binutils: heap-based buffer overflow in _bfd_x86_elf_get_synthetic_symtab (elfxx-x86.c)

["Agostino Sarubbo" <ago () gentoo org>]

Description:
binutils is a set of tools necessary to build programs.

The complete ASan output of the issue:

# nm -A -a -l -S -s --special-syms --synthetic --with-symbol-versions -D $FILE
==40547==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x61a000000574 at pc 0x0000004c1ca8 bp 0x7ffc34f58d10 
sp 0x7ffc34f584c0
WRITE of size 6 at 0x61a000000574 thread T0
    #0 0x4c1ca7 in __asan_memcpy 
/var/tmp/portage/sys-libs/compiler-rt-sanitizers-5.0.0/work/compiler-rt-5.0.0.src/lib/asan/asan_interceptors.cc:466
    #1 0x7f6df2a247e5 in _bfd_x86_elf_get_synthetic_symtab 
/var/tmp/portage/sys-devel/binutils-9999/work/binutils/bfd/elfxx-x86.c:1946:3
    #2 0x7f6df29f7b7a in elf_x86_64_get_synthetic_symtab 
/var/tmp/portage/sys-devel/binutils-9999/work/binutils/bfd/elf64-x86-64.c:4963:10
    #3 0x513df5 in display_rel_file /var/tmp/portage/sys-devel/binutils-9999/work/binutils/binutils/nm.c:1155:21
    #4 0x510f56 in display_file /var/tmp/portage/sys-devel/binutils-9999/work/binutils/binutils/nm.c:1318:7
    #5 0x50faae in main /var/tmp/portage/sys-devel/binutils-9999/work/binutils/binutils/nm.c:1792:12
    #6 0x7f6df19d1680 in __libc_start_main 
/var/tmp/portage/sys-libs/glibc-2.23-r4/work/glibc-2.23/csu/../csu/libc-start.c:289
    #7 0x41ac18 in _init (/usr/x86_64-pc-linux-gnu/binutils-bin/git/nm+0x41ac18)

0x61a000000574 is located 0 bytes to the right of 1268-byte region [0x61a000000080,0x61a000000574)
allocated by thread T0 here:
    #0 0x4d8e08 in malloc 
/var/tmp/portage/sys-libs/compiler-rt-sanitizers-5.0.0/work/compiler-rt-5.0.0.src/lib/asan/asan_malloc_linux.cc:67
    #1 0x7f6df299dd5c in bfd_malloc /var/tmp/portage/sys-devel/binutils-9999/work/binutils/bfd/libbfd.c:193:9
    #2 0x7f6df299dd5c in bfd_zmalloc /var/tmp/portage/sys-devel/binutils-9999/work/binutils/bfd/libbfd.c:278
    #3 0x7f6df2a23e29 in _bfd_x86_elf_get_synthetic_symtab 
/var/tmp/portage/sys-devel/binutils-9999/work/binutils/bfd/elfxx-x86.c:1829:26
    #4 0x7f6df29f7b7a in elf_x86_64_get_synthetic_symtab 
/var/tmp/portage/sys-devel/binutils-9999/work/binutils/bfd/elf64-x86-64.c:4963:10
    #5 0x513df5 in display_rel_file /var/tmp/portage/sys-devel/binutils-9999/work/binutils/binutils/nm.c:1155:21
    #6 0x510f56 in display_file /var/tmp/portage/sys-devel/binutils-9999/work/binutils/binutils/nm.c:1318:7
    #7 0x50faae in main /var/tmp/portage/sys-devel/binutils-9999/work/binutils/binutils/nm.c:1792:12
    #8 0x7f6df19d1680 in __libc_start_main 
/var/tmp/portage/sys-libs/glibc-2.23-r4/work/glibc-2.23/csu/../csu/libc-start.c:289

SUMMARY: AddressSanitizer: heap-buffer-overflow 
/var/tmp/portage/sys-libs/compiler-rt-sanitizers-5.0.0/work/compiler-rt-5.0.0.src/lib/asan/asan_interceptors.cc:466 in 
__asan_memcpy
Shadow bytes around the buggy address:
  0x0c347fff8050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c347fff8060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c347fff8070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c347fff8080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c347fff8090: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c347fff80a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00[04]fa
  0x0c347fff80b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c347fff80c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c347fff80d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c347fff80e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c347fff80f0: 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
==40547==ABORTING

Affected version:
2.29.51.20170921 and maybe past releases

Fixed version:
N/A

Commit fix:
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=61e3bf5f83f7e505b6bc51ef65426e5b31e6e360
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=56933f9e3e90eebf1018ed7417d6c1184b91db6b

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

CVE:
CVE-2017-14729

Reproducer:
https://github.com/asarubbo/poc/blob/master/00367-binutils-heapoverflow-_bfd_x86_elf_get_synthetic_symtab

Timeline:
2017-09-21: bug discovered and reported to upstream
2017-09-22: upstream released a patch
2017-09-25: blog post about the issue
2017-09-25: CVE assigned

Note:
This bug was found with American Fuzzy Lop.
This bug was identified with bare metal servers donated by Packet. This work is also supported by the Core 
Infrastructure Initiative.

Permalink:
https://blogs.gentoo.org/ago/2017/09/25/binutils-heap-based-buffer-overflow-in-_bfd_x86_elf_get_synthetic_symtab-elfxx-x86-c/

--
Agostino Sarubbo
Gentoo Linux Developer