Note: this class requires 'OpenSSL' PHP extension for random key/string generation on Windows and * for encryption/decryption on all platforms. For the highest security level PHP version >= 5.5.0 is recommended. * * @author Qiang Xue * @author Tom Worster * @author Klimov Paul * @since 2.0 */ class Security extends Component { /** * @var string The cipher to use for encryption and decryption. */ public $cipher = 'AES-128-CBC'; /** * @var array[] Look-up table of block sizes and key sizes for each supported OpenSSL cipher. * * In each element, the key is one of the ciphers supported by OpenSSL (@see openssl_get_cipher_methods()). * The value is an array of two integers, the first is the cipher's block size in bytes and the second is * the key size in bytes. * * > Warning: All OpenSSL ciphers that we recommend are in the default value, i.e. AES in CBC mode. * * > Note: Yii's encryption protocol uses the same size for cipher key, HMAC signature key and key * derivation salt. */ public $allowedCiphers = [ 'AES-128-CBC' => [16, 16], 'AES-192-CBC' => [16, 24], 'AES-256-CBC' => [16, 32], ]; /** * @var string Hash algorithm for key derivation. Recommend sha256, sha384 or sha512. * @see hash_algos() */ public $kdfHash = 'sha256'; /** * @var string Hash algorithm for message authentication. Recommend sha256, sha384 or sha512. * @see hash_algos() */ public $macHash = 'sha256'; /** * @var string HKDF info value for derivation of message authentication key. * @see hkdf() */ public $authKeyInfo = 'AuthorizationKey'; /** * @var integer derivation iterations count. * Set as high as possible to hinder dictionary password attacks. */ public $derivationIterations = 100000; /** * @var string strategy, which should be used to generate password hash. * Available strategies: * - 'password_hash' - use of PHP `password_hash()` function with PASSWORD_DEFAULT algorithm. * This option is recommended, but it requires PHP version >= 5.5.0 * - 'crypt' - use PHP `crypt()` function. */ public $passwordHashStrategy = 'crypt'; /** * Encrypts data using a password. * Derives keys for encryption and authentication from the password using PBKDF2 and a random salt, * which is deliberately slow to protect against dictionary attacks. Use [[encryptByKey()]] to * encrypt fast using a cryptographic key rather than a password. Key derivation time is * determined by [[$derivationIterations]], which should be set as high as possible. * The encrypted data includes a keyed message authentication code (MAC) so there is no need * to hash input or output data. * > Note: Avoid encrypting with passwords wherever possible. Nothing can protect against * poor-quality or compromised passwords. * @param string $data the data to encrypt * @param string $password the password to use for encryption * @return string the encrypted data * @see decryptByPassword() * @see encryptByKey() */ public function encryptByPassword($data, $password) { return $this->encrypt($data, true, $password, null); } /** * Encrypts data using a cryptograhic key. * Derives keys for encryption and authentication from the input key using HKDF and a random salt, * which is very fast relative to [[encryptByPassword()]]. The input key must be properly * random -- use [[generateRandomKey()]] to generate keys. * The encrypted data includes a keyed message authentication code (MAC) so there is no need * to hash input or output data. * @param string $data the data to encrypt * @param string $inputKey the input to use for encryption and authentication * @param string $info optional context and application specific information, see [[hkdf()]] * @return string the encrypted data * @see decryptByPassword() * @see encryptByKey() */ public function encryptByKey($data, $inputKey, $info = null) { return $this->encrypt($data, false, $inputKey, $info); } /** * Verifies and decrypts data encrypted with [[encryptByPassword()]]. * @param string $data the encrypted data to decrypt * @param string $password the password to use for decryption * @return bool|string the decrypted data or false on authentication failure * @see encryptByPassword() */ public function decryptByPassword($data, $password) { return $this->decrypt($data, true, $password, null); } /** * Verifies and decrypts data encrypted with [[encryptByPassword()]]. * @param string $data the encrypted data to decrypt * @param string $inputKey the input to use for encryption