[VulnWatch] iDEFENSE Security Advisory 12.21.04: libtiff STRIPOFFSETS Integer Overflow Vulnerability

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Date: 12/21/04

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    libtiff STRIPOFFSETS Integer Overflow Vulnerability

    iDEFENSE Security Advisory 12.21.04
    www.idefense.com/application/poi/display?id=173&type=vulnerabilities
    December 21, 2004

    I. BACKGROUND

    libtiff provides support for the Tag Image File Format (TIFF), a widely
    used format for storing image data.

    More information is available at the following site:
    http://www.remotesensing.org/libtiff/

    II. DESCRIPTION

    Remote exploitation of an integer overflow in libtiff may allow for the
    execution of arbitrary code.

    The overflow occurs in the parsing of TIFF files set with the
    STRIPOFFSETS flag in libtiff/tif_dirread.c. In the TIFFFetchStripThing()

    function, the number of strips (nstrips) is used directly in a
    CheckMalloc() routine without sanity checking. The call ultimately boils

    down to:

    malloc(user_supplied_int*size(int32));

    When supplied 0x40000000 as the user supplied integer, malloc is called
    with a length argument of 0. This has the effect of returning the
    smallest possible malloc chunk. A user controlled buffer is subsequently

    copied to that small heap buffer, causing a heap overflow.

    When exploited, it is possible to overwrite heap structures and seize
    control of execution.

    III. ANALYSIS

    An attacker can exploit the above-described vulnerability to execute
    arbitrary code under the permissions of the target user. Successful
    exploitation requires that the attacker convince the end user to open
    the malicious TIFF file using an application linked with a vulnerable
    version of libtiff. Exploitation of this vulnerability against a remote
    target is difficult because of the precision required in the attack.

    IV. DETECTION

    iDEFENSE has confirmed this vulnerability in libtiff 3.6.1. Changes were

    introduced in libtiff 3.7.0 that had the effect of fixing this
    vulnerability.

    The following vendors provide susceptible libtiff packages within their
    respective operating system distributions:
            
            - Gentoo Linux
            - Fedora Linux
            - RedHat Linux
            - SuSE Linux
            - Debian Linux

    V. WORKAROUND

    Only open TIFF files from trusted users.

    VI. VENDOR RESPONSE

    This issue is addressed in libtiff 3.7.0 and 3.7.1.

    VII. CVE INFORMATION

    A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
    been assigned yet.

    VIII. DISCLOSURE TIMELINE

    12/15/2004 Discovery of fix in later software version
    12/21/2004 Public disclosure

    IX. CREDIT

    infamous41md[at]hotpop.com is credited with this discovery.

    Get paid for vulnerability research
    http://www.idefense.com/poi/teams/vcp.jsp

    X. LEGAL NOTICES

    Copyright (c) 2004 iDEFENSE, Inc.

    Permission is granted for the redistribution of this alert
    electronically. It may not be edited in any way without the express
    written consent of iDEFENSE. If you wish to reprint the whole or any
    part of this alert in any other medium other than electronically, please
    email customerservice@idefense.com for permission.

    Disclaimer: The information in the advisory is believed to be accurate
    at the time of publishing based on currently available information. Use
    of the information constitutes acceptance for use in an AS IS condition.
    There are no warranties with regard to this information. Neither the
    author nor the publisher accepts any liability for any direct, indirect,
    or consequential loss or damage arising from use of, or reliance on,
    this information.


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