1<?php
2/*
3 * Copyright 2019 Google LLC
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License");
6 * you may not use this file except in compliance with the License.
7 * You may obtain a copy of the License at
8 *
9 *     http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18namespace Google\Auth;
19
20use phpseclib\Crypt\RSA;
21
22/**
23 * Sign a string using a Service Account private key.
24 */
25trait ServiceAccountSignerTrait
26{
27    /**
28     * Sign a string using the service account private key.
29     *
30     * @param string $stringToSign
31     * @param bool $forceOpenssl Whether to use OpenSSL regardless of
32     *        whether phpseclib is installed. **Defaults to** `false`.
33     * @return string
34     */
35    public function signBlob($stringToSign, $forceOpenssl = false)
36    {
37        $privateKey = $this->auth->getSigningKey();
38
39        $signedString = '';
40        if (class_exists('\\phpseclib\\Crypt\\RSA') && !$forceOpenssl) {
41            $rsa = new RSA();
42            $rsa->loadKey($privateKey);
43            $rsa->setSignatureMode(RSA::SIGNATURE_PKCS1);
44            $rsa->setHash('sha256');
45
46            $signedString = $rsa->sign($stringToSign);
47        } elseif (extension_loaded('openssl')) {
48            openssl_sign($stringToSign, $signedString, $privateKey, 'sha256WithRSAEncryption');
49        } else {
50            // @codeCoverageIgnoreStart
51            throw new \RuntimeException('OpenSSL is not installed.');
52        }
53        // @codeCoverageIgnoreEnd
54
55        return base64_encode($signedString);
56    }
57}
58