Changeset 3325 for pjproject/trunk/pjmedia/src/pjmedia/rtp.c

Timestamp:

Sep 28, 2010 8:26:51 AM (14 years ago)

Author:

nanang

Message:

Fix #1135: added RTP padding checks and RTP payload length adjustment according to padding length.

Payload padding in outgoing RTP investigation results:

• the RTP does not specify RTP payload alignment.
• most codecs also do not specify RTP payload alignment, usually only octet-alignment is specified and this seems to be done.
• SRTP, RFC3711 states:
  • None of the pre-defined SRTP encryption transforms uses any padding; for these, the RTP and SRTP payload sizes match exactly.
  • Message authentication codes define their own padding.
  • Encryption transforms that use padding are vulnerable to subtle attacks, especially when message authentication is not used.

So, currently payload padding in outgoing RTP is not necessary.

File:

• pjproject/trunk/pjmedia/src/pjmedia/rtp.c (modified) (1 diff)

pjproject/trunk/pjmedia/src/pjmedia/rtp.c

@@ -181 +181 @@
     *payload = ((pj_uint8_t*)pkt) + offset;
     *payloadlen = pkt_len - offset;
+ 
+    /* Remove payload padding if any */
+    if ((*hdr)->p && *payloadlen > 0) {
+        pj_uint8_t pad_len;
+
+        pad_len = ((pj_uint8_t*)(*payload))[*payloadlen - 1];
+        if (pad_len <= *payloadlen)
+            *payloadlen -= pad_len;
+    }
 
     return PJ_SUCCESS;