iDEFENSE Security Advisory 03.01.05: RealNetworks RealPlayer .smil Buffer Overflow Vulnerability

["Michael Sutton" <msutton@xxxxxxxxxxxx>]

RealNetworks RealPlayer .smil Buffer Overflow Vulnerability

iDEFENSE Security Advisory 03.01.05
www.idefense.com/application/poi/display?id=209&type=vulnerabilities
March 1, 2005

I. BACKGROUND

RealPlayer is an application for playing various media formats,
developed by RealNetworks Inc. For more information, visit
http://www.real.com/.

II. DESCRIPTION

Remote exploitation of a stack-based buffer overflow vulnerability in
the The Synchronized Multimedia Integration Language (smil) file format
parser within various versions of RealNetworks Inc.'s RealPlayer could
allow attackers to execute arbitrary code.

The vulnerability specifically exists due to an unbounded string copying
operation. The vulnerable code is shown below:

datatype/smil/renderer/smil1/smlparse.cpp
CSmil1Parser::testAttributeFailed(SMIL1Node* pNode)
line 2878
***
     if(HXR_OK == rc)
        {
            UINT32 ulScreenHeight = 0;
            UINT32 ulScreenWidth = 0;

            const char* pScreenSize = (const char*)pBuf->GetBuffer();
            // format is screen-height "X" screen-width
            char tmp[256]; /* Flawfinder: ignore */
            strcpy(tmp, pScreenSize); /* Flawfinder: ignore */
***


The pBuf object's datapointer (which is what GetBuffer uses internally)
is pointing at the screen-size attribute in the user-supplied smil file.
This allows a fixed stack buffer to be overwritten with user-supplied
data. An attacker could use this stack overwrite to manipulate a saved
return address or Structured Exception Handler, allowing for arbitrary
code execution.

In order to trigger this vulnerability, one would need an otherwise
valid .smil file with the following line added in an appropriate
section: <text src="1024_768.en.txt" region="size" system-screen-
size="LONGSTRINGX768">

Note that "LONGSTRING" should be more than 256 bytes in order to cause
stack corruption.

III. ANALYSIS

Exploitation allows for arbitrary code execution as the user who opened
the .smil file.

Exploitation requires an attacker to craft a malicious .smil and
convince a user to open it. An attacker could also force a web browser
to refresh and automatically load the .smil file from a normal web page
under the attacker's control. In default installations of RealPlayer
under Windows, Internet Explorer will not prompt the user for an action
when encountering a .smil file. It will open it without delay, thus
allowing a more effective method of exploitation.

IV. DETECTION

iDEFENSE Labs has confirmed that Real Networks Inc.'s RealPlayer 10.5
(6.0.12.1056) on Windows and RealPlayer 10 (10.0.1.436) on Linux are
vulnerable.

The vendor has reported that the following products are vulnerable on
the following platforms:

Windows:
        RealPlayer 10.5 (6.0.12.1056 and below)
        RealPlayer 10
        RealOne Player V2
        RealOne Player V1
        RealPlayer 8
        RealPlayer Enterprise

Mac
        RealPlayer 10 (10.0.0.325 and below)
        RealOne Player

Linux
        RealPlayer 10
        Helix Player

V. WORKAROUND

There are no known workarounds for this vulnerability. Although .smil
files can be disassociated from RealPlayer, it is still possible to
cause these files to load with RealPlayer using other methods. One such
method is loading the file via one of the many ActiveX Controls that
RealPlayer contains. Any effective workaround would prevent RealPlayer
from functioning.

VI. VENDOR RESPONSE

A vendor advisory for this issue is available at:

   http://service.real.com/help/faq/security/050224_player

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2005-0455 to these issues. This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

VIII. DISCLOSURE TIMELINE

01/14/2005  Initial vendor notification
01/19/2005  Initial vendor response
03/01/2005  Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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

Free tools, research and upcoming events
http://labs.idefense.com

X. LEGAL NOTICES

Copyright (c) 2005 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@xxxxxxxxxxxx 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.