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Merge pull request #1 from Minishlink/payload
Payload support with Firefox 46+ and Chrome 50+
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,172 @@ | ||
| <?php | ||
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| /* | ||
| * This file is part of the WebPush library. | ||
| * | ||
| * (c) Louis Lagrange <[email protected]> | ||
| * | ||
| * For the full copyright and license information, please view the LICENSE | ||
| * file that was distributed with this source code. | ||
| */ | ||
|
|
||
| namespace Minishlink\WebPush; | ||
|
|
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| use Base64Url\Base64Url; | ||
| use Mdanter\Ecc\EccFactory; | ||
| use Mdanter\Ecc\Serializer\Point\UncompressedPointSerializer; | ||
|
|
||
| final class Encryption | ||
| { | ||
| const MAX_PAYLOAD_LENGTH = 4078; | ||
|
|
||
| /** | ||
| * @param string $payload | ||
| * @param bool $automatic | ||
| * @return string padded payload (plaintext) | ||
| */ | ||
| public static function padPayload($payload, $automatic) | ||
| { | ||
| $payloadLen = strlen($payload); | ||
| $padLen = $automatic ? self::MAX_PAYLOAD_LENGTH - $payloadLen : 0; | ||
| return pack('n*', $padLen).str_pad($payload, $padLen + $payloadLen, chr(0), STR_PAD_LEFT); | ||
| } | ||
|
|
||
| /** | ||
| * @param string $payload With padding | ||
| * @param string $userPublicKey MIME base 64 encoded | ||
| * @param string $userAuthToken MIME base 64 encoded | ||
| * @param bool $nativeEncryption Use OpenSSL (>PHP7.1) | ||
| * | ||
| * @return array | ||
| */ | ||
| public static function encrypt($payload, $userPublicKey, $userAuthToken, $nativeEncryption) | ||
| { | ||
| $userPublicKey = base64_decode($userPublicKey); | ||
| $userAuthToken = base64_decode($userAuthToken); | ||
|
|
||
| // initialize utilities | ||
| $math = EccFactory::getAdapter(); | ||
| $pointSerializer = new UncompressedPointSerializer($math); | ||
| $generator = EccFactory::getNistCurves()->generator256(); | ||
| $curve = EccFactory::getNistCurves()->curve256(); | ||
|
|
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| // get local key pair | ||
| $localPrivateKeyObject = $generator->createPrivateKey(); | ||
| $localPublicKeyObject = $localPrivateKeyObject->getPublicKey(); | ||
| $localPublicKey = hex2bin($pointSerializer->serialize($localPublicKeyObject->getPoint())); | ||
|
|
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| // get user public key object | ||
| $pointUserPublicKey = $pointSerializer->unserialize($curve, bin2hex($userPublicKey)); | ||
| $userPublicKeyObject = $generator->getPublicKeyFrom($pointUserPublicKey->getX(), $pointUserPublicKey->getY(), $generator->getOrder()); | ||
|
|
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| // get shared secret from user public key and local private key | ||
| $sharedSecret = hex2bin($math->decHex($userPublicKeyObject->getPoint()->mul($localPrivateKeyObject->getSecret())->getX())); | ||
|
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| // generate salt | ||
| $salt = openssl_random_pseudo_bytes(16); | ||
|
|
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| // section 4.3 | ||
| $ikm = !empty($userAuthToken) ? | ||
| self::hkdf($userAuthToken, $sharedSecret, 'Content-Encoding: auth'.chr(0), 32) : | ||
| $sharedSecret; | ||
|
|
||
| // section 4.2 | ||
| $context = self::createContext($userPublicKey, $localPublicKey); | ||
|
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| // derive the Content Encryption Key | ||
| $contentEncryptionKeyInfo = self::createInfo('aesgcm', $context); | ||
| $contentEncryptionKey = self::hkdf($salt, $ikm, $contentEncryptionKeyInfo, 16); | ||
|
|
||
| // section 3.3, derive the nonce | ||
| $nonceInfo = self::createInfo('nonce', $context); | ||
| $nonce = self::hkdf($salt, $ikm, $nonceInfo, 12); | ||
|
|
||
