JWT::decode()   F
last analyzed

Complexity

Conditions 22
Paths 122

Size

Total Lines 86
Code Lines 46

Duplication

Lines 0
Ratio 0 %

Importance

Changes 0
Metric Value
cc 22
eloc 46
nc 122
nop 3
dl 0
loc 86
rs 3.9833
c 0
b 0
f 0

How to fix   Long Method    Complexity   

Long Method

Small methods make your code easier to understand, in particular if combined with a good name. Besides, if your method is small, finding a good name is usually much easier.

For example, if you find yourself adding comments to a method's body, this is usually a good sign to extract the commented part to a new method, and use the comment as a starting point when coming up with a good name for this new method.

Commonly applied refactorings include:

1
<?php
2
3
namespace Firebase\JWT;
4
5
use ArrayAccess;
6
use DateTime;
7
use DomainException;
8
use Exception;
9
use InvalidArgumentException;
10
use OpenSSLAsymmetricKey;
11
use OpenSSLCertificate;
12
use stdClass;
13
use UnexpectedValueException;
14
15
/**
16
 * JSON Web Token implementation, based on this spec:
17
 * https://tools.ietf.org/html/rfc7519
18
 *
19
 * PHP version 5
20
 *
21
 * @category Authentication
22
 * @package  Authentication_JWT
23
 * @author   Neuman Vong <[email protected]>
24
 * @author   Anant Narayanan <[email protected]>
25
 * @license  http://opensource.org/licenses/BSD-3-Clause 3-clause BSD
26
 * @link     https://github.com/firebase/php-jwt
27
 */
28
class JWT
29
{
30
    private const ASN1_INTEGER = 0x02;
31
    private const ASN1_SEQUENCE = 0x10;
32
    private const ASN1_BIT_STRING = 0x03;
33
34
    /**
35
     * When checking nbf, iat or expiration times,
36
     * we want to provide some extra leeway time to
37
     * account for clock skew.
38
     *
39
     * @var int
40
     */
41
    public static $leeway = 0;
42
43
    /**
44
     * Allow the current timestamp to be specified.
45
     * Useful for fixing a value within unit testing.
46
     * Will default to PHP time() value if null.
47
     *
48
     * @var ?int
49
     */
50
    public static $timestamp = null;
51
52
    /**
53
     * @var array<string, string[]>
54
     */
55
    public static $supported_algs = [
56
        'ES384' => ['openssl', 'SHA384'],
57
        'ES256' => ['openssl', 'SHA256'],
58
        'ES256K' => ['openssl', 'SHA256'],
59
        'HS256' => ['hash_hmac', 'SHA256'],
60
        'HS384' => ['hash_hmac', 'SHA384'],
61
        'HS512' => ['hash_hmac', 'SHA512'],
62
        'RS256' => ['openssl', 'SHA256'],
63
        'RS384' => ['openssl', 'SHA384'],
64
        'RS512' => ['openssl', 'SHA512'],
65
        'EdDSA' => ['sodium_crypto', 'EdDSA'],
66
    ];
67
68
    /**
69
     * Decodes a JWT string into a PHP object.
70
     *
71
     * @param string                 $jwt            The JWT
72
     * @param Key|ArrayAccess<string,Key>|array<string,Key> $keyOrKeyArray  The Key or associative array of key IDs
73
     *                                                                      (kid) to Key objects.
74
     *                                                                      If the algorithm used is asymmetric, this is
75
     *                                                                      the public key.
76
     *                                                                      Each Key object contains an algorithm and
77
     *                                                                      matching key.
78
     *                                                                      Supported algorithms are 'ES384','ES256',
79
     *                                                                      'HS256', 'HS384', 'HS512', 'RS256', 'RS384'
80
     *                                                                      and 'RS512'.
81
     * @param stdClass               $headers                               Optional. Populates stdClass with headers.
82
     *
83
     * @return stdClass The JWT's payload as a PHP object
84
     *
85
     * @throws InvalidArgumentException     Provided key/key-array was empty or malformed
86
     * @throws DomainException              Provided JWT is malformed
87
     * @throws UnexpectedValueException     Provided JWT was invalid
88
     * @throws SignatureInvalidException    Provided JWT was invalid because the signature verification failed
89
     * @throws BeforeValidException         Provided JWT is trying to be used before it's eligible as defined by 'nbf'
90
     * @throws BeforeValidException         Provided JWT is trying to be used before it's been created as defined by 'iat'
91
