Re: [Technical Errata Reported] RFC9530 (8890)

Hi Marius,

On Sat, 25 Apr 2026 at 23:34, RFC Errata System
<rfc-editor@rfc-editor.org> wrote:
>
> The following errata report has been submitted for RFC9530,
> "Digest Fields".
>
> --------------------------------------
> You may review the report below and at:
> https://www.rfc-editor.org/errata/eid8890
>
> --------------------------------------
> Type: Technical
> Reported by: Marius Kleidl <ietf@mariuskleidl.net>
>
> Section: B.4.
>
> Original Text
> -------------
> 8B 08 80 7B 22 68 65 6C 6C 6F
> 22 3A 20 22 77 6F 72 6C 64 22
> 7D 0A 03
>
> Corrected Text
> --------------
> 0B 09 80 7B 22 68 65 6C 6C 6F
> 22 3A 20 22 77 6F 72 6C 64 22
> 7D 0A 03

IIRC we used Python's brotli implementation
>>> brotli.compress(b'{"hello":"world"}')
that returns:

0B 08 80 7B 22 ..

so probably 8B -> 0B is an actual typo.

>
> Notes
> -----
> The Brotli representation provided in the examples in B.4 (Figure 18) and B.6 (Figure 21) aren't valid. Trying to decompress them via Node.js' zlib package and the brotli CLI fails:
>
> ```
> $ node -e "require('zlib').brotliDecompressSync(Buffer.from('8b08807b2268656c6c6f223a2022776f726c64227d0a03','hex'))"
> node:zlib:432
>       throw self[kError];
>       ^
>
> Error: unexpected end of file
>   [...]
>   code: 'Z_BUF_ERROR'
> }
> ```
>
> ```
> $ echo 8b08807b2268656c6c6f223a2022776f726c64227d0a03 | xxd -r -p | brotli -d -c
> corrupt input [con]
> ```
>
> In addition, the SHA-256 over the bytes in the original text is MklYnI/SsUF/5X7enJ2TU+DFjodRObdKLFaPPLe/Kcw=, not d435Qo+nKZ+gLcUHn7GQtQ72hiBVAgqoLsZnZPiTGPk= as used by the RFC in the Repr-Digest header field. The SHA-512 digest in Figure 21 is similarly incorrect.
>

While I think it's OK to update the examples to match the brotli C
implementation,
I am not sure it's an actual erratum, and I will wait for feedback
by the WG.

> The correct text only differs in the first two bytes. With this change, the response content is a valid Brotli compression of `{"hello": "world"}\n`. The SHA-256 and SHA-512 digests in the Repr-Digest header fields then also match the representation's digests.
>
> Instructions:
> -------------
> This erratum is currently posted as "Reported". (If it is spam, it
> will be removed shortly by the RFC Production Center.) Please
> use "Reply All" to discuss whether it should be verified or
> rejected. When a decision is reached, the verifying party
> will log in to change the status and edit the report, if necessary.
>
> --------------------------------------
> RFC9530 (draft-ietf-httpbis-digest-headers-13)
> --------------------------------------
> Title               : Digest Fields
> Publication Date    : February 2024
> Author(s)           : R. Polli, L. Pardue
> Category            : PROPOSED STANDARD
> Source              : HTTP
> Stream              : IETF
> Verifying Party     : IESG

Received on Monday, 27 April 2026 10:28:28 UTC