HTTP Unencoded Digest
draft-ietf-httpbis-unencoded-digest-05

[Ballot comment]
In Section 5:

>  original unencoded representation.  In order to avoid unintended
>  validation failures, care is advised when selecting content codings
>  for use with Unencoded-Digest; that said, most registered content
>  codings do provide byte-for-byte equivalence and are appropriate.

The important bit is that this consideration is surfaced to the reader (which this section does). However, Section 5 seems to go out of its way to politely permit the implementor to shoot themselves in the foot if they so choose after carefully explaining why they shouldn't. I suggest adding a normative SHOULD here ("When selecting content codings, implementations SHOULD use those with byte-to-byte equivalence to avoid...") seeing as how this is exactly a situation where the implementor has a choice and the authors wish to explain why there's a more correct choice that otherwise has negative consequences.

I support the other normative commentary from the COMMENT sections from Mahesh and Deb. Like Deb, I don't think a DISCUSS is warranted, but I am hoping the next revision addressing Mahesh's DISCUSS will also significantly clean up the approach to normative requirements in what otherwise looks like a solid document.

Minor nit in Section 6: s/"following by an LF"/"followed by an LF"/

[Ballot comment]
Thank you for this clear and concise document.

In section 6, one minor suggestion is to update the description of the response in the second example.

OLD
The server responds with a 206 (Partial Content) response using GZIP content coding, it has three different Integrity fields.

NEW
The server responds with a 206 (Partial Content) response using GZIP content coding and containing three different Integrity fields.

[Ballot discuss]
This particular DISCUSS should be easy to address.

Section 2, paragraph 1
>    This document uses the Augmented BNF defined in [RFC5234] and updated
>    by [RFC7405].  This includes the rules: LF (line feed)

RFC 5234 and RFC 7405 are listed as normative references, yet no ABNF grammar is defined anywhere in this document. It appears that these RFCs are being cited for defining the meaning of "LF". The authors should either remove RFC 5234 and RFC 7405 as normative references and rephrase the LF reference inline (e.g., "followed by a line feed (0xA)"), or confirm what normative ABNF use this document makes justify retaining the two RFCs as normative references.

[Ballot comment]
Section 1, paragraph 5
>    For a variety of reasons, decoding and re-encoding content in order
>    to benefit from HTTP integrity fields is not preferable.  This
>    specification defines the Unencoded-Digest and Want-Unencoded-Digest
>    fields to support a simpler validation workflow in some scenarios
>    where content coding is applied.  These fields complement the other
>    integrity fields defined in [DIGEST-FIELDS].

There is an implicit assumption that this draft does not state explicitly, i.e.,
the server must know the digest of the complete unencoded resource before it
sends the first chunk. That means:

- The server cannot compute Unencoded-Digest on-the-fly as it streams/encodes data.
- It must either have pre-computed the digest and stored it, or buffer the entire unencoded content first, hash it, then start sending.

This is actually a non-trivial constraint that the draft glosses over.
RFC 9530 discusses the streaming vs. pre-computation trade-off for Repr-Digest in
Section 6.1 ("Digest and Content-Encoding"), but this document just says
Unencoded-Digest "behaves similarly to Repr-Digest" and leaves it at that.

This draft should explicitly note that Unencoded-Digest cannot be computed
lazily during transmission, and requires the server to have prior knowledge
of the digest of the complete unencoded representation — either from storage
or pre-computation. This is a meaningful deployment consideration for servers
handling large objects or dynamically generated content, and it belongs to either
in Section 3 or Section 5.

Section 4, paragraph 5
>    *  value is an Integer (Section 3.3.1 of [STRUCTURED-FIELDS]) that
>      conveys an ascending, relative, weighted preference.  It must be
>      in the range 0 to 10 inclusive. 1 is the least preferred, 10 is
>      the most preferred, and a value of 0 means "not acceptable".