and authentication * @param string $info optional context and application specific information, see [[hkdf()]] * @return bool|string the decrypted data or false on authentication failure * @see encryptByKey() */ public function decryptByKey($data, $inputKey, $info = null) { return $this->decrypt($data, false, $inputKey, $info); } /** * Encrypts data. * * @param string $data data to be encrypted * @param boolean $passwordBased set true to use password-based key derivation * @param string $secret the encryption password or key * @param string $info context/application specific information, e.g. a user ID * See [RFC 5869 Section 3.2](https://tools.ietf.org/html/rfc5869#section-3.2) for more details. * * @return string the encrypted data * @throws InvalidConfigException on OpenSSL not loaded * @throws Exception on OpenSSL error * @see decrypt() */ protected function encrypt($data, $passwordBased, $secret, $info) { if (!extension_loaded('openssl')) { throw new InvalidConfigException('Encryption requires the OpenSSL PHP extension'); } if (!isset($this->allowedCiphers[$this->cipher][0], $this->allowedCiphers[$this->cipher][1])) { throw new InvalidConfigException($this->cipher . ' is not an allowed cipher'); } list($blockSize, $keySize) = $this->allowedCiphers[$this->cipher]; $keySalt = $this->generateRandomKey($keySize); if ($passwordBased) { $key = $this->pbkdf2($this->kdfHash, $secret, $keySalt, $this->derivationIterations, $keySize); } else { $key = $this->hkdf($this->kdfHash, $secret, $keySalt, $info, $keySize); } $iv = $this->generateRandomKey($blockSize); $encrypted = openssl_encrypt($data, $this->cipher, $key, OPENSSL_RAW_DATA, $iv); if ($encrypted === false) { throw new \yii\base\Exception('OpenSSL failure on encryption: ' . openssl_error_string()); } $authKey = $this->hkdf($this->kdfHash, $key, null, $this->authKeyInfo, $keySize); $hashed = $this->hashData($iv . $encrypted, $authKey); /* * Output: [keySalt][MAC][IV][ciphertext] * - keySalt is KEY_SIZE bytes long * - MAC: message authentication code, length same as the output of MAC_HASH * - IV: initialization vector, length $blockSize */ return $keySalt . $hashed; } /** * Decrypts data. * * @param string $data encrypted data to be decrypted. * @param boolean $passwordBased set true to use password-based key derivation * @param string $secret the decryption password or key * @param string $info context/application specific information, @see encrypt() * * @return bool|string the decrypted data or false on authentication failure * @throws InvalidConfigException on OpenSSL not loaded * @throws Exception on OpenSSL error * @see encrypt() */ protected function decrypt($data, $passwordBased, $secret, $info) { if (!extension_loaded('openssl')) { throw new InvalidConfigException('Encryption requires the OpenSSL PHP extension'); } if (!isset($this->allowedCiphers[$this->cipher][0], $this->allowedCiphers[$this->cipher][1])) { throw new InvalidConfigException($this->cipher . ' is not an allowed cipher'); } list($blockSize, $keySize) = $this->allowedCiphers[$this->cipher]; $keySalt = StringHelper::byteSubstr($data, 0, $keySize); if ($passwordBased) { $key = $this->pbkdf2($this->kdfHash, $secret, $keySalt, $this->derivationIterations, $keySize); } else { $key = $this->hkdf($this->kdfHash, $secret, $keySalt, $info, $keySize); } $authKey = $this->hkdf($this->kdfHash, $key, null, $this->authKeyInfo, $keySize); $data = $this->validateData(StringHelper::byteSubstr($data, $keySize, null), $authKey); if ($data === false) { return false; } $iv = StringHelper::byteSubstr($data, 0, $blockSize); $encrypted = StringHelper::byteSubstr($data, $blockSize, null); $decrypted = openssl_decrypt($encrypted, $this->cipher, $key, OPENSSL_RAW_DATA, $iv); if ($decrypted === false) { throw new \yii\base\Exception('OpenSSL failure on decryption: ' . openssl_error_string()); } return $decrypted; } /** * Derives a key from the given input key using the standard HKDF algorithm. * Implements HKDF specified in [RFC 5869](https://tools.ietf.org/html/rfc5869). * Recommend use one of the SHA-2 hash algorithms: sha224, sha256, sha384 or sha512. * @param string $algo a hash algorithm supported by `hash_hmac()`, e.g. 