several assumptions that limit the sc omputing devices. However, this document includes several assumptions that limi
ope to network equipment (e.g., routers, switches and firewalls):</t> t the scope to network equipment (e.g., routers, switches, and firewalls):</t>
<ul spacing="normal">
<t><list style="symbols"> <li>This solution is for use in non-privacy-preserving applications (f
<t>This solution is for use in non-privacy-preserving applications (for exampl or example,
e, networking or industrial Internet of Things (IoT) applications), which avoids th
networking, Industrial IoT), avoiding the need for a Privacy Certificate e need for a Privacy Certification
Authority (also called an Attestation CA) for attestation keys <xref target="AK- Authority (also called an Attestation CA) for Attestation Keys (AKs) <xref targe
Enrollment"/> or TCG Platform t="AIK-ENROLL" format="default"/> or TCG Platform
Certificates <xref target="Platform-Certificates"/>.</t> Certificates <xref target="PLATFORM-CERTS" format="default"/>.</li>
<t>This document assumes network protocols that are common in network equipmen <li>This document assumes network protocols that are common in network
t such as YANG <xref target="RFC7950"/> and NETCONF <xref target="RFC6241"/>, equipment such as YANG <xref target="RFC7950" format="default"/> and Network Co
but not generally used in other applications.</t> nfiguration Protocol (NETCONF) <xref target="RFC6241" format="default"/>,
<t>The approach outlined in this document mandates the use of a TPM <xref targ but not generally used in other applications.</li>
et="TPM1.2"/>, <xref target="TPM2.0"/>, or a compatible cryptoprocessor.</t> <li>The approach outlined in this document mandates the use of a TPM <
</list></t> xref target="TPM-1.2" format="default"/> <xref target="TPM-2.0" format="default"
/> or a compatible cryptoprocessor.</li>
<section anchor="out-of-scope" title="Out of Scope"> </ul>
<section anchor="out-of-scope" numbered="true" toc="default">
<t><list style="symbols"> <name>Out of Scope</name>
<t>Run-Time Attestation: The Linux Integrity Measurement Architecture <xref ta <dl spacing="normal">
rget="IMA"/> attests each process launched <dt>Run-Time Attestation:</dt><dd>The Linux Integrity Measurement Ar
chitecture <xref target="IMA" format="default"/> attests each process launched
after a device is started (and is in scope for RIV in general), but continuous r un-time attestation of Linux or after a device is started (and is in scope for RIV in general), but continuous r un-time attestation of Linux or
other multi-threaded operating system processes after the OS has started conside rably expands the scope of the problem. other multi-threaded operating system processes after the OS has started conside rably expands the scope of the problem.
Many researchers are working on that problem, but this document defers the probl em of continuous, in-memory Many researchers are working on that problem, but this document defers the probl em of continuous, in-memory
run-time attestation.</t> run-time attestation.</dd>
<t>Multi-Vendor Embedded Systems: Additional coordination would be needed for <dt>Multi-Vendor Embedded Systems:</dt><dd> Additional coordination
devices that themselves comprise hardware and software from multiple vendors, would be needed for
devices that themselves comprise hardware and software from multiple vendors and
are
integrated by the end user. Although out of scope for this document, these integrated by the end user. Although out of scope for this document, these
issues are accommodated in <xref target="I-D.ietf-rats-architecture"/>.</t> issues are accommodated in <xref target="RFC9334" format="default"/>.</dd>
<t>Processor Sleep Modes: Network equipment typically does not “sleep”, so <dt>Processor Sleep Modes:</dt><dd>Network equipment typically does
not "sleep", so
sleep and hibernate modes are not considered. Although out of scope sleep and hibernate modes are not considered. Although out of scope
for RIV in this document, Trusted Computing Group specifications do encompass sl for RIV in this document, TCG specifications do encompass sleep and hibernate
eep and hibernate states, which could be incorporated into remote attestation for network equipmen
states, which could be incorporated into remote attestation for network equipmen t in the future, given a compelling need.</dd>
t in the future, given a compelling need.</t> <dt>Virtualization and Containerization:</dt><dd> In a non-virtualiz
<t>Virtualization and Containerization: In a non-virtualized system, the host ed system, the host OS is
OS is responsible for measuring each user-space file or process throughout the operati
responsible for measuring each User Space file or process throughout the operati onal lifetime
onal lifetime
of the system. For virtualized systems, the host OS must verify the hypervisor, of the system. For virtualized systems, the host OS must verify the hypervisor,
but then the hypervisor must manage its own chain of trust through the virtual m achine. Virtualization but then the hypervisor must manage its own chain of trust through the virtual m achine. Virtualization
and containerization technologies are increasingly used in network equipment, bu t and containerization technologies are increasingly used in network equipment, bu t
are not considered in this document.</t> are not considered in this document.</dd>
</list></t> </dl>
</section>
</section> </section>
</section> </section>
</section> <section anchor="solution-overview" numbered="true" toc="default">
<section anchor="solution-overview" title="Solution Overview"> <name>Solution Overview</name>
<section anchor="riv-software-configuration-attestation-using-tpm" numbere
<section anchor="riv-software-configuration-attestation-using-tpm" title="RIV So d="true" toc="default">
ftware Configuration Attestation using TPM"> <name>RIV Software Configuration Attestation Using TPM</name>
<t>RIV Attestation is a process that can be used to determine the identi
<t>RIV Attestation is a process which can be used to determine the identity of s ty of software running
oftware running on a specifically identified device. The Remote Attestation steps of <xref targ
on a specifically-identified device. The Remote Attestation steps of <xref targ et="RIV-desc" format="default"/> are split into two
et="RIV-desc"/> are broken into two phases as shown in <xref target="RIV-Attestation-Model" format="default"/>:</t>
phases, shown in Figure 1:</t> <ul spacing="normal">
<li>During system startup, or Boot Phase, each distinct software objec
<t><list style="symbols"> t is "measured" by the Attester.
<t>During system startup, or boot phase, each distinct software object is “mea The object's identity, hash (i.e., cryptographic digest), and version informatio
sured” by the Attester. n are recorded in a log.
The object’s identity, hash (i.e., cryptographic digest) and version information Hashes are also extended into the TPM (see <xref target="using-tpm" format="defa
are recorded in a log. ult"/> for more on extending hashes) in a way that can be used to validate the l
Hashes are also extended into the TPM (see <xref target="using-tpm"/> for more o og entries. The measurement process generally
n ‘extending hashes’), in a way that can be used to validate the log entries. T
he measurement process generally
follows the layered chain-of-trust model used in Measured Boot, where each stage follows the layered chain-of-trust model used in Measured Boot, where each stage
of the system measures the next one, and extends its measurement into the TPM, of the system measures the next one, and extends its measurement into the TPM,
before launching it. See <xref target="I-D.ietf-rats-architecture"/>, section “ before launching it. See <xref target="RFC9334" sectionFormat="of" section="3.2
Layered Attestation Environments,” for an architectural definition "/>, "Layered Attestation Environments", for an architectural definition
of this model.</t> of this model.</li>
<t>Once the device is running and has operational network connectivity, verifi <li>Once the device is running and has operational network connectivit
cation can take place. A separate y, verification can take place. A separate
Verifier, running in its own trusted environment, will interrogate the network Verifier, running in its own trusted environment, will interrogate the network
device to retrieve the logs and a copy of the digests collected by hashing device to retrieve the logs and a copy of the digests collected by hashing
each software object, signed by an attestation private key secured by, but never released by, each software object, signed by an attestation private key secured by, but never released by,
the TPM. The YANG model described in <xref target="I-D.ietf-rats-yang-tpm-charr the TPM. The YANG model described in <xref target="RFC9684" format="default"/>
a"/> facilitates this operation.</t> facilitates this operation.</li>
</list></t> </ul>
<t>The result is that the Verifier can verify the device's identity by c
<t>The result is that the Verifier can verify the device’s identity by checking hecking
the subject<xref target="RFC5280"/> and signature of the certificate containing the subject <xref target="RFC5280" format="default"/> and signature of the certi
the TPM’s attestation public key, and can ficate containing the TPM's attestation public key.
validate the software that was launched by verifying the correctness of the logs The Verifier can then verify the log's correctness by accumulating all the hashe
by comparing with the s in the log
signed digests from the TPM, and comparing digests in the log with and comparing that to the signed digests from the TPM. From
Reference Values.</t> there, the Verifier can validate the launched software by
comparing the digests in the log with Reference Values.</t>
<t>It should be noted that attestation and identity are inextricably linked; <t>It should be noted that attestation and identity are inextricably lin
ked;
signed Evidence that a particular version of software was loaded is of little signed Evidence that a particular version of software was loaded is of little
value without cryptographic proof of the identity of the Attester producing value without cryptographic proof of the identity of the Attester producing
the Evidence.</t> the Evidence.</t>
<figure anchor="RIV-Attestation-Model">
<figure title="Layered RIV Attestation Model" anchor="RIV-Attestation-Model"><ar <name>Layered RIV Attestation Model</name>
twork align="left"><![CDATA[ <artwork align="left" name="" type="" alt=""><![CDATA[
+-------------------------------------------------------+ +-------------------------------------------------------+
| +---------+ +--------+ +--------+ +---------+ | | +---------+ +--------+ +--------+ +---------+ |
| |UEFI BIOS|--->| Loader |-->| Kernel |--->|Userland | | | |UEFI BIOS|--->| Loader |-->| Kernel |--->|Userland | |
| +---------+ +--------+ +--------+ +---------+ | | +---------+ +--------+ +--------+ +---------+ |
| | | | | | | | | |
| | | | | | | | | |
| +------------+-----------+-+ | | +------------+-----------+-+ |
| Boot Phase | | | Boot Phase | |
| V | | V |
| +--------+ | | +--------+ |
skipping to change at line 361 skipping to change at line 325
| +--------+ | | +--------+ |
| Router | | | Router | |
+--------------------------------|----------------------+ +--------------------------------|----------------------+
| |
| Verification Phase | Verification Phase
| +-----------+ | +-----------+
+--->| Verifier | +--->| Verifier |
+-----------+ +-----------+
Reset---------------flow-of-time-during-boot...---------> Reset---------------flow-of-time-during-boot...--------->
]]></artwork></figure> ]]></artwork>
</figure>
<t>In the Boot phase, measurements are “extended”, or hashed, into the TPM as pr <t>In the Boot Phase, measurements are "extended", or hashed, into the T
ocesses start, PM as processes start,
with the result that the TPM ends up containing hashes of all the measured hashe which result in the TPM containing hashes of all the measured hashes. Later, onc
s. Later, once the system is operational, during the Verification phase, signed e the system is operational, signed
digests are retrieved from the TPM for off-box analysis.</t> digests are retrieved from the TPM during the Verification Phase for off-box ana
lysis.</t>
<section anchor="what-does-riv-attest" title="What Does RIV Attest?"> <section anchor="what-does-riv-attest" numbered="true" toc="default">
<name>What Does RIV Attest?</name>
<t>TPM attestation is focused on Platform Configuration Registers (PCRs), but th <t>TPM attestation is focused on PCRs, but those registers are only ve
ose registers are only vehicles for certifying hicles for certifying
accompanying Evidence, conveyed in log entries. It is the hashes in log entries accompanying Evidence conveyed in log entries. It is the hashes in log entries
that are extended into PCRs, where the final PCR values that are extended into PCRs, where the final PCR values
can be retrieved in the form of a structure called a Quote, signed by an Attesta can be retrieved in the form of a structure called a Quote, which is signed by a
tion key known only to the TPM. The use of multiple PCRs serves only to n AK known only to the TPM. The use of multiple PCRs serves only to
provide some independence between different classes of object, so that one class provide some independence between different classes of object so that one class
of objects can be updated without changing the of objects can be updated without changing the
extended hash for other classes. Although PCRs can be used for any purpose, thi s section outlines the objects within the extended hash for other classes. Although PCRs can be used for any purpose, thi s section outlines the objects within the
scope of this document which may be extended into the TPM.</t> scope of this document that may be extended into the TPM.</t>
<t>In general, assignment of measurements to PCRs is a policy choice m
<t>In general, assignment of measurements to PCRs is a policy choice made by the ade by the device manufacturer, selected to independently attest three classes o
device manufacturer, selected to independently attest three classes of object:< f object:</t>
/t> <dl>
<dt>Code:</dt>
<t><list style="symbols"> <dd>Instructions to be executed by a CPU.</dd>
<t>Code, (i.e., instructions) to be executed by a CPU.</t> <dt>Configuration:</dt>
<t>Configuration - Many devices offer numerous options controlled by non-volat <dd>Many devices offer numerous options controlled by non-volatile c
ile configuration variables which can impact the device’s security posture. The onfiguration variables that can impact the device's security posture. These set
se settings may have vendor defaults, but often can be changed by administrators tings may have vendor defaults, but often can be changed by administrators, who
, who may want to verify via attestation that the operational state of the setti may want to verify via attestation that the operational state of the settings ma
ngs match their intended state.</t> tch their intended state.</dd>
<t>Credentials - Administrators may wish to verify via attestation that public <dt>Credentials:</dt>
keys and credentials outside the Root of Trust have not been subject to unautho <dd>Administrators may wish to verify via attestation that public ke
rized tampering. (By definition, keys protecting the root of trust can’t be ver ys and credentials outside the Root of Trust have not been subject to unauthoriz
ified independently.)</t> ed tampering. (By definition, keys protecting the Root of Trust can't be verifi
</list></t> ed independently.)</dd>
</dl>
<t>The TCG PC Client Platform Firmware Profile Specification <xref target="PC-Cl <t>The "TCG PC Client Specific Platform Firmware Profile Specification
ient-BIOS-TPM-2.0"/> gives considerable detail on what is to be " <xref target="PC-CLIENT-BIOS-TPM-2.0" format="default"/> details what is to be
measured during the boot phase of platform startup using a UEFI BIOS (www.uefi.o measured during the Boot Phase of platform startup using a Unified Extensible Fi
rg), but the goal is simply to measure every bit of rmware Interface (UEFI) BIOS (<eref target="www.uefi.org" brackets="angle"/>), b
ut the goal is simply to measure every bit of
code executed in the process of starting the device, along with any configuratio n information related to security posture, leaving code executed in the process of starting the device, along with any configuratio n information related to security posture, leaving
no gap for unmeasured code to remain undetected, potentially subverting the chai no gap for unmeasured code to remain undetected and potentially subverting the c
n.</t> hain.</t>
<t>For devices using a UEFI BIOS, <xref target="PC-CLIENT-BIOS-TPM-2.0
<t>For devices using a UEFI BIOS, <xref target="PC-Client-BIOS-TPM-2.0"/> and <x " format="default"/> and <xref target="PC-CLIENT-EFI-TPM-1.2" format="default"/>
ref target="PC-Client-EFI-TPM-1.2"/> give detailed normative requirements for PC give detailed normative requirements for PCR usage. For other
R usage. For other platform architectures, where TCG normative requirements currently do not exist,
platform architectures, where TCG normative requirements currently do not exist, <xref target="Attested-Objects" format="default"/> gives non-normative guidance
the table in <xref target="Attested-Objects"/> gives non-normative guidance for for PCR assignment that generalizes the specific
PCR assignment that generalizes the specific details of <xref target="PC-CLIENT-BIOS-TPM-2.0" format="default"/>.</t>
details of <xref target="PC-Client-BIOS-TPM-2.0"/>.</t> <t>By convention, most PCRs are assigned in pairs, with the even-numbe
red PCR used to measure executable code and
<t>By convention, most PCRs are assigned in pairs, which the even-numbered PCR u
sed to measure executable code, and
the odd-numbered PCR used to measure whatever data and configuration are associa ted with that code. It is important the odd-numbered PCR used to measure whatever data and configuration are associa ted with that code. It is important
to note that each PCR may contain results from dozens (or even thousands) of ind ividual measurements.</t> to note that each PCR may contain results from dozens (or even thousands) of ind ividual measurements.</t>
<table anchor="Attested-Objects">
<name>Attested Objects</name>
<thead>
<tr>
<th></th>
<th rowspan="" colspan="2"> Assigned PCR #</th>
</tr>
<tr>
<th>Function</th>
<th>Code</th>
<th>Configuration</th>
</tr>
</thead>
<tbody>
<tr>
<td>Firmware Static Root of Trust (i.e., initial boot firmware
and drivers)</td>
<td>0</td>
<td>1</td>
</tr>
<tr>
<td>Drivers and initialization for optional or add-in devices</
td>
<td>2</td>
<td>3</td>
</tr>
<tr>
<td>OS loader code and configuration (i.e., the code launched b
y firmware) to load an operating system kernel. These PCRs record each boot att
empt, and an identifier for where the loader was found</td>
<td>4</td>
<td>5</td>
</tr>
<tr>
<td>Vendor-specific measurements during boot</td>
<td>6</td>
<td>6</td>
</tr>
<tr>
<td>Secure Boot Policy. This PCR records keys and configuratio
n used to validate the OS loader</td>
<td></td>
<td>7</td>
</tr>
<tr>
<td> Measurements made by the OS loader (e.g., GRUB2 for Linux)
</td>
<td>8</td>
<td>9</td>
</tr>
<tr>
<td>Measurements made by OS (e.g., Linux IMA)</td>
<td>10</td>
<td>10</td>
</tr>
</tbody>
</table>
<figure title="Attested Objects" anchor="Attested-Objects"><artwork align="left" </section>
><![CDATA[ <section anchor="notes-on-pcr-allocations" numbered="true" toc="default"
+------------------------------------------------------------------+ >
| | Assigned PCR # | <name>Notes on PCR Allocations</name>
| Function | Code | Configuration| <t>It is important to recognize that PCR[0] is critical. The first me
| Firmware Static Root of Trust, (i.e., | 0 | 1 | asurement into PCR[0] is taken by the Root of Trust for
| initial boot firmware and drivers) | | | Measurement, which is code that, by definition, cannot be verified by measuremen
| Drivers and initialization for optional | 2 | 3 | t. This measurement
| or add-in devices | | |
| OS Loader code and configuration, (i.e., | 4 | 5 |
| the code launched by firmware) to load an | | |
| operating system kernel. These PCRs record | | |
| each boot attempt, and an identifier for | | |
| where the loader was found | | |
| Vendor Specific Measurements during boot | 6 | 6 |
| Secure Boot Policy. This PCR records keys | | 7 |
| and configuration used to validate the OS | | |
| loader | | |
| Measurements made by the OS Loader | 8 | 9 |
| (e.g. GRUB2 for Linux) | | |
| Measurements made by OS (e.g., Linux IMA) | 10 | 10 |
+------------------------------------------------------------------+
]]></artwork></figure>
</section>
<section anchor="notes-on-pcr-allocations" title="Notes on PCR Allocations">
<t>It is important to recognize that PCR[0] is critical. The first measurement
into PCR[0] is taken by the Root of Trust for
Measurement, code which, by definition, cannot be verified by measurement. This
measurement
establishes the chain of trust for all subsequent measurements. If the PCR[0] m easurement cannot be trusted, the establishes the chain of trust for all subsequent measurements. If the PCR[0] m easurement cannot be trusted, the
validity of the entire chain is put into question.</t> validity of the entire chain is called into question.</t>
<t>Distinctions between PCR[0], PCR[2], PCR[4], and PCR[8] are summari
<t>Distinctions Between PCR[0], PCR[2], PCR[4] and PCR[8] are summarized below:< zed below:</t>
/t> <dl spacing="normal">
<dt>PCR[0]</dt><dd>typically represents a consistent view of rarely
<t><list style="symbols"> changed boot components of the host platform, which allows Attestation policies
<t>PCR[0] typically represents a consistent view of rarely-changed Host Platfo to be defined using the less changeable components of the transitive trust chain
rm boot components, allowing Attestation policies to be defined using the less c . This PCR
hangeable components of the transitive trust chain. This PCR typically provides a consistent view of the platform regardless of user-selected
typically provides a consistent view of the platform regardless of user selected options.</dd>
options.</t> <dt>PCR[2]</dt><dd>is intended to represent a "user-configurable" en
<t>PCR[2] is intended to represent a “user configurable” environment where the vironment where the user has the ability to alter the
user has the ability to alter the
components that are measured into PCR[2]. This is typically done by adding adapt er cards, etc., into user-accessible components that are measured into PCR[2]. This is typically done by adding adapt er cards, etc., into user-accessible
PCI or other slots. In UEFI systems these devices may be configured by Option R Peripheral Component Interconnect (PCI) or other slots. In UEFI systems, these
OMs measured into PCR[2] and devices may be configured by Option ROMs measured into PCR[2] and
executed by the UEFI BIOS.</t> executed by the UEFI BIOS.</dd>
<t>PCR[4] is intended to represent the software that manages the transition be <dt>PCR[4]</dt><dd>is intended to represent the software that manage
tween the platform’s Pre-Operating System s the transition between the platform's pre-OS
start and the state of a system with the Operating System present. This PCR, al start and the state of a system with the OS present. This PCR, along with PCR[5
ong with PCR[5], identifies the initial ], identifies the initial
operating system loader (e.g., GRUB for Linux).</t> OS loader (e.g., GRUB for Linux).</dd>
<t>PCR[8] is used by the OS loader (e.g. GRUB) to record measurements of the v <dt>PCR[8]</dt><dd>is used by the OS loader (e.g., GRUB) to record m
arious components of the operating system.</t> easurements of the various components of the operating system.</dd>
</list></t> </dl>
<t>Although <xref target="PC-CLIENT-BIOS-TPM-2.0" format="default"/> s
<t>Although the TCG PC Client document specifies the use of the first eight PCRs pecifies the use of the first eight PCRs very carefully to ensure interoperabili
very carefully to ensure interoperability ty
among multiple among multiple
UEFI BIOS vendors, it should be noted that embedded software vendors may have co nsiderably more flexibility. Verifiers UEFI BIOS vendors, it should be noted that embedded software vendors may have co nsiderably more flexibility. Verifiers
typically need to know which log entries are consequential and which are not (po ssibly controlled by local policies) but typically need to know which log entries are consequential and which are not (po ssibly controlled by local policies), but
the Verifier may not need to know what each log entry means or why it was assign ed to a particular PCR. Designers must the Verifier may not need to know what each log entry means or why it was assign ed to a particular PCR. Designers must
recognize that some PCRs may cover log entries that a particular Verifier consid ers critical and other log entries that recognize that some PCRs may cover log entries that a particular Verifier consid ers critical and other log entries that
are not considered important, so differing PCR values may not on their own const are not considered important, so differing PCR values may not on their own const
itute a check for authenticity. For example, in a UEFI system, some administrat itute a check for authenticity. For example, in a UEFI system, some administrat
ors may consider booting an image from a removable drive, something recorded in ors may consider booting an image from a removable drive, something recorded in
a PCR, to be a security violation, while others might consider that operation an a PCR, to be a security violation, while others might consider that operation to
authorized recovery procedure.</t> be an authorized recovery procedure.</t>
<t>Designers may allocate particular events to specific PCRs in order
<t>Designers may allocate particular events to specific PCRs in order to achieve to achieve a particular objective with local
a particular objective with local attestation (e.g., allowing a procedure to execute, or releasing a particular de
attestation, (e.g., allowing a procedure to execute, or releasing a particular d cryption key, only if a given PCR is in a given state). It may also be importan
ecryption key, only if a given PCR is in a given state). It may also be importa t
nt to designers to consider whether streaming notification of PCR updates is requir
to designers to consider whether streaming notification of PCR updates is requir ed (see <xref target="I-D.ietf-rats-network-device-subscription" format="default
ed (see <xref target="I-D.birkholz-rats-network-device-subscription"/>). Specif "/>). Specific
ic
log entries can only be validated if the Verifier receives every log entry affec ting the relevant PCR, so (for example) log entries can only be validated if the Verifier receives every log entry affec ting the relevant PCR, so (for example)
a designer might want to separate rare, high-value events such as configuration a designer might want to separate rare, high-value events, such as configuration
changes, from high-volume, routine changes, from high-volume, routine
measurements such as IMA <xref target="IMA"/> logs.</t> measurements such as IMA logs <xref target="IMA" format="default"/>.</t>
</section>
</section> </section>
</section> <section anchor="riv-keying" numbered="true" toc="default">
<section anchor="riv-keying" title="RIV Keying"> <name>RIV Keying</name>
<t>RIV attestation relies on two credentials:</t>
<t>RIV attestation relies on two credentials:</t> <ul spacing="normal">
<li>An identity key pair and matching certificate is required to certi
<t><list style="symbols"> fy the identity of the Attester itself.
