HTTP Problem Types for Digest Fields
draft-ietf-httpapi-digest-fields-problem-types-00

Building Blocks for HTTP APIs                                  M. Kleidl
Internet-Draft                                               Transloadit
Intended status: Informational                                 L. Pardue
Expires: 8 May 2025                                           Cloudflare
                                                                R. Polli
                                                                 Par-Tec
                                                         4 November 2024

                  HTTP Problem Types for Digest Fields
           draft-ietf-httpapi-digest-fields-problem-types-00

Abstract

   This document specifies problem types that servers can use in
   responses to problems encountered while dealing with a request
   carrying integrity fields and integrity preference fields.

About This Document

   This note is to be removed before publishing as an RFC.

   The latest revision of this draft can be found at https://ietf-wg-
   httpapi.github.io/digest-fields-problem-types/draft-ietf-httpapi-
   digest-fields-problem-types.html.  Status information for this
   document may be found at https://datatracker.ietf.org/doc/draft-ietf-
   httpapi-digest-fields-problem-types/.

   Discussion of this document takes place on the Building Blocks for
   HTTP APIs Working Group mailing list (mailto:httpapi@ietf.org), which
   is archived at https://mailarchive.ietf.org/arch/browse/httpapi/.
   Subscribe at https://www.ietf.org/mailman/listinfo/httpapi/.

   Source for this draft and an issue tracker can be found at
   https://github.com/ietf-wg-httpapi/digest-fields-problem-types.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

Kleidl, et al.             Expires 8 May 2025                   [Page 1]
Internet-Draft    HTTP Problem Types for Digest Fields     November 2024

   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 8 May 2025.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date 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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  Problem Types . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Unsupported Hashing Algorithm . . . . . . . . . . . . . .   3
     3.2.  Invalid Digest Value  . . . . . . . . . . . . . . . . . .   5
     3.3.  Mismatching Digest Value  . . . . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  Registration of "digest-unsupported-algorithm" Problem
           Type  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.2.  Registration of "digest-invalid-value" Problem Type . . .   7
     5.3.  Registration of "digest-mismatching-value" Problem
           Type  . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   [DIGEST] by design does not define, require or recommend any specific
   behavior for error handling relating to integrity.  The
   responsibility is instead delegated to applications.  This draft
   defines a set of problem types ([PROBLEM]) that can be used by server
   applications to indicate that a problem was encountered while dealing
   with a request carrying integrity fields and integrity preference
   fields.

Kleidl, et al.             Expires 8 May 2025                   [Page 2]
Internet-Draft    HTTP Problem Types for Digest Fields     November 2024

   For example, a request message may include content alongside Content-
   Digest and Repr-Digest fields that use a digest algorithm the server
   does not support.  An application could decide to reject this request
   because it cannot validate the integrity.  Using a problem type, the
   server can provide machine-readable error details to aid debugging or
   error reporting, as shown in the following example.

   HTTP/1.1 400 Bad Request
   Content-Type: application/problem+json
   Want-Content-Digest: sha-512=3, sha-256=10

   {
     "type": "https://iana.org/assignments/http-problem-types#digest-unsupported-algorithm",
     "title": "hashing algorithm is not supported",
     "unsupported-algorithm": "foo"
   }

2.  Conventions and Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The terms "integrity fields" and "integrity preference fields" in
   this document are to be interpreted as described in [DIGEST].

   The term "problem type" in this document is to be interpreted as
   described in [PROBLEM].

   The term "request", "response", "intermediary", "sender", and
   "server" are from [HTTP].

3.  Problem Types

3.1.  Unsupported Hashing Algorithm

   This section defines the "https://iana.org/assignments/http-problem-
   types#digest-unsupported-algorithm" problem type.  A server MAY use
   this problem type if it wants to communicate to the client that one
   of the hashing algorithms referenced in the integrity or integrity
   preference fields present in the request is not supported.

Kleidl, et al.             Expires 8 May 2025                   [Page 3]
Internet-Draft    HTTP Problem Types for Digest Fields     November 2024

   For this problem type, unsupported-algorithm is defined as the only
   extension member.  It SHOULD be populated in a response using this
   problem type, with its value being the algorithm key of the
   unsupported algorithm from the request.  The response can include the
   corresponding integrity preference field to indicate the server's
   algorithm support and preference.

