draft-ietf-rats-tpm-based-network-device-attest-03.txt   draft-ietf-rats-tpm-based-network-device-attest-04.txt 
RATS Working Group G. Fedorkow, Ed. RATS Working Group G. Fedorkow, Ed.
Internet-Draft Juniper Networks, Inc. Internet-Draft Juniper Networks, Inc.
Intended status: Informational E. Voit Intended status: Informational E. Voit
Expires: February 14, 2021 Cisco Systems, Inc. Expires: March 22, 2021 Cisco Systems, Inc.
J. Fitzgerald-McKay J. Fitzgerald-McKay
National Security Agency National Security Agency
August 13, 2020 September 18, 2020
TPM-based Network Device Remote Integrity Verification TPM-based Network Device Remote Integrity Verification
draft-ietf-rats-tpm-based-network-device-attest-03 draft-ietf-rats-tpm-based-network-device-attest-04
Abstract Abstract
This document describes a workflow for remote attestation of the This document describes a workflow for remote attestation of the
integrity of firmware and software installed on network devices that integrity of firmware and software installed on network devices that
contain Trusted Platform Modules [TPM]. contain Trusted Platform Modules [TPM1.2], [TPM2.0].
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
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Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 14, 2021. This Internet-Draft will expire on March 22, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Document Organization . . . . . . . . . . . . . . . . . . 4 1.2. Document Organization . . . . . . . . . . . . . . . . . . 4
1.3. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4. Description of Remote Integrity Verification (RIV) . . . 5 1.4. Description of Remote Integrity Verification (RIV) . . . 5
1.5. Solution Requirements . . . . . . . . . . . . . . . . . . 7 1.5. Solution Requirements . . . . . . . . . . . . . . . . . . 7
1.6. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.6. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.6.1. Out of Scope . . . . . . . . . . . . . . . . . . . . 8 1.6.1. Out of Scope . . . . . . . . . . . . . . . . . . . . 8
2. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 8 2. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 9
2.1. RIV Software Configuration Attestation using TPM . . . . 8 2.1. RIV Software Configuration Attestation using TPM . . . . 9
2.1.1. What Does RIV Attest? . . . . . . . . . . . . . . . . 10 2.1.1. What Does RIV Attest? . . . . . . . . . . . . . . . . 10
2.2. RIV Keying . . . . . . . . . . . . . . . . . . . . . . . 12 2.1.2. Notes on PCR Allocations . . . . . . . . . . . . . . 12
2.3. RIV Information Flow . . . . . . . . . . . . . . . . . . 13 2.2. RIV Keying . . . . . . . . . . . . . . . . . . . . . . . 13
2.4. RIV Simplifying Assumptions . . . . . . . . . . . . . . . 15 2.3. RIV Information Flow . . . . . . . . . . . . . . . . . . 14
2.4.1. Reference Integrity Manifests (RIMs) . . . . . . . . 16 2.4. RIV Simplifying Assumptions . . . . . . . . . . . . . . . 16
2.4.2. Attestation Logs . . . . . . . . . . . . . . . . . . 17 2.4.1. Reference Integrity Manifests (RIMs) . . . . . . . . 17
3. Standards Components . . . . . . . . . . . . . . . . . . . . 17 2.4.2. Attestation Logs . . . . . . . . . . . . . . . . . . 18
3.1. Prerequisites for RIV . . . . . . . . . . . . . . . . . . 18 3. Standards Components . . . . . . . . . . . . . . . . . . . . 19
3.1.1. Unique Device Identity . . . . . . . . . . . . . . . 18 3.1. Prerequisites for RIV . . . . . . . . . . . . . . . . . . 19
3.1.2. Keys . . . . . . . . . . . . . . . . . . . . . . . . 18 3.1.1. Unique Device Identity . . . . . . . . . . . . . . . 19
3.1.3. Appraisal Policy for Evidence . . . . . . . . . . . . 18 3.1.2. Keys . . . . . . . . . . . . . . . . . . . . . . . . 19
3.2. Reference Model for Challenge-Response . . . . . . . . . 19 3.1.3. Appraisal Policy for Evidence . . . . . . . . . . . . 19
3.2.1. Transport and Encoding . . . . . . . . . . . . . . . 21 3.2. Reference Model for Challenge-Response . . . . . . . . . 20
3.3. Centralized vs Peer-to-Peer . . . . . . . . . . . . . . . 21 3.2.1. Transport and Encoding . . . . . . . . . . . . . . . 22
4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 23 3.3. Centralized vs Peer-to-Peer . . . . . . . . . . . . . . . 23
5. Security Considerations . . . . . . . . . . . . . . . . . . . 23 4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 24
5.1. Keys Used in RIV . . . . . . . . . . . . . . . . . . . . 24 5. Security Considerations . . . . . . . . . . . . . . . . . . . 25
5.2. Prevention of Spoofing and Man-in-the-Middle Attacks . . 26 5.1. Keys Used in RIV . . . . . . . . . . . . . . . . . . . . 25
5.3. Replay Attacks . . . . . . . . . . . . . . . . . . . . . 27 5.2. Prevention of Spoofing and Man-in-the-Middle Attacks . . 27
5.4. Owner-Signed Keys . . . . . . . . . . . . . . . . . . . . 27 5.3. Replay Attacks . . . . . . . . . . . . . . . . . . . . . 28
5.5. Other Trust Anchors . . . . . . . . . . . . . . . . . . . 28 5.4. Owner-Signed Keys . . . . . . . . . . . . . . . . . . . . 28
6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 29 5.5. Other Trust Anchors . . . . . . . . . . . . . . . . . . . 29
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 30
8. Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . 29 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
8.1. Layering Model for Network Equipment Attester and 8. Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Verifier . . . . . . . . . . . . . . . . . . . . . . . . 29 8.1. Using a TPM for Attestation . . . . . . . . . . . . . . . 30
8.1.1. Why is OS Attestation Different? . . . . . . . . . . 31 8.2. Root of Trust for Measurement . . . . . . . . . . . . . . 32
8.2. Implementation Notes . . . . . . . . . . . . . . . . . . 31 8.3. Layering Model for Network Equipment Attester and
8.3. Root of Trust for Measurement . . . . . . . . . . . . . . 33 Verifier . . . . . . . . . . . . . . . . . . . . . . . . 32
9. Informative References . . . . . . . . . . . . . . . . . . . 33 8.3.1. Why is OS Attestation Different? . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 38 8.4. Implementation Notes . . . . . . . . . . . . . . . . . . 34
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 36
9.1. Normative References . . . . . . . . . . . . . . . . . . 36
9.2. Informative References . . . . . . . . . . . . . . . . . 38
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41
1. Introduction 1. Introduction
There are many aspects to consider in fielding a trusted computing There are many aspects to consider in fielding a trusted computing
device, from operating systems to applications. Mechanisms to prove device, from operating systems to applications. Mechanisms to prove
that a device installed at a customer's site is authentic (i.e., not that a device installed at a customer's site is authentic (i.e., not
counterfeit) and has been configured with authorized software, all as counterfeit) and has been configured with authorized software, all as
part of a trusted supply chain, are just a few of the many aspects part of a trusted supply chain, are just a few of the many aspects
which need to be considered concurrently to have confidence that a which need to be considered concurrently to have confidence that a
device is truly trustworthy. device is truly trustworthy.
A generic architecture for remote attestation has been defined in A generic architecture for remote attestation has been defined in
[I-D.ietf-rats-architecture]. Additionally, the use case for [I-D.ietf-rats-architecture]. Additionally, the use cases for
remotely attesting networking devices is within Section 6 of remotely attesting networking devices are discussed within Section 6
[I-D.richardson-rats-usecases]. However, these documents do not of [I-D.richardson-rats-usecases]. However, these documents do not
provide sufficient guidance for equipment vendors and network provide sufficient guidance for network equipment vendors and
operators to design, build, and deploy interoperable platforms. operators to design, build, and deploy interoperable devices.
The intent of this document is to provide such guidance. It does The intent of this document is to provide such guidance. It does
this by outlining the Remote Integrity Verification (RIV) problem, this by outlining the Remote Integrity Verification (RIV) problem,
and then identifies elements that are necessary to get the complete, and then identifies elements that are necessary to get the complete,
scalable attestation procedure working with commercial networking scalable attestation procedure working with commercial networking
products such as routers, switches and firewalls. An underlying products such as routers, switches and firewalls. An underlying
assumption will be the availability within the device of a Trusted assumption will be the availability within the device of a Trusted
Platform Module [TPM] compliant cryptoprocessor to enable the remote Platform Module [TPM1.2], [TPM2.0] compliant cryptoprocessor to
trustworthy assessment of the device's software and hardware. enable the trustworthy remote assessment of the device's software and
hardware.
1.1. Terminology 1.1. Terminology
A number of terms are reused from [I-D.ietf-rats-architecture]. A number of terms are reused from [I-D.ietf-rats-architecture].
These include: Appraisal Policy for Attestation Result, Attestation These include: Appraisal Policy for Attestation Results, Attestation
Result, Attester, Endorser, Evidence, Relying Party, Verifier, Result, Attester, Evidence, Relying Party, Verifier, and Verifier
Verifier Owner. Owner.
Additionally, this document defines the following terms: Additionally, this document defines the following terms:
Attestation: the process of creating, conveying and appraising Remote Attestation: the process of creating, conveying and appraising
assertions about Platform trustworthiness characteristics, including claims about device trustworthiness characteristics, including supply
supply chain trust, identity, platform provenance, software chain trust, identity, device provenance, software configuration,
configuration, hardware configuration, platform composition, hardware configuration, device composition, compliance to test
compliance to test suites, functional and assurance evaluations, etc. suites, functional and assurance evaluations, etc.
This document uses the term Endorser to refer to the trusted
authority for any signed object relating to the device, such as
certificates or reference measurement. Typically, the manufacturer
of an embedded device would be accepted as an Endorser.
The goal of attestation is simply to assure an administrator that the The goal of attestation is simply to assure an administrator that the
software that was launched when the device was last started is an software that was launched when the device was last started is an
authentic and untampered copy of the software that the device vendor authentic and untampered-with copy of the software that the device
shipped. vendor shipped.
Within the Trusted Computing Group context, attestation is the Within the Trusted Computing Group context, attestation is the
process by which an independent Verifier can obtain cryptographic process by which an independent Verifier can obtain cryptographic
proof as to the identity of the device in question, evidence of the proof as to the identity of the device in question, and evidence of
integrity of software loaded on that device when it started up, and the integrity of software loaded on that device when it started up,
then verify that what's there is what's supposed to be there. For and then verify that what's there is what's supposed to be there.
networking equipment, a verifier capability can be embedded in a For networking equipment, a Verifier capability can be embedded in a
Network Management Station (NMS), a posture collection server, or Network Management Station (NMS), a posture collection server, or
other network analytics tool (such as a software asset management other network analytics tool (such as a software asset management
solution, or a threat detection and mitigation tool, etc.). While solution, or a threat detection and mitigation tool, etc.). While
informally referred to as attestation, this document focuses on a informally referred to as attestation, this document focuses on a
subset defined here as Remote Integrity Verification (RIV). RIV subset defined here as Remote Integrity Verification (RIV). RIV
takes a network equipment centric perspective that includes a set of takes a network equipment centric perspective that includes a set of
protocols and procedures for determining whether a particular device protocols and procedures for determining whether a particular device
was launched with untampered software, starting from Roots of Trust. was launched with authentic software, starting from Roots of Trust.
While there are many ways to accomplish attestation, RIV sets out a While there are many ways to accomplish attestation, RIV sets out a
specific set of protocols and tools that work in environments specific set of protocols and tools that work in environments
commonly found in Networking Equipment. RIV does not cover other commonly found in Networking Equipment. RIV does not cover other
platform characteristics that could be attested (e.g. geographic device characteristics that could be attested (e.g., geographic
location, connectivity; see [I-D.richardson-rats-usecases]), although location, connectivity; see [I-D.richardson-rats-usecases]), although
it does provide evidence of a secure infrastructure to increase the it does provide evidence of a secure infrastructure to increase the
level of trust in other platform characteristics attested by other level of trust in other device characteristics attested by other
means (e.g., by Entity Attestation Tokens [I-D.ietf-rats-eat]). means (e.g., by Entity Attestation Tokens [I-D.ietf-rats-eat]).
1.2. Document Organization 1.2. Document Organization
The remainder of this document is organized into several sections: The remainder of this document is organized into several sections:
o The remainder of this section covers goals and requirements, plus o The remainder of this section covers goals and requirements, plus
a top-level description of RIV a top-level description of RIV.
o The Solution Overview section outlines how RIV works o The Solution Overview section outlines how Remote Integrity
Verification works.
o The Standards Components section links components of RIV to o The Standards Components section links components of RIV to
normative standards. normative standards.
o Privacy and Security shows how specific features of RIV contribute o Privacy and Security shows how specific features of RIV contribute
to the trustworthiness of the attestation result to the trustworthiness of the Attestation Result.
o Supporting material is in an appendix at the end. o Supporting material is in an appendix at the end.
1.3. Goals 1.3. Goals
Network operators benefit from a trustworthy attestation mechanism Network operators benefit from a trustworthy attestation mechanism
that provides assurance that their network comprises authentic that provides assurance that their network comprises authentic
equipment, and has loaded software free of known vulnerabilities and equipment, and has loaded software free of known vulnerabilities and
unauthorized tampering. In line with the overall goal of assuring unauthorized tampering. In line with the overall goal of assuring
integrity, attestation can be used for asset management, integrity, attestation can be used to assist in asset management,
vulnerability and compliance assessment, plus configuration vulnerability and compliance assessment, plus configuration
management. management.
As a part of a trusted supply chain, the RIV attestation workflow The RIV attestation workflow outlined in this document is intended to
outlined in this document is intended to meet the following high- meet the following high-level goals:
level goals:
o Provable Device Identity - This specification requires that an o Provable Device Identity - This specification requires that an
attesting device includes a cryptographic identifier unique to attesting device includes a cryptographic identifier unique to
each device. Effectively this means that the TPM must be so each device. Effectively this means that the TPM must be so
provisioned during the manufacturing cycle. provisioned during the manufacturing cycle.
o Software Inventory - A key goal is to identify the software o Software Inventory - A key goal is to identify the software
release installed on the attesting device, and to provide evidence release(s) installed on the attesting device, and to provide
that the software stored within hasn't been altered evidence that the software stored within hasn't been altered
without authorization.
o Verifiability - Verification of software and configuration of the o Verifiability - Verification of software and configuration of the
device shows that the software that was authorized for device shows that the software that was authorized for
installation by the administrator has actually been launched. installation by the administrator has actually been launched.
