Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2005.0055 -- iDEFENSE Security Advisory 01.18.05 Multiple Unix/Linux Vendor Xpdf makeFileKey2 Stack Overflow 19 January 2005 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Xpdf Publisher: iDEFENSE Operating System: BSD variants Linux variants UNIX variants Impact: Execute Arbitrary Code/Commands Access: Remote/Unauthenticated CVE Names: CAN-2005-0064 Original Bulletin: http://www.idefense.com/application/poi/display?id=186 - --------------------------BEGIN INCLUDED TEXT-------------------- 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. - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 If you believe that your computer system has been compromised or attacked in any way, we encourage you to let us know by completing the secure National IT Incident Reporting Form at: http://www.auscert.org.au/render.html?it=3192 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQCVAwUBQe28/ih9+71yA2DNAQLADwP+L4s0O8kQyDNr5u7ANEvQKJB7hTpLbeXB sTgUE0t3+tJmp8W40bjNABuLFJvrEtDgSjxbF203tdxgexA3XUvsaLCAuAACMiEe 6qmXZRCGYqVGJgqYAq5VXwG2t1EE4U2vwxLEB4G5Q/ogdNj2eTxHMEpj+S6Nj4I7 lZ/7nvas+8c= =YXFy -----END PGP SIGNATURE-----