     * @throws ExpiredException             Provided JWT has since expired, as defined by the 'exp' claim
92
     *
93
     * @uses jsonDecode
94
     * @uses urlsafeB64Decode
95
     */
96
    public static function decode(
97
        string $jwt,
98
        $keyOrKeyArray,
99
        stdClass &$headers = null
100
    ): stdClass {
101
        // Validate JWT
102
        $timestamp = \is_null(static::$timestamp) ? \time() : static::$timestamp;
103
104
        if (empty($keyOrKeyArray)) {
105
            throw new InvalidArgumentException('Key may not be empty');
106
        }
107
        $tks = \explode('.', $jwt);
108
        if (\count($tks) !== 3) {
109
            throw new UnexpectedValueException('Wrong number of segments');
110
        }
111
        list($headb64, $bodyb64, $cryptob64) = $tks;
112
        $headerRaw = static::urlsafeB64Decode($headb64);
113
        if (null === ($header = static::jsonDecode($headerRaw))) {
114
            throw new UnexpectedValueException('Invalid header encoding');
115
        }
116
        if ($headers !== null) {
117
            $headers = $header;
118
        }
119
        $payloadRaw = static::urlsafeB64Decode($bodyb64);
120
        if (null === ($payload = static::jsonDecode($payloadRaw))) {
121
            throw new UnexpectedValueException('Invalid claims encoding');
122
        }
123
        if (\is_array($payload)) {
124
            // prevent PHP Fatal Error in edge-cases when payload is empty array
125
            $payload = (object) $payload;
126
        }
127
        if (!$payload instanceof stdClass) {
128
            throw new UnexpectedValueException('Payload must be a JSON object');
129
        }
130
        $sig = static::urlsafeB64Decode($cryptob64);
131
        if (empty($header->alg)) {
132
            throw new UnexpectedValueException('Empty algorithm');
133
        }
134
        if (empty(static::$supported_algs[$header->alg])) {
135
            throw new UnexpectedValueException('Algorithm not supported');
136
        }
137
138
        $key = self::getKey($keyOrKeyArray, property_exists($header, 'kid') ? $header->kid : null);
139
140
        // Check the algorithm
141
        if (!self::constantTimeEquals($key->getAlgorithm(), $header->alg)) {
142
            // See issue #351
143
            throw new UnexpectedValueException('Incorrect key for this algorithm');
144
        }
145
        if (\in_array($header->alg, ['ES256', 'ES256K', 'ES384'], true)) {
146
            // OpenSSL expects an ASN.1 DER sequence for ES256/ES256K/ES384 signatures
147
            $sig = self::signatureToDER($sig);
148
        }
149
        if (!self::verify("{$headb64}.{$bodyb64}", $sig, $key->getKeyMaterial(), $header->alg)) {
150
            throw new SignatureInvalidException('Signature verification failed');
151
        }
152
153
        // Check the nbf if it is defined. This is the time that the
154
        // token can actually be used. If it's not yet that time, abort.
155
        if (isset($payload->nbf) && floor($payload->nbf) > ($timestamp + static::$leeway)) {
156
            $ex = new BeforeValidException(
157
                'Cannot handle token with nbf prior to ' . \date(DateTime::ISO8601, (int) $payload->nbf)
158
            );
159
            $ex->setPayload($payload);
160
            throw $ex;
161
        }
162
163
        // Check that this token has been created before 'now'. This prevents
164
        // using tokens that have been created for later use (and haven't
165
        // correctly used the nbf claim).
166
        if (!isset($payload->nbf) && isset($payload->iat) && floor($payload->iat) > ($timestamp + static::$leeway)) {
167
            $ex = new BeforeValidException(
168
                'Cannot handle token with iat prior to ' . \date(DateTime::ISO8601, (int) $payload->iat)
169
            );
170
            $ex->setPayload($payload);
171
            throw $ex;
172
        }
173
174
        // Check if this token has expired.
175
        if (isset($payload->exp) && ($timestamp - static::$leeway) >= $payload->exp) {
176
            $ex = new ExpiredException('Expired token');
177
            $ex->setPayload($payload);
178
            throw $ex;
179
        }
180
181
        return $payload;
182
    }
183
184
    /**
185
     * Converts and signs a PHP array into a JWT string.
186
     *
187
     * @param array<mixed>          $payload PHP array
188
     * @param string|resource|OpenSSLAsymmetricKey|OpenSSLCertificate $key The secret key.
189
     * @param string                $alg     Supported algorithms are 'ES384','ES256', 'ES256K', 'HS256',
