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

Network Working Group                                          M. Kleidl
Internet-Draft                                               Transloadit
Intended status: Informational                                 L. Pardue
Expires: 9 January 2025                                       Cloudflare
                                                             8 July 2024

                  HTTP Problem Types for Digest Fields
              draft-kleidl-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://tus.github.io/draft-digest-fields-problem-types/draft-kleidl-
   digest-fields-problem-types.html.  Status information for this
   document may be found at https://datatracker.ietf.org/doc/draft-
   kleidl-digest-fields-problem-types/.

   Source for this draft and an issue tracker can be found at
   https://github.com/tus/draft-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/.

   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 9 January 2025.

Kleidl & Pardue          Expires 9 January 2025                 [Page 1]
Internet-Draft    HTTP Problem Types for Digest Fields         July 2024

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  . . . . . . . . . . . . . . . . . .   4
     3.3.  Mismatching Digest Value  . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

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.

   For example, a request message may include content alongside Content-
   Digest and Repr-Digest header 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.

Kleidl & Pardue          Expires 9 January 2025                 [Page 2]
Internet-Draft    HTTP Problem Types for Digest Fields         July 2024

   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#unsupported-hashing-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" are
   from [DIGEST].

3.  Problem Types

3.1.  Unsupported Hashing Algorithm

   This section defines the "https://iana.org/assignments/http-problem-
   types#unsupported-hashing-algorithm" problem type [PROBLEM].  A
   server MAY use this problem type when responding to a request, whose
   integrity or integrity preference fields reference a hashing
   algorithm that the server can not or does not want to support for
   this request, and if the server wants to indicate this problem to the
   sender.

   For this problem type, the 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 SHOULD include
   the corresponding integrity preference field to indicate the server's
   algorithm support and preference.

   The following example shows a response for a request with an
   integrity field utilizing an unsupported hashing algorithm foo.  The
   response also includes a list of supported algorithms.

Kleidl & Pardue          Expires 9 January 2025                 [Page 3]
Internet-Draft    HTTP Problem Types for Digest Fields         July 2024

   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#unsupported-hashing-algorithm",
     "title": "hashing algorithm is not supported",
     "unsupported-algorithm": "foo"
   }

   This problem type is a hint to the client about algorithm support,
   which the client could use to retry the request with a different
   algorithm supported by the server.

3.2.  Invalid Digest Value

   This section defines the "https://iana.org/assignments/http-problem-
   types#invalid-digest-value" problem type [PROBLEM].  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 response for a request with an invalid
   digest value.

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

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

   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.

Kleidl & Pardue          Expires 9 January 2025                 [Page 4]
Internet-Draft    HTTP Problem Types for Digest Fields         July 2024

3.3.  Mismatching Digest Value

   This section defines the "https://iana.org/assignments/http-problem-
   types#mismatching-digest-value" problem type [PROBLEM].  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 response for a request with a
   mismatching SHA-256 digest value.

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

   {
     "type": "https://iana.org/assignments/http-problem-types#mismatching-digest-value",
     "title": "digest value fromr request does not match expected value",
     "algorithm": "sha-256",
     "provided-digest": ":RK/0qy18MlBSVnWgjwz6lZEWjP/lF5HF9bvEF8FabDg=:",
     "calculated-digest": ":d435Qo+nKZ+gLcUHn7GQtQ72hiBVAgqoLsZnZPiTGPk=:"
   }

   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

   Although an error appeared while handling the digest fields, the
   server may choose to not disclose this error to the sender to avoid
   lacking implementation details.  Similar, the server may choose a
   general problem type for the response even in a more specific problem
   type is defined if it prefers to hide the details of the error from
   the sender.

Kleidl & Pardue          Expires 9 January 2025                 [Page 5]
Internet-Draft    HTTP Problem Types for Digest Fields         July 2024

5.  IANA Considerations

   IANA is asked to register the following entry in the "HTTP Problem
   Types" registry:

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

   Title:  Unsupported Hashing Algorithm

   Recommended HTTP status code:  400

   Reference:  This document

   IANA is asked to register the following entry in the "HTTP Problem
   Types" registry:

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

   Title:  Invalid Digest Value

   Recommended HTTP status code:  400

   Reference:  This document

   IANA is asked to register the following entry in the "HTTP Problem
   Types" registry:

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

   Title:  Mismatching Digest Value

   Recommended HTTP status code:  400

   Reference:  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>.

   [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>.

Kleidl & Pardue          Expires 9 January 2025                 [Page 6]
Internet-Draft    HTTP Problem Types for Digest Fields         July 2024

   [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>.

Acknowledgments

   This document is based on ideas from a discussion with Roberto Polli,
   so thanks to him for his valuable input and feedback on this topic.

Authors' Addresses

   Marius Kleidl
   Transloadit
   Email: marius@transloadit.com

   Lucas Pardue
   Cloudflare
   Email: lucas@lucaspardue.com

Kleidl & Pardue          Expires 9 January 2025                 [Page 7]