--- 1/draft-ietf-rats-eat-06.txt 2021-02-03 15:13:11.410461008 -0800 +++ 2/draft-ietf-rats-eat-07.txt 2021-02-03 15:13:11.506463447 -0800 @@ -1,22 +1,22 @@ RATS Working Group G. Mandyam Internet-Draft Qualcomm Technologies Inc. Intended status: Standards Track L. Lundblade -Expires: 4 June 2021 Security Theory LLC +Expires: August 7, 2021 Security Theory LLC M. Ballesteros J. O'Donoghue Qualcomm Technologies Inc. - 1 December 2020 + February 03, 2021 The Entity Attestation Token (EAT) - draft-ietf-rats-eat-06 + draft-ietf-rats-eat-07 Abstract An Entity Attestation Token (EAT) provides a signed (attested) set of claims that describe state and characteristics of an entity, typically a device like a phone or an IoT device. These claims are used by a relying party to determine how much it wishes to trust the entity. An EAT is either a CWT or JWT with some attestation-oriented claims. @@ -34,132 +34,151 @@ Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." - This Internet-Draft will expire on 4 June 2021. + This Internet-Draft will expire on August 7, 2021. Copyright Notice - Copyright (c) 2020 IETF Trust and the persons identified as the + Copyright (c) 2021 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 of publication of this document. - Please review these documents carefully, as they describe your rights - and restrictions with respect to this document. Code Components - extracted from this document must include Simplified BSD License text - as described in Section 4.e of the Trust Legal Provisions and are - provided without warranty as described in the Simplified BSD License. + Provisions Relating to IETF Documents + (https://trustee.ietf.org/license-info) in effect on the date of + publication of this document. Please review these documents + carefully, as they describe your rights and restrictions with respect + to this document. Code Components extracted from this document must + include Simplified BSD License text as described in Section 4.e of + the Trust Legal Provisions and are provided without warranty as + described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. CWT, JWT and UCCS . . . . . . . . . . . . . . . . . . . . 5 1.2. CDDL . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 1.3. Entity Overview . . . . . . . . . . . . . . . . . . . . . 5 + 1.3. Entity Overview . . . . . . . . . . . . . . . . . . . . . 6 1.4. EAT Operating Models . . . . . . . . . . . . . . . . . . 6 1.5. What is Not Standardized . . . . . . . . . . . . . . . . 7 - 1.5.1. Transmission Protocol . . . . . . . . . . . . . . . . 7 + 1.5.1. Transmission Protocol . . . . . . . . . . . . . . . . 8 1.5.2. Signing Scheme . . . . . . . . . . . . . . . . . . . 8 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 8 3. The Claims . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1. Token ID Claim (cti and jti) . . . . . . . . . . . . . . 10 3.2. Timestamp claim (iat) . . . . . . . . . . . . . . . . . . 10 3.3. Nonce Claim (nonce) . . . . . . . . . . . . . . . . . . . 10 3.3.1. nonce CDDL . . . . . . . . . . . . . . . . . . . . . 11 3.4. Universal Entity ID Claim (ueid) . . . . . . . . . . . . 11 3.4.1. ueid CDDL . . . . . . . . . . . . . . . . . . . . . . 13 3.5. Origination Claim (origination) . . . . . . . . . . . . . 13 3.5.1. origination CDDL . . . . . . . . . . . . . . . . . . 14 3.6. OEM Identification by IEEE (oemid) . . . . . . . . . . . 14 - 3.6.1. oemid CDDL . . . . . . . . . . . . . . . . . . . . . 15 - 3.7. Hardware Version Claims (hardware-version-claims) . . . . 15 + 3.6.1. oemid CDDL . . . . . . . . . . . . . . . . . . . . . 14 + 3.7. Hardware Version Claims (hardware-version-claims) . . . . 14 3.8. Software Description and Version . . . . . . . . . . . . 16 - 3.9. The Security Level Claim (security-level) . . . . . . . . 17 - 3.9.1. security-level CDDL . . . . . . . . . . . . . . . . . 18 - 3.10. Secure Boot Claim (secure-boot) . . . . . . . . . . . . . 18 - 3.10.1. secure-boot CDDL . . . . . . . . . . . . . . . . . . 18 + 3.9. The Security Level Claim (security-level) . . . . . . . . 16 + 3.9.1. security-level CDDL . . . . . . . . . . . . . . . . . 17 + 3.10. Secure Boot Claim (secure-boot) . . . . . . . . . . . . . 17 + 3.10.1. secure-boot CDDL . . . . . . . . . . . . . . . . . . 17 3.11. Debug Status Claim (debug-status) . . . . . . . . . . . . 18 3.11.1. Enabled . . . . . . . . . . . . . . . . . . . . . . 19 3.11.2. Disabled . . . . . . . . . . . . . . . . . . . . . . 19 - 3.11.3. Disabled Since Boot . . . . . . . . . . . . . . . . 20 - 3.11.4. Disabled Permanently . . . . . . . . . . . . . . . . 20 - 3.11.5. Disabled Fully and Permanently . . . . . . . . . . . 20 - 3.11.6. debug-status CDDL . . . . . . . . . . . . . . . . . 20 + 3.11.3. Disabled Since Boot . . . . . . . . . . . . . . . . 19 + 3.11.4. Disabled Permanently . . . . . . . . . . . . . . . . 19 + 3.11.5. Disabled Fully and Permanently . . . . . . . . . . . 19 + 3.11.6. debug-status CDDL . . . . . . . . . . . . . . . . . 19 3.12. Including Keys . . . . . . . . . . . . . . . . . . . . . 20 3.13. The Location Claim (location) . . . . . . . . . . . . . . 21 - 3.13.1. location CDDL . . . . . . . . . . . . . . . . . . . 22 + 3.13.1. location CDDL . . . . . . . . . . . . . . . . . . . 21 3.14. The Uptime Claim (uptime) . . . . . . . . . . . . . . . . 22 3.14.1. uptime CDDL . . . . . . . . . . . . . . . . . . . . 22 + 3.14.2. The Boot Seed Claim (boot-seed) . . . . . . . . . . 22 3.15. The Intended Use Claim (intended-use) . . . . . . . . . . 23 3.15.1. intended-use CDDL . . . . . . . . . . . . . . . . . 23 - 3.16. The Submodules Part of a Token (submods) . . . . . . . . 24 - 3.16.1. Two Types of Submodules . . . . . . . . . . . . . . 24 - 3.16.1.1. Non-token Submodules . . . . . . . . . . . . . . 24 - 3.16.1.2. Nested EATs . . . . . . . . . . . . . . . . . . 25 - 3.16.1.3. Unsecured JWTs and UCCS Tokens as Submodules . . 26 - 3.16.2. No Inheritance . . . . . . . . . . . . . . . . . . . 26 - 3.16.3. Security Levels . . . . . . . . . . . . . . . . . . 27 - 3.16.4. Submodule Names . . . . . . . . . . . . . . . . . . 27 - 3.16.5. submods CDDL . . . . . . . . . . . . . . . . . . . . 27 + 3.16. The Profile Claim (profile) . . . . . . . . . . . . . . . 24 + 3.17. The Submodules Part of a Token (submods) . . . . . . . . 24 + 3.17.1. Two Types of Submodules . . . . . . . . . . . . . . 25 + 3.17.1.1. Non-token Submodules . . . . . . . . . . . . . . 25 + 3.17.1.2. Nested EATs . . . . . . . . . . . . . . . . . . 25 + 3.17.1.3. Unsecured JWTs and UCCS Tokens as Submodules . . 26 + 3.17.2. No Inheritance . . . . . . . . . . . . . . . . . . . 27 + 3.17.3. Security Levels . . . . . . . . . . . . . . . . . . 27 + 3.17.4. Submodule Names . . . . . . . . . . . . . . . . . . 27 + 3.17.5. submods CDDL . . . . . . . . . . . . . . . . . . . . 27 4. Endorsements and Verification Keys . . . . . . . . . . . . . 28 - 5. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 28 - 5.1. Common CDDL Types . . . . . . . . . . . . . . . . . . . . 29 - 5.2. CDDL for CWT-defined Claims . . . . . . . . . . . . . . . 29 - 5.3. JSON . . . . . . . . . . . . . . . . . . . . . . . . . . 29 - 5.3.1. JSON Labels . . . . . . . . . . . . . . . . . . . . . 29 - 5.3.2. JSON Interoperability . . . . . . . . . . . . . . . . 30 - 5.4. CBOR . . . . . . . . . . . . . . . . . . . . . . . . . . 30 - 5.4.1. CBOR Interoperability . . . . . . . . . . . . . . . . 30 - 5.5. Collected CDDL . . . . . . . . . . . . . . . . . . . . . 32 - 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38 - 6.1. Reuse of CBOR Web Token (CWT) Claims Registry . . . . . . 38 - 6.2. Claim Characteristics . . . . . . . . . . . . . . . . . . 38 - 6.2.1. Interoperability and Relying Party Orientation . . . 38 - 6.2.2. Operating System and Technology Neutral . . . . . . . 39 - 6.2.3. Security Level Neutral . . . . . . . . . . . . . . . 39 - 6.2.4. Reuse of Extant Data Formats . . . . . . . . . . . . 39 - 6.2.5. Proprietary Claims . . . . . . . . . . . . . . . . . 40 - 6.3. Claims Registered by This Document . . . . . . . . . . . 40 - 7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 40 - 7.1. UEID Privacy Considerations . . . . . . . . . . . . . . . 41 - 7.2. Location Privacy Considerations . . . . . . . . . . . . . 41 - 8. Security Considerations . . . . . . . . . . . . . . . . . . . 42 - 8.1. Key Provisioning . . . . . . . . . . . . . . . . . . . . 42 - 8.1.1. Transmission of Key Material . . . . . . . . . . . . 42 - 8.2. Transport Security . . . . . . . . . . . . . . . . . . . 42 - 8.3. Multiple EAT Consumers . . . . . . . . . . . . . . . . . 43 - 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 43 - 9.1. Normative References . . . . . . . . . . . . . . . . . . 43 - 9.2. Informative References . . . . . . . . . . . . . . . . . 45 - Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 47 - A.1. Very Simple EAT . . . . . . . . . . . . . . . . . . . . . 47 - A.2. Example with Submodules, Nesting and Security Levels . . 47 - Appendix B. UEID Design Rationale . . . . . . . . . . . . . . . 48 - B.1. Collision Probability . . . . . . . . . . . . . . . . . . 48 - B.2. No Use of UUID . . . . . . . . . . . . . . . . . . . . . 51 - Appendix C. Changes from Previous Drafts . . . . . . . . . . . . 51 - C.1. From draft-rats-eat-01 . . . . . . . . . . . . . . . . . 51 - C.2. From draft-mandyam-rats-eat-00 . . . . . . . . . . . . . 52 - C.3. From draft-ietf-rats-eat-01 . . . . . . . . . . . . . . . 52 - C.4. From draft-ietf-rats-eat-02 . . . . . . . . . . . . . . . 52 - C.5. From draft-ietf-rats-eat-03 . . . . . . . . . . . . . . . 52 - C.6. From draft-ietf-rats-eat-04 . . . . . . . . . . . . . . . 52 - C.7. From draft-ietf-rats-eat-05 . . . . . . . . . . . . . . . 53 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 53 + 5. Profiles . . . . . . . . . . . . . . . . . . . . . . . . . . 28 + 5.1. List of Profile Issues . . . . . . . . . . . . . . . . . 