Microsoft Windows - Uniscribe Font Processing Multiple Heap-Based Out-of-Bounds and Wild Reads (MS17

Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1031
 
Through fuzzing, we have discovered a number of different crashes in the Windows Uniscribe user-mode library, while trying to display text using a corrupted font file or calling documented Uniscribe API functions against such malformed fonts. In this bug, we address a variety of crashes manifested through invalid memory READ accesses. Some of them occur at page boundaries, while other at seemingly valid yet non-mapped addresses. The sheer amount of the crashes makes it very difficult for us to assess the root cause, severity and impact of each of them within a reasonable time-frame. Consequently, we have only performed basic deduplication based on the top-level address of the faulting instruction, and are reporting all of such crashes in this single bug tracker entry.
 
A summary of the crash locations is as follows:
 
--------------------------------------------------------------
1   USP10!otlMultiSubstLookup::apply+0xa8
2   USP10!otlSingleSubstLookup::applyToSingleGlyph+0x98
3   USP10!otlSingleSubstLookup::apply+0xa9
4   USP10!otlMultiSubstLookup::getCoverageTable+0x2c
5   USP10!otlMark2Array::mark2Anchor+0x18
6   USP10!GetSubstGlyph+0x2e
7   USP10!BuildTableCache+0x1ca
8   USP10!otlMkMkPosLookup::apply+0x1b4
9   USP10!otlLookupTable::markFilteringSet+0x1a
10  USP10!otlSinglePosLookup::getCoverageTable+0x12
11  USP10!BuildTableCache+0x1e7
12  USP10!otlChainingLookup::getCoverageTable+0x15
13  USP10!otlReverseChainingLookup::getCoverageTable+0x15
14  USP10!otlLigCaretListTable::coverage+0x7
15  USP10!otlMultiSubstLookup::apply+0x99
16  USP10!otlTableCacheData::FindLookupList+0x9
17  USP10!ttoGetTableData+0x4b4
18  USP10!GetSubtableCoverage+0x1ab
19  USP10!otlChainingLookup::apply+0x2d
20  USP10!MergeLigRecords+0x132
21  USP10!otlLookupTable::subTable+0x23
22  USP10!GetMaxParameter+0x53
23  USP10!ApplyLookup+0xc3
24  USP10!ApplyLookupToSingleGlyph+0x6f
25  USP10!ttoGetTableData+0x19f6
26  USP10!otlExtensionLookup::extensionSubTable+0x1d
27  USP10!ttoGetTableData+0x1a77
--------------------------------------------------------------
 
All of the issues reproduce successfully on Windows 7. It is highly encouraged to enable PageHeap for the test program in order to get reliable repros. It is also necessary to use a custom program which displays all of the font's glyphs at various point sizes, and additionally calls some of the Uniscribe-specific API functions.
 
Attached is an archive with textual crash excerpts and up to 3 samples per each unique crash.
 
 
Proof of Concept:
https://github.com/offensive-security/exploit-database-bin-sploits/raw/master/sploits/41655.zip

#  0day.today [2018-04-14]  #