PHP使用 JWT进行登录

一、用户认证问题

最初互联网用户认证一般流程如下：

1、用户登录，向服务器发送用户名和密码。

2、服务器验证用户信息通过后，在当前对话（session）里面保存相关数据，比如用户角色、登录时间等等。

3、服务器向用户返回一个 session_id，客户端获取后将这个session_id写入 Cookie。

4、用户随后的每一次请求，都会通过 Cookie，将 session_id 传回服务器。

5、服务器收到 session_id，找到前期保存的数据，由此得知用户的身份。

这种模式的问题在于：

1.扩展性不好。单机当然没有问题，如果是服务器集群，或者是跨域的服务导向架构，就要求 session 数据共享，每台服务器都能够读取 session

2.服务端为了存贮session同时快速的获取session，一般会选择将其存储在内存中，消耗服务器内存资源。

 

JWT 便是这些问题的一个解决方案：服务端不再保存任何客户数据，而是在用户最开始登录时生成一个令牌并返回给客户端，客户端每次请求带上令牌，服务端便知道请求的对象时谁，真正做到了无状态。

 

二、JWT(JSON Web Token)

JWT 的原理是，服务器认证以后，生成一个 JSON 对象。以后，用户与服务端通信的时候，都要发回这个 JSON 对象。服务器完全只靠这个对象认定用户身份。为了防止用户篡改数据，服务器在生成这个对象的时候，会加上签名并加密。

JWT 的最大缺点是，由于服务器不保存 session 状态，因此无法在使用过程中废止某个 token，或者更改 token 的权限。也就是说，一旦 JWT 签发了，在到期之前就会始终有效，除非服务器部署额外的逻辑。

也是由于这个原因，无法实现动态令牌效果，即在用户持续使用阶段不废止令牌，而在用户停止操作一段时间后废除令牌。

<?php

namespace app\home\controller;

use \DomainException;
use \InvalidArgumentException;
use \UnexpectedValueException;
use \DateTime;

class Jwt
{
    const ASN1_INTEGER = 0x02;
    const ASN1_SEQUENCE = 0x10;
    const ASN1_BIT_STRING = 0x03;

    //加密密钥
    public static $key = 'qwerqwr12341234brqbwbsdafa';
    //有效期检查
    public static $leeway = 0;

    //允许指定当前时间戳，默认为PHP的time()
    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'),
    );

    /**
     * 将字符串编码为PHP对象
     * @param string $jwt 原始未加密字串
     * @param string|array|resource $key 加密钥匙，如果使用的时非对称加密，这里需要传输公钥
     * @param array $allowed_algs 支持的验证算法列表
     * @return object The JWT's payload as a PHP object
     * @throws UnexpectedValueException     Provided JWT was invalid
     * @uses jsonDecode
     * @uses urlsafeB64Decode
     */
    public static function decode($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');
            }
        }
        //  检查签名
        if (!static::verify("$headb64.$bodyb64", $sig, $key, $header->alg)) {
            throw new \UnexpectedValueException('Signature verification failed');
        }
        // 检查是否到了起作用的时间，未到则禁止
        if (isset($payload->nbf) && $payload->nbf > ($timestamp + static::$leeway)) {
            throw new \UnexpectedValueException(
                'Cannot handle token prior to ' . date(DateTime::ISO8601, $payload->nbf)
            );
        }

        if (isset($payload->iat) && $payload->iat > ($timestamp + static::$leeway)) {
            throw new \UnexpectedValueException(
                'Cannot handle token prior to ' . date(DateTime::ISO8601, $payload->iat)
            );
        }

        // 过期检查
        if (isset($payload->exp) && ($timestamp - static::$leeway) >= $payload->exp) {
            throw new \UnexpectedValueException('Expired token');
        }
        return $payload;
    }

    /**
     * Converts and signs a PHP object or array into a JWT string.
     *
     * @param object|array $payload PHP object or array
     * @param string $key The secret key.
     *                                  If the algorithm used is asymmetric, this is the private key
     * @param string $alg The signing algorithm.
     *                                  Supported algorithms are 'ES256', 'HS256', 'HS384', 'HS512', 'RS256', 'RS384', and 'RS512'
     * @param mixed $keyId
     * @param array $head An array with header elements to attach
     *
     * @return string A signed JWT
     *
     * @uses jsonEncode
     * @uses urlsafeB64Encode
     */
    public static function encode($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);
    }

    /**
     * Sign a string with a given key and algorithm.
     *
     * @param string $msg The message to sign
     * @param string|resource $key The secret key
     * @param string $alg The signing algorithm.
     *                                  Supported algorithms are 'ES256', 'HS256', 'HS384', 'HS512', 'RS256', 'RS384', and 'RS512'
     *
     * @return string An encrypted message
     *
     * @throws DomainException Unsupported algorithm was specified
     */
    public static function sign($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;
                }
        }
    }

    /**
     * Verify a signature with the message, key and method. Not all methods
     * are symmetric, so we must have a separate verify and sign method.
     *
     * @param string $msg The original message (header and body)
     * @param string $signature The original signature
     * @param string|resource $key For HS*, a string key works. for RS*, must be a resource of an openssl public key
     * @param string $alg The algorithm
     *
     * @return bool
     *
     * @throws DomainException Invalid Algorithm or OpenSSL failure
     */
    private static function verify($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);
                }
                $len = min(static::safeStrlen($signature), static::safeStrlen($hash));