29 + 5.1.1. Use of JSON, CBOR or both . . . . . . . . . . . . . . 29 + 5.1.2. CBOR Map and Array Encoding . . . . . . . . . . . . . 29 + 5.1.3. CBOR String Encoding . . . . . . . . . . . . . . . . 29 + 5.1.4. COSE/JOSE Protection . . . . . . . . . . . . . . . . 29 + 5.1.5. COSE/JOSE Algorithms . . . . . . . . . . . . . . . . 30 + 5.1.6. Verification Key Identification . . . . . . . . . . . 30 + 5.1.7. Endorsement Identification . . . . . . . . . . . . . 30 + 5.1.8. Required Claims . . . . . . . . . . . . . . . . . . . 30 + 5.1.9. Prohibited Claims . . . . . . . . . . . . . . . . . . 30 + 5.1.10. Additional Claims . . . . . . . . . . . . . . . . . . 31 + 5.1.11. Refined Claim Definition . . . . . . . . . . . . . . 31 + 5.1.12. CBOR Tags . . . . . . . . . . . . . . . . . . . . . . 31 + 6. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 31 + 6.1. Common CDDL Types . . . . . . . . . . . . . . . . . . . . 31 + 6.2. CDDL for CWT-defined Claims . . . . . . . . . . . . . . . 31 + 6.3. JSON . . . . . . . . . . . . . . . . . . . . . . . . . . 32 + 6.3.1. JSON Labels . . . . . . . . . . . . . . . . . . . . . 32 + 6.3.2. JSON Interoperability . . . . . . . . . . . . . . . . 33 + 6.4. CBOR . . . . . . . . . . . . . . . . . . . . . . . . . . 33 + 6.4.1. CBOR Interoperability . . . . . . . . . . . . . . . . 33 + 6.4.1.1. EAT Constrained Device Serialization . . . . . . 33 + 6.5. Collected CDDL . . . . . . . . . . . . . . . . . . . . . 34 + 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40 + 7.1. Reuse of CBOR Web Token (CWT) Claims Registry . . . . . . 40 + 7.2. Claim Characteristics . . . . . . . . . . . . . . . . . . 40 + 7.2.1. Interoperability and Relying Party Orientation . . . 40 + 7.2.2. Operating System and Technology Neutral . . . . . . . 41 + 7.2.3. Security Level Neutral . . . . . . . . . . . . . . . 41 + 7.2.4. Reuse of Extant Data Formats . . . . . . . . . . . . 41 + 7.2.5. Proprietary Claims . . . . . . . . . . . . . . . . . 42 + 7.3. Claims Registered by This Document . . . . . . . . . . . 42 + 8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 42 + 8.1. UEID Privacy Considerations . . . . . . . . . . . . . . . 43 + 8.2. Location Privacy Considerations . . . . . . . . . . . . . 43 + 9. Security Considerations . . . . . . . . . . . . . . . . . . . 44 + 9.1. Key Provisioning . . . . . . . . . . . . . . . . . . . . 44 + 9.1.1. Transmission of Key Material . . . . . . . . . . . . 44 + 9.2. Transport Security . . . . . . . . . . . . . . . . . . . 44 + 9.3. Multiple EAT Consumers . . . . . . . . . . . . . . . . . 45 + 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 45 + 10.1. Normative References . . . . . . . . . . . . . . . . . . 45 + 10.2. Informative References . . . . . . . . . . . . . . . . . 47 + Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 49 + A.1. Very Simple EAT . . . . . . . . . . . . . . . . . . . . . 49 + A.2. Example with Submodules, Nesting and Security Levels . . 49 + Appendix B. UEID Design Rationale . . . . . . . . . . . . . . . 50 + B.1. Collision Probability . . . . . . . . . . . . . . . . . . 50 + B.2. No Use of UUID . . . . . . . . . . . . . . . . . . . . . 52 + Appendix C. Changes from Previous Drafts . . . . . . . . . . . . 53 + C.1. From draft-rats-eat-01 . . . . . . . . . . . . . . . . . 53 + C.2. From draft-mandyam-rats-eat-00 . . . . . . . . . . . . . 53 + C.3. From draft-ietf-rats-eat-01 . . . . . . . . . . . . . . . 53 + C.4. From draft-ietf-rats-eat-02 . . . . . . . . . . . . . . . 53 + C.5. From draft-ietf-rats-eat-03 . . . . . . . . . . . . . . . 54 + C.6. From draft-ietf-rats-eat-04 . . . . . . . . . . . . . . . 54 + C.7. From draft-ietf-rats-05 . . . . . . . . . . . . . . . . . 54 + C.8. From draft-ietf-rats-06 . . . . . . . . . . . . . . . . . 55 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 55 1. Introduction Remote device attestation is a fundamental service that allows a remote device such as a mobile phone, an Internet-of-Things (IoT) device, or other endpoint to prove itself to a relying party, a server or a service. This allows the relying party to know some characteristics about the device and decide whether it trusts the device. @@ -170,57 +189,58 @@ The relying party needs to know that the device is one that is known to do biometric matching correctly. Another example is content protection where the relying party wants to know the device will protect the data. This generalizes on to corporate enterprises that might want to know that a device is trustworthy before allowing corporate data to be accessed by it. The notion of attestation here is large and may include, but is not limited to the following: - * Proof of the make and model of the device hardware (HW) + o Proof of the make and model of the device hardware (HW) - * Proof of the make and model of the device processor, particularly + o Proof of the make and model of the device processor, particularly for security-oriented chips - * Measurement of the software (SW) running on the device + o Measurement of the software (SW) running on the device - * Configuration and state of the device - * Environmental characteristics of the device such as its GPS + o Configuration and state of the device + + o Environmental characteristics of the device such as its GPS location TODO: mention use for Attestation Evidence and Results. 1.1. CWT, JWT and UCCS For flexibility and ease of imlpementation in a wide variety of - environments, EATs can be either CBOR [RFC7049] or JSON [ECMAScript] + environments, EATs can be either CBOR [RFC8949] or JSON [ECMAScript] format. This specification simultaneously describes both formats. An EAT is either a CWT as defined in [RFC8392], a UCCS as defined in [UCCS.Draft], or a JWT as defined in [RFC7519]. This specification extends those specifications with additional claims for attestation. The identification of a protocol element as an EAT, whether CBOR or JSON format, follows the general conventions used by CWT, JWT and UCCS. Largely this depends on the protocol carrying the EAT. In some cases it may be by content type (e.g., MIME type). In other cases it may be through use of CBOR tags. There is no fixed mechanism across all use cases. 1.2. CDDL This specification uses CDDL, [RFC8610], as the primary formalism to define each claim. The implementor then interprets the CDDL to come - to either the CBOR [RFC7049] or JSON [ECMAScript] representation. In + to either the CBOR [RFC8949] or JSON [ECMAScript] representation. In the case of JSON, Appendix E of [RFC8610] is followed. Additional - rules are given in Section 5.3.2 of this document where Appendix E is + rules are given in Section 6.3.2 of this document where Appendix E is insufficient. (Note that this is not to define a general means to translate between CBOR and JSON, but only to define enough such that the claims defined in this document can be rendered unambiguously in JSON). The CWT specification was authored before CDDL was available and did not use it. This specification includes a CDDL definition of most of what is described in [RFC8392]. 1.3. Entity Overview @@ -273,29 +293,29 @@ In all operating models, hardware and/or software on the entity create an EAT of the format described in this document. The EAT is always signed by the attestation key material provisioned by the manufacturer. In all operating models, the relying party must end up knowing that the signature on the EAT is valid and consistent with data from claims in the EAT. This can happen in many different ways. Here are some examples. - * The EAT is transmitted to the relying party. The relying party + o The EAT is transmitted to the relying party. The relying party gets corresponding key material (e.g. a root certificate) from the manufacturer. The relying party performs the verification. - * The EAT is transmitted to the relying party. The relying party + o The EAT is transmitted to the relying party. The relying party transmits the EAT to a verification service offered by the manufacturer. The server returns the validated claims. - * The EAT is transmitted directly to a verification service, perhaps + o The EAT is transmitted directly to a verification service, perhaps operated by the manufacturer or perhaps by another party. It verifies the EAT and makes the validated claims available to the relying party. It may even modify the claims in some way and re- sign the EAT (with a different signing key). All these operating models are supported and there is no preference of one over the other. It is important to support this variety of operating models to generally facilitate deployment and to allow for some special scenarios. One special scenario has a validation service that is monetized, most likely by the manufacturer. In @@ -385,37 +405,37 @@ 3. The Claims This section describes new claims defined for attestation. It also mentions several claims defined by CWT and JWT that are particularly important for EAT. Note also: * Any claim defined for CWT or JWT may be used in an EAT including those in the CWT [IANA.CWT.Claims] and JWT IANA [IANA.JWT.Claims] claims registries. - * All claims are optional + o All claims are optional - * No claims are mandatory + o No claims are mandatory - * All claims that are not understood by implementations MUST be + o All claims that are not understood by implementations MUST be ignored There are no default values or meanings assigned to absent claims other than they are not reported. The reason for a claim's absence may be the implementation not supporting the claim, an inability to determine its value, or a preference to report in a different way such as a proprietary claim. CDDL along with text descriptions is used to define each claim indepdent of encoding. Each claim is defined as a CDDL group (the group is a general aggregation and type definition feature of CDDL). - In the encoding section Section 5, the CDDL groups turn into CBOR map + In the encoding section Section 6, the CDDL groups turn into CBOR map entries and JSON name/value pairs. TODO: add paragraph here about use for Attestation Evidence and for Results. 