RFC 9684
A YANG Data Model for Challenge-Response-Based Remote Attestation (CHARRA) Procedures Using Trusted Platform Modules (TPMs)
okay bestie, RFC 9684 is here and it's giving sleek security energy 🦋✨
This is a Standards Track document from the IETF, published in December 2024 with ISSN 2070-1721 💅 The authors are H. Birkholz and M. Eckel (Fraunhofer SIT | ATHENE), S. Bhandari (ThoughtSpot), E. Voit, B. Sulzen (Cisco), L. Xia (Huawei), T. Laffey (HPE), and G. C. Fedorkow (Juniper) 🫶 The title block doesn't list anything it obsoletes or updates, so no drama there 🌸
A YANG Data Model for Challenge-Response-Based Remote Attestation (CHARRA) Procedures Using Trusted Platform Modules (TPMs)
Abstract ✨
Okay so this doc defines the YANG Remote Procedure Calls (RPCs) and configuration nodes you need to fetch attestation evidence about integrity measurements from a device 🔥 It follows the operational context from RFC 9683 "TPM-based Network Device Remote Integrity Verification", which is giving clean, organised, no-chaos vibes. Complementary measurement logs from one or more Roots of Trust for Measurement (RTMs) also come through these YANG RPCs 🧚
The module needs the device components of the composite device (the one the YANG server runs on) to include at least one Trusted Platform Module (TPM) of version 1.2 or 2.0, plus a matching TPM Software Stack (TSS) 💜 Or you can use an equivalent hardware implementation that has the protected capabilities TPMs provide, along with a matching software stack. Ngl, that's a lot of setup, but the payoff is worth it 👑
Status of This Memo ✨
This is an Internet Standards Track document 🎀
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It went through public review and got approved for publication by the Internet Engineering Steering Group (IESG) 🌈 If you want more info on Internet Standards, check Section 2 of RFC 7841. For the current status, any errata, and how to give feedback, go to https://www.rfc-editor.org/info/rfc9684 🍓
Copyright Notice ✨
Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved 💖
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date this document was published. Please read these carefully, because they spell out your rights and restrictions for this document 🙈 Code Components pulled out of this document must include Revised BSD License text, as described in Section 4.e of the Trust Legal Provisions, and they come without warranty, as described in the Revised BSD License 💅
Table of Contents ✨
1. Introduction
1.1. Requirements Notation
2. The YANG Module for Basic Remote Attestation Procedures
2.1. YANG Modules
2.1.1. ietf-tpm-remote-attestation
2.1.1.1. Features
2.1.1.2. Identities
2.1.1.3. Remote Procedure Calls (RPCs)
2.1.2. ietf-tcg-algs
3. IANA Considerations
4. Security Considerations
5. References
5.1. Normative References
5.2. Informative References
Appendix A. Integrity Measurement Architecture (IMA)
Appendix B. IMA for Network Equipment Boot Logs
Authors' Addresses1. Introduction 🦋
This doc is built on the general terminology from the Remote ATtestation procedureS (RATS) architecture [RFC9334] 🧠 It also uses the operational context from [RFC9683], plus the interaction model and information elements from [RATS-Interaction-Models]. The hardware security modules (HSMs) it supports right now are the Trusted Platform Modules (TPMs) [TPM1.2] [TPM2.0], as specified by the Trusted Computing Group (TCG) 🔐 You need one TPM to use the YANG module in this document, or multiple TPMs if you've got a composite device 🫧
Each TPM works as a Root of Trust for Storage (RTS), which means it stores system security measurement Evidence 💜 Each TPM also works as a Root of Trust for Reporting (RTR), which means it retrieves attestation Evidence 🌸 To do that, you use a YANG RPC to request a quote. The quote exposes a rolling hash of the security measurements stored inside the TPM, and it's honestly so iconic 😭
Some specific terms come from [RFC9334] and are used in this document: Attester, composite device, and Evidence ✨ Others come from [TPM2.0-Key]: Endorsement Key (EK), Initial Attestation Key (IAK), Attestation Identity Key (AIK), and Local Attestation Key (LAK) 🧚
1.1. Requirements Notation 🎀
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here 💅 So a lowercase version is just vibes, not a rule.
2. The YANG Module for Basic Remote Attestation Procedures 👑
One or more TPMs MUST be embedded in a composite device that provides attestation Evidence through the YANG module defined here 🔥 The ietf-tpm-remote-attestation YANG module lets a composite device take on the role of an Attester, following the RATS architecture [RFC9334] and the matching challenge-response interaction model in [RATS-Interaction-Models] 🦋 A fresh nonce with an appropriate amount of entropy [NIST-915121] MUST be supplied by the YANG client. That's how you get a proof-of-freshness for the attestation Evidence the Attester gives from the YANG datastore it's running 🫶 This nonce also prevents replay attacks, so it's literally doing the most 🙈 How each individual TPM relates to the specific measured component inside the composite device is out of scope for this document 💖
2.1. YANG Modules 🌸
In this section, the two YANG modules get defined ✨
2.1.1. ietf-tpm-remote-attestation 🧚
This YANG module imports modules from [RFC6991] with prefix 'yang', [RFC8348] with prefix 'hw', [RFC9642] with prefix 'ks', and ietf-tcg-algs.yang Section 2.1.2.3 with prefix 'taa' 💜 It also makes references to [RFC6933], [TPM1.2-Commands], [TPM2.0-Arch], [TPM2.0-Structures], [TPM2.0-Key], [TPM1.2-Structures], [BIOS-Log], and [CEL], plus Appendix B 📚
2.1.1.1. Features 🎀
This module supports the following features:
'mtpm': Indicates that multiple TPMs on the device can support remote attestation. For example, this feature could be used when multiple line cards are present, each with its own TPM 🍓'bios': Indicates that the device supports retrieval of BIOS and Unified Extensible Firmware Interface (UEFI) event logs [BIOS-Log] 🌈'ima': Indicates that the device supports retrieval of event logs from the Linux Integrity Measurement Architecture (IMA, see Appendix A) 🔥'netequip_boot': Indicates that the device supports retrieval of netequip boot event logs. See Appendixes A and B 👑
2.1.1.2. Identities 🦋
This module supports the following types of attestation event logs: 'bios', 'ima', and 'netequip_boot' ✨
2.1.1.3. Remote Procedure Calls (RPCs) 💅
In the following sections, RPCs for attestation procedures for both TPM 1.2 and TPM 2.0 are defined 🧚
2.1.1.3.1. tpm12-challenge-response-attestation 🫧
This RPC lets a Verifier ask, via the TPM Quote operation, for signed TPM Platform Configuration Registers (PCRs) from a cryptoprocessor that's compliant with TPM 1.2 💖 When the feature 'mtpm' is active and one or more 'certificate-name' isn't provided, all cryptoprocessors compliant with TPM 1.2 will respond. The YANG tree diagram for this RPC looks like this 🙈
+---x tpm12-challenge-response-attestation {taa:tpm12}?
+---w input
| +---w tpm12-attestation-challenge
| +---w pcr-index* pcr
| +---w nonce-value binary
| +---w certificate-name* certificate-name-ref
| {tpm:mtpm}?
+--ro output
+--ro tpm12-attestation-response* []
+--ro certificate-name certificate-name-ref
+--ro up-time? uint32
+--ro TPM_QUOTE2? binaryPart 1 of 11 is done, bestie 🎀 More parts are coming, so stay tuned 💜
2.1.1.3.2. tpm20-challenge-response-attestation 🌸
okay so this RPC is giving "Verifier, please show me your receipts" energy 💅 A Verifier uses it to request signed TPM PCRs (the TPM Quote operation) from a cryptoprocessor that's compliant with TPM 2.0 ✨ Where the feature 'mtpm' is active and one or more 'certificate-name' is not provided, all cryptoprocessors compliant with TPM 2.0 will respond 🫶 Here's the YANG tree diagram for this RPC 🦋
+---x tpm20-challenge-response-attestation {taa:tpm20}?
+---w input
| +---w tpm20-attestation-challenge
| +---w nonce-value binary
| +---w tpm20-pcr-selection* []
| | +---w tpm20-hash-algo? identityref
| | +---w pcr-index* pcr
| +---w certificate-name* certificate-name-ref
| {tpm:mtpm}?
+--ro output
+--ro tpm20-attestation-response* []
+--ro certificate-name certificate-name-ref
+--ro TPMS_QUOTE_INFO binary
+--ro quote-signature? binary
+--ro up-time? uint32
+--ro unsigned-pcr-values* []
+--ro tpm20-hash-algo? identityref
+--ro pcr-values* [pcr-index]
+--ro pcr-index pcr
+--ro pcr-value? binaryNow the example! 🎀 This is an RPC challenge asking for PCRs 0-7 from a SHA-256 bank:
<rpc message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<tpm20-attestation-challenge
xmlns="urn:ietf:params:yang:ietf-tpm-remote-attestation">
<certificate-name>
(identifier of a TPM signature key with which the Attester is
supposed to sign the attestation data)
</certificate-name>
<nonce>
0xe041307208d9f78f5b1bbecd19e2d152ad49de2fc5a7d8dbf769f6b8ffdeab9
</nonce>
<tpm20-pcr-selection>
<tpm20-hash-algo
xmlns="urn:ietf:params:xml:ns:yang:ietf-tcg-algs">
TPM_ALG_SHA256
</tpm20-hash-algo>
<pcr-index>0</pcr-index>
<pcr-index>1</pcr-index>
<pcr-index>2</pcr-index>
<pcr-index>3</pcr-index>
<pcr-index>4</pcr-index>
<pcr-index>5</pcr-index>
<pcr-index>6</pcr-index>
<pcr-index>7</pcr-index>
</tpm20-pcr-selection>
</tpm20-attestation-challenge>
</rpc>And if it works out, a successful response looks like this 😭🙌
<rpc-reply message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<tpm20-attestation-response
xmlns="urn:ietf:params:xml:ns:yang:ietf-tpm-remote-attestation">
<certificate-name
xmlns="urn:ietf:params:xml:ns:yang:ietf-keystore">
(instance of certificate name in the keystore)
</certificate-name>
<attestation-data>
(raw attestation data, i.e., the TPM quote; this includes,
among other information, a composite digest of requested PCRs,
the nonce, and TPM 2.0 clock information.)