In addition, RIV is designed to operate in a centralized environment, In addition, RIV is designed to operate either in a centralized
such as with a central authority that manages and configures a number environment, such as with a central authority that manages and
of network devices, or 'peer-to-peer', where network devices configures a number of network devices, or 'peer-to-peer', where
independently verify one another to establish a trust relationship. network devices independently verify one another to establish a trust
(See Section 3.3 below, and also relationship. (See Section 3.3 below, and also
[I-D.voit-rats-trusted-path-routing]) [I-D.voit-rats-trusted-path-routing])
1.4. Description of Remote Integrity Verification (RIV) 1.4. Description of Remote Integrity Verification (RIV)
Attestation requires two interlocking services between the Attester Attestation requires two interlocking services between the Attester
network device and the Verifier: network device and the Verifier:
o Platform Identity, the mechanism providing trusted identity, can o Device Identity, the mechanism providing trusted identity, can
reassure network managers that the specific devices they ordered reassure network managers that the specific devices they ordered
from authorized manufacturers for attachment to their network are from authorized manufacturers for attachment to their network are
those that were installed, and that they continue to be present in those that were installed, and that they continue to be present in
their network. As part of the mechanism for Platform Identity, their network. As part of the mechanism for Device Identity,
cryptographic proof of the identity of the manufacturer is also cryptographic proof of the identity of the manufacturer is also
provided. provided.
o Software Measurement is the mechanism that reports the state of o Software Measurement is the mechanism that reports the state of
mutable software components on the device, and can assure network mutable software components on the device, and can assure network
managers that they have known, untampered software configured to managers that they have known, authentic software configured to
run in their network. run in their network.
Using these two interlocking services, RIV provides a procedure that Using these two interlocking services, RIV is a component in a chain
assures a network operator that the equipment in their network can be of procedures that can assure a network operator that the equipment
reliably identified, and that untampered software of a known version in their network can be reliably identified, and that authentic
is installed on each endpoint. Equipment in the network includes software of a known version is installed on each device. Equipment
devices that make up the network itself, such as routers, switches in the network includes devices that make up the network itself, such
and firewalls. as routers, switches and firewalls.
RIV includes several major processes: RIV includes several major processes:
1. Creation of Evidence is the process whereby an Attester generates 1. Creation of Evidence is the process whereby an Attester generates
cryptographic proof (Evidence) of claims about platform cryptographic proof (Evidence) of claims about device properties.
properties. In particular, the platform identity and its In particular, the device identity and its software configuration
software configuration are both of critical importance are both of critical importance.
2. Platform Identification refers to the mechanism assuring the 2. Device Identification refers to the mechanism assuring the
Relying Party (ultimately, a network administrator) of the Relying Party (ultimately, a network administrator) of the
identity of devices that make up their network, and that their identity of devices that make up their network, and that their
manufacturers are known. manufacturers are known.
3. Software used to boot a platform can be described as a chain of 3. Software used to boot a device can be described as a chain of
measurements, started by a Root of Trust for Measurement, that measurements, anchored at the start by a Root of Trust for
normally ends when the system software is loaded. A measurement Measurement, that normally ends when the system software is
signifies the identity, integrity and version of each software loaded. A measurement signifies the identity, integrity and
component registered with an attesting device's TPM [TPM], so version of each software component registered with an attesting
that the subsequent appraisal stage can determine if the software device's TPM [TPM1.2], [TPM2.0], so that the subsequent appraisal
installed is authentic, up-to-date, and free of tampering. stage can determine if the software installed is authentic, up-
to-date, and free of tampering.
4. Conveyance of Evidence reliably transports at least the minimum 4. Conveyance of Evidence reliably transports at least the minimum
amount of Evidence from Attester to a Verifier to allow a amount of Evidence from Attester to a Verifier to allow a
management station to perform a meaningful appraisal in Step 5. management station to perform a meaningful appraisal in Step 5.
The transport is typically carried out via a management network. The transport is typically carried out via a management network.
The channel must provide integrity and authenticity, and, in some The channel must provide integrity and authenticity, and, in some
use cases, may also require confidentiality. use cases, may also require confidentiality.
5. Finally, Appraisal of Evidence occurs. As the Verifier and 5. Finally, Appraisal of Evidence occurs. As the Verifier and
Relying Party roles are often combined within RIV, this is the Relying Party roles are often combined within RIV, this is the
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Attesting device, and using an Appraisal Policy to develop an Attesting device, and using an Appraisal Policy to develop an
Attestation Result, used to inform decision making. In practice, Attestation Result, used to inform decision making. In practice,
this means comparing the device measurements reported as Evidence this means comparing the device measurements reported as Evidence
with the Attester configuration expected by the Verifier. with the Attester configuration expected by the Verifier.
Subsequently the Appraisal Policy for Attestation Results might Subsequently the Appraisal Policy for Attestation Results might
match what was found against Reference Integrity Measurements match what was found against Reference Integrity Measurements
(aka Golden Measurements) which represent the intended configured (aka Golden Measurements) which represent the intended configured
state of the connected device. state of the connected device.
All implementations supporting this RIV specification require the All implementations supporting this RIV specification require the
support of the following three technologies: 1. Identity: Platform support of the following three technologies:
identity can be based on IEEE 802.1AR Device Identity [IEEE-802-1AR],
coupled with careful supply-chain management by the manufacturer.
The DevID certificate contains a statement by the manufacturer that
establishes 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), or with different privacy concerns, may want
to use alternative mechanisms for platform authentication (for
example, TCG Platform Certificates [Platform-Certificates]).
1. Platform Attestation provides evidence of configuration of 1. Identity: Device identity MUST be based on IEEE 802.1AR Device
Identity (DevID) [IEEE-802-1AR], coupled with careful supply-
chain management by the manufacturer. The DevID certificate
contains a statement by the manufacturer that establishes 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), or with different privacy concerns, may want to
use alternative mechanisms for platform authentication (for
example, TCG Platform Certificates [Platform-Certificates]).
2. Platform Attestation provides evidence of configuration of
software elements present in the device. This form of software elements present in the device. This form of
attestation can be implemented with TPM Platform Configuration attestation can be implemented with TPM Platform Configuration
Registers (PCRs), Quote and Log mechanisms, which provide an Registers (PCRs), Quote and Log mechanisms, which provide
authenticated mechanism to report what software was started on cryptographically authenticated evidence to report what software
the device through the boot cycle. Successful attestation was started on the device through the boot cycle. Successful
requires an unbroken chain from a boot-time root of trust through attestation requires an unbroken chain from a boot-time root of
all layers of software needed to bring the device to an trust through all layers of software needed to bring the device
operational state, in which each stage measures components of the to an operational state, in which each stage measures components
next stage, updates the attestation log, and extends hashes into of the next stage, updates the attestation log, and extends
a PCR. The TPM can then report the hashes of all the measured hashes into a PCR. The TPM can then report the hashes of all the
hashes as a signed Quote (see [TPM] for many more details). measured hashes as signed evidence called a Quote (see
Section 8.1 for an overview of TPM operation, or [TPM1.2] and
[TPM2.0] for many more details).
2. Reference Integrity Measurements must be conveyed from the 3. Reference Integrity Measurements must be conveyed from the
Endorser (the entity accepted as the software authority, often Endorser (the entity accepted as the software authority, often
the manufacturer for embedded systems) to the system in which the manufacturer for embedded systems) to the system in which
verification will take place verification will take place.
1.5. Solution Requirements 1.5. Solution Requirements
Remote Integrity Verification must address the "Lying Endpoint" Remote Integrity Verification 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 intended function, and also prevent the endpoint from reporting its
compromised status. (See Section 5 for further Security compromised status. (See Section 5 for further Security
Considerations) Considerations)
RIV attestation is designed to be simple to deploy at scale. RIV RIV attestation is designed to be simple to deploy at scale. RIV
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at the end-user's site, as network equipment is often required to at the end-user's site, as network equipment is often required to
"self-configure", to reliably reach out without manual intervention "self-configure", to reliably reach out without manual intervention
to prove its identity and operating posture, then download its own to prove its identity and operating posture, then download its own
configuration. See [RFC8572] for an example of Secure Zero Touch configuration. See [RFC8572] for an example of Secure Zero Touch
Provisioning. Provisioning.
1.6. Scope 1.6. Scope
Remote Attestation is a very general problem that could apply to most Remote Attestation is a very general problem that could apply to most
network-connected computing devices. However, this document includes network-connected computing devices. However, this document includes
several assumptions that limit the scope to Network Equipment (e.g. several assumptions that limit the scope to Network Equipment (e.g.,
routers, switches and firewalls): routers, switches and firewalls):
o This solution is for use in non-privacy-preserving applications o This solution is for use in non-privacy-preserving applications
(for example, networking, Industrial IoT), avoiding the need for a (for example, networking, Industrial IoT), avoiding the need for a
Privacy Certificate Authority for attestation keys Privacy Certificate Authority for attestation keys
[AIK-Enrollment] or TCG Platform Certificates [AIK-Enrollment] or TCG Platform Certificates
[Platform-Certificates] [Platform-Certificates]
o This document assumes network protocols that are common in o This document assumes network protocols that are common in
networking equipment such as YANG [RFC7950] and NETCONF [RFC6241], networking equipment such as YANG [RFC7950] and NETCONF [RFC6241],
but not generally used in other applications. but not generally used in other applications.
o The approach outlined in this document mandates the use of a o The approach outlined in this document mandates the use of a
compliant TPM [TPM]. Other roots of trust could be used with the compliant TPM [TPM1.2], [TPM2.0].
same information flow, although they're out of scope for this
document.
1.6.1. Out of Scope 1.6.1. Out of Scope
o Run-Time Attestation: Run-time attestation of Linux or other o Run-Time Attestation: Run-time attestation of Linux or other
multi-threaded operating system processes considerably expands the multi-threaded operating system processes considerably expands the
scope of the problem. Many researchers are working on that scope of the problem. Many researchers are working on that
problem, but this document defers the run-time attestation problem, but this document defers the run-time attestation
problem. problem.
o Multi-Vendor Embedded Systems: Additional coordination would be o Multi-Vendor Embedded Systems: Additional coordination would be
needed for devices that themselves comprise hardware and software needed for devices that themselves comprise hardware and software
from multiple vendors, integrated by the end user. from multiple vendors, integrated by the end user.
o Processor Sleep Modes: Network equipment typically does not o Processor Sleep Modes: Network equipment typically does not
"sleep", so sleep and hibernate modes are not considered. "sleep", so sleep and hibernate modes are not considered.
Although out of scope for RIV, Trusted Computing Group Although out of scope for RIV, Trusted Computing Group
specifications do encompass sleep and hibernate states. specifications do encompass sleep and hibernate states.
o Virtualization and Containerization: In a non-virtualized system, o Virtualization and Containerization: In a non-virtualized system,
the host OS is responsible for measuring each Userland file or the host OS is responsible for measuring each User Space file or
process, but that't the end of the chain of trust. For process, but that't the end of the boot process. For virtualized
virtualized systems, the host OS must verify the hypervisor, which systems, the host OS must verify the hypervisor, which then
then manages its own chain of trust through the virtual machine. manages its own chain of trust through the virtual machine.
Virtualization and containerization technologies are increasingly Virtualization and containerization technologies are increasingly
used in Network equipment, but are not considered in this revision used in Network equipment, but are not considered in this revision
of the document. of the document.
2. Solution Overview 2. Solution Overview
2.1. RIV Software Configuration Attestation using TPM 2.1. RIV Software Configuration Attestation using TPM
RIV Attestation is a process which can be used to determine the RIV Attestation is a process which can be used to determine the
identity of software running on a specifically-identified device. identity of software running on a specifically-identified device.
Remote Attestation is broken into two phases, shown in Figure 1: Remote Attestation is broken into two phases, shown in Figure 1:
o During system startup, each distinct software object is o During system startup, each distinct software object is
"measured". Its identity, hash (i.e. cryptographic digest) and "measured". Its identity, hash (i.e., cryptographic digest) and
version information are recorded in a log. Hashes are also version information are recorded in a log. Hashes are also
extended, or cryptographically folded, into the TPM, in a way that extended, or cryptographically folded, into the TPM, in a way that
can be used to validate the log entries. The measurement process can be used to validate the log entries. The measurement process
generally follows the Chain of Trust model used in Measured Boot, generally follows the Chain of Trust model used in Measured Boot,
where each stage of the system measures the next one, and extends where each stage of the system measures the next one, and extends
its measurement into the TPM, before launching it. its measurement into the TPM, before launching it.
o Once the device is running and has operational network o Once the device is running and has operational network
connectivity, a separate, trusted Verifier will interrogate the connectivity, a separate, trusted Verifier will interrogate the
network device to retrieve the logs and a copy of the digests network device to retrieve the logs and a copy of the digests
collected by hashing each software object, signed by an collected by hashing each software object, signed by an
attestation private key known only to the TPM. attestation private key known only to the TPM.
The result is that the Verifier can verify the device's identity by The result is that the Verifier can verify the device's identity by
checking the certificate containing the TPM's attestation public key, checking the Subject Field and signature of certificate containing
and can validate the software that was launched by comparing digests the TPM's attestation public key, and can validate the software that
in the log with known-good values, and verifying their correctness by was launched by verifying the correctness of the logs by comparing
comparing with the signed digests from the TPM. with the signed digests from the TPM, and comparing digests in the
log with known-good values.
It should be noted that attestation and identity are inextricably It should be noted that attestation and identity are inextricably
linked; signed Evidence that a particular version of software was linked; signed Evidence that a particular version of software was
loaded is of little value without cryptographic proof of the identity loaded is of little value without cryptographic proof of the identity
of the Attester producing the Evidence. of the Attester producing the Evidence.
+-------------------------------------------------------+ +-------------------------------------------------------+
| +--------+ +--------+ +--------+ +---------+ | | +--------+ +--------+ +--------+ +---------+ |
| | BIOS |--->| Loader |-->| Kernel |--->|Userland | | | | BIOS |--->| Loader |-->| Kernel |--->|Userland | |
| +--------+ +--------+ +--------+ +---------+ | | +--------+ +--------+ +--------+ +---------+ |
skipping to change at page 10, line 5 skipping to change at page 10, line 29
| |
| Step 2 | Step 2
| +-----------+ | +-----------+
+--->| Verifier | +--->| Verifier |
+-----------+ +-----------+
Reset---------------flow-of-time-during-boot--...-------> Reset---------------flow-of-time-during-boot--...------->
Figure 1: RIV Attestation Model Figure 1: RIV Attestation Model
In Step 1, measurements are "extended" into the TPM as processes In Step 1, measurements are "extended", or hashed, into the TPM as
start. In Step 2, signed PCR digests are retrieved from the TPM for processes start, with the result that the PCR ends up containing a
off-box analysis after the system is operational. hash of all the measured hashes. In Step 2, signed PCR digests are
retrieved from the TPM for off-box analysis after the system is
operational.