3.1. Token ID Claim (cti and jti) CWT defines the "cti" claim. JWT defines the "jti" claim. These are equivalent to each other in EAT and carry a unique token identifier as they do in JWT and CWT. They may be used to defend against re use @@ -483,93 +503,88 @@ UEID's must be universally and globally unique across manufacturers and countries. UEIDs must also be unique across protocols and systems, as tokens are intended to be embedded in many different protocols and systems. No two products anywhere, even in completely different industries made by two different manufacturers in two different countries should have the same UEID (if they are not global and universal in this way, then relying parties receiving them will have to track other characteristics of the device to keep devices distinct between manufacturers). - There are privacy considerations for UEID's. See Section 7.1. + There are privacy considerations for UEID's. See Section 8.1. The UEID should be permanent. It should never change for a given device / entity. In addition, it should not be reprogrammable. UEID's are variable length. All implementations MUST be able to receive UEID's that are 33 bytes long (1 type byte and 256 bits). The recommended maximum sent is also 33 bytes. When the entity constructs the UEID, the first byte is a type and the following bytes the ID for that type. Several types are allowed to accommodate different industries and different manufacturing processes and to give options to avoid paying fees for certain types of manufacturer registrations. Creation of new types requires a Standards Action [RFC8126]. - +======+======+===================================================+ + +------+------+-----------------------------------------------------+ | Type | Type | Specification | | Byte | Name | | - +======+======+===================================================+ + +------+------+-----------------------------------------------------+ | 0x01 | RAND | This is a 128, 192 or 256 bit random number | - | | | generated once and stored in the device. This | - | | | may be constructed by concatenating enough | - | | | identifiers to make up an equivalent number of | - | | | random bits and then feeding the concatenation | - | | | through a cryptographic hash function. It may | - | | | also be a cryptographic quality random number | - | | | generated once at the beginning of the life of | - | | | the device and stored. It may not be smaller | - | | | than 128 bits. | - +------+------+---------------------------------------------------+ + | | | generated once and stored in the device. This may | + | | | be constructed by concatenating enough identifiers | + | | | to make up an equivalent number of random bits and | + | | | then feeding the concatenation through a | + | | | cryptographic hash function. It may also be a | + | | | cryptographic quality random number generated once | + | | | at the beginning of the life of the device and | + | | | stored. It may not be smaller than 128 bits. | | 0x02 | IEEE | This makes use of the IEEE company identification | | | EUI | registry. An EUI is either an EUI-48, EUI-60 or | | | | EUI-64 and made up of an OUI, OUI-36 or a CID, | - | | | different registered company identifiers, and | - | | | some unique per-device identifier. EUIs are | - | | | often the same as or similar to MAC addresses. | - | | | This type includes MAC-48, an obsolete name for | - | | | EUI-48. (Note that while devices with multiple | - | | | network interfaces may have multiple MAC | - | | | addresses, there is only one UEID for a device) | - | | | [IEEE.802-2001], [OUI.Guide] | - +------+------+---------------------------------------------------+ + | | | different registered company identifiers, and some | + | | | unique per-device identifier. EUIs are often the | + | | | same as or similar to MAC addresses. This type | + | | | includes MAC-48, an obsolete name for EUI-48. (Note | + | | | that while devices with multiple network interfaces | + | | | may have multiple MAC addresses, there is only one | + | | | UEID for a device) [IEEE.802-2001], [OUI.Guide] | | 0x03 | IMEI | This is a 14-digit identifier consisting of an | | | | 8-digit Type Allocation Code and a 6-digit serial | | | | number allocated by the manufacturer, which SHALL | | | | be encoded as byte string of length 14 with each | | | | byte as the digit's value (not the ASCII encoding | | | | of the digit; the digit 3 encodes as 0x03, not | | | | 0x33). The IMEI value encoded SHALL NOT include | - | | | Luhn checksum or SVN information. | - | | | [ThreeGPP.IMEI] | - +------+------+---------------------------------------------------+ + | | | Luhn checksum or SVN information. [ThreeGPP.IMEI] | + +------+------+-----------------------------------------------------+ Table 1: UEID Composition Types UEID's are not designed for direct use by humans (e.g., printing on the case of a device), so no textual representation is defined. The consumer (the relying party) of a UEID MUST treat a UEID as a completely opaque string of bytes and not make any use of its internal structure. For example, they should not use the OUI part of a type 0x02 UEID to identify the manufacturer of the device. Instead they should use the oemid claim that is defined elsewhere. The reasons for this are: - * UEIDs types may vary freely from one manufacturer to the next. + o UEIDs types may vary freely from one manufacturer to the next. - * New types of UEIDs may be created. For example, a type 0x07 UEID + o New types of UEIDs may be created. For example, a type 0x07 UEID may be created based on some other manufacturer registration scheme. - * Device manufacturers are allowed to change from one type of UEID + o Device manufacturers are allowed to change from one type of UEID to another anytime they want. For example, they may find they can optimize their manufacturing by switching from type 0x01 to type 0x02 or vice versa. The main requirement on the manufacturer is that UEIDs be universally unique. 3.4.1. ueid CDDL ueid-type = bstr .size (7..33) ueid-claim = ( @@ -578,37 +593,32 @@ 3.5. Origination Claim (origination) TODO: this claim is likely to be dropped in favor of Endorsement identifier and locators. This claim describes the parts of the device or entity that are creating the EAT. Often it will be tied back to the device or chip manufacturer. The following table gives some examples: - +===================+=========================================+ + +-------------------+-----------------------------------------------+ | Name | Description | - +===================+=========================================+ - | Acme-TEE | The EATs are generated in the TEE | - | | authored and configured by "Acme" | - +-------------------+-----------------------------------------+ - | Acme-TPM | The EATs are generated in a TPM | - | | manufactured by "Acme" | - +-------------------+-----------------------------------------+ - | Acme-Linux-Kernel | The EATs are generated in a Linux | - | | kernel configured and shipped by "Acme" | - +-------------------+-----------------------------------------+ + +-------------------+-----------------------------------------------+ + | Acme-TEE | The EATs are generated in the TEE authored | + | | and configured by "Acme" | + | Acme-TPM | The EATs are generated in a TPM manufactured | + | | by "Acme" | + | Acme-Linux-Kernel | The EATs are generated in a Linux kernel | + | | configured and shipped by "Acme" | | Acme-TA | The EATs are generated in a Trusted | | | Application (TA) authored by "Acme" | - +-------------------+-----------------------------------------+ - - Table 2 + +-------------------+-----------------------------------------------+ TODO: consider a more structure approach where the name and the URI and other are in separate fields. TODO: This needs refinement. It is somewhat parallel to issuer claim in CWT in that it describes the authority that created the token. 3.5.1. origination CDDL origination-claim = ( @@ -720,21 +729,21 @@ 3.8. Software Description and Version TODO: Add claims that reference CoSWID. 3.9. The Security Level Claim (security-level) This claim characterizes the device/entity ability to defend against attacks aimed at capturing the signing key, forging claims and at forging EATs. This is done by defining four security levels as described below. This is similar to the key protection types defined - by the Fast Identity Online (FIDO) Alliance [FIDO.Registry]). + by the Fast Identity Online (FIDO) Alliance [FIDO.Registry]. These claims describe security environment and countermeasures available on the end-entity / client device where the attestation key reside and the claims originate. 1 - Unrestricted There is some expectation that implementor will protect the attestation signing keys at this level. Otherwise the EAT provides no meaningful security assurances. 2- Restricted Entities at this level should not be general-purpose @@ -954,24 +962,23 @@ since the last contact with a GPS satellite. Either the timestamp or age data item can be used to quantify the cached period. The timestamp data item is preferred as it a non-relative time. The age data item can be used when the entity doesn't know what time it is either because it doesn't have a clock or it isn't set. The entity must still have a "ticker" that can measure a time interval. The age is the interval between acquisition of the location data and token creation. - See Section 7.2 below. + See location-related privacy considerations in Section 8.2 below. 