</attestation-data>
<quote-signature>
(signature over attestation-data using the TPM key
identified by sig-key-id)
</quote-signature>
</tpm20-attestation-response>
</rpc-reply>2.1.1.4. log-retrieval 🧚
this RPC is the Verifier's way of getting the Evidence that was extended into specific TPM PCRs 📜 It's giving "show me the whole diary" vibes 💜 Here's the YANG tree diagram:
+---x log-retrieval
+---w input
| +---w log-type identityref
| +---w log-selector* []
| +---w name* string
| +---w (index-type)?
| | +--:(last-entry)
| | | +---w last-entry-value? binary
| | +--:(index)
| | | +---w last-index-number? uint64
| | +--:(timestamp)
| | +---w timestamp? yang:date-and-time
| +---w log-entry-quantity? uint16
+--ro output
+--ro system-event-logs
+--ro node-data* []
+--ro name? string
+--ro up-time? uint32
+--ro log-result
+--ro (attested_event_log_type)
+--:(bios) {bios}?
| +--ro bios-event-logs
| +--ro bios-event-entry* [event-number]
| +--ro event-number uint32
| +--ro event-type? uint32
| +--ro pcr-index? pcr
| +--ro digest-list* []
| | +--ro hash-algo? identityref
| | +--ro digest* binary
| +--ro event-size? uint32
| +--ro event-data* binary
+--:(ima) {ima}?
| +--ro ima-event-logs
| +--ro ima-event-entry* [event-number]
| +--ro event-number uint64
| +--ro ima-template? string
| +--ro filename-hint? string
| +--ro filedata-hash? binary
| +--ro filedata-hash-algorithm? string
| +--ro template-hash-algorithm? string
| +--ro template-hash? binary
| +--ro pcr-index? pcr
| +--ro signature? binary
+--:(netequip_boot) {netequip_boot}?
+--ro boot-event-logs
+--ro boot-event-entry* [event-number]
+--ro event-number uint64
+--ro ima-template? string
+--ro filename-hint? string
+--ro filedata-hash? binary
+--ro filedata-hash-algorithm? string
+--ro template-hash-algorithm? string
+--ro template-hash? binary
+--ro pcr-index? pcr
+--ro signature? binary2.1.1.5. Data Nodes 🍓
this section is the high-level tour of the data nodes that hold the configuration and operational objects in the YANG data model 🗺️ If you want the nitty-gritty, the YANG module itself is in Figure 1 🤓
Container 'rats-support-structures' 🏠: this is the house for all the remote attestation info for a device. It covers the specific device TPM(s), the compute nodes (like line cards) where those TPM(s) live, and the algorithms supported across the whole platform.
Container 'tpms' 🔐: this has the configuration and operational details for each supported TPM, like the tpm-firmware-version, the PCRs that can be quoted, the certificates tied to that TPM, and the current operational status. The certificates are the main tea ☕ Because a certificate is associated with a particular TPM Attestation Key, knowing the certificate lets you identify a specific TPM.
+--rw tpms
+--rw tpm* [name]
+--rw name string
+--ro hardware-based boolean
+--ro physical-index? int32 {hw:entity-mib}?
+--ro path? string
+--ro compute-node compute-node-ref {tpm:mtpm}?
+--ro manufacturer? string
+--rw firmware-version identityref
+--rw tpm12-hash-algo? identityref {taa:tpm12}?
+--rw tpm12-pcrs* pcr
+--rw tpm20-pcr-bank* [tpm20-hash-algo] {taa:tpm20}?
| +--rw tpm20-hash-algo identityref
| +--rw pcr-index* tpm:pcr
+--ro status enumeration
+--rw certificates
+--rw certificate* [name]
+--rw name string
+--rw keystore-ref? leafref {ks:asymmetric-keys}?
+--rw type? enumerationContainer 'attester-supported-algos' 🧪: this one identifies which TCG hash algorithms are available for use on the Attesting platform. An operator uses this info to limit the algorithms RPCs can use to just a desired set, picked from all the hash algorithms the TCG allows 💖
+--rw attester-supported-algos
+--rw tpm12-asymmetric-signing* identityref {taa:tpm12}?
+--rw tpm12-hash* identityref {taa:tpm12}?
+--rw tpm20-asymmetric-signing* identityref {taa:tpm20}?
+--rw tpm20-hash* identityref {taa:tpm20}?Container 'compute-nodes' 🖥️: when more than one TPM is supported, this container keeps track of the compute node linked to each specific TPM. That way, every TPM can say which 'compute-node' it belongs to 🫶
+--rw compute-nodes {tpm:mtpm}?
+--ro compute-node* [node-id]
+--ro node-id string
+--ro node-physical-index? int32 {hw:entity-mib}?
+--ro node-name? string
+--ro node-location? string2.1.1.6. YANG Module 👑
here's the full YANG module, the whole main character 🎬
<CODE BEGINS> file "ietf-tpm-remote-attestation@2024-12-05.yang"
module ietf-tpm-remote-attestation {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang"
+ ":ietf-tpm-remote-attestation";
prefix tpm;
import ietf-yang-types {
prefix yang;
}
import ietf-hardware {
prefix hw;
}
import ietf-keystore {
prefix ks;
}
import ietf-tcg-algs {
prefix taa;
}
organization
"IETF RATS (Remote ATtestation procedureS) Working Group";
contact
"WG Web : <https://datatracker.ietf.org/wg/rats/>
WG List : <mailto:rats@ietf.org>
Author : Eric Voit <evoit@cisco.com>
Author : Henk Birkholz <henk.birkholz@ietf.contact>
Author : Michael Eckel <michael.eckel@sit.fraunhofer.de>
Author : Shwetha Bhandari <shwetha.bhandari@thoughtspot.com>
Author : Bill Sulzen <bsulzen@cisco.com>
Author : Liang Xia (Frank) <frank.xialiang@huawei.com>
Author : Tom Laffey <tom.laffey@hpe.com>
Author : Guy C. Fedorkow <gfedorkow@juniper.net>";
description
"A YANG module to enable remote attestation procedures based
on TPM 1.2 and TPM 2.0 using a challenge-response
interaction model and the Quote primitive operations defined
by TPM 1.2 and TPM 2.0.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
Copyright (c) 2024 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Revised BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 9684; see the
RFC itself for full legal notices.";okay the module keeps going and it's giving feature flags, typedefs, identities and groupings all in one place 💅✨
revision 2024-12-05 {
description
"Initial version";
reference
"RFC 9684: A YANG Data Model for Challenge-Response-Based
Remote Attestation (CHARRA) Procedures Using Trusted Platform
Modules (TPMs)";
}
/*****************/
/* Features */
/*****************/
feature mtpm {
description
"The device supports the remote attestation of multiple
TPM-based cryptoprocessors.";
}
feature bios {
description
"The device supports the BIOS logs.";
reference
"BIOS-Log:
TCG PC Client Platform Firmware Profile Specification,
https://trustedcomputinggroup.org/wp-content/uploads/
TCG-PC-Client-Platform-Firmware-Profile-Version-1.06-
Revision-52_pub-2.pdf, Section 10.4.5.2";
}
feature ima {
description
"The device supports Integrity Measurement Architecture logs.
Many variants of IMA logs exist in the deployment. Each
encodes the log entry contents as the specific measurements
that get hashed into a PCRs as Evidence. See the reference
below for one example of such an encoding.";
reference
"CEL:
Canonical Event Log Format,
https://www.trustedcomputinggroup.org/wp-content/uploads/
TCG_IWG_CEL_v1_r0p41_pub.pdf, Section 5.1.6";
}
feature netequip_boot {
description
"The device supports the netequip_boot logs.";
reference
"RFC 9684: A YANG Data Model for Challenge-Response-Based
Remote Attestation (CHARRA) Procedures Using Trusted Platform
Modules (TPMs), Appendix B";
}
/*****************/
/* Typedefs */
/*****************/
typedef pcr {
type uint8 {
range "0..31";
}
description
"Valid index number for a PCR. A PCR index compliant with
TPM 2.0 extends from 0-31. At this time, a typical TPM would
have no more than 32 PCRs.";
}
typedef compute-node-ref {
type leafref {
path "/tpm:rats-support-structures/tpm:compute-nodes"
+ "/tpm:compute-node/tpm:node-id";
}
description
"This type is used to reference a hardware node. Note that an
implementer might include an alternative leafref pointing to a
different YANG module node specifying hardware structures.";
}
typedef certificate-name-ref {
type leafref {
path "/tpm:rats-support-structures/tpm:tpms/tpm:tpm"
+ "/tpm:certificates/tpm:certificate/tpm:name";
}
description
"A type that allows identification of a TPM-based
certificate.";
}
/******************/
/* Identities */
/******************/
identity attested_event_log_type {
description
"Base identity allowing categorization of the reasons why an
attested measurement has been taken on an Attester.";
}
identity ima {
base attested_event_log_type;
description
"An event type recorded in IMA.";
}
identity bios {
base attested_event_log_type;
description
"An event type associated with BIOS/UEFI.";
}
identity netequip_boot {
base attested_event_log_type;
description
"An event type associated with Network Equipment Boot.";
}
/*****************/
/* Groupings */
/*****************/
grouping tpm20-hash-algo {
description
"The cryptographic algorithm used to hash the PCRs compliant
with TPM 2.0. This must be from the list of platform-
supported options.";
leaf tpm20-hash-algo {
type identityref {
base taa:hash;
}
must '. = /tpm:rats-support-structures'
+ '/tpm:attester-supported-algos/tpm:tpm20-hash' {
error-message "This platform does not support "
+ "tpm20-hash-algo";
}
description
"The hash scheme that is used to hash a PCR compliant with
TPM 2.0. This must be one of those supported by a platform.
Where this object does not appear, the default value of
'taa:TPM_ALG_SHA256' will apply.";
}
}
grouping tpm12-hash-algo {
description
"The cryptographic algorithm used to hash the PCRs compliant
with TPM 1.2.";
leaf tpm12-hash-algo {
type identityref {
base taa:hash;
}
must '. = /tpm:rats-support-structures'
+ '/tpm:attester-supported-algos/tpm:tpm12-hash' {
error-message "This platform does not support "
+ "tpm12-hash-algo";
}
description
"The hash scheme that is used to hash a PCR compliant with
TPM 1.2. This MUST be one of those supported by a platform.
Where this object does not appear, the default value of
'taa:TPM_ALG_SHA1' will apply.";
}
}
grouping nonce {
description
"A random number intended to guarantee freshness and for use
as part of a replay-detection mechanism.";
leaf nonce-value {
type binary;
mandatory true;
description
"A cryptographically generated random number that should
not be predictable prior to its issuance from a random
number generation function. The random number MUST be
derived from an entropy source external to the Attester.