| // encrypt | ||
| // "The additional data passed to each invocation of AEAD_AES_128_GCM is a zero-length octet sequence." | ||
| if (!$nativeEncryption) { | ||
| list($encryptedText, $tag) = \AESGCM\AESGCM::encrypt($contentEncryptionKey, $nonce, $payload, ""); | ||
| } else { | ||
| $encryptedText = openssl_encrypt($payload, 'aes-128-gcm', $contentEncryptionKey, OPENSSL_RAW_DATA, $nonce, $tag); // base 64 encoded | ||
| } | ||
|
|
||
| // return values in url safe base64 | ||
| return array( | ||
| 'localPublicKey' => Base64Url::encode($localPublicKey), | ||
| 'salt' => Base64Url::encode($salt), | ||
| 'cipherText' => $encryptedText.$tag, | ||
| ); | ||
| } | ||
|
|
||
| /** | ||
| * HMAC-based Extract-and-Expand Key Derivation Function (HKDF) | ||
| * | ||
| * This is used to derive a secure encryption key from a mostly-secure shared | ||
| * secret. | ||
| * | ||
| * This is a partial implementation of HKDF tailored to our specific purposes. | ||
| * In particular, for us the value of N will always be 1, and thus T always | ||
| * equals HMAC-Hash(PRK, info | 0x01). | ||
| * | ||
| * See {@link https://www.rfc-editor.org/rfc/rfc5869.txt} | ||
| * From {@link https://github.com/GoogleChrome/push-encryption-node/blob/master/src/encrypt.js} | ||
| * | ||
| * @param $salt string A non-secret random value | ||
| * @param $ikm string Input keying material | ||
| * @param $info string Application-specific context | ||
| * @param $length int The length (in bytes) of the required output key | ||
| * @return string | ||
| */ | ||
| private static function hkdf($salt, $ikm, $info, $length) | ||
| { | ||
| // extract | ||
| $prk = hash_hmac('sha256', $ikm, $salt, true); | ||
|
|
||
| // expand | ||
| return substr(hash_hmac('sha256', $info.chr(1), $prk, true), 0, $length); | ||
| } | ||
|
|
||
| /** | ||
| * Creates a context for deriving encyption parameters. | ||
| * See section 4.2 of | ||
| * {@link https://tools.ietf.org/html/draft-ietf-httpbis-encryption-encoding-00} | ||
| * From {@link https://github.com/GoogleChrome/push-encryption-node/blob/master/src/encrypt.js} | ||
| * | ||
| * @param $clientPublicKey string The client's public key | ||
| * @param $serverPublicKey string Our public key | ||
| * @return string | ||
| * @throws \ErrorException | ||
| */ | ||
| private static function createContext($clientPublicKey, $serverPublicKey) | ||
| { | ||
| if (strlen($clientPublicKey) !== 65) { | ||
| throw new \ErrorException('Invalid client public key length'); | ||
| } | ||
|
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| // This one should never happen, because it's our code that generates the key | ||
| if (strlen($serverPublicKey) !== 65) { | ||
| throw new \ErrorException('Invalid server public key length'); | ||
| } | ||
|
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| $len = chr(0).'A'; // 65 as Uint16BE | ||
|
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| return chr(0).$len.$clientPublicKey.$len.$serverPublicKey; | ||
| } | ||
|
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| /** | ||
| * Returns an info record. See sections 3.2 and 3.3 of | ||
| * {@link https://tools.ietf.org/html/draft-ietf-httpbis-encryption-encoding-00} | ||
| * From {@link https://github.com/GoogleChrome/push-encryption-node/blob/master/src/encrypt.js} | ||
| * | ||
| * @param $type string The type of the info record | ||
| * @param $context string The context for the record | ||
| * @return string | ||
| * @throws \ErrorException | ||
| */ | ||
| private static function createInfo($type, $context) { | ||
| if (strlen($context) !== 135) { | ||
| throw new \ErrorException('Context argument has invalid size'); | ||
| } | ||
|
|
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| return 'Content-Encoding: '.$type.chr(0).'P-256'.$context; | ||
| } | ||
| } |
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