3.13.1. location CDDL - location-type = { latitude => number, longitude => number, ? altitude => number, ? accuracy => number, ? altitude-accuracy => number, ? heading => number, ? speed => number, ? timestamp => ~time-int, ? age => uint @@ -995,20 +1002,32 @@ The "uptime" claim contains a value that represents the number of seconds that have elapsed since the entity or submod was last booted. 3.14.1. uptime CDDL uptime-claim = ( uptime => uint ) +3.14.2. The Boot Seed Claim (boot-seed) + + The Boot Seed claim is a random value created at system boot time + that will allow differentiation of reports from different boot + sessions. This value is usually public and not protected. It is not + the same as a seed for a random number generator which must be kept + secret. + + boot-seed-claim = ( + boot-seed => bytes + ) + 3.15. The Intended Use Claim (intended-use) EAT's may be used in the context of several different applications. The intended-use claim provides an indication to an EAT consumer about the intended usage of the token. This claim can be used as a way for an application using EAT to internally distinguish between different ways it uses EAT. 1 - Generic Generic attestation describes an application where the EAT consumer requres the most up-to-date security assessment of @@ -1044,114 +1063,130 @@ registration: 2, provisioning: 3, csr: 4, pop: 5 ) intended-use-claim = ( intended-use => intended-use-type ) -3.16. The Submodules Part of a Token (submods) +3.16. The Profile Claim (profile) + + The profile claim is a text string that simply gives the name of the + profile to which the token purports to adhere to. It may name an + IETF document, some other document or no particular document. There + is no requirement that the named document be publicly accessible. + + See Section 5 for a detailed description of a profile. + + Note that this named "eat-profile" for JWT and is distinct from the + already registered "profile" claim in the JWT claims registry. + + profile-claim = ( + profile => tstr + ) + +3.17. The Submodules Part of a Token (submods) Some devices are complex, having many subsystems or submodules. A mobile phone is a good example. It may have several connectivity submodules for communications (e.g., Wi-Fi and cellular). It may have subsystems for low-power audio and video playback. It may have one or more security-oriented subsystems like a TEE or a Secure Element. The claims for each these can be grouped together in a submodule. The submods part of a token are in a single map/object with many entries, one per submodule. There is only one submods map in a token. It is identified by its specific label. It is a peer to other claims, but it is not called a claim because it is a container for a claim set rather than an individual claim. This submods part of a token allows what might be called recursion. It allows claim sets inside of claim sets inside of claims sets... -3.16.1. Two Types of Submodules +3.17.1. Two Types of Submodules Each entry in the submod map is one of two types: - * A non-token submodule that is a map or object directly containing + o A non-token submodule that is a map or object directly containing claims for the submodule. - * A nested EAT that is a fully formed, independently signed EAT + o A nested EAT that is a fully formed, independently signed EAT token -3.16.1.1. Non-token Submodules +3.17.1.1. Non-token Submodules This is simply a map or object containing claims about the submodule. It may contain claims that are the same as its surrounding token or superior submodules. For example, the top-level of the token may have a UEID, a submod may have a different UEID and a further subordinate submodule may also have a UEID. It is signed/encrypted along with the rest of the token and thus the claims are secured by the same Attester with the same signing key as the rest of the token. If a token is in CBOR format (a CWT or a UCCS), all non-token submodules must be CBOR format. If a token in in JSON format (a JWT), all non-token submodules must be in JSON format. When decoding, this type of submodule is recognized from the other type by being a data item of type map for CBOR or type object for JSON. -3.16.1.2. Nested EATs +3.17.1.2. Nested EATs This type of submodule is a fully formed secured EAT as defined in this document except that it MUST NOT be a UCCS or an unsecured JWT. A nested token that is one that is always secured using COSE or JOSE, usually by an independent Attester. When the surrounding EAT is a CWT or secured JWT, the nested token becomes securely bound with the other claims in the surrounding token. It is allowed to have a CWT as a submodule in a JWT and vice versa, but this SHOULD be avoided unless necessary. -3.16.1.2.1. Surrounding EAT is CBOR format +3.17.1.2.1. Surrounding EAT is CBOR format They type of an EAT nested in a CWT is determined by whether the CBOR type is a text string or a byte string. If a text string, then it is a JWT. If a byte string, then it is a CWT. A CWT nested in a CBOR-format token is always wrapped by a byte string for easier handling with standard CBOR decoders and token processing APIs that will typically take a byte buffer as input. Nested CWTs may be either a CWT CBOR tag or a CWT Protocol Message. COSE layers in nested CWT EATs MUST be a COSE_Tagged_Message, never a COSE_Untagged_Message. If a nested EAT has more than one level of COSE, for example one that is both encrypted and signed, a COSE_Tagged_message must be used at every level. -3.16.1.2.2. Surrounding EAT is JSON format +3.17.1.2.2. Surrounding EAT is JSON format When a CWT is nested in a JWT, it must be as a 55799 tag in order to distinguish it from a nested JWT. When a nested EAT in a JWT is decoded, first remove the base64url encoding. Next, check to see if it starts with the bytes 0xd9d9f7. If so, then it is a CWT as a JWT will never start with these four bytes. If not if it is a JWT. Other than the 55799 tag requirement, tag usage for CWT's nested in a JSON format token follow the same rules as for CWTs nested in CBOR- format tokens. It may be a CWT CBOR tag or a CWT Protocol Message and COSE_Tagged_Message MUST be used at all COSE layers. -3.16.1.3. Unsecured JWTs and UCCS Tokens as Submodules +3.17.1.3. Unsecured JWTs and UCCS Tokens as Submodules To incorporate a UCCS token as a submodule, it MUST be as a non-token submodule. This can be accomplished inserting the content of the UCCS Tag into the submodule map. The content of a UCCS tag is exactly a map of claims as required for a non-token submodule. If the UCCS is not a UCCS tag, then it can just be inserted into the submodule map directly. The definition of a nested EAT type of submodule is that it is one that is secured (signed) by an Attester. Since UCCS tokens are @@ -1161,48 +1196,48 @@ To incorporate an Unsecured JWT as a submodule, the null-security JOSE wrapping should be removed. The resulting claims set should be inserted as a non-token submodule. To incorporate a UCCS token in a surrounding JSON token, the UCCS token claims should be translated from CBOR to JSON. To incorporate an Unsecured JWT into a surrounding CBOR-format token, the null- security JOSE should be removed and the claims translated from JSON to CBOR. -3.16.2. No Inheritance +3.17.2. No Inheritance The subordinate modules do not inherit anything from the containing token. The subordinate modules must explicitly include all of their claims. This is the case even for claims like the nonce and age. This rule is in place for simplicity. It avoids complex inheritance rules that might vary from one type of claim to another. -3.16.3. Security Levels +3.17.3. Security Levels The security level of the non-token subordinate modules should always be less than or equal to that of the containing modules in the case of non-token submodules. It makes no sense for a module of lesser security to be signing claims of a module of higher security. An example of this is a TEE signing claims made by the non-TEE parts (e.g. the high-level OS) of the device. The opposite may be true for the nested tokens. They usually have their own more secure key material. An example of this is an embedded secure element. -3.16.4. Submodule Names +3.17.4. Submodule Names The label or name for each submodule in the submods map is a text string naming the submodule. No submodules may have the same name. -3.16.5. submods CDDL +3.17.5. submods CDDL ; The part of a token that contains all the submodules. It is a peer ; with the claims in the token, but not a claim, only a map/object to ; hold all the submodules. submods-part = ( submods => submods-type ) submods-type = { + submod-type } @@ -1224,39 +1259,165 @@ submod-name = tstr 4. Endorsements and Verification Keys TODO: fill this section in. It will discuss key IDs, endorsement ID and such that are needed as input needed to by the Verifier to verify the signature. This will NOT discuss the contents of an Endorsement, just and ID/locator. -5. Encoding +5. Profiles + + This EAT specification does not gaurantee that implementations of it + will interoperate. The variability in this specification is + necessary to accommodate the widely varying use cases. An EAT + profile narrows the specification for a specific use case. An ideal + EAT profile will gauarantee interoperability. + + The profile can be named in the token using the profile claim + described in Section 3.16. + +5.1. List of Profile Issues + + The following is a list of EAT, CWT, UCCS, JWS, COSE, JOSE and CBOR + options that a profile should address. + +5.1.1. Use of JSON, CBOR or both + + The profile should indicate whether the token format should be CBOR, + JSON, both or even some other encoding. If some other encoding, a + specification for how the CDDL described here is serialized in that + encoding is necessary. + + This should be addressed for the top-level token and for any nested + tokens. For example, a profile might require all nested tokens to be + of the same encoding of the top level token. + +5.1.2. CBOR Map