2.1.1. What Does RIV Attest? 2.1.1. What Does RIV Attest?
TPM attestation is strongly focused on Platform Configuration TPM attestation is strongly focused on Platform Configuration
Registers (PCRs), but those registers are only vehicles for Registers (PCRs), but those registers are only vehicles for
certifying accompanying Evidence, conveyed in log entries. It is the certifying accompanying Evidence, conveyed in log entries. It is the
hashes in log entries that are extended into PCRs, where the final hashes in log entries that are extended into PCRs, where the final
digests can be retrieved in the form of a Quote signed by a key known PCR values can be retrieved in the form of a structured called a
only to the TPM. The use of multiple PCRs serves only to provide Quote, signed by an Attestation key known only to the TPM. The use
some independence between different classes of object, so that one of multiple PCRs serves only to provide some independence between
class of objects can be updated without changing the extended hash different classes of object, so that one class of objects can be
for other classes. Although PCRs can be used for any purpose, this updated without changing the extended hash for other classes.
section outlines the objects within the scope of this document which Although PCRs can be used for any purpose, this section outlines the
may be extended into the TPM. objects within the scope of this document which may be extended into
the TPM.
In general, PCRs are organized to independently attest three classes In general, assignment of measurements to PCRs is a policy choice
of object: made by the device manufacturer, selected to independently attest
three classes of object:
o Code, i.e., instructions to be executed by a CPU. o Code, (i.e., instructions) to be executed by a CPU.
o Configuration - Many devices offer numerous options controlled by o Configuration - Many devices offer numerous options controlled by
non-volatile configuration variables which can impact the device's non-volatile configuration variables which can impact the device's
security posture. These settings may have vendor defaults, but security posture. These settings may have vendor defaults, but
often can be changed by administrators, who may want to verify via often can be changed by administrators, who may want to verify via
attestation that the settings they intend are still in place. attestation that the settings they intend are still in place.
o Credentials - Administrators may wish to verify via attestation o Credentials - Administrators may wish to verify via attestation
that keys (and other credentials) outside the Root of Trust have that keys (and other credentials) outside the Root of Trust have
not been subject to unauthorized tampering. (By definition, keys not been subject to unauthorized tampering. (By definition, keys
inside the root of trust can't be verified independently) inside the root of trust can't be verified independently).
The TCG PC Client Platform Firmware Profile Specification The TCG PC Client Platform Firmware Profile Specification
[PC-Client-BIOS-TPM-2.0] gives considerable detail on what is to be [PC-Client-BIOS-TPM-2.0] gives considerable detail on what is to be
measured during the boot phase of a platform boot using a UEFI BOIS measured during the boot phase of platform startup using a UEFI BOIS
(www.uefi.org), but the goal is simply to measure every bit of code (www.uefi.org), but the goal is simply to measure every bit of code
executed in the process of starting the device, along with any executed in the process of starting the device, along with any
configuration information related to security posture, leaving no gap configuration information related to security posture, leaving no gap
for unmeasured code to subvert the chain. for unmeasured code to remain undetected and subvert the chain.
For platforms using a UEFI BIOS, [PC-Client-BIOS-TPM-2.0] gives For devices using a UEFI BIOS, [PC-Client-BIOS-TPM-2.0] gives
detailed normative requirements for PCR usage. But for other detailed normative requirements for PCR usage. But for other
platform architectures, the table in Figure 2 gives guidance for PCR platform architectures, the table in Figure 2 gives guidance for PCR
assignment that generalizes the specific details of assignment that generalizes the specific details of
[PC-Client-BIOS-TPM-2.0]. [PC-Client-BIOS-TPM-2.0].
By convention, most PCRs are allocated in pairs, which the even- By convention, most PCRs are assigned in pairs, which the even-
numbered PCR used to measure executable code, and the odd-numbered numbered PCR used to measure executable code, and the odd-numbered
PCR used to measure whatever data and configuration are associated PCR used to measure whatever data and configuration are associated
with that code. It is important to note that each PCR may contain with that code. It is important to note that each PCR may contain
results from dozens (or even thousands) of individual measurements. results from dozens (or even thousands) of individual measurements.
+------------------------------------------------------------------+ +------------------------------------------------------------------+
| | Allocated PCR # | | | Assigned PCR # |
| Function | Code | Configuration| | Function | Code | Configuration|
-------------------------------------------------------------------- --------------------------------------------------------------------
| Firmware Static Root of Trust, i.e., | 0 | 1 | | Firmware Static Root of Trust, (i.e., | 0 | 1 |
| initial boot firmware and drivers | | | | initial boot firmware and drivers) | | |
-------------------------------------------------------------------- --------------------------------------------------------------------
| Drivers and initialization for optional | 2 | 3 | | Drivers and initialization for optional | 2 | 3 |
| or add-in devices | | | | or add-in devices | | |
-------------------------------------------------------------------- --------------------------------------------------------------------
| OS Loader code and configuration, i.e., | 4 | 5 | | OS Loader code and configuration, (i.e., | 4 | 5 |
| the code launched by firmware to load an | | | | the code launched by firmware) to load an | | |
| operating system kernel. These PCRs record | | | | operating system kernel. These PCRs record | | |
| each boot attempt, and an identifier for | | | | each boot attempt, and an identifier for | | |
| where the loader was found | | | | where the loader was found | | |
-------------------------------------------------------------------- --------------------------------------------------------------------
| Vendor Specific Measurements during boot | 6 | 6 | | Vendor Specific Measurements during boot | 6 | 6 |
-------------------------------------------------------------------- --------------------------------------------------------------------
| Secure Boot Policy. This PCR records keys | | 7 | | Secure Boot Policy. This PCR records keys | | 7 |
| and configuration used to validate the OS | | | | and configuration used to validate the OS | | |
| loader | | | | loader | | |
-------------------------------------------------------------------- --------------------------------------------------------------------
| Measurements made by the OS Loader | 8 | 9 | | Measurements made by the OS Loader | 8 | 9 |
| (e.g GRUB2 for Linux) | | | | (e.g GRUB2 for Linux) | | |
-------------------------------------------------------------------- --------------------------------------------------------------------
| Measurements made by OS (e.g. Linux IMA) | 10 | 10 | | Measurements made by OS (e.g., Linux IMA) | 10 | 10 |
+------------------------------------------------------------------+ +------------------------------------------------------------------+
Figure 2: Attested Objects Figure 2: Attested Objects
Notes on PCR Allocations 2.1.2. Notes on PCR Allocations
It is important to recognize that PCR[0] is critical. The first It is important to recognize that PCR[0] is critical. The first
measurement into PCR[0] taken by the Root of Trust for Measurement, measurement into PCR[0] taken by the Root of Trust for Measurement,
is critical to establishing the chain of trust for all subsequent is critical to establishing the chain of trust for all subsequent
measurements. If the PCR[0] measurement cannot be trusted, the measurements. If the PCR[0] measurement cannot be trusted, the
validity of the entire chain is put into question. validity of the entire chain is put into question.
Distinctions Between PCR[0], PCR[2], PCR[4] and PCR[8] Distinctions Between PCR[0], PCR[2], PCR[4] and PCR[8] are summarized
below:
o PCR[0] typically represents a consistent view of the Host Platform o PCR[0] typically represents a consistent view of the Host Platform
between boot cycles, allowing Attestation and Sealed Storage between boot cycles, allowing Attestation and Sealed Storage
policies to be defined using the less changeable components of the policies to be defined using the less changeable components of the
transitive trust chain. This PCR typically provides a consistent transitive trust chain. This PCR typically provides a consistent
view of the platform regardless of user selected options. view of the platform regardless of user selected options.
o PCR[2] is intended to represent a "user configurable" environment o PCR[2] is intended to represent a "user configurable" environment
where the user has the ability to alter the components that are where the user has the ability to alter the components that are
measured into PCR[2]. This is typically done by adding adapter measured into PCR[2]. This is typically done by adding adapter
cards, etc., into user-accessible PCI or other slots. In UEFI cards, etc., into user-accessible PCI or other slots. In UEFI
systems these devices may be configured by Option ROMsm easured systems these devices may be configured by Option ROMs measured
into PCR[2] and executed by the BIOS. into PCR[2] and executed by the BIOS.
o PCR[4] is intended to represent the software that manages the o PCR[4] is intended to represent the software that manages the
transition between the platform's Pre-Operating System Start and transition between the platform's Pre-Operating System Start and
the state of a system with the Operating System present. This the state of a system with the Operating System present. This
PCR, along with PCR[5], identifies the initial operating system PCR, along with PCR[5], identifies the initial operating system
loader (e.g. GRUB for Linux) loader (e.g., GRUB for Linux).
o PCR[8] is used by the OS loader to record measurements of the o PCR[8] is used by the OS loader to record measurements of the
various components of the operating system. various components of the operating system.
Although the TCG PC Client document specifies the use of the first Although the TCG PC Client document specifies the use of the first
eight PCRs very carefully to ensure interoperability among multiple eight PCRs very carefully to ensure interoperability among multiple
UEFI BIOS vendors, it should be noted that embedded software vendors UEFI BIOS vendors, it should be noted that embedded software vendors
may have considerably more flexibility. Verifiers typically need to may have considerably more flexibility. Verifiers typically need to
know which log entries are consequential and which are not (possibly know which log entries are consequential and which are not (possibly
controlled by local policies) but the verifier may not need to know controlled by local policies) but the Verifier may not need to know
what each log entry means or why it was assigned to a particular PCR. what each log entry means or why it was assigned to a particular PCR.
Designers must recognize that some PCRs may cover log entries that a Designers must recognize that some PCRs may cover log entries that a
particular verifier considers critical and other log entries that are particular Verifier considers critical and other log entries that are
not considered important, so differing PCR values may not on their not considered important, so differing PCR values may not on their
own constitute a check for authenticity. own constitute a check for authenticity.
Designers may allocate particular events to specific PCRs in order to Designers may allocate particular events to specific PCRs in order to
achieve a particular objective with Local Attestation, i.e., allowing achieve a particular objective with Local Attestation, (e.g.,
a procedure to execute only if a given PCR is in a given state. It allowing a procedure to execute only if a given PCR is in a given
may also be important to designers to consider whether streaming state). It may also be important to designers to consider whether
notification of PCR updates is required (see ID Rats Streaming). streaming notification of PCR updates is required (see
Specific log entries can only be validated if the verifier receives [I-D.birkholz-rats-network-device-subscription]). Specific log
every log entry affecting the relevant PCR, so (for example) a entries can only be validated if the Verifier receives every log
designer might want to separate rare, high-value events such as entry affecting the relevant PCR, so (for example) a designer might
configuration changes, from high-volume, routine measurements such as want to separate rare, high-value events such as configuration
IMA logs. changes, from high-volume, routine measurements such as IMA [IMA]
logs.
2.2. RIV Keying 2.2. RIV Keying
RIV attestation relies on two keys: RIV attestation relies on two keys:
o An identity key is required to certify the identity of the o An identity key is required to certify the identity of the
Attester itself. RIV specifies the use of an IEEE 802.1AR DevID Attester itself. RIV specifies the use of an IEEE 802.1AR Device
[IEEE-802-1AR], signed by the device manufacturer, containing the Identity (DevID) [IEEE-802-1AR], signed by the device
device serial number. manufacturer, containing the device serial number.
o An Attestation Key is required to sign the Quote generated by the o An Attestation Key is required to sign the Quote generated by the
TPM to report evidence of software configuration. TPM to report evidence of software configuration.
In TPM application, the Attestation key must be protected by the TPM, In TPM application, the Attestation key MUST be protected by the TPM,
and the DevID should be as well. Depending on other TPM and the DevID SHOULD be as well. Depending on other TPM
configuration procedures, the two keys may be different. Some of the configuration procedures, the two keys are likely be different; some
considerations are outlined in TCG Guidance for Securing Network of the considerations are outlined in TCG Guidance for Securing
Equipment [NetEq]. Network Equipment [NetEq].
TCG Guidance for Securing Network Equipment specifies further TCG Guidance for Securing Network Equipment specifies further
conventions for these keys: conventions for these keys:
o When separate Identity and Attestation keys are used, the o When separate Identity and Attestation keys are used, the
Attestation Key (AK) and its x.509 certificate should parallel the Attestation Key (AK) and its X.509 certificate should parallel the
DevID, with the same device ID information as the DevID DevID, with the same device ID information as the DevID
certificate (i.e., the same Subject Name and Subject Alt Name, certificate (i.e., the same Subject Name and Subject Alt Name,
even though the key pairs are different). This allows a quote even though the key pairs are different). This allows a quote
from the device, signed by an AK, to be linked directly to the from the device, signed by an AK, to be linked directly to the
device that provided it, by examining the corresponding AK device that provided it, by examining the corresponding AK
certificate. certificate.
o Network devices that are expected to use secure zero touch o Network devices that are expected to use secure zero touch
provisioning as specified in [RFC8572]) must be shipped by the provisioning as specified in [RFC8572]) MUST be shipped by the
manufacturer with pre-provisioned keys (Initial DevID and AK, manufacturer with pre-provisioned keys (Initial DevID and AK,
called IDevID and IAK). Inclusion of an DevID and IAK by a vendor called IDevID and IAK). Inclusion of an IDevID and IAK by a
does not preclude a mechanism whereby an Administrator can define vendor does not preclude a mechanism whereby an Administrator can
Local Identity and Attestation Keys (LDevID and LAK) if desired. define Local Identity and Attestation Keys (LDevID and LAK) if
desired. IDevID and IAK certificates MUST both be signed by the
Endorser (typically the device manufacturer).
2.3. RIV Information Flow 2.3. RIV Information Flow
RIV workflow for networking equipment is organized around a simple RIV workflow for networking equipment is organized around a simple
use-case, where a network operator wishes to verify the integrity of use case where a network operator wishes to verify the integrity of
software installed in specific, fielded devices. This use-case software installed in specific, fielded devices. This use case
implies several components: implies several components:
1. The Attesting Device, which the network operator wants to 1. The Attesting Device, which the network operator wants to
examine. examine.
2. A Verifier (which might be a network management station) 2. A Verifier (which might be a network management station)
somewhere separate from the Device that will retrieve the somewhere separate from the Device that will retrieve the
information and analyze it to pass judgment on the security information and analyze it to pass judgment on the security
posture of the device. posture of the device.
3. A Relying Party, which can act on Attestation results. 3. A Relying Party, which can act on Attestation Results.
Interaction between the Relying Party and the Verifier is Interaction between the Relying Party and the Verifier is
considered out of scope for RIV. considered out of scope for RIV.
