Created
May 16, 2016 21:30
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Implementation of Mozilla's node-client-sessions in PHP
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| <?php | |
| if(!function_exists('hash_equals')) { | |
| function hash_equals($str1, $str2) { | |
| if(strlen($str1) != strlen($str2)) { | |
| return false; | |
| } else { | |
| $res = $str1 ^ $str2; | |
| $ret = 0; | |
| for($i = strlen($res) - 1; $i >= 0; $i--) $ret |= ord($res[$i]); | |
| return !$ret; | |
| } | |
| } | |
| } | |
| class ClientSessions | |
| { | |
| private $opts; | |
| private $COOKIE_NAME_SEP = '='; | |
| private $DEFAULT_SIGNATURE_ALGORITHM = 'sha256'; | |
| private $DEFAULT_ENCRYPTION_ALGORITHM = 'RIJNDAEL-128'; | |
| private $KDF_ENC = 'cookiesession-encryption'; | |
| private $KDF_MAC = 'cookiesession-signature'; | |
| function __construct ($opts) { | |
| $this->opts = $opts; | |
| } | |
| private function aes256_cbc_encrypt($key, $data, $iv) { | |
| if(32 !== strlen($key)) $key = hash('SHA256', $key, true); | |
| if(16 !== strlen($iv)) $iv = hash('MD5', $iv, true); | |
| $padding = 16 - (strlen($data) % 16); | |
| $data .= str_repeat(chr($padding), $padding); | |
| return mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $data, MCRYPT_MODE_CBC, $iv); | |
| } | |
| function aes256_cbc_decrypt($key, $data, $iv) { | |
| if(32 !== strlen($key)) $key = hash('SHA256', $key, true); | |
| if(16 !== strlen($iv)) $iv = hash('MD5', $iv, true); | |
| $data = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $data, MCRYPT_MODE_CBC, $iv); | |
| $padding = ord($data[strlen($data) - 1]); | |
| return substr($data, 0, -$padding); | |
| } | |
| function base64urlencode($arg) { | |
| $s = base64_encode($arg); | |
| $exploded = explode('=', $s); | |
| $s = $exploded[0]; | |
| $s = preg_replace('/\+/', '-', $s); | |
| $s = preg_replace('/\//', '_', $s); | |
| return $s; | |
| } | |
| function base64urldecode($arg) { | |
| $s = preg_replace('/-/', '+', $arg); | |
| $s = preg_replace('/_/', '/', $s); | |
| switch (strlen($s) % 4) { // Pad with trailing '='s | |
| case 0: | |
| break; // No pad chars in this case | |
| case 2: | |
| $s = $s . "=="; | |
| break; // Two pad chars | |
| case 3: | |
| $s = $s . "="; | |
| break; // One pad char | |
| default: | |
| throw new Exception("Illegal base64url string!"); | |
| } | |
| return base64_decode($s); | |
| } | |
| private function computeHmac($opts, $iv, $ciphertext, $duration, $createdAt) { | |
| $ctx = hash_init($opts->signatureAlgorithm, 1, $opts->signatureKey); | |
| hash_update($ctx, $iv); | |
| hash_update($ctx, "."); | |
| hash_update($ctx, $ciphertext); | |
| hash_update($ctx, "."); | |
| hash_update($ctx, (string) $createdAt); | |
| hash_update($ctx, "."); | |
| hash_update($ctx, (string) $duration); | |
| return hash_final($ctx, true); | |
| } | |
| private function constantTimeEquals($a, $b) { | |
| return hash_equals($a, $b); | |
| } | |
| private function deriveKey($master, $type) { | |
| return hash_hmac('sha256', $type, $master, true); | |
| } | |
| private function setupKeys($opts) { | |
| $opts->encryptionKey = $this->deriveKey($opts->secret, $this->KDF_ENC); | |
| $opts->signatureKey = $this->deriveKey($opts->secret, $this->KDF_MAC); | |
| $opts->signatureAlgorithm = $this->DEFAULT_SIGNATURE_ALGORITHM; | |
| $opts->encryptionAlgorithm = $this->DEFAULT_ENCRYPTION_ALGORITHM; | |
| } | |
| public function decode($session) | |
| { | |
| // Grabbing all the parts | |
| $components = explode('.', $session); | |
| // Setting up the authentication/signature encryption-methods/keys | |
| $this->setupKeys($this->opts); | |
| // Naming the stuff we need right and decoding some things | |
| $iv = $this->base64urldecode($components[0]); | |
| $ciphertext = $this->base64urldecode($components[1]); | |
| $hmac = $components[4]; | |
| $createdAt = floatval($components[2]); | |
| $duration = floatval($components[3]); | |
| // If the IV isn't 16 characters, nothing else will work | |
| if (strlen($iv) != 16) { | |
| return null; | |
| } | |
| // Verify the HMAC | |
| $expectedHmac = $this->computeHmac($this->opts, $iv, $ciphertext, $duration, $createdAt); | |
| $encodedExpectedHmac = $this->base64urlencode($expectedHmac); | |
| if (!$this->constantTimeEquals($hmac, $encodedExpectedHmac)) { | |
| return null; | |
| } | |
| $plainBinary = $this->aes256_cbc_decrypt($this->opts->encryptionKey, $ciphertext, $iv); | |
| $plainText = utf8_encode($plainBinary); | |
| // Returning the results | |
| $result = new stdClass(); | |
| $sessionJson = substr($plainText, strrpos($plainText, $this->COOKIE_NAME_SEP) + 1); | |
| $result->session = json_decode($sessionJson); | |
| $result->createdAt = $createdAt; | |
| $result->duration = $duration; | |
| return $result; | |
| } | |
| public function encode($session) { | |
| // Setting up the authentication/signature encryption-methods/keys | |
| $this->setupKeys($this->opts); | |
| $duration = round(24*60*60*1000); | |
| $createdAt = round(microtime(true)*1000); | |
| $iv = mcrypt_create_iv(16, MCRYPT_RAND); | |
| $json = json_encode($session); | |
| $plainText = $this->opts->cookieName . $this->COOKIE_NAME_SEP . $json; | |
| $ciphertext = $this->aes256_cbc_encrypt($this->opts->encryptionKey, $plainText, $iv); | |
| $hmac = $this->computeHmac($this->opts, $iv, $ciphertext, $duration, $createdAt); | |
| $components = array( | |
| $this->base64urlencode($iv), | |
| $this->base64urlencode($ciphertext), | |
| (string)$createdAt, | |
| (string)$duration, | |
| $this->base64urlencode($hmac) | |
| ); | |
| $result = implode('.', $components); | |
| return $result; | |
| } | |
| public function destroy() { | |
| setcookie($this->opts->cookieName, '', 0, '/', $this->opts->cookieDomain); | |
| } | |
| public function get() { | |
| if (!isset($_COOKIE[$this->opts->cookieName]) || !array_key_exists($this->opts->cookieName, $_COOKIE)) { | |
| return null; | |
| } | |
| $result = $this->decode($_COOKIE[$this->opts->cookieName]); | |
| if ($result == null) { | |
| return null; | |
| } | |
| // Checking whether the cookie is expired | |
| $expires = $result->createdAt + $result->duration; | |
| $now = microtime(true) * 1000; | |
| if ($expires <= $now) { | |
| return null; | |
| } | |
| // Returning the results | |
| return $result->session; | |
| } | |
| public function set ($session) { | |
| $cookieValue = $this->encode($session); | |
| setcookie($this->opts->cookieName, $cookieValue, 0, '/', $this->opts->cookieDomain); | |
| } | |
| } | |
| ?> |
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