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<?php
/**
* SecurityHelper class file.
*
* @link http://www.yiiframework.com/
* @copyright Copyright &copy; 2008 Yii Software LLC
* @license http://www.yiiframework.com/license/
*/
namespace yii\util;
use Yii;
use yii\base\Exception;
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use yii\base\InvalidConfigException;
use yii\base\InvalidParamException;
/**
* SecurityHelper provides a set of methods to handle common security-related tasks.
*
* In particular, SecurityHelper supports the following features:
*
* - Encryption/decryption: [[encrypt()]] and [[decrypt()]]
* - Data tampering prevention: [[hashData()]] and [[validateData()]]
* - Password validation: [[generatePasswordHash()]] and [[validatePassword()]]
*
* Additionally, SecurityHelper provides [[getSecretKey()]] to support generating
* named secret keys. These secret keys, once generated, will be stored in a file
* and made available in future requests.
*
* @author Qiang Xue <qiang.xue@gmail.com>
* @author Tom Worster <fsb@thefsb.org>
* @since 2.0
*/
class SecurityHelper
{
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/**
* Encrypts data.
* @param string $data data to be encrypted.
* @param string $key the encryption secret key
* @return string the encrypted data
* @throws Exception if PHP Mcrypt extension is not loaded or failed to be initialized
* @see decrypt()
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*/
public static function encrypt($data, $key)
{
$module = static::openCryptModule();
$key = StringHelper::substr($key, 0, mcrypt_enc_get_key_size($module));
srand();
$iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($module), MCRYPT_RAND);
mcrypt_generic_init($module, $key, $iv);
$encrypted = $iv . mcrypt_generic($module, $data);
mcrypt_generic_deinit($module);
mcrypt_module_close($module);
return $encrypted;
}
/**
* Decrypts data
* @param string $data data to be decrypted.
* @param string $key the decryption secret key
* @return string the decrypted data
* @throws Exception if PHP Mcrypt extension is not loaded or failed to be initialized
* @see encrypt()
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*/
public static function decrypt($data, $key)
{
$module = static::openCryptModule();
$key = StringHelper::substr($key, 0, mcrypt_enc_get_key_size($module));
$ivSize = mcrypt_enc_get_iv_size($module);
$iv = StringHelper::substr($data, 0, $ivSize);
mcrypt_generic_init($module, $key, $iv);
$decrypted = mdecrypt_generic($module, StringHelper::substr($data, $ivSize, StringHelper::strlen($data)));
mcrypt_generic_deinit($module);
mcrypt_module_close($module);
return rtrim($decrypted, "\0");
}
/**
* Prefixes data with a keyed hash value so that it can later be detected if it is tampered.
* @param string $data the data to be protected
* @param string $key the secret key to be used for generating hash
* @param string $algorithm the hashing algorithm (e.g. "md5", "sha1", "sha256", etc.). Call PHP "hash_algos()"
* function to see the supported hashing algorithms on your system.
* @return string the data prefixed with the keyed hash
* @see validateData()
* @see getSecretKey()
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*/
public static function hashData($data, $key, $algorithm = 'sha256')
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{
return hash_hmac($algorithm, $data, $key) . $data;
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}
/**
* Validates if the given data is tampered.
* @param string $data the data to be validated. The data must be previously
* generated by [[hashData()]].
* @param string $key the secret key that was previously used to generate the hash for the data in [[hashData()]].
* @param string $algorithm the hashing algorithm (e.g. "md5", "sha1", "sha256", etc.). Call PHP "hash_algos()"
* function to see the supported hashing algorithms on your system. This must be the same
* as the value passed to [[hashData()]] when generating the hash for the data.
* @return string the real data with the hash stripped off. False if the data is tampered.
* @see hashData()
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*/
public static function validateData($data, $key, $algorithm = 'sha256')
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{
$hashSize = StringHelper::strlen(hash_hmac($algorithm, 'test', $key));
$n = StringHelper::strlen($data);
if ($n >= $hashSize) {
$hash = StringHelper::substr($data, 0, $hashSize);
$data2 = StringHelper::substr($data, $hashSize, $n - $hashSize);
return $hash === hash_hmac($algorithm, $data2, $key) ? $data2 : false;
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} else {
return false;
}
}
/**
* Returns a secret key associated with the specified name.
* If the secret key does not exist, a random key will be generated
* and saved in the file "keys.php" under the application's runtime directory
* so that the same secret key can be returned in future requests.
* @param string $name the name that is associated with the secret key
* @param integer $length the length of the key that should be generated if not exists
* @return string the secret key associated with the specified name
*/
public static function getSecretKey($name, $length = 32)
{
static $keys;
$keyFile = Yii::$app->getRuntimePath() . '/keys.php';
if ($keys === null) {
$keys = is_file($keyFile) ? require($keyFile) : array();
}
if (!isset($keys[$name])) {
// generate a 32-char random key
$chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
$keys[$name] = substr(str_shuffle(str_repeat($chars, 5)), 0, $length);
file_put_contents($keyFile, "<?php\nreturn " . var_export($keys, true) . ";\n");
}
return $keys[$name];
}
/**
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* Opens the mcrypt module.