<t>An identity key pair and matching certificate is required to certify the id RIV specifies the use of an IEEE 802.1AR DevID <xref target="IEEE-802-1AR" forma
entity of the Attester itself. t="default"/> that is
RIV specifies the use of an IEEE 802.1AR Device Identity (DevID) <xref target="I signed by the device manufacturer and contains the device serial number. This r
EEE-802-1AR"/>, equirement goes slightly
signed by the device manufacturer, containing the device serial number. This re beyond 802.1AR; see <xref target="riv-simplify" format="default"/> for notes.</l
quirement goes slightly i>
beyond 802.1AR; see <xref target="riv-simplify"/> for notes.</t> <li>An Attestation key pair and matching certificate is required to si
<t>An Attestation key pair and matching certificate is required to sign the Qu gn the Quote generated by the TPM to report evidence
ote generated by the TPM to report evidence of software configuration.</li>
of software configuration.</t> </ul>
</list></t> <t>In a TPM application, both the Attestation private key and the DevID
private key <bcp14>MUST</bcp14> be protected by the TPM.
<t>In a TPM application, both the Attestation private key and the DevID private
key MUST be protected by the TPM.
Depending on other TPM configuration procedures, Depending on other TPM configuration procedures,
the two keys are likely to be different; some of the considerations are outlined the two keys are likely to be different; some of the considerations are outlined
in TCG in the
“TPM 2.0 Keys for Device Identity and Attestation” <xref target="Platform-DevID- "TPM 2.0 Keys for Device Identity and Attestation" document <xref target="PLATFO
TPM-2.0"/>.</t> RM-DEVID-TPM-2.0" format="default"/>.</t>
<t>The "TPM 2.0 Keys for Device Identity and Attestation" document <xref
<t>The TCG TPM 2.0 Keys document <xref target="Platform-DevID-TPM-2.0"/> specifi target="PLATFORM-DEVID-TPM-2.0" format="default"/> specifies further convention
es further conventions for these keys:</t> s for these keys:</t>
<ul spacing="normal">
<t><list style="symbols"> <li>When separate Identity and Attestation keys are used, the
<t>When separate Identity and Attestation keys are used, the Attestation AK and its X.509 certificate should parallel the DevID, with the same unique
Key (AK) and its X.509 certificate should parallel the DevID, with the same uniq device identification as the DevID certificate (that is, the same subject and su
ue bjectAltName (if present), even though the key pairs are different). By examini
device identification as the DevID certificate (that is, the same subject and su ng the corresponding AK certificate, the Verifier
bjectAltName (if present), even though the key pairs are different). This allow can directly link a device's quote, which was signed by an
s AK, to the device that provided it. If the
a quote from the device, signed by an AK, to be linked directly to the subject in the AK certificate doesn't match the corresponding DevID certificate,
device that provided it, by examining the corresponding AK certificate. If the or
subject in the AK certificate doesn’t match the corresponding DevID certificate, if they're signed by different authorities, the Verifier may signal the detecti
or on of an Asokan-style person-in-the-middle attack (see <xref target="pitm" forma
they’re signed by differing authorities the Verifier may signal the detection o t="default"/>).</li>
f an Asokan-style person-in-the-middle attack (see <xref target="pitm"/>).</t> <li>Network devices that are expected to use SZTP as
<t>Network devices that are expected to use secure zero touch provisioning as specified in <xref target="RFC8572" format="default"/>
specified in <xref target="RFC8572"/> <bcp14>MUST</bcp14> be shipped by the manufacturer with pre-provisioned keys (In
MUST be shipped by the manufacturer with pre-provisioned keys (Initial DevID and itial DevID and Initial AK,
Initial AK, called IDevID and IAK, respectively). IDevID and IAK certificates <bcp14>MUST</
called IDevID and IAK). IDevID and IAK certificates MUST both be signed by the bcp14> both be signed by the Endorser
Endorser
(typically the device manufacturer). Inclusion of an IDevID and IAK by a vendor does not (typically the device manufacturer). Inclusion of an IDevID and IAK by a vendor does not
preclude a mechanism whereby an administrator can define Local Identity and preclude a mechanism whereby an administrator can define LDevID and
Attestation Keys (LDevID and LAK) if desired.</t> Local Attestation Keys (LAK) if desired.</li>
</list></t> </ul>
</section>
</section> <section anchor="RIV-flow" numbered="true" toc="default">
<section anchor="RIV-flow" title="RIV Information Flow"> <name>RIV Information Flow</name>
<t>RIV workflow for network equipment is organized around a simple use c
<t>RIV workflow for network equipment is organized around a simple use case ase
where a network operator wishes to verify the integrity of software installed where a network operator wishes to verify the integrity of software installed
in specific, fielded devices. A normative taxonomy of terms is given in <xref t arget="I-D.ietf-rats-architecture"/>, in specific, fielded devices. A normative taxonomy of terms is given in <xref t arget="RFC9334" format="default"/>,
but as a reminder, this use case implies several roles and objects:</t> but as a reminder, this use case implies several roles and objects:</t>
<dl spacing="normal">
<t><list style="numbers"> <dt>Attester:</dt>
<t>The Attester, the device which the network operator wants to examine.</t> <dd>The device that the network operator wants to examine.</dd>
<t>A Verifier (which might be a network management station) somewhere separate <dt>Verifier:</dt>
<dd>Which might be a Network Management Station and is somewhat separa
te
from the Device that will retrieve the signed evidence and measurement logs, a nd analyze them to pass from the Device that will retrieve the signed evidence and measurement logs, a nd analyze them to pass
judgment on the security posture of the device.</t> judgment on the security posture of the device.</dd>
<t>A Relying Party, which can act on Attestation Results. Interaction between <dt>Relying Party:</dt>
the Relying Party and the <dd>Can act on Attestation Results. Interaction between the Relying P
Verifier is considered out of scope for RIV.</t> arty and the
<t>Signed Reference Integrity Manifests (RIMs), containing Reference Values, c Verifier is considered out of scope for RIV.</dd>
an <dt>Signed Reference Integrity Manifests (RIMs):</dt>
<dd>Contains Reference Values. RIMs can
either be created by the device manufacturer either be created by the device manufacturer
and shipped along with the device as part of its software image, or alternativ ely, and shipped along with the device as part of its software image, or alternativ ely,
could be obtained several other ways (direct to the Verifier from the could be obtained several other ways (direct to the Verifier from the
manufacturer, from a third party, from the owner’s observation of what’s manufacturer, from a third party, from the owner's concept
thought to be a “known good system”, etc.). Retrieving RIMs from the device of a "known good system", etc.). Retrieving RIMs from the device
itself allows attestation to be done in systems that may not have access itself allows attestation to be done in systems that may not have access
to the public internet, or by other devices that are not management stations to the public Internet, or by other devices that are not management stations
per se (e.g., a peer device; see <xref target="RIM-policy"/>). If Reference V per se (e.g., a peer device; see <xref target="RIM-policy" format="default"/>)
alues are obtained from . If Reference Values are obtained from
multiple sources, the Verifier may need to evaluate the relative level of multiple sources, the Verifier may need to evaluate the relative level of
trust to be placed in each source in case of a discrepancy.</t> trust to be placed in each source in case of a discrepancy.</dd>
</list></t> </dl>
<t>These components are illustrated in <xref target="RIV-Reference-Confi
<t>These components are illustrated in <xref target="RIV-Reference-Configuration guration" format="default"/>.</t>
"/>.</t> <figure anchor="RIV-Reference-Configuration">
<name>RIV Reference Configuration for Network Equipment</name>
<figure title="RIV Reference Configuration for Network Equipment" anchor="RIV-Re <artwork align="left" name="" type="" alt=""><![CDATA[
ference-Configuration"><artwork align="left"><![CDATA[
+----------------+ +-------------+ +---------+--------+ +----------------+ +-------------+ +---------+--------+
|Reference Value | | Attester | Step 1 | Verifier| | |Reference Value | | Attester | Step 1 | Verifier| |
|Provider | | (Device |<-------| (Network| Relying| |Provider | | (Device |<-------| (Network| Relying|
|(Device | | under |------->| Mngmt | Party | |(Device | | under |------->| Mgmt | Party |
|Manufacturer | | attestation)| Step 2 | Station)| | |Manufacturer | | attestation)| Step 2 | Station)| |
|or other | | | | | | |or other | | | | | |
|authority) | | | | | | |authority) | | | | | |
+----------------+ +-------------+ +---------+--------+ +----------------+ +-------------+ +---------+--------+
| /\ | /\
| Step 0 | | Step 0 |
----------------------------------------------- -----------------------------------------------
]]></artwork>
]]></artwork></figure> </figure>
<ol spacing="normal" type="Step %d:" start="0" indent="9">
<t><list style="symbols"> <li>The Reference Value Provider (the device manufacturer or other aut
<t>In Step 0, The Reference Value Provider (the device manufacturer or other a hority) makes
uthority) makes one or more RIMs, which correspond to the software image expected to be found on
one or more Reference Integrity Manifests (RIMs), corresponding to the software the device and are signed by the Reference Value Provider, available to the Ver
image expected to be found on the device, signed by the Reference Value Provider ifier.
, available to the Verifier (See <xref target="RIM-policy" format="default"/> for "in-band" and "out of band
(see <xref target="RIM-policy"/> for “in-band” and “out of band” ways to make th " ways to make this happen.)</li>
is happen).</t> <li>On behalf of a Relying Party, the Verifier (Network Management Sta
<t>In Step 1, tion) requests DevID,
the Verifier (Network Management Station), on behalf of a Relying Party, request Measurement Values, and possibly RIMs from the Attester.</li>
s Identity, <li>The
Measurement Values, and possibly RIMs, from the Attester.</t> Attester responds to the request by providing a DevID, quotes (measured values t
<t>In Step 2, the hat are signed by the Attester),
Attester responds to the request by providing a DevID, quotes (measured values, and optionally RIMs.</li>
signed by the Attester), </ol>
and optionally RIMs.</t> <t>The use of the following standards components allows for interoperabi
</list></t> lity:</t>
<ol spacing="normal" type="1"><li>TPM keys <bcp14>MUST</bcp14> be config
<t>Use of the following standards components allows for interoperability:</t> ured according to <xref target="PLATFORM-DEVID-TPM-2.0" format="default"/> or <x
ref target="PLATFORM-ID-TPM-1.2" format="default"/>.</li>
<t><list style="numbers"> <li>For devices using UEFI and Linux, measurements of firmware and boo
<t>TPM Keys MUST be configured according to <xref target="Platform-DevID-TPM-2 table modules <bcp14>MUST</bcp14> be taken according to "TCG EFI Platform Specif
.0"/>, or <xref target="Platform-ID-TPM-1.2"/>.</t> ication" <xref target="PC-CLIENT-EFI-TPM-1.2" format="default"/> or "TCG PC Clie
<t>For devices using UEFI and Linux, measurements of firmware and bootable mod nt Specific Platform Firmware Profile Specification" <xref target="PC-CLIENT-BIO
ules MUST be taken according to TCG PC Client <xref target="PC-Client-EFI-TPM-1. S-TPM-2.0" format="default"/>, and Linux IMA <xref target="IMA" format="default"
2"/> or <xref target="PC-Client-BIOS-TPM-2.0"/>, and Linux IMA <xref target="IMA />.</li>
"/>.</t> <li>DevID <bcp14>MUST</bcp14> be managed as DevID certificates as spec
<t>Device Identity MUST be managed as specified in IEEE 802.1AR Device Identit ified in IEEE Std 802.1AR <xref target="IEEE-802-1AR" format="default"/>, with k
y certificates <xref target="IEEE-802-1AR"/>, with keys protected by TPMs.</t> eys protected by TPMs.</li>
<t>Attestation logs from Linux-based systems MUST be formatted according to th <li>Attestation logs from Linux-based systems <bcp14>MUST</bcp14> be f
e Canonical Event Log format <xref target="Canonical-Event-Log"/>. UEFI-based s ormatted according to the "Canonical Event Log Format" <xref target="CEL" format
ystems MUST use the TCG UEFI BIOS event log <xref target="PC-Client-EFI-TPM-1.2" ="default"/>. UEFI-based systems <bcp14>MUST</bcp14> use the TCG UEFI BIOS even
/> for TPM1.2 systems, and TCG PC Client Platform Firmware Profile <xref target= t log <xref target="PC-CLIENT-EFI-TPM-1.2" format="default"/> for TPM 1.2 system
"PC-Client-BIOS-TPM-2.0"/> for TPM2.0.</t> s and the "TCG PC Client Specific Platform Firmware Profile" <xref target="PC-CL
<t>Quotes MUST be retrieved from the TPM according to TCG TAP Information Mode IENT-BIOS-TPM-2.0" format="default"/> for TPM 2.0 systems.</li>
l <xref target="TAP"/> and the CHARRA YANG model <xref target="I-D.ietf-rats-yan <li>Quotes <bcp14>MUST</bcp14> be retrieved from the TPM according to
g-tpm-charra"/>. While the TAP IM gives a protocol-independent description of t the TCG Trusted Attestation Protocol Information Model (TAP IM) <xref target="TA
he data elements involved, it’s important to note that quotes from the TPM are s P" format="default"/> and the Challenge-Response-based Remote Attestation (CHARR
igned inside the TPM, and MUST be retrieved in a way that does not invalidate th A) YANG model <xref target="RFC9684" format="default"/>. While the TAP IM gives
e signature, to preserve the trust model. The <xref target="I-D.ietf-rats-yang- a protocol-independent description of the data elements involved, it's importan
tpm-charra"/> is used for this purpose. (See <xref target="security-cons"/> Sec t to note that quotes from the TPM are signed inside the TPM and <bcp14>MUST</bc
urity Considerations).</t> p14> be retrieved in a way that does not invalidate the signature, to preserve t
<t>Reference Values MUST be encoded as defined in he trust model. The CHARRA YANG model <xref target="RFC9684" format="default"/>
the TCG RIM document <xref target="RIM"/>, typically using SWID <xref target=" is used for this purpose. (See <xref target="security-cons" format="default"/>
SWID"/>, <xref target="NIST-IR-8060"/> or CoSWID tags <xref target="I-D.ietf-sac , Security Considerations).</li>
m-coswid"/>.</t> <li>Reference Values <bcp14>MUST</bcp14> be encoded as defined in
</list></t> the TCG RIM document <xref target="RIM" format="default"/>, typically using So
ftware Identification (SWID) tags <xref target="SWID" format="default"/> <xref t
</section> arget="NIST-IR-8060" format="default"/> or Concise SWID (CoSWID) tags <xref targ
<section anchor="riv-simplify" title="RIV Simplifying Assumptions"> et="RFC9393" format="default"/>.</li>
</ol>
<t>This document makes the following simplifying assumptions to reduce complexit </section>
y:</t> <section anchor="riv-simplify" numbered="true" toc="default">
<name>RIV Simplifying Assumptions</name>
<t><list style="symbols"> <t>This document makes the following simplifying assumptions to reduce c
<t>The product to be attested MUST be shipped by the equipment vendor with bot omplexity:</t>
h an IEEE 802.1AR Device Identity and an Initial <ul spacing="normal">
Attestation Key (IAK), with certificates in place. The IAK certificate must con <li>The product to be attested <bcp14>MUST</bcp14> be shipped by the e
tain the same identity quipment vendor with both a DevID as specified by IEEE Std 802.1AR and an IAK, w
ith certificates in place. The IAK certificate must contain the same identity
information as the DevID (specifically, the same subject and subjectAltName (if used), signed by the manufacturer). The IAK is a type of key that can be information as the DevID (specifically, the same subject and subjectAltName (if used), signed by the manufacturer). The IAK is a type of key that can be
used to sign a TPM Quote, but not other objects (i.e., it’s marked as a TCG “Res tricted” key; used to sign a TPM Quote, but not other objects (i.e., it's marked as a TCG "Res tricted" key;
this convention is described in this convention is described in
“TPM 2.0 Keys for Device Identity and Attestation” <xref target="Platform-DevID- TPM-2.0"/>). For network equipment, which is generally non-privacy-sensitive, sh ipping "TPM 2.0 Keys for Device Identity and Attestation" <xref target="PLATFORM-DEVID- TPM-2.0" format="default"/>). For network equipment, which is generally not priv acy sensitive, shipping
a device with both an IDevID and an IAK already provisioned substantially a device with both an IDevID and an IAK already provisioned substantially
simplifies initial startup.</t> simplifies initial startup.</li>
<t>IEEE 802.1AR does not require a product serial number as part of the subjec <li>
t, but RIV-compliant <t>IEEE Std 802.1AR does not require a product serial number as part
devices MUST include their serial numbers in the DevID/IAK certificates to simpl of the subject, but RIV-compliant
ify tracking logistics devices <bcp14>MUST</bcp14> include their serial numbers in the DevID/IAK certif
icates to simplify tracking logistics
for network equipment users. All other optional for network equipment users. All other optional
802.1AR fields remain optional in RIV.<vspace /> 802.1AR fields remain optional in RIV.</t>
It should be noted that 802.1AR use of X.509 certificate fields <t>
is not identical to those descsribed in <xref target="RFC6125"/> for representat It should be noted that the use of X.509 certificate fields as specified by IEEE
ion of application service identity.</t> Std 802.1AR
<t>The product MUST be equipped with a Root of Trust for Measurement (RTM), Ro is not identical to that described in <xref target="RFC9525" format="default"/>
ot of Trust for representation of application service identity.</t>
for Storage and Root of Trust for Reporting (as defined in <xref target="SP800-1 </li>
55"/>) which together are <li>The product <bcp14>MUST</bcp14> be equipped with an RTM, a Root of
capable of conforming to TCG Trusted Attestation Protocol Information Model <xre Trust
f target="TAP"/>.</t> for Storage, and a Root of Trust for Reporting (as defined in <xref target="SP80
<t>The authorized software supplier MUST make available Reference Values 0-155" format="default"/>), which together are
in the form of signed SWID or CoSWID tags.</t> capable of conforming to the TCG TAP IM <xref target="TAP" format="default"/>.</
</list></t> li>
<li>The authorized software supplier <bcp14>MUST</bcp14> make availabl
<section anchor="RIM-section" title="Reference Integrity Manifests (RIMs)"> e Reference Values
in the form of signed SWID or CoSWID tags.</li>
<t><xref target="I-D.ietf-rats-yang-tpm-charra"/> focuses on collecting and tran </ul>
smitting evidence in <section anchor="RIM-section" numbered="true" toc="default">
<name>Reference Integrity Manifests (RIMs)</name>
<t><xref target="RFC9684" format="default"/> focuses on collecting and
transmitting evidence in
the form of PCR measurements and attestation logs. But the critical part the form of PCR measurements and attestation logs. But the critical part
of the process is enabling the Verifier to decide whether the measurements of the process is enabling the Verifier to decide whether the measurements
are “the right ones” or not.</t> are "the right ones" or not.</t>
<t>While it must be up to network administrators to decide what they w
<t>While it must be up to network administrators to decide what they want on ant on
their networks, the software supplier should supply the Reference Values, in their networks, the software supplier should supply the Reference Values, in
signed Reference Integrity Manifests, that signed RIMs, that
