password_compat
===============

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This library is intended to provide forward compatibility with the password_* functions being worked on for PHP 5.5.

See [the RFC](https://wiki.php.net/rfc/password_hash) for more detailed information.


Requirements
============

This library requires `PHP >= 5.3.7` OR a version that has the `$2y` fix backported into it (such as Debian provides).

The runtime checks have been removed due to this version issue. To see if password_compat is available for your system, run the included `version-test.php`. If it outputs "Pass", you can safely use the library. If not, you cannot. 

If you attempt to use password-compat on an unsupported version, attempts to create or verify hashes will return `false`. You have been warned!

The reason for this is that PHP prior to 5.3.7 contains a security issue with its BCRYPT implementation. Therefore, it's highly recommended that you upgrade to a newer version of PHP prior to using this layer.

Installation
============

To install, simply `require` the `password.php` file under `lib`. 

You can also install it via `Composer` by using the [Packagist archive](http://packagist.org/packages/ircmaxell/password-compat).

Usage
=====

**Creating Password Hashes**

To create a password hash from a password, simply use the `password_hash` function.

    $hash = password_hash($password, PASSWORD_BCRYPT);

Note that the algorithm that we chose is `PASSWORD_BCRYPT`. That's the current strongest algorithm supported. This is the `BCRYPT` crypt algorithm. It produces a 60 character hash as the result.

`BCRYPT` also allows for you to define a `cost` parameter in the options array. This allows for you to change the CPU cost of the algorithm:

    $hash = password_hash($password, PASSWORD_BCRYPT, ["cost" => 10]);

That's the same as the default. The cost can range from `4` to `31`. I would suggest that you use the highest cost that you can, while keeping response time reasonable (I target between 0.1 and 0.5 seconds for a hash, depending on use-case).

Another algorithm name is supported:

    PASSWORD_DEFAULT

This will use the strongest algorithm available to PHP at the current time. Presently, this is the same as specifying `PASSWORD_BCRYPT`. But in future versions of PHP, it may be updated to use a stronger algorithm if one is introduced. It can also be changed if a problem is identified with the BCRYPT algorithm. Note that if you use this option, you are **strongly** encouraged to store it in a `VARCHAR(255)` column to avoid truncation issues if a future algorithm increases the length of the generated hash.

It is very important that you should check the return value of `password_hash` prior to storing it, because a `false` may be returned if it encountered an error.

**Verifying Password Hashes**

To verify a hash created by `password_hash`, simply call:

	if (password_verify($password, $hash)) {
		/* Valid */
	} else {
		/* Invalid */
	}

That's all there is to it.

**Rehashing Passwords**

From time to time you may update your hashing parameters (algorithm, cost, etc). So a function to determine if rehashing is necessary is available:

    if (password_verify($password, $hash)) {
		if (password_needs_rehash($hash, $algorithm, $options)) {
			$hash = password_hash($password, $algorithm, $options);
			/* Store new hash in db */
		}
	}