Note that a nonce sent into a TPM will typically be 160 or
256 binary digits long. (This is 20 or 32 bytes.) So if
fewer binary digits are sent, this nonce object will be
padded with leading zeros within Quotes returned from the
TPM. Additionally, if more bytes are sent, the nonce will
be trimmed to the most significant binary digits.";
}
}
grouping tpm12-pcr-selection {
description
"A Verifier can request one or more PCR values using its
individually created Attestation Key Certificate (AC).
The corresponding selection filter is represented in this
grouping.";
leaf-list pcr-index {
type pcr;
description
"The numbers/indexes of the PCRs. In addition, any selection
of PCRs MUST verify that the set of PCRs requested are a
subset of the set of PCRs exposed in the leaf-list
/tpm:rats-support-structures
/tpm:tpms/tpm:tpm[name=current()]/tpm:tpm12-pcrs";
}
}
grouping tpm20-pcr-selection {
description
"A Verifier can acquire one or more PCR values, which are
hashed together in a TPM2B_DIGEST coming from the TPM2.
The selection list of desired PCRs and the hash algorithm
is represented in this grouping.";
list tpm20-pcr-selection {
unique "tpm20-hash-algo";
description
"Specifies the list of PCRs and hash algorithms that can be
returned within a TPM2B_DIGEST.";
reference
"TPM2.0-Structures:
Trusted Platform Module Library Part 2: Structures,
Revision 01.83, https://trustedcomputinggroup.org/
wp-content/uploads/TPM-2.0-1.83-Part-2-Structures.pdf,
Section 10.9.7";
uses tpm20-hash-algo;
leaf-list pcr-index {
type pcr;
description
"The numbers of the PCRs that are being tracked
with a hash based on the tpm20-hash-algo. In addition,
any selection of PCRs MUST verify that the set of PCRs
requested are a subset of the set of selected PCR indexes
available for that specific TPM.";
}
}
}
grouping certificate-name-ref {
description
"Identifies a certificate in a keystore.";
leaf certificate-name {
type certificate-name-ref;
mandatory true;
description
"Identifies a certificate in a keystore.";
}
}
grouping tpm-name {
description
"A unique TPM on a device.";
leaf name {
type string;
description
"Unique system-generated name for a TPM on a device.";
}
}
grouping node-uptime {
description
"Uptime in seconds of the node.";
leaf up-time {
type uint32;
description
"Uptime in seconds of this node reporting its data.";
}
}
grouping tpm12-attestation {
description
"Contains an instance of cryptoprocessor measurements signed
according to TPM 1.2. It is supplemented by unsigned
Attester information.";
uses node-uptime;
leaf pcr-data {
type binary;
description
"The value created and signed for the quote
(type TPM_PCR_INFO_SHORT), i.e., the 'pcrData' part of
a TPM1.2 Quote2 operation result.";
reference
"TPM1.2-Commands:
TPM Main Part 3 Commands, Rev116,
https://trustedcomputinggroup.org/wp-content/uploads
/TPM-Main-Part-3-Commands_v1.2_rev116_01032011.pdf,
Section 16.5";
}
leaf version-info {
type binary;
description
"The version info (type TPM_CAP_VERSION_INFO),
i.e., the 'versionInfo' part of a TPM1.2 Quote2
operation result.";
reference
"TPM1.2-Commands:
TPM Main Part 3 Commands, Rev116,
https://trustedcomputinggroup.org/wp-content/uploads
/TPM-Main-Part-3-Commands_v1.2_rev116_01032011.pdf,
Section 16.5";
}
leaf sig {
type binary;
description
"The signature generated across the signed data,
i.e., the 'sig' part of a TPM1.2 Quote2 operation
result.";
reference
"TPM1.2-Commands:
TPM Main Part 3 Commands, Rev116,
https://trustedcomputinggroup.org/wp-content/uploads
/TPM-Main-Part-3-Commands_v1.2_rev116_01032011.pdf,
Section 16.5";
}
}Okay bestie, let's dive into the TPM 2.0 bundle first 💜
grouping tpm20-attestation {
description
"Contains an instance of cryptoprocessor measurements signed
according to TPM 2.0. It is supplemented by unsigned
Attester information.";
leaf quote-data {
type binary;
mandatory true;
description
"A hash of the latest PCR values (and the hash algorithm
used) that have been returned from an Attester for the
selected PCRs and hash algorithms.";
reference
"TPM2.0-Structures:
Trusted Platform Module Library Part 2: Structures,
Revision 01.83, https://trustedcomputinggroup.org/
wp-content/uploads/TPM-2.0-1.83-Part-2-Structures.pdf,
Section 10.12.1";
}
leaf quote-signature {
type binary;
description
"Quote signature returned by TPM Quote. The signature was
generated using the key associated with the
certificate 'name'.";
reference
"TPM2.0-Structures:
Trusted Platform Module Library Part 2: Structures,
Revision 01.83, https://trustedcomputinggroup.org/
wp-content/uploads/TPM-2.0-1.83-Part-2-Structures.pdf,
Section 11.2.1";
}
uses node-uptime;
list unsigned-pcr-values {
description
"PCR values in each PCR bank. This might appear redundant
with the TPM2B_DIGEST, but that digest is calculated across
multiple PCRs. Having to verify across multiple PCRs does
not necessarily make it easy for a Verifier to appraise just
the minimum set of PCR information that has changed since
the last received TPM2B_DIGEST. Put another way, why should
a Verifier reconstruct the proper value of all PCR Quotes
when only a single PCR has changed?
To help this happen, if the Attester does know specific PCR
values, the Attester can provide these individual values via
'unsigned-pcr-values'. By comparing this information to
what has previously been validated, it is possible for a
Verifier to confirm the Attester's signature while
eliminating significant processing. Note that there should
never be a result where an unsigned PCR value differs from
what may be reconstructed from within the PCR quote and
the event logs.
If there is a difference, a signed result that has been
verified from retrieved logs is considered definitive.";
uses tpm20-hash-algo;
list pcr-values {
key "pcr-index";
description
"List of one PCR bank.";
leaf pcr-index {
type pcr;
description
"PCR index number.";
}
leaf pcr-value {
type binary;
description
"PCR value.";
reference
"TPM2.0-Structures:
Trusted Platform Module Library Part 2: Structures,
Revision 01.83, https://trustedcomputinggroup.org/
wp-content/uploads/TPM-2.0-1.83-Part-2-Structures.pdf,
Section 10.9.7";
}
}
}
}
grouping log-identifier {
description
"Identifier for type of log to be retrieved.";
leaf log-type {
type identityref {
base attested_event_log_type;
}
mandatory true;
description
"The corresponding identity of the measurement log type.";
}
}
grouping boot-event-log {
description
"Defines a specific instance of an event log entry
and corresponding to the information used to
extend the PCR.";
leaf event-number {
type uint32;
description
"Unique event number of this event, which monotonically
increases within a given event log. The maximum event
number should not be reached, nor is wrapping back to
an earlier number supported.";
}
leaf event-type {
type uint32;
description
"BIOS log event type.";
reference
"BIOS-Log:
TCG PC Client Platform Firmware Profile Specification,
https://trustedcomputinggroup.org/wp-content/uploads/
TCG-PC-Client-Platform-Firmware-Profile-Version-1.06-
Revision-52_pub-2.pdf, Section 10.4.1";
}
leaf pcr-index {
type pcr;
description
"Defines the PCR index that this event extended.";
}
list digest-list {
description
"Hash of event data.";
leaf hash-algo {
type identityref {
base taa:hash;
}
description
"The hash scheme that is used to compress the event data in
each of the leaf-list digest items.";
}
leaf-list digest {
type binary;
description
"The hash of the event data using the algorithm of the
'hash-algo' against 'event data'.";
}
}
leaf event-size {
type uint32;
description
"Size of the event data.";
}
leaf-list event-data {
type binary;
description
"The event data. This is a binary structure
of size 'event-size'. For more on what
might be recorded within this object
see BIOS-Log, Section 10, which details
viable events that might be recorded.";
reference
"BIOS-Log:
TCG PC Client Platform Firmware Profile Specification,
https://trustedcomputinggroup.org/wp-content/uploads/
TCG-PC-Client-Platform-Firmware-Profile-Version-1.06-
Revision-52_pub-2.pdf, Section 10";
}
}
grouping bios-event-log {
description
"Measurement log created by the BIOS/UEFI.";
list bios-event-entry {
key "event-number";
description
"Ordered list of the TCG-described event log
that extended the PCRs in the order they
were logged.";
uses boot-event-log;
}
}
grouping ima-event {
description
"Defines a hash log extend event for IMA measurements.";
reference
"CEL:
Canonical Event Log Format,
https://www.trustedcomputinggroup.org/wp-content/uploads/
TCG_IWG_CEL_v1_r0p41_pub.pdf, Section 4.3";
leaf event-number {
type uint64;
description
"Unique event number of this event, which monotonically
increases. The maximum event number should not be
reached, nor is wrapping back to an earlier number
supported.";
}
leaf ima-template {
type string;
description
"Name of the template used for event logs,
e.g., ima, ima-ng, ima-sig.";
}
leaf filename-hint {
type string;
description
"File name (including the path) that was measured.";
}
leaf filedata-hash {
type binary;
description
"Hash of filedata as updated based upon the
filedata-hash-algorithm.";
}
leaf filedata-hash-algorithm {
type string;
description
"Algorithm used for filedata-hash.";
}
leaf template-hash-algorithm {
type string;
description
"Algorithm used for template-hash.";
}
leaf template-hash {
type binary;
description
"hash(filedata-hash, filename-hint)";
}
leaf pcr-index {
type pcr;
description
"Defines the PCR index that this event extended.";
}
leaf signature {
type binary;
description
"Digital file signature that provides a
fingerprint for the file being measured.";
}
}
grouping ima-event-log {
description
"Measurement log created by IMA.";
list ima-event-entry {
key "event-number";
description
"Ordered list of IMA event logs by event-number.";
uses ima-event;
}
}
grouping network-equipment-boot-event-log {
description
"Measurement log created by Network Equipment Boot. The
Network Equipment Boot format is identical to the IMA
format. In contrast to the IMA log, the Network Equipment
Boot log includes every measurable event from an Attester,
including the boot stages of BIOS, Bootloader, etc. In
essence, the scope of events represented in this format
combines the scope of BIOS events and IMA events.";
