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MinishlinkMinishlink
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‎src/Encryption.php

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<?php
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/*
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* This file is part of the WebPush library.
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*
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* (c) Louis Lagrange <[email protected]>
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*
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* For the full copyright and license information, please view the LICENSE
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* file that was distributed with this source code.
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*/
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namespace Minishlink\WebPush;
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use Base64Url\Base64Url;
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use Mdanter\Ecc\Crypto\Key\PublicKey;
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use Mdanter\Ecc\EccFactory;
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use Mdanter\Ecc\Serializer\Point\UncompressedPointSerializer;
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final class Encryption
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{
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/**
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* @param string $payload
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* @param string $userPublicKey MIME base 64 encoded
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* @param string $userAuthToken MIME base 64 encoded
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* @param bool $nativeEncryption Use OpenSSL (>PHP7.1)
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*
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* @return array
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*/
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public static function encrypt($payload, $userPublicKey, $userAuthToken, $nativeEncryption)
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{
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$userPublicKey = base64_decode($userPublicKey);
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$userAuthToken = base64_decode($userAuthToken);
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$plaintext = chr(0).chr(0).utf8_decode($payload);
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// initialize utilities
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$math = EccFactory::getAdapter();
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$keySerializer = new UncompressedPointSerializer($math);
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$curveGenerator = EccFactory::getNistCurves()->generator256();
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$curve = EccFactory::getNistCurves()->curve256();
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// get local key pair
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$localPrivateKeyObject = $curveGenerator->createPrivateKey();
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$localPublicKeyObject = $localPrivateKeyObject->getPublicKey();
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$localPublicKey = hex2bin($keySerializer->serialize($localPublicKeyObject->getPoint()));
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// get user public key object
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$userPublicKeyObject = new PublicKey($math, $curveGenerator, $keySerializer->unserialize($curve, bin2hex($userPublicKey)));
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// get shared secret from user public key and local private key
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$sharedSecret = hex2bin($math->decHex($userPublicKeyObject->getPoint()->mul($localPrivateKeyObject->getSecret())->getX()));
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// generate salt
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$salt = openssl_random_pseudo_bytes(16);
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$prk = !empty($userAuthToken) ?
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self::hkdf($userAuthToken, $sharedSecret, utf8_decode('Content-Encoding: auth\0'), 32) :
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$sharedSecret;
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$context = self::createContext($userPublicKey, $localPublicKey);
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// derive the Content Encryption Key
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$contentEncryptionKeyInfo = self::createInfo('aesgcm', $context);
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$contentEncryptionKey = self::hkdf($salt, $prk, $contentEncryptionKeyInfo, 16);
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// derive the Nonce
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$nonceInfo = self::createInfo('nonce', $context);
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$nonce = self::hkdf($salt, $prk, $nonceInfo, 12);
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// encrypt
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if (!$nativeEncryption) {
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list($encryptedText, $tag) = \Jose\Util\GCM::encrypt($contentEncryptionKey, $nonce, $plaintext, "");
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$cipherText = $encryptedText.$tag;
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} else {
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$cipherText = openssl_encrypt($plaintext, 'aes-128-gcm', $contentEncryptionKey, false, $nonce); // base 64 encoded
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}
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// return values in url safe base64
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return array(
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'localPublicKey' => Base64Url::encode($localPublicKey),
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'salt' => Base64Url::encode($salt),
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'cipherText' => $cipherText,
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);
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}
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/**
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* HMAC-based Extract-and-Expand Key Derivation Function (HKDF)
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*
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* This is used to derive a secure encryption key from a mostly-secure shared
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* secret.
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*
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* This is a partial implementation of HKDF tailored to our specific purposes.
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* In particular, for us the value of N will always be 1, and thus T always
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* equals HMAC-Hash(PRK, info | 0x01).
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*
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* See {@link https://www.rfc-editor.org/rfc/rfc5869.txt}
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* From {@link https://github.com/GoogleChrome/push-encryption-node/blob/master/src/encrypt.js}
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*
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* @param $salt string A non-secret random value
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* @param $ikm string Input keying material
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* @param $info string Application-specfic context
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* @param $length int The length (in bytes) of the required output key
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* @return string
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*/
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private static function hkdf($salt, $ikm, $info, $length)
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{
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// extract
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$prk = hash_hmac('sha256', $ikm, $salt, true);
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// expand
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return substr(hash_hmac('sha256', $info.chr(1), $prk, true), 0, $length);
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}
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/**
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* Creates a context for deriving encyption parameters.
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* See section 4.2 of
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* {@link https://tools.ietf.org/html/draft-ietf-httpbis-encryption-encoding-00}
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* From {@link https://github.com/GoogleChrome/push-encryption-node/blob/master/src/encrypt.js}
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*
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* @param $clientPublicKey string The client's public key
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* @param $serverPublicKey string Our public key
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* @return string
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* @throws \ErrorException
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*/
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private static function createContext($clientPublicKey, $serverPublicKey)
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{
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if (strlen($clientPublicKey) !== 65) {
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throw new \ErrorException('Invalid client public key length');
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}
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// This one should never happen, because it's our code that generates the key
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if (strlen($serverPublicKey) !== 65) {
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throw new \ErrorException('Invalid server public key length');
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}
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return chr(0).strlen($clientPublicKey).$clientPublicKey.strlen($serverPublicKey).$serverPublicKey;
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}
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/**
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* Returns an info record. See sections 3.2 and 3.3 of
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* {@link https://tools.ietf.org/html/draft-ietf-httpbis-encryption-encoding-00}
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* From {@link https://github.com/GoogleChrome/push-encryption-node/blob/master/src/encrypt.js}
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*
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* @param $type string The type of the info record
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* @param $context string The context for the record
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* @return string
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* @throws \ErrorException
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*/
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private static function createInfo($type, $context) {
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if (strlen($context) !== 135) {
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throw new \ErrorException('Context argument has invalid size');
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}
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return 'Content-Encoding: '.$type.chr(0).'P-256'.$context;
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}
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}

