RFC 8555, "Automatic Certificate Management Environment (ACME)", March 2019

Errata ID: 6030
Status: Reported
Type: Technical
Publication Format(s) : TEXT
Reported By: Matt Palmer
Date Reported: 2020-03-25

Section 7.2 says:

To get a fresh nonce, the client sends a HEAD request to the newNonce
resource on the server.  The server's response MUST include a Replay-
Nonce header field containing a fresh nonce and SHOULD have status
code 200 (OK).  The server MUST also respond to GET requests for this
resource, returning an empty body (while still providing a Replay-
Nonce header) with a status code of 204 (No Content).

It should say:

To get a fresh nonce, the client sends a HEAD request to the newNonce
resource on the server.  The server's response MUST include a Replay-
Nonce header field containing a fresh nonce and SHOULD have status
code 204 (No Content).  The server MUST also respond to GET requests for this
resource, returning an empty body (while still providing a Replay-
Nonce header) with a status code of 204 (No Content).

Notes:

RFC7321 s4.3.2, says "The server SHOULD send the same header fields in response to a HEAD request as it would have sent if the request had been a GET". I can't see any rationale for violating this SHOULD in the discussion in the GH issue which introduced the discrepancy in response code between GET and HEAD (https://github.com/ietf-wg-acme/acme/pull/371), thus (IMHO) it violates the tenets of a SHOULD, as "the full implications" do not appear to have "be[en] understood and carefully weighed before choosing a different course" (RFC2119, of course).

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