heap overflow in _dwarf_check_string_valid in dwarf_util.c

[sleicasper]

There is a heap overflow in _dwarf_check_string_valid in dwarf_util.c. Depending on the usage of this library, this may cause code execution or deny of service.

reproduce steps:

1. compile libdwarf with address sanitizer
2. run dwarfdump with poc file

dwarfdump -vv -a ./poc

poc:
poc.zip

Address sanitizer output:

=================================================================
==1464907==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6060000015bb at pc 0x00000083fa88 bp 0x7fff18213420 sp 0x7fff18213418
READ of size 1 at 0x6060000015bb thread T0
    #0 0x83fa87 in _dwarf_check_string_valid /home/casper/targets/struct/libdwarf/aflasan/SRC/src/lib/libdwarf/dwarf_util.c:938:13
    #1 0x70192c in _dwarf_internal_get_pubnames_like_data /home/casper/targets/struct/libdwarf/aflasan/SRC/src/lib/libdwarf/dwarf_global.c:560:19
    #2 0x7e43be in dwarf_get_pubtypes /home/casper/targets/struct/libdwarf/aflasan/SRC/src/lib/libdwarf/dwarf_pubtypes.c:63:11
    #3 0x637fa0 in print_types /home/casper/targets/struct/libdwarf/aflasan/SRC/src/bin/dwarfdump/print_types.c:90:13
    #4 0x519257 in process_one_file /home/casper/targets/struct/libdwarf/aflasan/SRC/src/bin/dwarfdump/dwarfdump.c:1242:16
    #5 0x512ac7 in main /home/casper/targets/struct/libdwarf/aflasan/SRC/src/bin/dwarfdump/dwarfdump.c:503:9
    #6 0x7f1199de00b2 in __libc_start_main /build/glibc-sMfBJT/glibc-2.31/csu/../csu/libc-start.c:308:16
    #7 0x42848d in _start (/home/casper/targets/struct/libdwarf/aflasan/fuzzrun/dwarfdump+0x42848d)

0x6060000015bb is located 0 bytes to the right of 59-byte region [0x606000001580,0x6060000015bb)
allocated by thread T0 here:
    #0 0x4cd59f in malloc /home/casper/fuzz/fuzzdeps/llvm-project-11.0.0/compiler-rt/lib/asan/asan_malloc_linux.cpp:145:3
    #1 0x870cd5 in elf_load_nolibelf_section /home/casper/targets/struct/libdwarf/aflasan/SRC/src/lib/libdwarf/dwarf_elfread.c:229:26
    #2 0x4969e5 in vprintf /home/casper/fuzz/fuzzdeps/llvm-project-11.0.0/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:1641:1

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/casper/targets/struct/libdwarf/aflasan/SRC/src/lib/libdwarf/dwarf_util.c:938:13 in _dwarf_check_string_valid
Shadow bytes around the buggy address:
  0x0c0c7fff8260: fd fd fd fa fa fa fa fa fd fd fd fd fd fd fd fa
  0x0c0c7fff8270: fa fa fa fa fd fd fd fd fd fd fd fa fa fa fa fa
  0x0c0c7fff8280: 00 00 00 00 00 00 00 00 fa fa fa fa 00 00 00 00
  0x0c0c7fff8290: 00 00 00 00 fa fa fa fa 00 00 00 00 00 00 00 00
  0x0c0c7fff82a0: fa fa fa fa 00 00 00 00 00 00 00 00 fa fa fa fa
=>0x0c0c7fff82b0: 00 00 00 00 00 00 00[03]fa fa fa fa fa fa fa fa
  0x0c0c7fff82c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0c7fff82d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0c7fff82e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0c7fff82f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c0c7fff8300: 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

[davea42]

Thank you for the report and test case. I assigned this libdwarf vulnerability as
DW202205-001 and have pushed the fix .
View the vulnerability on www.prevanders.net/dwarfbug.html