Internet DRAFT - draft-tschofenig-rats-aiss-token
draft-tschofenig-rats-aiss-token
RATS H. Tschofenig
Internet-Draft Arm Limited
Intended status: Informational A. Kankaanpää
Expires: 24 October 2022 N. Bowler
Synopsys
T. Khandelwal
Arm Limited
22 April 2022
Automatic Integration of Secure Silicon (AISS) Attestation Token
draft-tschofenig-rats-aiss-token-00
Abstract
This specification defines a profile of the Entity Attestation Token
(EAT) for use in special System-on-Chip (SoC) designs that are
generated automatically utilizing a methodology currently developed
in a DARPA funded project.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on 24 October 2022.
Copyright Notice
Copyright (c) 2022 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/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. Claims . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Nonce . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Instance ID . . . . . . . . . . . . . . . . . . . . . . . 4
3.3. Implementation ID . . . . . . . . . . . . . . . . . . . . 4
3.4. Security Lifecycle . . . . . . . . . . . . . . . . . . . 5
3.5. Boot Odometer . . . . . . . . . . . . . . . . . . . . . . 6
3.6. Watermark . . . . . . . . . . . . . . . . . . . . . . . . 6
3.7. Profile Definition . . . . . . . . . . . . . . . . . . . 7
4. Token Encoding and Signing . . . . . . . . . . . . . . . . . 7
5. Freshness Model . . . . . . . . . . . . . . . . . . . . . . . 8
6. Collated CDDL . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Verification . . . . . . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8.1. Claim Registration . . . . . . . . . . . . . . . . . . . 10
8.1.1. Security Lifecycle Claim . . . . . . . . . . . . . . 10
8.1.2. Implementation ID Claim . . . . . . . . . . . . . . . 10
8.1.3. Watermark Claim . . . . . . . . . . . . . . . . . . . 10
8.2. Media Type Registration . . . . . . . . . . . . . . . . . 11
8.3. CoAP Content-Formats Registration . . . . . . . . . . . . 12
8.3.1. Registry Contents . . . . . . . . . . . . . . . . . . 12
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
9.1. Normative References . . . . . . . . . . . . . . . . . . 12
9.2. Informative References . . . . . . . . . . . . . . . . . 13
Appendix A. Example . . . . . . . . . . . . . . . . . . . . . . 14
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction
The DARPA-funded project Automated Implementation of Secure Silicon
(AISS) is aimed at making scalable on-chip security pervasive. The
objective is to develop ways to automate the process of adding
security into integrated circuits.
If successful, AISS will allow security to be inexpensively
incorporated into chip designs with minimal effort and expertise,
ultimately making scalable on-chip security ubiquitous. The project
seeks to create a novel, automated chip design flow that will allow
the security mechanisms to scale consistently with the goals of the
design.
As a minimal component, the generated chip designs must offer
attestation capabilities.
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This specification describes the minimal claim set offered by an
attestation token conforming to the Entity Attestation Token (EAT)
specification. This attestation token is, on request, provided to a
Verifier.
2. Conventions and Definitions
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.
The following term is used in this document:
RoT Root of Trust, the minimal set of software, hardware and data
that has to be implicitly trusted in the platform - there is no
software or hardware at a deeper level that can verify that the
Root of Trust is authentic and unmodified. An example of RoT is
an initial bootloader in ROM, which contains cryptographic
functions and credentials, running on a specific hardware
platform.
3. Claims
This section describes the claims to be used in an AISS attestation
token.
CDDL [RFC8610] along with text descriptions is used to define each
claim independent of encoding. The following CDDL type(s) are reused
by different claims:
aiss-hash-type = bytes .size 32 / bytes .size 48 / bytes .size 64
3.1. Nonce
The Nonce claim is used to carry the challenge provided by the caller
to demonstrate freshness of the generated token.
The EAT [I-D.ietf-rats-eat] nonce (claim key 10) is used. The
following constraints apply to the nonce-type:
* The length MUST be either 32, 48, or 64 bytes.
* Only a single nonce value is conveyed. Per [I-D.ietf-rats-eat]
the array notation is not used for encoding the nonce value.
This claim MUST be present in an AISS attestation token.
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aiss-nonce = (
nonce-label => aiss-hash-type
)
3.2. Instance ID
The Instance ID claim represents the unique identifier of the
attestation key.
The EAT ueid (claim key 256) of type RAND is used. The following
constraints apply to the ueid-type:
* The length MUST be 17 bytes.
* The first byte MUST be 0x01 (RAND) followed by the 16-bytes random
value, which may be created by hashing the key identifier or may
be the key identifier itself.