and Array Encoding + + The profile should indicate whether definite-length arrays/maps, + indefinite-length arrays/maps or both are allowed. A good default is + to allow only definite-length arrays/maps. + + An alternate is to allow both definite and indefinite-length arrays/ + maps. The decoder should accept either. Encoders that need to fit + on very small hardware or be actually implement in hardware can use + indefinite-length encoding. + + This applies to individual EAT claims, CWT and COSE parts of the + implementation. + +5.1.3. CBOR String Encoding + + The profile should indicate whether definite-length strings, + indefinite-length strings or both are allowed. A good default is to + allow only definite-length strings. As with map and array encoding, + allowing indefinite-length strings can be beneficial for some smaller + implementations. + +5.1.4. COSE/JOSE Protection + + COSE and JOSE have several options for signed, MACed and encrypted + messages. EAT/CWT has the option to have no protection using UCCS + and JOSE has a NULL protection option. It is possible to implement + no protection, sign only, MAC only, sign then encrypt and so on. All + combinations allowed by COSE, JOSE, JWT, CWT and UCCS are allowed by + EAT. + + The profile should list the protections that must be supported by all + decoders implementing the profile. The encoders them must implement + a subset of what is listed for the decoders, perhaps only one. + + Implementations may choose to sign or MAC before encryption so that + the implementation layer doing the signing or MACing can be the + smallest. It is often easier to make smaller implementations more + secure, perhaps even implementing in solely in hardware. The key + material for a signature or MAC is a private key, while for + encryption it is likely to be a public key. The key for encryption + requires less protection. + +5.1.5. COSE/JOSE Algorithms + + The profile document should list the COSE algorithms that a Verifier + must implement. The Attester will select one of them. Since there + is no negotiation, the Verifier should implement all algorithms + listed in the profile. + +5.1.6. Verification Key Identification + + Section Section 4 describes a number of methods for identifying a + verification key. The profile document should specify one of these + or one that is not described. The ones described in this document + are only roughly described. The profile document should go into the + full detail. + +5.1.7. Endorsement Identification + + Similar to, or perhaps the same as Verification Key Identification, + the profile may wish to specify how Endorsements are to be + identified. However note that Endorsement Identification is + optional, where as key identification is not. + +5.1.8. Required Claims + + The profile can list claims whose absence results in Verification + failure. + +5.1.9. Prohibited Claims + + The profile can list claims whose presence results in Verification + failure. + +5.1.10. Additional Claims + + The profile may describe entirely new claims. These claims can be + required or optional. + +5.1.11. Refined Claim Definition + + The profile may lock down optional aspects of individual claims. For + example, it may require altitude in the location claim, or it may + require that HW Versions always be described using EAN-13. + +5.1.12. CBOR Tags + + The profile should specify whether the token should be a CWT Tag or + not. Similarly, the profile should specify whether the token should + be a UCCS tag or not. + + When COSE protection is used, the profile should specify whether COSE + tags are used or not. Note that RFC 8392 requires COSE tags be used + in a CWT tag. + + Often a tag is unncessary because the surrounding or carrying + protocol identifies the object as an EAT. + +6. Encoding This makes use of the types defined in CDDL Appendix D, Standard Prelude. Some of the CDDL included here is for claims that are defined in CWT [RFC8392] or JWT [RFC7519] or are in the IANA CWT or JWT registries. CDDL was not in use when these claims where defined. -5.1. Common CDDL Types +6.1. Common CDDL Types time-int is identical to the epoch-based time, but disallows floating-point representation. string-or-uri = tstr time-int = #6.1(int) -5.2. CDDL for CWT-defined Claims +6.2. CDDL for CWT-defined Claims This section provides CDDL for the claims defined in CWT. It is non- normative as [RFC8392] is the authoritative definition of these claims. $$eat-extension //= ( ? issuer => text, ? subject => text, ? audience => text, ? expiration => time, @@ -1266,135 +1427,128 @@ ) issuer = 1 subject = 2 audience = 3 expiration = 4 not-before = 5 issued-at = 6 cwt-id = 7 -5.3. JSON +6.3. JSON + +6.3.1. JSON Labels -5.3.1. JSON Labels ueid /= "ueid" nonce /= "nonce" origination /= "origination" oemid /= "oemid" security-level /= "security-level" secure-boot /= "secure-boot" debug-status /= "debug-status" location /= "location" age /= "age" uptime /= "uptime" + profile /= "eat-profile" + boot-seed /= "bootseed" submods /= "submods" timestamp /= "timestamp" latitude /= "lat" longitude /= "long" altitude /= "alt" accuracy /= "accry" altitude-accuracy /= "alt-accry" heading /= "heading" speed /= "speed" -5.3.2. JSON Interoperability +6.3.2. JSON Interoperability JSON should be encoded per RFC 8610 Appendix E. In addition, the following CDDL types are encoded in JSON as follows: - * bstr - must be base64url encoded + o bstr - must be base64url encoded - * time - must be encoded as NumericDate as described section 2 of + o time - must be encoded as NumericDate as described section 2 of [RFC7519]. - * string-or-uri - must be encoded as StringOrURI as described + o string-or-uri - must be encoded as StringOrURI as described section 2 of [RFC7519]. -5.4. CBOR - -5.4.1. CBOR Interoperability +6.4. CBOR - Variations in the CBOR serializations supported in CBOR encoding and - decoding are allowed and suggests that CBOR-based protocols specify - how this variation is handled. This section specifies what formats - MUST be supported in order to achieve interoperability. +6.4.1. CBOR Interoperability - The assumption is that the entity is likely to be a constrained - device and relying party is likely to be a very capable server. The - approach taken is that the entity generating the token can use - whatever encoding it wants, specifically encodings that are easier to - implement such as indefinite lengths. The relying party receiving - the token must support decoding all encodings. + CBOR allows data items to be serialized in more than one form. If + the sender uses a form that the receiver can't decode, there will not + be interoperability. - These rules cover all types used in the claims in this document. - They also are recommendations for additional claims. + This specification gives no blanket requirements to narrow CBOR + serialization for all uses of EAT. This allows individual uses to + tailor serialization to the environment. It also may result in EAT + implementations that don't interoperate. - Canonical CBOR encoding, Preferred Serialization and - Deterministically Encoded CBOR are explicitly NOT required as they - would place an unnecessary burden on the entity implementation, - particularly if the entity implementation is implemented in hardware. + One way to guarantee interoperability is to clearly specify CBOR + serialization in a profile document. See Section 5 for a list of + serialization issues that should be addressed. - * Integer Encoding (major type 0, 1) - The entity may use any - integer encoding allowed by CBOR. The server MUST accept all - integer encodings allowed by CBOR. + EAT will be commonly used where the device generating the attestation + is constrained and the receiver/verifier of the attestation is a + capacious server. Following is a set of serialization requirements + that work well for that use case and are guaranteed to interoperate. + Use of this serialization is recommended where possible, but not + required. An EAT profile may just reference the following section + rather than spell out serialization details. - * String Encoding (major type 2 and 3) - The entity can use any - string encoding allowed by CBOR including indefinite lengths. It - may also encode the lengths of strings in any way allowed by CBOR. - The server must accept all string encodings. +6.4.1.1. EAT Constrained Device Serialization - * Major type 2, bstr, SHOULD have tag 21 to indicate conversion to - base64url in case that conversion is performed. + o Preferred serialization described in section 4.1 of [RFC8949] is + not required. The EAT decoder must accept all forms of number + serialization. The EAT encoder may use any form it wishes. - * Map and Array Encoding (major type 4 and 5) - The entity can use - any array or map encoding allowed by CBOR including indefinite - lengths. Sorting of map keys is not required. Duplicate map keys - are not allowed. The server must accept all array and map - encodings. The server may reject maps with duplicate map keys. + o The EAT decoder must accept indefinite length arrays and maps as + described in section 3.2.2 of [RFC8949]. The EAT encoder may use + indefinite length arrays and maps if it wishes. - * Date and Time - The entity should send dates as tag 1 encoded as - 64-bit or 32-bit integers. The entity may not send floating-point - dates. The server must support tag 1 epoch-based dates encoded as - 64-bit or 32-bit integers. The entity may send tag 0 dates, - however tag 1 is preferred. The server must support tag 0 UTC - dates. + o The EAT decoder must accept indefinite length strings as described + in section 3.2.3 of [RFC8949]. The EAT encoder may use indefinite + length strings if it wishes. - * URIs - URIs should be encoded as text strings and marked with tag - 32. + o Sorting of maps by key is not required. The EAT decoder must not + rely on