jwt.php

<?php
namespace Bitrix\Main\Web;
 
use \DomainException;
use \InvalidArgumentException;
use \UnexpectedValueException;
use \DateTime;
 
class JWT
{
    const ASN1_INTEGER = 0x02;
    const ASN1_SEQUENCE = 0x10;
    const ASN1_BIT_STRING = 0x03;
 
    public static $leeway = 0;
 
    public static $timestamp = null;
 
    public static $supported_algs = array(
        'ES256' => array('openssl', 'SHA256'),
        'HS256' => array('hash_hmac', 'SHA256'),
        'HS384' => array('hash_hmac', 'SHA384'),
        'HS512' => array('hash_hmac', 'SHA512'),
        'RS256' => array('openssl', 'SHA256'),
        'RS384' => array('openssl', 'SHA384'),
        'RS512' => array('openssl', 'SHA512'),
    );
 
    public static function decode($jwt, $key, array $allowed_algs = array())
    {
        $timestamp = is_null(static::$timestamp) ? time() : static::$timestamp;
 
        if (empty($key)) {
            throw new InvalidArgumentException('Key may not be empty');
        }
        $tks = explode('.', $jwt);
        if (count($tks) != 3) {
            throw new UnexpectedValueException('Wrong number of segments');
        }
        list($headb64, $bodyb64, $cryptob64) = $tks;
        if (null === ($header = static::jsonDecode(static::urlsafeB64Decode($headb64)))) {
            throw new UnexpectedValueException('Invalid header encoding');
        }
        if (null === $payload = static::jsonDecode(static::urlsafeB64Decode($bodyb64))) {
            throw new UnexpectedValueException('Invalid claims encoding');
        }
        if (false === ($sig = static::urlsafeB64Decode($cryptob64))) {
            throw new UnexpectedValueException('Invalid signature encoding');
        }
        if (empty($header->alg)) {
            throw new UnexpectedValueException('Empty algorithm');
        }
        if (empty(static::$supported_algs[$header->alg])) {
            throw new UnexpectedValueException('Algorithm not supported');
        }
        if (!in_array($header->alg, $allowed_algs)) {
            throw new UnexpectedValueException('Algorithm not allowed');
        }
        if ($header->alg === 'ES256') {
            // OpenSSL expects an ASN.1 DER sequence for ES256 signatures
            $sig = self::signatureToDER($sig);
        }
 
        if (is_array($key) || $key instanceof \ArrayAccess) {
            if (isset($header->kid)) {
                if (!isset($key[$header->kid])) {
                    throw new UnexpectedValueException('"kid" invalid, unable to lookup correct key');
                }
                $key = $key[$header->kid];
            } else {
                throw new UnexpectedValueException('"kid" empty, unable to lookup correct key');
            }
        }
 
        // Check the signature
        if (!static::verify("$headb64.$bodyb64", $sig, $key, $header->alg)) {
            throw new UnexpectedValueException('Signature verification failed');
        }
 
        // Check the nbf if it is defined. This is the time that the
        // token can actually be used. If it's not yet that time, abort.
        if (isset($payload->nbf) && $payload->nbf > ($timestamp + static::$leeway)) {
            throw new UnexpectedValueException(
                'Cannot handle token prior to ' . date(DateTime::ISO8601, $payload->nbf)
            );
        }
 
        // Check that this token has been created before 'now'. This prevents
        // using tokens that have been created for later use (and haven't
        // correctly used the nbf claim).
        if (isset($payload->iat) && $payload->iat > ($timestamp + static::$leeway)) {
            throw new UnexpectedValueException(
                'Cannot handle token prior to ' . date(DateTime::ISO8601, $payload->iat)
            );
        }
 
        // Check if this token has expired.
        if (isset($payload->exp) && ($timestamp - static::$leeway) >= $payload->exp) {
            throw new UnexpectedValueException('Expired token');
        }
 
        return $payload;
    }
 
    public static function encode($payload, $key, $alg = 'HS256', $keyId = null, $head = null)
    {
        $header = array('typ' => 'JWT', 'alg' => $alg);
        if ($keyId !== null) {
            $header['kid'] = $keyId;
        }
        if (isset($head) && is_array($head)) {
            $header = array_merge($head, $header);
        }
        $segments = array();
        $segments[] = static::urlsafeB64Encode(static::jsonEncode($header));
        $segments[] = static::urlsafeB64Encode(static::jsonEncode($payload));
        $signing_input = implode('.', $segments);
 
        $signature = static::sign($signing_input, $key, $alg);
        $segments[] = static::urlsafeB64Encode($signature);
 
        return implode('.', $segments);
    }
 
    public static function sign($msg, $key, $alg = 'HS256')
    {
        if (empty(static::$supported_algs[$alg])) {
            throw new DomainException('Algorithm not supported');
        }
        list($function, $algorithm) = static::$supported_algs[$alg];
        switch ($function) {
            case 'hash_hmac':
                return hash_hmac($algorithm, $msg, $key, true);
            case 'openssl':
                $signature = '';
                $success = openssl_sign($msg, $signature, $key, $algorithm);
                if (!$success) {
                    throw new DomainException("OpenSSL unable to sign data");
                } else {
                    if ($alg === 'ES256') {
                        $signature = self::signatureFromDER($signature, 256);
                    }
                    return $signature;
                }
        }
    }
 
    private static function verify($msg, $signature, $key, $alg)
    {
        if (empty(static::$supported_algs[$alg])) {
            throw new DomainException('Algorithm not supported');
        }
 
        list($function, $algorithm) = static::$supported_algs[$alg];
        switch ($function) {
            case 'openssl':
                $success = openssl_verify($msg, $signature, $key, $algorithm);
                if ($success === 1) {
                    return true;
                } elseif ($success === 0) {
                    return false;
                }
                // returns 1 on success, 0 on failure, -1 on error.
                throw new DomainException(
                    'OpenSSL error: ' . openssl_error_string()
                );
            case 'hash_hmac':
            default:
                $hash = hash_hmac($algorithm, $msg, $key, true);
                if (function_exists('hash_equals')) {
                    return hash_equals($signature, $hash);
                }
                $len = min(strlen($signature), strlen($hash));
 
