rtmppkt: Check for packet size mismatches
authorMichael Niedermayer <michael@niedermayer.cc>
Mon, 5 Dec 2016 10:14:51 +0000 (11:14 +0100)
committerMartin Storsjö <martin@martin.st>
Thu, 15 Dec 2016 13:45:59 +0000 (15:45 +0200)
When receiving fragmented packets, the first packet declares the size,
and the later ones normally are small follow-on packets that don't repeat
the size and the other header fields. But technically, the later fragments
also can have a full header, declaring a different size than the previous
packet.

If the follow-on packet declares a larger size than the initial one, we
could end up writing outside of the allocation.

This fixes out of bounds writes.

Found-by: Paul Cher <paulcher@icloud.com>
Reviewed-by: Paul Cher <paulcher@icloud.com>
CC: libav-stable@libav.org
Signed-off-by: Martin Storsjö <martin@martin.st>
libavformat/rtmppkt.c

index f8c51d0..1cb3078 100644 (file)
@@ -235,6 +235,14 @@ static int rtmp_packet_read_one_chunk(URLContext *h, RTMPPacket *p,
     if (hdr != RTMP_PS_TWELVEBYTES)
         timestamp += prev_pkt[channel_id].timestamp;
 
+    if (prev_pkt[channel_id].read && size != prev_pkt[channel_id].size) {
+        av_log(h, AV_LOG_ERROR, "RTMP packet size mismatch %d != %d\n",
+                                size, prev_pkt[channel_id].size);
+        ff_rtmp_packet_destroy(&prev_pkt[channel_id]);
+        prev_pkt[channel_id].read = 0;
+        return AVERROR_INVALIDDATA;
+    }
+
     if (!prev_pkt[channel_id].read) {
         if ((ret = ff_rtmp_packet_create(p, channel_id, type, timestamp,
                                          size)) < 0)