[Fwd: Buffer Overflow in NVIDIA Binary Graphics Driver For Linux (with exploit)]

[Matthieu Herrb]

-------- Original Message --------
Subject: Buffer Overflow in NVIDIA Binary Graphics Driver For Linux 
(with exploit)
Date: Mon, 16 Oct 2006 13:09:14 -0700
From: Chad Loder <cloder at openbsd.org>
To: matthieu at openbsd.org

Hello Mattthieu.

I know you are involved with X.org security, so I thought you should 
know about this
security advisory in the NVIDIA binary blob driver for X that we 
published today, along
with a working root exploit.

PS: We actually used one of your example X programs as a basis to 
initialize the X
rendering environment for our exploit. You will see your name on the 
copyright of
the exploit code, please do not be offended. :)

Best,
	Chad Loder

---
Rapid7 Advisory R7-0025
Buffer Overflow in NVIDIA Binary Graphics Driver For Linux

    Published:  Oct 16, 2006
    Revision:   1.0
    http://www.rapid7.com/advisories/R7-0025.jsp

1. Affected system(s):

    KNOWN VULNERABLE:
     o NVIDIA Driver For Linux v8774
     o NVIDIA Driver For Linux v8762

    PROBABLY VULNERABLE:
     o NVIDIA Driver for FreeBSD
     o NVIDIA Driver for Solaris
     o Earlier versions

    KNOWN FIXED:
     o None

2. Summary

    The NVIDIA Binary Graphics Driver for Linux is vulnerable to a
    buffer overflow that allows an attacker to run arbitrary code as
    root. This bug can be exploited both locally or remotely (via
    a remote X client or an X client which visits a malicious web page).
    A working proof-of-concept root exploit is included with this
    advisory.

    The NVIDIA drivers for Solaris and FreeBSD are also likely to be
    vulnerable.

3. Vendor status and information

    NVIDIA Corporation
    http://www.nvidia.com

    There have been multiple public reports of this NVIDIA bug on the
    NVNews forum [1,2] and elsewhere, dating back to 2004 [3]. NVIDIA's
    first public acknowledgement of this bug was on July 7th, 2006. In a
    public posting [1] on the NVNews forum, an NVIDIA employee reported
    having reproduced the problem, assigned it bug ID 239065, and promised
    a fix would be forthcoming.

    As of the publication date, the latest NVIDIA binary driver is still
    vulnerable. Furthermore, it is our opinion that NVIDIA's binary driver
    remains an unacceptable security risk based on the large numbers of
    reproducible, unfixed crashes that have been reported in public forums
    and bug databases. This number does not include bugs reported directly
    to NVIDIA.

    1. http://www.nvnews.net/vbulletin/showthread.php?p=931048   (Jul 2006)
    2. http://www.nvnews.net/vbulletin/showthread.php?t=76493    (Sep 2006)
    3. https://bugs.freedesktop.org/show_bug.cgi?id=2129         (Dec 2004)
    4. http://lists.freedesktop.org/archives/xorg/2005-January/005642.html
    5. http://forums.gentoo.org/viewtopic.php?t=282107           (Jan 2005)
    6. https://bugs.eclipse.org/bugs/show_bug.cgi?id=87299       (Mar 2005)
    7. http://www.nvnews.net/vbulletin/showthread.php?t=76206    (Sep 2006)

4. Solution

    Disable the binary blob driver and use the open-source "nv" driver
    that is included by default with X.

5. Detailed analysis

    There are two NVIDIA graphics drivers for Linux: a closed-source
    binary blob driver provided by NVIDIA (which provides acceleration)
    and an open-source driver (which lacks acceleration). NVIDIA's
    binary blob driver contains an error in its accelerated rendering
    of glyphs (text character data) that can be exploited to write
    arbitrary data to anywhere in memory. The open-source driver is
    not vulnerable.

    The XRender extension provides a client function named
    XRenderCompositeString8 which tells the X server to render glyphs
    onto the screen. This request is processed by the server's
    ProcRenderCompositeGlpyhs function. This function pulls the glyphs
    out of the render request, constructs a glyph list, and then calls
    into the graphics driver via a registered callback function.

    The NVIDIA binary blob driver registers a function named _nv000373X.
    This function calculates a bounding BoxRec of the total area occupied
    by the glyph data. It then uses Xalloc to allocate a buffer large
    enough to hold the data by multiplying width * height. This buffer
    is then passed to another internal function called _nv000053X.

    The _nv000053X function iterates over the glyph list and copies
    glyph data into the buffer using each glyph's accumulated width,
    xOff, height, and yOff values to calculate the destination position
    in the buffer. The NVIDIA binary blob driver does not check this
    calculation against the size of the allocated buffer. As a result,
    a short sequence of user-supplied glyphs can be used to trick the
    function into writing to an arbitrary location in memory.

    It is important to note that glyph data is supplied to the X server
    by the X client. Any remote X client can gain root privileges on
    the X server using the proof of concept program attached.

    It is also trivial to exploit this vulnerability as a DoS by causing
    an existing X client program (such as Firefox) to render a long text
    string. It may be possible to use Flash movies, Java applets, or
    embedded web fonts to supply the custom glyph data necessary for
    reliable remote code execution.

    A simple HTML page containing an INPUT field with a long value is
    sufficient to demonstrate the DoS.

5. Credit

    This vulnerability was discovered by Derek Abdine of Rapid7. Special
    thanks to Marc Bevand for his assistance.

6. Contact Information

    Rapid7, LLC
    Email: advisory at rapid7.com
    Web: http://www.rapid7.com
    Phone: +1 (310) 316-1235

7. Disclaimer and Copyright

    Rapid7, LLC is not responsible for the misuse of the information
    provided in our security advisories. These advisories are a service
    to the professional security community. There are NO WARRANTIES with
    regard to this information. Any application or distribution of this
    information constitutes acceptance AS IS, at the user's own risk.
    This information is subject to change without notice.

    This advisory Copyright (C) 2006 Rapid7, LLC. Permission is hereby
    granted to redistribute this advisory, providing that no changes are
    made and that the copyright notices and disclaimers remain intact.



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