                $status = 0;
                for ($i = 0; $i < $len; $i++) {
                    $status |= (ord($signature[$i]) ^ ord($hash[$i]));
                }
                $status |= (static::safeStrlen($signature) ^ static::safeStrlen($hash));

                return ($status === 0);
        }
    }

    /**
     * Decode a JSON string into a PHP object.
     *
     * @param string $input JSON string
     *
     * @return object Object representation of JSON string
     *
     * @throws DomainException Provided string was invalid JSON
     */
    public static function jsonDecode($input)
    {
        if (version_compare(PHP_VERSION, '5.4.0', '>=') && !(defined('JSON_C_VERSION') && PHP_INT_SIZE > 4)) {
            /** In PHP >=5.4.0, json_decode() accepts an options parameter, that allows you
             * to specify that large ints (like Steam Transaction IDs) should be treated as
             * strings, rather than the PHP default behaviour of converting them to floats.
             */
            $obj = json_decode($input, false, 512, JSON_BIGINT_AS_STRING);
        } else {
            /** Not all servers will support that, however, so for older versions we must
             * manually detect large ints in the JSON string and quote them (thus converting
             *them to strings) before decoding, hence the preg_replace() call.
             */
            $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;
    }

    /**
     * Encode a PHP object into a JSON string.
     *
     * @param object|array $input A PHP object or array
     *
     * @return string JSON representation of the PHP object or array
     *
     * @throws DomainException Provided object could not be encoded to valid JSON
     */
    public static function jsonEncode($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;
    }

    /**
     * Decode a string with URL-safe Base64.
     *
     * @param string $input A Base64 encoded string
     *
     * @return string A decoded string
     */
    public static function urlsafeB64Decode($input)
    {
        $remainder = strlen($input) % 4;
        if ($remainder) {
            $padlen = 4 - $remainder;
            $input .= str_repeat('=', $padlen);
        }
        return base64_decode(strtr($input, '-_', '+/'));
    }

    /**
     * Encode a string with URL-safe Base64.
     *
     * @param string $input The string you want encoded
     *
     * @return string The base64 encode of what you passed in
     */
    public static function urlsafeB64Encode($input)
    {
        return str_replace('=', '', strtr(base64_encode($input), '+/', '-_'));
    }

    /**
     * Helper method to create a JSON error.
     *
     * @param int $errno An error number from json_last_error()
     *
     * @return void
     */
    private static function handleJsonError($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
        );
        $msg = isset($messages[$errno]) ? $messages[$errno] : 'Unknown JSON error: ' . $errno;
        throw new DomainException($msg);
    }

    /**
     * Get the number of bytes in cryptographic strings.
     *
     * @param string $str
     *
     * @return int
     */
    private static function safeStrlen($str)
    {
        if (function_exists('mb_strlen')) {
            return mb_strlen($str, '8bit');
        }
        return strlen($str);
    }

    /**
     * Convert an ECDSA signature to an ASN.1 DER sequence
     *
     * @param string $sig The ECDSA signature to convert
     * @return  string The encoded DER object
     */
    private static function signatureToDER($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)
        );
    }

    /**
     * Encodes a value into a DER object.
     *
     * @param int $type DER tag
     * @param string $value the value to encode
     * @return  string  the encoded object
     */
    private static function encodeDER($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;
    }

    /**
     * Encodes signature from a DER object.
     *
     * @param string $der binary signature in DER format
     * @param int $keySize the nubmer of bits in the key
     * @return  string  the signature
     */
    private static function signatureFromDER($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;
    }

    /**
     * Reads binary DER-encoded data and decodes into a single object
     *
     * @param string $der the binary data in DER format
     * @param int $offset the offset of the data stream containing the object
     * to decode
     * @return array [$offset, $data] the new offset and the decoded object
     */
    private static function readDER($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, $len - 1);
            if (!$ignore_bit_strings) {
                $pos += $len - 1;
            }
        } elseif (!$constructed) {
            $data = substr($der, $pos, $len);
            $pos += $len;
        } else {
            $data = null;
        }

        return array($pos, $data);
    }

    //生成token
    public function get_token($uid, $user_name)
    {
        $key = static::key;
        $token = [
            "iss" => "admin_name",  //签发者 可以为空
            "aud" => "user_name", //面象的用户，可以为空
            "iat" => time(), //签发时间
            "nbf" => time(), //在什么时候jwt开始生效
            "exp" => time() + 30 * 60, //token 过期时间
            "uid" => $uid, //记录的userid的信息，这里是自已添加上去的，如果有其它信息，可以再添加数组的键值对
            "user_name" => $user_name,
        ];
        $jwt = $this->encode($token, $key, "HS256"); //根据参数生成了 token
        return $jwt;
    }

    //检查token
    public function check_token($token)
    {
        $key = static::key;
        $info = $this->decode($token, $key, ["HS256"]); //解密jwt
        return json($info);
    }

}

使用时可以直接复制这个文件，该为自己的命名空间，然后使用最后两个方法生成和验证token。