sorting. - * Floating Point - The entity may use any floating-point encoding. - The relying party must support decoding of all types of floating- - point. + o Deterministic encoding described in Section 4.2 of [RFC8949] is + not required. - * Other types - Other types like bignums, regular expressions and - such, SHOULD NOT be used. The server MAY support them but is not - required to so interoperability is not guaranteed. + o Basic validity described in section 5.3.1 of [RFC8949] must be + followed. The EAT encoder must not send duplicate map keys/labels + or invalid UTF-8 strings. -5.5. Collected CDDL +6.5. Collected CDDL ; This is the top-level definition of the claims in EAT tokens. To ; form an actual EAT Token, this claim set is enclosed in a COSE, JOSE ; or UCCS message. -; TO-DO: Add intended-use claim eat-claim-set = { ? ueid-claim, ? nonce-claim, ? origination-claim, ? oemid-claim, ? hardware-version-claims, ? security-level-claim, ? secure-boot-claim, ? debug-status-claim, ? location-claim, + ? profile-claim, ? uptime-claim, + ? boot-seed-claim, ? submods-part, * $$eat-extension, } ; This is the top-level definition of an EAT Token. It is a CWT, JWT ; or UCSS where the payload is an eat-claim-set. A JWT_Message is what ; is defined by JWT in RFC 7519. (RFC 7519 doesn't use CDDL so a there ; is no actual CDDL definition of JWT_Message). eat-token = EAT_Tagged_Message / EAT_Untagged_Message / JWT_Message @@ -1402,41 +1556,46 @@ ; This is CBOR-format EAT token in the CWT or UCCS format that is a ; tag. COSE_Tagged_message is defined in RFC 8152. Tag 601 is ; proposed by the UCCS draft, but not yet assigned. EAT_Tagged_Message = #6.61(COSE_Tagged_Message) / #6.601(eat-claim-set) ; This is a CBOR-format EAT token that is a CWT or UCSS that is not a ; tag COSE_Tagged_message and COSE_Untagged_Message are defined in RFC ; 8152. -EAT_Untagged_Message = COSE_Tagged_Message / COSE_Untagged_Message / UCCS_Untagged_Message + EAT_Untagged_Message = COSE_Tagged_Message / + COSE_Untagged_Message / + UCCS_Untagged_Message + ; This is an "unwrapped" UCCS tag. Unwrapping a tag means to use the ; definition of its content without the preceding type 6 tag ; integer. Since a UCCS is nothing but a tag for an unsecured CWT ; claim set, unwrapping reduces to a bare eat-claim-set. UCCS_Untagged_Message = eat-claim-set ; The following Claim Keys (labels) are temporary. They are not ; assigned by IANA nonce = 10 ueid = 11 origination = 12 oemid = 13 security-level = 14 secure-boot = 15 debug-status = 16 location = 17 + profile = 18 uptime = 19 submods = 20 + boot-seed = 21 chip-version = 21 board-version = 22 device-version = 23 chip-version-scheme = 24 board-version-scheme = 25 device-version-scheme = 26 ean-chip-version = 27 ean-board-version = 28 ean-device-version = 29 @@ -1571,36 +1725,34 @@ ? board-version-scheme-claim, ? device-version-scheme-claim, ? ean-chip-version-claim, ? ean-board-version-claim, ? ean-device-version-claim, ) origination-claim = ( origination => string-or-uri ) - secure-boot-claim = ( secure-boot => bool ) - security-level-type = &( unrestricted: 1, restricted: 2, secure-restricted: 3, hardware: 4 ) security-level-claim = ( security-level => security-level-type -) + ) ; The part of a token that contains all the submodules. It is a peer ; with the claims in the token, but not a claim, only a map/object to ; hold all the submodules. submods-part = ( submods => submods-type ) submods-type = { + submod-type } @@ -1620,267 +1772,273 @@ ; Each submodule has a unique text string name. submod-name = tstr ueid-type = bstr .size (7..33) ueid-claim = ( ueid => ueid-type ) - uptime-claim = ( uptime => uint ) - + profile-claim = ( + profile => tstr + ) + boot-seed-claim = ( + boot-seed => bytes + ) ueid /= "ueid" nonce /= "nonce" origination /= "origination" oemid /= "oemid" security-level /= "security-level" secure-boot /= "secure-boot" debug-status /= "debug-status" location /= "location" age /= "age" uptime /= "uptime" + profile /= "eat-profile" + boot-seed /= "bootseed" submods /= "submods" timestamp /= "timestamp" latitude /= "lat" longitude /= "long" altitude /= "alt" accuracy /= "accry" altitude-accuracy /= "alt-accry" heading /= "heading" speed /= "speed" -6. IANA Considerations +7. IANA Considerations -6.1. Reuse of CBOR Web Token (CWT) Claims Registry +7.1. Reuse of CBOR Web Token (CWT) Claims Registry Claims defined for EAT are compatible with those of CWT so the CWT Claims Registry is re used. No new IANA registry is created. All EAT claims should be registered in the CWT and JWT Claims Registries. -6.2. Claim Characteristics +7.2. Claim Characteristics The following is design guidance for creating new EAT claims, particularly those to be registered with IANA. Much of this guidance is generic and could also be considered when designing new CWT or JWT claims. -6.2.1. Interoperability and Relying Party Orientation +7.2.1. Interoperability and Relying Party Orientation It is a broad goal that EATs can be processed by relying parties in a general way regardless of the type, manufacturer or technology of the device from which they originate. It is a goal that there be general-purpose verification implementations that can verify tokens for large numbers of use cases with special cases and configurations for different device types. This is a goal of interoperability of the semantics of claims themselves, not just of the signing, encoding and serialization formats. This is a lofty goal and difficult to achieve broadly requiring careful definition of claims in a technology neutral way. Sometimes it will be difficult to design a claim that can represent the semantics of data from very different device types. However, the goal remains even when difficult. -6.2.2. Operating System and Technology Neutral +7.2.2. Operating System and Technology Neutral Claims should be defined such that they are not specific to an operating system. They should be applicable to multiple large high- level operating systems from different vendors. They should also be applicable to multiple small embedded operating systems from multiple vendors and everything in between. Claims should not be defined such that they are specific to a SW environment or programming language. Claims should not be defined such that they are specific to a chip or particular hardware. For example, they should not just be the contents of some HW status register as it is unlikely that the same HW status register with the same bits exists on a chip of a different manufacturer. The boot and debug state claims in this document are an example of a claim that has been defined in this neutral way. -6.2.3. Security Level Neutral +7.2.3. Security Level Neutral Many use cases will have EATs generated by some of the most secure hardware and software that exists. Secure Elements and smart cards are examples of this. However, EAT is intended for use in low- security use cases the same as high-security use case. For example, an app on a mobile device may generate EATs on its own. Claims should be defined and registered on the basis of whether they are useful and interoperable, not based on security level. In particular, there should be no exclusion of claims because they are just used only in low-security environments. -6.2.4. Reuse of Extant Data Formats +7.2.4. Reuse of Extant Data Formats Where possible, claims should use already standardized data items, identifiers and formats. This takes advantage of the expertise put into creating those formats and improves interoperability. Often extant claims will not be defined in an encoding or serialization format used by EAT. It is preferred to define a CBOR and JSON format for them so that EAT implementations do not require a plethora of encoders and decoders for serialization formats. In some cases, it may be better to use the encoding and serialization as is. For example, signed X.509 certificates and CRLs can be carried as-is in a byte string. This retains interoperability with the extensive infrastructure for creating and processing X.509 certificates and CRLs. -6.2.5. Proprietary Claims +7.2.5. Proprietary Claims EAT allows the definition and use of proprietary claims. For example, a device manufacturer may generate a token with proprietary claims intended only for verification by a service offered by that device manufacturer. This is a supported use case. In many cases proprietary claims will be the easiest and most obvious way to proceed, however for better interoperability, use of general standardized claims is preferred. -6.3. Claims Registered by This Document +7.3. Claims Registered by This Document - * Claim Name: UEID + o Claim Name: UEID - * Claim Description: The Universal Entity ID + o Claim Description: The Universal Entity ID - * JWT Claim Name: N/A + o JWT Claim Name: N/A - * Claim Key: 8 + o Claim Key: 8 - * Claim Value Type(s): byte string + o Claim Value Type(s): byte string - * Change Controller: IESG + o Change Controller: IESG - * Specification Document(s): *this document* + o Specification Document(s): *this document* TODO: add the rest of the claims in here -7. Privacy Considerations +8. Privacy Considerations Certain EAT claims can be used to track the owner of an entity and therefore, implementations should consider providing privacy- preserving options dependent on the intended usage of the EAT. Examples would include suppression of location claims for EAT's provided to unauthenticated consumers. -7.1. UEID Privacy Considerations +8.1. UEID Privacy Considerations A UEID is usually not privacy-preserving. Any set of relying parties that receives tokens that happen to be from a single device will be able to know the tokens are all from the same device and be able to track the device. Thus, in many usage situations ueid violates governmental privacy regulation. In other usage situations UEID will not be allowed for certain