This section uses lowercase "must," leaving the normative force ambiguous. RFC 9530 Section 4 uses the
same lowercase "must" for Want-Repr-Digest, so this is consistent with the parent document.
Nevertheless, if senders generating out-of-range values would cause interoperability failures,
this should be "MUST". A brief clarifying note (e.g., whether the Structured Fields Integer
type already enforces this, which would make the normative level moot) would help.

Section 7, paragraph 2
>    A content coding may provide encryption capabilities, for example
>    "aes128gcm" ([RFC8188]).  Using Unencoded-Digest with such content
>    codings can leak information about the original data because header
>    fields are visible to anyone who can read the HTTP message.  This
>    could be used as a side channel.  For instance, an attacker that can
>    access Unencoded-Digest values could infer details about the
>    unencrypted content without decrypting it if, for example, the
>    unencrypted content has a predictable pattern.  When the "aes128gcm"
>    content coding is used, the security considerations in Section 4 of
>    [RFC8188] apply.

I support Deb's comment on the use of a SHOULD NOT for combining Unencoded-Digest with encryption-capable content codings.

In addition, agree with Mallory on changing 'may' to 'might'. This is an informative "may" (describing a possibility,
not a permission), but it sits in a section full of normative language and could be misread. Changing to "might" aligns with RFC 8174 guidance might, and reduces ambiguity.

[Ballot comment]
I ballot no objection.

* My only comment is that I do not like the mixture of [RFC1234] and [LIST] names for references.  I prefer to that you select one style or the other.

[Ballot comment]
Thanks to Rifaat Shekh-Yusef for their secdir reviews.

Please note that while I am balloting 'no obj', I do feel like some minor tweaks make sense.  I am happy to have a conversation (in avoidance of the 'd' word).

Section 7, para 2:  I expected a 'SHOULD NOT' use an Unencoded-Digest in this circumstance.

Section 7, para 2:  I'm not sure I would call the inference of 'details about the unencrypted content with out decrypting it' a 'side channel' per se. Most commonly, we talk about side channels leaking key, not leaking plain text.  With no loss of clarity, I would suggest merely deleting this sentence:  'This could be used as a side channel'.  Notes:  I would hope that any digest algorithm used in this capacity was strong enough to obscure whatever structure was in the plain text.  I would also hope that in this circumstance, an Unencoded-Digest field would not be utilized.

[Ballot comment]
Thanks for the work done in this document, while simple it seems useful.

BUT, please add a normative reference to RFC 8792.

Cosmetic nit: s/This includes the rule*s*: LF (line feed)/This includes the rules: LF (line feed)*.*/ (or something bigger is missing).

Regards

-éric

[Ballot comment]
Hi Lucas and Mike,

Thank you for the effort put into this specification.

The text includes adequate provisions for local policies to better control the handling of the digests.

Please find below some few comments:

# Broken link

CURRENT:
  Source for this draft and an issue tracker can be found at
  https://github.com/httpwg/http-extensions/labels/unecoded-digest.

# Update definitions, not terms

OLD:
  This document updates the terms "Integrity fields" and "Integrity
  preference fields" defined in RFC 9530.


NEW:
  This document updates the definitions of terms "Integrity fields" and "Integrity preference
  fields" defined in RFC 9530.


OLD:
  This document updates the term "Integrity fields" defined in
  [DIGEST-FIELDS] to also include the Unencoded-Digest field,

NEW:
  This document updates the definition of term "Integrity fields" defined in
  [DIGEST-FIELDS] to also include the Unencoded-Digest field,

# Folding

CURRENT:
  This document uses the line folding strategies described in
  [FOLDING].

This is used only for examples. I would move [FOLDING] from Normative to Informative.

# Ease future referencing to the updated definitions

Maybe consider adding entries in Section 2:

NEW:
"Integrity fields" is the collective term for Content-Digest, Repr-Digest, and Unencoded-Digest.

