JWK.php 5.48 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
<?php

namespace Firebase\JWT;

use DomainException;
use InvalidArgumentException;
use UnexpectedValueException;

/**
 * JSON Web Key implementation, based on this spec:
 * https://tools.ietf.org/html/draft-ietf-jose-json-web-key-41
 *
 * PHP version 5
 *
 * @category Authentication
 * @package  Authentication_JWT
 * @author   Bui Sy Nguyen <nguyenbs@gmail.com>
 * @license  http://opensource.org/licenses/BSD-3-Clause 3-clause BSD
 * @link     https://github.com/firebase/php-jwt
 */
class JWK
{
    /**
     * Parse a set of JWK keys
     *
     * @param array $jwks The JSON Web Key Set as an associative array
     *
     * @return array An associative array that represents the set of keys
     *
     * @throws InvalidArgumentException     Provided JWK Set is empty
     * @throws UnexpectedValueException     Provided JWK Set was invalid
     * @throws DomainException              OpenSSL failure
     *
     * @uses parseKey
     */
    public static function parseKeySet(array $jwks)
    {
        $keys = array();

        if (!isset($jwks['keys'])) {
            throw new UnexpectedValueException('"keys" member must exist in the JWK Set');
        }
        if (empty($jwks['keys'])) {
            throw new InvalidArgumentException('JWK Set did not contain any keys');
        }

        foreach ($jwks['keys'] as $k => $v) {
            $kid = isset($v['kid']) ? $v['kid'] : $k;
            if ($key = self::parseKey($v)) {
                $keys[$kid] = $key;
            }
        }

        if (0 === \count($keys)) {
            throw new UnexpectedValueException('No supported algorithms found in JWK Set');
        }

        return $keys;
    }

    /**
     * Parse a JWK key
     *
     * @param array $jwk An individual JWK
     *
     * @return resource|array An associative array that represents the key
     *
     * @throws InvalidArgumentException     Provided JWK is empty
     * @throws UnexpectedValueException     Provided JWK was invalid
     * @throws DomainException              OpenSSL failure
     *
     * @uses createPemFromModulusAndExponent
     */
    private static function parseKey(array $jwk)
    {
        if (empty($jwk)) {
            throw new InvalidArgumentException('JWK must not be empty');
        }
        if (!isset($jwk['kty'])) {
            throw new UnexpectedValueException('JWK must contain a "kty" parameter');
        }

        switch ($jwk['kty']) {
            case 'RSA':
                if (\array_key_exists('d', $jwk)) {
                    throw new UnexpectedValueException('RSA private keys are not supported');
                }
                if (!isset($jwk['n']) || !isset($jwk['e'])) {
                    throw new UnexpectedValueException('RSA keys must contain values for both "n" and "e"');
                }

                $pem = self::createPemFromModulusAndExponent($jwk['n'], $jwk['e']);
                $publicKey = \openssl_pkey_get_public($pem);
                if (false === $publicKey) {
                    throw new DomainException(
                        'OpenSSL error: ' . \openssl_error_string()
                    );
                }
                return $publicKey;
            default:
                // Currently only RSA is supported
                break;
        }
    }

    /**
     * Create a public key represented in PEM format from RSA modulus and exponent information
     *
     * @param string $n The RSA modulus encoded in Base64
     * @param string $e The RSA exponent encoded in Base64
     *
     * @return string The RSA public key represented in PEM format
     *
     * @uses encodeLength
     */
    private static function createPemFromModulusAndExponent($n, $e)
    {
        $modulus = JWT::urlsafeB64Decode($n);
        $publicExponent = JWT::urlsafeB64Decode($e);

        $components = array(
            'modulus' => \pack('Ca*a*', 2, self::encodeLength(\strlen($modulus)), $modulus),
            'publicExponent' => \pack('Ca*a*', 2, self::encodeLength(\strlen($publicExponent)), $publicExponent)
        );

        $rsaPublicKey = \pack(
            'Ca*a*a*',
            48,
            self::encodeLength(\strlen($components['modulus']) + \strlen($components['publicExponent'])),
            $components['modulus'],
            $components['publicExponent']
        );

        // sequence(oid(1.2.840.113549.1.1.1), null)) = rsaEncryption.
        $rsaOID = \pack('H*', '300d06092a864886f70d0101010500'); // hex version of MA0GCSqGSIb3DQEBAQUA
        $rsaPublicKey = \chr(0) . $rsaPublicKey;
        $rsaPublicKey = \chr(3) . self::encodeLength(\strlen($rsaPublicKey)) . $rsaPublicKey;

        $rsaPublicKey = \pack(
            'Ca*a*',
            48,
            self::encodeLength(\strlen($rsaOID . $rsaPublicKey)),
            $rsaOID . $rsaPublicKey
        );

        $rsaPublicKey = "-----BEGIN PUBLIC KEY-----\r\n" .
            \chunk_split(\base64_encode($rsaPublicKey), 64) .
            '-----END PUBLIC KEY-----';

        return $rsaPublicKey;
    }

    /**
     * DER-encode the length
     *
     * DER supports lengths up to (2**8)**127, however, we'll only support lengths up to (2**8)**4.  See
     * {@link http://itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf#p=13 X.690 paragraph 8.1.3} for more information.
     *
     * @param int $length
     * @return string
     */
    private static function encodeLength($length)
    {
        if ($length <= 0x7F) {
            return \chr($length);
        }

        $temp = \ltrim(\pack('N', $length), \chr(0));

        return \pack('Ca*', 0x80 | \strlen($temp), $temp);
    }
}