Microsoft Windows – Uniscribe Font Processing Multiple Heap Out-of-Bounds and Wild Reads (MS17-011)

Exploit Database
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作者： Google Security Research

日期： 2017-03-20
类别：
- dos
平台：
- windows
来源：https://www.exploit-db.com/exploits/41655/

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://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/41655.zip