"Integrity preference fields" is the collective term for Want-Repr-Digest, Want-Content-Digest, and Want-Unencoded-Digest.

# Section 3

CURRENT:
  A sender MAY send a digest if it
  knows the recipient will ignore it.

Consider adding an example to illustrate how it knows that.

# Section 4

## Maybe

OLD: must be in the range 0 to 10 inclusive.

NEW: MUST be in the range 0 to 10 inclusive.

## Examples of valid values

OLD:
  Examples:

NEW:
  Examples of valid Want-Unencoded-Digest values are:

Cheers,
Med

IESG/Authors/WG Chairs:

IANA has completed its review of draft-ietf-httpbis-unencoded-digest-03. If any part of this review is inaccurate, please let us know.

IANA understands that, upon approval of this document, there is a single action which we must complete.

In the Hypertext Transfer Protocol (HTTP) Field Name Registry located at:

https://www.iana.org/assignments/http-fields/

two new registrations will be made as follows:

Field Name: Unencoded-Digest
Status: permanent
Structured Type: Dictionary
Reference: [ RFC-to-be; Section 3 ]
Comments:

Field Name: Want-Unencoded-Digest
Status: permanent
Structured Type: Dictionary
Reference: [ RFC-to-be; Section 4 ]
Comments:

As this document requests registrations in an Expert Review or Specification Required (see RFC 8126) registry, we will initiate the required Expert Review via a separate request. This review must be completed before the document's IANA state can be changed to "IANA OK."

We understand that this is the only action required to be completed upon approval of this document.

NOTE: The action requested in this document will not be completed until the document has been approved for publication as an RFC. This message is meant only to confirm the action that will be performed.

For definitions of IANA review states, please see:

https://datatracker.ietf.org/help/state/draft/iana-review

Thank you,

David Dong
IANA Services Sr. Specialist

The following Last Call announcement was sent out (ends 2026-01-14):

From: The IESG
To: IETF-Announce
CC: draft-ietf-httpbis-unencoded-digest@ietf.org, httpbis-chairs@ietf.org, ietf-http-wg@w3.org, mbishop@evequefou.be, mnot@mnot.net
Reply-To: last-call@ietf.org
Sender:
Subject: Last Call:  (HTTP Unencoded Digest) to Proposed Standard


The IESG has received a request from the HTTP WG (httpbis) to consider the
following document: - 'HTTP Unencoded Digest'
  as Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits final
comments on this action. Please send substantive comments to the
last-call@ietf.org mailing lists by 2026-01-14. Exceptionally, comments may
be sent to iesg@ietf.org instead. In either case, please retain the beginning
of the Subject line to allow automated sorting.

Abstract


  The Repr-Digest and Content-Digest integrity fields are subject to
  HTTP content coding considerations.  There are some use cases that
  benefit from the unambiguous exchange of integrity digests of
  unencoded representation.  The Unencoded-Digest and Want-Unencoded-
  Digest fields complement existing integrity fields for this purpose.

  This document updates the terms "Integrity fields" and "Integrity
  preference fields" defined in RFC 9530.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-httpbis-unencoded-digest/



No IPR declarations have been submitted directly on this I-D.

# Document Shepherd Write-Up for Group Documents

*This version is dated 4 July 2022.*

Thank you for your service as a document shepherd. Among the responsibilities is
answering the questions in this write-up to give helpful context to Last Call
and Internet Engineering Steering Group ([IESG][1]) reviewers, and your
diligence in completing it is appreciated. The full role of the shepherd is
further described in [RFC 4858][2]. You will need the cooperation of the authors
and editors to complete these checks.

Note that some numbered items contain multiple related questions; please be sure
to answer all of them.

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?

There was quiet but broad agreement to adopt, followed by regular check-ins and contributions, but the authors were most active. This is to be expected given that this is a "boring" but important exercise in creating a protocol element to fill a necessary hole.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

No.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize the areas of conflict in separate email messages to the
  responsible Area Director. (It should be in a separate email because this
  questionnaire is publicly available.)