list boot-event-entry {
key "event-number";
description
"Ordered list of Network Equipment Boot event logs
by event-number, using the IMA event format.";
uses ima-event;
}
}
grouping event-logs {
description
"A selector for the log and its type.";
choice attested_event_log_type {
mandatory true;
description
"Event log type determines the event log's content.";
case bios {
if-feature "bios";
description
"BIOS/UEFI event logs.";
container bios-event-logs {
description
"BIOS/UEFI event logs.";
uses bios-event-log;
}
}
case ima {
if-feature "ima";
description
"IMA event logs.";
container ima-event-logs {
description
"IMA event logs.";
uses ima-event-log;
}
}
case netequip_boot {
if-feature "netequip_boot";
description
"Network Equipment Boot event logs.";
container boot-event-logs {
description
"Network Equipment Boot event logs.";
uses network-equipment-boot-event-log;
}
}
}
}
/**********************/
/* RPC operations */
/**********************/okay bestie, the RPCs are up next and they are SO giving 💅✨
rpc tpm12-challenge-response-attestation {
if-feature "taa:tpm12";
description
"This RPC accepts the input for TSS TPM 1.2 commands made to
the attesting device.";
input {
container tpm12-attestation-challenge {
description
"This container includes every information element defined
in the reference challenge-response interaction model for
remote attestation. Corresponding values are based on
TPM 1.2 structure definitions";
uses tpm12-pcr-selection;
uses nonce;
leaf-list certificate-name {
if-feature "tpm:mtpm";
type certificate-name-ref;
must "/tpm:rats-support-structures/tpm:tpms"
+ "/tpm:tpm[tpm:firmware-version='taa:tpm12']"
+ "/tpm:certificates/"
+ "/tpm:certificate[name=current()]" {
error-message "Not an available TPM1.2 AIK certificate.";
}
description
"When populated, the RPC will only get a Quote for the
TPMs associated with these certificate(s).";
}
}
}
output {
list tpm12-attestation-response {
unique "certificate-name";
description
"The binary output of TPM 1.2 TPM_Quote/TPM_Quote2,
including the PCR selection and other associated
attestation evidence metadata.";
uses certificate-name-ref {
description
"Certificate associated with this tpm12-attestation.";
}
uses tpm12-attestation;
}
}
}
rpc tpm20-challenge-response-attestation {
if-feature "taa:tpm20";
description
"This RPC accepts the input for TSS TPM 2.0 commands of the
managed device. Composite devices may contain several TPMs;
/hardware/component/physical-index from the hardware
management YANG module is used to refer to dedicated TPMs in
composite devices; however, devices without TPMs are not
covered.";
input {
container tpm20-attestation-challenge {
description
"This container includes every information element defined
in the reference challenge-response interaction model for
remote attestation. Corresponding values are based on
TPM 2.0 structure definitions.";
uses nonce;
uses tpm20-pcr-selection;
leaf-list certificate-name {
if-feature "tpm:mtpm";
type certificate-name-ref;
must "/tpm:rats-support-structures/tpm:tpms"
+ "/tpm:tpm[tpm:firmware-version='taa:tpm20']"
+ "/tpm:certificates/"
+ "/tpm:certificate[name=current()]" {
error-message "Not an available TPM2.0 AIK certificate.";
}
description
"When populated, the RPC will only get a Quote for the
TPMs associated with the certificates.";
}
}
}
output {
list tpm20-attestation-response {
unique "certificate-name";
description
"The binary output of TPM2_Quote from one TPM of the
node which is identified by node-id: an attestation
structure (TPMS_ATTEST), including a length, and a
signature (TPMT_SIGNATURE) over that structure.";
reference
"TPM2.0-Structures:
Trusted Platform Module Library Part 2: Structures,
Revision 01.83, https://trustedcomputinggroup.org/
wp-content/uploads/TPM-2.0-1.83-Part-2-Structures.pdf,
Section 10.12.12";
uses certificate-name-ref {
description
"Certificate associated with this tpm20-attestation.";
}
uses tpm20-attestation;
}
}
}
rpc log-retrieval {
description
"Log entries are identified either via indices or by providing
the last line received. The number of lines returned can be
limited. The type of log is a choice that can be augmented.";
input {
uses log-identifier;
list log-selector {
description
"Only log entries that meet all of the provided selection
criteria are to be returned by the RPC output.";
leaf-list name {
type string;
description
"Name of one or more unique TPMs on a device. If this
object exists, a selection should pull only the objects
related to these TPM(s). If it does not exist, all
qualifying TPMs that are 'hardware-based' equals true
on the device are selected. When this selection
criteria is provided, it will be considered as a logical
AND with any other selection criteria provided.";
}
choice index-type {
description
"Last log entry received, log index number, or
timestamp.";
case last-entry {
description
"The last entry of the log already retrieved.";
leaf last-entry-value {
type binary;
description
"Content of a log event that matches 1:1 with a
unique event record contained within the log. Log
entries after this will be passed to the
requester. Note: if log entry values are not
unique, this MUST return an error.";
}
}
case index {
description
"Numeric index of the last log entry retrieved, or
zero.";
leaf last-index-number {
type uint64;
description
"The last numeric index number of a log entry.
Zero means to start at the beginning of the log.
Entries after this will be passed to the
requester.";
}
}
case timestamp {
leaf timestamp {
type yang:date-and-time;
description
"Timestamp from which to start the extraction. The
next log entry after this timestamp is to
be sent.";
}
description
"Timestamp from which to start the extraction.";
}
}
leaf log-entry-quantity {
type uint16;
description
"The number of log entries to be returned. If omitted, it
means all of them.";
}
}
}
output {
container system-event-logs {
description
"The requested data of the measurement event logs.";
list node-data {
unique "name";
description
"Event logs of a node in a distributed system
identified by the node name.";
uses tpm-name;
uses node-uptime;
container log-result {
description
"The requested entries of the corresponding log.";
uses event-logs;
}
}
}
}
}
/****************************************/
/* Config and Oper accessible nodes */
/****************************************/ container rats-support-structures {
description
"The datastore definition enabling Verifiers or Relying
Parties to discover the information necessary to use the
remote attestation RPCs appropriately.";
container compute-nodes {
if-feature "tpm:mtpm";
description
"Holds the set of device subsystems/components in this
composite device that support TPM operations.";
list compute-node {
key "node-id";
unique "node-name";
config false;
min-elements 2;
description
"A component within this composite device that
supports TPM operations.";
leaf node-id {
type string;
description
"ID of the compute node, such as Board Serial Number.";
}
leaf node-physical-index {
if-feature "hw:entity-mib";
type int32 {
range "1..2147483647";
}
config false;
description
"The entPhysicalIndex for the compute node.";
reference
"RFC 6933: Entity MIB (Version 4) - entPhysicalIndex";
}
leaf node-name {
type string;
description
"Name of the compute node.";
}
leaf node-location {
type string;
description
"Location of the compute node, such as slot number.";
}
}
}
container tpms {
description
"Holds the set of TPMs within an Attester.";
list tpm {
key "name";
unique "path";
description
"A list of TPMs in this composite device that RATS
can be conducted with.";
uses tpm-name;
leaf hardware-based {
type boolean;
config false;
mandatory true;
description
"System-generated indication of whether this is a
hardware-based TPM.";
}
leaf physical-index {
if-feature "hw:entity-mib";
type int32 {
range "1..2147483647";
}
config false;
description
"The entPhysicalIndex for the TPM.";
reference
"RFC 6933: Entity MIB (Version 4) - entPhysicalIndex";
}
leaf path {
type string;
config false;
description
"Device path to a unique TPM on a device. This can
change across reboots.";
}
leaf compute-node {
if-feature "tpm:mtpm";
type compute-node-ref;
config false;
mandatory true;
description
"Indicates the compute node measured by this TPM.";
}
leaf manufacturer {
type string;
config false;
description
"TPM manufacturer name.";
}
leaf firmware-version {
type identityref {
base taa:cryptoprocessor;
}
mandatory true;
description
"Identifies the cryptoprocessor API set supported. This
is automatically configured by the device and should not
be changed.";
}
uses tpm12-hash-algo {
when "derived-from-or-self(firmware-version, 'taa:tpm12')";
if-feature "taa:tpm12";
refine "tpm12-hash-algo" {
description
"The hash algorithm overwrites the default used for
PCRs on this TPM1.2-compliant cryptoprocessor.";
}
}
leaf-list tpm12-pcrs {
when "derived-from-or-self(../firmware-version, "
+ "'taa:tpm12')";
if-feature "taa:tpm12";
type pcr;
description
"The PCRs that may be extracted from this TPM1.2-
compliant cryptoprocessor.";
}
list tpm20-pcr-bank {
when "derived-from-or-self(../firmware-version, "
+ "'taa:tpm20')";
if-feature "taa:tpm20";
key "tpm20-hash-algo";
description
"Specifies the list of PCRs that may be extracted for
a specific hash algorithm on this TPM2-compliant
cryptoprocessor. A bank is a set of PCRs that are
extended using a particular hash algorithm.";
reference
"TPM2.0-Structures:
Trusted Platform Module Library Part 2: Structures,
Revision 01.83, https://trustedcomputinggroup.org/
wp-content/uploads/TPM-2.0-1.83-Part-2-Structures.pdf,
Section 10.9.7";
leaf tpm20-hash-algo {
type identityref {
base taa:hash;
}
must '/tpm:rats-support-structures'
+ '/tpm:attester-supported-algos'
+ '/tpm:tpm20-hash' {
error-message "This platform does not support "
+ "tpm20-hash-algo";
}
description
"The hash scheme actively being used to hash
one or more TPM2.0 PCRs.";
}
leaf-list pcr-index {
type tpm:pcr;
description
"Defines which TPM2.0 PCRs are available to be
extracted.";
}
}
leaf status {
type enumeration {
enum operational {
value 0;
description
"The TPM currently is running normally and
is ready to accept and process TPM quotes.";
reference
"TPM2.0-Arch: Trusted Platform Module Library
Part 1: Architecture,
