Secure password hashing with bCrypt

In this article I will show you how to implement a secure password hashing mechanism in your Yii projects using a bCrypt class.

The inspiration for this wiki came from this discussion on StackOverflow.

bCrypt Class - Save in /protected/vendors
class bCrypt {
  private $rounds;
  private $prefix;
  
  public function __construct($prefix = '', $rounds = 12) {
    if(CRYPT_BLOWFISH != 1) {
      throw new Exception("bcrypt not supported in this installation. See http://php.net/crypt");
    }

    $this->rounds = $rounds;
    $this->prefix = $prefix;
  }

  public function hash($input) {
    $hash = crypt($input, $this->getSalt());

    if(strlen($hash) > 13)
      return $hash;

    return false;
  }

  public function verify($input, $existingHash) {
    $hash = crypt($input, $existingHash);

    return $hash === $existingHash;
  }

  private function getSalt() {
    // the base64 function uses +'s and ending ='s; translate the first, and cut out the latter
    return sprintf('$2a$%02d$%s', $this->rounds, substr(strtr(base64_encode($this->getBytes()), '+', '.'), 0, 22));
  }
  
  private function getBytes() {
    $bytes = '';

    if(function_exists('openssl_random_pseudo_bytes') &&
        (strtoupper(substr(PHP_OS, 0, 3)) !== 'WIN')) { // OpenSSL slow on Win
      $bytes = openssl_random_pseudo_bytes(18);
    }

    if($bytes === '' && is_readable('/dev/urandom') &&
       ($hRand = @fopen('/dev/urandom', 'rb')) !== FALSE) {
      $bytes = fread($hRand, 18);
      fclose($hRand);
    }
    
    if($bytes === '') {
      $key = uniqid($this->prefix, true);
      
      // 12 rounds of HMAC must be reproduced / created verbatim, no known shortcuts.
      // Salsa20 returns more than enough bytes.
      for($i = 0; $i < 12; $i++) {
        $bytes = hash_hmac('sha512', microtime() . $bytes, $key, true);
        usleep(10);
      }
    }
	return $bytes;
  }
}

?>
Edit main.cfg config file
'import'=>array(
		'application.vendors.*'
	),
User Model
protected function afterValidate()
	{
		$this->password = $this->encrypt($this->password);
		return parent::afterValidate();
	}

	public function encrypt($value)
	{
	$enc = NEW bCrypt();
	    return $enc->hash($value);
	}
UserIdentity - Modify password check to the following static method:
} else if (!bCrypt::verify($this->password, $user->password)) {
			$this->errorCode=self::ERROR_PASSWORD_INVALID;

Discussion

How does this work?

By hooking into the User model's afterValidate() method we can drop in this code without any major changes to the UserIdentity or other components. What happens is that when your login form is submitted the inputs are validated (username, password). If they pass validation, the password value gets sent through the encrypt function and returned as a hash for database comparison.

The only remaining work to do is to ensure that your password field in the database is large enough to hold the values. I recommend using char(60) as field type.

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Viewed: 25 861 times
Version: 1.1
Category: How-tos
Written by: waitforit
Last updated by: Ivo Pereira
Created on: Dec 20, 2011
Last updated: 5 years ago
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