From: Junio C Hamano Date: Fri, 09 Jan 2015 22:39:33 GMT Subject: Re: [RFC/PATCH] receive-pack.c: only accept push-cert if push_cert_nonce was advertised Message-ID: In-Reply-To: <1420836437-11068-1-git-send-email-sbeller@google.com> Stefan Beller writes: > If the server did not advertise the capability to have signed pushes > it should not accept signed pushes as stated in > Documentation/technical/protocol-capabilities.txt: > > Client will then send a space separated list of capabilities it wants > to be in effect. The client MUST NOT ask for capabilities the server > did not say it supports. > > Server MUST diagnose and abort if capabilities it does not understand > was sent. Server MUST NOT ignore capabilities that client requested > and server advertised. As a consequence of these rules, server MUST > NOT advertise capabilities it does not understand. > > After rereading the second paragraph I think they should also be reworded to > > Server MUST diagnose and abort if capabilities it did not advertise > was sent. Except for s/was sent/was requested/, I think that rule makes sense very much. > diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c > index 4c069c5..628d13a 100644 > --- a/builtin/receive-pack.c > +++ b/builtin/receive-pack.c > @@ -1276,7 +1276,8 @@ static struct command *read_head_info(struct sha1_array *shallow) > use_atomic = 1; > } > > - if (!strcmp(line, "push-cert")) { > + if (push_cert_nonce && > + !strcmp(line, "push-cert")) { > int true_flush = 0; > char certbuf[1024]; This implementation is somewhat questionable. The server knows how to parse "push-cert" line, knows that what follows after that line up to "push-cert-end" line are shaped very differently from protocol commands outside the push-cert block. In other words, it knows how to parse the request meant for the capable server; it just wants to refuse to serve that request. The patched code will make it fail by hoping that queue_command() that only handles "40-hex 40-hex ref" will reject the line that begins with "push-cert". Instead of relying on such a hidden dependency, wouldn't it be cleaner to actually parse the push-cert block and then at the end notice and explictly say "Your requests were syntactically correct, but I am not going to honor your request to use the push-cert extension, because I never told you that I'd offer you that capability", instead of rejecting the request with "I was expecting old/new/ref but you sent a line with 'push-cert' on it; what are you talking about?"