'SHA-256' * @param string $inputKey the source key * @param string $salt the random salt * @param string $info optional info to bind the derived key material to application- * and context-specific information, e.g. a user ID or API version, see * [RFC 5869](https://tools.ietf.org/html/rfc5869) * @param integer $length length of the output key in bytes. If 0, the output key is * the length of the hash algorithm output. * @throws InvalidParamException when HMAC generation fails. * @return string the derived key */ public function hkdf($algo, $inputKey, $salt = null, $info = null, $length = 0) { $test = @hash_hmac($algo, '', '', true); if (!$test) { throw new InvalidParamException('Failed to generate HMAC with hash algorithm: ' . $algo); } $hashLength = StringHelper::byteLength($test); if (is_string($length) && preg_match('{^\d{1,16}$}', $length)) { $length = (int) $length; } if (!is_integer($length) || $length < 0 || $length > 255 * $hashLength) { throw new InvalidParamException('Invalid length'); } $blocks = $length !== 0 ? ceil($length / $hashLength) : 1; if ($salt === null) { $salt = str_repeat("\0", $hashLength); } $prKey = hash_hmac($algo, $inputKey, $salt, true); $hmac = ''; $outputKey = ''; for ($i = 1; $i <= $blocks; $i++) { $hmac = hash_hmac($algo, $hmac . $info . chr($i), $prKey, true); $outputKey .= $hmac; } if ($length !== 0) { $outputKey = StringHelper::byteSubstr($outputKey, 0, $length); } return $outputKey; } /** * Derives a key from the given password using the standard PBKDF2 algorithm. * Implements HKDF2 specified in [RFC 2898](http://tools.ietf.org/html/rfc2898#section-5.2) * Recommend use one of the SHA-2 hash algorithms: sha224, sha256, sha384 or sha512. * @param string $algo a hash algorithm supported by `hash_hmac()`, e.g. 'SHA-256' * @param string $password the source password * @param string $salt the random salt * @param integer $iterations the number of iterations of the hash algorithm. Set as high as * possible to hinder dictionary password attacks. * @param integer $length length of the output key in bytes. If 0, the output key is * the length of the hash algorithm output. * @return string the derived key * @throws InvalidParamException when hash generation fails due to invalid params given. */ public function pbkdf2($algo, $password, $salt, $iterations, $length = 0) { if (function_exists('hash_pbkdf2')) { $outputKey = hash_pbkdf2($algo, $password, $salt, $iterations, $length, true); if ($outputKey === false) { throw new InvalidParamException('Invalid parameters to hash_pbkdf2()'); } return $outputKey; } // todo: is there a nice way to reduce the code repetition in hkdf() and pbkdf2()? $test = @hash_hmac($algo, '', '', true); if (!$test) { throw new InvalidParamException('Failed to generate HMAC with hash algorithm: ' . $algo); } if (is_string($iterations) && preg_match('{^\d{1,16}$}', $iterations)) { $iterations = (int) $iterations; } if (!is_integer($iterations) || $iterations < 1) { throw new InvalidParamException('Invalid iterations'); } if (is_string($length) && preg_match('{^\d{1,16}$}', $length)) { $length = (int) $length; } if (!is_integer($length) || $length < 0) { throw new InvalidParamException('Invalid length'); } $hashLength = StringHelper::byteLength($test); $blocks = $length !== 0 ? ceil($length / $hashLength) : 1; $outputKey = ''; for ($j = 1; $j <= $blocks; $j++) { $hmac = hash_hmac($algo, $salt . pack('N', $j), $password, true); $xorsum = $hmac; for ($i = 1; $i < $iterations; $i++) { $hmac = hash_hmac($algo, $hmac, $password, true); $xorsum ^= $hmac; } $outputKey .= $xorsum; } if ($length !== 0) { $outputKey = StringHelper::byteSubstr($outputKey, 0, $length); } return $outputKey; } /** * Prefixes data with a keyed hash value so that it can later be detected if it is tampered. * There is no need to hash inputs or outputs of [[encryptByKey()]] or [[encryptByPassword()]] * as those methods perform the task. * @param string $data the data to be protected * @param string $key the secret key to be used for generating hash. Should be a secure * cryptographic key. * @param boolean $rawHash whether the generated hash value is in raw binary format. If false, lowercase * hex digits will be generated. * @return string the data prefixed with the keyed hash * @throws InvalidConfigException when HMAC generation fails. * @see validateData() * @see generateRandomKey() * @see hkdf() * @see pbkdf2() */ public function hashData($data, $key, $rawHash = false) { $hash = hash_hmac($this->macHash, $data, $key, $rawHash); if (!