may be used by a Verifier to determine if evidence shows known good, known may be used by a Verifier to determine if evidence shows known good, known
bad or unknown software configurations.</t> bad, or unknown software configurations.</t>
<t>In general, there are two kinds of reference measurements:</t>
<t>In general, there are two kinds of reference measurements:</t> <ol spacing="normal" type="1"><li>Measurements of early system startup
(e.g., BIOS, boot loader, OS kernel)
<t><list style="numbers"> are essentially single threaded and executed exactly once, in a known sequence,
<t>Measurements of early system startup (e.g., BIOS, boot loader, OS kernel) before any results can be reported. In this case, while the method for
are essentially single-threaded, and executed exactly once, in a known sequence,
before any results could be reported. In this case, while the method for
computing the hash and extending relevant PCRs may be complicated, the net computing the hash and extending relevant PCRs may be complicated, the net
result is that the software (more likely, firmware) vendor will have one result is that the software (more likely, firmware) vendor will have one
known good PCR value that “should” be present in the relevant PCRs after the box has known good PCR value that "should" be present in the relevant PCRs after the box has
booted. In this case, the signed reference measurement could simply list the booted. In this case, the signed reference measurement could simply list the
expected hashes for the given version. However, a RIM that contains the expected hashes for the given version. However, a RIM that contains the
intermediate hashes can be useful in debugging cases where the expected final ha sh intermediate hashes can be useful in debugging cases where the expected final ha sh
is not the one reported.</t> is not the one reported.</li>
<t>Measurements taken later in operation of the system, once an OS has started <li>Measurements taken later in operation of the system, once an OS
(for example, Linux IMA <xref target="IMA"/>), may be more complex, with unpredi has started
ctable “final” (for example, Linux IMA <xref target="IMA" format="default"/>), may be more comp
lex, with unpredictable "final"
PCR values. In this case, the Verifier must have enough information to reconstr uct PCR values. In this case, the Verifier must have enough information to reconstr uct
the expected PCR values from logs and signed reference measurements from the expected PCR values from logs and signed reference measurements from
a trusted authority.</t> a trusted authority.</li>
</list></t> </ol>
<t>In both cases, the expected values can be expressed as signed SWID
<t>In both cases, the expected values can be expressed as signed SWID or CoSWID or CoSWID tags,
tags,
but the SWID structure in the second case is somewhat more complex, as reconstru ction of the extended hash in a PCR may involve thousands of files and other obj ects.</t> but the SWID structure in the second case is somewhat more complex, as reconstru ction of the extended hash in a PCR may involve thousands of files and other obj ects.</t>
<t>TCG has published an information model defining elements of RIMs
<t>TCG has published an information model defining elements of Reference Integri under the title "TCG Reference Integrity Manifest (RIM) Information Model" <xref
ty target="RIM" format="default"/>. This information model outlines how SWID tags
Manifests under the title TCG Reference Integrity Manifest Information Model <xr should be structured to allow attestation, and it defines "bundles" of SWID tag
ef target="RIM"/>. This information model outlines how SWID tags should be stru s that may be needed to describe a complete software release. The RIM contains
ctured to allow attestation, and defines “bundles” of SWID tags that may be need metadata relating to the software release it belongs to, plus hashes for each in
ed to describe a complete software release. The RIM contains metadata relating dividual file or other object that could be attested.</t>
to the software release it belongs to, plus hashes for each individual file or o <t>Many network equipment vendors use a UEFI BIOS to launch their netw
ther object that could be attested.</t> ork operating system. These vendors may want to
also use the "TCG PC Client Reference Integrity Manifest Specification" <xref ta
<t>Many network equipment vendors use a UEFI BIOS to launch their network operat rget="PC-CLIENT-RIM" format="default"/>, which focuses specifically on a SWID-co
ing system. These vendors may want to mpatible format suitable for expressing measurement values expected from a UEFI
also use the TCG PC Client Reference Integrity Measurement specification <xref t BIOS.</t>
arget="PC-Client-RIM"/>, which focuses specifically on a SWID-compatible format </section>
suitable for expressing measurement values expected from a UEFI BIOS.</t> <section anchor="attestation-logs" numbered="true" toc="default">
<name>Attestation Logs</name>
</section> <t>Quotes from a TPM can provide evidence of the state of a device up
<section anchor="attestation-logs" title="Attestation Logs"> to the time
the evidence was recorded. However, to make sense of the quote in cases where se
<t>Quotes from a TPM can provide evidence of the state of a device up to the tim veral events are extended into one PCR, an
e
the evidence was recorded, but to make sense of the quote in cases where several
events are extended into one PCR an
event log that identifies which software modules contributed which values to the quote event log that identifies which software modules contributed which values to the quote
during startup must also be provided. When required, the log MUST contain enoug h information during startup must also be provided. When required, the log <bcp14>MUST</bcp14 > contain enough information
to demonstrate its integrity by allowing exact reconstruction of the digest to demonstrate its integrity by allowing exact reconstruction of the digest
conveyed in the signed quote (that is, calculating the hash of all the hashes in the conveyed in the signed quote (that is, calculating the hash of all the hashes in the
log should produce the same values as contained in the PCRs; if they don’t match log should produce the same values as contained in the PCRs; if they don't match
, the log , the log
may have been tampered with. See <xref target="using-tpm"/>).</t> may have been tampered with. See <xref target="using-tpm" format="default"/>).<
/t>
<t>There are multiple event log formats which may be supported as viable formats <t>There are multiple event log formats that may be supported as viabl
of Evidence between the Attester and Verifier, e formats of Evidence between the Attester and Verifier;
but to simplify interoperability, RIV focuses on just three:</t> however, to simplify interoperability, RIV focuses on just three:</t>
<ol spacing="normal" type="1">
<t><list style="symbols"> <li>TCG UEFI BIOS event log for TPM 2.0 ("TCG PC Client Specific Pla
<t>TCG UEFI BIOS event log for TPM 2.0 (TCG PC Client Platform Firmware Profil tform Firmware Profile Specification") <xref target="PC-CLIENT-BIOS-TPM-2.0" for
e) <xref target="PC-Client-BIOS-TPM-2.0"/></t> mat="default"/></li>
<t>TCG UEFI BIOS event log for TPM 1.2 (TCG EFI Platform Specification for TPM <li>TCG UEFI BIOS event log for TPM 1.2 ("TCG EFI Platform Specifica
Family 1.1 or tion" for TPM Family 1.1 or
1.2, Section 7) <xref target="PC-Client-EFI-TPM-1.2"/></t> 1.2, Section 7) <xref target="PC-CLIENT-EFI-TPM-1.2" format="default"/></li>
<t>TCG Canonical Event Log <xref target="Canonical-Event-Log"/></t> <li>TCG "Canonical Event Log Format" <xref target="CEL" format="defa
</list></t> ult"/></li>
</ol>
</section> </section>
</section> </section>
</section> </section>
<section anchor="standards-components" title="Standards Components"> <section anchor="standards-components" numbered="true" toc="default">
<name>Standards Components</name>
<section anchor="prerequisites-for-riv" title="Prerequisites for RIV"> <section anchor="prerequisites-for-riv" numbered="true" toc="default">
<name>Prerequisites for RIV</name>
<t>The Reference Interaction Model for Challenge-Response-based Remote Attestati <t>The Reference Interaction Model for Challenge-Response-based Remote A
on (<xref target="I-D.birkholz-rats-reference-interaction-model"/>) ttestation (<xref target="I-D.ietf-rats-reference-interaction-models" format="de
is based on the standard roles defined in <xref target="I-D.ietf-rats-architectu fault"/>)
re"/>. However, additional prerequisites have been established to allow for int is based on the standard roles defined in <xref target="RFC9334" format="default
eroperable RIV use case implementations. These prerequisites are intended to pr "/>. However, additional prerequisites have been established to allow for inter
ovide sufficient context information so that the Verifier can acquire and evalua operable implementations of RIV use cases. These prerequisites are intended to
te measurements collected by the Attester.</t> provide sufficient context information so that the Verifier can acquire and eval
uate measurements collected by the Attester.</t>
<section anchor="unique-device-identity" title="Unique Device Identity"> <section anchor="unique-device-identity" numbered="true" toc="default">
<name>Unique Device Identity</name>
<t>A secure Device Identity (DevID) in the form of an IEEE 802.1AR DevID certifi <t>A DevID in the form of a DevID certificate as specified by IEEE Std
cate <xref target="IEEE-802-1AR"/> must be provisioned in the Attester’s TPMs.</ 802.1AR <xref target="IEEE-802-1AR" format="default"/> must be provisioned in t
t> he Attester's TPMs.</t>
</section>
</section> <section anchor="keys" numbered="true" toc="default">
<section anchor="keys" title="Keys"> <name>Keys</name>
<t>The AK and certificate must also be provisioned on the Attester acc
<t>The Attestation Key (AK) and certificate must also be provisioned on the Atte ording to <xref target="PLATFORM-DEVID-TPM-2.0" format="default"/> or <xref targ
ster according to <xref target="Platform-DevID-TPM-2.0"/>, or <xref target="Plat et="PLATFORM-ID-TPM-1.2" format="default"/>.</t>
form-ID-TPM-1.2"/>.</t> <t>It <bcp14>MUST</bcp14> be possible for the Verifier to determine th
at the Attester's AKs are resident in the same TPM as its DevID keys (see <xref
<t>It MUST be possible for the Verifier to determine that the Attester’s Attesta target="riv-keying" format="default"/> and <xref target="security-cons" format="
tion keys are resident in the same TPM as its DevID keys (see <xref target="riv- default"/>, Security Considerations).</t>
keying"/> and <xref target="security-cons"/> Security Considerations).</t> </section>
<section anchor="RIM-policy" numbered="true" toc="default">
</section> <name>Appraisal Policy for Evidence</name>
<section anchor="RIM-policy" title="Appraisal Policy for Evidence"> <t>As noted in <xref target="RIV-flow" format="default"/>, the Verifie
r may obtain Reference Values from several sources. In addition, administrators
<t>As noted in <xref target="RIV-flow"/>, the Verifier may obtain Reference Valu may make authorized, site-specific changes (e.g., keys in key databases) that c
es from several sources. In addition, administrators may make authorized, site- ould impact attestation results. As such, there could be conflicts, omissions,
specific changes (e.g. keys in key databases) that could impact attestation resu or ambiguities between some Reference Values and collected Evidence.</t>
lts. As such, there could be conflicts, omissions or ambiguities between some R <t>The Verifier <bcp14>MUST</bcp14> have an Appraisal Policy for Evide
eference Values and collected Evidence.</t> nce to evaluate the significance of any discrepancies between different referenc
e sources, or between Reference Values and evidence from logs and quotes.
<t>The Verifier MUST have an Appraisal Policy for Evidence to evaluate the signi
ficance of any discrepancies between different reference sources, or between ref
erence values and evidence from logs and quotes.
While there must be an Appraisal Policy, this document does not specify the form at or mechanism to convey the intended policy, nor does RIV specify mechanisms b y which the results of applying the policy are communicated to the Relying Party .</t> While there must be an Appraisal Policy, this document does not specify the form at or mechanism to convey the intended policy, nor does RIV specify mechanisms b y which the results of applying the policy are communicated to the Relying Party .</t>
</section>
</section> </section>
</section> <section anchor="reference-model-for-challenge-response" numbered="true" t
<section anchor="reference-model-for-challenge-response" title="Reference Model oc="default">
for Challenge-Response"> <name>Reference Model for Challenge-Response</name>
<t>Once the prerequisites for RIV are met, a Verifier is able to acquire
<t>Once the prerequisites for RIV are met, a Verifier is able to acquire Evidenc Evidence from an Attester. <xref target="IETF-Attestation-Information-Flow" fo
e from an Attester. The following diagram illustrates a RIV information flow be rmat="default"/> illustrates a RIV information flow between a Verifier and an At
tween a Verifier and an Attester, tester,
derived from Section 7.1 of <xref target="I-D.birkholz-rats-reference-interactio derived from Section 7.1 of <xref target="I-D.ietf-rats-reference-interaction-mo
n-model"/>. In this diagram, each event with its dels" format="default"/>. In this diagram, each event with its
input and output parameters is shown as “Event(input-params)=&gt;(outputs)”. input and output parameters is shown as "Event(input-params)=&gt;(outputs)".
Event times shown correspond to the time types described within Appendix A of <x The event times shown correspond to the time types described within <xref target
ref target="I-D.ietf-rats-architecture"/>:</t> ="RFC9334" section="A" sectionFormat="of" format="default"/>:</t>
<figure anchor="IETF-Attestation-Information-Flow">
<figure title="IETF Attestation Information Flow" anchor="IETF-Attestation-Infor <name>IETF Attestation Information Flow</name>
mation-Flow"><artwork align="left"><![CDATA[ <artwork align="left" name="" type="" alt=""><![CDATA[
.----------. .-----------------------. .----------. .-----------------------.
| Attester | | Relying Party/Verifier | | Attester | | Relying Party/Verifier |
'----------' '------------------------' '----------' '------------------------'
time(VG) | time(VG) |
generateClaims(attestingEnvironment) | generateClaims(attestingEnvironment) |
| => claims, eventLogs | | => claims, eventLogs |
| | | |
| time(NS) | time(NS)
| <-- requestAttestation(handle, authSecIDs, claimSelection) | | <-- requestAttestation(handle, authSecIDs, claimSelection) |
| | | |
skipping to change at line 727 skipping to change at line 680
generateEvidence(handle, authSecIDs, collectedClaims) | generateEvidence(handle, authSecIDs, collectedClaims) |
| => evidence | | => evidence |
| time(RG,RA) | time(RG,RA)
| evidence, eventLogs -------------------------------------> | | evidence, eventLogs -------------------------------------> |
| | | |
| appraiseEvidence(evidence, eventLogs, refValues) | appraiseEvidence(evidence, eventLogs, refValues)
| attestationResult <= | | attestationResult <= |
| | | |
~ ~ ~ ~
| time(RX) | time(RX)
]]></artwork></figure> ]]></artwork>
</figure>
<t><list style="symbols"> <dl spacing="normal">
<t>Step 1 (time(VG)): One or more Attesting Network Device PCRs are extended w <dt>Step 1 (time(VG)):</dt><dd>One or more attesting network device PC
ith measurements. RIV provides no direct link between Rs are extended with measurements. RIV provides no direct link between
the time at which the event takes place and the time that it’s attested, althoug the time at which the event takes place and the time that it's attested, althoug
h streaming attestation as in <xref target="I-D.birkholz-rats-network-device-sub h streaming attestation as described in <xref target="I-D.ietf-rats-network-devi
scription"/> could.</t> ce-subscription" format="default"/> could.</dd>
<t>Step 2 (time(NS)): The Verifier generates a unique random nonce (“number us <!-- [rfced] Section 3.2. FYI, we will update the title of RFC 9684 when it is f
ed once”), and makes a request for one or more PCRs from an Attester. For inter inalized. -->
operability, this must be accomplished as specified in the YANG Data Model for C <dt>Step 2 (time(NS)):</dt><dd>The Verifier generates a unique random
hallenge-Response-based Remote Attestation Procedures using TPMs <xref target="I nonce ("number used once") and makes a request for one or more PCRs from an Atte
-D.ietf-rats-yang-tpm-charra"/>. TPM1.2 and TPM2.0 both allow nonces as large a ster. For interoperability, this must be accomplished as specified in "A YANG D
s the operative digest size (i.e., 20 or 32 bytes; see <xref target="TPM1.2"></x ata Model for Challenge-Response-Based Remote Attestation (CHARRA) Procedures Us
ref> Part 2, Section 5.5 and <xref target="TPM2.0"></xref> Part 2, Section 10.4. ing Trusted Platform Modules (TPMs)" <xref target="RFC9684" format="default"/>.
4).</t> Both TPM 1.2 and TPM 2.0 allow nonces as large as the operative digest size (i.
<t>Step 3 (time(EG)): On the Attester, measured values are retrieved from the e., 20 or 32 bytes; see <xref target="TPM-1.2" format="default"/> Part 2, Sectio
Attester’s TPM. This requested PCR evidence, n 5.5, and <xref target="TPM-2.0" format="default"/> Part 2, Section 10.4.4).</d
along with the Verifier’s nonce, called a Quote, is signed by the Attestation Ke d>
y (AK) associated with the DevID. Quotes are retrieved according to CHARRA YANG <dt>Step 3 (time(EG)):</dt><dd>On the Attester, measured values are re
model <xref target="I-D.ietf-rats-yang-tpm-charra"/>. At the same time, the At trieved from the Attester's TPM. This requested PCR evidence
tester collects log evidence showing the values have been extended into that PCR along with the Verifier's nonce is called a Quote and is signed by the AK associ
. <xref target="using-tpm"/> gives more detail on how this works, including ref ated with the DevID. Quotes are retrieved according to the CHARRA YANG model <x
erences to the structure and contents of quotes in TPM documents.</t> ref target="RFC9684" format="default"/>. At the same time, the Attester collect
<t>Step 4: Collected Evidence is passed from the Attester to the Verifier</t> s log evidence showing the values have been extended into that PCR. <xref targe
<t>Step 5 (time(RG,RA)): The Verifier reviews the Evidence and takes action as t="using-tpm" format="default"/> gives more detail on how this works and include
needed. As the interaction between Relying Party and Verifier is out of scope s references to the structure and contents of quotes in TPM documents.</dd>
for RIV, this can be described as one step. <list style="symbols"> <dt>Step 4:</dt><dd>The collected Evidence is passed from the Attester
<t>If the signature covering TPM Evidence is not correct, the device SHOUL to the Verifier.</dd>
D NOT be trusted.</t>
<t>If the nonce in the response doesn’t match the Verifier’s nonce, the re
sponse may be a replay, and device SHOULD NOT be trusted.</t>
<t>If the signed PCR values do not match the set of log entries which have
extended a particular PCR, the device SHOULD NOT be trusted.</t>
<t>If the log entries that the Verifier considers important do not match k
nown good values, the device SHOULD NOT be trusted. We note that the process of
collecting and analyzing the log can be omitted if the value in the relevant PC
R is already a known-good value.</t>
<t>If the set of log entries are not seen as acceptable by the Appraisal P
olicy for Evidence, the device SHOULD NOT be trusted.</t>
<t>If time(RG)-time(NS) is greater than the Appraisal Policy for Evidence’
s threshold for assessing freshness, the Evidence is considered stale and SHOULD
NOT be trusted.</t>
</list></t>
</list></t>
<section anchor="transport-and-encoding" title="Transport and Encoding">
<t>Network Management systems may retrieve signed PCR based Evidence using NETCO
NF or RESTCONF with <xref target="I-D.ietf-rats-yang-tpm-charra"/>.
