Date: Mon Apr 11 16:09:42 2005
From: lab at venustech.com.cn (adlab)
Subject: OpenOffice DOC document Heap Overflow

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OpenOffice DOC document Heap Overflow
[Security Advisory]

Advisory:[AD_LAB-05001] OpenOffice DOC document Heap Overflow
Class: Design Error
DATE:30/3/2005
CVEID:CAN-2005-0941
Vulnerable:
    <=OpenOffice OpenOffice 1.1.4
    -OpenOffice OpenOffice 2.0dev

Unvulnerable:
    Unknow
Vendor:
     www.openoffice.org

I.DESCRIPTION:
- -------------
     OpenOffice.org is an office productivity suite, including word
processing, spreadsheets, presentations, drawings, data charting,
formula editing, and file conversion facilities.
The vulnerability is caused due to a  error within the .Doc document header
processing.This can be exploited to cause a heap-based buffer overflow.

II.DETAILS:
- ----------
    There is a vulnerability in  StgCompObjStream::Load() function,
When reading DOC document information of format,memory is allocated by
DOC provide length.
DOC provided a 32 bits integer,and will use the low 16 bits of this
number to allocate memory,
but when reading doc information,still use the 32 bits number as
length,this maybe cause heap
overflow, and when free happened ,will cause write pointer,maybe cause
arbitrary code excute .

BOOL StgCompObjStream::Load()
{
    memset( &aClsId, 0, sizeof( ClsId ) );
    nCbFormat = 0;
    aUserName.Erase();
    if( GetError() != SVSTREAM_OK )
        return FALSE;
    Seek( 8L );
    INT32 nMarker = 0;
    *this >> nMarker;
    if( nMarker == -1L )
    {
        *this >> aClsId;
        INT32 nLen1 = 0;
        *this >> nLen1; // we can control this 32 bits int
        sal_Char* p = new sal_Char[ (USHORT) nLen1 ]; //use low 16 bits
value to allocate memory
        if( Read( p, nLen1 ) == (ULONG) nLen1 ) //still use 32 bits int
 as length,if failed,
                            // will goto free step,maybe cause write
pointer.
        {
            aUserName = String( p, gsl_getSystemTextEncoding() );
            ....
            nCbFormat = ReadClipboardFormat( *this );
        }
        else
            SetError( SVSTREAM_GENERALERROR );
        delete [] p; //free step,heap overflow cause write pointer.
    }
    return BOOL( GetError() == SVSTREAM_OK );
}
example:
    if we provide 0x10000018 to nLen1,will allocate 0x18 length memory,
 Read( p, nLen1 ) still use 0x10000018 as length,then, read will fail,
 but readed length is bigger than allocated memory,and overwrite the
next chunk.
when goto delete [] p;,write pointer happened. we had triggered this
problem successful.
    StartOffice maybe affected too. did not test.


III.CREDIT:
- ----------
    AD-LAB discovery this vuln:)
Vulnerability analysis and advisory by A1rsupp1y.
Special thanks to xalan's  discussion.
Thank to Sam,icbm,liangbin and all Venustech AD-Lab guys:P.



V.DISCLAIMS:
- -----------

The information in this bulletin is provided "AS IS" without warranty of any
kind. In no event shall we be liable for any damages whatsoever
including direct,
indirect, incidental, consequential, loss of business profits or special
damages.

Copyright 1996-2005 VENUSTECH. All Rights Reserved. Terms of use.

VENUSTECH Security Lab
VENUSTECH INFORMATION TECHNOLOGY CO.,LTD(http://www.venustech.com.cn)

Security
Trusted {Solution} Provider
Service



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