4. Signed Reference Integrity Manifests (RIMs), containing Reference 4. Signed Reference Integrity Manifests (RIMs), containing Reference
Integrity Measurements, can either be created by the device Integrity Measurements, can either be created by the device
manufacturer and shipped along with the device as part of its manufacturer and shipped along with the device as part of its
software image, or alternatively, could be obtained several other software image, or alternatively, could be obtained several other
ways (direct to the Verifier from the manufacturer, from a third ways (direct to the Verifier from the manufacturer, from a third
party, from the owner's observation of what's thought to be a party, from the owner's observation of what's thought to be a
"known good system", etc.). Retrieving RIMs from the device "known good system", etc.). Retrieving RIMs from the device
itself allows attestation to be done in systems which may not itself allows attestation to be done in systems that may not have
have access to the public internet, or by other devices that are access to the public internet, or by other devices that are not
not management stations per-se (e.g., a peer device; See management stations per se (e.g., a peer device; see
Section 3.1.3). If reference measurements are obtained from Section 3.1.3). If Reference Integrity Measurements are obtained
multiple sources, the Verifier may need to evaluate the relative from multiple sources, the Verifier may need to evaluate the
level of trust to be placed in each source in case of a relative level of trust to be placed in each source in case of a
discrepancy. discrepancy.
These components are illustrated in Figure 2. These components are illustrated in Figure 3.
A more-detailed taxonomy of terms is given in A more-detailed taxonomy of terms is given in
[I-D.ietf-rats-architecture] [I-D.ietf-rats-architecture]
+---------------+ +-------------+ +---------+--------+ +---------------+ +-------------+ +---------+--------+
| | | Attester | Step 1 | Verifier| | | | | Attester | Step 1 | Verifier| |
| Endorser | | (Device |<-------| (Network| Relying| | Endorser | | (Device |<-------| (Network| Relying|
| (Device | | under |------->| Mngmt | Party | | (Device | | under |------->| Mngmt | Party |
| Manufacturer | | attestation)| Step 2 | Station)| | | Manufacturer | | attestation)| Step 2 | Station)| |
| or other | | | | | | | or other | | | | | |
| authority) | | | | | | | authority) | | | | | |
+---------------+ +-------------+ +---------+--------+ +---------------+ +-------------+ +---------+--------+
| /\ | /\
| Step 0 | | Step 0 |
----------------------------------------------- -----------------------------------------------
Figure 3: RIV Reference Configuration for Network Equipment Figure 3: RIV Reference Configuration for Network Equipment
In Step 0, The Endorser (the device manufacturer) provides a Software In Step 0, The Endorser (the device manufacturer or other authority)
Image to the Attester (the device under attestation), and makes one provides a software image to the Attester (the device under
or more Reference Integrity Manifests (RIMs) signed by the Endorser, attestation), and makes one or more Reference Integrity Manifests
available to the Verifier (see Section 3.1.3 for "in-band" and "out (RIMs) signed by the Endorser, available to the Verifier (see
of band" ways to make this happen). In Step 1, the Verifier (Network Section 3.1.3 for "in-band" and "out of band" ways to make this
Management Station), on behalf of a Relying Party, requests Identity, happen). In Step 1, the Verifier (Network Management Station), on
Measurement Values (and possibly RIMs) from the Attester. In Step 2, behalf of a Relying Party, requests Identity, Measurement Values, and
the Attester responds to the request by providing a DevID, quotes possibly RIMs, from the Attester. In Step 2, the Attester responds
(measured values), and optionally RIMs, signed by the Attester. to the request by providing a DevID, quotes (measured values, signed
by the Attester), and optionally RIMs.
The following standards components may be used: To achieve interoperability, the following standards components
SHOULD be used:
1. TPM Keys are configured according to [Platform-DevID-TPM-2.0], 1. TPM Keys MUST be configured according to
[PC-Client-BIOS-TPM-1.2], or [Platform-ID-TPM-1.2] [Platform-DevID-TPM-2.0], [PC-Client-BIOS-TPM-1.2], or
[Platform-ID-TPM-1.2].
2. Measurements of firmware and bootable modules may be taken 2. For devices using UEFI and Linux, measurements of firmware and
according to TCG PC Client [PC-Client-BIOS-TPM-2.0] and Linux IMA bootable modules SHOULD be taken according to TCG PC Client
[IMA] [PC-Client-BIOS-TPM-2.0] and Linux IMA [IMA]
3. Device Identity is managed by IEEE 802.1AR certificates 3. Device Identity MUST be managed as specified in IEEE 802.1AR
[IEEE-802-1AR], with keys protected by TPMs. Device Identity certificates [IEEE-802-1AR], with keys protected
by TPMs.
4. Attestation logs may be formatted according to the Canonical 4. Attestation logs SHOULD be formatted according to the Canonical
Event Log format [Canonical-Event-Log], although other Event Log format [Canonical-Event-Log], although other
specialized formats may be used. specialized formats may be used. UEFI-based systems MAY use the
TCG UEFI BIOS event log [EFI-TPM]).
5. Quotes are retrieved from the TPM according to the TCG TAP 5. Quotes are retrieved from the TPM according to the TCG TAP
Information Model [TAP]. While the TAP IM gives a protocol- Information Model [TAP]. While the TAP IM gives a protocol-
independent description of the data elements involved, it's independent description of the data elements involved, it's
important to note that quotes from the TPM are signed inside the important to note that quotes from the TPM are signed inside the
TPM, so must be retrieved in a way that does not invalidate the TPM, so MUST be retrieved in a way that does not invalidate the
signature, as specified in [I-D.ietf-rats-yang-tpm-charra], to signature, as specified in [I-D.ietf-rats-yang-tpm-charra], to
preserve the trust model. (See Section 5 Security preserve the trust model. (See Section 5 Security
Considerations). Considerations).
6. Reference Integrity Measurements may be encoded as CoSWID tags, 6. Reference Integrity Measurements SHOULD be encoded as CoSWID
as defined in the TCG RIM document [RIM], compatible with NIST IR tags, as defined in the TCG RIM document [RIM], compatible with
8060 [NIST-IR-8060] and the IETF CoSWID draft NIST IR 8060 [NIST-IR-8060] and the IETF CoSWID draft
[I-D.ietf-sacm-coswid]. See Section 2.4.1. [I-D.ietf-sacm-coswid]. See Section 2.4.1.
2.4. RIV Simplifying Assumptions 2.4. RIV Simplifying Assumptions
This document makes the following simplifying assumptions to reduce This document makes the following simplifying assumptions to reduce
complexity: complexity:
o The product to be attested is shipped with an IEEE 802.1AR DevID o The product to be attested MUST be shipped with an IEEE 802.1AR
and an Initial Attestation Key (IAK) with certificate. The IAK Device Identity and an Initial Attestation Key (IAK) with
cert contains the same identity information as the DevID certificate. The IAK cert contains the same identity information
(specifically, the same Subject Name and Subject Alt Name, signed as the DevID (specifically, the same Subject Name and Subject Alt
by the manufacturer), but it's a type of key that can be used to Name, signed by the manufacturer), but it's a type of key that can
sign a TPM Quote. This convention is described in TCG Guidance be used to sign a TPM Quote. This convention is described in TCG
for Securing Network Equipment [NetEq]. For network equipment, Guidance for Securing Network Equipment [NetEq]. For network
which is generally non-privacy-sensitive, shipping a device with equipment, which is generally non-privacy-sensitive, shipping a
both an IDevID and an IAK already provisioned substantially device with both an IDevID and an IAK already provisioned
simplifies initial startup. Privacy-sensitive applications may substantially simplifies initial startup. Privacy-sensitive
use the TCG Platform Certificate and additional procedures to applications may use the TCG Platform Certificate and additional
install identity credentials on the platform after manufacture. procedures to install identity credentials into the device after
manufacture.
o The product is equipped with a Root of Trust for Measurement, Root o The product MUST be equipped with a Root of Trust for Measurement,
of Trust for Storage and Root of Trust for Reporting (as defined Root of Trust for Storage and Root of Trust for Reporting (as
in [SP800-155]) that are capable of conforming to the TCG Trusted defined in [SP800-155]) that are capable of conforming to the TCG
Attestation Protocol (TAP) Information Model [TAP]. Trusted Attestation Protocol (TAP) Information Model [TAP].
o The vendor will ship Reference Integrity Measurements (i.e., o The authorized software supplier MUST make available Reference
known-good measurements) in the form of signed CoSWID tags Integrity Measurements (i.e., known-good measurements) in the form
[I-D.ietf-sacm-coswid], [SWID], as described in TCG Reference of signed CoSWID tags [I-D.ietf-sacm-coswid], [SWID], as described
Integrity Measurement Manifest Information Model [RIM]. in TCG Reference Integrity Measurement Manifest Information Model
[RIM].
2.4.1. Reference Integrity Manifests (RIMs) 2.4.1. Reference Integrity Manifests (RIMs)
[I-D.ietf-rats-yang-tpm-charra] focuses on collecting and [I-D.ietf-rats-yang-tpm-charra] focuses on collecting and
transmitting evidence in the form of PCR measurements and attestation transmitting evidence in the form of PCR measurements and attestation
logs. But the critical part of the process is enabling the verifier logs. But the critical part of the process is enabling the Verifier
to decide whether the measurements are "the right ones" or not. to decide whether the measurements are "the right ones" or not.
While it must be up to network administrators to decide what they While it must be up to network administrators to decide what they
want on their networks, the software supplier should supply the want on their networks, the software supplier should supply the
Reference Integrity Measurements that may be used by a verifier to Reference Integrity Measurements that may be used by a Verifier to
determine if evidence shows known good, known bad or unknown software determine if evidence shows known good, known bad or unknown software
configurations. configurations.
In general, there are two kinds of reference measurements: In general, there are two kinds of reference measurements:
1. Measurements of early system startup (e.g., BIOS, boot loader, OS 1. Measurements of early system startup (e.g., BIOS, boot loader, OS
kernel) are essentially single threaded, and executed exactly kernel) are essentially single-threaded, and executed exactly
once, in a known sequence, before any results could be reported. once, in a known sequence, before any results could be reported.
In this case, while the method for computing the hash and In this case, while the method for computing the hash and
extending relevant PCRs may be complicated, the net result is extending relevant PCRs may be complicated, the net result is
that the software (more likely, firmware) vendor will have one that the software (more likely, firmware) vendor will have one
known good PCR value that "should" be present in the relevant known good PCR value that "should" be present in the relevant
PCRs after the box has booted. In this case, the signed PCRs after the box has booted. In this case, the signed
reference measurement could simply list the expected hashes for reference measurement could simply list the expected hashes for
the given version. However, a RIM that contains the intermediate the given version. However, a RIM that contains the intermediate
hashes can be useful in debugging cases where the expected final hashes can be useful in debugging cases where the expected final
hash is not the one reported. hash is not the one reported.
skipping to change at page 17, line 29 skipping to change at page 18, line 32
specific case of a UEFI-compatible BIOS, where the SWID focus on specific case of a UEFI-compatible BIOS, where the SWID focus on
files and file systems is not a direct fit. While the PC Client RIM files and file systems is not a direct fit. While the PC Client RIM
is not directly applicable to network equipment, many vendors do use is not directly applicable to network equipment, many vendors do use
a conventional UEFI BIOS to launch their network OS. a conventional UEFI BIOS to launch their network OS.
2.4.2. Attestation Logs 2.4.2. Attestation Logs
Quotes from a TPM can provide evidence of the state of a device up to Quotes from a TPM can provide evidence of the state of a device up to
the time the evidence was recorded, but to make sense of the quote in the time the evidence was recorded, but to make sense of the quote in
most cases an event log that identifies which software modules most cases an event log that identifies which software modules
contributed which values to the quote during startup must also be contributed which values to the quote during startup MUST also be
provided. The log must contain enough information to demonstrate its provided. The log MUST contain enough information to demonstrate its
integrity by allowing exact reconstruction of the digest conveyed in integrity by allowing exact reconstruction of the digest conveyed in
the signed quote (i.e., PCR values). the signed quote (i.e., PCR values).
There are multiple event log formats which may be supported as viable There are multiple event log formats which may be supported as viable
formats of Evidence between the Attester and Verifier: formats of Evidence between the Attester and Verifier:
o Event log exports from [I-D.ietf-rats-yang-tpm-charra] o Event log exports from [I-D.ietf-rats-yang-tpm-charra]
o IMA Event log file exports [IMA] o IMA Event log file exports [IMA]
o TCG UEFI BIOS event log (TCG EFI Platform Specification for TPM o TCG UEFI BIOS event log (TCG EFI Platform Specification for TPM
Family 1.1 or 1.2, Section 7 [EFI-TPM]) Family 1.1 or 1.2, Section 7) [EFI-TPM])
o TCG Canonical Event Log [Canonical-Event-Log] o TCG Canonical Event Log [Canonical-Event-Log]
Devices which use UEFI BIOS and Linux SHOULD use TCG Canonical Event
Log [Canonical-Event-Log] and TCG UEFI BIOS event log [EFI-TPM])
3. Standards Components 3. Standards Components
3.1. Prerequisites for RIV 3.1. Prerequisites for RIV
The Reference Interaction Model for Challenge-Response-based Remote The Reference Interaction Model for Challenge-Response-based Remote
Attestation is based on the standard roles defined in Attestation is based on the standard roles defined in
[I-D.ietf-rats-architecture]. However additional prerequisites must [I-D.ietf-rats-architecture]. However additional prerequisites have
be established to allow for interoperable RIV use case been established to allow for interoperable RIV use case
implementations. These prerequisites are intended to provide implementations. These prerequisites are intended to provide
sufficient context information so that the Verifier can acquire and sufficient context information so that the Verifier can acquire and
evaluate Attester measurements. evaluate Attester measurements.
3.1.1. Unique Device Identity 3.1.1. Unique Device Identity
A Secure device Identity (DevID) in the form of an IEEE 802.1AR A secure Device Identity (DevID) in the form of an IEEE 802.1AR DevID
certificate [IEEE-802-1AR] must be provisioned in the Attester's certificate [IEEE-802-1AR] MUST be provisioned in the Attester's
TPMs. TPMs.
3.1.2. Keys 3.1.2. Keys
The Attestation Identity Key (AIK) and certificate must also be The Attestation Identity Key (AIK) and certificate MUST also be
provisioned on the Attester according to [Platform-DevID-TPM-2.0], provisioned on the Attester according to [Platform-DevID-TPM-2.0],
[PC-Client-BIOS-TPM-1.2], or [Platform-ID-TPM-1.2]. [PC-Client-BIOS-TPM-1.2], or [Platform-ID-TPM-1.2].
The Attester's TPM Keys must be associated with the DevID on the The Attester's TPM Keys MUST be associated with the DevID on the
Verifier (see Section 5 Security Considerations). Verifier (see [Platform-DevID-TPM-2.0] and Section 5 Security
Considerations, below).
3.1.3. Appraisal Policy for Evidence 3.1.3. Appraisal Policy for Evidence
(Editor's Note - terminology in this section must be brought back The Verifier MUST obtain trustworthy Endorsements in the form of
into line with the RATS Architecture definitions) reference measurements (e.g., Known Good Values, encoded as CoSWID
tags [I-D.birkholz-yang-swid]). These reference measurements will
The Verifier must obtain the Appraisal Policy for Evidence. This eventually be compared to signed PCR Evidence acquired from an
policy may be in the form of reference measurements (e.g., Known Good Attester's TPM using Attestation Policies chosen by the administrator
Values, CoSWID tags [I-D.birkholz-yang-swid]). These reference or owner of the device.
measurements will eventually be compared to signed PCR Evidence
acquired from an Attester's TPM.