In either case, implementatations must do so using a secure tunnel.</t>
<t>Log Evidence MUST be retrieved via log interfaces specified in <xref target="
I-D.ietf-rats-yang-tpm-charra"/>.</t>
</section>
</section>
<section anchor="peer-to-peer" title="Centralized vs Peer-to-Peer">
<t><xref target="IETF-Attestation-Information-Flow"/> above assumes that the Ver
ifier is trusted, while the Attester is not. In a Peer-to-Peer application such
as two routers negotiating a trust relationship, the two peers can each ask the
other to prove software integrity. In this application, the information flow i
s the same, but each side plays a role both as an Attester and a Verifier. Each
device issues a challenge, and each device responds to the other’s challenge, a
s shown in <xref target="Peer-to-peer-Information-Flow"/>. Peer-to-peer challen
ges, particularly if used to establish a trust relationship between routers, req
uire devices to carry their own signed reference measurements (RIMs). Devices m
ay also have to carry Appraisal Policy for Evidence for each possible peer devic
e so that each device has everything needed for remote attestation, without havi
ng to resort to a central authority.</t>
<figure title="Peer-to-Peer Attestation Information Flow" anchor="Peer-to-peer-I <dt>Step 5 (time(RG,RA)):</dt><dd><t>The Verifier reviews the Eviden
nformation-Flow"><artwork align="left"><![CDATA[ ce and takes action as needed. As the interaction between Relying Party and Ver
ifier is out of scope for RIV, this can be described as one step.</t>
<ul spacing="normal">
<li>If the signature covering TPM Evidence is not correct, the dev
ice <bcp14>SHOULD NOT</bcp14> be trusted.</li>
<li>If the nonce in the response doesn't match the Verifier's nonc
e, the response may be a replay, and the device <bcp14>SHOULD NOT</bcp14> be tru
sted.</li>
<li>If the signed PCR values do not match the set of log entries t
hat have extended a particular PCR, the device <bcp14>SHOULD NOT</bcp14> be trus
ted.</li>
<li>If the log entries that the Verifier considers important do no
t match known good values, the device <bcp14>SHOULD NOT</bcp14> be trusted. We
note that the process of collecting and analyzing the log can be omitted if the
value in the relevant PCR is already a known-good value.</li>
<li>If the set of log entries are not seen as acceptable by the Ap
praisal Policy for Evidence, the device <bcp14>SHOULD NOT</bcp14> be trusted.</l
i>
<li>If time(RG)-time(NS) is greater than the Appraisal Policy for
Evidence's threshold for assessing freshness, the Evidence is considered stale a
nd <bcp14>SHOULD NOT</bcp14> be trusted.</li>
</ul>
</dd>
</dl>
<section anchor="transport-and-encoding" numbered="true" toc="default">
<name>Transport and Encoding</name>
<t>Network Management systems may retrieve signed PCR-based Evidence u
sing NETCONF or RESTCONF with <xref target="RFC9684" format="default"/>.
In either case, implementations must do so using a secure tunnel.</t>
<t>Log Evidence <bcp14>MUST</bcp14> be retrieved via log interfaces sp
ecified in <xref target="RFC9684" format="default"/>.</t>
</section>
</section>
<section anchor="peer-to-peer" numbered="true" toc="default">
<name>Centralized vs. Peer-to-Peer</name>
<t><xref target="IETF-Attestation-Information-Flow" format="default"/> a
ssumes that the Verifier is trusted, while the Attester is not. In a peer-to-pe
er application such as two routers negotiating a trust relationship, the two pee
rs can each ask the other to prove software integrity. In this application, the
information flow is the same, but each side plays a role both as an Attester an
d a Verifier. Each device issues a challenge, and each device responds to the o
ther's challenge, as shown in <xref target="Peer-to-peer-Information-Flow" forma
t="default"/>. Peer-to-peer challenges, particularly if used to establish a tru
st relationship between routers, require devices to carry their own signed refer
ence measurements (RIMs). Devices may also have to carry an appraisal policy fo
r evidence for each possible peer device so that each device has everything need
ed for remote attestation, without having to resort to a central authority.</t>
<figure anchor="Peer-to-peer-Information-Flow">
<name>Peer-to-Peer Attestation Information Flow</name>
<artwork align="left" name="" type="" alt=""><![CDATA[
+---------------+ +---------------+ +---------------+ +---------------+
| RefVal | | RefVal | | RefVal | | RefVal |
| Provider A | | Provider B | | Provider A | | Provider B |
| Firmware | | Firmware | | Firmware | | Firmware |
| Configuration | | Configuration | | Configuration | | Configuration |
| Authority | | Authority | | Authority | | Authority |
| | | | | | | |
+---------------+ +---------------+ +---------------+ +---------------+
| | | |
| |Step 0B | |Step 0B
skipping to change at line 787 skipping to change at line 742
|- Router A -| Step 3 |- Router B -| | / |- Router A -| Step 3 |- Router B -| | /
| | | | | | | | | |
| | | | | | | | | |
| | Step 1 | | | \ | | Step 1 | | | \
| Verifier |<------>| Attester |<-+ | Router A | Verifier |<------>| Attester |<-+ | Router A
| |<------>| | |- Challenges | |<------>| | |- Challenges
| | Step 2 | | | Router B | | Step 2 | | | Router B
| | | | | | | | | |
| |<-------| | | | |<-------| | |
+------------+ Step 3 +------------+ / +------------+ Step 3 +------------+ /
]]></artwork>
]]></artwork></figure> </figure>
<t>In this application, each device may need to be equipped with signed
<t>In this application, each device may need to be equipped with signed RIMs to RIMs to act as an Attester, and to allow each device to act as a Verifier, each
act as an Attester, and also an Appraisal Policy for Evidence and a selection of may need to be equipped with an Appraisal Policy for Evidence and a selection of
trusted X.509 root certificates, to allow the device to act as a Verifier. An trusted X.509 root certificates also. An existing link layer protocol such as
existing link layer protocol such as 802.1X <xref target="IEEE-802.1X"/> or 802 802.1X <xref target="IEEE-802.1X" format="default"/> or 802.1AE <xref target="I
.1AE <xref target="IEEE-802.1AE"/>, with Evidence being enclosed over a variant EEE-802.1AE" format="default"/>, with Evidence being enclosed over a variant of
of EAP <xref target="RFC3748"/> or LLDP <xref target="LLDP"/> are suitable metho the Extensible Authentication Protocol (EAP) <xref target="RFC3748" format="defa
ds for such an exchange. ult"/> or Link Layer Discovery Protocol (LLDP) <xref target="LLDP" format="defau
lt"/>, are suitable methods for such an exchange.
Details of peer-to-peer operation are out of scope for this document.</t> Details of peer-to-peer operation are out of scope for this document.</t>
</section>
</section> </section>
</section> <section anchor="privacy-considerations" numbered="true" toc="default">
<section anchor="privacy-considerations" title="Privacy Considerations"> <name>Privacy Considerations</name>
<t>Network equipment, such as routers, switches, and firewalls, has a key
<t>Network equipment, such as routers, switches and firewalls, has a key role to role to play in guarding the privacy of individuals using the network. Network
play in guarding the privacy of individuals using the network. Network equipme equipment generally adheres to several rules to protect privacy:</t>
nt generally adheres to several rules to protect privacy:</t> <ul spacing="normal">
<li>
<t><list style="symbols"> <t>Packets passing through the device must not be sent to unauthorized
<t>Packets passing through the device must not be sent to unauthorized destina destinations. For example: </t>
tions. For example: <list style="symbols"> <ul spacing="normal">
<t>Routers often act as Policy Enforcement Points, where individual subscr <li>Routers often act as Policy Enforcement Points, where individual
ibers may be checked for subscribers may be checked for
authorization to access a network. Subscriber login information must not be rel authorization to access a network. Subscriber login information must not be rel
eased to unauthorized parties.</t> eased to unauthorized parties.</li>
<t>Network equipment is often called upon to block access to protected res <li>Network equipment is often called upon to block access to protec
ources from unauthorized users.</t> ted resources from unauthorized users.</li>
</list></t> </ul>
<t>Routing information, such as the identity of a router’s peers, must not be </li>
leaked to unauthorized neighbors.</t> <li>Routing information, such as the identity of a router's peers, must
<t>If configured, encryption and decryption of traffic must be carried out rel not be leaked to unauthorized neighbors.</li>
iably, while protecting keys and credentials.</t> <li>If configured, encryption and decryption of traffic must be carried
</list></t> out reliably, while protecting keys and credentials.</li>
</ul>
<t>Functions that protect privacy are implemented as part of each layer of hardw <t>Functions that protect privacy are implemented as part of each layer of
are and software that hardware and software that
makes up the networking device. makes up the networking device.
In light of these requirements for protecting the privacy of users of the networ k, the network equipment In light of these requirements for protecting the privacy of users of the networ k, the network equipment
must identify itself, and its boot configuration and measured device state (for example, PCR values), must identify itself, and its boot configuration and measured device state (for example, PCR values),
to the equipment’s administrator, so there’s no uncertainty as to what function to the equipment's administrator so there's no uncertainty about the device's fu
each device and nction and
configuration is configured to carry out. Attestation is a component that allows configuration. Attestation is a component that allows the administrator to ensur
the administrator to ensure that the network e that the network
provides individual and peer privacy guarantees, even though the device itself m ay not have a provides individual and peer privacy guarantees, even though the device itself m ay not have a
right to keep its identity secret.</t> right to keep its identity secret.</t>
<t>See <xref target="NET-EQ" format="default"/> for more context on privac
<t>See <xref target="NetEq"/> for more context on privacy in networking devices. y in networking devices.</t>
</t> <t>While attestation information from network devices is not likely to con
tain privacy-sensitive content regarding
<t>While attestation information from network devices is not likely to contain p
rivacy-sensitive content regarding
network users, administrators may want to keep attestation records confidential to avoid disclosing versions of network users, administrators may want to keep attestation records confidential to avoid disclosing versions of
software loaded on the device, information which could facilitate attacks agains software loaded on the device, which is information that could facilitate attack
t known vulnerabilities.</t> s against known vulnerabilities.</t>
</section>
</section> <section anchor="security-cons" numbered="true" toc="default">
<section anchor="security-cons" title="Security Considerations"> <name>Security Considerations</name>
<t>Specifications such as TLS <xref target="RFC8446" format="default"/> an
<t>Specifications such as <xref target="RFC8446"/> (TLS) and <xref target="RFC79 d YANG <xref target="RFC7950" format="default"/> contain considerable advice on
50"/> (YANG) contain considerable advice on keeping keeping
network-connected systems secure. This section outlines specific risks and miti gations related to attestation.</t> network-connected systems secure. This section outlines specific risks and miti gations related to attestation.</t>
<t>Attestation Evidence obtained by the RIV procedure is subject to a numb
<t>Attestation Evidence obtained by the RIV procedure is subject to a number of er of attacks:</t>
attacks:</t> <ul spacing="normal">
<li>Keys may be compromised.</li>
<t><list style="symbols"> <li>A counterfeit device may attempt to impersonate (spoof) a known auth
<t>Keys may be compromised.</t> entic device.</li>
<t>A counterfeit device may attempt to impersonate (spoof) a known authentic d <li>Person-in-the-middle attacks may be used by a compromised device to
evice.</t> attempt to deliver
<t>Person-in-the-middle attacks may be used by a compromised device to attempt responses that originate in an authentic device.</li>
to deliver <li>Replay attacks may be attempted by a compromised device.</li>
responses that originate in an authentic device.</t> </ul>
<t>Replay attacks may be attempted by a compromised device.</t> <section anchor="keys-used-in-riv" numbered="true" toc="default">
</list></t> <name>Keys Used in RIV</name>
<t>Trustworthiness of RIV attestation depends strongly on the validity o
<section anchor="keys-used-in-riv" title="Keys Used in RIV"> f keys used for identity
<t>Trustworthiness of RIV attestation depends strongly on the validity of keys u
sed for identity
and attestation reports. RIV takes full advantage of TPM capabilities to ensure that evidence can be trusted.</t> and attestation reports. RIV takes full advantage of TPM capabilities to ensure that evidence can be trusted.</t>
<t>Two sets of key pairs are relevant to RIV attestation:</t>
<t>Two sets of key-pairs are relevant to RIV attestation:</t> <ul spacing="normal">
<li>A DevID key pair is used to certify the identity of the device in
<t><list style="symbols"> which the TPM is installed.</li>
<t>A DevID key-pair is used to certify the identity of the device in which the <li>An AK key pair is used to certify attestation Evidence (i.e., quot
TPM is installed.</t> es) and
<t>An Attestation Key-pair (AK) key is used to certify attestation Evidence (c to provide evidence for integrity of the device software.</li>
alled ‘quotes’ in TCG documents), </ul>
used to provide evidence for integrity of the software on the device</t> <t>TPM practices usually require that these keys be different to ensure
</list></t> that a general-purpose
<t>TPM practices usually require that these keys be different, as a way of ensur
ing that a general-purpose
signing key cannot be used to spoof an attestation quote.</t> signing key cannot be used to spoof an attestation quote.</t>
<t>In each case, the private half of the key is known only to the TPM an
<t>In each case, the private half of the key is known only to the TPM, and canno d cannot be
t be retrieved externally, even by a trusted party. To ensure that's the case,
retrieved externally, even by a trusted party. To ensure that’s the case, specification-compliant private/public key pairs are generated inside the TPM, w
specification-compliant private/public key-pairs are generated inside the TPM, w here they are never
here they are never exposed and cannot be extracted (see <xref target="PLATFORM-DEVID-TPM-2.0" forma
exposed, and cannot be extracted (See <xref target="Platform-DevID-TPM-2.0"/>).< t="default"/>).</t>
/t> <t>Keeping keys safe is a critical enabler of trustworthiness, but it's
just part of attestation security; knowing which keys are bound
<t>Keeping keys safe is a critical enabler of trustworthiness, but it’s just par
t of attestation security; knowing which keys are bound
to the device in question is just as important in an environment where private k eys are never exposed.</t> to the device in question is just as important in an environment where private k eys are never exposed.</t>
<t>While there are many ways to manage keys in a TPM (see <xref target="
<t>While there are many ways to manage keys in a TPM (see <xref target="Platform PLATFORM-DEVID-TPM-2.0" format="default"/>), RIV includes
-DevID-TPM-2.0"/>), RIV includes support for "zero touch" provisioning (also known as zero touch onboarding) of f
support for “zero touch” provisioning (also known as zero-touch onboarding) of f ielded
ielded devices (e.g., SZTP <xref target="RFC8572" format="default"/>), where keys that
devices (e.g., Secure ZTP, <xref target="RFC8572"/>), where keys which have pred have predictable trust properties are
ictable trust properties are
provisioned by the device vendor.</t> provisioned by the device vendor.</t>
<t>Device identity in RIV is based on DevID defined by IEEE Std 802.1AR.
<t>Device identity in RIV is based on IEEE 802.1AR Device Identity (DevID). This This specification provides several elements:</t>
specification provides several elements:</t> <ul spacing="normal">
<li>A DevID requires a unique key pair for each device, accompanied by
<t><list style="symbols"> an X.509 certificate.</li>
<t>A DevID requires a unique key pair for each device, accompanied by an X.509 <li>The private portion of the DevID key is to be stored in the device
certificate,</t> , in a manner that provides confidentiality (Section 6.2.5 of <xref target="IEEE
<t>The private portion of the DevID key is to be stored in the device, in a ma -802-1AR" format="default"/>).</li>
nner that provides confidentiality (Section 6.2.5 <xref target="IEEE-802-1AR"/>) </ul>
</t> <t>The X.509 certificate contains several components:</t>
</list></t> <ul spacing="normal">
<li>The public part of the unique DevID key assigned to that device al
<t>The X.509 certificate contains several components:</t> lows a challenge of identity.</li>
<li>An identifying string that's unique to the manufacturer of the dev
<t><list style="symbols"> ice. This is normally the
<t>The public part of the unique DevID key assigned to that device allows a ch serial number of the unit, which might also be printed on a label on the device.
allenge of identity.</t> </li>
<t>An identifying string that’s unique to the manufacturer of the device. Thi <li>The certificate must be signed by a key traceable to the manufactu
s is normally the rer's root key.</li>
serial number of the unit, which might also be printed on a label on the device. </ul>
</t> <t>With these elements, the device's manufacturer and serial number can
<t>The certificate must be signed by a key traceable to the manufacturer’s roo be identified by analyzing the
t key.</t> DevID certificate plus the chain of intermediate certificates leading back to th
</list></t> e manufacturer's root
<t>With these elements, the device’s manufacturer and serial number can be ident
ified by analyzing the
DevID certificate plus the chain of intermediate certificates leading back to th
e manufacturer’s root
certificate. As is conventional in TLS or SSH connections, a random nonce must be signed by the device certificate. As is conventional in TLS or SSH connections, a random nonce must be signed by the device
in response to a challenge, in response to a challenge,
proving possession of its DevID private key.</t> proving possession of its DevID private key.</t>
<t>RIV uses the DevID to validate a TLS or SSH connection to the device
as the attestation session begins. Security of
this process derives from TLS or SSH security, with the DevID, which contains a
device serial number, providing proof that the session terminates on
the intended device. See <xref target="RFC8446" format="default"/> <xref target=
"RFC4253" format="default"/>.</t>
<t>Evidence of software integrity is delivered in the form of a quote th
at is signed by the TPM
itself and accompanied by an IAK certificate containing the same identity inform
ation as the DevID. Because the contents of the quote are signed inside the TPM
, any external
modification (including reformatting to a different data format) after measureme
nts have been taken will be detected
as tampering. An unbroken chain of trust is essential for ensuring that blocks
of code that are taking
measurements have been verified before execution (see <xref target="RIV-Attestat
ion-Model" format="default"/>).</t>
<t>Requiring measurements of the operating software to be signed by a ke
y known only to the TPM also
removes the need to trust the device's operating software (beyond the first meas
urement in the RTM; see below).
If malicious software makes any changes to a quote
in the device itself, or in the path back to the Verifier, the signature on the
quote will
be invalidated.</t>
<t>A critical feature of the YANG model described in <xref target="RFC96
84" format="default"/> is the ability to carry TPM data structures in their TCG-
defined format, without requiring any changes to the structures as they were sig
ned and delivered by the TPM. While alternate methods of conveying TPM quotes c
ould reduce redundant information, or add another layer of signing using externa
l keys, the implementation <bcp14>MUST</bcp14> preserve the TPM signing so that
tampering anywhere in the path between the TPM itself and the Verifier can be de
tected.</t>
</section>
<section anchor="pitm" numbered="true" toc="default">
<name>Prevention of Spoofing and Person-in-the-Middle Attacks</name>
<t>Prevention of spoofing attacks against attestation systems is also im
portant. There are several cases to consider:</t>
<ul spacing="normal">
<li>The entire device could be spoofed. If the Verifier goes to apprai
se a specific Attester, it might be redirected to a different Attester.</li>
<li>A compromised device could have a valid DevID, but substitute a qu
ote from a known-good device instead of returning its own, as described in <xref
target="RFC6813" format="default"/>.</li>
<li>A device with a compromised OS could return a fabricated quote pro
viding spoofed attestation Evidence.</li>
</ul>
<t>Use of the 802.1AR DevID in the TPM provides protection against the c
ase of a spoofed device by ensuring that the Verifier's TLS or SSH session is in
fact terminating on the right device.</t>
<t>Protection against spoofed quotes from a device with valid identity i
s a bit more complex.
An identity key must be available to sign any kind of nonce or hash offered by t
he Verifier,
and consequently, could be used to sign a fabricated quote. To block a spoofed
Attestation
Result, the quote generated inside the TPM must be signed by
a key, known as an AK, that's different from the DevID.</t>
<t>Given separate Attestation and DevID keys, the
binding between the AK and the same device must also be proven to
prevent a person-in-the-middle attack (e.g., the "Asokan Attack" <xref target="R
FC6813" format="default"/>).</t>
<t>This is accomplished in RIV through use of an AK certificate with the
same elements as the DevID
(same manufacturer's serial number and signed by the same manufacturer's key), b
ut containing
the device's unique AK public key instead of the DevID public key.
This binding between DevID and AK certificates is critical to reliable attestati
on.</t>
<t>The TCG document "TPM 2.0 Keys for Device Identity and Attestation" <
xref target="PLATFORM-DEVID-TPM-2.0" format="default"/> specifies
OIDs for Attestation Certificates that allow the CA to mark a key as specificall
y known to be
an AK.</t>
<t>These two key pairs and certificates are used together:</t>
<ul spacing="normal">
<li>The DevID is used to validate a TLS connection terminating on the
device with a known serial number.</li>
<li>The AK is used to sign attestation quotes, which provides proof th
at the attestation
evidence comes from the same device.</li>
</ul>
</section>
<section anchor="replay-attacks" numbered="true" toc="default">
<name>Replay Attacks</name>
<t>Replay attacks, where the results of a previous attestation are submi
tted in response to subsequent requests,
are usually prevented by the inclusion of a random nonce in the request to the T
PM
for a quote. Each request from the Verifier includes a new random number (a non
ce). The resulting
quote signed by the TPM contains the same nonce, which allows the Verifier to de
termine
freshness (i.e., that the resulting quote was generated in response to the Verif
ier's specific request).
"Time-Based Uni-Directional Attestation" <xref target="I-D.birkholz-rats-tuda" f
ormat="default"/> provides an alternate mechanism
to verify freshness without requiring a request/response cycle.</t>
</section>
<section anchor="owner-signed-keys" numbered="true" toc="default">
<name>Owner-Signed Keys</name>
<t>Although device manufacturers must pre-provision devices with easily
verified DevID and AK certificates
if SZTP such as described in <xref target="RFC8572" format="default"/> is to be
supported,
use of those credentials is not mandatory. IEEE Std 802.1AR incorporates the id
ea of an
IDevID, which is provisioned by the manufacturer, and a LDevID, which is provisi
oned by the owner of
the device. RIV and <xref target="PLATFORM-DEVID-TPM-2.0" format="default"/> ex
tend that concept by defining an IAK and
LAK with the same properties.</t>
<t>Device owners can use any method to provision the local credentials.<
/t>
<ul spacing="normal">
<li>The TCG document <xref target="PLATFORM-DEVID-TPM-2.0" format="def
ault"/> shows how the IAKs
can be used to certify LDevID and LAK keys. The use of the LDevID and LAK allow
s the device owner
to use a uniform identity structure across device types from multiple manufactur
ers (in the same way
that an "Asset Tag" is used by many enterprises to identify devices they own).