190
     *                                       'HS384', 'HS512', 'RS256', 'RS384', and 'RS512'
191
     * @param string                $keyId
192
     * @param array<string, string> $head    An array with header elements to attach
193
     *
194
     * @return string A signed JWT
195
     *
196
     * @uses jsonEncode
197
     * @uses urlsafeB64Encode
198
     */
199
    public static function encode(
200
        array $payload,
201
        $key,
202
        string $alg,
203
        string $keyId = null,
204
        array $head = null
205
    ): string {
206
        $header = ['typ' => 'JWT'];
207
        if (isset($head) && \is_array($head)) {
208
            $header = \array_merge($header, $head);
209
        }
210
        $header['alg'] = $alg;
211
        if ($keyId !== null) {
212
            $header['kid'] = $keyId;
213
        }
214
        $segments = [];
215
        $segments[] = static::urlsafeB64Encode((string) static::jsonEncode($header));
216
        $segments[] = static::urlsafeB64Encode((string) static::jsonEncode($payload));
217
        $signing_input = \implode('.', $segments);
218
219
        $signature = static::sign($signing_input, $key, $alg);
220
        $segments[] = static::urlsafeB64Encode($signature);
221
222
        return \implode('.', $segments);
223
    }
224
225
    /**
226
     * Sign a string with a given key and algorithm.
227
     *
228
     * @param string $msg  The message to sign
229
     * @param string|resource|OpenSSLAsymmetricKey|OpenSSLCertificate  $key  The secret key.
230
     * @param string $alg  Supported algorithms are 'EdDSA', 'ES384', 'ES256', 'ES256K', 'HS256',
231
     *                    'HS384', 'HS512', 'RS256', 'RS384', and 'RS512'
232
     *
233
     * @return string An encrypted message
234
     *
235
     * @throws DomainException Unsupported algorithm or bad key was specified
236
     */
237
    public static function sign(
238
        string $msg,
239
        $key,
240
        string $alg
241
    ): string {
242
        if (empty(static::$supported_algs[$alg])) {
243
            throw new DomainException('Algorithm not supported');
244
        }
245
        list($function, $algorithm) = static::$supported_algs[$alg];
246
        switch ($function) {
247
            case 'hash_hmac':
248
                if (!\is_string($key)) {
249
                    throw new InvalidArgumentException('key must be a string when using hmac');
250
                }
251
                return \hash_hmac($algorithm, $msg, $key, true);
252
            case 'openssl':
253
                $signature = '';
254
                $success = \openssl_sign($msg, $signature, $key, $algorithm); // @phpstan-ignore-line
255
                if (!$success) {
256
                    throw new DomainException('OpenSSL unable to sign data');
257
                }
258
                if ($alg === 'ES256' || $alg === 'ES256K') {
259
                    $signature = self::signatureFromDER($signature, 256);
260
                } elseif ($alg === 'ES384') {
261
                    $signature = self::signatureFromDER($signature, 384);
262
                }
263
                return $signature;
264
            case 'sodium_crypto':
265
                if (!\function_exists('sodium_crypto_sign_detached')) {
266
                    throw new DomainException('libsodium is not available');
267
                }
268
                if (!\is_string($key)) {
269
                    throw new InvalidArgumentException('key must be a string when using EdDSA');
270
                }
271
                try {
272
                    // The last non-empty line is used as the key.
273
                    $lines = array_filter(explode("\n", $key));
274
                    $key = base64_decode((string) end($lines));
275
                    if (\strlen($key) === 0) {
276
                        throw new DomainException('Key cannot be empty string');
277
                    }
278
                    return sodium_crypto_sign_detached($msg, $key);
279
                } catch (Exception $e) {
280
                    throw new DomainException($e->getMessage(), 0, $e);
281
                }
282
        }
283
284
        throw new DomainException('Algorithm not supported');
285
    }
286
287
    /**
288
     * Verify a signature with the message, key and method. Not all methods
289
     * are symmetric, so we must have a separate verify and sign method.
290
     *
291
     * @param string $msg         The original message (header and body)
292
     * @param string $signature   The original signature
