Subject: draft-ietf-httpbis-digest-headers: Digests and Conditional Requests

From: Julian Reschke <[email-masked]>
Date: Tue, 30 Jun 2020 11:22:44 +0200

Hi there,

I just noticed that RFC 4918 (WebDAV) and RFC 6920 (Naming Things with
Hashes) give us the machinery to make request conditional on hashes.

Example (based on
<https://greenbytes.de/tech/webdav/draft-ietf-httpbis-digest-headers-02.html#server-returns-full-representation-data>)

   PUT /x HTTP/1.1
   Host: foo
   If: <ni:///sha-256;X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=>
   Content-Type: application/json

   {"hello": "world2"}

All that would be needed is s statement that servers that support both
the Digest field and the If header field SHOULD consider the ni: URIs
built from the hashes as "state tokens" as defined in RFC 4918, Section 3.

Best regards, Julian

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From: Roberto Polli <[email-masked]>
Date: Tue, 30 Jun 2020 18:03:25 +0200

Hi Julian,

thanks for this feedback!
I am reading RFC 6920 but I don't find many details on representation
metadata and partial representation
(only `ct` - content-type is defined).

It would be interesting to understand how to tie "ni:///$HASH" with
the other digest-algorithms in a way that it is respectful of RFC3230,
eg. see https://github.com/httpwg/http-extensions/pull/1213

When  I finish reading rfc 6920 I'll provide more feedback.

Thanks again,
R.

---

From: Julian Reschke <[email-masked]>
Date: Tue, 30 Jun 2020 18:31:37 +0200

On 30.06.2020 18:03, Roberto Polli wrote:
> ...

Do we have any evidence of use of parameters for digest algorithms?

Best regards, Julian