Internet Bug Bounty: CVE-2017-13019: The PGM parser in tcpdump before 4.9.2 has a buffer over-read in print-pgm.c:pgm_print()

Hello,

The vulnerable code portion is linked below. The linked function is responsible for printing PGM packet payload information to the terminal (e.g., stdout)

https://github.com/the-tcpdump-group/tcpdump/commit/4601c685e7fd19c3724d5e499c69b8d3ec49933e

The issue may be reproduced as follows

Check out vulnerable tcpdump commit (< 4.9.2) as follows

$ git clone -b 26a6799b9ca80508c05cac7a9a3bef922991520b https://github.com/the-tcpdump-group/tcpdump

Build it with afl and AddressSanitizer as follows (please install libpcap before this step)

$ CC=afl-gcc
$ AFL_USE_ASAN=1 make -j

Run tcpdump against linked payload (link: https://github.com/the-tcpdump-group/tcpdump/blob/4601c685e7fd19c3724d5e499c69b8d3ec49933e/tests/pgm_opts_asan_2.pcap?raw=true)

$ tcpdump -nvr <payload>
reading from file /tmp/pgm_opts_asan_2.pcap, link-type EN10MB (Ethernet)
=================================================================
==3947==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60800000007d at pc 0x5560b85896f6 bp 0x7ffe420b1ca0 sp 0x7ffe420b1c90
READ of size 4 at 0x60800000007d thread T0
    #0 0x5560b85896f5 in EXTRACT_32BITS extract.h:190
    #1 0x5560b85896f5 in pgm_print print-pgm.c:697
    #2 0x5560b849f20c in ip_print_demux print-ip.c:483
    #3 0x5560b849f20c in ip_print print-ip.c:658
    #4 0x5560b84506df in ethertype_print print-ether.c:334
    #5 0x5560b84531d1 in ether_print print-ether.c:237
    #6 0x5560b84531d1 in ether_if_print print-ether.c:262
    #7 0x5560b83b76be in pretty_print_packet print.c:332
    #8 0x5560b839062d in print_packet tcpdump.c:2590
    #9 0x5560b8663ee8 in pcap_offline_read savefile.c:561
    #10 0x5560b8652e5e in pcap_loop pcap.c:2737
    #11 0x5560b8383fed in main tcpdump.c:2093
    #12 0x7f7aaf546b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
    #13 0x5560b838c009 in _start (/home/bhargava/work/github/tcpdump/tcpdump+0x17c009)

0x60800000007f is located 0 bytes to the right of 95-byte region [0x608000000020,0x60800000007f)
allocated by thread T0 here:
    #0 0x7f7aafc0ab50 in __interceptor_malloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xdeb50)
    #1 0x5560b8664c7a in pcap_check_header sf-pcap.c:404

SUMMARY: AddressSanitizer: heap-buffer-overflow extract.h:190 in EXTRACT_32BITS
Shadow bytes around the buggy address:
  0x0c107fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c107fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c107fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c107fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c107fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c107fff8000: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00[07]
  0x0c107fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c107fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c107fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c107fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c107fff8050: 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
==3947==ABORTING

It is acknowledged here(link: https://github.com/the-tcpdump-group/tcpdump/commit/4601c685e7fd19c3724d5e499c69b8d3ec49933e) that I (Bhargava Shastry) am the original reporter of the issue.

To prove that this hackerone account belongs to me, I have hosted a file with the following message on my github page(link: https://bshastry.github.io/.well-known/hackerone.txt)

hello @turtle_shell @hackerone

If you have any further queries, please let me know.

Tracked as CVE-2017-13019: https://nvd.nist.gov/vuln/detail/CVE-2017-13019

Impact

I believe that information disclosure is possible.