293
     * @param string|resource|OpenSSLAsymmetricKey|OpenSSLCertificate  $keyMaterial For Ed*, ES*, HS*, a string key works. for RS*, must be an instance of OpenSSLAsymmetricKey
294
     * @param string $alg         The algorithm
295
     *
296
     * @return bool
297
     *
298
     * @throws DomainException Invalid Algorithm, bad key, or OpenSSL failure
299
     */
300
    private static function verify(
301
        string $msg,
302
        string $signature,
303
        $keyMaterial,
304
        string $alg
305
    ): bool {
306
        if (empty(static::$supported_algs[$alg])) {
307
            throw new DomainException('Algorithm not supported');
308
        }
309
310
        list($function, $algorithm) = static::$supported_algs[$alg];
311
        switch ($function) {
312
            case 'openssl':
313
                $success = \openssl_verify($msg, $signature, $keyMaterial, $algorithm); // @phpstan-ignore-line
314
                if ($success === 1) {
315
                    return true;
316
                }
317
                if ($success === 0) {
318
                    return false;
319
                }
320
                // returns 1 on success, 0 on failure, -1 on error.
321
                throw new DomainException(
322
                    'OpenSSL error: ' . \openssl_error_string()
323
                );
324
            case 'sodium_crypto':
325
                if (!\function_exists('sodium_crypto_sign_verify_detached')) {
326
                    throw new DomainException('libsodium is not available');
327
                }
328
                if (!\is_string($keyMaterial)) {
329
                    throw new InvalidArgumentException('key must be a string when using EdDSA');
330
                }
331
                try {
332
                    // The last non-empty line is used as the key.
333
                    $lines = array_filter(explode("\n", $keyMaterial));
334
                    $key = base64_decode((string) end($lines));
335
                    if (\strlen($key) === 0) {
336
                        throw new DomainException('Key cannot be empty string');
337
                    }
338
                    if (\strlen($signature) === 0) {
339
                        throw new DomainException('Signature cannot be empty string');
340
                    }
341
                    return sodium_crypto_sign_verify_detached($signature, $msg, $key);
342
                } catch (Exception $e) {
343
                    throw new DomainException($e->getMessage(), 0, $e);
344
                }
345
            case 'hash_hmac':
346
            default:
347
                if (!\is_string($keyMaterial)) {
348
                    throw new InvalidArgumentException('key must be a string when using hmac');
349
                }
350
                $hash = \hash_hmac($algorithm, $msg, $keyMaterial, true);
351
                return self::constantTimeEquals($hash, $signature);
352
        }
353
    }
354
355
    /**
356
     * Decode a JSON string into a PHP object.
357
     *
358
     * @param string $input JSON string
359
     *
360
     * @return mixed The decoded JSON string
361
     *
362
     * @throws DomainException Provided string was invalid JSON
363
     */
364
    public static function jsonDecode(string $input)
365
    {
366
        $obj = \json_decode($input, false, 512, JSON_BIGINT_AS_STRING);
367
368
        if ($errno = \json_last_error()) {
369
            self::handleJsonError($errno);
370
        } elseif ($obj === null && $input !== 'null') {
371
            throw new DomainException('Null result with non-null input');
372
        }
373
        return $obj;
374
    }
375
376
    /**
377
     * Encode a PHP array into a JSON string.
378
     *
379
     * @param array<mixed> $input A PHP array
380
     *
381
     * @return string JSON representation of the PHP array
382
     *
383
     * @throws DomainException Provided object could not be encoded to valid JSON
384
     */
385
    public static function jsonEncode(array $input): string
386
    {
387
        if (PHP_VERSION_ID >= 50400) {
388
            $json = \json_encode($input, \JSON_UNESCAPED_SLASHES);
389
        } else {
390
            // PHP 5.3 only
391
            $json = \json_encode($input);
392
        }
393
        if ($errno = \json_last_error()) {
394
            self::handleJsonError($errno);
395
        } elseif ($json === 'null') {
396
            throw new DomainException('Null result with non-null input');
397
        }
398
        if ($json === false) {
399