This document does not specify the format or contents for the This document does not specify the format or contents for the
Appraisal Policy for Evidence. But acquiring this policy may happen Appraisal Policy for Evidence, but Endorsements may be acquired in
in one of two ways: one of two ways:
1. a Verifier obtains reference measurements directly from a 1. a Verifier may obtain reference measurements directly from an
Verifier Owner (i.e., a Device Configuration Authority) chosen by Endorser chosen by the Verifier administrator (e.g., through a
the Verifier administrator. web site).
2. Signed reference measurements may be distributed by the Verifier 2. Signed reference measurements may be distributed by the Endorser
Owner to the Attester. From there, the reference measurement may to the Attester, as part of a software update. From there, the
be acquired by the Verifier. reference measurement may be acquired by the Verifier.
In either case, the Verifier Owner MUST select the source of trusted
endorsements through the Appraisal Policy for Evidence.
************* .-------------. .-----------. ************* .-------------. .-----------.
* Verifier * | Attester | | Verifier/ | * Endorser * | Attester | | Verifier/ |
* Owner * | | | Relying | * * | | | Relying |
*(Device *----2--->| (Network |----2--->| Party | *(Device *----2--->| (Network |----2--->| Party |
* config * | Device) | |(Ntwk Mgmt | * config * | Device) | |(Ntwk Mgmt |
* Authority)* | | | Station) | * Authority)* | | | Station) |
************* '-------------' '-----------' ************* '-------------' '-----------'
| ^ | ^
| | | |
'----------------1--------------------------' '----------------1--------------------------'
Figure 4: Appraisal Policy for Evidence Prerequisites Figure 4: Appraisal Policy for Evidence Prerequisites
In either case the Appraisal Policy for Evidence must be generated, In either case the Endorsements must be generated, acquired and
acquired and delivered in a secure way. This includes reference delivered in a secure way, including reference measurements of
measurements of: firmware and bootable modules taken according to TCG PC Client
[PC-Client-BIOS-TPM-2.0] and Linux IMA [IMA]. Endorsementa MUST be
o firmware and bootable modules taken according to TCG PC Client encoded as SWID or CoSWID tags, signed by the device manufacturer, as
[PC-Client-BIOS-TPM-2.0] and Linux IMA [IMA] defined in the TCG RIM document [RIM], compatible with NIST IR 8060
[NIST-IR-8060] or the IETF CoSWID draft [I-D.ietf-sacm-coswid].
o encoded CoSWID tags signed by the device manufacturer, are as
defined in the TCG RIM document [RIM], compatible with NIST IR
8060 [NIST-IR-8060] and the IETF CoSWID draft
[I-D.ietf-sacm-coswid].
3.2. Reference Model for Challenge-Response 3.2. Reference Model for Challenge-Response
Once the prerequisites for RIV are met, a Verifier may acquire Once the prerequisites for RIV are met, a Verifier is able to acquire
Evidence from an Attester. The following diagram illustrates a RIV Evidence from an Attester. The following diagram illustrates a RIV
information flow between a Verifier and an Attester, derived from information flow between a Verifier and an Attester, derived from
Section 8.1 of [I-D.birkholz-rats-reference-interaction-model]. Section 8.1 of [I-D.birkholz-rats-reference-interaction-model].
Event times shown correspond to the time types described within Event times shown correspond to the time types described within
Appendix A of [I-D.ietf-rats-architecture]: Appendix A of [I-D.ietf-rats-architecture]:
.----------. .--------------------------. .----------. .--------------------------.
| Attester | | Relying Party / Verifier | | Attester | | Relying Party / Verifier |
'----------' '--------------------------' '----------' '--------------------------'
time(VG) | time(VG) |
skipping to change at page 20, line 30 skipping to change at page 21, line 30
| returnLogEvidence----------------------------------------> | | returnLogEvidence----------------------------------------> |
| | | |
| time(RG,RA) | time(RG,RA)
| evidenceAppraisal(SignedPcrEvidence, eventLog, refClaims) | evidenceAppraisal(SignedPcrEvidence, eventLog, refClaims)
| attestationResult <= | | attestationResult <= |
~ ~ ~ ~
| time(RX) | time(RX)
Figure 5: IETF Attestation Information Flow Figure 5: IETF Attestation Information Flow
o time(VG): One or more Attesting Network Device PCRs are extended o Step 1 (time(VG)): One or more Attesting Network Device PCRs are
with measurements. extended with measurements. RIV provides no direct link between
the time at which the event takes place and the time that it's
attested, although streaming attestation as in
[I-D.birkholz-rats-network-device-subscription] could.
o time(NS): The Verifier generates a unique nonce ("number used o Step 2 (time(NS)): The Verifier generates a unique nonce ("number
once"), and makes a request attestation data for one or more PCRs used once"), and makes a request attestation data for one or more
from an Attester. This can be accomplished via a YANG [RFC7950] PCRs from an Attester. For interoperability, this MUST be
interface that implements the TCG TAP model (e.g. YANG Module for accomplished via a YANG [RFC7950] interface that implements the
Basic Challenge-Response-based Remote Attestation Procedures TCG TAP model (e.g., YANG Module for Basic Challenge-Response-
based Remote Attestation Procedures
[I-D.ietf-rats-yang-tpm-charra]). [I-D.ietf-rats-yang-tpm-charra]).
o time(EG): On the Attester, measured values are retrieved from the o Step 3 (time(EG)): On the Attester, measured values are retrieved
Attester's TPM. This requested PCR evidence is signed by the from the Attester's TPM. This requested PCR evidence is signed by
Attestation Identity Key (AIK) associated with the DevID. Quotes the Attestation Identity Key (AIK) associated with the DevID.
are retrieved according to TCG TAP Information Model [TAP]. While Quotes are retrieved according to TCG TAP Information Model [TAP].
the TAP IM gives a protocol-independent description of the data While the TAP IM gives a protocol-independent description of the
elements involved, it's important to note that quotes from the TPM data elements involved, it's important to note that quotes from
are signed inside the TPM, so must be retrieved in a way that does the TPM are signed inside the TPM, so must be retrieved in a way
not invalidate the signature, as specified in that does not invalidate the signature, as specified in
[I-D.ietf-rats-yang-tpm-charra], to preserve the trust model. [I-D.ietf-rats-yang-tpm-charra], to preserve the trust model.
(See Section 5 Security Considerations). At the same time, the (See Section 5 Security Considerations). At the same time, the
Attester collects log evidence showing what values have been Attester collects log evidence showing what values have been
extended into that PCR. extended into that PCR.
o Collected Evidence is passed from the Attester to the Verifier o Step 4: Collected Evidence is passed from the Attester to the
Verifier
o time(RG,RA): The Verifier reviews the Evidence and takes action as o Step 5 (time(RG,RA)): The Verifier reviews the Evidence and takes
needed. As the Relying Party and Verifier are assumed co- action as needed. As the interaction between Relying Party and
resident, this can happen in one step. Verifier is out of scope for RIV, this can happen in one step.
* If the signed PCR values do not match the set of log entries * If the signed PCR values do not match the set of log entries
which have extended a particular PCR, the device should not be which have extended a particular PCR, the device SHOULD NOT be
trusted. trusted.
* If the log entries that the verifier considers important do not * If the log entries that the Verifier considers important do not
match known good values, the device should not be trusted. We match known good values, the device SHOULD NOT be trusted. We
note that the process of collecting and analyzing the log can note that the process of collecting and analyzing the log can
be omitted if the value in the relevant PCR is already a known- be omitted if the value in the relevant PCR is already a known-
good value. good value.
* If the set of log entries are not seen as acceptable by the * If the set of log entries are not seen as acceptable by the
Appraisal Policy for Evidence, the device should not be Appraisal Policy for Evidence, the device SHOULD NOT be
trusted. trusted.
* If the AIK signature is not correct, or freshness such as that * If the AIK signature is not correct, or freshness such as that
provided by the nonce is not included in the response, the provided by the nonce is not included in the response, the
device should not be trusted. device SHOULD NOT be trusted.
o time(RX): At some point after the verification of Evidence, the * If time(RG)-time(NS) is greater than the threshold in the
Attester can no longer be considered Attested as trustworthy. Appraisal Policy for Evidence, the Evidence is considered stale
and SHOULD NOT be trusted.
3.2.1. Transport and Encoding 3.2.1. Transport and Encoding
Network Management systems may retrieve signed PCR based Evidence as Network Management systems may retrieve signed PCR based Evidence as
shown in Figure 5, and can be accomplished via: shown in Figure 5, and can be accomplished via NETCONF or RESTCONF,
with XML, JSON, or CBOR encoded Evidence.
o XML, JSON, or CBOR encoded Evidence, using
o RESTCONF or NETCONF transport, over a
o TLS or SSH secure tunnel Implementations that use NETCONF MUST do so over a TLS or SSH secure
tunnel. Implementations that use RESTCONF transport MAY do so over a
TLS or SSH secure tunnel.
Retrieval of Log Evidence will be via log interfaces on the network Retrieval of Log Evidence SHOULD be via log interfaces on the network
device. (For example, see [I-D.ietf-rats-yang-tpm-charra]). device. (For example, see [I-D.ietf-rats-yang-tpm-charra]).
3.3. Centralized vs Peer-to-Peer 3.3. Centralized vs Peer-to-Peer
Figure 5 above assumes that the Verifier is implicitly trusted, while Figure 5 above assumes that the Verifier is implicitly trusted, while
the Attesting device is not. In a Peer-to-Peer application such as the Attesting device is not. In a Peer-to-Peer application such as
two routers negotiating a trust relationship two routers negotiating a trust relationship
[I-D.voit-rats-trusted-path-routing], the two peers can each ask the [I-D.voit-rats-trusted-path-routing], the two peers can each ask the
other to prove software integrity. In this application, the other to prove software integrity. In this application, the
information flow is the same, but each side plays a role both as an information flow is the same, but each side plays a role both as an
Attester and a Verifier. Each device issues a challenge, and each Attester and a Verifier. Each device issues a challenge, and each
device responds to the other's challenge, as shown in Figure 6. device responds to the other's challenge, as shown in Figure 6.
Peer-to-peer challenges, particularly if used to establish a trust Peer-to-peer challenges, particularly if used to establish a trust
relationship between routers, require devices to carry their own relationship between routers, require devices to carry their own
signed reference measurements (RIMs) so that each device has signed reference measurements (RIMs). Devices may also have to carry
everything needed for attestation, without having to resort to a Appraisal Policy for Evidence for each possible peer device so that
central authority. each device has everything needed for attestation, without having to
resort to a central authority.
+---------------+ +---------------+ +---------------+ +---------------+
| | | | | | | |
| Endorser A | | Endorser B | | Endorser A | | Endorser B |
| Firmware | | Firmware | | Firmware | | Firmware |
| Configuration | | Configuration | | Configuration | | Configuration |
| Authority | | Authority | | Authority | | Authority |
| | | | | | | |
+---------------+ +---------------+ +---------------+ +---------------+
| | | |
skipping to change at page 22, line 43 skipping to change at page 24, line 6
| Verifier |<------>| Attester |<-+ | Router A | Verifier |<------>| Attester |<-+ | Router A
| |<------>| | |- Challenges | |<------>| | |- Challenges
| | Step 2 | | | Router B | | Step 2 | | | Router B
| | | | | | | | | |
| |<-------| | | | |<-------| | |
+-------------+ Step 3 +------------+ / +-------------+ Step 3 +------------+ /
Figure 6: Peer-to-Peer Attestation Information Flow Figure 6: Peer-to-Peer Attestation Information Flow
In this application, each device may need to be equipped with signed In this application, each device may need to be equipped with signed
RIMs to act as an Attester, and also a selection of trusted x.509 RIMs to act as an Attester, and also an Appraisal Policy for Evidence
root certificates to allow the device to act as a Verifier. An and a selection of trusted X.509 root certificates, to allow the
existing link layer protocol such as 802.1x [IEEE-802.1x] or 802.1AE device to act as a Verifier. An existing link layer protocol such as
[IEEE-802.1ae], with Evidence being enclosed over a variant of EAP 802.1x [IEEE-802.1x] or 802.1AE [IEEE-802.1ae], with Evidence being
[RFC3748] or LLDP [LLDP] are suitable methods for such an exchange. enclosed over a variant of EAP [RFC3748] or LLDP [LLDP] are suitable
methods for such an exchange.
4. Privacy Considerations 4. Privacy Considerations
Networking Equipment, such as routers, switches and firewalls, has a Networking Equipment, such as routers, switches and firewalls, has a
key role to play in guarding the privacy of individuals using the key role to play in guarding the privacy of individuals using the
network: network:
o Packets passing through the device must not be sent to o Packets passing through the device must not be sent to
unauthorized destinations. For example: unauthorized destinations. For example:
skipping to change at page 23, line 42 skipping to change at page 24, line 50
configuration and measured device state (for example, PCR values), to configuration and measured device state (for example, PCR values), to
the Equipment's Administrator, so there's no uncertainty as to what the Equipment's Administrator, so there's no uncertainty as to what
function each device and configuration is configured to carry out. function each device and configuration is configured to carry out.
This allows the administrator to ensure that the network provides This allows the administrator to ensure that the network provides
individual and peer privacy guarantees. individual and peer privacy guarantees.
RIV specifically addresses the collection of information from RIV specifically addresses the collection of information from
enterprise network devices by authorized agents of the enterprise. enterprise network devices by authorized agents of the enterprise.
As such, privacy is a fundamental concern for those deploying this As such, privacy is a fundamental concern for those deploying this
solution, given EU GDPR, California CCPA, and many other privacy solution, given EU GDPR, California CCPA, and many other privacy
regulations. The enterprise should implement and enforce their duty regulations. The enterprise SHOULD implement and enforce their duty
of care. of care.
See [NetEq] for more context on privacy in networking devices See [NetEq] for more context on privacy in networking devices.
5. Security Considerations 5. Security Considerations
Attestation results from the RIV procedure are subject to a number of Attestation Results from the RIV procedure are subject to a number of
attacks: attacks:
o Keys may be compromised o Keys may be compromised.
o A counterfeit device may attempt to impersonate (spoof) a known o A counterfeit device may attempt to impersonate (spoof) a known
authentic device authentic device.
o Man-in-the-middle attacks may be used by a counterfeit device to o Man-in-the-middle attacks may be used by a counterfeit device to
attempt to deliver responses that originate in an actual authentic attempt to deliver responses that originate in an actual authentic
device device.
o Replay attacks may be attempted by a compromised device o Replay attacks may be attempted by a compromised device.
