[PATCH 5/8] mgcp: NUL-terminate MGCP message

[Jacob Erlbeck]

The MGCP message isn't always NUL-terminated when arriving at
mgcp_handle_message(). This may lead to undefined results.

This patch ensures that the message text is NUL-terminated by
setting *msg->tail to '\0' in mgcp_handle_message().

Addresses:
<000b> mgcp_protocol.c:642 Unhandled option: 'r'/114 on 0x3
<000b> mgcp_protocol.c:593 Unhandled SDP option: '='/61 on 0x3
<000b> mgcp_protocol.c:871 Unhandled option: '.'/46 on 0x2

Sponsored-by: On-Waves ehf
---
 openbsc/src/libmgcp/mgcp_protocol.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/openbsc/src/libmgcp/mgcp_protocol.c b/openbsc/src/libmgcp/mgcp_protocol.c
index d4a23a7..44c93f7 100644
--- a/openbsc/src/libmgcp/mgcp_protocol.c
+++ b/openbsc/src/libmgcp/mgcp_protocol.c
@@ -262,6 +262,18 @@ struct msgb *mgcp_handle_message(struct mgcp_config *cfg, struct msgb *msg)
 	struct msgb *resp = NULL;
 	char *data;
 
+	/* Ensure that the msg->l2h is NULL terminated. */
+	if (msgb_tailroom(msg) > 0)
+		*msg->tail = '\0';
+	else if (*(msg->tail-1) == '\r' || *(msg->tail-1) == '\n')
+		*(msg->tail - 1) = '\0';
+	else {
+		LOGP(DMGCP, LOGL_ERROR, "Cannot NUL terminate MGCP message: "
+		     "Length: %d, Buffer size: %d\n",
+		     msgb_l2len(msg), msg->data_len);
+		return NULL;
+	}
+
 	if (msgb_l2len(msg) < 4) {
 		LOGP(DMGCP, LOGL_ERROR, "msg too short: %d\n", msg->len);
 		return NULL;
@@ -278,7 +290,6 @@ struct msgb *mgcp_handle_message(struct mgcp_config *cfg, struct msgb *msg)
 
 	/*
 	 * Check for a duplicate message and respond.
-	 * FIXME: Verify that the msg->l3h is NULL terminated.
 	 */
 	memset(&pdata, 0, sizeof(pdata));
 	pdata.cfg = cfg;
-- 
1.7.9.5