            throw new DomainException('Provided object could not be encoded to valid JSON');
400
        }
401
        return $json;
402
    }
403
404
    /**
405
     * Decode a string with URL-safe Base64.
406
     *
407
     * @param string $input A Base64 encoded string
408
     *
409
     * @return string A decoded string
410
     *
411
     * @throws InvalidArgumentException invalid base64 characters
412
     */
413
    public static function urlsafeB64Decode(string $input): string
414
    {
415
        return \base64_decode(self::convertBase64UrlToBase64($input));
416
    }
417
418
    /**
419
     * Convert a string in the base64url (URL-safe Base64) encoding to standard base64.
420
     *
421
     * @param string $input A Base64 encoded string with URL-safe characters (-_ and no padding)
422
     *
423
     * @return string A Base64 encoded string with standard characters (+/) and padding (=), when
424
     * needed.
425
     *
426
     * @see https://www.rfc-editor.org/rfc/rfc4648
427
     */
428
    public static function convertBase64UrlToBase64(string $input): string
429
    {
430
        $remainder = \strlen($input) % 4;
431
        if ($remainder) {
432
            $padlen = 4 - $remainder;
433
            $input .= \str_repeat('=', $padlen);
434
        }
435
        return \strtr($input, '-_', '+/');
436
    }
437
438
    /**
439
     * Encode a string with URL-safe Base64.
440
     *
441
     * @param string $input The string you want encoded
442
     *
443
     * @return string The base64 encode of what you passed in
444
     */
445
    public static function urlsafeB64Encode(string $input): string
446
    {
447
        return \str_replace('=', '', \strtr(\base64_encode($input), '+/', '-_'));
448
    }
449
450
451
    /**
452
     * Determine if an algorithm has been provided for each Key
453
     *
454
     * @param Key|ArrayAccess<string,Key>|array<string,Key> $keyOrKeyArray
455
     * @param string|null            $kid
456
     *
457
     * @throws UnexpectedValueException
458
     *
459
     * @return Key
460
     */
461
    private static function getKey(
462
        $keyOrKeyArray,
463
        ?string $kid
464
    ): Key {
465
        if ($keyOrKeyArray instanceof Key) {
466
            return $keyOrKeyArray;
467
        }
468
469
        if (empty($kid) && $kid !== '0') {
470
            throw new UnexpectedValueException('"kid" empty, unable to lookup correct key');
471
        }
472
473
        if ($keyOrKeyArray instanceof CachedKeySet) {
474
            // Skip "isset" check, as this will automatically refresh if not set
475
            return $keyOrKeyArray[$kid];
476
        }
477
478
        if (!isset($keyOrKeyArray[$kid])) {
479
            throw new UnexpectedValueException('"kid" invalid, unable to lookup correct key');
480
        }
481
482
        return $keyOrKeyArray[$kid];
483
    }
484
485
    /**
486
     * @param string $left  The string of known length to compare against
487
     * @param string $right The user-supplied string
488
     * @return bool
489
     */
490
    public static function constantTimeEquals(string $left, string $right): bool
491
    {
492
        if (\function_exists('hash_equals')) {
493
            return \hash_equals($left, $right);
494
        }
495
        $len = \min(self::safeStrlen($left), self::safeStrlen($right));
496
497
        $status = 0;
498
        for ($i = 0; $i < $len; $i++) {
499
            $status |= (\ord($left[$i]) ^ \ord($right[$i]));
500
        }
501
        $status |= (self::safeStrlen($left) ^ self::safeStrlen($right));
502
503
        return ($status === 0);
504
    }
505
506
    /**
507
     * Helper method to create a JSON error.
508
     *
509
     * @param int $errno An error number from json_last_error()
510
     *
511
     * @throws DomainException
512
     *
513
     * @return void
514
     */
515
    private static function handleJsonError(int $errno): void
516
    {
517
        $messages = [
518
            JSON_ERROR_DEPTH => 'Maximum stack depth exceeded',
519
            JSON_ERROR_STATE_MISMATCH => 'Invalid or malformed JSON',
520
            JSON_ERROR_CTRL_CHAR => 'Unexpected control character found',
521
            JSON_ERROR_SYNTAX => 'Syntax error, malformed JSON',
522
            JSON_ERROR_UTF8 => 'Malformed UTF-8 characters' //PHP >= 5.3.3
523
        ];
524
        throw new DomainException(
525
            isset($messages[$errno])
526
            ? $messages[$errno]
527
            : 'Unknown JSON error: ' . $errno
528
        );
529
    }
530
531
    /**
532
     * Get the number of bytes in cryptographic strings.