No.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?

No significant implementation but there are applicable use cases.

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.

No.

6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

N/A beyond the normal HTTP-focused reviews.

7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] for syntax and
  formatting validation? If there are any resulting errors or warnings, what is
  the justification for not fixing them at this time? Does the YANG module
  comply with the Network Management Datastore Architecture (NMDA) as specified
  in [RFC 8342][5]?

No YANG here (yet).

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.

N/A

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?

Yes.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?

None appear immediately applicable.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

Standards Track, to match the status of companion / similar documents.

12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

Yes; these are experienced contributors and they have been notified.

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

Yes.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

Covered below.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

All look good.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?

N/A

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

RFC8792 is already in the downref registry.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

N/A

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

Updates 9530, correctly in the metadata and discussed in the Introduction.

20. Describe the document shepherd's review of the IANA considerations section,
    especially with regard to its consistency with the body of the document.
    Confirm that all aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

Two straightforward HTTP field registrations.

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

N/A.

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://wiki.ietf.org/group/ops/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://wiki.ietf.org/group/iesg/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/

# Document Shepherd Write-Up for Group Documents

*This version is dated 4 July 2022.*

Thank you for your service as a document shepherd. Among the responsibilities is
answering the questions in this write-up to give helpful context to Last Call
and Internet Engineering Steering Group ([IESG][1]) reviewers, and your
diligence in completing it is appreciated. The full role of the shepherd is
further described in [RFC 4858][2]. You will need the cooperation of the authors
and editors to complete these checks.

Note that some numbered items contain multiple related questions; please be sure
to answer all of them.

## Document History

1. Does the working group (WG) consensus represent the strong concurrence of a
  few individuals, with others being silent, or did it reach broad agreement?

There was quiet but broad agreement to adopt, followed by regular check-ins and contributions, but the authors were most active. This is to be expected given that this is a "boring" but important exercise in creating a protocol element to fill a necessary hole.

2. Was there controversy about particular points, or were there decisions where
  the consensus was particularly rough?

No.

3. Has anyone threatened an appeal or otherwise indicated extreme discontent? If
  so, please summarize the areas of conflict in separate email messages to the
  responsible Area Director. (It should be in a separate email because this
  questionnaire is publicly available.)

No.

4. For protocol documents, are there existing implementations of the contents of
  the document? Have a significant number of potential implementers indicated
  plans to implement? Are any existing implementations reported somewhere,
  either in the document itself (as [RFC 7942][3] recommends) or elsewhere
  (where)?

No significant implementation but there are applicable use cases.

## Additional Reviews

5. Do the contents of this document closely interact with technologies in other
  IETF working groups or external organizations, and would it therefore benefit
  from their review? Have those reviews occurred? If yes, describe which
  reviews took place.

No.

6. Describe how the document meets any required formal expert review criteria,
  such as the MIB Doctor, YANG Doctor, media type, and URI type reviews.

N/A beyond the normal HTTP-focused reviews.

7. If the document contains a YANG module, has the final version of the module
  been checked with any of the [recommended validation tools][4] for syntax and
  formatting validation? If there are any resulting errors or warnings, what is
  the justification for not fixing them at this time? Does the YANG module
  comply with the Network Management Datastore Architecture (NMDA) as specified
  in [RFC 8342][5]?

No YANG here (yet).

8. Describe reviews and automated checks performed to validate sections of the
  final version of the document written in a formal language, such as XML code,
  BNF rules, MIB definitions, CBOR's CDDL, etc.

N/A

## Document Shepherd Checks

9. Based on the shepherd's review of the document, is it their opinion that this
  document is needed, clearly written, complete, correctly designed, and ready
  to be handed off to the responsible Area Director?

Yes.

10. Several IETF Areas have assembled [lists of common issues that their
    reviewers encounter][6]. For which areas have such issues been identified
    and addressed? For which does this still need to happen in subsequent
    reviews?