$hash) { throw new InvalidConfigException('Failed to generate HMAC with hash algorithm: ' . $this->macHash); } return $hash . $data; } /** * 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()]]. * 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. * @param boolean $rawHash this should take the same value as when you generate the data using [[hashData()]]. * It indicates whether the hash value in the data is in binary format. If false, it means the hash value consists * of lowercase hex digits only. * hex digits will be generated. * @return string the real data with the hash stripped off. False if the data is tampered. * @throws InvalidConfigException when HMAC generation fails. * @see hashData() */ public function validateData($data, $key, $rawHash = false) { $test = @hash_hmac($this->macHash, '', '', $rawHash); if (!$test) { throw new InvalidConfigException('Failed to generate HMAC with hash algorithm: ' . $this->macHash); } $hashLength = StringHelper::byteLength($test); if (StringHelper::byteLength($data) >= $hashLength) { $hash = StringHelper::byteSubstr($data, 0, $hashLength); $pureData = StringHelper::byteSubstr($data, $hashLength, null); $calculatedHash = hash_hmac($this->macHash, $pureData, $key, $rawHash); if ($this->compareString($hash, $calculatedHash)) { return $pureData; } } return false; } /** * Generates specified number of random bytes. * Note that output may not be ASCII. * @see generateRandomString() if you need a string. * * @param integer $length the number of bytes to generate * @return string the generated random bytes * @throws InvalidConfigException if OpenSSL extension is required (e.g. on Windows) but not installed. * @throws Exception on failure. */ public function generateRandomKey($length = 32) { /* * Strategy * * The most common platform is Linux, on which /dev/urandom is the best choice. Many other OSs * implement a device called /dev/urandom for Linux compat and it is good too. So if there is * a /dev/urandom then it is our first choice regardless of OS. * * Nearly all other modern Unix-like systems (the BSDs, Unixes and OS X) have a /dev/random * that is a good choice. If we didn't get bytes from /dev/urandom then we try this next but * only if the system is not Linux. Do not try to read /dev/random on Linux. * * Finally, OpenSSL can supply CSPR bytes. It is our last resort. On Windows this reads from * CryptGenRandom, which is the right thing to do. On other systems that don't have a Unix-like * /dev/urandom, it will deliver bytes from its own CSPRNG that is seeded from kernel sources * of randomness. Even though it is fast, we don't generally prefer OpenSSL over /dev/urandom * because an RNG in user space memory is undesirable. * * For background, see http://sockpuppet.org/blog/2014/02/25/safely-generate-random-numbers/ */ $bytes = ''; // If we are on Linux or any OS that mimics the Linux /dev/urandom device, e.g. FreeBSD or OS X, // then read from /dev/urandom. if (@file_exists('/dev/urandom')) { $handle = fopen('/dev/urandom', 'r'); if ($handle !== false) { $bytes .= fread($handle, $length); fclose($handle); } } if (StringHelper::byteLength($bytes) >= $length) { return StringHelper::byteSubstr($bytes, 0, $length); } // If we are not on Linux and there is a /dev/random device then we have a BSD or Unix device // that won't block. It's not safe to read from /dev/random on Linux. if (PHP_OS !== 'Linux' && @file_exists('/dev/random')) { $handle = fopen('/dev/random', 'r'); if ($handle !== false) { $bytes .= fread($handle, $length); fclose($handle); } } if (StringHelper::byteLength($bytes) >= $length) { return StringHelper::byteSubstr($bytes, 0, $length); } if (!extension_loaded('openssl')) { throw new InvalidConfigException('The OpenSSL PHP extension is not installed.'); } $bytes .= openssl_random_pseudo_bytes($length, $cryptoStrong); if (StringHelper::byteLength($bytes) < $length || !