[bug-cflow] A heap-buffer-overflow problem in nexttoken function in /src

Hi there,

I have found a heap-buffer-overflow problem in nexttoken function in /src/parser.c in cflow 1.6 the lastest release version. This bug can also reproduce in cflow 1.5. I have confirmed them with address sanitizer too.

Here are the POC files. Please use the "./cflow $POC" to reproduce the bug.

The ASAN dumps the stack trace as follows:

=================================================================
==8202==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x61f000000c80 at pc 0x0000004d9762 bp 0x7ffe9d88e430 sp 0x7ffe9d88dbe0
READ of size 24 at 0x61f000000c80 thread T0
    #0 0x4d9761 in __asan_memcpy /llvm-6.0.1/projects/compiler-rt/lib/asan/asan_interceptors_memintrinsics.cc:23
    #1 0x549214 in nexttoken /cflow-1.6/src/parser.c:302:12
    #2 0x54f134 in parse_function_declaration /cflow-1.6/src/parser.c:673:9
    #3 0x54ea79 in parse_declaration /cflow-1.6/src/parser.c:578:4
    #4 0x54de68 in yyparse /cflow-1.6/src/parser.c:528:9
    #5 0x53b254 in main /cflow-1.6/src/main.c:812:7
    #6 0x7f54ee2e882f in __libc_start_main /build/glibc-Cl5G7W/glibc-2.23/csu/../csu/libc-start.c:291
    #7 0x41a978 in _start (/cflow-1.6/build/bin/cflow+0x41a978)

0x61f000000c80 is located 0 bytes to the right of 3072-byte region [0x61f000000080,0x61f000000c80)
allocated by thread T0 here:
    #0 0x4dad20 in realloc /home/wencheng/Documents/llvm-6.0.1/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:107
    #1 0x5bde5f in xrealloc /cflow-1.6/gnu/xmalloc.c:63:7

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/wencheng/Documents/llvm-6.0.1/projects/compiler-rt/lib/asan/asan_interceptors_memintrinsics.cc:23 in __asan_memcpy
Shadow bytes around the buggy address:
  0x0c3e7fff8140: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c3e7fff8150: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c3e7fff8160: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c3e7fff8170: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c3e7fff8180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c3e7fff8190:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3e7fff81a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3e7fff81b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3e7fff81c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3e7fff81d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3e7fff81e0: 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
==8202==ABORTING
Aborted

If you have any question, please let me know.

From:	wcventure
Subject:	[bug-cflow] A heap-buffer-overflow problem in nexttoken function in /src/parser.c in cflow 1.6 the lastest release version
Date:	Mon, 1 Apr 2019 14:19:50 +0800 (CST)