draft-ietf-rats-reference-interaction-models-02.txt   draft-ietf-rats-reference-interaction-models-03.txt 
RATS Working Group H. Birkholz RATS Working Group H. Birkholz
Internet-Draft M. Eckel Internet-Draft M. Eckel
Intended status: Informational Fraunhofer SIT Intended status: Informational Fraunhofer SIT
Expires: 28 October 2021 W. Pan Expires: 14 January 2022 W. Pan
Huawei Technologies Huawei Technologies
E. Voit E. Voit
Cisco Cisco
26 April 2021 13 July 2021
Reference Interaction Models for Remote Attestation Procedures Reference Interaction Models for Remote Attestation Procedures
draft-ietf-rats-reference-interaction-models-02 draft-ietf-rats-reference-interaction-models-03
Abstract Abstract
This document describes interaction models for remote attestation This document describes interaction models for remote attestation
procedures (RATS). Three conveying mechanisms -- Challenge/Response, procedures (RATS). Three conveying mechanisms -- Challenge/Response,
Uni-Directional, and Streaming Remote Attestation -- are illustrated Uni-Directional, and Streaming Remote Attestation -- are illustrated
and defined. Analogously, a general overview about the information and defined. Analogously, a general overview about the information
elements typically used by corresponding conveyance protocols are elements typically used by corresponding conveyance protocols are
highlighted. highlighted.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on 28 October 2021. This Internet-Draft will expire on 14 January 2022.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/ Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document. license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
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Attester itself. The corresponding trustable statements are called Attester itself. The corresponding trustable statements are called
Endorsements and originate from external, trustable entities that Endorsements and originate from external, trustable entities that
take on the role of an Endorser (e.g., supply chain entities). take on the role of an Endorser (e.g., supply chain entities).
5. Normative Prerequisites 5. Normative Prerequisites
In order to ensure an appropriate conveyance of Evidence via In order to ensure an appropriate conveyance of Evidence via
interaction models in general, the following set of prerequisites interaction models in general, the following set of prerequisites
MUST be in place to support the implementation of interaction models: MUST be in place to support the implementation of interaction models:
Authentication Secret: An Authentication Secret MUST be available
exclusively to an Attesting Environment of an Attester.
The Attester MUST protect Claims with that Authentication Secret,
thereby proving the authenticity of the Claims included in
Evidence. The Authentication Secret MUST be established before
RATS can take place.
Attester Identity: A statement about a distinguishable Attester made Attester Identity: A statement about a distinguishable Attester made
by an Endorser without accompanying evidence about its validity, by an Endorser.
used as proof of identity.
The provenance of Evidence with respect to a distinguishable The provenance of Evidence with respect to a distinguishable
Attesting Environment MUST be correct and unambiguous. Attesting Environment MUST be correct and unambiguous.
An Attester Identity MAY be a unique identity, MAY be included in An Attester Identity MAY be an Authentication Secret which is
a zero-knowledge proof (ZKP), MAY be part of a group signature, or available exclusively to one of the Attesting Environments of an
it MAY be a randomized DAA credential [DAA]. Attester. It MAY be a unique identity, MAY be included in a zero-
knowledge proof (ZKP), MAY be part of a group signature, or it MAY
be a randomized DAA credential [DAA].
Attestation Evidence Authenticity: Attestation Evidence MUST be Attestation Evidence Authenticity: Attestation Evidence MUST be
authentic. authentic.
In order to provide proofs of authenticity, Attestation Evidence In order to provide proofs of authenticity, Attestation Evidence
SHOULD be cryptographically associated with an identity document SHOULD be cryptographically associated with an identity document
(e.g. an PKIX certificate or trusted key material, or a randomized (e.g., a PKIX certificate or trusted key material, or a randomized
DAA credential [DAA]), or SHOULD include a correct and unambiguous DAA credential [DAA]), or SHOULD include a correct, unambiguous
and stable reference to an accessible identity document. and stable reference to an accessible identity document.
Authentication Secret: An Authentication Secret MUST be available
exclusively to an Attester's Attesting Environment.
The Attester MUST protect Claims with that Authentication Secret,
thereby proving the authenticity of the Claims included in
Evidence. The Authentication Secret MUST be established before
RATS can take place.