$cryptoStrong) { throw new Exception('Unable to generate random bytes.'); } return StringHelper::byteSubstr($bytes, 0, $length); } /** * Generates a random string of specified length. * The string generated matches [A-Za-z0-9_-]+ and is transparent to URL-encoding. * * @param integer $length the length of the key in characters * @return string the generated random key * @throws InvalidConfigException if OpenSSL extension is needed but not installed. * @throws Exception on failure. */ public function generateRandomString($length = 32) { $bytes = $this->generateRandomKey($length); // '=' character(s) returned by base64_encode() are always discarded because // they are guaranteed to be after position $length in the base64_encode() output. return strtr(substr(base64_encode($bytes), 0, $length), '+/', '_-'); } /** * Generates a secure hash from a password and a random salt. * * The generated hash can be stored in database. * 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) * $hash = Yii::$app->getSecurity()->generatePasswordHash($password); * // ...save $hash in database... * * // during login, validate if the password entered is correct using $hash fetched from database * if (Yii::$app->getSecurity()->validatePassword($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 $cost. * @return string The password hash string. When [[passwordHashStrategy]] is set to 'crypt', * the output is always 60 ASCII characters, when set to 'password_hash' the output length * might increase in future versions of PHP (http://php.net/manual/en/function.password-hash.php) * @throws Exception on bad password parameter or cost parameter. * @throws InvalidConfigException when an unsupported password hash strategy is configured. * @see validatePassword() */ public function generatePasswordHash($password, $cost = 13) { switch ($this->passwordHashStrategy) { case 'password_hash': if (!function_exists('password_hash')) { throw new InvalidConfigException('Password hash key strategy "password_hash" requires PHP >= 5.5.0, either upgrade your environment or use another strategy.'); } /** @noinspection PhpUndefinedConstantInspection */ return password_hash($password, PASSWORD_DEFAULT, ['cost' => $cost]); case 'crypt': $salt = $this->generateSalt($cost); $hash = crypt($password, $salt); // strlen() is safe since crypt() returns only ascii if (!is_string($hash) || strlen($hash) !== 60) { throw new Exception('Unknown error occurred while generating hash.'); } return $hash; default: throw new InvalidConfigException("Unknown password hash strategy '{$this->passwordHashStrategy}'"); } } /** * Verifies a password against a hash. * @param string $password The password to verify. * @param string $hash The hash to verify the password against. * @return boolean whether the password is correct. * @throws InvalidParamException on bad password/hash parameters or if crypt() with Blowfish hash is not available. * @throws InvalidConfigException when an unsupported password hash strategy is configured. * @see generatePasswordHash() */ public function validatePassword($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 || $matches[1] > 30) { throw new InvalidParamException('Hash is invalid.'); } switch ($this->passwordHashStrategy) { case 'password_hash': if (!function_exists('password_verify')) { throw new InvalidConfigException('Password hash key strategy "password_hash" requires PHP >= 5.5.0, either upgrade your environment or use another strategy.'); } return password_verify($password, $hash); case 'crypt': $test = crypt($password, $hash); $n = strlen($test); if ($n !== 60) { return false; } return $this->compareString($test, $hash); default: throw new InvalidConfigException("Unknown password hash strategy '{$this->passwordHashStrategy}'"); } } /** * 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 $cost the cost parameter * @return string the random salt value. * @throws InvalidParamException if the cost parameter is out of the range of 4 to 31. */ protected function generateSalt($cost = 13) { $cost = (int) $cost; if ($cost < 4 || $cost > 31) { throw new InvalidParamException('Cost must be between 4 and 31.'); } // Get a 20-byte random string $rand = $this->generateRandomKey(20); // Form the prefix that specifies Blowfish (bcrypt) 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; } /** * Performs string comparison using timing attack resistant approach. * @see http://codereview.stackexchange.com/questions/13512 * @param string $expected string to compare. * @param string $actual user-supplied string. * @return boolean whether strings are equal. */ public function compareString($expected, $actual) { $expected .= "\0"; $actual .= "\0"; $expectedLength = StringHelper::byteLength($expected); $actualLength = StringHelper::byteLength($actual); $diff = $expectedLength - $actualLength; for ($i = 0; $i < $actualLength; $i++) { $diff |= (ord($actual[$i]) ^ ord($expected[$i % $expectedLength])); } return $diff === 0; } }