[Bug] heap buffer overflow in parse_mpls

[kdsjZh]

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Describe the bug
There is a heap-overflow bug found in parse_mpls, can be triggered via tcpprep+ ASan

To Reproduce
Steps to reproduce the behavior:

1. export CC=clang && export CFLAGS="-fsanitize=address -g"
2. ./autogen.sh && ./configure --disable-shared --disable-local-libopts && make clean && make -j8
3. ./src/tcpprep --auto=bridge --pcap=$POC --cachefile=/dev/null

Output:

==2021941==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000142 at pc 0x000000448721 bp 0x7fff4fd006f0 sp 0x7fff4fd006e0
READ of size 4 at 0x602000000142 thread T0
    #0 0x448720 in parse_mpls (/validate/run1/tcpreplay/tcpprep+0x448720)
    #1 0x44edb0 in parse_metadata (/validate/run1/tcpreplay/tcpprep+0x44edb0)
    #2 0x44c591 in get_l2len_protocol (/validate/run1/tcpreplay/tcpprep+0x44c591)
    #3 0x44fa30 in get_ipv4 (/validate/run1/tcpreplay/tcpprep+0x44fa30)
    #4 0x41434c in process_raw_packets (/validate/run1/tcpreplay/tcpprep+0x41434c)
    #5 0x412708 in main (/validate/run1/tcpreplay/tcpprep+0x412708)
    #6 0x7f6b96777d8f  (/lib/x86_64-linux-gnu/libc.so.6+0x2dd8f)
    #7 0x7f6b96777e3f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2de3f)
    #8 0x4085f4 in _start (/validate/run1/tcpreplay/tcpprep+0x4085f4)

0x602000000142 is located 2 bytes to the right of 16-byte region [0x602000000130,0x602000000140)
allocated by thread T0 here:
    #0 0x4dd0d8 in __interceptor_realloc (/validate/run1/tcpreplay/tcpprep+0x4dd0d8)
    #1 0x7f6b969bd1c7  (/lib/x86_64-linux-gnu/libpcap.so.0.8+0x291c7)

SUMMARY: AddressSanitizer: heap-buffer-overflow (/validate/run1/tcpreplay/tcpprep+0x448720) in parse_mpls
Shadow bytes around the buggy address:
  0x0c047fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff8000: fa fa fd fd fa fa fd fd fa fa fd fd fa fa fd fd
  0x0c047fff8010: fa fa fd fd fa fa fd fd fa fa fd fd fa fa fd fd
=>0x0c047fff8020: fa fa fd fd fa fa 00 00[fa]fa fa fa fa fa fa fa
  0x0c047fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8060: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8070: 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
  Shadow gap:              cc
==2021941==ABORTING

System (please complete the following information):

• OS: Ubuntu 20.04
• Clang 12.0.1
• Tcpreplay Version : latest commit 09f0774

Credit
NCNIPC of China
Hexhive

POC

POC2.zip

[fklassen]

Improved overflow protection for parse_mpls() in PR #741