Evidence Freshness: Evidence MUST include an indicator about its Evidence Freshness: Evidence MUST include an indicator about its
freshness that can be understood by a Verifier. Analogously, freshness that can be understood by a Verifier. Analogously,
interaction models MUST support the conveyance of proofs of interaction models MUST support the conveyance of proofs of
freshness in a way that is useful to Verifiers and their appraisal freshness in a way that is useful to Verifiers and their appraisal
procedures. procedures.
Evidence Protection: Evidence MUST be a set of well-formatted and Evidence Protection: Evidence MUST be a set of well-formatted and
well-protected Claims that an Attester can create and convey to a well-protected Claims that an Attester can create and convey to a
Verifier in a tamper-evident manner. Verifier in a tamper-evident manner.
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This section defines the information elements that are vital to all This section defines the information elements that are vital to all
kinds interaction models. Varying from solution to solution, generic kinds interaction models. Varying from solution to solution, generic
information elements can be either included in the scope of protocol information elements can be either included in the scope of protocol
messages (instantiating Conceptual Messages) or can be included in messages (instantiating Conceptual Messages) or can be included in
additional protocol parameters or payload. Ultimately, the following additional protocol parameters or payload. Ultimately, the following
information elements are required by any kind of scalable remote information elements are required by any kind of scalable remote
attestation procedure using one or more of the interaction models attestation procedure using one or more of the interaction models
provided. provided.
Attester Identity ('attesterIdentity'): _mandatory_
A statement about a distinguishable Attester made by an Endorser
without accompanying evidence about its validity - used as proof
of identity.
Authentication Secret IDs ('authSecIDs'): _mandatory_ Authentication Secret IDs ('authSecIDs'): _mandatory_
A statement representing an identifier list that MUST be A statement representing an identifier list that MUST be
associated with corresponding Authentication Secrets used to associated with corresponding Authentication Secrets used to
protect Claims included in Evidence. protect Claims included in Evidence.
Each Authentication Secret is uniquely associated with a Each Authentication Secret is uniquely associated with a
distinguishable Attesting Environment. Consequently, an distinguishable Attesting Environment. Consequently, an
Authentication Secret ID also identifies an Attesting Environment. Authentication Secret ID also identifies an Attesting Environment.
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With the Handle, the Authentication Secret IDs, and the collected With the Handle, the Authentication Secret IDs, and the collected
Claims, the Attester produces signed Evidence. That is, it digitally Claims, the Attester produces signed Evidence. That is, it digitally
signs the Handle and the collected Claims with a cryptographic secret signs the Handle and the collected Claims with a cryptographic secret
identified by the Authentication Secret ID. This is done once per identified by the Authentication Secret ID. This is done once per
Attesting Environment which is identified by the particular Attesting Environment which is identified by the particular
Authentication Secret ID. The Attester communicates the signed Authentication Secret ID. The Attester communicates the signed
Evidence as well as all accompanying Event Logs back to the Verifier. Evidence as well as all accompanying Event Logs back to the Verifier.
While it is crucial that Claims, the Handle, and the Attester While it is crucial that Claims, the Handle, and the Attester
Identity information MUST be cryptographically bound to the signature Identity information (i.e., the Authentication Secret) MUST be
of Evidence, they MAY be presented obfuscated, encrypted, or cryptographically bound to the signature of Evidence, they MAY be
cryptographically blinded. For further reference see section presented obfuscated, encrypted, or cryptographically blinded. For
Section 10. further reference see section Section 10.
As soon as the Verifier receives the signed Evidence and Event Logs, As soon as the Verifier receives the Evidence and the Event Logs, it
it appraises the Evidence. For this purpose, it validates the appraises the Evidence. For this purpose, it validates the
signature, the Attester Identity, and the Handle, and then appraises signature, the Attester Identity, and the Handle, and then appraises
the Claims. Appraisal procedures are application-specific and can be the Claims. Appraisal procedures are application-specific and can be
conducted via comparison of the Claims with corresponding Reference conducted via comparison of the Claims with corresponding Reference
Values, such as Reference Integrity Measurements. The final output Values, such as Reference Integrity Measurements. The final output
of the Verifier are Attestation Results. Attestation Results of the Verifier are Attestation Results. Attestation Results
constitute new Claim Sets about the properties and characteristics of constitute new Claim Sets about the properties and characteristics of
an Attester, which enables Relying Parties, for example, to assess an an Attester, which enables Relying Parties, for example, to assess an
Attester's trustworthiness. Attester's trustworthiness.
