libarchive: bsdtar: heap-based buffer overflow in detect_form (archive_read_support_format_mtree.c)

Description:
libarchive is a multi-format archive and compression library.

After it got fuzzed by hanno and some other people (1 2 3)I decided to fuzz it too.

A crafted file causes an heap overflow in the detect_form function in the mtree parser.

The complete ASan output:

# bsdtar -t -f $FILE
==25612==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7fadef29981e at pc 0x7fadeec6fbac bp 0x7ffd2318bb30 sp 0x7ffd2318bb28                                                      
READ of size 1 at 0x7fadef29981e thread T0                                                                                                                                                     
    #0 0x7fadeec6fbab in detect_form /var/tmp/portage/app-arch/libarchive-3.2.1-r3/work/libarchive-3.2.1/libarchive/archive_read_support_format_mtree.c:692:26                                 
    #1 0x7fadeeb3518b in choose_format /var/tmp/portage/app-arch/libarchive-3.2.1-r3/work/libarchive-3.2.1/libarchive/archive_read.c:712:10                                                    
    #2 0x7fadeeb3518b in archive_read_open1 /var/tmp/portage/app-arch/libarchive-3.2.1-r3/work/libarchive-3.2.1/libarchive/archive_read.c:529
    #3 0x7fadeeb6cf1f in archive_read_open_filename /var/tmp/portage/app-arch/libarchive-3.2.1-r3/work/libarchive-3.2.1/libarchive/archive_read_open_filename.c:109:9
    #4 0x501f66 in read_archive /var/tmp/portage/app-arch/libarchive-3.2.1-r3/work/libarchive-3.2.1/tar/read.c:223:6
    #5 0x501473 in tar_mode_t /var/tmp/portage/app-arch/libarchive-3.2.1-r3/work/libarchive-3.2.1/tar/read.c:94:2
    #6 0x4f8929 in main /var/tmp/portage/app-arch/libarchive-3.2.1-r3/work/libarchive-3.2.1/tar/bsdtar.c:803:3
    #7 0x7fadedba861f in __libc_start_main /var/tmp/portage/sys-libs/glibc-2.22-r4/work/glibc-2.22/csu/libc-start.c:289
    #8 0x41b778 in _init (/usr/bin/bsdtar+0x41b778)

0x7fadef29981e is located 4126 bytes to the right of 262144-byte region [0x7fadef258800,0x7fadef298800)
allocated by thread T0 here:
    #0 0x4c2cc8 in malloc /var/tmp/portage/sys-devel/llvm-3.8.0-r3/work/llvm-3.8.0.src/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:52
    #1 0x7fadeeb3cbca in __archive_read_filter_ahead /var/tmp/portage/app-arch/libarchive-3.2.1-r3/work/libarchive-3.2.1/libarchive/archive_read.c:1436:17

SUMMARY: AddressSanitizer: heap-buffer-overflow /var/tmp/portage/app-arch/libarchive-3.2.1-r3/work/libarchive-3.2.1/libarchive/archive_read_support_format_mtree.c:692:26 in detect_form
Shadow bytes around the buggy address:
  0x0ff63de4b2b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff63de4b2c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff63de4b2d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff63de4b2e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff63de4b2f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0ff63de4b300: fa fa fa[fa]fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff63de4b310: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff63de4b320: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff63de4b330: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff63de4b340: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0ff63de4b350: 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
==25612==ABORTING

Affected version:
3.2.1

Fixed version:
3.2.2

Commit fix:
https://github.com/libarchive/libarchive/commit/eec077f52bfa2d3f7103b4b74d52572ba8a15aca

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

CVE:
CVE-2016-8688

Timeline:
2016-08-11: bug discovered
2016-08-11: bug reported to upstream
2016-09-11: blog post about the issue
2016-09-19: upstream released a patch
2016-10-16: CVE Assigned
2016-10-24: Upstream released 3.2.2

Note:
This bug was found with American Fuzzy Lop.

Permalink:

libarchive: bsdtar: heap-based buffer overflow in detect_form (archive_read_support_format_mtree.c)

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