https://trustedcomputinggroup.org/wp-content/
uploads/TPM-2.0-1.83-Part-1-Architecture.pdf,
Section 12";
}
enum non-operational {
value 1;
description
"TPM is in a state such as startup or shutdown, which
precludes the processing of TPM quotes.";
}
}
config false;
mandatory true;
description
"TPM chip self-test status.";
}
container certificates {
description
"The TPM's certificates, including EK Certificates
and Attestation Key Certificates.";
list certificate {
key "name";
description
"Three types of certificates can be accessed via
this statement, including Initial Attestation
Key Certificate, Local Attestation Key Certificate, or
Endorsement Key Certificate.";
leaf name {
type string;
description
"An arbitrary name uniquely identifying a certificate
associated with a key within a TPM.";
}
leaf keystore-ref {
if-feature "ks:central-keystore-supported";
if-feature "ks:asymmetric-keys";
type leafref {
path "/ks:keystore/ks:asymmetric-keys"
+ "/ks:asymmetric-key/ks:name";
}
description
"A reference to a specific certificate of an
asymmetric key in the keystore.";
}
leaf type {
type enumeration {
enum endorsement-certificate {
value 0;
description
"Endorsement Key (EK) Certificate type.";
reference
"TPM2.0-Key:
TPM 2.0 Keys for Device Identity and Attestation
https://trustedcomputinggroup.org/wp-content/
uploads/TPM-2p0-Keys-for-Device-Identity-
and-Attestation_v1_r12_pub10082021.pdf,
Section 3.11";
}
enum initial-attestation-certificate {
value 1;
description
"Initial Attestation Key (IAK) Certificate
type.";
reference
"TPM2.0-Key:
TPM 2.0 Keys for Device Identity and Attestation
https://trustedcomputinggroup.org/wp-content/
uploads/TPM-2p0-Keys-for-Device-Identity-
and-Attestation_v1_r12_pub10082021.pdf,
Section 3.2";
}
enum local-attestation-certificate {
value 2;
description
"Local Attestation Key (LAK) Certificate type.";
reference
"TPM2.0-Key:
TPM 2.0 Keys for Device Identity and Attestation
https://trustedcomputinggroup.org/wp-content/
uploads/TPM-2p0-Keys-for-Device-Identity-
and-Attestation_v1_r12_pub10082021.pdf,
Section 3.2";
}
}
description
"Function supported by this certificate from within
the TPM.";
}
}
}
}
}
container attester-supported-algos {
description
"Identifies which TPM algorithms are available for use on an
attesting platform.";
leaf-list tpm12-asymmetric-signing {
when "../../tpm:tpms"
+ "/tpm:tpm[tpm:firmware-version='taa:tpm12']";
if-feature "taa:tpm12";
type identityref {
base taa:asymmetric;
}
description
"Platform-supported TPM1.2 asymmetric algorithms.";
}
leaf-list tpm12-hash {
when "../../tpm:tpms"
+ "/tpm:tpm[tpm:firmware-version='taa:tpm12']";
if-feature "taa:tpm12";
type identityref {
base taa:hash;
}
description
"Platform-supported TPM1.2 hash algorithms.";
}
leaf-list tpm20-asymmetric-signing {
when "../../tpm:tpms"
+ "/tpm:tpm[tpm:firmware-version='taa:tpm20']";
if-feature "taa:tpm20";
type identityref {
base taa:asymmetric;
}
description
"Platform-supported TPM2.0 asymmetric algorithms.";
}
leaf-list tpm20-hash {
when "../../tpm:tpms"
+ "/tpm:tpm[tpm:firmware-version='taa:tpm20']";
if-feature "taa:tpm20";
type identityref {
base taa:hash;
}
description
"Platform-supported TPM2.0 hash algorithms.";
}
}
}
}
<CODE ENDS>Figure 1
2.1.2. ietf-tcg-algs ✨
Okay bestie, this one is the big algorithm table 💅 It encodes the TCG Algorithm definitions from Table 3 of [TCG-Algos], revision 1.32. Because the whole table is its own YANG file inside this document, other YANG modules can totally borrow what's in here 🫶 Specific references to [TPM1.2-Structures], [TPM2.0], [RFC2104], [RFC8017], [RFC8032], [ISO-IEC-9797-1], [ISO-IEC-9797-2], [ISO-IEC-10116], [ISO-IEC-10118-3], [ISO-IEC-14888-3], [ISO-IEC-15946-1], [ISO-IEC-18033-3], [IEEE-Std-1363-2000], [IEEE-Std-1363a-2004], [NIST-FIPS-202], [NIST-SP800-38C], [NIST-SP800-38D], [NIST-SP800-38F], [NIST-SP800-56A], and [NIST-SP800-108] all live inside the YANG module 📚
2.1.2.1. Features 🎀
There are two types of features supported: tpm12 and tpm20. Support for either one means a cryptoprocessor using that kind of TCG TPM API is present on an Attester 🦋 Most commonly, only one type of cryptoprocessor will be available on an Attester, so it's usually just one of these two 💜
2.1.2.2. Identities 🧚
There are three types of identities in this model, and they're giving organized 💖
- Cryptographic functions supported by a TPM algorithm. These include
asymmetric,symmetric,hash,signing,anonymous_signing,encryption_mode,method, andobject_type. The definitions of each of these are in Table 2 of [TCG-Algos] 📖 - API specifications for TPM types:
tpm12andtpm20🔥 - Specific algorithm types. Each algorithm type defines which cryptographic functions may be supported, and on which type of API specification. It is not required that an implementation of a specific TPM will support all algorithm types, so don't panic if yours doesn't 🙈 The contents of each specific algorithm mirror the contents of Table 3 of [TCG-Algos] ✨
2.1.2.3. YANG Module 👑
<CODE BEGINS> file "ietf-tcg-algs@2024-12-05.yang"
module ietf-tcg-algs {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-tcg-algs";
prefix taa;
organization
"IETF RATS (Remote ATtestation procedureS) Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/rats/>
WG List: <mailto:rats@ietf.org>
Author: Eric Voit <mailto:evoit@cisco.com>";
description
"This module defines identities for asymmetric algorithms.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
Copyright (c) 2024 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Revised BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 9684; see the
RFC itself for full legal notices.";
revision 2024-12-05 {
description
"Initial version";
reference
"RFC 9684: A YANG Data Model for Challenge-Response-Based
Remote Attestation (CHARRA) Procedures Using Trusted Platform
Modules (TPMs)";
}
/*****************/
/* Features */
/*****************/
feature tpm12 {
description
"This feature indicates algorithm support for the TPM 1.2 API
per Section 4.8 of TPM1.2-Structures.";
reference
"TPM1.2-Structures: TPM Main Part 2 TPM Structures,
https://trustedcomputinggroup.org/wp-content/uploads/
TPM-Main-Part-2-TPM-Structures_v1.2_rev116_01032011.pdf
TPM_ALGORITHM_ID values, Section 4.8";
}
feature tpm20 {
description
"This feature indicates algorithm support for the TPM 2.0 API
per Section 11.4 of Trusted Platform Module Library Part 1:
Architecture.";
reference
"TPM2.0-Arch: Trusted Platform Module Library Part 1:
Architecture, https://trustedcomputinggroup.org/wp-content/
uploads/TPM-2.0-1.83-Part-1-Architecture.pdf, Section 11.4";
}
/*****************/
/* Identities */
/*****************/
identity asymmetric {
description
"A TCG-recognized asymmetric algorithm with a public and
private key.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 2,
https://trustedcomputinggroup.org/resource/
tcg-algorithm-registry/TCG-_Algorithm_Registry_r1p32_pub";
}
identity symmetric {
description
"A TCG-recognized symmetric algorithm with only a private
key.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 2";
}
identity hash {
description
"A TCG-recognized hash algorithm that compresses input data to
a digest value or indicates a method that uses a hash.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 2";
}
identity signing {
description
"A TCG-recognized signing algorithm";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 2";
}
identity anonymous_signing {
description
"A TCG-recognized anonymous signing algorithm.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 2";
}
identity encryption_mode {
description
"A TCG-recognized encryption mode.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 2";
}
identity method {
description
"A TCG-recognized method such as a mask generation function.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 2";
}
identity object_type {
description
"A TCG-recognized object type.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 2";
}
identity cryptoprocessor {
description
"Base identity identifying a crytoprocessor.";
}
identity tpm12 {
if-feature "tpm12";
base cryptoprocessor;
description
"Supportable by a TPM 1.2.";
reference
"TPM1.2-Structures:
TPM Main Part 2 TPM Structures,
https://trustedcomputinggroup.org/wp-content/uploads/
TPM-Main-Part-2-TPM-Structures_v1.2_rev116_01032011.pdf
TPM_ALGORITHM_ID values, Section 4.8";
}
identity tpm20 {
if-feature "tpm20";
base cryptoprocessor;
description
"Supportable by a TPM 2.0";
reference
"TPM2.0-Structures:
Trusted Platform Module Library Part 2: Structures,
Revision 01.83, https://trustedcomputinggroup.org/
wp-content/uploads/TPM-2.0-1.83-Part-2-Structures.pdf";
}
identity TPM_ALG_RSA {
if-feature "tpm12 or tpm20";
base tpm12;
base tpm20;
base asymmetric;
base object_type;
description
"RSA algorithm.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
RFC 8017. ALG_ID: 0x0001";
}
identity TPM_ALG_TDES {
if-feature "tpm12";
base tpm12;
base symmetric;
description
"Block cipher with various key sizes (Triple Data Encryption
Algorithm, commonly called Triple Data Encryption Standard)
Note: Was banned in TPM 1.2, v94";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 18033-3. ALG_ID: 0x0003";
}
identity TPM_ALG_SHA1 {
if-feature "tpm12 or tpm20";
base hash;
base tpm12;
base tpm20;
description
"SHA1 algorithm - Deprecated due to insufficient cryptographic
protection. However, it is still useful for hash algorithms
where protection is not required.";
reference
"TCG-Algos: TCG Algorithm Registry Rev1.34, Table 3, and
ISO/IEC 10118-3. ALG_ID: 0x0004";
}
identity TPM_ALG_HMAC {
if-feature "tpm12 or tpm20";
base tpm12;
base tpm20;
base hash;
base signing;
description
"Hash Message Authentication Code (HMAC) algorithm.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 9797-2, and
RFC 2104. ALG_ID: 0x0005";
}
identity TPM_ALG_AES {
if-feature "tpm12";
base tpm12;
base symmetric;
description
"The AES algorithm with various key sizes.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 18033-3. ALG_ID: 0x0006";
}
identity TPM_ALG_MGF1 {
if-feature "tpm20";
base tpm20;
base hash;
base method;
description
"Hash-based mask-generation function.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
IEEE Std 1363-2000, and
IEEE Std 1363a-2004.
