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cwalter-at / freemodbus

BSD licensed MODBUS RTU/ASCII and TCP slave
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A global-buffer-overflow bug that can lead demo/LINUXTCP to crash #34

Open LeeHun9 opened 1 year ago

LeeHun9 commented 1 year ago

Hi, I am running some experiments for AFLNET and it has found a global-buffer-overflow bug in recv when sent this pdus to tcpmodbus

poc: poc.zip

To reproduce: Complie the demo/LINUXTCP with ASAN

then use aflnet-replay to send the binary_poc to the port, detail in aflnet

I also captured the pcap file when send those pdus to the tcpmodbus, both pcap and binary in poc.zip

ASAN show this information:

=================================================================
==62032==ERROR: AddressSanitizer: global-buffer-overflow on address 0x000000daefa7 at pc 0x00000046d94c bp 0x7f77940fec50 sp 0x7f77940fe418
WRITE of size 36 at 0x000000daefa7 thread T1
    #0 0x46d94b in recv (/home/ubuntu/Documents/freemodbus/demo/LINUXTCP/tcpmodbus+0x46d94b)
    #1 0x4c9d48 in xMBPortTCPPool /home/ubuntu/Documents/freemodbus/demo/LINUXTCP/port/porttcp.c:224:25
    #2 0x4c8ca4 in xMBPortEventGet /home/ubuntu/Documents/freemodbus/demo/LINUXTCP/port/portevent.c:69:17
    #3 0x4cb3df in eMBPoll /home/ubuntu/Documents/freemodbus/demo/LINUXTCP/../../modbus/mb.c:351:9
    #4 0x4c7dd4 in pvPollingThread /home/ubuntu/Documents/freemodbus/demo/LINUXTCP/demo.c:195:17
    #5 0x7f7797a97608 in start_thread /build/glibc-SzIz7B/glibc-2.31/nptl/pthread_create.c:477:8
    #6 0x7f7797842132 in clone /build/glibc-SzIz7B/glibc-2.31/misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:95

0x000000daefa7 is located 0 bytes to the right of global variable 'aucTCPBuf' defined in 'port/porttcp.c:80:17' (0xdaeea0) of size 263
SUMMARY: AddressSanitizer: global-buffer-overflow (/home/ubuntu/Documents/freemodbus/demo/LINUXTCP/tcpmodbus+0x46d94b) in recv
Shadow bytes around the buggy address:
  0x0000801adda0: 00 00 00 00 01 f9 f9 f9 f9 f9 f9 f9 04 f9 f9 f9
  0x0000801addb0: f9 f9 f9 f9 00 00 00 00 04 f9 f9 f9 f9 f9 f9 f9
  0x0000801addc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801addd0: f9 f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 00
  0x0000801adde0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0000801addf0: 00 00 00 00[07]f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
  0x0000801ade00: 02 f9 f9 f9 f9 f9 f9 f9 02 f9 f9 f9 f9 f9 f9 f9
  0x0000801ade10: 00 00 00 00 00 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9
  0x0000801ade20: f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9
  0x0000801ade30: f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9 01 f9 f9 f9
  0x0000801ade40: f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9
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
Thread T1 created by T0 here:
    #0 0x480dfa in pthread_create (/home/ubuntu/Documents/freemodbus/demo/LINUXTCP/tcpmodbus+0x480dfa)
    #1 0x4c6264 in bCreatePollingThread /home/ubuntu/Documents/freemodbus/demo/LINUXTCP/demo.c:169:13
    #2 0x4c6264 in main /home/ubuntu/Documents/freemodbus/demo/LINUXTCP/demo.c:92:21
    #3 0x7f7797747082 in __libc_start_main /build/glibc-SzIz7B/glibc-2.31/csu/../csu/libc-start.c:308:16

==62032==ABORTING