John Heasman of NGSSoftware has discovered several high risk vulnerabilities
in the handling of WMF and EMF graphics formats within the OpenOffice
The vulnerabilities, three heap overflows, affect OpenOffice 2.1.0 and
StarOffice 6, 7 and 8. If an attacker can coax a user into opening a
specially crafted document then the attacker can execute arbitrary code in
the security context of their victim.
1) From svtools\source\filter.vcl\wmf\winwmf.cxx
case W_META_ESCAPE :
sal_uInt32 i, nStringLen, nDXCount;
aMemoryStream >> aPt.X()
sal_Unicode* pBuf = aString.AllocBuffer( (sal_uInt16)nStringLen );
for ( i = 0; i < nStringLen; i++ )
aMemoryStream >> pBuf[ i ];
nStringLen is a sal_uInt32; it is cast to a sal_uInt16 for the allocation
then the original 32 bit value is used as a count to fill the buffer, thus
any length greater than 0xFFFF results in a heap overflow. Code execution is
possible via a function pointer overwrite or arbitrary DWORD overwrite if
the user opens a malicious WMF, or a container document (such as a Microsoft
Word document) in which it is embedded.
2) From svtools\source\filter.vcl\wmf\enhwmf.cxx
case EMR_POLYPOLYGON :
INT32 i, nPoly, nGesPoints;
*pWMF >> nPoly >> nGesPoints;
pPtAry = (Point*) new char[ nGesPoints * sizeof(Point) ];
for ( i = 0; i < nGesPoints; i++ )
*pWMF >> nX32 >> nY32;
pPtAry[ i ] = Point( nX32, nY32 );
nGesPoints * sizeof(Point) will result in an integer wrap if nGesPoints is >
(0x100000000 / sizeof(Point)).
Code execution is possible via a function pointer overwrite.
3) As above but for EMR_POLYPOLYGON16 record.
These issues have now been resolved; OpenOffice and StarOffice users are
strongly recommended to install the relevant patch, available from the
OpenOffice and SunSolve websites:
NGSSoftware Insight Security Research
+44(0)208 401 0070
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