From: Christopher Zimmermann <chrisz@openbsd.org>
Subject: relayd: Keep Content-Length in response to HEAD request
To: millert@openbsd.org, tech@openbsd.org
Date: Sat, 29 Jun 2024 19:16:36 +0200

Hi,

responses to HEAD requests SHOULD return the same headers a GET request 
would yield (https://www.rfc-editor.org/rfc/rfc9110.html#section-9.3.2).

Therefore the Content-Length header should not be stripped from 
responses to HEAD requests.

This bit me when relaying traffic between restic and a 
restic-rest-server. Restic gets confused by the missing Content-Length: 
header and complains about a "negative content length" when checking for 
the presence of /config.

OK?


Christopher


Index: relay_http.c
===================================================================
RCS file: /cvs/src/usr.sbin/relayd/relay_http.c,v
retrieving revision 1.87
diff -u -p -r1.87 relay_http.c
--- relay_http.c        1 Dec 2023 16:48:40 -0000       1.87
+++ relay_http.c        29 Jun 2024 17:02:44 -0000
@@ -435,18 +435,6 @@ relay_read_http(struct bufferevent *bev,
                                         kv_delete(&desc->http_headers,
                                             desc->http_lastheader);
                                         break;
-                               case HTTP_METHOD_RESPONSE:
-                                       /*
-                                        * Strip Content-Length header from
-                                        * HEAD responses since there is no
-                                        * actual payload in the response.
-                                        */
-                                       if (request_method == HTTP_METHOD_HEAD) {
-                                               kv_delete(&desc->http_headers,
-                                                   desc->http_lastheader);
-                                               break;
-                                       }
-                                       /* FALLTHROUGH */
                                 default:
                                         /*
                                          * Need to read data from the client