This claim MUST be present in an AISS attestation token.
aiss-instance-id-type = bytes .size 33
aiss-instance-id = (
ueid-label => aiss-instance-id-type
)
3.3. Implementation ID
The Implementation ID claim uniquely identifies the implementation of
the immutable RoT. A verification service uses this claim to locate
the details of the RoT implementation from a manufacturer. Such
details are used by a verification service to determine the security
properties or certification status of the RoT implementation.
The value and format of the ID is decided by the manufacturer or a
particular certification scheme. For example, the ID could take the
form of a product serial number, database ID, or other appropriate
identifier.
This claim MUST be present in an AISS attestation token.
Note that this identifies the RoT implementation, not a particular
instance. The Instance ID claim, see Section 3.2, uniquely
identifies an instance.
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aiss-implementation-id-type = bytes .size 32
aiss-implementation-id = (
aiss-implementation-id-label => aiss-implementation-id-type
)
3.4. Security Lifecycle
The Security Lifecycle claim represents the current lifecycle state
of the RoT. The state is represented by an unsigned integer.
The lifecycle states are illustrated in Figure 1. When the device is
deployed, a Verifier can only trust reports when the lifecycle state
is in "Secured" and "Non-RoT Debug" states. The states "Testing" and
"Provisioning" are utilized during manufacturing. A device is in
"Decommisioned" state when it is retired.
This claim MUST be present in an AISS attestation token.
.-------------. .-------------.
+ Testing |-------> Provisioning |
'-------------' '------+------'
| .------------------.
| | |
v v |
.---------. |
.---------+ Secured +-----------. |
| '-+-------' | |
| | ^ | |
| v | v |
| .------------+------. .----------+----.
| | Non-RoT Debug | | Recoverable |
v '---------+---------' | RoT Debug |
.----------------. | '------+--------'
| Decommissioned |<-----------+-------------------'
'----------------'
Figure 1: Lifecycle States.
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aiss-lifecycle-unknown-type = 0
aiss-lifecycle-testing-type = 1
aiss-lifecycle-provisioning-type = 2
aiss-lifecycle-secured-type = 3
aiss-lifecycle-non-rot-debug-type = 4
aiss-lifecycle-recoverable-rot-debug-type = 5
aiss-lifecycle-decommissioned-type = 6
aiss-lifecycle-type =
aiss-lifecycle-unknown-type /
aiss-lifecycle-testing-type /
aiss-lifecycle-provisioning-type /
aiss-lifecycle-secured-type /
aiss-lifecycle-non-rot-debug-type /
aiss-lifecycle-recoverable-rot-debug-type /
aiss-lifecycle-decommissioned-type
aiss-lifecycle = (
aiss-lifecycle-label => aiss-lifecycle-type
)
3.5. Boot Odometer
The Boot Odometer claim contains a value that represents the number
of times the entity or submod has been booted.
The EAT boot-seed-label (claim key TBD) of type unsigned integer is
used.
This claim MUST be present in an AISS attestation token.
aiss-boot-odometer = (
aiss-boot-odometer-label => uint
)
3.6. Watermark
Watermarking, the process of marking an asset with a known structure,
is used to detect intellectual property (IP) theft and overuse.
Watermarking in hardware IPs is the mechanism of embedding a unique
"code" into IP without altering the original functionality of the
design. The ownership of the IP can be later verified when the
watermark is extracted.
The Watermark claim contains a code extracted from the watermarking
hardware identified by an identifier. This identifier is formated as
a type 4 UUID [RFC4122].
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This claim MUST be present in an AISS attestation token when the
attestation token request asked for a watermark to be present.
watermark-type = [
id: bstr .size 16,
watermark: bytes
]
aiss-watermark = ( watermark-label => watermark-type )
3.7. Profile Definition
The Profile Definition claim encodes the unique identifier that
corresponds to the EAT profile described by this document. This
allows a receiver to assign the intended semantics to the rest of the
claims found in the token.
The EAT profile (claim key 265) is used. The following constraints
apply to its type:
* The URI encoding MUST be used.
* The value MUST be http://aiss/1.0.0.
This claim MUST be present in an AISS attestation token.
aiss-profile-type = "http://aiss/1.0.0"
aiss-profile = (
profile-label => aiss-profile-type
)
4. Token Encoding and Signing
The AISS attestation token is encoded in CBOR [RFC8949] format. Only
definite-length string, arrays, and maps are allowed.
Cryptographic protection is accomplished by COSE. The signature
structure MUST be COSE_Sign1. Only the use of asymmetric key
algorithms is envisioned.