The TCG document
<xref target="PROV-TPM-2.0" format="default"/> also contains guidance on provisi
oning local identity keys in TPM 2.0.
Owners should follow the same practice of binding LDevID and LAK as the manufact
urer would for IDevID and IAK.
See <xref target="riv-keying" format="default"/>.</li>
<li>Device owners, however, can use any other mechanism they want, inc
luding physical inspection and programming in a secure location, to assure thems
elves that local identity
certificates are inserted into the intended device
if they prefer to avoid placing trust in the manufacturer-provided keys.</li>
</ul>
<t>Clearly, local keys can't be used for SZTP; installation of the local
keys
can only be done by some process that runs before the device is installed for ne
twork operation,
or by using procedures such as those outlined in Bootstrapping Remote Secure Key
Infrastructure (BRSKI) <xref target="RFC8995" format="default"/>.</t>
<t>On the other end of the device lifecycle, provision should be made to
wipe local keys when a device
is decommissioned to indicate that the device is no longer owned by the enterpri
se. The manufacturer's
initial identity keys must be preserved, as they contain no information that's n
ot already printed on
the device's serial number plate.</t>
</section>
<section anchor="other-factors-for-trustworthy-operation" numbered="true"
toc="default">
<name>Other Factors for Trustworthy Operation</name>
<t>In addition to the trustworthy provisioning of keys, RIV depends on a
number of other factors for trustworthy operation.</t>
<ul spacing="normal">
<li>Secure identity depends on mechanisms to prevent per-device secret
keys from being compromised. The TPM
provides this capability as a Root of Trust for Storage.</li>
<li>Attestation depends on an unbroken chain of measurements, starting
from the very first
measurement. See <xref target="using-tpm" format="default"/> for background on
TPM practices.</li>
<li>That first measurement is made by code called the RTM, typically d
one by trusted
firmware stored in boot flash. Mechanisms for maintaining the trustworthiness o
f the RTM are out of
scope for RIV, but could include immutable firmware, signed updates, or a vendor
-specific hardware
verification technique. See <xref target="root-of-trust" format="default"/> f
or background on Roots of Trust.</li>
<li>The device owner <bcp14>SHOULD</bcp14> provide some level of physi
cal defense for the device. If a TPM that has already been programmed
with an authentic DevID is stolen and is inserted into a counterfeit device, att
estation of that counterfeit
device may become indistinguishable from an authentic device.</li>
</ul>
<t>RIV also depends on reliable Reference Values, as expressed by the RI
M <xref target="RIM" format="default"/>. The definition of
trust procedures for RIMs is out of scope for RIV, and the device owner is free
to use any policy to validate
a set of reference measurements. It should also be noted that, while RIV can pr
ovide a reliable indication that a known software package is in use by the devic
e and that the package has not been tampered with, it is the device owner's resp
onsibility to determine that it's the correct package for the application.</t>
<t>RIMs may be conveyed either out-of-band or in-band as part of the att
estation
process (see <xref target="RIM-policy" format="default"/>). However, for networ
k devices, where software is usually shipped as a self-contained
package, RIMs signed by the manufacturer and delivered in-band may be more conve
nient for the device owner.</t>
<t>The validity of RIV attestation results is also influenced by procedu
res used to create Reference Values:</t>
<ul spacing="normal">
<li>While the RIM itself is signed, supply chains <bcp14>SHOULD</bcp14
> be carefully scrutinized to ensure that the values are
not subject to unexpected manipulation prior to signing. Insider attacks agains
t code bases and build chains
are particularly hard to spot.</li>
<li>Designers <bcp14>SHOULD</bcp14> guard against hash collision attac
ks. RIMs often give hashes for large objects
of indeterminate size. If one of the measured objects can be replaced with an im
plant engineered to produce
the same hash, RIV will be unable to detect the substitution. TPM 1.2 only uses
SHA-1 hashes, which have been
shown to be susceptible to collision attack. TPM 2.0 will produce quotes with S
HA-256, which so far has resisted
such attacks. Consequently, RIV implementations <bcp14>SHOULD</bcp14> use TPM 2
.0.</li>
</ul>
</section>
</section>
<section anchor="IANA" numbered="true" toc="default">
<name>IANA Considerations</name>
<t>This document has no IANA actions.</t>
</section>
<section anchor="conclusion" numbered="true" toc="default">
<name>Conclusion</name>
<t>TCG technologies can play an important part in the implementation of RI
V.
Standards for many of the components needed for
implementation of RIV already exist:</t>
<ul spacing="normal">
<li>Platform identity can be based on IEEE 802.1AR DevID, coupled with
careful supply-chain management by the manufacturer.</li>
<li>Complex supply chains can be certified using TCG Platform Certificat
es <xref target="PLATFORM-CERTS" format="default"/>.</li>
<li>The TCG TAP mechanism coupled with <xref target="RFC9684" format="de
fault"/> can be used to retrieve attestation evidence.</li>
<li>Reference Values must be conveyed from the software authority (e.g.,
the manufacturer) in RIMs to the system in which verification will take place.
IETF and TCG
SWID and CoSWID work (<xref target="RFC9393" format="default"/> <xref target="RI
M" format="default"/>) forms the basis for this function.</li>
</ul>
</section>
</middle>
<back>
<t>RIV uses the DevID to validate a TLS or SSH connection to the device as the a <displayreference target="I-D.ietf-rats-reference-interaction-models" to="RATS-I
ttestation session begins. Security of NTERACTION-MODELS"/>
this process derives from TLS or SSH security, with the DevID, containing a devi <displayreference target="I-D.richardson-rats-usecases" to="RATS-USECASES"/>
ce serial number, providing proof that the session terminates on <displayreference target="I-D.birkholz-rats-tuda" to="RATS-TUDA"/>
the intended device. See <xref target="RFC8446"/>, <xref target="RFC4253"/>.</t> <displayreference target="I-D.ietf-rats-network-device-subscription" to="RATS-NE
T-DEV-SUB"/>
<displayreference target="I-D.ietf-rats-eat" to="RATS-EAT"/>
<t>Evidence of software integrity is delivered in the form of a quote signed by <references>
the TPM <name>References</name>
itself, accompanied by an IAK certificate containing the same identity informati <references>
on as the DevID. Because the contents of the quote are signed inside the TPM, a <name>Normative References</name>
ny external <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.21
modification (including reformatting to a different data format) after measureme 19.xml"/>
nts have been taken will be detected <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.84
as tampering. An unbroken chain of trust is essential to ensuring that blocks o 46.xml"/>
f code that are taking <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.42
measurements have been verified before execution (see <xref target="RIV-Attestat 53.xml"/>
ion-Model"/>).</t> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.62
41.xml"/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.81
74.xml"/>
<xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.52
80.xml"/>
<t>Requiring measurements of the operating software to be signed by a key known <!-- [I-D.ietf-rats-yang-tpm-charra] companion document RFC 9684 -->
only to the TPM also
removes the need to trust the device’s operating software (beyond the first meas
urement in the RTM; see below); any
changes to the quote, generated and signed by the TPM itself, made by malicious
device software, or in
the path back to the Verifier, will invalidate the signature on the quote.</t>
<t>A critical feature of the YANG model described in <xref target="I-D.ietf-rats <reference anchor='RFC9684' target='https://www.rfc-editor.org/info/rfc9684'>
-yang-tpm-charra"/> is the ability to carry TPM data structures in their TCG-def <front>
ined format, without requiring any changes to the structures as they were signed <title>A YANG Data Model for Challenge-Response-Based Remote Attestation (CH
and delivered by the TPM. While alternate methods of conveying TPM quotes coul ARRA) Procedures Using Trusted Platform Modules (TPMs)</title>
d compress out redundant information, or add another layer of signing using exte <author initials='H' surname='Birkholz' fullname='Henk Birkholz'>
rnal keys, the implementation MUST preserve the TPM signing, so that tampering a <organization />
nywhere in the path between the TPM itself and the Verifier can be detected.</t> </author>
<author initials='M' surname='Eckel' fullname='Michael Eckel'>
<organization />
</author>
<author initials='S' surname='Bhandari' fullname='Shwetha Bhandari'>
<organization />
</author>
<author initials='E' surname='Voit' fullname='Eric Voit'>
<organization />
</author>
<author initials='B' surname='Sulzen' fullname='Bill Sulzen'>
<organization />
</author>
<author initials='L' surname='Xia' fullname='Liang Xia'>
<organization />
</author>
<author initials='T' surname='Laffey' fullname='Tom Laffey'>
<organization />
</author>
<author initials='G' surname='Fedorkow' fullname='Guy Fedorkow'>
<organization />
</author>
<date year='2024' month='October'/>
</front>
<seriesInfo name="RFC" value="9684"/>
<seriesInfo name="DOI" value="10.17487/RFC9684"/>
</reference>
</section> <!-- [I-D.ietf-sacm-coswid] has been published as RFC 9393. -->
<section anchor="pitm" title="Prevention of Spoofing and Person-in-the-Middle At <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.93
tacks"> 93.xml"/>
<t>Prevention of spoofing attacks against attestation systems is also important. <!-- [I-D.ietf-rats-architecture] has been published as RFC 9334. -->
There are several cases to consider:</t> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.93
34.xml"/>
<t><list style="symbols"> <reference anchor="IEEE-802-1AR" >
<t>The entire device could be spoofed. If the Verifier goes to appraise a spec <front>
ific Attester, it might be redirected to a different Attester.</t> <title>IEEE Standard for Local and Metropolitan Area Networks - Secu
<t>A compromised device could have a valid DevID, but substitute a quote from re Device Identity</title>
a knonwn-good device, instead of returning its own, as described in <xref target <author>
="RFC6813"/>.</t> <organization>IEEE</organization>
<t>A device with a compromised OS could return a fabricated quote providing sp </author>
oofed attestation Evidence.</t> <date year="2018" month="August"/>
</list></t> </front>
<seriesInfo name="IEEE Std" value="802.1AR-2018"/>
<seriesInfo name="DOI" value="10.1109/IEEESTD.2018.8423794"/>
</reference>
<t>Use of the 802.1AR Device Identity (DevID) in the TPM provides protection aga <reference anchor="TAP" target="https://trustedcomputinggroup.org/wp-con
inst the case of a spoofed device, by ensuring that the Verifier’s TLS or SSH se tent/uploads/TNC_TAP_Information_Model_v1.00_r0.36-FINAL.pdf">
ssion is in fact terminating on the right device.</t> <front>
<title>TCG Trusted Attestation Protocol (TAP) Information Model for
TPM Families 1.2 and 2.0 and DICE Family 1.0</title>
<author>
<organization>Trusted Computing Group</organization>
</author>
<date year="2018" month="October"/>
</front>
<refcontent>Version 1.0, Revision 0.36</refcontent>
</reference>
<t>Protection against spoofed quotes from a device with valid identity is a bit <reference anchor="CEL" target="https://trustedcomputinggroup.org/wp-con
more complex. tent/uploads/TCG_IWG_CEL_v1_r0p41_pub.pdf">
An identity key must be available to sign any kind of nonce or hash offered by t <front>
he Verifier, <title>Canonical Event Log Format</title>
and consequently, could be used to sign a fabricated quote. To block a spoofed <author>
Attestation <organization>Trusted Computing Group</organization>
Result, the quote generated inside the TPM must be signed by </author>
a key that’s different from the DevID, called an Attestation Key (AK).</t> <date year="2022" month="February"/>
</front>
<refcontent>Version 1.0, Revision 0.41</refcontent>
</reference>
<t>Given separate Attestation and DevID keys, the <reference anchor="PC-CLIENT-BIOS-TPM-2.0" target="https://trustedcomput
binding between the AK and the same device must also be proven to inggroup.org/resource/pc-client-specific-platform-firmware-profile-specification
prevent a person-in-the-middle attack (e.g., the ‘Asokan Attack’ <xref target="R /">
FC6813"/>).</t> <front>
<title>TCG PC Client Specific Platform Firmware Profile Specificatio
n</title>
<author>
<organization>Trusted Computing Group</organization>
</author>
<date year="2021" month="May"/>
</front>
<refcontent>Family "2.0", Level 00, Version 1.05, Revision 23</refconte
nt>
</reference>
<t>This is accomplished in RIV through use of an AK certificate with the same el <reference anchor="PC-CLIENT-EFI-TPM-1.2" target="https://trustedcomputi
ements as the DevID nggroup.org/resource/tcg-efi-platform-specification/">
(same manufacturer’s serial number, signed by the same manufacturer’s key), but <front>
containing <title>TCG EFI Platform Specification</title>
the device’s unique AK public key instead of the DevID public key. <author>
This binding between DevID and AK certificates is critical to reliable attestati <organization>Trusted Computing Group</organization>
on.</t> </author>
<date year="2014" month="January"/>
</front>
<refcontent>For TPM Family 1.1 or 1.2, Version 1.22, Revision 15</refco
ntent>
</reference>
<t>The TCG document TPM 2.0 Keys for Device Identity and Attestation <xref targe <reference anchor="RIM" target="https://trustedcomputinggroup.org/resour
t="Platform-DevID-TPM-2.0"/> specifies ce/tcg-reference-integrity-manifest-rim-information-model/">
OIDs for Attestation Certificates that allow the CA to mark a key as specificall <front>
y known to be <title>TCG Reference Integrity Manifest (RIM) Information Model</tit
an Attestation key.</t> le>
<author>
<organization>Trusted Computing Group</organization>
</author>
<date year="2020" month="November"/>
</front>
<refcontent>Version 1.01, Revision 0.16</refcontent>
</reference>
<t>These two key-pairs and certificates are used together:</t> <reference anchor="PC-CLIENT-RIM" target="https://trustedcomputinggroup.
org/resource/tcg-pc-client-reference-integrity-manifest-specification/">
<front>
<title>TCG PC Client Reference Integrity Manifest Specification</tit
le>
<author>
<organization>Trusted Computing Group</organization>
</author>
<date year="2020" month="November"/>
</front>
<refcontent>Version 1.04</refcontent>
</reference>
<t><list style="symbols"> <reference anchor="PLATFORM-DEVID-TPM-2.0" target="https://trustedcomput
<t>The DevID is used to validate a TLS connection terminating on the device wi inggroup.org/resource/tpm-2-0-keys-for-device-identity-and-attestation/">
th a known serial number.</t> <front>
<t>The AK is used to sign attestation quotes, providing proof that the attesta <title>TPM 2.0 Keys for Device Identity and Attestation</title>
tion <author>
evidence comes from the same device.</t> <organization>Trusted Computing Group</organization>
</list></t> </author>
<date year="2021" month="October"/>
</front>
<refcontent>Version 1.00, Revision 12</refcontent>
</reference>
</section> <reference anchor="PLATFORM-ID-TPM-1.2" target="https://trustedcomputing
<section anchor="replay-attacks" title="Replay Attacks"> group.org/resource/tpm-keys-for-platform-identity-for-tpm-1-2-2/">
<front>
<title>TCG Infrastructure WG TPM Keys for Platform Identity for TPM
1.2</title>
<author>
<organization>Trusted Computing Group</organization>
</author>
<date year="2015" month="August"/>
</front>
<refcontent>Specification Version 1.0, Revision 3</refcontent>
</reference>
<t>Replay attacks, where results of a previous attestation are submitted in resp <reference anchor="SWID" target="https://www.iso.org/standard/65666.html
onse to subsequent requests, ">
are usually prevented by inclusion of a random nonce in the request to the TPM <front>
for a quote. Each request from the Verifier includes a new random number (a non <title>Information technology - IT asset management - Part 2: Softwa
ce). The resulting re identification tag</title>
quote signed by the TPM contains the same nonce, allowing the Verifier to determ <author>
ine <organization>ISO/IEC</organization>
freshness, (i.e., that the resulting quote was generated in response to the Veri </author>
fier’s specific request). <date year="2015" month="October"/>
Time-Based Uni-directional Attestation <xref target="I-D.birkholz-rats-tuda"/> p </front>
rovides an alternate mechanism <seriesInfo name="ISO/IEC" value="19770-2:2015"/>
to verify freshness without requiring a request/response cycle.</t> </reference>
</section> <reference anchor="IMA" target="https://www.kernel.org/doc/html/v6.11/ad
<section anchor="owner-signed-keys" title="Owner-Signed Keys"> min-guide/device-mapper/dm-ima.html">
<front>
<title>dm-ima</title>
<author>
<organization>The kernel development community</organization>
</author>
<date year="2024" month="September" day="15"/>
</front>
<refcontent>Linux Kernel 6.11</refcontent>
<annotation>The latest version can be found at <eref target="https://d
ocs.kernel.org/admin-guide/device-mapper/dm-ima.html"/>.</annotation>
</reference>
</references>
<references>
<name>Informative References</name>
<t>Although device manufacturers must pre-provision devices with easily verified <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.681
DevID and AK certificates 3.xml"/>
if zero-touch provisioning such as described in <xref target="RFC8572"/> is to b <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.374
e supported, 8.xml"/>
use of those credentials is not mandatory. IEEE 802.1AR incorporates the idea o <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.952
f an Initial Device ID 5.xml"/>
(IDevID), provisioned by the manufacturer, and a Local Device ID (LDevID) provis <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.899
ioned by the owner of 5.xml"/>
the device. RIV and <xref target="Platform-DevID-TPM-2.0"/> extends that concep <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.795
t by defining an Initial Attestation Key (IAK) and Local Attestation 0.xml"/>
Key (LAK) with the same properties.</t> <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.857
2.xml"/>
<t>Device owners can use any method to provision the Local credentials.</t> <!-- [I-D.birkholz-rats-reference-interaction-model] replaced by [I-D.ietf-rats- reference-interaction-models] IESG state I-D Exists -->
<t><list style="symbols"> <xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D.
<t>TCG document <xref target="Platform-DevID-TPM-2.0"/> shows how the initial ietf-rats-reference-interaction-models.xml"/>
Attestation
keys can be used to certify LDevID and LAK keys. Use of the LDevID and LAK allo
ws the device owner
to use a uniform identity structure across device types from multiple manufactur
ers (in the same way
that an “Asset Tag” is used by many enterprises to identify devices they own).
TCG document
<xref target="Provisioning-TPM-2.0"/> also contains guidance on provisioning Loc
al identity keys in TPM 2.0.
Owners should follow the same practice of binding Local DevID and Local AK as th
e manufacturer would for IDevID and IAK.