7.2. Uni-Directional Remote Attestation 7.2. Uni-Directional Remote Attestation
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12.2. Informative References 12.2. Informative References
[DAA] Brickell, E., Camenisch, J., and L. Chen, "Direct [DAA] Brickell, E., Camenisch, J., and L. Chen, "Direct
Anonymous Attestation", page 132-145, ACM Proceedings of Anonymous Attestation", page 132-145, ACM Proceedings of
the 11rd ACM conference on Computer and Communications the 11rd ACM conference on Computer and Communications
Security, 2004. Security, 2004.
[I-D.birkholz-rats-tuda] [I-D.birkholz-rats-tuda]
Fuchs, A., Birkholz, H., McDonald, I. E., and C. Bormann, Fuchs, A., Birkholz, H., McDonald, I. E., and C. Bormann,
"Time-Based Uni-Directional Attestation", Work in "Time-Based Uni-Directional Attestation", Work in
Progress, Internet-Draft, draft-birkholz-rats-tuda-04, 13 Progress, Internet-Draft, draft-birkholz-rats-tuda-05, 12
January 2021, <https://www.ietf.org/archive/id/draft- July 2021, <https://www.ietf.org/archive/id/draft-
birkholz-rats-tuda-04.txt>. birkholz-rats-tuda-05.txt>.
[I-D.ietf-rats-architecture] [I-D.ietf-rats-architecture]
Birkholz, H., Thaler, D., Richardson, M., Smith, N., and Birkholz, H., Thaler, D., Richardson, M., Smith, N., and
W. Pan, "Remote Attestation Procedures Architecture", Work W. Pan, "Remote Attestation Procedures Architecture", Work
in Progress, Internet-Draft, draft-ietf-rats-architecture- in Progress, Internet-Draft, draft-ietf-rats-architecture-
12, 23 April 2021, <https://www.ietf.org/archive/id/draft- 12, 23 April 2021, <https://www.ietf.org/archive/id/draft-
ietf-rats-architecture-12.txt>. ietf-rats-architecture-12.txt>.
[I-D.ietf-rats-tpm-based-network-device-attest] [I-D.ietf-rats-tpm-based-network-device-attest]
Fedorkow, G., Voit, E., and J. Fitzgerald-McKay, "TPM- Fedorkow, G., Voit, E., and J. Fitzgerald-McKay, "TPM-
based Network Device Remote Integrity Verification", Work based Network Device Remote Integrity Verification", Work
in Progress, Internet-Draft, draft-ietf-rats-tpm-based- in Progress, Internet-Draft, draft-ietf-rats-tpm-based-
network-device-attest-06, 7 December 2020, network-device-attest-07, 10 June 2021,
<https://www.ietf.org/archive/id/draft-ietf-rats-tpm- <https://www.ietf.org/archive/id/draft-ietf-rats-tpm-
based-network-device-attest-06.txt>. based-network-device-attest-07.txt>.
[turtles] Rudnicki, R., "Turtles All the Way Down: Foundation, [turtles] Rudnicki, R., "Turtles All the Way Down: Foundation,
Edifice, and Ruin in Faulkner and McCarthy", Edifice, and Ruin in Faulkner and McCarthy",
DOI 10.1353/fau.2010.0002, The Faulkner Journal 25.2, DOI 10.1353/fau.2010.0002, The Faulkner Journal 25.2,
2010, <https://doi.org/10.1353/fau.2010.0002>. 2010, <https://doi.org/10.1353/fau.2010.0002>.
Appendix A. CDDL Specification for a simple CoAP Challenge/Response Appendix A. CDDL Specification for a simple CoAP Challenge/Response
Interaction Interaction
The following CDDL specification is an exemplary proof-of-concept to The following CDDL specification is an exemplary proof-of-concept to
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