5.1. Keys Used in RIV 5.1. Keys Used in RIV
Trustworthiness of RIV attestation depends strongly on the validity Trustworthiness of RIV attestation depends strongly on the validity
of keys used for identity and attestation reports. RIV takes full of keys used for identity and attestation reports. RIV takes full
advantage of TPM capabilities to ensure that results can be trusted. advantage of TPM capabilities to ensure that results can be trusted.
Two sets of keys are relevant to RIV attestation Two sets of keys are relevant to RIV attestation:
o A DevID key is used to certify the identity of the device in which o A DevID key is used to certify the identity of the device in which
the TPM is installed. the TPM is installed.
o An Attestation Key (AK) key signs attestation reports, (called o An Attestation Key (AK) key signs attestation reports (called
'quotes' in TCG documents), used to provide evidence for integrity 'quotes' in TCG documents), used to provide evidence for integrity
of the software on the device. of the software on the device.
TPM practices usually require that these keys be different, as a way TPM practices usually require that these keys be different, as a way
of ensuring that a general-purpose signing key cannot be used to of ensuring that a general-purpose signing key cannot be used to
spoof an attestation quote. spoof an attestation quote.
In each case, the private half of the key is known only to the TPM, In each case, the private half of the key is known only to the TPM,
and cannot be retrieved externally, even by a trusted party. To and cannot be retrieved externally, even by a trusted party. To
ensure that's the case, specification-compliant private/public key- ensure that's the case, specification-compliant private/public key-
pairs are generated inside the TPM, where they're never exposed, and pairs are generated inside the TPM, where they're never exposed, and
cannot be extracted (See [Platform-DevID-TPM-2.0]). cannot be extracted (See [Platform-DevID-TPM-2.0]).
Keeping keys safe is just part of attestation security; knowing which Keeping keys safe is just part of attestation security; knowing which
keys are bound to the device in question is just as important. keys are bound to the device in question is just as important.
While there are many ways to manage keys in a TPM (See While there are many ways to manage keys in a TPM (see
[Platform-DevID-TPM-2.0]), RIV includes support for "zero touch" [Platform-DevID-TPM-2.0]), RIV includes support for "zero touch"
provisioning (also known as zero-touch onboarding) of fielded devices provisioning (also known as zero-touch onboarding) of fielded devices
(e.g. Secure ZTP, [RFC8572]), where keys which have predictable (e.g., Secure ZTP, [RFC8572]), where keys which have predictable
trust properties are provisioned by the device vendor. trust properties are provisioned by the device vendor.
Device identity in RIV is based on IEEE 802.1AR DevID. This Device identity in RIV is based on IEEE 802.1AR Device Identity
specification provides several elements (DevID). This specification provides several elements:
o A DevID requires a unique key pair for each device, accompanied by o A DevID requires a unique key pair for each device, accompanied by
an x.509 certificate an X.509 certificate,
o The private portion of the DevID key is to be stored in the o The private portion of the DevID key is to be stored in the
device, in a manner that provides confidentiality (Section 6.2.5 device, in a manner that provides confidentiality (Section 6.2.5
[IEEE-802-1AR]) [IEEE-802-1AR])
The x.509 certificate contains several components The X.509 certificate contains several components:
o The public part of the unique DevID key assigned to that device o The public part of the unique DevID key assigned to that device
allows a challenge of identity.
o An identifying string that's unique to the manufacturer of the o An identifying string that's unique to the manufacturer of the
device. This is normally the serial number of the unit, which device. This is normally the serial number of the unit, which
might also be printed on a label on the device. might also be printed on a label on the device.
o The certificate must be signed by a key traceable to the o The certificate must be signed by a key traceable to the
manufacturer's root key. manufacturer's root key.
With these elements, the device's manufacturer and serial number can With these elements, the device's manufacturer and serial number can
be identified by analyzing the DevID certificate plus the chain of be identified by analyzing the DevID certificate plus the chain of
intermediate certs leading back to the manufacturer's root intermediate certificates leading back to the manufacturer's root
certificate. As is conventional in TLS connections, a nonce must be certificate. As is conventional in TLS or SSH connections, a nonce
signed by the device in response to a challenge, proving possession must be signed by the device in response to a challenge, proving
of its DevID private key. possession of its DevID private key.
RIV uses the DevID to validate a TLS connection to the device as the RIV uses the DevID to validate a TLS or SSH connection to the device
attestation session begins. Security of this process derives from as the attestation session begins. Security of this process derives
TLS security, with the DevID providing proof that the TLS session from TLS or SSH security, with the DevID providing proof that the
terminates on the intended device. [RFC8446]. session terminates on the intended device. See [RFC8446], [RFC4253].
Evidence of software integrity is delivered in the form of a quote Evidence of software integrity is delivered in the form of a quote
signed by the TPM itself. Because the contents of the quote are signed by the TPM itself. Because the contents of the quote are
signed inside the TPM, any external modification (including signed inside the TPM, any external modification (including
reformatting to a different data format) will be detected as reformatting to a different data format) after measurements have been
tampering. taken will be detected as tampering. An unbroken chain of trust is
essential to ensuring that blocks of code that are taking
measurements have been verified before execution (see Figure 1.
Requiring results of attestation of the operating software to be Requiring results of attestation of the operating software to be
signed by a key known only to the TPM also removes the need to trust signed by a key known only to the TPM also removes the need to trust
the device's operating software (beyond the first measurement; see the device's operating software (beyond the first measurement; see
below); any changes to the quote, generated and signed by the TPM 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 itself, made by malicious device software, or in the path back to the
verifier, will invalidate the signature on the quote. Verifier, will invalidate the signature on the quote.
A critical feature of the YANG model described in A critical feature of the YANG model described in
[I-D.ietf-rats-yang-tpm-charra] is the ability to carry TPM data [I-D.ietf-rats-yang-tpm-charra] is the ability to carry TPM data
structures in their native format, without requiring any changes to structures in their native format, without requiring any changes to
the structures as they were signed and delivered by the TPM. While the structures as they were signed and delivered by the TPM. While
alternate methods of conveying TPM quotes could compress out alternate methods of conveying TPM quotes could compress out
redundant information, or add an additional layer of signing using redundant information, or add an additional layer of signing using
external keys, the important part is to preserve the TPM signing, so external keys, the implementation MUST preserve the TPM signing, so
that tampering anywhere in the path between the TPM itself and the that tampering anywhere in the path between the TPM itself and the
Verifier can be detected. Verifier can be detected.
5.2. Prevention of Spoofing and Man-in-the-Middle Attacks 5.2. Prevention of Spoofing and Man-in-the-Middle Attacks
Prevention of spoofing attacks against attestation systems is also Prevention of spoofing attacks against attestation systems is also
important. There are two cases to consider: important. There are two cases to consider:
o The entire device could be spoofed, that is, when the Verifier o The entire device could be spoofed, that is, when the Verifier
goes to verify a specific device, it might be redirected to a goes to verify a specific device, it might be redirected to a
different device. Use of the 802.1AR identity in the TPM ensures different device. Use of the 802.1AR Device Identity (DevID) in
that the Verifier's TLS session is in fact terminating on the the TPM ensures that the Verifier's TLS or SSH session is in fact
right device. terminating on the right device.
o A compromised device could respond with a spoofed attestation o A compromised device could respond with a spoofed Attestation
result, that is, a compromised OS could return a fabricated quote. Result, that is, a compromised OS could return a fabricated quote.
Protection against spoofed quotes from a device with valid identity Protection against spoofed quotes from a device with valid identity
is a bit more complex. An identity key must be available to sign any is a bit more complex. An identity key must be available to sign any
kind of nonce or hash offered by the verifier, and consequently, kind of nonce or hash offered by the Verifier, and consequently,
could be used to sign a fabricated quote. To block spoofed could be used to sign a fabricated quote. To block a spoofed
attestation result, the quote generated inside the TPM must be signed Attestation Result, the quote generated inside the TPM must be signed
by a key that's different from the DevID, called an Attestation Key by a key that's different from the DevID, called an Attestation Key
(AK). (AK).
Given separate Attestation and DevID keys, the binding between the AK Given separate Attestation and DevID keys, the binding between the AK
and the same device must also be proven to prevent a man-in-the- and the same device must also be proven to prevent a man-in-the-
middle attack (e.g. the 'Asokan Attack' [RFC6813]). middle attack (e.g., the 'Asokan Attack' [RFC6813]).
This is accomplished in RIV through use of an AK certificate with the This is accomplished in RIV through use of an AK certificate with the
same elements as the DevID (i.e., same manufacturer's serial number, same elements as the DevID (i.e., same manufacturer's serial number,
signed by the same manufacturer's key), but containing the device's signed by the same manufacturer's key), but containing the device's
unique AK public key instead of the DevID public key. unique AK public key instead of the DevID public key.
[Editor's Note: does this require an OID that says the key is known [Editor's Note: does this require an OID that says the key is known
by the CA to be an Attestation key?] by the CA to be an Attestation key?]
These two keys and certificates are used together: These two keys and certificates are used together:
o The DevID is used to validate a TLS connection terminating on the o The DevID is used to validate a TLS connection terminating on the
device with a known serial number. device with a known serial number.
o The AK is used to sign attestation quotes, providing proof that o The AK is used to sign attestation quotes, providing proof that
the attestation evidence comes from the same device. the attestation evidence comes from the same device.
5.3. Replay Attacks 5.3. Replay Attacks
skipping to change at page 27, line 12 skipping to change at page 28, line 19
o The AK is used to sign attestation quotes, providing proof that o The AK is used to sign attestation quotes, providing proof that
the attestation evidence comes from the same device. the attestation evidence comes from the same device.
5.3. Replay Attacks 5.3. Replay Attacks
Replay attacks, where results of a previous attestation are submitted Replay attacks, where results of a previous attestation are submitted
in response to subsequent requests, are usually prevented by in response to subsequent requests, are usually prevented by
inclusion of a nonce in the request to the TPM for a quote. Each inclusion of a nonce in the request to the TPM for a quote. Each
request from the Verifier includes a new random number (a nonce). request from the Verifier includes a new random number (a nonce).
The resulting quote signed by the TPM contains the same nonce, The resulting quote signed by the TPM contains the same nonce,
allowing the verifier to determine freshness, i.e., that the allowing the Verifier to determine freshness, (i.e., that the
resulting quote was generated in response to the verifier's specific resulting quote was generated in response to the Verifier's specific
request. Time-Based Uni-directional Attestation request). Time-Based Uni-directional Attestation
[I-D.birkholz-rats-tuda] provides an alternate mechanism to verify [I-D.birkholz-rats-tuda] provides an alternate mechanism to verify
freshness without requiring a request/response cycle. freshness without requiring a request/response cycle.
5.4. Owner-Signed Keys 5.4. Owner-Signed Keys
Although RIV recommends that device manufacturers pre-provision Although device manufacturers MUST pre-provision devices with easily
devices with easily-verified DevID and AK certs, use of those verified DevID and AK certificates, use of those credentials is not
credentials is not mandatory. IEEE 802.1AR incorporates the idea of mandatory. IEEE 802.1AR incorporates the idea of an Initial Device
an Initial Device ID (IDevID), provisioned by the manufacturer, and a ID (IDevID), provisioned by the manufacturer, and a Local Device ID
Local Device ID (LDevID) provisioned by the owner of the device. RIV (LDevID) provisioned by the owner of the device. RIV and
extends that concept by defining an Initial Attestation Key (IAK) and [Platform-DevID-TPM-2.0] extends that concept by defining an Initial
Local Attestation Key (LAK) with the same properties. Attestation Key (IAK) and Local Attestation Key (LAK) with the same
properties.
Device owners can use any method to provision the Local credentials. Device owners can use any method to provision the Local credentials.
o TCG document [Platform-DevID-TPM-2.0] shows how the initial o The TCG document [Platform-DevID-TPM-2.0] shows how the initial
Attestation keys can be used to certify LDevID and LAK keys. Use Attestation keys can be used to certify LDevID and LAK keys. Use
of the LDevID and LAK allows the device owner to use a uniform of the LDevID and LAK allows the device owner to use a uniform
identity structure across device types from multiple manufacturers identity structure across device types from multiple manufacturers
(in the same way that an "Asset Tag" is used by many enterprises (in the same way that an "Asset Tag" is used by many enterprises
to identify devices they own). TCG doc [Provisioning-TPM-2.0] to identify devices they own). The TCG document
also contains guidance on provisioning identity keys in TPM 2.0. [Provisioning-TPM-2.0] also contains guidance on provisioning
identity keys in TPM 2.0.
o But device owners can use any other mechanism they want to assure o Device owners, however, can use any other mechanism they want to
themselves that Local identity certificates are inserted into the assure themselves that Local identity certificates are inserted
intended device, including physical inspection and programming in into the intended device, including physical inspection and
a secure location, if they prefer to avoid placing trust in the programming in a secure location, if they prefer to avoid placing
manufacturer-provided keys. trust in the manufacturer-provided keys.
Clearly, Local keys can't be used for secure Zero Touch provisioning; Clearly, Local keys can't be used for secure Zero Touch provisioning;
installation of the Local keys can only be done by some process that installation of the Local keys can only be done by some process that
runs before the device is configured for network operation. runs before the device is installed for network operation.
On the other end of the device life cycle, provision should be made On the other end of the device life cycle, provision should be made
to wipe Local keys when a device is decommissioned, to indicate that to wipe Local keys when a device is decommissioned, to indicate that
the device is no longer owned by the enterprise. The manufacturer's the device is no longer owned by the enterprise. The manufacturer's
Initial identity keys must be preserved, as they contain no Initial identity keys must be preserved, as they contain no
information that's not already printed on the device's serial number information that's not already printed on the device's serial number
plate. plate.
5.5. Other Trust Anchors 5.5. Other Trust Anchors
In addition to trustworthy provisioning of keys, RIV depends on other In addition to trustworthy provisioning of keys, RIV depends on other
trust anchors. (See [SP800-155] for definitions of Roots of Trust.) trust anchors. (See [SP800-155] for definitions of Roots of Trust.)
o Secure identity depends on mechanisms to prevent per-device secret o Secure identity depends on mechanisms to prevent per-device secret
keys from being compromised. The TPM provides this capability as keys from being compromised. The TPM provides this capability as
a Root of Trust for Storage a Root of Trust for Storage.
o Attestation depends on an unbroken chain of measurements, starting o Attestation depends on an unbroken chain of measurements, starting
from the very first measurement. That first measurement is made from the very first measurement. That first measurement is made
by code called the Root of Trust for Measurement, typically done by code called the Root of Trust for Measurement, typically done
by trusted firmware stored in boot flash. Mechanisms for by trusted firmware stored in boot flash. Mechanisms for
maintaining the trustworthiness of the RTM are out of scope for maintaining the trustworthiness of the RTM are out of scope for
RIV, but could include immutable firmware, signed updates, or a RIV, but could include immutable firmware, signed updates, or a
vendor-specific hardware verification technique. vendor-specific hardware verification technique. See Section 8.1
for background on TPM practices.
o RIV assumes some level of physical defense for the device. If a o The device owner SHOULD provide some level of physical defense for
TPM that has already been programmed with an authentic DevID is the device. If a TPM that has already been programmed with an
stolen and inserted into a counterfeit device, attestation of that authentic DevID is stolen and inserted into a counterfeit device,
counterfeit device may become indistinguishable from an authentic attestation of that counterfeit device may become
device. indistinguishable from an authentic device.