See Section <xref target="riv-keying"/>.</t>
<t>Device owners, however, can use any other mechanism they want to assure the
mselves that local identity
certificates are inserted into the intended device, including physical inspectio
n and programming
in a secure location, if they prefer to avoid placing trust in the manufacturer-
provided keys.</t>
</list></t>
<t>Clearly, local keys can’t be used for secure Zero Touch provisioning; install <!-- [I-D.richardson-rats-usecases] IESG state Expired -->
ation of the local keys
can only be done by some process that runs before the device is installed for ne
twork operation,
or using procedures such as those outlined in Bootstrapping Remote Secure Key In
frastructure (BRSKI) <xref target="RFC8995"/>.</t>
<t>On the other end of the device life cycle, provision should be made to wipe l <xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D
ocal keys when a device .richardson-rats-usecases.xml"/>
is decommissioned, to indicate that the device is no longer owned by the enterpr
ise. The manufacturer’s
Initial identity keys must be preserved, as they contain no information that’s n
ot already printed on
the device’s serial number plate.</t>
</section> <!-- [I-D.birkholz-rats-tuda] IESG state I-D Exists -->
<section anchor="other-factors-for-trustworthy-operation" title="Other Factors f
or Trustworthy Operation">
<t>In addition to trustworthy provisioning of keys, RIV depends on a number of o ther factors for trustworthy operation.</t> <xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D .birkholz-rats-tuda.xml"/>
<t><list style="symbols"> <!-- [I-D.birkholz-rats-network-device-subscription] Replaced by [I-D.ietf-rats-
<t>Secure identity depends on mechanisms to prevent per-device secret keys fro network-device-subscription] IESG state I-D Exists -->
m being compromised. The TPM
provides this capability as a Root of Trust for Storage.</t>
<t>Attestation depends on an unbroken chain of measurements, starting from the
very first
measurement. See <xref target="using-tpm"/> for background on TPM practices.</t
>
<t>That first measurement is made by code called the Root of Trust for Measure
ment, typically done by trusted
firmware stored in boot flash. Mechanisms for maintaining the trustworthiness o
f the RTM are out of
scope for RIV, but could include immutable firmware, signed updates, or a vendor
-specific hardware
verification technique. See <xref target="root-of-trust"/> for background on
roots of trust.</t>
<t>The device owner SHOULD provide some level of physical defense for the devi
ce. If a TPM that has already been programmed
with an authentic DevID is stolen and inserted into a counterfeit device, attest
ation of that counterfeit
device may become indistinguishable from an authentic device.</t>
</list></t>
<t>RIV also depends on reliable Reference Values, as expressed by the RIM <xref <xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D
target="RIM"/>. The definition of .ietf-rats-network-device-subscription.xml"/>
trust procedures for RIMs is out of scope for RIV, and the device owner is free
to use any policy to validate
a set of reference measurements. It should also be noted that, while RIV can pr
ovide a reliable indication that a known software package is in use by the devic
e, and that the package has not been tampered, it is the device owner’s responsi
bility to determine that it’s the correct package for the application.</t>
<t>RIMs may be conveyed out-of-band or in-band, as part of the attestation <!-- [I-D.ietf-rats-eat] IESG state I-D Exists -->
process (see <xref target="RIM-policy"/>). But for network devices, where softw
are is usually shipped as a self-contained
package, RIMs signed by the manufacturer and delivered in-band may be more conve
nient for the device owner.</t>
<t>The validity of RIV attestation results is also influenced by procedures used to create Reference Values:</t> <xi:include href="https://datatracker.ietf.org/doc/bibxml3/reference.I-D .ietf-rats-eat.xml"/>
<t><list style="symbols"> <reference anchor="TPM-1.2" target="https://trustedcomputinggroup.org/re
<t>While the RIM itself is signed, supply-chains SHOULD be carefully scrutiniz source/tpm-main-specification/">
ed to ensure that the values are <front>
not subject to unexpected manipulation prior to signing. Insider-attacks agains <title>TPM 1.2 Main Specification</title>
t code bases and build chains <author>
are particularly hard to spot.</t> <organization>Trusted Computing Group</organization>
<t>Designers SHOULD guard against hash collision attacks. Reference Integrity </author>
Manifests often give hashes for large objects <date year="2011" month="March"/>
of indeterminate size; if one of the measured objects can be replaced with an im </front>
plant engineered to produce <refcontent>Level 2, Version 1.2, Revision 116</refcontent>
the same hash, RIV will be unable to detect the substitution. TPM1.2 uses SHA-1 </reference>
hashes only, which have been
shown to be susceptible to collision attack. TPM2.0 will produce quotes with SH
A-256, which so far has resisted
such attacks. Consequently, RIV implementations SHOULD use TPM2.0.</t>
</list></t>
</section> <reference anchor="TPM-2.0" target="https://trustedcomputinggroup.org/re
</section> source/tpm-library-specification/">
<section anchor="IANA" title="IANA Considerations"> <front>
<title>Trusted Platform Module Library</title>
<author>
<organization>Trusted Computing Group</organization>
</author>
<date year="2024" month="March"/>
</front>
<refcontent>Family "2.0", Level 00, Revision 01.83</refcontent>
</reference>
<t>This document has no IANA actions.</t> <reference anchor="PLATFORM-CERTS" target="https://trustedcomputinggroup
.org/resource/tcg-platform-attribute-credential-profile/">
<front>
<title>TCG Platform Attribute Credential Profile</title>
<author>
<organization>Trusted Computing Group</organization>
</author>
<date year="2018" month="January"/>
</front>
<refcontent>Specification Version 1.0, Revision 16</refcontent>
</reference>
</section> <reference anchor="PROV-TPM-2.0" target="https://trustedcomputinggroup.o
<section anchor="conclusion" title="Conclusion"> rg/wp-content/uploads/TCG-TPM-v2.0-Provisioning-Guidance-Published-v1r1.pdf">
<front>
<title>TCG TPM v2.0 Provisioning Guidance</title>
<author>
<organization>Trusted Computing Group</organization>
</author>
<date year="2017" month="March"/>
</front>
<refcontent>Version 1.0, Revision 1.0</refcontent>
</reference>
<t>TCG technologies can play an important part in the implementation of Remote <reference anchor="IEEE-802.1X">
Integrity Verification. Standards for many of the components needed for <front>
implementation of RIV already exist:</t> <title>IEEE Standard for Local and Metropolitan Area Networks - Port
-Based Network Access Control</title>
<author>
<organization>IEEE</organization>
</author>
<date year="2020" month="February"/>
</front>
<seriesInfo name="IEEE Std" value="802.1X-2020"/>
<seriesInfo name="DOI" value="10.1109/IEEESTD.2020.9018454"/>
</reference>
<t><list style="symbols"> <reference anchor="IEEE-802.1AE">
<t>Platform identity can be based on IEEE 802.1AR Device Identity, coupled wit <front>
h <title>IEEE Standard for Local and metropolitan area networks - Medi
careful supply-chain management by the manufacturer.</t> a Access Control (MAC) Security</title>
<t>Complex supply chains can be certified using TCG Platform Certificates <xre <author>
f target="Platform-Certificates"/>.</t> <organization>IEEE</organization>
<t>The TCG TAP mechanism coupled with <xref target="I-D.ietf-rats-yang-tpm-cha </author>
rra"/> can be used to retrieve attestation evidence.</t> <date year="2018"/>
<t>Reference Values must be conveyed from the software authority (e.g., </front>
the manufacturer) in Reference Integrity Manifests, to the system in which verif <seriesInfo name="IEEE Std" value="802.1AE-2018"/>
ication will take place. IETF and TCG <seriesInfo name="DOI" value="10.1109/IEEESTD.2018.8585421" />
SWID and CoSWID work (<xref target="I-D.ietf-sacm-coswid"/>, <xref target="RIM"/ </reference>
>) forms the basis for this function.</t>
</list></t>
</section> <reference anchor="LLDP">
<section anchor="acknowledgements" title="Acknowledgements"> <front>
<title>IEEE Standard for Local and metropolitan area networks - Stat
ion and Media Access Control Connectivity Discovery</title>
<author>
<organization>IEEE</organization>
</author>
<date year="2016" month="March"/>
</front>
<seriesInfo name="IEEE Std" value="802.1AB-2016"/>
<seriesInfo name="DOI" value="10.1109/IEEESTD.2016.7433915"/>
</reference>
<t>The authors wish to thank numerous reviewers for generous assistance, includi <reference anchor="TCG-RT" target="https://trustedcomputinggroup.org/wp-
ng William Bellingrath, Mark Baushke, Ned Smith, content/uploads/TCG_Roots_of_Trust_Specification_v0p20_PUBLIC_REVIEW.pdf">
Henk Birkholz, Tom Laffey, Dave Thaler, Wei Pan, Michael Eckel, Thomas Hardjono, <front>
Bill Sulzen, Willard (Monty) Wiseman, <title>TCG Roots of Trust Specification</title>
Kathleen Moriarty, Nancy Cam-Winget and Shwetha Bhandari</t> <author>
<organization>Trusted Computing Group</organization>
</author>
<date year="2018" month="July"/>
</front>
<refcontent>(Draft), Family "1.0", Level 00, Revision 0.20</refcontent
>
</reference>
</section> <reference anchor="SP800-193" target="https://nvlpubs.nist.gov/nistpubs/
<section anchor="appendix" title="Appendix"> SpecialPublications/NIST.SP.800-193.pdf">
<front>
<title>Platform Firmware Resiliency Guidelines</title>
<author>
<organization>NIST</organization>
</author>
<date year="2018" month="May"/>
</front>
<seriesInfo name="NIST SP" value="800-193"/>
<seriesInfo name="DOI" value="10.6028/NIST.SP.800-193"/>
</reference>
<section anchor="using-tpm" title="Using a TPM for Attestation"> <reference anchor="SP800-155" target="https://csrc.nist.gov/files/pubs/s
p/800/155/ipd/docs/draft-sp800-155_dec2011.pdf">
<front>
<title>BIOS Integrity Measurement Guidelines (Draft)</title>
<author>
<organization>NIST</organization>
</author>
<date year="2011" month="December"/>
</front>
<seriesInfo name="NIST SP" value="800-155 (Draft)"/>
</reference>
<t>The Trusted Platform Module and surrounding ecosystem provide three interlock <reference anchor="NET-EQ" target="https://trustedcomputinggroup.org/res
ing capabilities to enable secure collection ource/tcg-guidance-securing-network-equipment/">
of evidence from a remote device, Platform Configuration Registers (PCRs), a Quo <front>
te mechanism, and a standardized Event Log.</t> <title>TCG Guidance for Securing Network Equipment Using TCG Technol
ogy</title>
<author>
<organization>Trusted Computing Group</organization>
</author>
<date year="2018" month="January"/>
</front>
<refcontent>Version 1.0, Revision 29</refcontent>
</reference>
<t>Each TPM has at least eight and at most twenty-four PCRs (depending on the pr <reference anchor="NIST-IR-8060" target="https://nvlpubs.nist.gov/nistpu
ofile and vendor choices), each one large bs/ir/2016/NIST.IR.8060.pdf">
<front>
<title>Guidelines for the Creation of Interoperable Software Identif
ication (SWID) Tags</title>
<author initials="D" surname="Waltermire" fullname="David Waltermire
"></author>
<author initials="B. A." surname="Cheikes" fullname="Brant A. Cheike
s"></author>
<author initials="L" surname="Feldman" fullname="Larry Feldman"></au
thor>
<author initials="G" surname="Witte" fullname="Greg Witte"></author>
<date year="2016" month="April"/>
</front>
<seriesInfo name="NIST NISTIR" value="8060"/>
<seriesInfo name="DOI" value="10.6028/NIST.IR.8060"/>
</reference>
<reference anchor="AIK-ENROLL" target="https://trustedcomputinggroup.org
/resource/tcg-infrastructure-working-group-a-cmc-profile-for-aik-certificate-enr
ollment/">
<front>
<title>TCG Infrastructure Working Group A CMC Profile for AIK Certif
icate Enrollment</title>
<author>
<organization>Trusted Computing Group</organization>
</author>
<date year="2011" month="March"/>
</front>
<refcontent>Version 1.0, Revision 7</refcontent>
</reference>
<reference anchor="SWID-GEN" target="https://github.com/Labs64/swid-mave
n-plugin">
<front>
<title>SoftWare IDentification (SWID) Tags Generator (Maven Plugin)<
/title>
<author>
<organization>Labs64</organization>
</author>
</front>
</reference>
</references>
</references>
<section anchor="appendix" numbered="true" toc="default">
<name>Supporting Materials</name>
<section anchor="using-tpm" numbered="true" toc="default">
<name>Using a TPM for Attestation</name>
<t>The TPM and surrounding ecosystem provide three interlocking capabili
ties to enable secure collection
of evidence from a remote device: PCRs, a Quote mechanism, and a standardized Ev
ent Log.</t>
<t>Each TPM has at least eight and at most twenty-four PCRs (depending o
n the profile and vendor choices), each one large
enough to hold one hash value (SHA-1, SHA-256, and other hash algorithms can enough to hold one hash value (SHA-1, SHA-256, and other hash algorithms can
be used, depending on TPM version). PCRs can’t be accessed directly from outsid be used, depending on TPM version). PCRs can't be accessed directly from outsid
e the chip, but the TPM e the chip, but the TPM
interface provides a way to “extend” a new security measurement hash into any PC interface provides a way to "extend" a new security measurement hash into any PC
R, a process by which the existing value R, a process by which the existing value
in the PCR is hashed with the new security measurement hash, and the result plac ed back into the same PCR. The result in the PCR is hashed with the new security measurement hash, and the result plac ed back into the same PCR. The result
is a composite fingerprint comprising the hash of all the security measurements extended into each PCR since the system was reset.</t> is a composite fingerprint comprising the hash of all the security measurements extended into each PCR since the system was reset.</t>
<t>Every time a PCR is extended, an entry should be added to the corresp
<t>Every time a PCR is extended, an entry should be added to the corresponding E onding Event Log. Logs contain the security
vent Log. Logs contain the security
measurement hash plus informative fields offering hints as to which event genera ted the security measurement. measurement hash plus informative fields offering hints as to which event genera ted the security measurement.
The Event Log itself is protected against accidental manipulation, but it is imp The Event Log itself is protected against accidental manipulation, but it is imp
licitly tamper-evident – any licitly tamper-evident: Any
verification process can read the security measurement hash from the log events, verification process can read the security measurement hash from the log events,
compute the composite value compute the composite value,
and compare that to what ended up in the PCR. If there’s no discrepancy, the l and compare that to what is in the PCR. If there's no discrepancy, the logs do
ogs do provide an accurate provide an accurate
view of what was placed into the PCR.</t> view of what was placed into the PCR.</t>
<t>Note that the composite hash-of-hashes recorded in PCRs is order-depe
<t>Note that the composite hash-of-hashes recorded in PCRs is order-dependent, r ndent, resulting in different PCR values for different
esulting in different PCR values for different ordering of the same set of events (e.g., Event A followed by Event B yields a d
ordering of the same set of events (e.g. Event A followed by Event B yields a di ifferent PCR value than B followed by A).
fferent PCR value than B followed by A).
For single-threaded code, where both the events and their order are fixed, a Ver ifier may validate a single PCR value, and use the log only to diagnose a mismat ch from Reference Values. However, operating system code is usually For single-threaded code, where both the events and their order are fixed, a Ver ifier may validate a single PCR value, and use the log only to diagnose a mismat ch from Reference Values. However, operating system code is usually
non-deterministic, meaning that there may never be a single “known good” PCR val ue. In this case, the Verifier may have nondeterministic, meaning that there may never be a single "known good" PCR valu e. In this case, the Verifier may have
to verify that the log is correct, and then analyze each item in the log to dete rmine if it represents an authorized event.</t> to verify that the log is correct, and then analyze each item in the log to dete rmine if it represents an authorized event.</t>
<t>In a conventional TPM Attestation environment, the first measurement
<t>In a conventional TPM Attestation environment, the first measurement must be must be made and extended into the TPM by trusted
made and extended into the TPM by trusted device code (called the RTM). That first measurement should cover the segment o
device code (called the Root of Trust for Measurement, RTM). That first measure f
ment should cover the segment of
code that is run immediately after the RTM, which then measures the next code se gment before running it, and so on, code that is run immediately after the RTM, which then measures the next code se gment before running it, and so on,
forming an unbroken chain of trust. See <xref target="TCGRoT"/> for more on Mut forming an unbroken chain of trust. See <xref target="TCG-RT" format="default"/
able vs Immutable roots of trust.</t> > for more on Mutable vs. Immutable Roots of Trust.</t>
<t>The TPM provides another mechanism called a Quote that can read the c
<t>The TPM provides another mechanism called a Quote that can read the current v urrent value of the PCRs and package them,
alue of the PCRs and package them, along with the Verifier's nonce, into a TPM-specific data structure signed by an
along with the Verifier’s nonce, into a TPM-specific data structure signed by an Attestation private key, known
Attestation private key, known
only to the TPM.</t> only to the TPM.</t>
<t>It's important to note that the Quote data structure is signed inside
<t>As noted above in <xref target="security-cons"/> Security Considerations, it’ the TPM (see <xref target="security-cons" format="default"/>, Security Consider
s important to note that the Quote data structure is signed inside the TPM. The ations). The trust model is preserved by retrieving the Quote in a way that doe
trust model is preserved by retrieving the Quote in a way that does not invalid s not invalidate the signature,
ate the signature, as specified in <xref target="RFC9684" format="default"/>. The structure of the
as specified in <xref target="I-D.ietf-rats-yang-tpm-charra"/>. The structure o command and response for a quote, including its signature, as generated by the
f the command and response for a quote, including its signature, as generated by TPM, can be seen in Part 3, Section 16.5, of <xref target="TPM-1.2" format="defa
the TPM, can be seen in <xref target="TPM1.2"></xref> Part 3, Section 16.5, and ult"/> and Section 18.4.2 of <xref target="TPM-2.0" format="default"/>.</t>
<xref target="TPM2.0"></xref> Section 18.4.2.</t> <t>The Verifier uses the Quote and Log together. The Quote contains the
composite hash of the complete sequence
<t>The Verifier uses the Quote and Log together. The Quote contains the composi of security measurement hashes, signed by the TPM's private AK. The Log contain
te hash of the complete sequence s a record of each
of security measurement hashes, signed by the TPM’s private Attestation Key. Th measurement extended into the TPM's PCRs. By computing the composite hash of al
e Log contains a record of each l the measurements, the Verifier
measurement extended into the TPM’s PCRs. By computing the composite hash of al
l the measurements, the Verifier
can verify the integrity of the Event Log, even though the Event Log itself is n ot signed. Each hash in the validated can verify the integrity of the Event Log, even though the Event Log itself is n ot signed. Each hash in the validated
Event Log can then be compared to corresponding expected values in the set of Re ference Values to Event Log can then be compared to corresponding expected values in the set of Re ference Values to
validate overall system integrity.</t> validate overall system integrity.</t>
<t>A summary of information exchanged in obtaining quotes from TPM 1.2 a
<t>A summary of information exchanged in obtaining quotes from TPM1.2 and TPM2.0 nd TPM 2.0 can be found in <xref target="TAP" format="default"/>, Section 4.
can be found in <xref target="TAP"/>, Section 4. Detailed information about PCRs and Quote data structures can be found in <xref
Detailed information about PCRs and Quote data structures can be found in <xref target="TPM-1.2" format="default"/>, <xref target="TPM-2.0" format="default"/>.
target="TPM1.2"/>, <xref target="TPM2.0"/>. Recommended log Recommended log
formats include <xref target="PC-Client-BIOS-TPM-2.0"/>, and <xref target="Canon formats include <xref target="PC-CLIENT-BIOS-TPM-2.0" format="default"/>, and <x
ical-Event-Log"/>.</t> ref target="CEL" format="default"/>.</t>
</section>
</section> <section anchor="root-of-trust" numbered="true" toc="default">
<section anchor="root-of-trust" title="Root of Trust for Measurement"> <name>Root of Trust for Measurement (RTM)</name>
<t>The measurements needed for attestation require that the device being
<t>The measurements needed for attestation require that the device being atteste attested
d is equipped with an RTM, that is, some trustworthy
is equipped with a Root of Trust for Measurement, that is, some trustworthy
mechanism that can compute the first measurement in the chain of trust required mechanism that can compute the first measurement in the chain of trust required
to attest that each stage of system startup is verified, a Root of Trust for Sto rage (i.e., to attest that each stage of system startup is verified, a Root of Trust for Sto rage (i.e.,
the TPM PCRs) to record the results, and a Root of Trust the TPM PCRs) to record the results, and a Root of Trust
for Reporting to report the results.</t> for Reporting to report the results.</t>
<t>While there are many complex aspects of Roots of Trust (<xref target= "TCG-RT" format="default"/> <xref target="SP800-155" format="default"/> <xref ta rget="SP800-193" format="default"/>), two aspects that
<t>While there are many complex aspects of Roots of Trust ( <xref target="TCGRoT "/>, <xref target="SP800-155"/>, <xref target="SP800-193"/>), two aspects that
are important in the case of attestation are:</t> are important in the case of attestation are:</t>
<ul spacing="normal">
<t><list style="symbols"> <li>The first measurement computed by the RTM and stored
<t>The first measurement computed by the Root of Trust for Measurement, and st in the TPM's Root of Trust for Storage must be assumed to be correct.</li>
ored <li>There must not be a way to reset the Root of Trust for Storage wit
in the TPM’s Root of Trust for Storage, must be assumed to be correct.</t> hout re-entering
<t>There must not be a way to reset the Root of Trust for Storage without re-e the RTM code.</li>
ntering </ul>
the Root of Trust for Measurement code.</t> <t>The first measurement must be computed by code that is implicitly tru
</list></t> sted; if that
<t>The first measurement must be computed by code that is implicitly trusted; if
that
first measurement can be subverted, none of the remaining measurements can first measurement can be subverted, none of the remaining measurements can
be trusted. (See <xref target="SP800-155"/>)</t> be trusted. (See <xref target="SP800-155" format="default"/>.)</t>
<t>It's important to note that the trustworthiness of the RTM code canno
<t>It’s important to note that the trustworthiness of the RTM code cannot be ass t be assured by
ured by the TPM or TPM supplier -- code or procedures external to the TPM must guarantee
the TPM or TPM supplier – code or procedures external to the TPM must guarantee the
the
security of the RTM.</t> security of the RTM.</t>
</section>
</section> <section anchor="layering-model-for-network-equipment-attester-and-verifie
<section anchor="layering-model-for-network-equipment-attester-and-verifier" tit r" numbered="true" toc="default">
le="Layering Model for Network Equipment Attester and Verifier"> <name>Layering Model for Network Equipment Attester and Verifier</name>
<t>Retrieval of identity and attestation state uses one protocol stack,
<t>Retrieval of identity and attestation state uses one protocol stack, while while
retrieval of Reference Values uses a different set of protocols. Figure retrieval of Reference Values uses a different set of protocols.
5 shows the components involved.</t> <xref target="RIV-Protocol-Stacks" format="default"/> shows the components invol
ved.</t>
<figure title="RIV Protocol Stacks" anchor="RIV-Protocol-Stacks"><artwork align= <figure anchor="RIV-Protocol-Stacks">
"left"><![CDATA[ <name>RIV Protocol Stacks</name>
<artwork align="left" name="" type="" alt=""><![CDATA[
+-----------------------+ +-------------------------+ +-----------------------+ +-------------------------+
| | | | | | | |
| Attester |<-------------| Verifier | | Attester |<-------------| Verifier |
| (Device) |------------->| (Management Station) | | (Device) |------------->| (Management Station) |
| | | | | | | | | |
+-----------------------+ | +-------------------------+ +-----------------------+ | +-------------------------+
| |
-------------------- -------------------- -------------------- --------------------
| | | |
------------------------------- --------------------------------- ------------------------------- ---------------------------------
|Reference Values | | Attestation | | Reference Values | | Attestation |
------------------------------- --------------------------------- ------------------------------- ---------------------------------
******************************************************************** ********************************************************************
* IETF Attestation Reference Interaction Diagram * * IETF Remote Attestation Conceptual Data Flow *
* RFC9334, Figure 1 *
******************************************************************** ********************************************************************
......................... ......................... ......................... .........................
