Description:
potrace is a utility that transforms bitmaps into vector graphics.
A fuzz on 1.14 showed that an overflow previously reported as CVE-2016-8698 was not really fixed. Since there isn’t a public git repository, I uploaded the patch on my ‘poc’ repository on github. The patch was sent from the upstream maintainer, Mr. Peter Selinger.
The complete ASan output:
# potrace $FILE
==7325==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60200000efd0 at pc 0x00000051dc51 bp 0x7ffc766b1a30 sp 0x7ffc766b1a28
READ of size 8 at 0x60200000efd0 thread T0
#0 0x51dc50 in bm_readbody_bmp /tmp/portage/media-gfx/potrace-1.14/work/potrace-1.14/src/bitmap_io.c:754:4
#1 0x51dc50 in bm_read /tmp/portage/media-gfx/potrace-1.14/work/potrace-1.14/src/bitmap_io.c:138
#2 0x510a45 in process_file /tmp/portage/media-gfx/potrace-1.14/work/potrace-1.14/src/main.c:1058:9
#3 0x50dd56 in main /tmp/portage/media-gfx/potrace-1.14/work/potrace-1.14/src/main.c:1214:7
#4 0x7f6c7333e78f in __libc_start_main /tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/csu/../csu/libc-start.c:289
#5 0x419b68 in getenv (/usr/bin/potrace+0x419b68)
0x60200000efd1 is located 0 bytes to the right of 1-byte region [0x60200000efd0,0x60200000efd1)
allocated by thread T0 here:
#0 0x4d2b25 in calloc /tmp/portage/sys-devel/llvm-3.9.1-r1/work/llvm-3.9.1.src/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:72
#1 0x519776 in bm_new /tmp/portage/media-gfx/potrace-1.14/work/potrace-1.14/src/bitmap.h:121:30
#2 0x519776 in bm_readbody_bmp /tmp/portage/media-gfx/potrace-1.14/work/potrace-1.14/src/bitmap_io.c:574
#3 0x519776 in bm_read /tmp/portage/media-gfx/potrace-1.14/work/potrace-1.14/src/bitmap_io.c:138
#4 0x510a45 in process_file /tmp/portage/media-gfx/potrace-1.14/work/potrace-1.14/src/main.c:1058:9
#5 0x50dd56 in main /tmp/portage/media-gfx/potrace-1.14/work/potrace-1.14/src/main.c:1214:7
#6 0x7f6c7333e78f in __libc_start_main /tmp/portage/sys-libs/glibc-2.23-r3/work/glibc-2.23/csu/../csu/libc-start.c:289
SUMMARY: AddressSanitizer: heap-buffer-overflow /tmp/portage/media-gfx/potrace-1.14/work/potrace-1.14/src/bitmap_io.c:754:4 in bm_readbody_bmp
Shadow bytes around the buggy address:
0x0c047fff9da0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9db0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9dc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9dd0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9de0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c047fff9df0: fa fa fa fa fa fa fa fa fa fa[01]fa fa fa 04 fa
0x0c047fff9e00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c047fff9e40: 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
==7325==ABORTING
Affected version:
1.14
Fixed version:
1.15
Commit fix:
https://github.com/asarubbo/poc/blob/master/00219-potrace-heapoverflow-bm_readbody_bmp-PATCH
Credit:
This bug was discovered by Agostino Sarubbo of Gentoo.
CVE:
CVE-2017-7263
Reproducer:
https://github.com/asarubbo/poc/blob/master/00210-potrace-heapoverflow-bm_readbody_bmp
Timeline:
2017-02-26: bug discovered and reported to upstream
2017-02-28: upstream released a patch
2017-03-03: blog post about the issue
2017-03-26: CVE assigned
Note:
This bug was found with American Fuzzy Lop.
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