‎src/WebPush.php

Lines changed: 2 additions & 54 deletions
Original file line numberDiff line numberDiff line change
@@ -11,15 +11,11 @@
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namespace Minishlink\WebPush;
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use Base64Url\Base64Url;
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use Buzz\Browser;
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use Buzz\Client\AbstractClient;
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use Buzz\Client\MultiCurl;
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use Buzz\Exception\RequestException;
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use Buzz\Message\Response;
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use Mdanter\Ecc\Crypto\Key\PublicKey;
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use Mdanter\Ecc\EccFactory;
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use Mdanter\Ecc\Serializer\Point\UncompressedPointSerializer;
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class WebPush
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{
@@ -177,54 +173,6 @@ public function flush()
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return $completeSuccess ? true : $return;
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}
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180-
/**
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* @param string $userPublicKey MIME base 64 encoded
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* @param string $payload
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*
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* @return array
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*/
186-
private function encrypt($userPublicKey, $payload)
187-
{
188-
// initialize utilities
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$math = EccFactory::getAdapter();
190-
$keySerializer = new UncompressedPointSerializer($math);
191-
$curveGenerator = EccFactory::getNistCurves()->generator256();
192-
$curve = EccFactory::getNistCurves()->curve256();
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// get local key pair
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$localPrivateKeyObject = $curveGenerator->createPrivateKey();
196-
$localPublicKeyObject = $localPrivateKeyObject->getPublicKey();
197-
$localPublicKey = hex2bin($keySerializer->serialize($localPublicKeyObject->getPoint()));
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// get user public key object
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$userPublicKeyObject = new PublicKey($math, $curveGenerator, $keySerializer->unserialize($curve, bin2hex(base64_decode($userPublicKey))));
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// get shared secret from user public key and local private key
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$sharedSecret = $userPublicKeyObject->getPoint()->mul($localPrivateKeyObject->getSecret())->getX();
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// generate salt
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$salt = openssl_random_pseudo_bytes(16);
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// get encryption key
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$encryptionKey = hash_hmac('sha256', $salt, $sharedSecret, true);
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// encrypt
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$iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length('aes-128-gcm'));
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if (!$this->nativePayloadEncryptionSupport && $this->payloadEncryptionSupport) {
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list($encryptedText, $tag) = \Jose\Util\GCM::encrypt($encryptionKey, $iv, $payload, "");
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$cipherText = $encryptedText.$tag;
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} else {
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$cipherText = openssl_encrypt($payload, 'aes-128-gcm', $encryptionKey, false, $iv); // base 64 encoded
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}
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// return values in url safe base64
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return array(
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'localPublicKey' => Base64Url::encode($localPublicKey),
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'salt' => Base64Url::encode($salt),
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'cipherText' => Base64Url::encode($cipherText),
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);
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}
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private function sendToStandardEndpoints(array $notifications)
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{
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$responses = array();
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$userPublicKey = $notification->getUserPublicKey();
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if (isset($payload) && isset($userPublicKey) && ($this->payloadEncryptionSupport || $this->nativePayloadEncryptionSupport)) {
237-
$encrypted = $this->encrypt($userPublicKey, $payload);
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$encrypted = Encryption::encrypt($payload, $userPublicKey, null, $this->nativePayloadEncryptionSupport);
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$headers = array(
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'Content-Length' => strlen($encrypted['cipherText']),
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'Content-Type' => 'application/octet-stream',
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'Content-Encoding' => 'aesgcm128',
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'Content-Encoding' => 'aesgcm',
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'Encryption' => 'keyid="p256dh";salt="'.$encrypted['salt'].'"',
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'Crypto-Key' => 'keyid="p256dh";dh="'.$encrypted['localPublicKey'].'"',
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'TTL' => $this->TTL,

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