products like browsers that give privacy for the end user. It will often be the case that tokens will not have a UEID for these reasons. There are several strategies that can be used to still be able to put UEID's in tokens: - * The device obtains explicit permission from the user of the device + o The device obtains explicit permission from the user of the device to use the UEID. This may be through a prompt. It may also be through a license agreement. For example, agreements for some online banking and brokerage services might already cover use of a UEID. - * The UEID is used only in a particular context or particular use + o The UEID is used only in a particular context or particular use case. It is used only by one relying party. - * The device authenticates the relying party and generates a derived + o The device authenticates the relying party and generates a derived UEID just for that particular relying party. For example, the relying party could prove their identity cryptographically to the device, then the device generates a UEID just for that relying party by hashing a proofed relying party ID with the main device UEID. Note that some of these privacy preservation strategies result in multiple UEIDs per device. Each UEID is used in a different context, use case or system on the device. However, from the view of the relying party, there is just one UEID and it is still globally universal across manufacturers. -7.2. Location Privacy Considerations +8.2. Location Privacy Considerations Geographic location is most always considered personally identifiable information. Implementers should consider laws and regulations governing the transmission of location data from end user devices to servers and services. Implementers should consider using location management facilities offered by the operating system on the device generating the attestation. For example, many mobile phones prompt the user for permission when before sending location data. -8. Security Considerations +9. Security Considerations The security considerations provided in Section 8 of [RFC8392] and Section 11 of [RFC7519] apply to EAT in its CWT and JWT form, respectively. In addition, implementors should consider the following. -8.1. Key Provisioning +9.1. Key Provisioning Private key material can be used to sign and/or encrypt the EAT, or can be used to derive the keys used for signing and/or encryption. In some instances, the manufacturer of the entity may create the key material separately and provision the key material in the entity itself. The manfuacturer of any entity that is capable of producing an EAT should take care to ensure that any private key material be suitably protected prior to provisioning the key material in the entity itself. This can require creation of key material in an enclave (see [RFC4949] for definition of "enclave"), secure transmission of the key material from the enclave to the entity using an appropriate protocol, and persistence of the private key material in some form of secure storage to which (preferably) only the entity has access. -8.1.1. Transmission of Key Material +9.1.1. Transmission of Key Material Regarding transmission of key material from the enclave to the entity, the key material may pass through one or more intermediaries. Therefore some form of protection ("key wrapping") may be necessary. The transmission itself may be performed electronically, but can also be done by human courier. In the latter case, there should be minimal to no exposure of the key material to the human (e.g. encrypted portable memory). Moreover, the human should transport the key material directly from the secure enclave where it was created to a destination secure enclave where it can be provisioned. -8.2. Transport Security +9.2. Transport Security As stated in Section 8 of [RFC8392], "The security of the CWT relies upon on the protections offered by COSE". Similar considerations apply to EAT when sent as a CWT. However, EAT introduces the concept of a nonce to protect against replay. Since an EAT may be created by an entity that may not support the same type of transport security as the consumer of the EAT, intermediaries may be required to bridge communications between the entity and consumer. As a result, it is RECOMMENDED that both the consumer create a nonce, and the entity leverage the nonce along with COSE mechanisms for encryption and/or signing to create the EAT. Similar considerations apply to the use of EAT as a JWT. Although the security of a JWT leverages the JSON Web Encryption (JWE) and JSON Web Signature (JWS) specifications, it is still recommended to make use of the EAT nonce. -8.3. Multiple EAT Consumers +9.3. Multiple EAT Consumers In many cases, more than one EAT consumer may be required to fully verify the entity attestation. Examples include individual consumers for nested EATs, or consumers for individual claims with an EAT. When multiple consumers are required for verification of an EAT, it is important to minimize information exposure to each consumer. In addition, the communication between multiple consumers should be secure. For instance, consider the example of an encrypted and signed EAT @@ -1892,23 +2050,23 @@ subsets to any downstream consumer should leverage a secure protocol (e.g.one that uses transport-layer security, i.e. TLS), However, assume the EAT of the previous example is hierarchical and each claim subset for a downstream consumer is created in the form of a nested EAT. Then transport security between the receiving and downstream consumers is not strictly required. Nevertheless, downstream consumers of a nested EAT should provide a nonce unique to the EAT they are consuming. -9. References +10. References -9.1. Normative References +10.1. Normative References [CoSWID] "Concise Software Identification Tags", November 2020, . [EAN-13] GS1, "International Article Number - EAN/UPC barcodes", 2019, . [FIDO.AROE] The FIDO Alliance, "FIDO Authenticator Allowed Restricted Operating Environments List", November 2019, @@ -1921,24 +2079,20 @@ [IANA.JWT.Claims] IANA, "JSON Web Token (JWT) Claims", . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . - [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object - Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, - October 2013, . - [RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517, DOI 10.17487/RFC7517, May 2015, . [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, . [RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of- Possession Key Semantics for JSON Web Tokens (JWTs)", @@ -1966,50 +2120,43 @@ 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, . [RFC8747] Jones, M., Seitz, L., Selander, G., Erdtman, S., and H. Tschofenig, "Proof-of-Possession Key Semantics for CBOR Web Tokens (CWTs)", RFC 8747, DOI 10.17487/RFC8747, March 2020, . + [RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object + Representation (CBOR)", STD 94, RFC 8949, + DOI 10.17487/RFC8949, December 2020, + . + [ThreeGPP.IMEI] 3GPP, "3rd Generation Partnership Project; Technical Specification Group Core Network and Terminals; Numbering, addressing and identification", 2019, . - [TIME_T] The Open Group Base Specifications, "Vol. 1: Base - Definitions, Issue 7", Section 4.15 'Seconds Since the - Epoch', IEEE Std 1003.1, 2013 Edition, 2013, - . - [UCCS.Draft] Birkholz, H., "A CBOR Tag for Unprotected CWT Claims Sets", 2020, . [WGS84] National Imagery and Mapping Agency, "National Imagery and Mapping Agency Technical Report 8350.2, Third Edition", 2000, . -9.2. Informative References - - [ASN.1] International Telecommunication Union, "Information - Technology -- ASN.1 encoding rules: Specification of Basic - Encoding Rules (BER), Canonical Encoding Rules (CER) and - Distinguished Encoding Rules (DER)", ITU-T Recommendation - X.690, 1994. +10.2. Informative References [BirthdayAttack] "Birthday attack", . [Common.Criteria] "Common Criteria for Information Technology Security Evaluation", April 2017, . @@ -2017,21 +2164,22 @@ "Ecma International, "ECMAScript Language Specification, 5.1 Edition", ECMA Standard 262", June 2011, . [FIDO.Registry] The FIDO Alliance, "FIDO Registry of Predefined Values", December 2019, . - [FIPS-140] National Institue of Standards, "Security Requirements for + [FIPS-140] + National Institue of Standards, "Security Requirements for Cryptographic Modules", May 2001, . [IDevID] "IEEE Standard, "IEEE 802.1AR Secure Device Identifier"", December 2009, . [IEEE.802-2001] "IEEE Standard For Local And Metropolitan Area Networks @@ -2062,45 +2210,43 @@ [RFC4949] Shirey, R., "Internet Security Glossary, Version 2", FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007, . [W3C.GeoLoc] Worldwide Web Consortium, "Geolocation API Specification 2nd Edition", January 2018, . - [Webauthn] Worldwide Web Consortium, "Web Authentication: A Web API - for accessing scoped credentials", 2016. - Appendix A. Examples A.1. Very Simple EAT This is shown in CBOR diagnostic form. Only the payload signed by COSE is shown. { / issuer / 1: "joe", / nonce / 10: h'948f8860d13a463e8e', - / UEID / 11: h'0198f50a4ff6c05861c8860d13a638ea4fe2fa', + / UEID / 11: h'0198f50a4ff6c05861c8860d13a638ea', / secure-boot / 15: true, / debug-disable / 16: 3, / permanent-disable / / timestamp (iat) / 6: 1(1526542894), / chip-version / 21: "1.4a", / chip-version-scheme / 24: 2 / multipartnumeric+suffix / } A.2. Example with Submodules, Nesting and Security Levels + { / nonce / 10: h'948f8860d13a463e8e', - / UEID / 11: h'0198f50a4ff6c05861c8860d13a638ea4fe2fa', + / UEID / 11: h'0198f50a4ff6c05861c8860d13a638ea' / secure-boot / 15: true, / debug-disable / 16: 3, / permanent-disable / / timestamp (iat) / 6: 1(1526542894), / security-level / 14: 3, / secure restricted OS / / submods / 20: { / first submod, an Android Application / "Android App Foo" : { / security-level / 14: 1 / unrestricted / }, @@ -2138,43 +2284,39 @@ the limit of what is imaginable and should probably be accommodated. The 100 quadrillion datadbase is highly speculative perhaps involving nanorobots for every person, livestock animal and domesticated bird. It is included to round out the analysis. Note that the items counted here certainly do not have IP address and are not individually connected to the network. They may be connected to internal buses, via serial links, Bluetooth and so on. This is not the same problem as sizing IP addresses. - +=========+===========+============+==========+=================+ - | People | Devices / | Subsystems | Database | Database Size | - | | Person | / Device | Portion | | - +=========+===========+============+==========+=================+ + +---------+------------+--------------+------------+----------------+ + | People | Devices / | Subsystems / | Database | Database Size | + | | Person | Device | Portion | | + +---------+------------+--------------+------------+----------------+ | 10 | 100 | 10 | 10% | trillion | | billion | | | | (10^12) | - +---------+-----------+------------+----------+-----------------+ | 10 | 100,000 | 10 | 10% | quadrillion | | billion | | | | (10^15) | - +---------+-----------+------------+----------+-----------------+ - | 100 | 1,000,000 | 10 | 10% | 100 quadrillion | - | billion | | | | (10^17) | - +---------+-----------+------------+----------+-----------------+ - - Table 3 + | 100 | 1,000,000 | 10 | 10% | 100 | + | billion | | | | quadrillion | + | | | | | (10^17) | + +---------+------------+--------------+------------+----------------+ This is conceptually similar to the Birthday Problem where m is the number of possible birthdays, always 365, and k is the number of people. It is also conceptually similar to the Birthday Attack where collisions of the output of hash functions are considered. The proper formula for the collision calculation is - p = 1 - e^{-k^2/(2n)} p Collision Probability n Total possible population k Actual population However, for the very large values involved here, this formula requires floating point precision higher than commonly available in calculators and SW so this simple approximation is used. See [BirthdayAttack]. @@ -2180,32 +2322,28 @@ [BirthdayAttack]. p = k^2 / 2n For this calculation: p Collision Probability n Total population based on number of bits in UEID k Population in a database - +=====================+==============+==============+==============+ + +----------------------+--------------+--------------+--------------+ | Database Size | 128-bit UEID | 192-bit UEID | 256-bit UEID | - +=====================+==============+==============+==============+ + +----------------------+--------------+--------------+--------------+ | trillion (10^12) | 2 * 10^-15 | 8 * 10^-35 | 5 * 10^-55 | - +---------------------+--------------+--------------+--------------+ | quadrillion (10^15) | 2 * 10^-09 | 8 * 10^-29 | 5 * 10^-49 | - +---------------------+--------------+--------------+--------------+ | 100 quadrillion | 2 * 10^-05 | 8 * 10^-25 | 5 * 10^-45 | | (10^17) | | | | - +---------------------+--------------+--------------+--------------+ - - Table 4 + +----------------------+--------------+--------------+--------------+ Next, to calculate the probability of a collision occurring in one year's operation of a database, it is assumed that the database size is in a steady state and that 10% of the database changes per year. For example, a trillion record database would have 100 billion states per year. Each of those states has the above calculated probability of a collision. This assumption is a worst-case since it assumes that each state of the database is completely independent from the previous state. In @@ -2215,32 +2353,28 @@ The following tables gives the time interval until there is a probability of a collision based on there being one tenth the number of states per year as the number of records in the database. t = 1 / ((k / 10) * p) t Time until a collision p Collision probability for UEID size k Database size - +=====================+==============+==============+==============+ + +---------------------+---------------+--------------+--------------+ | Database Size | 128-bit UEID | 192-bit UEID | 256-bit UEID | - +=====================+==============+==============+==============+ + +---------------------+---------------+--------------+--------------+ | trillion (10^12) | 60,000 years | 10^24 years | 10^44 years | - +---------------------+--------------+--------------+--------------+ | quadrillion (10^15) | 8 seconds | 10^14 years | 10^34 years | - +---------------------+--------------+--------------+--------------+ | 100 quadrillion | 8 | 10^11 years | 10^31 years | | (10^17) | microseconds | | | - +---------------------+--------------+--------------+--------------+ - - Table 5 + +---------------------+---------------+--------------+--------------+ Clearly, 128 bits is enough for the near future thus the requirement that UEIDs be a minimum of 128 bits. There is no requirement for 256 bits today as quadrillion-record databases are not expected in the near future and because this time- to-collision calculation is a very worst case. A future update of the standard may increase the requirement to 256 bits, so there is a requirement that implementations be able to receive 256-bit UEIDs. @@ -2274,122 +2408,131 @@ as they are implemented in commonly used CPU hardware. Appendix C. Changes from Previous Drafts The following is a list of known changes from the previous drafts. This list is non-authoritative. It is meant to help reviewers see the significant differences. C.1. From draft-rats-eat-01 - * Added UEID design rationale appendix + o Added UEID design rationale appendix C.2. From draft-mandyam-rats-eat-00 This is a fairly large change in the orientation of the document, but no new claims have been added. - * Separate information and data model using CDDL. + o Separate information and data model using CDDL. - * Say an EAT is a CWT or JWT + o Say an EAT is a CWT or JWT - * Use a map to structure the boot_state and location claims + o Use a map to structure the boot_state and location claims C.3. From draft-ietf-rats-eat-01 - * Clarifications and corrections for OEMID claim + o Clarifications and corrections for OEMID claim - * Minor spelling and other fixes + o Minor spelling and other fixes - * Add the nonce claim, clarify jti claim + o Add the nonce claim, clarify jti claim C.4. From draft-ietf-rats-eat-02 - * Roll all EUIs back into one UEID type + o Roll all EUIs back into one UEID type - * UEIDs can be one of three lengths, 128, 192 and 256. + o UEIDs can be one of three lengths, 128, 192 and 256. - * Added appendix justifying UEID design and size. + o Added appendix justifying UEID design and size. - * Submods part now includes nested eat tokens so they can be named + o Submods part now includes nested eat tokens so they can be named and there can be more tha one of them - * Lots of fixes to the CDDL + o Lots of fixes to the CDDL - * Added security considerations + o Added security considerations C.5. From draft-ietf-rats-eat-03 - * Split boot_state into secure-boot and debug-disable claims + o Split boot_state into secure-boot and debug-disable claims - * Debug disable is an enumerated type rather than Booleans + o Debug disable is an enumerated type rather than Booleans C.6. From draft-ietf-rats-eat-04 - * Change IMEI-based UEIDs to be encoded as a 14-byte string + o Change IMEI-based UEIDs to be encoded as a 14-byte string - * CDDL cleaned up some more + o CDDL cleaned up some more - * CDDL allows for JWTs and UCCSs - * CWT format submodules are byte string wrapped + o CDDL allows for JWTs and UCCSs - * Allows for JWT nested in CWT and vice versa + o CWT format submodules are byte string wrapped - * Allows UCCS (unsigned CWTs) and JWT unsecured tokens + o Allows for JWT nested in CWT and vice versa - * Clarify tag usage when nesting tokens + o Allows UCCS (unsigned CWTs) and JWT unsecured tokens - * Add section on key inclusion + o Clarify tag usage when nesting tokens - * Add hardware version claims + o Add section on key inclusion - * Collected CDDL is now filled in. Other CDDL corrections. + o Add hardware version claims - * Rename debug-disable to debug-status; clarify that it is not + o Collected CDDL is now filled in. Other CDDL corrections. + + o Rename debug-disable to debug-status; clarify that it is not extensible - * Security level claim is not extensible + o Security level claim is not extensible - * Improve specification of location claim and added a location + o Improve specification of location claim and added a location privacy section - * Add intended use claim + o Add intended use claim -C.7. From draft-ietf-rats-eat-05 +C.7. From draft-ietf-rats-05 - * CDDL format issues resolved + o CDDL format issues resolved - * Corrected reference to Location Privacy section + o Corrected reference to Location Privacy section + +C.8. From draft-ietf-rats-06 + + o Added boot-seed claim + + o Rework CBOR interoperability section + + o Added profiles claim and section Authors' Addresses Giridhar Mandyam Qualcomm Technologies Inc. 5775 Morehouse Drive San Diego, California - United States of America + USA Phone: +1 858 651 7200 - Email: mandyam@qti.qualcomm.com + EMail: mandyam@qti.qualcomm.com Laurence Lundblade Security Theory LLC - Email: lgl@island-resort.com + EMail: lgl@island-resort.com + Miguel Ballesteros Qualcomm Technologies Inc. 5775 Morehouse Drive San Diego, California - United States of America + USA Phone: +1 858 651 4299 - Email: mballest@qti.qualcomm.com + EMail: mballest@qti.qualcomm.com Jeremy O'Donoghue Qualcomm Technologies Inc. 279 Farnborough Road - Farnborough - GU14 7LS + Farnborough GU14 7LS United Kingdom Phone: +44 1252 363189 - Email: jodonogh@qti.qualcomm.com + EMail: jodonogh@qti.qualcomm.com