Exploit-DB #45122
Description: WebRTC - FEC Processing Overflow
Type: dos
Platform: multiple
Date: 2018-08-01
Author: Google Security Research

Exploit:
There are several calls to memcpy that can overflow the destination buffer in webrtc::UlpfecReceiverImpl::AddReceivedRedPacket. The method takes a parameter incoming_rtp_packet, which is an RTP packet with a mac length that is defined by the transport (2048 bytes for DTLS in Chrome). This packet is then copied to the received_packet in several locations in the method, depending on packet properties, using the lenth of the incoming_rtp_packet as the copy length. The received_packet is a ForwardErrorCorrection::ReceivedPacket, which has a max size of 1500. Therefore, the memcpy calls in this method can overflow this buffer.

==204614==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x61b000046670 at pc 0x00000059d958 bp 0x7ffcac5716f0 sp 0x7ffcac570ea0
WRITE of size 2316 at 0x61b000046670 thread T0
    #0 0x59d957 in __asan_memcpy /b/build/slave/linux_upload_clang/build/src/third_party/llvm/compiler-rt/lib/asan/asan_interceptors_memintrinsics.cc:23:3
    #1 0x1b6aacc in webrtc::UlpfecReceiverImpl::AddReceivedRedPacket(webrtc::RTPHeader const&, unsigned char const*, unsigned long, unsigned char) modules/rtp_rtcp/source/ulpfec_receiver_impl.cc:173:5
    #2 0x1b3cd5c in webrtc::RtpVideoStreamReceiver::ParseAndHandleEncapsulatingHeader(unsigned char const*, unsigned long, webrtc::RTPHeader const&) video/rtp_video_stream_receiver.cc:426:27
    #3 0x1b39a31 in webrtc::RtpVideoStreamReceiver::ReceivePacket(unsigned char const*, unsigned long, webrtc::RTPHeader const&) video/rtp_video_stream_receiver.cc:402:5
    #4 0x1b3a895 in webrtc::RtpVideoStreamReceiver::OnRtpPacket(webrtc::RtpPacketReceived const&) video/rtp_video_stream_receiver.cc:301:3
    #5 0x8c7a26 in webrtc::RtpDemuxer::OnRtpPacket(webrtc::RtpPacketReceived const&) call/rtp_demuxer.cc:157:11
    #6 0x8cec3d in webrtc::RtpStreamReceiverController::OnRtpPacket(webrtc::RtpPacketReceived const&) call/rtp_stream_receiver_controller.cc:55:19
    #7 0x12e8507 in webrtc::internal::Call::DeliverRtp(webrtc::MediaType, rtc::CopyOnWriteBuffer, webrtc::PacketTime const&) call/call.cc:1291:36
    #8 0x12e92a0 in webrtc::internal::Call::DeliverPacket(webrtc::MediaType, rtc::CopyOnWriteBuffer, webrtc::PacketTime const&) call/call.cc:1316:10
    #9 0x5da2a6 in webrtc::RtpReplay() video/replay.cc:635:31
    #10 0x5dd5fe in main video/replay.cc:700:3
    #11 0x7feaa1ee92b0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202b0)

0x61b000046670 is located 0 bytes to the right of 1520-byte region [0x61b000046080,0x61b000046670)
allocated by thread T0 here:
    #0 0x5c9362 in operator new(unsigned long) /b/build/slave/linux_upload_clang/build/src/third_party/llvm/compiler-rt/lib/asan/asan_new_delete.cc:93:3
    #1 0x1b6a8c8 in webrtc::UlpfecReceiverImpl::AddReceivedRedPacket(webrtc::RTPHeader const&, unsigned char const*, unsigned long, unsigned char) modules/rtp_rtcp/source/ulpfec_receiver_impl.cc:165:35
    #2 0x1b3cd5c in webrtc::RtpVideoStreamReceiver::ParseAndHandleEncapsulatingHeader(unsigned char const*, unsigned long, webrtc::RTPHeader const&) video/rtp_video_stream_receiver.cc:426:27
    #3 0x1b39a31 in webrtc::RtpVideoStreamReceiver::ReceivePacket(unsigned char const*, unsigned long, webrtc::RTPHeader const&) video/rtp_video_stream_receiver.cc:402:5
    #4 0x1b3a895 in webrtc::RtpVideoStreamReceiver::OnRtpPacket(webrtc::RtpPacketReceived const&) video/rtp_video_stream_receiver.cc:301:3
    #5 0x8c7a26 in webrtc::RtpDemuxer::OnRtpPacket(webrtc::RtpPacketReceived const&) call/rtp_demuxer.cc:157:11
    #6 0x8cec3d in webrtc::RtpStreamReceiverController::OnRtpPacket(webrtc::RtpPacketReceived const&) call/rtp_stream_receiver_controller.cc:55:19
    #7 0x12e8507 in webrtc::internal::Call::DeliverRtp(webrtc::MediaType, rtc::CopyOnWriteBuffer, webrtc::PacketTime const&) call/call.cc:1291:36
    #8 0x12e92a0 in webrtc::internal::Call::DeliverPacket(webrtc::MediaType, rtc::CopyOnWriteBuffer, webrtc::PacketTime const&) call/call.cc:1316:10
    #9 0x5da2a6 in webrtc::RtpReplay() video/replay.cc:635:31
    #10 0x5dd5fe in main video/replay.cc:700:3
    #11 0x7feaa1ee92b0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202b0)

SUMMARY: AddressSanitizer: heap-buffer-overflow /b/build/slave/linux_upload_clang/build/src/third_party/llvm/compiler-rt/lib/asan/asan_interceptors_memintrinsics.cc:23:3 in __asan_memcpy
Shadow bytes around the buggy address:
  0x0c3680000c70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c3680000c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c3680000c90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c3680000ca0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c3680000cb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c3680000cc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00[fa]fa
  0x0c3680000cd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3680000ce0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3680000cf0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3680000d00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3680000d10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb


To reproduce this issue:

1) replace video/replay.cc with the attached version, and build it with asan (ninja -C out/asan video_replay). Note that this file adds the ability to load a full receiver