RIV also depends on reliable reference measurements, as expressed by RIV also depends on reliable reference measurements, as expressed by
the RIM [RIM]. The definition of trust procedures for RIMs is out of the RIM [RIM]. The definition of trust procedures for RIMs is out of
scope for RIV, and the device owner is free to use any policy to scope for RIV, and the device owner is free to use any policy to
validate a set of reference measurements. RIMs may be conveyed out- validate a set of reference measurements. RIMs may be conveyed out-
of-band or in-band, as part of the attestation process (see of-band or in-band, as part of the attestation process (see
Section 3.1.3). But for embedded devices, where software is usually Section 3.1.3). But for embedded devices, where software is usually
shipped as a self-contained package, RIMs signed by the manufacturer shipped as a self-contained package, RIMs signed by the manufacturer
and delivered in-band may be more convenient for the device owner. and delivered in-band may be more convenient for the device owner.
The validity of RIV attestation results is also influenced by The validity of RIV attestation results is also influenced by
procedures used to create reference measurements: procedures used to create reference measurements:
o While the RIM itself is signed, supply-chains must be carefully o While the RIM itself is signed, supply-chains SHOULD be carefully
scrutinized to ensure that the values are not subject to scrutinized to ensure that the values are not subject to
unexpected manipulation prior to signing. Insider-attacks against unexpected manipulation prior to signing. Insider-attacks against
code bases and build chains are particularly hard to spot. code bases and build chains are particularly hard to spot.
o Designers must guard against hash collision attacks. Reference o Designers SHOULD guard against hash collision attacks. Reference
measurements often give hashes for large objects of indeterminate Integrity Measurements often give hashes for large objects of
size; if one of the measured objects can be replaced with an indeterminate size; if one of the measured objects can be replaced
implant engineered to produce the same hash, RIV will be unable to with an implant engineered to produce the same hash, RIV will be
detect the substitution. TPM1.2 uses SHA-1 hashes only, which unable to detect the substitution. TPM1.2 uses SHA-1 hashes only,
have been shown to be susceptible to collision attack. TPM2.0 which have been shown to be susceptible to collision attack.
will produce quotes with SHA-256, which so far has resisted such TPM2.0 will produce quotes with SHA-256, which so far has resisted
attacks, and consequently is preferred. such attacks. Consequently RIV implementations SHOULD use TPM2.0.
6. Conclusion 6. Conclusion
TCG technologies can play an important part in the implementation of TCG technologies can play an important part in the implementation of
Remote Integrity Verification. Standards for many of the components Remote Integrity Verification. Standards for many of the components
needed for implementation of RIV already exist: needed for implementation of RIV already exist:
o Platform identity can be based on IEEE 802.1AR Device identity, o Platform identity can be based on IEEE 802.1AR Device Identity,
coupled with careful supply-chain management by the manufacturer. coupled with careful supply-chain management by the manufacturer.
o Complex supply chains can be certified using TCG Platform o Complex supply chains can be certified using TCG Platform
Certificates [Platform-Certificates] Certificates [Platform-Certificates].
o The TCG TAP mechanism can be used to retrieve attestation o The TCG TAP mechanism can be used to retrieve attestation
evidence. Work is needed on a YANG model for this protocol. evidence. Work is needed on a YANG model for this protocol.
o Reference Measurements must be conveyed from the software o Reference Integrity Measurements must be conveyed from the
authority (e.g., the manufacturer) to the system in which software authority (e.g., the manufacturer) to the system in which
verification will take place. IETF CoSWID work forms the basis verification will take place. IETF CoSWID work forms the basis
for this, but new work is needed to create an information model for this, but new work is needed to create an information model
and YANG implementation. and YANG implementation.
7. IANA Considerations 7. IANA Considerations
This memo includes no request to IANA. This memo includes no request to IANA.
8. Appendix 8. Appendix
8.1. Layering Model for Network Equipment Attester and Verifier 8.1. Using a TPM for Attestation
The Trusted Platform Module and surrounding ecosystem provide three
interlocking capabilities to enable secure collection of evidence
from a remote device, Platform Configuration Registers (PCRs), a
Quote mechanism, and a standardized Event Log.
Each TPM has at least between eight and twenty-four PCRs (depending
on the profile and vendor choices), each one large 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
outside the chip, but the TPM interface provides a way to "extend" a
new security measurement hash into any PCR, a process by which the
existing value in the PCR is hashed with the new security measurement
hash, and the result placed back into the same PCR. The result is a
composite fingerprint of all the security measurements extended into
each PCR since the system was reset.
Every time a PCR is extended, an entry should be added to the
corresponding Event Log. Logs contain the security measurement hash
plus informative fields offering hints as to what event it was that
generated the security measurement.
The Event Log itself is protected against accidental manipulation,
but it is implicitly tamper-evident - any verification process can
read the security measurement hash from the log events, compute the
composite value and compare that to what ended up in the PCR. If
there's a discrepancy, the logs do not provide an accurate view of
what was placed into the PCR.
In a conventional TPM Attestation environment, the first measurement
must be made and extended into the TPM by trusted device code (called
the Root of Trust for Measurement, RTM). That first measurement
should cover the segment of code that is run immediately after the
RTM, which then measures the next code segment before running it, and
so on, forming an unbroken chain of trust. See [TCGRoT] for more on
Mutable vs Immutable roots of trust.
The TPM provides another mechanism called a Quote that can read the
current value of the PCRs and package them into a data structure
signed by an Attestation Key (which is private key that is known only
to the TPM).
The Verifier uses the Quote and Log together. The Quote, containing
the composite hash of the complete sequence of security measurement
hashes, is used to verify the integrity of the Event Log. Each hash
in the validated Quote can then be compared to corresponding expected
values in the set of Reference Integrity Measurements to validate
overall system integrity.
A summary of information exchanged in obtaining quotes from TPM1.2
and TPM2.0 can be found in [TAP], Section 4. Detailed information
about PCRs and Quote data structures can be found in [TPM1.2],
[TPM2.0]. Recommended log formats include [PC-Client-BIOS-TPM-2.0]
and [Canonical-Event-Log].
8.2. Root of Trust for Measurement
The measurements needed for attestation require that the device being
attested 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 to attest that each stage of system
startup is verified, a Root of Trust for Storage (i.e., the TPM PCRs)
to record the results, and a Root of Trust for Reporting to report
the results [TCGRoT], [SP800-155].
While there are many complex aspects of a Root of Trust, two aspects
that are important in the case of attestation are:
o The first measurement computed by the Root of Trust for
Measurement, and stored in the TPM's Root of Trust for Storage, is
presumed to be correct.
o There must not be a way to reset the Root of Trust for Storage
without re-entering the Root of Trust for Measurement code.
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 be trusted. (See [NIST-SP-800-155])
8.3. Layering Model for Network Equipment Attester and Verifier
Retrieval of identity and attestation state uses one protocol stack, Retrieval of identity and attestation state uses one protocol stack,
while retrieval of Reference Measurements uses a different set of while retrieval of Reference Measurements uses a different set of
protocols. Figure 5 shows the components involved. protocols. Figure 5 shows the components involved.
+-----------------------+ +-------------------------+ +-----------------------+ +-------------------------+
| | | | | | | |
| Attester |<-------------| Verifier | | Attester |<-------------| Verifier |
| (Device) |------------->| (Management Station) | | (Device) |------------->| (Management Station) |
| | | | | | | | | |
skipping to change at page 30, line 50 skipping to change at page 33, line 50
* RESTCONF/NETCONF * * RESTCONF/NETCONF * * RESTCONF/NETCONF * * RESTCONF/NETCONF *
************************ ************************* ************************ *************************
************************* ************************ ************************* ************************
* TLS, SSH * * TLS, SSH * * TLS, SSH * * TLS, SSH *
************************* ************************ ************************* ************************
Figure 7: RIV Protocol Stacks Figure 7: RIV Protocol Stacks
IETF documents are captured in boxes surrounded by asterisks. TCG IETF documents are captured in boxes surrounded by asterisks. TCG
documents are shown in boxes surrounded by dots. The IETF documents are shown in boxes surrounded by dots.
Attestation Reference Interaction Diagram, Reference Integrity
Manifest, TAP Information Model and Canonical Log Format, and both
YANG modules are works in progress. Information Model layers
describe abstract data objects that can be requested, and the
corresponding response SNMP is still widely used, but the industry is
transitioning to YANG, so in some cases, both will be required. TLS
Authentication with TPM has been shown to work; SSH authentication
using TPM-protected keys is not as easily done [as of 2019]
8.1.1. Why is OS Attestation Different? 8.3.1. Why is OS Attestation Different?
Even in embedded systems, adding Attestation at the OS level (e.g. Even in embedded systems, adding Attestation at the OS level (e.g.,
Linux IMA, Integrity Measurement Architecture [IMA]) increases the Linux IMA, Integrity Measurement Architecture [IMA]) increases the
number of objects to be attested by one or two orders of magnitude, number of objects to be attested by one or two orders of magnitude,
involves software that's updated and changed frequently, and involves software that's updated and changed frequently, and
introduces processes that begin in an unpredictable order. introduces processes that begin in an unpredictable order.
TCG and others (including the Linux community) are working on methods TCG and others (including the Linux community) are working on methods
and procedures for attesting the operating system and application and procedures for attesting the operating system and application
software, but standardization is still in process. software, but standardization is still in process.
8.2. Implementation Notes 8.4. Implementation Notes
Table 1 summarizes many of the actions needed to complete an Figure 8 summarizes many of the actions needed to complete an
Attestation system, with links to relevant documents. While Attestation system, with links to relevant documents. While
documents are controlled by several standards organizations, the documents are controlled by several standards organizations, the
implied actions required for implementation are all the implied actions required for implementation are all the
responsibility of the manufacturer of the device, unless otherwise responsibility of the manufacturer of the device, unless otherwise
noted. noted. It should be noted that, while the YANG model is RECOMMENDED
for attestation, this table identifies an optional SNMP MIB as well,
+------------------------------------------------------------------+ [Attest-MIB].
| 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 | TCG TPM DevID |
| 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 |
| | simply |
| | configuring TLS|
| | to use the |
| | DevID as its |
| | trust anchor.) |
--------------------------------------------------------------------
| Make CoSWID tags for BIOS/LoaderLKernel 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.birkholz-yang-swid}}|
| as https://github.com/Labs64/swid-maven-plugin |
| 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 TAP to SNMP | TCG SNMP MIB |
| 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. | |
--------------------------------------------------------------------
+------------------------------------------------------------------+
| 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 | TCG TPM DevID |
| 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 |
| | simply |
| | configuring TLS|
| | to use the |
| | DevID as its |
| | trust anchor.) |
--------------------------------------------------------------------
| Make CoSWID tags for BIOS/LoaderLKernel 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 | draft-birkholz-yang-swid|
| 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 TAP to SNMP | TCG SNMP MIB |
| 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. | |
--------------------------------------------------------------------
Figure 8: Component Status Figure 8: Component Status
8.3. Root of Trust for Measurement 9. References
The measurements needed for attestation require that the device being 9.1. Normative References
attested is equipped with a Root of Trust for Measurement, i.e., some
trustworthy 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 Storage (i.e., the TPM PCRs) to
record the results, and a Root of Trust for Reporting to report the
results [TCGRoT], [SP800-155].
While there are many complex aspects of a Root of Trust, two aspects [Canonical-Event-Log]
that are important in the case of attestation are: Trusted Computing Group, "DRAFT Canonical Event Log Format
Version: 1.0, Revision: .12", October 2018.
o The first measurement computed by the Root of Trust for [I-D.birkholz-yang-swid]
Measurement, and stored in the TPM's Root of Trust for Storage, is Birkholz, H., "Software Inventory YANG module based on
presumed to be correct. Software Identifiers", draft-birkholz-yang-swid-02 (work
in progress), October 2018.
o There must not be a way to reset the Root of Trust for Storage [I-D.ietf-rats-yang-tpm-charra]
without re-entering the Root of Trust for Measurement code. Birkholz, H., Eckel, M., Bhandari, S., Sulzen, B., Voit,
E., Xia, L., Laffey, T., and G. Fedorkow, "A YANG Data
Model for Challenge-Response-based Remote Attestation
Procedures using TPMs", draft-ietf-rats-yang-tpm-charra-02
(work in progress), June 2020.
The first measurement must be computed by code that is implicitly [I-D.ietf-sacm-coswid]
trusted; if that first measurement can be subverted, none of the Birkholz, H., Fitzgerald-McKay, J., Schmidt, C., and D.
remaining measurements can be trusted. (See [NIST-SP-800-155]) Waltermire, "Concise Software Identification Tags", draft-
ietf-sacm-coswid-15 (work in progress), May 2020.
9. Informative References [IEEE-802-1AR]
Seaman, M., "802.1AR-2018 - IEEE Standard for Local and
Metropolitan Area Networks - Secure Device Identity, IEEE
Computer Society", August 2018.
[PC-Client-BIOS-TPM-1.2]
Trusted Computing Group, "TCG PC Client Specific
Implementation Specification for Conventional BIOS,
Specification Version 1.21 Errata, Revision 1.00",
February 2012,
<https://trustedcomputinggroup.org/resource/pc-client-
work-group-specific-implementation-specification-for-
conventional-bios/>.
[PC-Client-BIOS-TPM-2.0]
Trusted Computing Group, "PC Client Specific Platform
Firmware Profile Specification Family "2.0", Level 00
Revision 1.04", June 2019,
<https://trustedcomputinggroup.org/pc-client-specific-
platform-firmware-profile-specification>.
[PC-Client-RIM]
Trusted Computing Group, "DRAFT: TCG PC Client Reference
Integrity Manifest Specification, v.09", December 2019,
<https://trustedcomputinggroup.org/wp-content/uploads/
TCG_PC_Client_RIM_r0p15_15june2020.pdf>.
[Platform-DevID-TPM-2.0]
Trusted Computing Group, "DRAFT: TPM Keys for Platform
DevID for TPM2, Specification Version 0.7, Revision 0",
October 2018.
[Platform-ID-TPM-1.2]
Trusted Computing Group, "TPM Keys for Platform Identity
for TPM 1.2, Specification Version 1.0, Revision 3",
August 2015, <https://trustedcomputinggroup.org/resource/
tpm-keys-for-platform-identity-for-tpm-1-2-2/>.
[RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253,
January 2006, <https://www.rfc-editor.org/info/rfc4253>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC8572] Watsen, K., Farrer, I., and M. Abrahamsson, "Secure Zero
Touch Provisioning (SZTP)", RFC 8572,
DOI 10.17487/RFC8572, April 2019,
<https://www.rfc-editor.org/info/rfc8572>.
[RIM] Trusted Computing Group, "DRAFT: TCG Reference Integrity
Manifest Information Model", June 2019,
<https://trustedcomputinggroup.org/wp-content/uploads/
TCG_RIM_Model_v1-r13_2feb20.pdf>.
[SWID] The International Organization for Standardization/
International Electrotechnical Commission, "Information
Technology Software Asset Management Part 2: Software
Identification Tag, ISO/IEC 19770-2", October 2015,
<https://www.iso.org/standard/65666.html>.
[TAP] Trusted Computing Group, "TCG Trusted Attestation Protocol
(TAP) Information Model for TPM Families 1.2 and 2.0 and
DICE Family 1.0, Version 1.0, Revision 0.36", October
2018, <https://trustedcomputinggroup.org/resource/tcg-tap-
information-model/>.
9.2. Informative References
[AIK-Enrollment] [AIK-Enrollment]
Trusted Computing Group, "TCG Infrastructure Working Group Trusted Computing Group, "TCG Infrastructure Working Group
- A CMC Profile for AIK Certificate Enrollment Version - A CMC Profile for AIK Certificate Enrollment Version
1.0, Revision 7", March 2011, 1.0, Revision 7", March 2011,
<https://trustedcomputinggroup.org/resource/tcg- <https://trustedcomputinggroup.org/resource/tcg-
infrastructure-working-group-a-cmc-profile-for-aik- infrastructure-working-group-a-cmc-profile-for-aik-
certificate-enrollment/>. certificate-enrollment/>.
[Canonical-Event-Log] [Attest-MIB]
Trusted Computing Group, "DRAFT Canonical Event Log Format Trusted Computing Group, "SNMP MIB for TPM-Based
Version: 1.0, Revision: .12", October 2018. Attestation, Version 0.8Revision 0.02", May 2018,
<https://trustedcomputinggroup.org/wp-content/uploads/
TCG_SNMP_MIB_for_TPM-
Based_Attestation_v0.8r2_PUBLIC_REVIEW.pdf>.
[EFI-TPM] Trusted Computing Group, "TCG EFI Platform Specification [EFI-TPM] Trusted Computing Group, "TCG EFI Platform Specification
for TPM Family 1.1 or 1.2, Specification Version 1.22, for TPM Family 1.1 or 1.2, Specification Version 1.22,
Revision 15", January 2014, Revision 15", January 2014,
<https://trustedcomputinggroup.org/resource/tcg-efi- <https://trustedcomputinggroup.org/resource/tcg-efi-
platform-specification/>. platform-specification/>.
[I-D.birkholz-rats-network-device-subscription]
Birkholz, H., Voit, E., and W. Pan, "Attestation Event
Stream Subscription", draft-birkholz-rats-network-device-
subscription-00 (work in progress), June 2020.
[I-D.birkholz-rats-reference-interaction-model] [I-D.birkholz-rats-reference-interaction-model]
Birkholz, H., Eckel, M., Newton, C., and L. Chen, Birkholz, H., Eckel, M., Newton, C., and L. Chen,
"Reference Interaction Models for Remote Attestation "Reference Interaction Models for Remote Attestation
Procedures", draft-birkholz-rats-reference-interaction- Procedures", draft-birkholz-rats-reference-interaction-
model-03 (work in progress), July 2020. model-03 (work in progress), July 2020.
[I-D.birkholz-rats-tuda] [I-D.birkholz-rats-tuda]
Fuchs, A., Birkholz, H., McDonald, I., and C. Bormann, Fuchs, A., Birkholz, H., McDonald, I., and C. Bormann,
"Time-Based Uni-Directional Attestation", draft-birkholz- "Time-Based Uni-Directional Attestation", draft-birkholz-
rats-tuda-03 (work in progress), July 2020. rats-tuda-03 (work in progress), July 2020.
[I-D.birkholz-yang-swid]
Birkholz, H., "Software Inventory YANG module based on
Software Identifiers", draft-birkholz-yang-swid-02 (work
in progress), October 2018.
[I-D.ietf-rats-architecture] [I-D.ietf-rats-architecture]
Birkholz, H., Thaler, D., Richardson, M., Smith, N., and Birkholz, H., Thaler, D., Richardson, M., Smith, N., and
W. Pan, "Remote Attestation Procedures Architecture", W. Pan, "Remote Attestation Procedures Architecture",
draft-ietf-rats-architecture-05 (work in progress), July draft-ietf-rats-architecture-06 (work in progress),
2020. September 2020.
[I-D.ietf-rats-eat] [I-D.ietf-rats-eat]
Mandyam, G., Lundblade, L., Ballesteros, M., and J. Mandyam, G., Lundblade, L., Ballesteros, M., and J.
O'Donoghue, "The Entity Attestation Token (EAT)", draft- O'Donoghue, "The Entity Attestation Token (EAT)", draft-
ietf-rats-eat-03 (work in progress), February 2020. ietf-rats-eat-04 (work in progress), August 2020.
[I-D.ietf-rats-yang-tpm-charra]
Birkholz, H., Eckel, M., Bhandari, S., Sulzen, B., Voit,
E., Xia, L., Laffey, T., and G. Fedorkow, "A YANG Data
Model for Challenge-Response-based Remote Attestation
Procedures using TPMs", draft-ietf-rats-yang-tpm-charra-02
(work in progress), June 2020.
[I-D.ietf-sacm-coswid]
Birkholz, H., Fitzgerald-McKay, J., Schmidt, C., and D.
Waltermire, "Concise Software Identification Tags", draft-
ietf-sacm-coswid-15 (work in progress), May 2020.
[I-D.richardson-rats-usecases] [I-D.richardson-rats-usecases]
Richardson, M., Wallace, C., and W. Pan, "Use cases for Richardson, M., Wallace, C., and W. Pan, "Use cases for
Remote Attestation common encodings", draft-richardson- Remote Attestation common encodings", draft-richardson-
rats-usecases-07 (work in progress), March 2020. rats-usecases-07 (work in progress), March 2020.
[I-D.voit-rats-trusted-path-routing] [I-D.voit-rats-trusted-path-routing]
Voit, E., "Trusted Path Routing", draft-voit-rats-trusted- Voit, E., "Trusted Path Routing", draft-voit-rats-trusted-
path-routing-02 (work in progress), June 2020. path-routing-02 (work in progress), June 2020.
[IEEE-802-1AR]
Seaman, M., "802.1AR-2018 - IEEE Standard for Local and
Metropolitan Area Networks - Secure Device Identity, IEEE
Computer Society", August 2018.
[IEEE-802.1ae] [IEEE-802.1ae]
Seaman, M., "802.1AE MAC Security (MACsec)", 2018, Seaman, M., "802.1AE MAC Security (MACsec)", 2018,
<https://1.ieee802.org/security/802-1ae/>. <https://1.ieee802.org/security/802-1ae/>.
[IEEE-802.1x] [IEEE-802.1x]
IEEE Computer Society, "802.1X-2020 - IEEE Standard for IEEE Computer Society, "802.1X-2020 - IEEE Standard for
Local and Metropolitan Area Networks--Port-Based Network Local and Metropolitan Area Networks--Port-Based Network
Access Control", February 2020, Access Control", February 2020,
<https://standards.ieee.org/standard/802_1X-2020.html>. <https://standards.ieee.org/standard/802_1X-2020.html>.
skipping to change at page 36, line 11 skipping to change at page 40, line 18
Identification (SWID) Tags", April 2016, Identification (SWID) Tags", April 2016,
<https://nvlpubs.nist.gov/nistpubs/ir/2016/ <https://nvlpubs.nist.gov/nistpubs/ir/2016/
NIST.IR.8060.pdf>. NIST.IR.8060.pdf>.
[NIST-SP-800-155] [NIST-SP-800-155]
National Institute for Standards and Technology, "BIOS National Institute for Standards and Technology, "BIOS
Integrity Measurement Guidelines (Draft)", December 2011, Integrity Measurement Guidelines (Draft)", December 2011,
<https://csrc.nist.gov/csrc/media/publications/sp/800- <https://csrc.nist.gov/csrc/media/publications/sp/800-
155/draft/documents/draft-sp800-155_dec2011.pdf>. 155/draft/documents/draft-sp800-155_dec2011.pdf>.
[PC-Client-BIOS-TPM-1.2]
Trusted Computing Group, "TCG PC Client Specific
Implementation Specification for Conventional BIOS,
Specification Version 1.21 Errata, Revision 1.00",
February 2012,
<https://trustedcomputinggroup.org/resource/pc-client-
work-group-specific-implementation-specification-for-
conventional-bios/>.
[PC-Client-BIOS-TPM-2.0]
Trusted Computing Group, "PC Client Specific Platform
Firmware Profile Specification Family "2.0", Level 00
Revision 1.04", June 2019,
<https://trustedcomputinggroup.org/pc-client-specific-
platform-firmware-profile-specification>.
[PC-Client-RIM]
Trusted Computing Group, "DRAFT: TCG PC Client Reference
Integrity Manifest Specification, v.09", December 2019,
<https://trustedcomputinggroup.org/wp-content/uploads/
TCG_PC_Client_RIM_r0p15_15june2020.pdf>.
[Platform-Certificates] [Platform-Certificates]
Trusted Computing Group, "TCG Platform Attribute Trusted Computing Group, "TCG Platform Attribute
Credential Profile, Specification Version 1.0, Revision Credential Profile, Specification Version 1.0, Revision
16", January 2018, 16", January 2018,
<https://trustedcomputinggroup.org/resource/tcg-platform- <https://trustedcomputinggroup.org/resource/tcg-platform-
attribute-credential-profile/>. attribute-credential-profile/>.
[Platform-DevID-TPM-2.0]
Trusted Computing Group, "DRAFT: TPM Keys for Platform
DevID for TPM2, Specification Version 0.7, Revision 0",
October 2018.
[Platform-ID-TPM-1.2]
Trusted Computing Group, "TPM Keys for Platform Identity
for TPM 1.2, Specification Version 1.0, Revision 3",
August 2015, <https://trustedcomputinggroup.org/resource/
tpm-keys-for-platform-identity-for-tpm-1-2-2/>.
[Provisioning-TPM-2.0] [Provisioning-TPM-2.0]
Trusted Computing Group, "TCG TPM v2.0 Provisioning Trusted Computing Group, "TCG TPM v2.0 Provisioning
Guidance, Version 1.0, Revision 1.0", March 2015, Guidance, Version 1.0, Revision 1.0", March 2015,
<https://trustedcomputinggroup.org/wp-content/uploads/TCG- <https://trustedcomputinggroup.org/wp-content/uploads/TCG-
TPM-v2.0-Provisioning-Guidance-Published-v1r1.pdf>. TPM-v2.0-Provisioning-Guidance-Published-v1r1.pdf>.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, Ed., "Extensible Authentication Protocol Levkowetz, Ed., "Extensible Authentication Protocol
(EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004, (EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004,
<https://www.rfc-editor.org/info/rfc3748>. <https://www.rfc-editor.org/info/rfc3748>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6813] Salowey, J. and S. Hanna, "The Network Endpoint Assessment [RFC6813] Salowey, J. and S. Hanna, "The Network Endpoint Assessment
(NEA) Asokan Attack Analysis", RFC 6813, (NEA) Asokan Attack Analysis", RFC 6813,
DOI 10.17487/RFC6813, December 2012, DOI 10.17487/RFC6813, December 2012,
<https://www.rfc-editor.org/info/rfc6813>. <https://www.rfc-editor.org/info/rfc6813>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC8572] Watsen, K., Farrer, I., and M. Abrahamsson, "Secure Zero
Touch Provisioning (SZTP)", RFC 8572,
DOI 10.17487/RFC8572, April 2019,
<https://www.rfc-editor.org/info/rfc8572>.
[RIM] Trusted Computing Group, "DRAFT: TCG Reference Integrity
Manifest Information Model", June 2019,
<https://trustedcomputinggroup.org/wp-content/uploads/
TCG_RIM_Model_v1-r13_2feb20.pdf>.
[SP800-155] [SP800-155]
National Institute of Standards and Technology, "BIOS National Institute of Standards and Technology, "BIOS
Integrity Measurement Guidelines (Draft)", December 2011, Integrity Measurement Guidelines (Draft)", December 2011,
<https://csrc.nist.gov/csrc/media/publications/sp/800- <https://csrc.nist.gov/csrc/media/publications/sp/800-
155/draft/documents/draft-sp800-155_dec2011.pdf>. 155/draft/documents/draft-sp800-155_dec2011.pdf>.
[SWID] The International Organization for Standardization/ [SWID-Gen]
International Electrotechnical Commission, "Information Labs64, Munich, Germany, "SoftWare IDentification (SWID)
Technology Software Asset Management Part 2: Software Tags Generator (Maven Plugin)", n.d.,
Identification Tag, ISO/IEC 19770-2", October 2015, <https://github.com/Labs64/swid-maven-plugin>.
<https://www.iso.org/standard/65666.html>.
[TAP] Trusted Computing Group, "TCG Trusted Attestation Protocol
(TAP) Information Model for TPM Families 1.2 and 2.0 and
DICE Family 1.0, Version 1.0, Revision 0.36", October
2018, <https://trustedcomputinggroup.org/resource/tcg-tap-
information-model/>.
[TCGRoT] Trusted Computing Group, "DRAFT: TCG Roots of Trust [TCGRoT] Trusted Computing Group, "DRAFT: TCG Roots of Trust
Specification", October 2018, Specification", October 2018,
<https://trustedcomputinggroup.org/wp-content/uploads/ <https://trustedcomputinggroup.org/wp-content/uploads/
TCG_Roots_of_Trust_Specification_v0p20_PUBLIC_REVIEW.pdf>. TCG_Roots_of_Trust_Specification_v0p20_PUBLIC_REVIEW.pdf>.
[TPM] ISO/IEC JTC 1 Information technology, "ISO/IEC [TPM1.2] Trusted Computing Group, "TPM Main Specification Level 2
11889-1:2015 Information technology -- Trusted platform Version 1.2, Revision 116", March 2011,
module library -- Part 1: Architecture", August 2015, <https://trustedcomputinggroup.org/resource/tpm-main-
<https://www.iso.org/standard/66510.html>. specification/>.
[TPM2.0] Trusted Computing Group, "Trusted Platform Module Library
Specification, Family "2.0", Level 00, Revision 01.59",
November 2019,
<https://trustedcomputinggroup.org/resource/tpm-library-
specification/>.
Authors' Addresses Authors' Addresses
Guy Fedorkow (editor) Guy Fedorkow (editor)
Juniper Networks, Inc. Juniper Networks, Inc.
US US
Email: gfedorkow@juniper.net Email: gfedorkow@juniper.net
Eric Voit Eric Voit
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