Discard responses with more than one Via

This is not a perfect solution as headers that are joined via commas are not
detected. This is a parsing issue that to fix "correctly" would necessitate 
a new SIP parser.

Review: https://reviewboard.asterisk.org/r/1019/


git-svn-id: http://svn.digium.com/svn/asterisk/branches/1.4@295628 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 19 insertions, 3 deletions

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index e5a97ae3d..a06726bd6 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -16788,6 +16788,9 @@ static int handle_request(struct sip_pvt *p, struct sip_request *req, struct soc
 	const char *cmd;
 	const char *cseq;
 	const char *useragent;
+	const char *via;
+	const char *callid;
+	int via_pos = 0;
 	int seqno;
 	int len;
 	int ignore = FALSE;
@@ -16799,13 +16802,19 @@ static int handle_request(struct sip_pvt *p, struct sip_request *req, struct soc
 	int oldmethod = p->method;
 	int acked = 0;
 
-	/* Get Method and Cseq */
+	/* RFC 3261 - 8.1.1 A valid SIP request must contain To, From, CSeq, Call-ID and Via.
+	 * 8.2.6.2 Response must have To, From, Call-ID CSeq, and Via related to the request,
+	 * so we can check to make sure these fields exist for all requests and responses */
 	cseq = get_header(req, "Cseq");
 	cmd = req->header[0];
+	/* Save the via_pos so we can check later that responses only have 1 Via header */
+	via = __get_header(req, "Via", &via_pos);
+	/* This must exist already because we've called find_call by now */
+	callid = get_header(req, "Call-ID");
 
 	/* Must have Cseq */
-	if (ast_strlen_zero(cmd) || ast_strlen_zero(cseq)) {
-		ast_log(LOG_ERROR, "Missing Cseq. Dropping this SIP message, it's incomplete.\n");
+	if (ast_strlen_zero(cmd) || ast_strlen_zero(cseq) || ast_strlen_zero(via)) {
+		ast_log(LOG_ERROR, "Dropping this SIP message with Call-ID '%s', it's incomplete.\n", callid);
 		error = 1;
 	}
 	if (!error && sscanf(cseq, "%30d%n", &seqno, &len) != 1) {
@@ -16841,6 +16850,13 @@ static int handle_request(struct sip_pvt *p, struct sip_request *req, struct soc
 			ast_log(LOG_WARNING, "Invalid SIP response code: '%d'\n", respid);
 			return 0;
 		}
+		/* RFC 3261 - 8.1.3.3 If more than one Via header field value is present in a reponse
+		 * the UAC SHOULD discard the message. This is not perfect, as it will not catch multiple
+		 * headers joined with a comma. Fixing that would pretty much involve writing a new parser */
+		if (!ast_strlen_zero(__get_header(req, "via", &via_pos))) {
+			ast_log(LOG_WARNING, "Misrouted SIP response '%s' with Call-ID '%s', too many vias\n", e, callid);
+			return 0;
+		}
 		if (!p->initreq.headers) {
 			if (option_debug)
 				ast_log(LOG_DEBUG, "That's odd...  Got a response on a call we don't know about. Cseq %d Cmd %s\n", seqno, cmd);