libtiff: assertion failure in readSeparateTilesIntoBuffer (tiffcp.c)

[Agostino Sarubbo <ago () gentoo org>]

Description:
Libtiff is a software that provides support for the Tag Image File Format 
(TIFF), a widely used format for storing image data.

A crafted tiff file revealed an assertion failure.

The complete output:

# tiffcp -i $FILE /tmp/foo
tiffcp: /tmp/portage/media-
libs/tiff-4.0.7/work/tiff-4.0.7/tools/tiffcp.c:1390:
int readSeparateTilesIntoBuffer(TIFF *, uint8 *, uint32, uint32, tsample_t):
Assertion `bps % 8 == 0' failed.

Affected version:
4.0.7

Fixed version:
N/A

Commit fix:
https://github.com/vadz/libtiff/commit/7ff9652da2eec4c65279dcbc7e55c0418e87bbc8

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

CVE:
N/A

Reproducer:
https://github.com/asarubbo/poc/blob/master/00072-libtiff-assert-readSeparateTilesIntoBuffer

Timeline:
2016-11-23: bug discovered and reported to upstream
2016-12-03: upstream released a patch
2017-01-01: blog post about the issue

Note:
This bug was found with American Fuzzy Lop.

Permalink:
https://blogs.gentoo.org/ago/2017/01/01/libtiff-assertion-failure-in-readseparatetilesintobuffer-tiffcp-c

-- 
Agostino Sarubbo
Gentoo Linux Developer