The CWT CBOR tag (61) is not used. An application that needs to
exchange PSA attestation tokens can wrap the serialised COSE_Sign1 in
a dedicated media type, as for example defined in defined in
Section 8.2 or the CoAP Content-Format defined in Section 8.3.
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5. Freshness Model
The AISS attestation token supports the freshness models for
attestation Evidence based on nonces (Section 10.2 and 10.3 of
[I-D.ietf-rats-architecture]) using the nonce claim to convey the
nonce supplied by the Verifier. No further assumption on the
specific remote attestation protocol is made.
6. Collated CDDL
aiss-token = {
aiss-nonce,
aiss-instance-id,
aiss-profile,
aiss-implementation-id,
aiss-lifecycle,
aiss-boot-odometer,
aiss-watermark,
}
aiss-lifecycle-label = 2500
aiss-implementation-id-label = 2501
aiss-watermark-label = 2502
aiss-boot-odometer-label = 2503
; from EAT
nonce-label = 10
ueid-label = 256
profile-label = 265
aiss-hash-type = bytes .size 32 / bytes .size 48 / bytes .size 64
aiss-nonce = (
nonce-label => aiss-hash-type
)
aiss-instance-id-type = bytes .size 33
aiss-instance-id = (
ueid-label => aiss-instance-id-type
)
aiss-implementation-id-type = bytes .size 32
aiss-implementation-id = (
aiss-implementation-id-label => aiss-implementation-id-type
)
aiss-lifecycle-unknown-type = 0
aiss-lifecycle-testing-type = 1
aiss-lifecycle-provisioning-type = 2
aiss-lifecycle-secured-type = 3
aiss-lifecycle-non-rot-debug-type = 4
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aiss-lifecycle-recoverable-rot-debug-type = 5
aiss-lifecycle-decommissioned-type = 6
aiss-lifecycle-type =
aiss-lifecycle-unknown-type /
aiss-lifecycle-testing-type /
aiss-lifecycle-provisioning-type /
aiss-lifecycle-secured-type /
aiss-lifecycle-non-rot-debug-type /
aiss-lifecycle-recoverable-rot-debug-type /
aiss-lifecycle-decommissioned-type
aiss-lifecycle = (
aiss-lifecycle-label => aiss-lifecycle-type
)
aiss-boot-odometer = (
aiss-boot-odometer-label => uint
)
watermark-type = [
id: bstr .size 16,
watermark: bytes
]
aiss-watermark = ( watermark-label => watermark-type )
aiss-profile-type = "http://aiss/1.0.0"
aiss-profile = (
profile-label => aiss-profile-type
)
7. Verification
To verify the token, the primary need is to check correct encoding
and signing as detailed in Section 4. In particular, the Instance ID
claim is used (together with the kid in the COSE header, if present)
to assist in locating the public key used to verify the signature
covering the token. The key used for verification is supplied to the
Verifier by an authorized Endorser along with the corresponding
Attester's Instance ID.
In addition, the Verifier will typically operate a policy where
values of some of the claims in this profile can be compared to
reference values, registered with the Verifier for a given
deployment, in order to confirm that the device is endorsed by the
manufacturer supply chain. The policy may require that the relevant
claims must have a match to a registered reference value.
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The protocol used to convey Endorsements and Reference Values to the
Verifier is not in scope for this document.
8. IANA Considerations
8.1. Claim Registration
This specification requests IANA to register the following claims in
the "CBOR Web Token (CWT) Claims" registry [IANA-CWT].
8.1.1. Security Lifecycle Claim
* Claim Name: aiss-security-lifecycle
* Claim Description: AISS Security Lifecycle
* JWT Claim Name: N/A
* Claim Key: TBD (requested value: 2500)
* Claim Value Type(s): unsigned integer
* Change Controller: [[Authors of this RFC]]
* Specification Document(s): Section 3.4 of [[this RFC]]
8.1.2. Implementation ID Claim
* Claim Name: aiss-implementation-id
* Claim Description: AISS Implementation ID
* JWT Claim Name: N/A
* Claim Key: TBD (requested value: 2501)
* Claim Value Type(s): byte string
* Change Controller: [[Authors of this RFC]]
* Specification Document(s): Section 3.3 of [[this RFC]]
8.1.3. Watermark Claim
* Claim Name: aiss-watermark
* Claim Description: AISS Watermark
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* JWT Claim Name: N/A
* Claim Key: TBD (requested value: 2502)
* Claim Value Type(s): byte string
* Change Controller: [[Authors of this RFC]]
* Specification Document(s): Section 3.6 of [[this RFC]]
8.2. Media Type Registration
IANA is requested to register the "application/aiss-attestation-
token" media type [RFC2046] in the "Media Types" registry
[IANA-MediaTypes] in the manner described in RFC 6838 [RFC6838],
which can be used to indicate that the content is an AISS Attestation
Token.
