# PHP Juggling type and magic hashes

PHP provides two ways to compare two variables:

- Loose comparison using `== or !=` : both variables have "the same value".
- Strict comparison using `=== or !==` : both variables have "the same type and the same value".

## Type Juggling

### True statements

```php
var_dump('0010e2'   == '1e3');           # true
var_dump('0xABCdef' == ' 0xABCdef');     # true PHP 5.0 / false PHP 7.0
var_dump('0xABCdef' == '     0xABCdef'); # true PHP 5.0 / false PHP 7.0
var_dump('0x01'     == 1)                # true PHP 5.0 / false PHP 7.0
var_dump('0x1234Ab' == '1193131');
```

```php
'123'  == 123
'123a' == 123
'abc'  == 0
```

```php
'' == 0 == false == NULL
'' == 0       # true
0  == false   # true
false == NULL # true
NULL == ''    # true
```

### NULL statements

```php
var_dump(sha1([])); # NULL
var_dump(md5([]));  # NULL
```

## Magic Hashes - Exploit

If the hash computed starts with "0e" (or "0..0e") only followed by numbers, PHP will treat the hash as a float.

| Hash | “Magic” Number / String    | Magic Hash                                    | Found By      |
| ---- | -------------------------- |:---------------------------------------------:| -------------:|
| MD5  | 240610708                  | 0e462097431906509019562988736854              | Michal Spacek |
| SHA1 | 10932435112                | 0e07766915004133176347055865026311692244      | Independently found by Michael A. Cleverly & Michele Spagnuolo & Rogdham |

```php
<?php
var_dump(md5('240610708') == md5('QNKCDZO')); # bool(true)
var_dump(md5('aabg7XSs')  == md5('aabC9RqS'));
var_dump(sha1('aaroZmOk') == sha1('aaK1STfY'));
var_dump(sha1('aaO8zKZF') == sha1('aa3OFF9m'));
?>
```

## Thanks to

* [Writing Exploits For Exotic Bug Classes: PHP Type Juggling By Tyler Borland](http://turbochaos.blogspot.com/2013/08/exploiting-exotic-bugs-php-type-juggling.html)
* [Magic Hashes - WhieHatSec](https://www.whitehatsec.com/blog/magic-hashes/)