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Category:   Application (Generic)  >   Xpdf Vendors:   Glyph and Cog
Xpdf Buffer Overflow in makeFileKey2() Lets Remote Users Execute Arbitrary Code
SecurityTracker Alert ID:  1012936
SecurityTracker URL:  http://securitytracker.com/id/1012936
CVE Reference:   CVE-2005-0064   (Links to External Site)
Date:  Jan 19 2005
Impact:   Execution of arbitrary code via network, User access via network

Version(s): prior to 3.00pl3
Description:   iDEFENSE reported a buffer overflow vulnerability in Xpdf. A remote user may be able to execute arbitrary code on the target system.

A remote user can create a specially crafted PDF file to trigger a stack overflow in the 'Decrypt::makeFileKey2' function in the processing of the /Encrypt /Length tag. Arbitrary code can be executed with the privileges of the Xpdf process or the user running Xpdf.

The flaw resides in 'xpdf/Decrypt.cc'.

The vendor was notified on January 6, 2005.

The original advisory is available at:

http://www.idefense.com/application/poi/display?id=186&type=vulnerabilities

Impact:   A remote user can create a PDF file that, when processed by Xpdf, will execute arbitrary code on the target system. The code will run with the privileges of Xpdf.
Solution:   The vendor has issued a fixed version (3.00pl3), available at:

http://www.foolabs.com/xpdf/download.html

A patch is also available at:

ftp://ftp.foolabs.com/pub/xpdf/xpdf-3.00pl3.patch

Vendor URL:  www.foolabs.com/xpdf/ (Links to External Site)
Cause:   Boundary error
Underlying OS:  Linux (Any), UNIX (Any)

Message History:   This archive entry has one or more follow-up message(s) listed below.
Jan 19 2005 (Debian Issues Fix for CUPS) Xpdf Buffer Overflow in makeFileKey2() Lets Remote Users Execute Arbitrary Code
Debian has released a fix for CUPS.
Jan 19 2005 (Debian Issues Fix) Xpdf Buffer Overflow in makeFileKey2() Lets Remote Users Execute Arbitrary Code
Debian has released a fix.
Jan 19 2005 (KDE Issues Fix for kpdf) Xpdf Buffer Overflow in makeFileKey2() Lets Remote Users Execute Arbitrary Code
KDE has issued a fix for kpdf.
Jan 24 2005 (Gentoo Issues Fix for KDE Kpdf and KOffice) Xpdf Buffer Overflow in makeFileKey2() Lets Remote Users Execute Arbitrary Code
Gentoo has released a fix for KDE Kpdf and KOffice.
Feb 2 2005 (Red Hat Issues Fix) Xpdf Buffer Overflow in makeFileKey2() Lets Remote Users Execute Arbitrary Code
Red Hat has released a fix.
Mar 19 2005 (Red Hat Issues Fix for teTeX) Xpdf Buffer Overflow in makeFileKey2() Lets Remote Users Execute Arbitrary Code
Red Hat has released a fix for teTeX.
Jun 10 2005 (Libextractor Issues Fix) Xpdf Buffer Overflow in makeFileKey2() Lets Remote Users Execute Arbitrary Code
A fix is available for libextractor, which is affected by the Xpdf vulnerability.



 Source Message Contents

Subject:  iDEFENSE Security Advisory 01.18.05: Multiple Unix/Linux Vendor


Multiple Unix/Linux Vendor Xpdf makeFileKey2 Stack Overflow 

iDEFENSE Security Advisory 01.18.05
www.idefense.com/application/poi/display?id=186&type=vulnerabilities
January 18, 2005

I. BACKGROUND

Xpdf is an open-source viewer for PDF files. More information is 
available at the following site:

http://www.foolabs.com/xpdf/

II. DESCRIPTION

Remote exploitation of a buffer overflow vulnerability in the xpdf PDF 
viewer included in multiple Unix and Linux distributions could allow for

arbitrary code execution as the user viewing a PDF file. 

The vulnerability specifically exists due to insufficient bounds 
checking while processing a PDF file that provides malicious values in 
the /Encrypt /Length tag. The offending code can be found in the 
Decrypt::makeFileKey2 function in the source file xpdf/Decrypt.cc. 

GBool Decrypt::makeFileKey2(int encVersion, int encRevision,
                            int keyLength, GString *ownerKey,
                            GString *userKey, int permissions,
                            GString *fileID, String *userPassword,
                            Guchar *fileKey) {
      Guchar *buf;
      Guchar test[32];
      Guchar fState[256];
      Guchar tmpKey[16];
      Guchar fx, fy;
      int len, i, j;
      GBool ok;
      ...

            memcpy(test, userKey->getCString(), 32);
            for (i = 19; i >= 0; --i) {
                  for (j = 0; j < keyLength; ++j) {
[overflow]               tmpKey[j] = fileKey[j] ^ i; 
                  }
            ...
      }
      ...
} 

In this piece of code, the keyLength value is ultimately supplied by the

PDF file. This allows an attacker to specify an arbitrarily large value 
and overwrite portions of stack memory. As a consequence, arbitrary code

execution is possible.

III. ANALYSIS

Successful exploitation of this vulnerability leads to arbitrary code 
execution as the user who opened the malicious file. An attacker would 
have to convince a target to open the provided file in order to exploit 
this vulnerability, thus lessening the impact.

Exploitation can be performed reliably, especially with knowledge of the

target system.

IV. DETECTION

iDEFENSE has confirmed the existence of this vulnerability in version 
3.00 of xpdf. It is suspected previous versions are vulnerable. 

The following Linux vendors may be affected by this vulnerability:

	Novell Inc. (SUSE) 
	Red Hat Inc. 
	The Fedora Project 
	Debian Project 
	Gentoo Foundation Inc. 
	The FreeBSD Project 
	OpenBSD 

V. WORKAROUND

Only open PDF files from trusted individuals.

VI. VENDOR RESPONSE

A patch to address this issue is available at:

    ftp://ftp.foolabs.com/pub/xpdf/xpdf-3.00pl3.patch

Updated binaries (ver. 3.00pl3) to address this issue are available at:

    http://www.foolabs.com/xpdf/download.html

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2005-0064 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

01/06/2005  Initial vendor notification
01/12/2005  Initial vendor response
01/18/2005  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

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@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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