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Date: Sat, 08 Oct 2016 22:08:44 +0200
From: Agostino Sarubbo <ago@...too.org>
To: oss-security@...ts.openwall.com
Subject: libdwarf: heap-based buffer overflow in _dwarf_get_size_of_val (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
==22886==ERROR: AddressSanitizer: heap-buffer-overflow on address 
0x61300000de1c at pc 0x000000462c7c bp 0x7ffe80a3d230 sp 0x7ffe80a3c9e0
READ of size 1 at 0x61300000de1c thread T0
    #0 0x462c7b in __interceptor_strlen /var/tmp/portage/sys-devel/llvm-3.8.1-
r2/work/llvm-3.8.1.src/projects/compiler-rt/lib/asan/asan_interceptors.cc:581
    #1 0x60489f in _dwarf_get_size_of_val 
/tmp/dwarf-20161001/libdwarf/dwarf_util.c:267:21
    #2 0x5f2834 in dwarf_attrlist 
/tmp/dwarf-20161001/libdwarf/dwarf_query.c:389:27
    #3 0x519ed5 in print_one_die 
/tmp/dwarf-20161001/dwarfdump/print_die.c:1409:13
    #4 0x51710c in print_die_and_children_internal 
/tmp/dwarf-20161001/dwarfdump/print_die.c:1047:36
    #5 0x517c6b in print_die_and_children_internal 
/tmp/dwarf-20161001/dwarfdump/print_die.c:1142:13
    #6 0x5147cc in print_die_and_children 
/tmp/dwarf-20161001/dwarfdump/print_die.c:921:5
    #7 0x5147cc in print_one_die_section 
/tmp/dwarf-20161001/dwarfdump/print_die.c:831
    #8 0x512262 in print_infos 
/tmp/dwarf-20161001/dwarfdump/print_die.c:371:16
    #9 0x4faaea in process_one_file 
/tmp/dwarf-20161001/dwarfdump/dwarfdump.c:1371:9
    #10 0x4faaea in main /tmp/dwarf-20161001/dwarfdump/dwarfdump.c:654
    #11 0x7f7cd096261f in __libc_start_main /var/tmp/portage/sys-
libs/glibc-2.22-r4/work/glibc-2.22/csu/libc-start.c:289
    #12 0x419588 in _start (/usr/bin/dwarfdump-asan+0x419588)

0x61300000de1c is located 0 bytes to the right of 348-byte region 
[0x61300000dcc0,0x61300000de1c)
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 0x7f7cd1a3c206 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 /var/tmp/portage/sys-
devel/llvm-3.8.1-r2/work/llvm-3.8.1.src/projects/compiler-
rt/lib/asan/asan_interceptors.cc:581 in __interceptor_strlen
Shadow bytes around the buggy address:
  0x0c267fff9b70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c267fff9b80: 00 00 00 00 00 00 00 00 00 00 03 fa fa fa fa fa
  0x0c267fff9b90: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
  0x0c267fff9ba0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c267fff9bb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c267fff9bc0: 00 00 00[04]fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c267fff9bd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c267fff9be0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c267fff9bf0: 00 00 00 00 00 00 00 00 00 00 00 03 fa fa fa fa
  0x0c267fff9c00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c267fff9c10: 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
  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
==22886==ABORTING
Affected version:
20161001 and past

Fixed version:
N/A

Commit fix:
https://sourceforge.net/p/libdwarf/code/ci/2d14a7792889e33bc542c28d0f3792964c46214f/#diff-13 
and then 
https://sourceforge.net/p/libdwarf/code/ci/efe48cad0693d6994d9a7b561e1c3833b073a624/#diff-2 
(because of a mistake)

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

Timeline:
2016-10-04: bug discovered
2016-10-04: bug reported privately to upstream
2016-10-04: upstream realeased a patch
2016-10-06: blog post about the issue

Note:
This bug was found with American Fuzzy Lop.

Permalink:
https://blogs.gentoo.org/ago/2016/10/06/libdwarf-heap-based-buffer-overflow-in-_dwarf_get_size_of_val-dwarf_util-c/

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