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Date: Sat, 08 Oct 2016 22:16:25 +0200
From: Agostino Sarubbo <ago@...too.org>
To: oss-security@...ts.openwall.com
Subject: libdwarf: heap-based buffer overflow in _dwarf_get_abbrev_for_code (dwarf_util.c)

Description:
libdwarf is a library to consume and produce DWARF debug information.

A fuzzing revealed an out bounds read,

The complete ASan output:

# dwarfdump $FILE
==30323==ERROR: AddressSanitizer: heap-buffer-overflow on address 
0x611000005a00 at pc 0x000000606e87 bp 0x7ffe35e5e5b0 sp 0x7ffe35e5e5a8
READ of size 1 at 0x611000005a00 thread T0
    #0 0x606e86 in _dwarf_get_abbrev_for_code 
/tmp/dwarf-20161001/libdwarf/dwarf_util.c:624:43
    #1 0x576086 in dwarf_siblingof_b 
/tmp/dwarf-20161001/libdwarf/dwarf_die_deliv.c:1628:12
    #2 0x517e73 in print_die_and_children_internal 
/tmp/dwarf-20161001/dwarfdump/print_die.c:1163:17
    #3 0x517c6b in print_die_and_children_internal 
/tmp/dwarf-20161001/dwarfdump/print_die.c:1142:13
    #4 0x5147cc in print_die_and_children 
/tmp/dwarf-20161001/dwarfdump/print_die.c:921:5
    #5 0x5147cc in print_one_die_section 
/tmp/dwarf-20161001/dwarfdump/print_die.c:831
    #6 0x512262 in print_infos 
/tmp/dwarf-20161001/dwarfdump/print_die.c:371:16
    #7 0x4faaea in process_one_file 
/tmp/dwarf-20161001/dwarfdump/dwarfdump.c:1371:9
    #8 0x4faaea in main /tmp/dwarf-20161001/dwarfdump/dwarfdump.c:654
    #9 0x7f5912c2361f in __libc_start_main /var/tmp/portage/sys-
libs/glibc-2.22-r4/work/glibc-2.22/csu/libc-start.c:289
    #10 0x419588 in _start (/usr/bin/dwarfdump-asan+0x419588)

0x611000005a00 is located 0 bytes to the right of 256-byte region 
[0x611000005900,0x611000005a00)
allocated by thread T0 here:
    #0 0x4c0ad8 in malloc /var/tmp/portage/sys-devel/llvm-3.8.1-
r2/work/llvm-3.8.1.src/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:52
    #1 0x7f5913cfd206 in __libelf_set_rawdata_wrlock /tmp/portage/dev-
libs/elfutils-0.166/work/elfutils-0.166/libelf/elf_getdata.c:318

SUMMARY: AddressSanitizer: heap-buffer-overflow 
/tmp/dwarf-20161001/libdwarf/dwarf_util.c:624:43 in _dwarf_get_abbrev_for_code
Shadow bytes around the buggy address:
  0x0c227fff8af0: fa fa fa fa fa fa fa fa fd fd fd fd fd fd fd fd
  0x0c227fff8b00: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c227fff8b10: fd fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff8b20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c227fff8b30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c227fff8b40:[fa]fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
  0x0c227fff8b50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c227fff8b60: 00 fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c227fff8b70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c227fff8b80: 00 00 00 00 00 00 00 00 00 fa fa fa fa fa fa fa
  0x0c227fff8b90: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
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
  Heap right redzone:      fb
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack partial redzone:   f4
  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
==30323==ABORTING

Affected version:
20161001 and past

Fixed version:
N/A

Commit fix:
https://sourceforge.net/p/libdwarf/code/ci/268c1f18d1d28612af3b72d7c670076b1b88e51c/tree/libdwarf/dwarf_util.c?diff=0b28b923c3bd9827d1d904feed2abadde4fa5de2

Credit:
This bug was discovered by Agostino Sarubbo of Gentoo.

Timeline:
2016-10-03: bug discovered
2016-10-03: bug reported privately to upstream
2016-10-03: upstream realeased a patch
2016-10-04: blog post about the issue

Note:
This bug was found with American Fuzzy Lop.

Permalink:
https://blogs.gentoo.org/ago/2016/10/04/libdwarf-heap-based-buffer-overflow-in-_dwarf_get_abbrev_for_code-dwarf_util-c/

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