. Reference Integrity . . TAP (PTS2.0) Info . . Reference Integrity . . TAP Info .
. Manifest . . Model and Canonical . . Manifest . . Model and Canonical .
. . . Log Format . . . . Log Format .
......................... ......................... ......................... .........................
************************* ************************* ************************* *************************
* YANG SWID Module * * YANG Attestation * * YANG SWID Module * * YANG Attestation *
* I-D.ietf-sacm-coswid * * Module * * RFC9393 * * Module *
* * * I-D.ietf-rats- * * * * RFC9684 *
* * * yang-tpm-charra * * * * *
************************* ************************* ************************* *************************
************************* ************************* ************************* *************************
* XML, JSON, CBOR (etc) * * XML, JSON, CBOR (etc) * * XML, JSON, CBOR, etc. * * XML, JSON, CBOR, etc. *
************************* ************************* ************************* *************************
************************* ************************* ************************* *************************
* RESTCONF/NETCONF * * RESTCONF/NETCONF * * RESTCONF/NETCONF * * RESTCONF/NETCONF *
************************* ************************* ************************* *************************
************************* ************************* ************************* *************************
* TLS, SSH * * TLS, SSH * * TLS, SSH * * TLS, SSH *
************************* ************************* ************************* *************************
]]></artwork>
]]></artwork></figure> </figure>
<t>IETF documents are captured in boxes surrounded by asterisks. TCG doc
<t>IETF documents are captured in boxes surrounded by asterisks. TCG documents uments
are shown in boxes surrounded by dots.</t> are shown in boxes surrounded by dots.</t>
</section>
</section> <section anchor="implementation-notes" numbered="true" toc="default">
<section anchor="implementation-notes" title="Implementation Notes"> <name>Implementation Notes</name>
<t><xref target="Component-Status" format="default"/> summarizes many of
<t><xref target="Component-Status"/> summarizes many of the actions needed to co the actions needed to complete an Attestation
mplete an Attestation
system, with links to relevant documents. While documents are controlled system, with links to relevant documents. While documents are controlled
by several standards organizations, the implied actions required for by several standards organizations, the implied actions required for
implementation are all the responsibility of the manufacturer of the device, implementation are all the responsibility of the manufacturer of the device,
unless otherwise noted.</t> unless otherwise noted.</t>
<t>As noted, SWID tags can be generated many ways, but one possible tool is <xref target="SWID-GEN" format="default"/>.</t>
<t>As noted, SWID tags can be generated many ways, but one possible tool is <xre <!-- [rfced] Appendix A.4, Table 2.
f target="SWID-Gen"></xref></t>
<figure title="Component Status" anchor="Component-Status"><artwork align="left"
><![CDATA[
+------------------------------------------------------------------+
| Component | Controlling |
| | Specification |
| Make a Secure execution environment | TCG RoT |
| o Attestation depends on a secure root of | UEFI.org |
| trust for measurement outside the TPM, as | |
| well as roots for storage and reporting | |
| inside the TPM. | |
| o Refer to TCG Root of Trust for Measurement.| |
| o NIST SP 800-193 also provides guidelines | |
| on Roots of Trust | |
| Provision the TPM as described in |[Platform-DevID-TPM-2.0]|
| TCG documents. | TCG Platform |
| | Certificate |
| Put a DevID or Platform Cert in the TPM | TCG TPM DevID |
| o Install an Initial Attestation Key at the | TCG Platform |
| same time so that Attestation can work out | Certificate |
| of the box |-----------------
| o Equipment suppliers and owners may want to | IEEE 802.1AR |
| implement Local Device ID as well as | |
| Initial Device ID | |
| Connect the TPM to the TLS stack | Vendor TLS |
| o Use the DevID in the TPM to authenticate | stack (This |
| TAP connections, identifying the device | action is |
| | configuring TLS|
| | to use the DevID |
| | as its client |
| | certificate) |
| Make CoSWID tags for BIOS/Loader/Kernel objects | IETF CoSWID |
| o Add reference measurements into SWID tags | ISO/IEC 19770-2|
| o Manufacturer should sign the SWID tags | NIST IR 8060 |
| o The TCG RIM-IM identifies further | |
| procedures to create signed RIM | |
| documents that provide the necessary | |
| reference information | |
| Package the SWID tags with a vendor software | Retrieve tags |
| release | with |
| o A tag-generator plugin such | I-D.ietf-sacm-coswid|
| as [SWID-Gen] can be used |----------------|
| | TCG PC Client |
| | RIM |
| Use PC Client measurement definitions | TCG PC Client |
| to define the use of PCRs | BIOS |
| (although Windows OS is rare on Networking | |
| Equipment, UEFI BIOS is not) | |
| Use TAP to retrieve measurements | |
| o Map to YANG | YANG Module for|
| Use Canonical Log Format | Basic |
| | Attestation |
| | TCG Canonical |
| | Log Format |
| Posture Collection Server (as described in IETF | |
| SACMs ECP) should request the | |
| attestation and analyze the result | |
| The Management application might be broken down | |
| to several more components: | |
| o A Posture Manager Server | |
| which collects reports and stores them in | |
| a database | |
| o One or more Analyzers that can look at the| |
| results and figure out what it means. | |
]]></artwork></figure>
</section>
</section>
</middle>
<back>
<references title='Normative References'>
<reference anchor='RFC2119' target='https://www.rfc-editor.org/info/rfc2119'>
<front>
<title>Key words for use in RFCs to Indicate Requirement Levels</title>
<author fullname='S. Bradner' initials='S.' surname='Bradner'><organization/></a
uthor>
<date month='March' year='1997'/>
<abstract><t>In many standards track documents several words are used to signify
the requirements in the specification. These words are often capitalized. This
document defines these words as they should be interpreted in IETF documents.
This document specifies an Internet Best Current Practices for the Internet Comm
unity, and requests discussion and suggestions for improvements.</t></abstract>
</front>
<seriesInfo name='BCP' value='14'/>
<seriesInfo name='RFC' value='2119'/>
<seriesInfo name='DOI' value='10.17487/RFC2119'/>
</reference>
<reference anchor='RFC8446' target='https://www.rfc-editor.org/info/rfc8446'>
<front>
<title>The Transport Layer Security (TLS) Protocol Version 1.3</title>
<author fullname='E. Rescorla' initials='E.' surname='Rescorla'><organization/><
/author>
<date month='August' year='2018'/>
<abstract><t>This document specifies version 1.3 of the Transport Layer Security
(TLS) protocol. TLS allows client/server applications to communicate over the
Internet in a way that is designed to prevent eavesdropping, tampering, and mess
age forgery.</t><t>This document updates RFCs 5705 and 6066, and obsoletes RFCs
5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2
implementations.</t></abstract>
</front>
<seriesInfo name='RFC' value='8446'/>
<seriesInfo name='DOI' value='10.17487/RFC8446'/>
</reference>
<reference anchor='RFC4253' target='https://www.rfc-editor.org/info/rfc4253'>
<front>
<title>The Secure Shell (SSH) Transport Layer Protocol</title>
<author fullname='T. Ylonen' initials='T.' surname='Ylonen'><organization/></aut
hor>
<author fullname='C. Lonvick' initials='C.' role='editor' surname='Lonvick'><org
anization/></author>
<date month='January' year='2006'/>
<abstract><t>The Secure Shell (SSH) is a protocol for secure remote login and ot
her secure network services over an insecure network.</t><t>This document descri
bes the SSH transport layer protocol, which typically runs on top of TCP/IP. Th
e protocol can be used as a basis for a number of secure network services. It p
rovides strong encryption, server authentication, and integrity protection. It
may also provide compression.</t><t>Key exchange method, public key algorithm, s
ymmetric encryption algorithm, message authentication algorithm, and hash algori
thm are all negotiated.</t><t>This document also describes the Diffie-Hellman ke
y exchange method and the minimal set of algorithms that are needed to implement
the SSH transport layer protocol. [STANDARDS-TRACK]</t></abstract>
</front>
<seriesInfo name='RFC' value='4253'/>
<seriesInfo name='DOI' value='10.17487/RFC4253'/>
</reference>
<reference anchor='RFC6241' target='https://www.rfc-editor.org/info/rfc6241'>
<front>
<title>Network Configuration Protocol (NETCONF)</title>
<author fullname='R. Enns' initials='R.' role='editor' surname='Enns'><organizat
ion/></author>
<author fullname='M. Bjorklund' initials='M.' role='editor' surname='Bjorklund'>
<organization/></author>
<author fullname='J. Schoenwaelder' initials='J.' role='editor' surname='Schoenw
aelder'><organization/></author>
<author fullname='A. Bierman' initials='A.' role='editor' surname='Bierman'><org
anization/></author>
<date month='June' year='2011'/>
<abstract><t>The Network Configuration Protocol (NETCONF) defined in this docume
nt provides mechanisms to install, manipulate, and delete the configuration of n
etwork devices. It uses an Extensible Markup Language (XML)-based data encoding
for the configuration data as well as the protocol messages. The NETCONF proto
col operations are realized as remote procedure calls (RPCs). This document obs
oletes RFC 4741. [STANDARDS-TRACK]</t></abstract>
</front>
<seriesInfo name='RFC' value='6241'/>
<seriesInfo name='DOI' value='10.17487/RFC6241'/>
</reference>
<reference anchor='RFC8174' target='https://www.rfc-editor.org/info/rfc8174'>
<front>
<title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</title>
<author fullname='B. Leiba' initials='B.' surname='Leiba'><organization/></autho
r>
<date month='May' year='2017'/>
<abstract><t>RFC 2119 specifies common key words that may be used in protocol s
pecifications. This document aims to reduce the ambiguity by clarifying that on
ly UPPERCASE usage of the key words have the defined special meanings.</t></abs
tract>
</front>
<seriesInfo name='BCP' value='14'/>
<seriesInfo name='RFC' value='8174'/>
<seriesInfo name='DOI' value='10.17487/RFC8174'/>
</reference>
<reference anchor='RFC5280' target='https://www.rfc-editor.org/info/rfc5280'>
<front>
<title>Internet X.509 Public Key Infrastructure Certificate and Certificate Revo
cation List (CRL) Profile</title>
<author fullname='D. Cooper' initials='D.' surname='Cooper'><organization/></aut
hor>
<author fullname='S. Santesson' initials='S.' surname='Santesson'><organization/
></author>
<author fullname='S. Farrell' initials='S.' surname='Farrell'><organization/></a
uthor>
<author fullname='S. Boeyen' initials='S.' surname='Boeyen'><organization/></aut
hor>
<author fullname='R. Housley' initials='R.' surname='Housley'><organization/></a
uthor>
<author fullname='W. Polk' initials='W.' surname='Polk'><organization/></author>
<date month='May' year='2008'/>
<abstract><t>This memo profiles the X.509 v3 certificate and X.509 v2 certificat
e revocation list (CRL) for use in the Internet. An overview of this approach a
nd model is provided as an introduction. The X.509 v3 certificate format is des
cribed in detail, with additional information regarding the format and semantics
of Internet name forms. Standard certificate extensions are described and two
Internet-specific extensions are defined. A set of required certificate extensi
ons is specified. The X.509 v2 CRL format is described in detail along with sta
ndard and Internet-specific extensions. An algorithm for X.509 certification pa
th validation is described. An ASN.1 module and examples are provided in the ap
pendices. [STANDARDS-TRACK]</t></abstract>
</front>
<seriesInfo name='RFC' value='5280'/>
<seriesInfo name='DOI' value='10.17487/RFC5280'/>
</reference>
<reference anchor='I-D.ietf-rats-yang-tpm-charra'>
<front>
<title>A YANG Data Model for Challenge-Response-based Remote Attestation P
rocedures using TPMs</title>
<author fullname='Henk Birkholz'>
<organization>Fraunhofer SIT</organization>
</author>
<author fullname='Michael Eckel'>
<organization>Fraunhofer SIT</organization>
</author>
<author fullname='Shwetha Bhandari'>
<organization>ThoughtSpot</organization>
</author>
<author fullname='Eric Voit'>
<organization>Cisco Systems</organization>
</author>
<author fullname='Bill Sulzen'>
<organization>Cisco Systems</organization>
</author>
<author fullname='Liang Xia (Frank)'>
<organization>Huawei Technologies</organization>
</author>
<author fullname='Tom Laffey'>
<organization>Hewlett Packard Enterprise</organization>
</author>
<author fullname='Guy C. Fedorkow'>
<organization>Juniper Networks</organization>
</author>
<date day='20' month='March' year='2022'/>
<abstract>
<t> This document defines YANG RPCs and a few configuration nodes
required to retrieve attestation evidence about integrity
measurements from a device, following the operational context defined
in TPM-based Network Device Remote Integrity Verification.
Complementary measurement logs are also provided by the YANG RPCs,
originating from one or more roots of trust for measurement (RTMs).
The module defined requires at least one TPM 1.2 or TPM 2.0 as well
as a corresponding TPM Software Stack (TSS), or equivalent hardware
implementations that include the protected capabilities as provided
by TPMs as well as a corresponding software stack, included in the
device components of the composite device the YANG server is running
on.
</t>
</abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-ietf-rats-yang-tpm-charra-18'/
>
<format target='https://www.ietf.org/archive/id/draft-ietf-rats-yang-tpm-char
ra-18.txt' type='TXT'/>
</reference>
<reference anchor='I-D.ietf-sacm-coswid'>
<front>
<title>Concise Software Identification Tags</title>
<author fullname='Henk Birkholz'>
<organization>Fraunhofer SIT</organization>
</author>
<author fullname='Jessica Fitzgerald-McKay'>
<organization>National Security Agency</organization>
</author>
<author fullname='Charles Schmidt'>
<organization>The MITRE Corporation</organization>
</author>
<author fullname='David Waltermire'>
<organization>National Institute of Standards and Technology</organizati
on>
</author>
<date day='7' month='March' year='2022'/>
<abstract>
<t> ISO/IEC 19770-2:2015 Software Identification (SWID) tags provide a
n
extensible XML-based structure to identify and describe individual
software components, patches, and installation bundles. SWID tag
representations can be too large for devices with network and storage
constraints. This document defines a concise representation of SWID
tags: Concise SWID (CoSWID) tags. CoSWID supports a similar set of
semantics and features as SWID tags, as well as new semantics that
allow CoSWIDs to describe additional types of information, all in a
more memory efficient format.
</t>
</abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-ietf-sacm-coswid-21'/>
<format target='https://www.ietf.org/archive/id/draft-ietf-sacm-coswid-21.txt
' type='TXT'/>
</reference>
<reference anchor='I-D.ietf-rats-architecture'>
<front>
<title>Remote Attestation Procedures Architecture</title>
<author fullname='Henk Birkholz'>
<organization>Fraunhofer SIT</organization>
</author>
<author fullname='Dave Thaler'>
<organization>Microsoft</organization>
</author>
<author fullname='Michael Richardson'>
<organization>Sandelman Software Works</organization>
</author>
<author fullname='Ned Smith'>
<organization>Intel Corporation</organization>
</author>
<author fullname='Wei Pan'>
<organization>Huawei Technologies</organization>
</author>
<date day='8' month='February' year='2022'/>
<abstract>
<t> In network protocol exchanges it is often useful for one end of a
communication to know whether the other end is in an intended
operating state. This document provides an architectural overview of
the entities involved that make such tests possible through the
process of generating, conveying, and evaluating evidentiary claims.
An attempt is made to provide for a model that is neutral toward
processor architectures, the content of claims, and protocols.
</t>
</abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-ietf-rats-architecture-15'/>
<format target='https://www.ietf.org/archive/id/draft-ietf-rats-architecture-
15.txt' type='TXT'/>
</reference>
<reference anchor="IEEE-802-1AR" >
<front>
<title>802.1AR-2018 - IEEE Standard for Local and Metropolitan Area Networks
- Secure Device Identity, IEEE Computer Society</title>
<author initials="M." surname="Seaman">
<organization>IEEE Computer Society</organization>
</author>
<date year="2018" month="August"/>
</front>
</reference>
<reference anchor="TAP" target="https://trustedcomputinggroup.org/resource/tcg-t
ap-information-model/">
<front>
<title>TCG Trusted Attestation Protocol (TAP) Information Model for TPM Fami
lies 1.2 and 2.0 and DICE Family 1.0, Version 1.0, Revision 0.36</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2018" month="October"/>
</front>
</reference>
<reference anchor="Canonical-Event-Log" target="https://trustedcomputinggroup.or
g/resource/canonical-event-log-format/">
<front>
<title>Canonical Event Log Format Version 1.0 Revision .41, February 25, 202
2</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2020" month="December"/>
</front>
</reference>
<reference anchor="PC-Client-BIOS-TPM-2.0" target="https://trustedcomputinggroup
.org/resource/pc-client-specific-platform-firmware-profile-specification/">
<front>
<title>PC Client Specific Platform Firmware Profile Specification Family "2.
0", Level 00 Revision 1.05 Revision 23, May 7, 2021</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2021" month="May"/>
</front>
</reference>
<reference anchor="PC-Client-EFI-TPM-1.2" target="https://trustedcomputinggroup.