533
     *
534
     * @param string $str
535
     *
536
     * @return int
537
     */
538
    private static function safeStrlen(string $str): int
539
    {
540
        if (\function_exists('mb_strlen')) {
541
            return \mb_strlen($str, '8bit');
542
        }
543
        return \strlen($str);
544
    }
545
546
    /**
547
     * Convert an ECDSA signature to an ASN.1 DER sequence
548
     *
549
     * @param   string $sig The ECDSA signature to convert
550
     * @return  string The encoded DER object
551
     */
552
    private static function signatureToDER(string $sig): string
553
    {
554
        // Separate the signature into r-value and s-value
555
        $length = max(1, (int) (\strlen($sig) / 2));
556
        list($r, $s) = \str_split($sig, $length);
557
558
        // Trim leading zeros
559
        $r = \ltrim($r, "\x00");
560
        $s = \ltrim($s, "\x00");
561
562
        // Convert r-value and s-value from unsigned big-endian integers to
563
        // signed two's complement
564
        if (\ord($r[0]) > 0x7f) {
565
            $r = "\x00" . $r;
566
        }
567
        if (\ord($s[0]) > 0x7f) {
568
            $s = "\x00" . $s;
569
        }
570
571
        return self::encodeDER(
572
            self::ASN1_SEQUENCE,
573
            self::encodeDER(self::ASN1_INTEGER, $r) .
574
            self::encodeDER(self::ASN1_INTEGER, $s)
575
        );
576
    }
577
578
    /**
579
     * Encodes a value into a DER object.
580
     *
581
     * @param   int     $type DER tag
582
     * @param   string  $value the value to encode
583
     *
584
     * @return  string  the encoded object
585
     */
586
    private static function encodeDER(int $type, string $value): string
587
    {
588
        $tag_header = 0;
589
        if ($type === self::ASN1_SEQUENCE) {
590
            $tag_header |= 0x20;
591
        }
592
593
        // Type
594
        $der = \chr($tag_header | $type);
595
596
        // Length
597
        $der .= \chr(\strlen($value));
598
599
        return $der . $value;
600
    }
601
602
    /**
603
     * Encodes signature from a DER object.
604
     *
605
     * @param   string  $der binary signature in DER format
606
     * @param   int     $keySize the number of bits in the key
607
     *
608
     * @return  string  the signature
609
     */
610
    private static function signatureFromDER(string $der, int $keySize): string
611
    {
612
        // OpenSSL returns the ECDSA signatures as a binary ASN.1 DER SEQUENCE
613
        list($offset, $_) = self::readDER($der);
614
        list($offset, $r) = self::readDER($der, $offset);
615
        list($offset, $s) = self::readDER($der, $offset);
616
617
        // Convert r-value and s-value from signed two's compliment to unsigned
618
        // big-endian integers
619
        $r = \ltrim($r, "\x00");
620
        $s = \ltrim($s, "\x00");
621
622
        // Pad out r and s so that they are $keySize bits long
623
        $r = \str_pad($r, $keySize / 8, "\x00", STR_PAD_LEFT);
624
        $s = \str_pad($s, $keySize / 8, "\x00", STR_PAD_LEFT);
625
626
        return $r . $s;
627
    }
628
629
    /**
630
     * Reads binary DER-encoded data and decodes into a single object
631
     *
632
     * @param string $der the binary data in DER format
633
     * @param int $offset the offset of the data stream containing the object
634
     * to decode
635
     *
636
     * @return array{int, string|null} the new offset and the decoded object
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637
     */
638
    private static function readDER(string $der, int $offset = 0): array
639
    {
640
        $pos = $offset;
641
        $size = \strlen($der);
642
        $constructed = (\ord($der[$pos]) >> 5) & 0x01;
643
        $type = \ord($der[$pos++]) & 0x1f;
644
645
        // Length
646
        $len = \ord($der[$pos++]);
647
        if ($len & 0x80) {
648
            $n = $len & 0x1f;
649
            $len = 0;
650
            while ($n-- && $pos < $size) {
651
                $len = ($len << 8) | \ord($der[$pos++]);
652
            }
653
        }
654
655
        // Value
656
        if ($type === self::ASN1_BIT_STRING) {
657
            $pos++; // Skip the first contents octet (padding indicator)
658
            $data = \substr($der, $pos, $len - 1);
659
            $pos += $len - 1;
660
        } elseif (!$constructed) {
661
            $data = \substr($der, $pos, $len);
662
            $pos += $len;
663
        } else {
664
            $data = null;
665
        }
666
667
        return [$pos, $data];
668
    }
669
}
670