ALG_ID: 0x0007";
}
identity TPM_ALG_KEYEDHASH {
if-feature "tpm20";
base tpm20;
base hash;
base object_type;
description
"An encryption or signing algorithm using a keyed hash. These
may use XOR for encryption or an HMAC for signing and may
also refer to a data object that is neither signing nor
encrypting.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3.
ALG_ID: 0x0008";
}
identity TPM_ALG_XOR {
if-feature "tpm12 or tpm20";
base tpm12;
base tpm20;
base hash;
base symmetric;
description
"The XOR encryption algorithm.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3.
ALG_ID: 0x000A";
}
identity TPM_ALG_SHA256 {
if-feature "tpm20";
base tpm20;
base hash;
description
"The SHA-256 algorithm.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 10118-3. ALG_ID: 0x000B";
}
identity TPM_ALG_SHA384 {
if-feature "tpm20";
base tpm20;
base hash;
description
"The SHA-384 algorithm.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 10118-3. ALG_ID: 0x000C";
}
identity TPM_ALG_SHA512 {
if-feature "tpm20";
base tpm20;
base hash;
description
"The SHA-512 algorithm.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 10118-3. ALG_ID: 0x000D";
}
identity TPM_ALG_NULL {
if-feature "tpm20";
base tpm20;
description
"Null algorithm.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3.
ALG_ID: 0x0010";
}
identity TPM_ALG_SM3_256 {
if-feature "tpm20";
base tpm20;
base hash;
description
"The ShangMi 3 (SM3) hash algorithm.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 10118-3:2018. ALG_ID: 0x0012";
} identity TPM_ALG_SM4 {
if-feature "tpm20";
base tpm20;
base symmetric;
description
"ShangMi 4 (SM4) symmetric block cipher.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3.
ALG_ID: 0x0013";
}
identity TPM_ALG_RSASSA {
if-feature "tpm20";
base tpm20;
base asymmetric;
base signing;
description
"Signature algorithm defined in Section 8.2
(RSASSA-PKCS1-v1_5) of RFC 8017.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
RFC 8017. ALG_ID: 0x0014";
}
identity TPM_ALG_RSAES {
if-feature "tpm20";
base tpm20;
base asymmetric;
base encryption_mode;
description
"Signature algorithm defined in Section 7.2
(RSAES-PKCS1-v1_5) of RFC 8017.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
RFC 8017. ALG_ID: 0x0015";
}
identity TPM_ALG_RSAPSS {
if-feature "tpm20";
base tpm20;
base asymmetric;
base signing;
description
"Padding algorithm defined in Section 8.1 (RSASSA-PSS)
of RFC 8017.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
RFC 8017. ALG_ID: 0x0016";
}
identity TPM_ALG_OAEP {
if-feature "tpm20";
base tpm20;
base asymmetric;
base encryption_mode;
description
"Padding algorithm defined in Section 7.1 (RSAES-OAEP)
of RFC 8017.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
RFC 8017. ALG_ID: 0x0017";
}
identity TPM_ALG_ECDSA {
if-feature "tpm20";
base tpm20;
base asymmetric;
base signing;
description
"Signature algorithm using elliptic curve cryptography (ECC).";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 14888-3. ALG_ID: 0x0018";
}
identity TPM_ALG_ECDH {
if-feature "tpm20";
base tpm20;
base asymmetric;
base method;
description
"Secret sharing using ECC.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
NIST SP800-56A. ALG_ID: 0x0019";
}
identity TPM_ALG_ECDAA {
if-feature "tpm20";
base tpm20;
base asymmetric;
base signing;
base anonymous_signing;
description
"Elliptic-curve-based, anonymous signing scheme.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
TCG TPM 2.0 Library. ALG_ID: 0x001A";
}
identity TPM_ALG_SM2 {
if-feature "tpm20";
base tpm20;
base asymmetric;
base signing;
base encryption_mode;
base method;
description
"SM2 - depending on context, either an elliptic-curve based,
signature algorithm, an encryption scheme, or a key exchange
protocol.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3.
ALG_ID: 0x001B";
}
identity TPM_ALG_ECSCHNORR {
if-feature "tpm20";
base tpm20;
base asymmetric;
base signing;
description
"Elliptic-curve-based Schnorr signature.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3.
ALG_ID: 0x001C";
}
identity TPM_ALG_ECMQV {
if-feature "tpm20";
base tpm20;
base asymmetric;
base method;
description
"Two-phase elliptic-curve key.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
NIST SP800-56A. ALG_ID: 0x001D";
}
identity TPM_ALG_KDF1_SP800_56A {
if-feature "tpm20";
base tpm20;
base hash;
base method;
description
"Concatenation key derivation function.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
NIST SP800-56A (approved alternative1) Section 5.8.1.
ALG_ID: 0x0020";
}
identity TPM_ALG_KDF2 {
if-feature "tpm20";
base tpm20;
base hash;
base method;
description
"Key derivation function.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
IEEE 1363a-2004, KDF2, Section 13.2. ALG_ID: 0x0021";
}
identity TPM_ALG_KDF1_SP800_108 {
base TPM_ALG_KDF2;
description
"A key derivation method.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3 and
NIST SP800-108, Section 4.1, KDF. ALG_ID: 0x0022";
}
identity TPM_ALG_ECC {
if-feature "tpm20";
base tpm20;
base asymmetric;
base object_type;
description
"Prime field ECC.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 15946-1. ALG_ID: 0x0023";
}
identity TPM_ALG_SYMCIPHER {
if-feature "tpm20";
base tpm20;
base symmetric;
base object_type;
description
"Object type for a symmetric block cipher.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
TCG TPM 2.0 Library. ALG_ID: 0x0025";
}
identity TPM_ALG_CAMELLIA {
if-feature "tpm20";
base tpm20;
base symmetric;
description
"The Camellia algorithm.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 18033-3. ALG_ID: 0x0026";
}
identity TPM_ALG_SHA3_256 {
if-feature "tpm20";
base tpm20;
base hash;
description
"ISO/IEC 10118-3 - the SHA-256 algorithm.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
NIST FIPS 202. ALG_ID: 0x0027";
}
identity TPM_ALG_SHA3_384 {
if-feature "tpm20";
base tpm20;
base hash;
description
"The SHA-384 algorithm.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
NIST FIPS 202. ALG_ID: 0x0028";
}
identity TPM_ALG_SHA3_512 {
if-feature "tpm20";
base tpm20;
base hash;
description
"The SHA-512 algorithm.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
NIST FIPS 202. ALG_ID: 0x0029";
}
identity TPM_ALG_CMAC {
if-feature "tpm20";
base tpm20;
base symmetric;
base signing;
description
"Block Cipher-based Message Authentication Code (CMAC).";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 9797-1:2011, Algorithm 5. ALG_ID: 0x003F";
}
identity TPM_ALG_CTR {
if-feature "tpm20";
base tpm20;
base symmetric;
base encryption_mode;
description
"Counter mode.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 10116. ALG_ID: 0x0040";
}
identity TPM_ALG_OFB {
base tpm20;
base symmetric;
base encryption_mode;
description
"Output Feedback mode.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 10116. ALG_ID: 0x0041";
}
identity TPM_ALG_CBC {
if-feature "tpm20";
base tpm20;
base symmetric;
base encryption_mode;
description
"Cipher Block Chaining mode.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 10116. ALG_ID: 0x0042";
}
identity TPM_ALG_CFB {
if-feature "tpm20";
base tpm20;
base symmetric;
base encryption_mode;
description
"Cipher Feedback mode.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 10116. ALG_ID: 0x0043";
}
identity TPM_ALG_ECB {
if-feature "tpm20";
base tpm20;
base symmetric;
base encryption_mode;
description
"Electronic Codebook mode.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
ISO/IEC 10116. ALG_ID: 0x0044";
}
identity TPM_ALG_CCM {
if-feature "tpm20";
base tpm20;
base symmetric;
base signing;
base encryption_mode;
description
"Counter with Cipher Block Chaining--Message Authentication
Code (CCM).";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
NIST SP800-38C. ALG_ID: 0x0050";
}
identity TPM_ALG_GCM {
if-feature "tpm20";
base tpm20;
base symmetric;
base signing;
base encryption_mode;
description
"Galois/Counter Mode (GCM).";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
NIST SP800-38D. ALG_ID: 0x0051";
}
identity TPM_ALG_KW {
if-feature "tpm20";
base tpm20;
base symmetric;
base signing;
base encryption_mode;
description
"AES Key Wrap (KW).";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
NIST SP800-38F. ALG_ID: 0x0052";
}
identity TPM_ALG_KWP {
if-feature "tpm20";
base tpm20;
base symmetric;
base signing;
base encryption_mode;
description
"AES Key Wrap with Padding (KWP).";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
NIST SP800-38F. ALG_ID: 0x0053";
}
identity TPM_ALG_EAX {
if-feature "tpm20";
base tpm20;
base symmetric;
base signing;
base encryption_mode;
description
"Authenticated-Encryption Mode.";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
NIST SP800-38F. ALG_ID: 0x0054";
}
identity TPM_ALG_EDDSA {
if-feature "tpm20";
base tpm20;
base asymmetric;
base signing;
description
"Edwards-curve Digital Signature Algorithm (PureEdDSA).";
reference
"TCG-Algos: TCG Algorithm Registry, Rev1.34, Table 3, and
RFC 8032. ALG_ID: 0x0060";
}
}
<CODE ENDS>Note that not all cryptographic functions are required for use by ietf-tpm-remote-attestation.yang. However, the full definition of Table 3 of [TCG-Algos] will allow use by additional YANG specifications.
3. IANA Considerations 🦋
Okay, so this part is basically the paperwork bit 📋. The doc asks for two XML namespace URIs to be registered in the [XML-Registry], following [RFC3688]. Both have the IESG as the registrant contact, and the XML field is N/A because these URIs are just XML namespaces 💅.
URI: urn:ietf:params:xml:ns:yang:ietf-tpm-remote-attestation
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-tcg-algs
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.Then there's the YANG side 🌸. The doc registers two YANG modules in the [YANG-Parameters] registry, following Section 14 of [RFC6020]. Each one has a name, a namespace, a prefix, and a reference to the draft (in RFC form), so it's all nice and tidy ✨.