org/resource/tcg-efi-platform-specification/">
<front>
<title>TCG EFI Platform Specification for TPM Family 1.1 or 1.2, Specificati
on Version 1.22, Revision 15</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2014" month="January"/>
</front>
</reference>
<reference anchor="RIM" target="https://trustedcomputinggroup.org/resource/tcg-r
eference-integrity-manifest-rim-information-model/">
<front>
<title>TCG Reference Integrity Manifest (RIM) Information Model, v1.0, Revis
ion 0.16, Nov 12, 2020</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2019" month="June"/>
</front>
</reference>
<reference anchor="PC-Client-RIM" target="https://trustedcomputinggroup.org/reso
urce/tcg-pc-client-reference-integrity-manifest-specification/">
<front>
<title>TCG PC Client Reference Integrity Manifest Specification, v1.04, Nov
4, 2020</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2019" month="December"/>
</front>
</reference>
<reference anchor="Platform-DevID-TPM-2.0" target="https://trustedcomputinggroup
.org/resource/tpm-2-0-keys-for-device-identity-and-attestation/">
<front>
<title>TPM 2.0 Keys for Device Identity and Attestation, Specification Versi
on 1.0, Revision 2</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2020" month="September"/>
</front>
</reference>
<reference anchor="Platform-ID-TPM-1.2" target="https://trustedcomputinggroup.or
g/resource/tpm-keys-for-platform-identity-for-tpm-1-2-2/">
<front>
<title>TPM Keys for Platform Identity for TPM 1.2, Specification Version 1.0
, Revision 3</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2015" month="August"/>
</front>
</reference>
<reference anchor="SWID" target="https://www.iso.org/standard/65666.html">
<front>
<title>Information Technology Software Asset Management Part 2: Software Ide
ntification Tag, ISO/IEC 19770-2</title>
<author >
<organization>The International Organization for Standardization/Internati
onal Electrotechnical Commission</organization>
</author>
<date year="2015" month="October"/>
</front>
</reference>
<reference anchor="IMA" target="https://sourceforge.net/p/linux-ima/wiki/Home/">
<front>
<title>Integrity Measurement Architecture</title>
<author surname="dsafford">
<organization>dsafford</organization>
</author>
<author surname="kds_etu">
<organization>kds_etu</organization>
</author>
<author surname="mzohar">
<organization>mzohar</organization>
</author>
<author surname="reinersailer">
<organization>reinersailer</organization>
</author>
<author surname="serge_hallyn">
<organization>serge_hallyn</organization>
</author>
<date year="2019" month="June"/>
</front>
</reference>
</references>
<references title='Informative References'>
<reference anchor='RFC6813' target='https://www.rfc-editor.org/info/rfc6813'>
<front>
<title>The Network Endpoint Assessment (NEA) Asokan Attack Analysis</title>
<author fullname='J. Salowey' initials='J.' surname='Salowey'><organization/></a
uthor>
<author fullname='S. Hanna' initials='S.' surname='Hanna'><organization/></autho
r>
<date month='December' year='2012'/>
<abstract><t>The Network Endpoint Assessment (NEA) protocols are subject to a su
btle forwarding attack that has become known as the NEA Asokan Attack. This docu
ment describes the attack and countermeasures that may be mounted. This documen
t is not an Internet Standards Track specification; it is published for informat
ional purposes.</t></abstract>
</front>
<seriesInfo name='RFC' value='6813'/>
<seriesInfo name='DOI' value='10.17487/RFC6813'/>
</reference>
<reference anchor='RFC3748' target='https://www.rfc-editor.org/info/rfc3748'>
<front>
<title>Extensible Authentication Protocol (EAP)</title>
<author fullname='B. Aboba' initials='B.' surname='Aboba'><organization/></autho
r>
<author fullname='L. Blunk' initials='L.' surname='Blunk'><organization/></autho
r>
<author fullname='J. Vollbrecht' initials='J.' surname='Vollbrecht'><organizatio
n/></author>
<author fullname='J. Carlson' initials='J.' surname='Carlson'><organization/></a
uthor>
<author fullname='H. Levkowetz' initials='H.' role='editor' surname='Levkowetz'>
<organization/></author>
<date month='June' year='2004'/>
<abstract><t>This document defines the Extensible Authentication Protocol (EAP),
an authentication framework which supports multiple authentication methods. EA
P typically runs directly over data link layers such as Point-to-Point Protocol
(PPP) or IEEE 802, without requiring IP. EAP provides its own support for dupli
cate elimination and retransmission, but is reliant on lower layer ordering guar
antees. Fragmentation is not supported within EAP itself; however, individual E
AP methods may support this. This document obsoletes RFC 2284. A summary of th
e changes between this document and RFC 2284 is available in Appendix A. [STAND
ARDS-TRACK]</t></abstract>
</front>
<seriesInfo name='RFC' value='3748'/>
<seriesInfo name='DOI' value='10.17487/RFC3748'/>
</reference>
<reference anchor='RFC6125' target='https://www.rfc-editor.org/info/rfc6125'>
<front>
<title>Representation and Verification of Domain-Based Application Service Ident
ity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in
the Context of Transport Layer Security (TLS)</title>
<author fullname='P. Saint-Andre' initials='P.' surname='Saint-Andre'><organizat
ion/></author>
<author fullname='J. Hodges' initials='J.' surname='Hodges'><organization/></aut
hor>
<date month='March' year='2011'/>
<abstract><t>Many application technologies enable secure communication between t
wo entities by means of Internet Public Key Infrastructure Using X.509 (PKIX) ce
rtificates in the context of Transport Layer Security (TLS). This document speci
fies procedures for representing and verifying the identity of application servi
ces in such interactions. [STANDARDS-TRACK]</t></abstract>
</front>
<seriesInfo name='RFC' value='6125'/>
<seriesInfo name='DOI' value='10.17487/RFC6125'/>
</reference>
<reference anchor='RFC8995' target='https://www.rfc-editor.org/info/rfc8995'>
<front>
<title>Bootstrapping Remote Secure Key Infrastructure (BRSKI)</title>
<author fullname='M. Pritikin' initials='M.' surname='Pritikin'><organization/><
/author>
<author fullname='M. Richardson' initials='M.' surname='Richardson'><organizatio
n/></author>
<author fullname='T. Eckert' initials='T.' surname='Eckert'><organization/></aut
hor>
<author fullname='M. Behringer' initials='M.' surname='Behringer'><organization/
></author>
<author fullname='K. Watsen' initials='K.' surname='Watsen'><organization/></aut
hor>
<date month='May' year='2021'/>
<abstract><t>This document specifies automated bootstrapping of an Autonomic Con
trol Plane. To do this, a Secure Key Infrastructure is bootstrapped. This is d
one using manufacturer-installed X.509 certificates, in combination with a manuf
acturer's authorizing service, both online and offline. We call this process th
e Bootstrapping Remote Secure Key Infrastructure (BRSKI) protocol. Bootstrapping
a new device can occur when using a routable address and a cloud service, only
link-local connectivity, or limited/disconnected networks. Support for deploymen
t models with less stringent security requirements is included. Bootstrapping is
complete when the cryptographic identity of the new key infrastructure is succe
ssfully deployed to the device. The established secure connection can be used t
o deploy a locally issued certificate to the device as well.</t></abstract>
</front>
<seriesInfo name='RFC' value='8995'/>
<seriesInfo name='DOI' value='10.17487/RFC8995'/>
</reference>
<reference anchor='RFC7950' target='https://www.rfc-editor.org/info/rfc7950'>
<front>
<title>The YANG 1.1 Data Modeling Language</title>
<author fullname='M. Bjorklund' initials='M.' role='editor' surname='Bjorklund'>
<organization/></author>
<date month='August' year='2016'/>
<abstract><t>YANG is a data modeling language used to model configuration data,
state data, Remote Procedure Calls, and notifications for network management pro
tocols. This document describes the syntax and semantics of version 1.1 of the
YANG language. YANG version 1.1 is a maintenance release of the YANG language,
addressing ambiguities and defects in the original specification. There are a s
mall number of backward incompatibilities from YANG version 1. This document al
so specifies the YANG mappings to the Network Configuration Protocol (NETCONF).<
/t></abstract>
</front>
<seriesInfo name='RFC' value='7950'/>
<seriesInfo name='DOI' value='10.17487/RFC7950'/>
</reference>
<reference anchor='RFC8572' target='https://www.rfc-editor.org/info/rfc8572'>
<front>
<title>Secure Zero Touch Provisioning (SZTP)</title>
<author fullname='K. Watsen' initials='K.' surname='Watsen'><organization/></aut
hor>
<author fullname='I. Farrer' initials='I.' surname='Farrer'><organization/></aut
hor>
<author fullname='M. Abrahamsson' initials='M.' surname='Abrahamsson'><organizat
ion/></author>
<date month='April' year='2019'/>
<abstract><t>This document presents a technique to securely provision a networki
ng device when it is booting in a factory-default state. Variations in the solu
tion enable it to be used on both public and private networks. The provisioning
steps are able to update the boot image, commit an initial configuration, and e
xecute arbitrary scripts to address auxiliary needs. The updated device is subs
equently able to establish secure connections with other systems. For instance,
a device may establish NETCONF (RFC 6241) and/or RESTCONF (RFC 8040) connection
s with deployment-specific network management systems.</t></abstract>
</front>
<seriesInfo name='RFC' value='8572'/>
<seriesInfo name='DOI' value='10.17487/RFC8572'/>
</reference>
<reference anchor='I-D.birkholz-rats-reference-interaction-model'>
<front>
<title>Reference Interaction Models for Remote Attestation Procedures</tit
le>
<author fullname='Henk Birkholz'>
<organization>Fraunhofer SIT</organization>
</author>
<author fullname='Michael Eckel'>
<organization>Fraunhofer SIT</organization>
</author>
<author fullname='Christopher Newton'>
<organization>University of Surrey</organization>
</author>
<author fullname='Liqun Chen'>
<organization>University of Surrey</organization>
</author>
<date day='7' month='July' year='2020'/>
<abstract>
<t> This document describes interaction models for remote attestation
procedures (RATS). Three conveying mechanisms - Challenge/Response,
Uni-Directional, and Streaming Remote Attestation - are illustrated
and defined. Analogously, a general overview about the information
elements typically used by corresponding conveyance protocols are
highlighted. Privacy preserving conveyance of Evidence via Direct
Anonymous Attestation is elaborated on for each interaction model,
individually.
</t>
</abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-birkholz-rats-reference-intera
ction-model-03'/>
<format target='https://www.ietf.org/archive/id/draft-birkholz-rats-reference
-interaction-model-03.txt' type='TXT'/>
</reference>
<reference anchor='I-D.richardson-rats-usecases'>
<front>
<title>Use cases for Remote Attestation common encodings</title>
<author fullname='Michael Richardson'>
<organization>Sandelman Software Works</organization>
</author>
<author fullname='Carl Wallace'>
<organization>Red Hound Software</organization>
</author>
<author fullname='Wei Pan'>
<organization>Huawei Technologies</organization>
</author>
<date day='2' month='November' year='2020'/>
<abstract>
<t> This document details mechanisms created for performing Remote
Attestation that have been used in a number of industries. The
document initially focuses on existing industry verticals, mapping
terminology used in those specifications to the more abstract
terminology used by the IETF RATS Working Group.
The document aspires to describe possible future use cases that would
be enabled by common formats.
</t>
</abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-richardson-rats-usecases-08'/>
<format target='https://www.ietf.org/archive/id/draft-richardson-rats-usecase
s-08.txt' type='TXT'/>
</reference>
<reference anchor='I-D.birkholz-rats-tuda'>
<front>
<title>Time-Based Uni-Directional Attestation</title>
<author fullname='Andreas Fuchs'>
<organization>Fraunhofer Institute for Secure Information Technology</or
ganization>
</author>
<author fullname='Henk Birkholz'>
<organization>Fraunhofer Institute for Secure Information Technology</or
ganization>
</author>
<author fullname='Ira E McDonald'>
<organization>High North Inc</organization>
</author>
<author fullname='Carsten Bormann'>
<organization>Universität Bremen TZI</organization>
</author>
<date day='12' month='January' year='2022'/>
<abstract>
<t> This document defines the method and bindings used to convey Evide
nce
via Time-based Uni-Directional Attestation (TUDA) in Remote
ATtestation procedureS (RATS). TUDA does not require a challenge-
response handshake and thereby does not rely on the conveyance of a
nonce to prove freshness of remote attestation Evidence. TUDA
enables the creation of Secure Audit Logs that can constitute
believable Evidence about both current and past operational states of
an Attester. In TUDA, RATS entities require access to a Handle
Distributor to which a trustable and synchronized time-source is
available. The Handle Distributor takes on the role of a Time Stamp
Authority (TSA) to distribute Handles incorporating Time Stamp Tokens
(TST) to the RATS entities. RATS require an Attesting Environment
that generates believable Evidence. While a TPM is used as the
corresponding root of trust in this specification, any other type of
root of trust can be used with TUDA.
</t>
</abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-birkholz-rats-tuda-06'/>
<format target='https://www.ietf.org/archive/id/draft-birkholz-rats-tuda-06.t
xt' type='TXT'/>
</reference>
<reference anchor='I-D.birkholz-rats-network-device-subscription'>
<front>
<title>Attestation Event Stream Subscription</title>
<author fullname='Henk Birkholz'>
<organization>Fraunhofer SIT</organization>
</author>
<author fullname='Eric Voit'>
<organization>Cisco Systems, Inc.</organization>
</author>
<author fullname='Wei Pan'>
<organization>Huawei Technologies</organization>
</author>
<date day='17' month='August' year='2021'/>
<abstract>
<t> This memo defines how to subscribe to YANG Event Streams for Remot
e
Attestation Procedures (RATS). In RATS, Conceptional Messages, are
defined. Analogously, the YANG module defined in this memo augments
the YANG module for TPM-based Challenge-Response based Remote
Attestation (CHARRA) to allow for subscription to remote attestation
Evidence. Additionally, this memo provides the methods and means to
define additional Event Streams for other Conceptual Message as
illustrated in the RATS Architecture, e.g. Attestation Results,
Endorsements, or Event Logs.
</t>
</abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-birkholz-rats-network-device-s
ubscription-03'/>
<format target='https://www.ietf.org/archive/id/draft-birkholz-rats-network-d
evice-subscription-03.txt' type='TXT'/>
</reference>
<reference anchor='I-D.ietf-rats-eat'>
<front>
<title>The Entity Attestation Token (EAT)</title>
<author fullname='Laurence Lundblade'>
<organization>Security Theory LLC</organization>
</author>
<author fullname='Giridhar Mandyam'>
<organization>Qualcomm Technologies Inc.</organization>
</author>
<author fullname='Jeremy O&#39;Donoghue'>
<organization>Qualcomm Technologies Inc.</organization>
</author>
<date day='24' month='February' year='2022'/>
<abstract>
<t> An Entity Attestation Token (EAT) provides an attested claims set
that describes state and characteristics of an entity, a device like
a phone, IoT device, network equipment or such. This claims set is
used by a relying party, server or service to determine how much it
wishes to trust the entity.
An EAT is either a CBOR Web Token (CWT) or JSON Web Token (JWT) with
attestation-oriented claims. To a large degree, all this document
does is extend CWT and JWT.
</t>
</abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-ietf-rats-eat-12'/>
<format target='https://www.ietf.org/archive/id/draft-ietf-rats-eat-12.txt' t
ype='TXT'/>
</reference>
<reference anchor="TPM1.2" target="https://trustedcomputinggroup.org/resource/tp
m-main-specification/">
<front>
<title>TPM Main Specification Level 2 Version 1.2, Revision 116</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2011" month="March"/>
</front>
</reference>
<reference anchor="TPM2.0" target="https://trustedcomputinggroup.org/resource/tp
m-library-specification/">
<front>
<title>Trusted Platform Module Library Specification, Family "2.0", Level 00
, Revision 01.59</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2019" month="November"/>
</front>
</reference>
<reference anchor="Platform-Certificates" target="https://trustedcomputinggroup.
org/resource/tcg-platform-attribute-credential-profile/">
<front>
<title>TCG Platform Attribute Credential Profile, Specification Version 1.0,
Revision 16</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2018" month="January"/>
</front>
</reference>
<reference anchor="Provisioning-TPM-2.0" target="https://trustedcomputinggroup.o
rg/wp-content/uploads/TCG-TPM-v2.0-Provisioning-Guidance-Published-v1r1.pdf">
<front>
<title>TCG TPM v2.0 Provisioning Guidance, Version 1.0, Revision 1.0</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2015" month="March"/>
</front>
</reference>
<reference anchor="IEEE-802.1X" target="https://standards.ieee.org/standard/802_
1X-2020.html">
<front>
<title>802.1X-2020 - IEEE Standard for Local and Metropolitan Area Networks-
-Port-Based Network Access Control</title>
<author >
<organization>IEEE Computer Society</organization>
</author>
<date year="2020" month="February"/>
</front>
</reference>
<reference anchor="IEEE-802.1AE" target="https://1.ieee802.org/security/802-1ae/
">
<front>
<title>802.1AE MAC Security (MACsec)</title>
<author initials="M." surname="Seaman">
<organization>IEEE Computer Society</organization>
</author>
<date year="2018"/>
</front>
</reference>
<reference anchor="LLDP" target="https://standards.ieee.org/standard/802_1AB-201
6.html">
<front>
<title>802.1AB-2016 - IEEE Standard for Local and metropolitan area networks
- Station and Media Access Control Connectivity Discovery</title>
<author >
<organization>IEEE Computer Society</organization>
</author>
<date year="2016" month="March"/>
</front>
</reference>
<reference anchor="TCGRoT" target="https://trustedcomputinggroup.org/wp-content/
uploads/TCG_Roots_of_Trust_Specification_v0p20_PUBLIC_REVIEW.pdf">
<front>
<title>DRAFT: TCG Roots of Trust Specification</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2018" month="October"/>
</front>
</reference>
<reference anchor="SP800-193" target="https://nvlpubs.nist.gov/nistpubs/SpecialP
ublications/NIST.SP.800-193.pdf">
<front>
<title>NIST Special Publication 800-193: Platform Firmware Resiliency Guidel
ines</title>
<author >
<organization>National Institute for Standards and Technology</organizatio
n>
</author>
<date year="2018" month="April"/>
</front>
</reference>
<reference anchor="SP800-155" target="https://csrc.nist.gov/csrc/media/publicati
ons/sp/800-155/draft/documents/draft-sp800-155_dec2011.pdf">
<front>
<title>BIOS Integrity Measurement Guidelines (Draft)</title>
<author >
<organization>National Institute of Standards and Technology</organization
>
</author>
<date year="2011" month="December"/>
</front>
</reference>
<reference anchor="NetEq" target="https://trustedcomputinggroup.org/resource/tcg
-guidance-securing-network-equipment/">
<front>
<title>TCG Guidance for Securing Network Equipment, Version 1.0, Revision 29
</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2018" month="January"/>
</front>
</reference>
<reference anchor="NIST-IR-8060" target="https://nvlpubs.nist.gov/nistpubs/ir/20
16/NIST.IR.8060.pdf">
<front>
<title>Guidelines for the Creation of Interoperable Software Identification
(SWID) Tags</title>
<author >
<organization>National Institute for Standards and Technology</organizatio
n>
</author>
<date year="2016" month="April"/>
</front>
</reference>
<reference anchor="AK-Enrollment" target="https://trustedcomputinggroup.org/reso
urce/tcg-infrastructure-working-group-a-cmc-profile-for-aik-certificate-enrollme
nt/">
<front>
<title>TCG Infrastructure Working Group - A CMC Profile for AIK Certificate
Enrollment Version 1.0, Revision 7</title>
<author >
<organization>Trusted Computing Group</organization>
</author>
<date year="2011" month="March"/>
</front>
</reference>
<reference anchor="SWID-Gen" target="https://github.com/Labs64/swid-maven-plugin
">
<front>
<title>SoftWare IDentification (SWID) Tags Generator (Maven Plugin)</title>
<author >
<organization>Labs64, Munich, Germany</organization>
</author>
<date year="n.d."/>
</front>
</reference>
</references>
</back>
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c) FYI, there is an issue with xml2rfc that is cutting off text in Table 2 in th e txt output. We have asked the Tools Team to fix this issue <https://github.com /ietf-tools/xml2rfc/issues/1155>
--> -->
<table anchor="Component-Status">
<name>Component Status</name>
<thead>
<tr>
<th>Component</th>
<th>Controlling Specification</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<t>Make a Secure execution environment:</t>
<ul>
<li>Attestation depends on a secure RTM outside the TPM, as well as Ro
ots for Storage and Reporting inside the TPM.</li>
<li>Refer to "TCG Roots of Trust Specification" <xref target="TCG-RT"
format="default"/>.</li>
<li><xref target="SP800-193" format="default"/> also provides guidelin
es on Roots of Trust.</li>
</ul>
</td>
<td>
<t><xref target="TCG-RT" format="default"/></t>
<t><eref target="www.uefi.org" brackets="angle"/></t>
</td>
</tr>
<tr>
<td>Provision the TPM as described in the TCG documents.</td>
<td>
<t><xref target="PLATFORM-DEVID-TPM-2.0" format="default"/></t>
<t><xref target="PLATFORM-CERTS" format="default"/></t>
</td>
</tr>
<tr>
<td rowspan="2" colspan="">
<t>Put a DevID or Platform Certificate in the TPM:</t>
<ul>
<li>Install an IAK at the same time so that Attestation can work out o
f the box.</li>
<li>Equipment suppliers and owners may want to implement LDevID as wel
l as IDevID.</li>
</ul>
</td>
<td>
<t><xref target="PLATFORM-DEVID-TPM-2.0" format="default"/></t>
<t><xref target="PLATFORM-CERTS" format="default"/></t>
</td>
</tr>
<tr>
<td><xref target="IEEE-802-1AR" format="default"/></td>
</tr>
<tr>
<td>
<t>Connect the TPM to the TLS stack:</t>
<ul>
<li>Use the DevID in the TPM to authenticate TAP connections, identify
ing the device</li>
</ul>
</td>
<td>Vendor TLS stack (This action configures TLS to use the DevID as its c
lient certificate)</td>
</tr>
<tr>
<td>
<t>Make CoSWID tags for BIOS/Loader/Kernel objects:</t>
<ul>
<li>Add reference measurements into SWID tags.</li>
<li>Manufacturer should sign the SWID tags.</li>
<li>The TCG RIM-IM <xref target="RIM" format="default"/> identifies fu
rther procedures to create signed RIM documents that provide the necessary refer
ence information.</li>
</ul>
</td>
<td>
<t><xref target="RFC9393" format="default"/></t>
<t><xref target="SWID" format="default"/></t>
<t><xref target="NIST-IR-8060" format="default"/></t>
</td>
</tr>
<tr>
<td rowspan="2">
<t>Package the SWID tags with a vendor software release:</t>
<ul>
<li>A tag-generator plugin such as <xref target="SWID-GEN" format="def
ault"/> can be used.</li>
</ul>
</td>
<td>Retrieve tags with <xref target="RFC9393" format="default"/>.</td>
</tr>
<tr>
<td><xref target="PC-CLIENT-RIM" format="default"/></td>
</tr>
<tr>
<td>Use PC Client measurement definitions to define the use of PCRs (altho
ugh Windows OS is rare on Networking Equipment, UEFI BIOS is not).</td>
<td><xref target="PC-CLIENT-BIOS-TPM-2.0" format="default"/></td>
</tr>
<tr>
<td>
<t>Use TAP to retrieve measurements:</t>
<ul>
<li><t>Map to YANG.</t></li>
<li><t>Use Canonical Log Format.</t></li>
</ul>
</td>
<td>
<t><xref target="RFC9684" format="default"/></t>
<t><xref target="CEL" format="default"/></t>
</td>
</tr>
<tr>
<td>
<t>A Verifier (as described in <xref target="RFC9334" section="3" sectio
nFormat="comma"/>) should request the attestation and analyze the result. The Ve
rifier application might be broken down to several more components:</t>
<ul>
<li>A Posture Manager Server that collects reports and stores them in
a database.</li>
<li>One or more Analyzers that can look at the results and figure out
what it means.</li>
</ul>
</td>
<td>
</td>
</tr>
</tbody>
</table>
</section>
</section>
</rfc> <section anchor="acknowledgements" numbered="false" toc="default">
<name>Acknowledgements</name>
<t>The authors wish to thank numerous reviewers for generous assistance, i
ncluding <contact fullname="William Bellingrath"/>, <contact fullname="Mark Baus
hke"/>, <contact fullname="Ned Smith"/>,
<contact fullname="Henk Birkholz"/>, <contact fullname="Tom Laffey"/>, <contact
fullname="Dave Thaler"/>, <contact fullname="Wei Pan"/>, <contact fullname="Mich
ael Eckel"/>, <contact fullname="Thomas Hardjono"/>, <contact fullname="Bill Sul
zen"/>, <contact fullname="Willard (Monty) Wiseman"/>,
<contact fullname="Kathleen Moriarty"/>, <contact fullname="Nancy Cam-Winget"/>,
and <contact fullname="Shwetha Bhandari"/>.</t>
</section>
</back>
</rfc>
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