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Diffstat (limited to 'managing-ui/lib/Encryption.class.php')
| -rw-r--r-- | managing-ui/lib/Encryption.class.php | 162 |
1 files changed, 162 insertions, 0 deletions
diff --git a/managing-ui/lib/Encryption.class.php b/managing-ui/lib/Encryption.class.php new file mode 100644 index 0000000..2920d36 --- /dev/null +++ b/managing-ui/lib/Encryption.class.php @@ -0,0 +1,162 @@ +<?php +/** + * A class to handle secure encryption and decryption of arbitrary data + * + * Note that this is not just straight encryption. It also has a few other + * features in it to make the encrypted data far more secure. Note that any + * other implementations used to decrypt data will have to do the same exact + * operations. + * + * Security Benefits: + * + * - Uses Key stretching + * - Hides the Initialization Vector + * - Does HMAC verification of source data + * + */ +class Encryption { + + /** + * @var string $cipher The mcrypt cipher to use for this instance + */ + protected $cipher = ''; + + /** + * @var int $mode The mcrypt cipher mode to use + */ + protected $mode = ''; + + /** + * @var int $rounds The number of rounds to feed into PBKDF2 for key generation + */ + protected $rounds = 100; + + /** + * Constructor! + * + * @param string $cipher The MCRYPT_* cypher to use for this instance + * @param int $mode The MCRYPT_MODE_* mode to use for this instance + * @param int $rounds The number of PBKDF2 rounds to do on the key + */ + public function __construct($cipher, $mode, $rounds = 100) { + $this->cipher = $cipher; + $this->mode = $mode; + $this->rounds = (int) $rounds; + } + + /** + * Decrypt the data with the provided key + * + * @param string $data The encrypted datat to decrypt + * @param string $key The key to use for decryption + * + * @returns string|false The returned string if decryption is successful + * false if it is not + */ + public function decrypt($data, $key) { + $salt = substr($data, 0, 128); + $enc = substr($data, 128, -64); + $mac = substr($data, -64); + + list ($cipherKey, $macKey, $iv) = $this->getKeys($salt, $key); + + if ($mac !== hash_hmac('sha512', $enc, $macKey, true)) { + return false; + } + + $dec = mcrypt_decrypt($this->cipher, $cipherKey, $enc, $this->mode, $iv); + + $data = $this->unpad($dec); + + return $data; + } + + /** + * Encrypt the supplied data using the supplied key + * + * @param string $data The data to encrypt + * @param string $key The key to encrypt with + * + * @returns string The encrypted data + */ + public function encrypt($data, $key) { + $salt = mcrypt_create_iv(128, MCRYPT_DEV_URANDOM); + list ($cipherKey, $macKey, $iv) = $this->getKeys($salt, $key); + + $data = $this->pad($data); + + $enc = mcrypt_encrypt($this->cipher, $cipherKey, $data, $this->mode, $iv); + + $mac = hash_hmac('sha512', $enc, $macKey, true); + return $salt . $enc . $mac; + } + + /** + * Generates a set of keys given a random salt and a master key + * + * @param string $salt A random string to change the keys each encryption + * @param string $key The supplied key to encrypt with + * + * @returns array An array of keys (a cipher key, a mac key, and a IV) + */ + protected function getKeys($salt, $key) { + $ivSize = mcrypt_get_iv_size($this->cipher, $this->mode); + $keySize = mcrypt_get_key_size($this->cipher, $this->mode); + $length = 2 * $keySize + $ivSize; + + $key = $this->pbkdf2('sha512', $key, $salt, $this->rounds, $length); + + $cipherKey = substr($key, 0, $keySize); + $macKey = substr($key, $keySize, $keySize); + $iv = substr($key, 2 * $keySize); + return array($cipherKey, $macKey, $iv); + } + + /** + * Stretch the key using the PBKDF2 algorithm + * + * @see http://en.wikipedia.org/wiki/PBKDF2 + * + * @param string $algo The algorithm to use + * @param string $key The key to stretch + * @param string $salt A random salt + * @param int $rounds The number of rounds to derive + * @param int $length The length of the output key + * + * @returns string The derived key. + */ + protected function pbkdf2($algo, $key, $salt, $rounds, $length) { + $size = strlen(hash($algo, '', true)); + $len = ceil($length / $size); + $result = ''; + for ($i = 1; $i <= $len; $i++) { + $tmp = hash_hmac($algo, $salt . pack('N', $i), $key, true); + $res = $tmp; + for ($j = 1; $j < $rounds; $j++) { + $tmp = hash_hmac($algo, $tmp, $key, true); + $res ^= $tmp; + } + $result .= $res; + } + return substr($result, 0, $length); + } + + protected function pad($data) { + $length = mcrypt_get_block_size($this->cipher, $this->mode); + $padAmount = $length - strlen($data) % $length; + if ($padAmount == 0) { + $padAmount = $length; + } + return $data . str_repeat(chr($padAmount), $padAmount); + } + + protected function unpad($data) { + $length = mcrypt_get_block_size($this->cipher, $this->mode); + $last = ord($data[strlen($data) - 1]); + if ($last > $length) return false; + if (substr($data, -1 * $last) !== str_repeat(chr($last), $last)) { + return false; + } + return substr($data, 0, -1 * $last); + } +}
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