Bug 183677

Summary: CVE-2006-0747 Freetype integer underflow
Product: [Fedora] Fedora Reporter: Josh Bressers <bressers>
Component: freetypeAssignee: Behdad Esfahbod <behdad>
Status: CLOSED RAWHIDE QA Contact: Brock Organ <borgan>
Severity: medium Docs Contact:
Priority: medium    
Version: 5CC: security-response-team
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard: source=redhat,reported=20060302,embargo=yes,impact=moderate
Fixed In Version: Doc Type: Bug Fix
Doc Text:
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Clone Of: Environment:
Last Closed: 2008-03-11 01:01:29 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Flags
testcase none

Description Josh Bressers 2006-03-02 19:20:14 UTC
Freetype integer underflow

While fuzzing some pdf files a few weeks back, I ended up finding an
integer underflow in freetype2.  Upstream did commit some fixes, so
this issue is somewhat public.

1.ttf will generate this error.

Patches:
http://cvs.savannah.gnu.org/viewcvs/freetype/freetype2/src/pshinter/pshglob.c?r1=1.30&r2=1.31&makepatch=1&diff_format=h
http://cvs.savannah.gnu.org/viewcvs/freetype/freetype2/src/cff/cffload.c?r1=1.73&r2=1.74&makepatch=1&diff_format=h
http://cvs.savannah.gnu.org/viewcvs/freetype/freetype2/src/type1/t1load.c?r1=1.104&r2=1.105&makepatch=1&diff_format=h

The problem is the number of blue values needs to be even.  If a font
file claims it's odd, freetype2 doesn't handle it well.


The crash is seen in src/pshinter/pshglob.c:psh_blues_set_zones_0()

What was basically happening is since read_count is an unsigned
integer, and is decremented by 2, it is possible to cause an integer
underflow by ensuring the value of read_count is an odd number.  Once
read_count underflows, the loop starts dumping garbage onto the heap.
Normally I wouldn't think this is exploitable as it should crash
before anything exciting can happen, most graphical applications are
multi-threaded, so this does worry me.  At the very least this issue
is a denial of service bug.

The 2.ttf file in the testcase will also trigger a NULL pointer
dereference, which I'm not considering a secuirty issue.  The patch is
here:

http://cvs.savannah.gnu.org/viewcvs/freetype/freetype2/src/base/ftutil.c?r1=1.17&r2=1.18&makepatch=1&diff_format=h

Comment 1 Josh Bressers 2006-03-02 19:21:41 UTC
Created attachment 125556 [details]
testcase

Comment 2 Josh Bressers 2006-05-15 18:01:09 UTC
Lifting embargo

Comment 3 Josh Bressers 2006-05-15 18:01:48 UTC
This issue also affects FC4