* Type name: application
* Subtype name: aiss-attestation-token
* Required parameters: n/a
* Optional parameters: n/a
* Encoding considerations: binary
* Security considerations: See the Security Considerations section
of [[this RFC]]
* Interoperability considerations: n/a
* Published specification: [[this RFC]]
* Applications that use this media type: Attesters and Relying
Parties sending AISS attestation tokens over HTTP(S), CoAP(S) and
other transports.
* Fragment identifier considerations: n/a
* Additional information:
- Magic number(s): n/a
- File extension(s): n/a
- Macintosh file type code(s): n/a
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* Person & email address to contact for further information: Hannes
Tschofenig, Hannes.Tschofenig@arm.com
* Intended usage: COMMON
* Restrictions on usage: none
* Author: Hannes Tschofenig, Hannes.Tschofenig@arm.com
* Change controller: IESG
* Provisional registration? No
8.3. CoAP Content-Formats Registration
IANA is requested to register the CoAP Content-Format ID for the
"application/aiss-attestation-token" media type in the "CoAP Content-
Formats" registry [IANA-CoAP-Content-Formats].
8.3.1. Registry Contents
* Media Type: application/aiss-attestation-token
* Encoding: -
* Id: [[To-be-assigned by IANA]]
* Reference: [[this RFC]]
9. References
9.1. Normative References
[I-D.ietf-rats-eat]
Lundblade, L., Mandyam, G., and J. O'Donoghue, "The Entity
Attestation Token (EAT)", Work in Progress, Internet-
Draft, draft-ietf-rats-eat-12, 24 February 2022,
<https://www.ietf.org/archive/id/draft-ietf-rats-eat-
12.txt>.
[IANA-CWT] IANA, "CBOR Web Token (CWT) Claims", 2022,
<https://www.iana.org/assignments/cwt/cwt.xhtml#claims-
registry>.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
DOI 10.17487/RFC2046, November 1996,
<https://www.rfc-editor.org/info/rfc2046>.
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[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>.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/info/rfc6838>.
[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>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/info/rfc8610>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/info/rfc8949>.
9.2. Informative References
[I-D.ietf-rats-architecture]
Birkholz, H., Thaler, D., Richardson, M., Smith, N., and
W. Pan, "Remote Attestation Procedures Architecture", Work
in Progress, Internet-Draft, draft-ietf-rats-architecture-
15, 8 February 2022, <https://www.ietf.org/archive/id/
draft-ietf-rats-architecture-15.txt>.
[IANA-CoAP-Content-Formats]
IANA, "CoAP Content-Formats", 2022,
<https://www.iana.org/assignments/core-parameters>.
[IANA-MediaTypes]
IANA, "Media Types", 2022,
<http://www.iana.org/assignments/media-types>.
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Appendix A. Example
The following example shows an AISS attestation token for an
hypothetical system. The attesting device is in a lifecycle state
Section 3.4 of SECURED.
The claims in this example are:
{
/ instance-id / 255: h'FF0039A1',
/ nonce / 10: h'AABBCCDD',
/ lifecycle / 2500: 2,
/ implementation-id / 2501: h'CCDDEE',
/ watermark / 2502: h'010203',
/ boot-odometer / 2503: 5,
/ profile-id / 256: "aiss/1.0.0",
}
The resulting COSE object is:
18(
[
/ protected / h'A10126',
/ unprotected / {},
/ payload / h'A718FF44FF0039A10A44AABBCCDD1909C4021901006
A616973732F312E302E301909C543CCDDEE1909C643
0102031909C705',
/ signature / h'9744085E05D875E5EAAEC1598D1DD9E14097CCE4E9A
484344D08C9D41244713C700CD4F1CD7E86C0C6397A
ABECE40E166EBA5AA92DB11170F69B2DD8E681708E'
]
)
Acknowledgments
We would like to thank Rob Aitken, Mike Borza, Liam Dillon, Dale
Donchin, John Goodenough, and Oleg Raikhman for their feedback.
Work on this document has in part been supported by the DARPA AISS
project (grant agreement HR0011-20-9-0043).
Authors' Addresses
Hannes Tschofenig
Arm Limited
Email: Hannes.Tschofenig@arm.com
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Arto Kankaanpää
Synopsys
Email: arto.kankaanpaa@synopsys.com
Nick Bowler
Synopsys
Email: nick.bowler@synopsys.com
Tushar Khandelwal
Arm Limited
Email: Tushar.Khandelwal@arm.com
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