   Example:

   POST /books HTTP/1.1
   Host: foo.example
   Content-Type: application/json
   Accept: application/json
   Accept-Encoding: identity
   Repr-Digest: sha-256=:mEkdbO7Srd9LIOegftO0aBX+VPTVz7/CSHes2Z27gc4=:

   {"title": "New Title"}

      Figure 1: A request with a sha-256 integrity field, which is not
                          supported by the server

   HTTP/1.1 400 Bad Request
   Content-Type: application/problem+json
   Want-Repr-Digest: sha-512=10, sha-256=0

   {
     "type": "https://iana.org/assignments/http-problem-types#digest-unsupported-algorithm",
     "title": "Unsupported hashing algorithm",
     "unsupported-algorithm": "sha-256"
   }

          Figure 2: Response Advertising the Supported Algorithms

   This problem type is a hint to the client about algorithm support,
   which the client could use to retry the request with a different,
   supported, algorithm.  Note that a request may contain more than one
   integrity field.

   This problem type can also be used when a request contains an
   integrity preference field.  For example:

   GET /items/123 HTTP/1.1
   Host: foo.example
   Want-Repr-Digest: sha=10

                Figure 3: GET Request with Want-Repr-Digest

Kleidl, et al.             Expires 8 May 2025                   [Page 4]
Internet-Draft    HTTP Problem Types for Digest Fields     November 2024

   HTTP/1.1 400 Bad Request
   Content-Type: application/problem+json

   {
     "type": "https://iana.org/assignments/http-problem-types#digest-unsupported-algorithm",
     "title": "Unsupported hashing algorithm",
     "unsupported-algorithm": "sha"
   }

          Figure 4: Response Advertising the Supported Algorithms

3.2.  Invalid Digest Value

   This section defines the "https://iana.org/assignments/http-problem-
   types#digest-invalid-value" problem type.  A server MAY use this
   problem type when responding to a request, whose integrity fields
   include a digest value, that cannot be generated by the corresponding
   hashing algorithm.  For example, if the digest value of the sha-512
   hashing algorithm is not 64 bytes long, it cannot be a valid digest
   value and the server can skip computing the digest value.  This
   problem type MUST NOT be used if the server is not able to parse the
   integrity fields according to Section 4.5 of [STRUCTURED-FIELDS], for
   example because of a syntax error in the field value.

   The server SHOULD include a human-readable description why the value
   is considered invalid in the title member.

   The following example shows a request with the content {"hello":
   "world"} (plus LF), but the digest has been truncated.  The
   subsequent response indicates the invalid SHA-512 digest.

   PUT /items/123 HTTP/1.1
   Host: foo.example
   Content-Type: application/json
   Repr-Digest: sha-512=:YMAam51Jz/jOATT6/zvHrLVgOYTGFy1d6GJiOHTohq4:

   {"hello": "world"}

      Figure 5: A request with a sha-512 integrity field, whose digest
                             has been truncated

   HTTP/1.1 400 Bad Request
   Content-Type: application/problem+json

   {
     "type": "https://iana.org/assignments/http-problem-types#digest-invalid-value",
     "title": "digest value for sha-512 is not 64 bytes long"
   }

Kleidl, et al.             Expires 8 May 2025                   [Page 5]
Internet-Draft    HTTP Problem Types for Digest Fields     November 2024

    Figure 6: Response indicating that the provided digest is too short

   This problem type indicates a fault in the sender's calculation or
   encoding of the digest value.  A retry of the same request without
   modification will likely not yield a successful response.

3.3.  Mismatching Digest Value

   This section defines the "https://iana.org/assignments/http-problem-
   types#digest-mismatching-value" problem type.  A server MAY use this
   problem type when responding to a request, whose integrity fields
   include a digest value that does not match the digest value that the
   server calculated for the request content or representation.

   Three problem type extension members are defined: the algorithm,
   provided-digest, and calculated-digest members.  A response using
   this problem type SHOULD populate all members, with the value of
   algorithm being the algorithm key of the used hashing algorithm, with
   the value of provided-digest being the digest value taken from the
   request's integrity fields, and the value of calculated-digest being
   the calculated digest.  The digest values MUST BE serialized as byte
   sequences as described in Section 4.1.8 of [STRUCTURED-FIELDS].

   The following example shows a request with the content {"hello":
   "woXYZ"} (plus LF), but the representation digest for {"hello":
   "world"} (plus LF).  The subsequent response indicates the
   mismatching SHA-256 digest values.