                $status = 0;
                for ($i = 0; $i < $len; $i++) {
                    $status |= (ord($signature[$i]) ^ ord($hash[$i]));
                }
                $status |= (strlen($signature) ^ strlen($hash));
 
                return ($status === 0);
        }
    }
 
    public static function jsonDecode($input)
    {
        if (version_compare(PHP_VERSION, '5.4.0', '>=') && !(defined('JSON_C_VERSION') && PHP_INT_SIZE > 4)) {
            $obj = json_decode($input, false, 512, JSON_BIGINT_AS_STRING);
        } else {
            $max_int_length = strlen((string) PHP_INT_MAX) - 1;
            $json_without_bigints = preg_replace('/:\s*(-?\d{'.$max_int_length.',})/', ': "$1"', $input);
            $obj = json_decode($json_without_bigints);
        }
 
        if ($errno = json_last_error()) {
            static::handleJsonError($errno);
        } elseif ($obj === null && $input !== 'null') {
            throw new DomainException('Null result with non-null input');
        }
        return $obj;
    }
 
    public static function jsonEncode($input)
    {
        $json = json_encode($input);
        if ($errno = json_last_error()) {
            static::handleJsonError($errno);
        } elseif ($json === 'null' && $input !== null) {
            throw new DomainException('Null result with non-null input');
        }
        return $json;
    }
 
    public static function urlsafeB64Decode($input)
    {
        $remainder = strlen($input) % 4;
        if ($remainder) {
            $padlen = 4 - $remainder;
            $input .= str_repeat('=', $padlen);
        }
        return base64_decode(strtr($input, '-_', '+/'));
    }
 
    public static function urlsafeB64Encode($input)
    {
        return str_replace('=', '', strtr(base64_encode($input), '+/', '-_'));
    }
 
    private static function handleJsonError($errno)
    {
        $messages = array(
            JSON_ERROR_DEPTH => 'Maximum stack depth exceeded',
            JSON_ERROR_STATE_MISMATCH => 'Invalid or malformed JSON',
            JSON_ERROR_CTRL_CHAR => 'Unexpected control character found',
            JSON_ERROR_SYNTAX => 'Syntax error, malformed JSON',
            JSON_ERROR_UTF8 => 'Malformed UTF-8 characters' //PHP >= 5.3.3
        );
        throw new DomainException(
            $messages[$errno] ?? 'Unknown JSON error: '.$errno
        );
    }
 
    private static function signatureToDER($sig)
    {
        // Separate the signature into r-value and s-value
        list($r, $s) = str_split($sig, (int) (strlen($sig) / 2));
 
        // Trim leading zeros
        $r = ltrim($r, "\x00");
        $s = ltrim($s, "\x00");
 
        // Convert r-value and s-value from unsigned big-endian integers to
        // signed two's complement
        if (ord($r[0]) > 0x7f) {
            $r = "\x00" . $r;
        }
        if (ord($s[0]) > 0x7f) {
            $s = "\x00" . $s;
        }
 
        return self::encodeDER(
            self::ASN1_SEQUENCE,
            self::encodeDER(self::ASN1_INTEGER, $r) .
            self::encodeDER(self::ASN1_INTEGER, $s)
        );
    }
 
    private static function encodeDER($type, $value)
    {
        $tag_header = 0;
        if ($type === self::ASN1_SEQUENCE) {
            $tag_header |= 0x20;
        }
 
        // Type
        $der = chr($tag_header | $type);
 
        // Length
        $der .= chr(strlen($value));
 
        return $der . $value;
    }
 
    private static function signatureFromDER($der, $keySize)
    {
        // OpenSSL returns the ECDSA signatures as a binary ASN.1 DER SEQUENCE
        list($offset, $_) = self::readDER($der);
        list($offset, $r) = self::readDER($der, $offset);
        list($offset, $s) = self::readDER($der, $offset);
 
        // Convert r-value and s-value from signed two's compliment to unsigned
        // big-endian integers
        $r = ltrim($r, "\x00");
        $s = ltrim($s, "\x00");
 
        // Pad out r and s so that they are $keySize bits long
        $r = str_pad($r, $keySize / 8, "\x00", STR_PAD_LEFT);
        $s = str_pad($s, $keySize / 8, "\x00", STR_PAD_LEFT);
 
        return $r . $s;
    }
 
    private static function readDER($der, $offset = 0)
    {
        $pos = $offset;
        $size = strlen($der);
        $constructed = (ord($der[$pos]) >> 5) & 0x01;
        $type = ord($der[$pos++]) & 0x1f;
 
        // Length
        $len = ord($der[$pos++]);
        if ($len & 0x80) {
            $n = $len & 0x1f;
            $len = 0;
            while ($n-- && $pos < $size) {
                $len = ($len << 8) | ord($der[$pos++]);
            }
        }
 
        // Value
        if ($type == self::ASN1_BIT_STRING) {
            $pos++; // Skip the first contents octet (padding indicator)
            $data = substr($der, $pos, $len - 1);
            $pos += $len - 1;
        } elseif (!$constructed) {
            $data = substr($der, $pos, $len);
            $pos += $len;
        } else {
            $data = null;
        }
 
        return array($pos, $data);
    }
}