* @return resource the mcrypt module handle.
* @throws InvalidConfigException if mcrypt extension is not installed
* @throws Exception if mcrypt initialization fails
*/
protected static function openCryptModule()
{
if (!extension_loaded('mcrypt')) {
throw new InvalidConfigException('The mcrypt PHP extension is not installed.');
}
$module = @mcrypt_module_open('rijndael-256', '', MCRYPT_MODE_CBC, '');
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if ($module === false) {
throw new Exception('Failed to initialize the mcrypt module.');
}
return $module;
}
/**
* Generates a secure hash from a password and a random salt.
*
* The generated hash can be stored in database (e.g. `CHAR(64) CHARACTER SET latin1` on MySQL).
* Later when a password needs to be validated, the hash can be fetched and passed
* to [[validatePassword()]]. For example,
*
* ~~~
* // generates the hash (usually done during user registration or when the password is changed)
* $hash = SecurityHelper::hashPassword($password);
* // ...save $hash in database...
*
* // during login, validate if the password entered is correct using $hash fetched from database
* if (PasswordHelper::verifyPassword($password, $hash) {
* // password is good
* } else {
* // password is bad
* }
* ~~~
*
* @param string $password The password to be hashed.
* @param integer $cost Cost parameter used by the Blowfish hash algorithm.
* The higher the value of cost,
* the longer it takes to generate the hash and to verify a password against it. Higher cost
* therefore slows down a brute-force attack. For best protection against brute for attacks,
* set it to the highest value that is tolerable on production servers. The time taken to
* compute the hash doubles for every increment by one of $cost. So, for example, if the
* hash takes 1 second to compute when $cost is 14 then then the compute time varies as
* 2^($cost - 14) seconds.
* @throws Exception on bad password parameter or cost parameter
* @return string The password hash string, ASCII and not longer than 64 characters.
* @see validatePassword()
*/
public static function generatePasswordHash($password, $cost = 13)
{
$salt = static::generateSalt($cost);
$hash = crypt($password, $salt);
if (!is_string($hash) || strlen($hash) < 32) {
throw new Exception('Unknown error occurred while generating hash.');
}
return $hash;
}
/**
* Verifies a password against a hash.
* @param string $password The password to verify.
* @param string $hash The hash to verify the password against.
* @return boolean whether the password is correct.
* @throws InvalidParamException on bad password or hash parameters or if crypt() with Blowfish hash is not available.
* @see generatePasswordHash()
*/
public static function validatePassword($password, $hash)
{
if (!is_string($password) || $password === '') {
throw new InvalidParamException('Password must be a string and cannot be empty.');
}
if (!preg_match('/^\$2[axy]\$(\d\d)\$[\./0-9A-Za-z]{22}/', $hash, $matches) || $matches[1] < 4 || $matches[1] > 30) {
throw new InvalidParamException('Hash is invalid.');
}
$test = crypt($password, $hash);
$n = strlen($test);
if (strlen($test) < 32 || $n !== strlen($hash)) {
return false;
}
// Use a for-loop to compare two strings to prevent timing attacks. See:
// http://codereview.stackexchange.com/questions/13512
$check = 0;
for ($i = 0; $i < $n; ++$i) {
$check |= (ord($test[$i]) ^ ord($hash[$i]));
}
return $check === 0;
}
/**
* Generates a salt that can be used to generate a password hash.
*
* The PHP [crypt()](http://php.net/manual/en/function.crypt.php) built-in function
* requires, for the Blowfish hash algorithm, a salt string in a specific format:
* "$2a$", "$2x$" or "$2y$", a two digit cost parameter, "$", and 22 characters
* from the alphabet "./0-9A-Za-z".
*
* @param integer $cost the cost parameter
* @return string the random salt value.
* @throws InvalidParamException if the cost parameter is not between 4 and 30
*/
protected static function generateSalt($cost = 13)
{
$cost = (int)$cost;
if ($cost < 4 || $cost > 30) {
throw new InvalidParamException('Cost must be between 4 and 31.');
}
// Get 20 * 8bits of pseudo-random entropy from mt_rand().
$rand = '';
for ($i = 0; $i < 20; ++$i) {
$rand .= chr(mt_rand(0, 255));
}
// Add the microtime for a little more entropy.
$rand .= microtime();
// Mix the bits cryptographically into a 20-byte binary string.
$rand = sha1($rand, true);
// Form the prefix that specifies Blowfish algorithm and cost parameter.
$salt = sprintf("$2y$%02d$", $cost);
// Append the random salt data in the required base64 format.
$salt .= str_replace('+', '.', substr(base64_encode($rand), 0, 22));
return $salt;
}
}