   PUT /items/123 HTTP/1.1
   Host: foo.example
   Content-Type: application/json
   Repr-Digest: sha-256=:RK/0qy18MlBSVnWgjwz6lZEWjP/lF5HF9bvEF8FabDg=:

   {"hello": "woXYZ"}

       Figure 7: A request with a sha-256 integrity field, which does
                        not match the representation

   HTTP/1.1 400 Bad Request
   Content-Type: application/problem+json

   {
     "type": "https://iana.org/assignments/http-problem-types#digest-mismatching-value",
     "title": "digest value fromr request does not match expected value",
     "algorithm": "sha-256",
     "provided-digest": ":RK/0qy18MlBSVnWgjwz6lZEWjP/lF5HF9bvEF8FabDg=:",
     "calculated-digest": ":8vXo+0QVwf2woEblm4hTAftp0/K5fWSMZG4CKtplwjc=:"
   }

Kleidl, et al.             Expires 8 May 2025                   [Page 6]
Internet-Draft    HTTP Problem Types for Digest Fields     November 2024

           Figure 8: Response indicating the mismatching digests

   If the sender receives this problem type, the request might be
   modified unintentionally by an intermediary.  The sender could use
   this information to retry the request without modification to address
   temporary transmission issues.

4.  Security Considerations

   Disclosing error details could leak information such as the presence
   of intermediaries or the server's implementation details.  Moreover,
   they can be used to fingerprint the server.

   To mitigate these risks, a server could assess the risk of disclosing
   error details and prefer a general problem type over a more specific
   one.

5.  IANA Considerations

   IANA is asked to register the following entries in the "HTTP Problem
   Types" registry at https://www.iana.org/assignments/http-problem-
   types (https://www.iana.org/assignments/http-problem-types).

5.1.  Registration of "digest-unsupported-algorithm" Problem Type

   Type URI:  https://iana.org/assignments/http-problem-types#digest-
      unsupported-algorithm

   Title:  Unsupported Hashing Algorithm

   Recommended HTTP status code:  400

   Reference:  Section 3.1 of this document

5.2.  Registration of "digest-invalid-value" Problem Type

   Type URI:  https://iana.org/assignments/http-problem-types#digest-
      invalid-value

   Title:  Invalid Digest Value

   Recommended HTTP status code:  400

   Reference:  Section 3.2 of this document

5.3.  Registration of "digest-mismatching-value" Problem Type

   Type URI:  https://iana.org/assignments/http-problem-types#digest-

Kleidl, et al.             Expires 8 May 2025                   [Page 7]
Internet-Draft    HTTP Problem Types for Digest Fields     November 2024

      mismatching-value

   Title:  Mismatching Digest Value

   Recommended HTTP status code:  400

   Reference:  Section 3.3 of this document

6.  Normative References

   [DIGEST]   Polli, R. and L. Pardue, "Digest Fields", RFC 9530,
              DOI 10.17487/RFC9530, February 2024,
              <https://www.rfc-editor.org/rfc/rfc9530>.

   [HTTP]     Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
              Ed., "HTTP Semantics", STD 97, RFC 9110,
              DOI 10.17487/RFC9110, June 2022,
              <https://www.rfc-editor.org/rfc/rfc9110>.

   [PROBLEM]  Nottingham, M., Wilde, E., and S. Dalal, "Problem Details
              for HTTP APIs", RFC 9457, DOI 10.17487/RFC9457, July 2023,
              <https://www.rfc-editor.org/rfc/rfc9457>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

   [STRUCTURED-FIELDS]
              Nottingham, M. and P. Kamp, "Structured Field Values for
              HTTP", RFC 8941, DOI 10.17487/RFC8941, February 2021,
              <https://www.rfc-editor.org/rfc/rfc8941>.

Authors' Addresses

   Marius Kleidl
   Transloadit
   Email: marius@transloadit.com

   Lucas Pardue
   Cloudflare
   Email: lucas@lucaspardue.com

Kleidl, et al.             Expires 8 May 2025                   [Page 8]
Internet-Draft    HTTP Problem Types for Digest Fields     November 2024

   Roberto Polli
   Par-Tec
   Italy
   Email: robipolli@gmail.com

Kleidl, et al.             Expires 8 May 2025                   [Page 9]