None appear immediately applicable.

11. What type of RFC publication is being requested on the IETF stream ([Best
    Current Practice][12], [Proposed Standard, Internet Standard][13],
    [Informational, Experimental or Historic][14])? Why is this the proper type
    of RFC? Do all Datatracker state attributes correctly reflect this intent?

Standards Track, to match the status of companion / similar documents.

12. Have reasonable efforts been made to remind all authors of the intellectual
    property rights (IPR) disclosure obligations described in [BCP 79][7]? To
    the best of your knowledge, have all required disclosures been filed? If
    not, explain why. If yes, summarize any relevant discussion, including links
    to publicly-available messages when applicable.

Yes; these are experienced contributors and they have been notified.

13. Has each author, editor, and contributor shown their willingness to be
    listed as such? If the total number of authors and editors on the front page
    is greater than five, please provide a justification.

Yes.

14. Document any remaining I-D nits in this document. Simply running the [idnits
    tool][8] is not enough; please review the ["Content Guidelines" on
    authors.ietf.org][15]. (Also note that the current idnits tool generates
    some incorrect warnings; a rewrite is underway.)

Covered below.

15. Should any informative references be normative or vice-versa? See the [IESG
    Statement on Normative and Informative References][16].

All look good.

16. List any normative references that are not freely available to anyone. Did
    the community have sufficient access to review any such normative
    references?

N/A

17. Are there any normative downward references (see [RFC 3967][9] and [BCP
    97][10]) that are not already listed in the [DOWNREF registry][17]? If so,
    list them.

RFC8792 is already in the downref registry.

18. Are there normative references to documents that are not ready to be
    submitted to the IESG for publication or are otherwise in an unclear state?
    If so, what is the plan for their completion?

N/A

19. Will publication of this document change the status of any existing RFCs? If
    so, does the Datatracker metadata correctly reflect this and are those RFCs
    listed on the title page, in the abstract, and discussed in the
    introduction? If not, explain why and point to the part of the document
    where the relationship of this document to these other RFCs is discussed.

Updates 9530, correctly in the metadata and discussed in the Introduction.

20. Describe the document shepherd's review of the IANA considerations section,
    especially with regard to its consistency with the body of the document.
    Confirm that all aspects of the document requiring IANA assignments are
    associated with the appropriate reservations in IANA registries. Confirm
    that any referenced IANA registries have been clearly identified. Confirm
    that each newly created IANA registry specifies its initial contents,
    allocations procedures, and a reasonable name (see [RFC 8126][11]).

Two straightforward HTTP field registrations.

21. List any new IANA registries that require Designated Expert Review for
    future allocations. Are the instructions to the Designated Expert clear?
    Please include suggestions of designated experts, if appropriate.

N/A.

[1]: https://www.ietf.org/about/groups/iesg/
[2]: https://www.rfc-editor.org/rfc/rfc4858.html
[3]: https://www.rfc-editor.org/rfc/rfc7942.html
[4]: https://wiki.ietf.org/group/ops/yang-review-tools
[5]: https://www.rfc-editor.org/rfc/rfc8342.html
[6]: https://wiki.ietf.org/group/iesg/ExpertTopics
[7]: https://www.rfc-editor.org/info/bcp79
[8]: https://www.ietf.org/tools/idnits/
[9]: https://www.rfc-editor.org/rfc/rfc3967.html
[10]: https://www.rfc-editor.org/info/bcp97
[11]: https://www.rfc-editor.org/rfc/rfc8126.html
[12]: https://www.rfc-editor.org/rfc/rfc2026.html#section-5
[13]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.1
[14]: https://www.rfc-editor.org/rfc/rfc2026.html#section-4.2
[15]: https://authors.ietf.org/en/content-guidelines-overview
[16]: https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
[17]: https://datatracker.ietf.org/doc/downref/