Multiple Unix/Linux Vendor Xpdf makeFileKey2 Stack Overflow iDEFENSE Security Advisory 01.18.05 http://www.idefense.com/application/poi/display?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, GString *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 01/06/2004 Initial vendor notification 01/12/2004 Initial vendor response 01/18/2004 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
Multiple Unix/Linux Vendor Xpdf makeFileKey2 Stack Overflow iDEFENSE Security Advisory 01.18.05 http://www.idefense.com/application/poi/display?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, GString *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 01/06/2004 Initial vendor notification 01/12/2004 Initial vendor response 01/18/2004 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 © 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.
declassifying signoff=jaervosz/koon Waiting for more definitive patch
Created attachment 48566 [details, diff] CAN-2005-0064.patch Patch from RedHat
Heinrich Wendel (lanius) is the man for this one. adding him to the CC:
Heinrich: An official patch will be available on the 18th (see url above), but if we can prepare and arch-test another one in the meantime, all the better. We can't commit this to portage until it's public, so please attach the ebuild to the bug so that we let arches test from here.
Created attachment 48638 [details] xpdf-3.00-r8.ebuild download the patch into your filesdirectory and use this ebuild
Arches, please test attached ebuild and report success. This is still confidential until the 18th, we'll try to commit it directly to stable if possible. Calling: for sparc: fmccor@gentoo.org & weeve@gentoo.org for amd64: kugelfang@gentoo.org & blubb@gentoo.org for ppc64: corsair@gentoo.org for alpha: kloeri@gentoo.org for ppc: SeJo@gentoo.org
works on ppc64
Successfully tested on amd64.
Installs on sparc and seems to work fine for me.
Fine on alpha.
This is going public sometime today, ppc testing is still needed.
OK apparently this patch is not sufficient. We'll just wait for the upstream official patch... sorry for wasting your time, folks.
commited with "alpha amd64 ~hppa ~ia64 ~ppc ppc64 sparc x86"
ok, removed the commit again
Heinrich: keep the engine running, you will have a lot to commit tonight !
[ http://www.idefense.com/application/poi/display?id=186 ] This issue is now public.
Do kdegraphics/koffice get their own bugs or did you forget us!? ;)
@comment #17 We didn't forget just waited until public disclosure. I've just opend up bug #78619 and bug #78620
Created attachment 48920 [details, diff] xpdf-3.00pl3.patch Upstream patch
Heinrich: Please bump in Portage using the official patch
commited
Arches please test & mark 3.00-r8 stable Target KEYWORDS="alpha amd64 hppa ia64 ppc ppc64 sparc x86"
Stable for sparc. Installs and tests as good.
Stable on amd64
Stable on ppc.
Stable on alpha.
stable on ppc64
corsair: ppc64 stable marking doesn't show in KEYWORDS
sorry, now it is definetly marked stable on ppc64
GLSA 200501-28 hppa, ia64 please mark stable to benefit from GLSA
Already stable on hppa