Name: ietf-tpm-remote-attestation
Namespace: urn:ietf:params:xml:ns:yang:ietf-tpm-remote-attestation
Prefix: tpm
Reference: draft-ietf-rats-yang-tpm-charra (RFC form)
Name: ietf-tcg-algs
Namespace: urn:ietf:params:xml:ns:yang:ietf-tcg-algs
Prefix: taa
Reference: draft-ietf-rats-yang-tpm-charra (RFC form)4. Security Considerations 🔐✨
okay bestie, this is the part where the RFC gets serious about who can touch what 💅 the YANG module ietf-tpm-remote-attestation.yang is built to be reached through network management protocols like NETCONF [RFC6241] or RESTCONF [RFC8040]. the lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. the lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446] 🦋
the Network Configuration Access Control Model (NACM) [RFC8341] is how you restrict particular NETCONF or RESTCONF users to a preconfigured subset of the protocol operations and content. it's giving access control realness 🔒
these nodes are the ones to watch, no cap 👀
- in the 'tpms' container, the 'certificates' will expose certificates used for attestation, which could let someone pick a certificate that might be compromised. the 'type' could also be misconfigured to represent a different type of key, and that might change how a Verifier evaluates the results 😭
- within the 'attester-supported-algos' container, each leaf-list will expose and potentially allow changing the encryption algorithms a device supports 🫶
there are a bunch of data nodes in this module that are writable, creatable, and deletable (that's _config true_, which is the default) 🎀 these may be sensitive or vulnerable in some network environments. write operations (like _edit-config_) to these nodes without proper protection can mess with network operations, so please be careful 🙈 here's the sensitivity breakdown:
Container '/rats-support-structures/attester-supported-algos': 'tpm12-asymmetric-signing', 'tpm12-hash', 'tpm20-asymmetric-signing', and 'tpm20-hash'. all of these could get populated with algorithms the physical TPM installed by the equipment vendor doesn't actually support. a vendor should restrict the ability to configure unsupported algorithms 🚫
Container: '/rats-support-structures/tpms': 'name' is shown as 'rw', but it's system generated, so an operator should not be able to add or remove a TPM from the configuration 🧚
'tpm20-pcr-bank': it's possible to configure PCRs that aren't being extended by system software for extraction. that could unnecessarily use TPM resources 🌸
'certificates': it's possible to provision a certificate that doesn't correspond to an AIK within the TPM 1.2, or to an Attestation Key (AK) within the TPM 2.0. if that happens, calls to an RPC requesting that specific certificate could end up with either no response or a response from an unexpected TPM. that's a whole mess 💀
RPC 'tpm12-challenge-response-attestation': the receiver of the RPC response MUST verify that the certificate is for an active AIK, i.e., the certificate has been confirmed by a third party as being able to support Attestation on the targeted TPM 1.2. no skipping this one bestie 👑
RPC 'tpm20-challenge-response-attestation': the receiver of the RPC response MUST verify that the certificate is for an active AK, i.e., the private key confirmation of the quote signature within the RPC response has been confirmed by a third party to belong to an entity legitimately able to perform Attestation on the targeted TPM 2.0. 🔥
RPC 'log-retrieval': requesting a large volume of logs from the Attester could require significant system resources and create a denial of service 😭🌈
information collected through the RPCs above could reveal specific versions of software and configurations of endpoints, which could identify vulnerabilities on those systems. so RPCs SHOULD be protected by NACM [RFC8341] with a default setting of deny-all, to limit extraction of attestation data to only authorized Verifiers 🔐💜
for the YANG module ietf-tcg-algs.yang, please use care when picking specific algorithms 🧐 the introductory section of [TCG-Algos] highlights that some algorithms should be considered legacy, and recommends implementers and adopters diligently evaluate available information (governmental, industrial, and academic research) before selecting an algorithm for use 📚
some of the readable data nodes in this YANG module may be sensitive or vulnerable too, so it's important to control read access (via get, get-config, or notification) to them 👀 these are the subtrees and their sensitivity breakdown:
Event logs (bios-log, ima-log, netequip-boot-log) typically contain hash values (digests) of running boot and OS software. passive attackers can use those hashes to identify software versions and launch targeted attacks on known vulnerabilities. so bios-log, ima-log, and netequip-boot-log are considered sensitive 🥺🍓
some of the RPC operations in this module may also be sensitive or vulnerable, so controlling access to them is a must 🛡️ here's the rundown:
The 'log-retrieval' RPC operation is considered sensitive because it enables retrieval of logs (bios-log, ima-log, netequip-boot-log) that typically contain hash values (digests) of running boot and OS software. that lets outsiders figure out the specifics of loaded software, including BIOS and operating system software 🫣
the other two RPC operations, 'tpm20-challenge-response-attestation' and 'tpm12-challenge-response-attestation', will expose values showing the device's internal operational state. those values could also be correlated to specifics of running software 💖
5. References 📚
5.1. Normative References
[BIOS-Log] Trusted Computing Group, "TCG PC Client Platform Firmware Profile Specification", Family "2.0" Level 00 Revision 1.03 Version 51, 1 May 2017, <https://trustedcomputinggroup.org/wp-content/uploads/PC-C lientSpecific_Platform_Profile_for_TPM_2p0_Systems_v51.pdf>.
[CEL] Trusted Computing Group, "Canonical Event Log Format", Version 1.0 Revision 0.41, 25 February 2022, <https://trustedcomputinggroup.org/wp-content/uploads/TCG_IWG_CEL_v1_r0p41_pub.pdf>.
[IEEE-Std-1363-2000] IEEE, "IEEE Standard Specifications for Public-Key Cryptography", IEEE Std 1363-2000, DOI 10.1109/IEEESTD.2000.92292, August 2000, <https://ieeexplore.ieee.org/document/891000>.
[IEEE-Std-1363a-2004] IEEE, "IEEE Standard Specifications for Public-Key Cryptography - Amendment 1: Additional Techniques", IEEE Std 1363a-2004, DOI 10.1109/IEEESTD.2004.94612, September 2004, <https://ieeexplore.ieee.org/document/1335427>.
[ISO-IEC-10116] ISO/IEC, "Information technology - Security techniques - Modes of operation for an n-bit block cipher", Edition 4, ISO/IEC 10116:2017, July 2017, <https://www.iso.org/standard/64575.html>.
[ISO-IEC-10118-3] ISO/IEC, "IT Security techniques - Hash-functions - Part 3: Dedicated hash-functions", Edition 4, ISO/IEC 10118-3:2018, October 2018, <https://www.iso.org/standard/67116.html>.
[ISO-IEC-14888-3] ISO/IEC, "Security techniques - Digital signatures with appendix - Part 3: Discrete logarithm based mechanisms", Edition 4, ISO/IEC 14888-3:2018, November 2018, <https://www.iso.org/standard/76382.html>.
[ISO-IEC-15946-1] ISO/IEC, "Information technology - Security techniques - Cryptographic techniques based on elliptic curves - Part 1: General", Edition 3, ISO/IEC 15946-1:2016, July 2016, <https://www.iso.org/standard/65480.html>.
[ISO-IEC-18033-3] ISO/IEC, "Information technology - Security techniques - Encryption algorithms - Part 3: Block ciphers", Edition 2, ISO/IEC 18033-3:2010, December 2010, <https://www.iso.org/standard/54531.html>.
[ISO-IEC-9797-1] ISO/IEC, "Information technology - Security techniques - Message Authentication Codes (MACs) - Part 1: Mechanisms using a block cipher", Edition 2, ISO/IEC 9797-1:2011, November 2011, <https://www.iso.org/standard/50375.html>.
[ISO-IEC-9797-2] ISO/IEC, "Information security - Message authentication codes (MACs) - Part 2: Mechanisms using a dedicated hash-function", Edition 3, ISO/IEC 9797-2:2021, June 2021, <https://www.iso.org/standard/75296.html>.
[NIST-FIPS-202] NIST, "SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions", NIST FIPS 202, DOI 10.6028/NIST.FIPS.202, August 2015, <https://csrc.nist.gov/publications/detail/fips/202/final>.
[NIST-SP800-108] Chen, L., "Recommendation for Key Derivation Using Pseudorandom Functions", DOI 10.6028/NIST.SP.800-108r1-upd1, NIST SP 800-108r1-upd1, February 2024, <https://csrc.nist.gov/pubs/sp/800/108/r1/upd1/final>.
[NIST-SP800-38C] Dworkin, M., "Recommendation for Block Cipher Modes of Operation: the CCM Mode for Authentication and Confidentiality", NIST SP 800-38C, DOI 10.6028/NIST.SP.800-38C, July 2007, <https://csrc.nist.gov/publications/detail/sp/800-38c/final>.
[NIST-SP800-38D] Dworkin, M., "Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC", NIST SP 800-38D, DOI 10.6028/NIST.SP.800-38D, November 2007, <https://csrc.nist.gov/publications/detail/sp/800-38d/final>.
[NIST-SP800-38F] Dworkin, M., "Recommendation for Block Cipher Modes of Operation: Methods for Key Wrapping", NIST SP 800-38F, DOI 10.6028/NIST.SP.800-38F, December 2012, <https://csrc.nist.gov/publications/detail/sp/800-38f/final>.
[NIST-SP800-56A] Barker, E., Chen, L., Roginsky, A., Vassilev, A., and R. Davis, "Recommendation for Pair-Wise Key-Establishment Schemes Using Discrete Logarithm Cryptography", NIST SP 800-56A Rev. 3, DOI 10.6028/NIST.SP.800-56Ar3, April 2018, <https://csrc.nist.gov/publications/detail/sp/800-56a/rev-3/final>.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-Hashing for Message Authentication", RFC 2104, DOI 10.17487/RFC2104, February 1997, <https://www.rfc-editor.org/info/rfc2104>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, <https://www.rfc-editor.org/info/rfc3688>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, https://www.rfc-editor.org/info/rfc6020.
[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.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, https://www.rfc-editor.org/info/rfc6242.
[RFC6933] Bierman, A., Romascanu, D., Quittek, J., and M. Chandramouli, "Entity MIB (Version 4)", RFC 6933, DOI 10.17487/RFC6933, May 2013, https://www.rfc-editor.org/info/rfc6933.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013, https://www.rfc-editor.org/info/rfc6991.
[RFC8017] Moriarty, K., Ed., Kaliski, B., Jonsson, J., and A. Rusch, "PKCS #1: RSA Cryptography Specifications Version 2.2", RFC 8017, DOI 10.17487/RFC8017, November 2016, https://www.rfc-editor.org/info/rfc8017.
[RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital Signature Algorithm (EdDSA)", RFC 8032, DOI 10.17487/RFC8032, January 2017, https://www.rfc-editor.org/info/rfc8032.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, https://www.rfc-editor.org/info/rfc8040.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, https://www.rfc-editor.org/info/rfc8174.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018, https://www.rfc-editor.org/info/rfc8341.
[RFC8348] Bierman, A., Bjorklund, M., Dong, J., and D. Romascanu, "A YANG Data Model for Hardware Management", RFC 8348, DOI 10.17487/RFC8348, March 2018, https://www.rfc-editor.org/info/rfc8348.
[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.
[RFC9334] Birkholz, H., Thaler, D., Richardson, M., Smith, N., and W. Pan, "Remote ATtestation procedureS (RATS) Architecture", RFC 9334, DOI 10.17487/RFC9334, January 2023, https://www.rfc-editor.org/info/rfc9334.
[RFC9642] Watsen, K., "A YANG Data Model for a Keystore", RFC 9642, DOI 10.17487/RFC9642, October 2024, https://www.rfc-editor.org/info/rfc9642.
[RFC9683] Fedorkow, G. C., Ed., Voit, E., and J. Fitzgerald-McKay, "Remote Integrity Verification of Network Devices Containing Trusted Platform Modules", RFC 9683, DOI 10.17487/RFC9683, December 2024, https://www.rfc-editor.org/info/rfc9683.
[TCG-Algos] Trusted Computing Group, "TCG Algorithm Registry", Family "2.0" Level 00 Revision 01.34, 24 August 2023, https://trustedcomputinggroup.org/wp-content/uploads/TCG-Algorithm-Registry-Revision-1.34_pub-1.pdf.
[TPM1.2] Trusted Computing Group, "TPM 1.2 Main Specification", TPM Main Specification Level 2 Version 1.2, Revision 116, 1 March 2011, https://trustedcomputinggroup.org/resource/tpm-main-specification/.
[TPM1.2-Commands] Trusted Computing Group, "TPM Main Part 3 Commands", TPM Main Specification Level 2 Version 1.2, Revision 116, 1 March 2011, https://trustedcomputinggroup.org/wp-content/uploads/TPM-Main-Part-3-Commands_v1.2_rev116_01032011.pdf.
[TPM1.2-Structures] Trusted Computing Group, "TPM Main Part 2 TPM Structures", TPM Main Specification Level 2 Version 1.2, Revision 116, 1 March 2011, https://trustedcomputinggroup.org/wp-content/uploads/TPM-Main-Part-2-TPM-Structures_v1.2_rev116_01032011.pdf.
[TPM2.0] Trusted Computing Group, "TPM 2.0 Library", Trusted Platform Module Library Specification, Family "2.0", Level 00, Revision 01.83, March 2024, https://trustedcomputinggroup.org/resource/tpm-library-specification/.
[TPM2.0-Arch] Trusted Computing Group, "Trusted Platform Module Library Part 1: Architecture", Family "2.0", Level 00, Revision 01.83, 25 January 2024, https://trustedcomputinggroup.org/wp-content/uploads/TPM-2.0-1.83-Part-1-Architecture.pdf.
[TPM2.0-Key] Trusted Computing Group, "TPM 2.0 Keys for Device Identity and Attestation", Version 1.00, Revision 12, 8 October 2021, https://trustedcomputinggroup.org/wp-content/uploads/TPM-2p0-Keys-for-Device-Identity-and-Attestation_v1_r12_pub10082021.pdf.
[TPM2.0-Structures] Trusted Computing Group, "Trusted Platform Module Library Part 2: Structures", Family "2.0", Level 00, Revision 01.83, 25 January 2024, https://trustedcomputinggroup.org/wp-content/uploads/TPM-2.0-1.83-Part-2-Structures.pdf.
[UEFI-Secure-Boot] Unified Extensible Firmware Interface (UEFI) Forum, Inc., "Unified Extensible Firmware Interface (UEFI) Specification", Section 32.1: Secure Boot, Version 2.10, 29 August 2022, https://uefi.org/sites/default/files/resources/UEFI_Spec_2_10_Aug29.pdf.
5.2. Informative References 📚✨
Now for the "good to know, not required" crew 💅 These ones give you background and context, but nothing here is a must-have for implementing the spec 🫶
[IMA-Template-Management] The kernel development community, "IMA Template Management Mechanism", Linux Kernel 6.11, 15 September 2024, https://www.kernel.org/doc/html/v6.11/security/IMA-templates.html.
[NIST-915121] NIST, "True Randomness Can't be Left to Chance: Why entropy is important for information security", https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915121.
[RATS-Interaction-Models] Birkholz, H., Eckel, M., Pan, W., and E. Voit, "Reference Interaction Models for Remote Attestation Procedures", Work in Progress, Internet-Draft, draft-ietf-rats-reference-interaction-models-11, 22 July 2024, https://datatracker.ietf.org/doc/html/draft-ietf-rats-reference-interaction-models-11.
[XML-Registry] IANA, "IETF XML Registry", https://www.iana.org/assignments/xml-registry/.
[YANG-Parameters] IANA, "YANG Parameters", https://www.iana.org/assignments/yang-parameters/.
Appendix A. Integrity Measurement Architecture (IMA) 🛡️🌸
Okay, bestie, this appendix is the IMA deep dive and it is seriously giving main character energy 👑
IMA takes the whole vibe of Measured Boot [TPM2.0-Arch] and Secure Boot [UEFI-Secure-Boot] and brings it to Linux, where it's applied to operating system applications and files 💖 It's been part of the Linux integrity subsystem of the Linux kernel since 2009 (kernel version 2.6.30) ✨ The IMA mechanism that the YANG module in this spec represents is rooted in kernel version 5.16 [IMA-Template-Management] 🧚 So basically, IMA protects system integrity by collecting (aka measuring) and storing measurements of files before they run. In IETF RATS land those measurements are called Claims 🦋 Then they can be used later, while the system is running, in remote attestation procedures. IMA also supports the Appraisal of Evidence (which includes measurement Claims) by using Reference Values stored in extended file attributes 🫶
Now the Stored Measurement Log (SML) 📜 This is an ordered list with no duplicates, kept in kernel space, covering all the files that got measured before execution since the OS booted. IMA can technically run without a TPM, but it's usually paired with one so the SML is anchored in hardware-protected storage, meaning the PCRs that TPMs provide 🔥 IMA exposes the SML in both binary and ASCII forms in the Linux security file system _securityfs_ at /sys/kernel/security/ima/ 💅
Next up, IMA templates 🎀 These define the format of the SML, which means which fields show up in each log record. Examples include file path, file hash, user ID, group ID, file signature, and extended file attributes 💜 IMA comes with a set of predefined template formats, and it also lets you make a custom format built from template fields that IMA supports. Usually the template gets picked by boot arguments passed to the kernel. You can also hard-code the format into custom kernels instead 🌈 Templates and fields are extensible in the kernel source code, so more template fields can be added down the road 🍓
And IMA policies 🧁 These decide which files get measured, using the IMA policy language. Built-in policies can be passed in as boot arguments to the kernel, while custom IMA policies can be defined once at runtime or hard-coded into a custom kernel. Here's the tea: if no policy is defined, no measurements are taken and IMA is effectively disabled 💀
Last but not least, the CEL spec. Table 16 of the Canonical Event Log (CEL) specification [CEL] has a full breakdown of the content fields in the Linux IMA TLV format 🙈 And CEL Section 5.1.6 shows how templates can be used to enable extended or customized IMA TLV formats ⭐
Appendix B. IMA for Network Equipment Boot Logs 🖥️✨
okay bestie, so this appendix is about how network gear can run similar IMA-protected functions to generate measurements (aka Claims) about its boot process 🦋 That's what enables remote attestation! Network Equipment Boot Logs smush the measuring and logging of boot components and operating system components (executables and files) into ONE log file, and it's formatted exactly like the IMA format 💅 Heads up though: the way boot components get logged in this scheme is different from the boot logging strategy described elsewhere in this document, so don't mix them up 🙈
During the boot process of the network device, aka from BIOS all the way to the end of the operating system and user-space, every file that gets executed can be measured and logged, in the order it ran 🧚 When the Verifier kicks off a remote attestation process (like the challenge-response remote attestation defined in this document), the network equipment becomes the Attester. It can then send the Verifier the Claims that make up the measurement log, plus the matching PCR values (Evidence) from a TPM 🔥
The Verifier can check the integrity (compliance with the Reference Values) of each executed file by comparing its measured value to the Reference Value. Since it knows the execution order, the Verifier can compute a PCR Reference Value by replaying the log 🌈 Then it compares that to the measurement log Claims it got alongside the PCR Evidence, so it can judge how trustworthy things are with respect to the intended operational state. Iconic behavior, honestly 👑
Network equipment usually runs multiple components in parallel. That's true during the operating system loading phase, and even during the BIOS boot phase 😭 With this measurement log mechanism, network equipment can take on the Attester role and prove to the Verifier that its boot process is trustworthy ✨ Using the measurement log, Verifiers can pinpoint exactly which log entries don't match, which helps them infer which components might have been tampered with. Detective energy 🕵️♀️💜
Last but not least, this also works for scenarios where files on the Attester get modified and then executed during the boot phase (think updating or patching) 🎀 You just update the right Reference Values in the Reference Integrity Manifests, which tell Verifiers how an Attester is composed. No drama, just vibes 🫶
Authors' Addresses
Henk Birkholz
Fraunhofer SIT | ATHENE Center
Rheinstrasse 75
64295 Darmstadt
Germany
Email: henk.birkholz@ietf.contact
Michael Eckel
Fraunhofer SIT | ATHENE Center
Rheinstrasse 75
64295 Darmstadt
Germany
Email: michael.eckel@sit.fraunhofer.de
Shwetha Bhandari
ThoughtSpot
Email: shwetha.bhandari@thoughtspot.com
Eric Voit
Cisco Systems
Email: evoit@cisco.com
Bill Sulzen
Cisco Systems
Email: bsulzen@cisco.com
Liang Xia (Frank)
Huawei Technologies
Yuhuatai District
101 Software Avenue
Nanjing
Jiangsu, 210012
China
Email: Frank.Xialiang@huawei.com
Tom Laffey
Hewlett Packard Enterprise
Email: tom.laffey@hpe.com
Guy C. Fedorkow
Juniper Networks
10 Technology Park Drive
Westford, Massachusetts 01886
United States of America
Email: gfedorkow@juniper.net📦 where this page comes from
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