bugtraq - [PRE-SA-2012-05] Multiple heap-based buffer overflows in LibreOffice / OpenOffice

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Date: Fri, 10 Aug 2012 09:58:01 +0200
From: Timo Warns <warns@...-sense.de>
To: full-disclosure@...ts.grok.org.uk, bugtraq@...urityfocus.com
Subject: [PRE-SA-2012-05] Multiple heap-based buffer overflows in LibreOffice
 / OpenOffice

PRE-CERT Security Advisory
==========================

* Advisory: PRE-SA-2012-05
* Released on: 6 August 2012
* Affected product: LibreOffice < 3.5.5
                    Apache OpenOffice <= 3.4.0
* Impact: code execution
* Origin: encrypted office files
* CVSS Base Score: 9.3
    Impact Subscore: 10
    Exploitability Subscore: 8.6
  CVSS Vector: (AV:N/AC:M/Au:N/C:C/I:C/A:C)
* Credit: Timo Warns (PRESENSE Technologies GmbH)
* CVE Identifier: CVE-2012-2665


Summary
-------

Multiple issues have been identified in LibreOffice / OpenOffice that
allow to execute arbitrary code via specially crafted office files.

    Elements outside expected parent elements
    -----------------------------------------

    Initially, the aSequence attribute of a ManifestImport instance has
    no memory allocated for PropertyValue elements.
    ManifestImport::startElement() (re)allocates memory when
    a "manifest:file-entry" XML element is encountered in the manifest
    file. The property values are, for example, accessed when
    a "manifest:encryption-data" XML element is found. If such
    elements are located outside an expected parent element
    "manifest:file-entry", ManifestImport::startElement() accesses
    aSequence out-of-bounds.


    Writes beyond fixed size buffer
    -------------------------------

    ManifestImport::startElement() allocates memory for 12 (=
    PKG_SIZE_ENCR_MNFST) PropertValue elements. If
    a "manifest:file-entry" XML element has child elements that cause
    startElement() to access more than 12 PropertValues, startElement()
    accesses aSequence out-of-bounds.


    Base64Codec::decodeBase64()
    ---------------------------

    ManifestImport::startElement() calls Base64Codec::decodeBase64() to
    decode the XML attributes for checksums, initialization vectors, and
    salt values. Base64Codec::decodeBase64() implicitly assumes that the
    source buffer sBuffer contains a number of characters divisible by 4.
    If this is not the case, the called method FourByteToThreeByte()
    writes up to 3 bytes past a buffer allocated on the heap.


Solution
--------

The issue has been fixed in LibreOffice 3.5.5.
An update to Apache OpenOffice is pending.


References
----------

http://www.libreoffice.org/advisories/CVE-2012-2665/
https://bugzilla.redhat.com/show_bug.cgi?id=826077

When further information becomes available, this advisory will be
updated. The most recent version of this advisory is available at:

http://www.pre-cert.de/advisories/PRE-SA-2012-05.txt


Contact
--------

PRE-CERT can be reached under precert@...-secure.de. For PGP key
information, refer to http://www.pre-cert.de/.