| Internet-Draft | SRI Signature Profile | November 2024 |
| West | Expires 25 May 2025 | [Page] |
An HTTP Message Signature profile that specifies the requirements for signatures intended as proofs of integrity/provenance that can be enforced upon by clients without any pre-existing relationship to the server which delivered them.¶
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://mikewest.github.io/rfc9421-sri-profile/draft-west-sri-signature-profile.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-west-sri-signature-profile/.¶
Source for this draft and an issue tracker can be found at https://github.com/mikewest/rfc9421-sri-profile.¶
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This document defines an HTTP Message Signature profile that specifies the requirements for signatures intended as proofs of integrity/provenance that can be enforced upon by clients without any pre-existing relationship to the server which delivered them. This requires locking down the components and properties of the signature itself, as well as some of the decision points available during the generation of the signature base (Section 2.5 of [RFC9421]).¶
In short: this profile supports only Ed25519 signatures, requires that the public key portion of the verification key material be included in the signature's input, and specifies the ordering of the components and properties to remove potential ambiguity about the signature's construction.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
The following requirements define a profile of HTTP Message Signatures that enables clients to verify a response's signature without any additional information, following the guidelines laid out in Section 1.4 of [RFC9421]:¶
The signature's input MUST:¶
Include the following component identifiers (Section 2 of [RFC9421]) with their associated constraints:¶
identity-digest, which MUST include the sf parameter (Section 2.1
of RFC9421}}) and no other parameters.¶
Include the following parameters (Section 2.3 of [RFC9421]) with their associated constraints:¶
Order the signature's parameters alphabetically.¶
The signature's input MAY:¶
The identity-digest component references the Identity-Digest header defined in
[I-D.pardue-http-identity-digest]. It is expected to be a Dictionary Structured
Field (Section 3.2 of [STRUCTURED-FIELDS]).¶
The public key of the verification key material can be directly extracted from
the signature input's keyid parameter, where it's represented as a
base64-encoded string (Section 4 of [RFC4648]).¶
The only signature algorithm allowed is ed25519.¶
Since the only accepted algorithm is ed25519, it is appropriate for any
context in which this profile will be used, and we require it to be specified
as the alg parameter to the signature's input.¶
The context for derivation of message components from an HTTP message and its application context is the HTTP message itself, encompassing the response with which the signature was delivered, and the request to which it responds.¶
No error reporting is required.¶
Clients MUST represent verification failures as network errors, consistent with [FETCH]'s handling of other server-specified constraints on the usage of response data.¶
This profile has no security considerations beyond those specified in [RFC9421] itself, and in [SIGSRI] for which it serves as foundation.¶
This document has no IANA actions.¶
TODO acknowledge.¶