rbdwllr/reallysimplejwt

A really simple library to generate user authentication JSON Web Tokens.

3.1.0 2020-06-09 14:01 UTC

README

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A simple PHP library for creating JSON Web Tokens that uses HMAC SHA256 to sign signatures. For basic usage the library exposes a static interface to allow developers to create a token that stores a user identifier and expiration time.

The library is also open to extension, developers can define their own encoding standard, their own secret validation, set all the RFC standard JWT claims, and set their own private claims.

You can easily integrate ReallySimpleJWT with PSR-7 / PSR-15 compliant frameworks such as Slim PHP with the PSR-JWT middleware library. Please read the framework integration documentation to learn more.

If you need to read tokens in the browser please take a look at our JavaScript / Typescript library RS-JWT.

Contents

What is a JSON Web Token?

JSON Web Tokens is a standard for creating URL friendly access tokens that assert claims about a user or system.

A token is broken down into three parts; the header, the payload and the signature; with each part separated by a dot. Each part is encoded using the base64URL standard, see the RFC.

An example JWT:

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

The header and payload are both encoded JSON strings that contain a number of claims:

// Example Header
{
  "alg": "HS256",
  "typ": "JWT"
}

// Example Payload
{
  "sub": "1234567890",
  "name": "John Doe",
  "iat": 1516239022
}

A claim is a key value pair, eg "typ": "JWT", please read RFC 7519 to learn more about JSON Web Token claims.

Token security is achieved via the signature which is made up of the header, payload and a secret known only to the token author. This information is hashed and then base64URL encoded.

If a malicious user attempts to edit the header or payload claims they will be unable to replicate the signature so long as you use a strong secret. See Token Security for more information on this.

Setup

To install this package you will need to install Composer and then run composer init. Once this is done you can install the package via the command line or by editing the composer.json file created by the composer init command.

Finally you will need to reference the composer autoloader in your PHP code, require 'vendor/autoload.php';. The location of the autoload file will differ dependent on where your code is run. Also you will not need to reference the autoload file if you are using a framework like Laravel or Symfony.

Install via Composer on the command line:

composer require rbdwllr/reallysimplejwt

Install via the composer.json file:

Add the following to your composer.json file:

"require": {
    "rbdwllr/reallysimplejwt": "^2.0"
}

Then run:

composer update

Basic Usage

For basic usage the library exposes a set of static methods via the ReallySimpleJWT\Token class which allow a developer to create and validate basic JSON Web Tokens.

Create Token

Call the create() static method and pass in a user identifier, a secret, an expiration date time number and the token issuer.

This will return a token string on success and throw a ReallySimpleJWT\Exception\ValidateException on failure.

use ReallySimpleJWT\Token;

require 'vendor/autoload.php';

$userId = 12;
$secret = 'sec!ReT423*&';
$expiration = time() + 3600;
$issuer = 'localhost';

$token = Token::create($userId, $secret, $expiration, $issuer);

To create a more customised token developers can use the customPayload() method. This allows the creation of a token based on an array of key value pairs which represent the payload claims.

use ReallySimpleJWT\Token;

require 'vendor/autoload.php';

$payload = [
    'iat' => time(),
    'uid' => 1,
    'exp' => time() + 10,
    'iss' => 'localhost'
];

$secret = 'Hello&MikeFooBar123';

$token = Token::customPayload($payload, $secret);

On success the customPayload() method will return a JWT token string and on failure it will throw an exception.

Validate Token

To validate a JSON web token call the validate() static method, pass in the token string and the secret. The validate method checks the token structure is correct, the signature is valid, the expiration time has not expired and the not before time has elapsed.

It will return true on success and false on failure.

use ReallySimpleJWT\Token;

require 'vendor/autoload.php';

$token = 'aaa.bbb.ccc';
$secret = 'sec!ReT423*&';

$result = Token::validate($token, $secret);

Get Header and Payload Claims Data

To retrieve the token claims data from the header or payload call the getHeader() and or getPayload() static methods.

Both methods will return an associative array on success and throw an exception on failure.

use ReallySimpleJWT\Token;

require 'vendor/autoload.php';

$token = 'aaa.bbb.ccc';
$secret = 'sec!ReT423*&';

// Return the header claims
Token::getHeader($token, $secret);

// Return the payload claims
Token::getPayload($token, $secret);

Build and Parse Factory Methods

The ReallySimpleJWT\Token class also provides two factory methods to gain access to the core ReallySimpleJWT\Build and ReallySimpleJWT\Parse classes. These classes allow you to build custom tokens and parse and validate tokens as you see fit.

Token::builder(); // Returns an instance of ReallySimpleJWT\Build

Token::parser($token, $secret); // Returns an instance of ReallySimpleJWT\Parse

Advanced Usage

To create customised JSON Web Tokens developers need to access the ReallySimpleJWT\Build and ReallySimpleJWT\Parse classes directly.

Create Custom Token

The ReallySimpleJWT\Build class allows you to create a completely unique JSON Web Token. It has helper methods for all the RFC defined header and payload claims. For example, the setIssuer() method will add the iss claim to the token payload.

The class also allows developers to set custom header and payload claims via the setHeaderClaim() and setPayloadClaim() methods.

The methods can be chained together and when the build() method is called the token will be generated and returned within a ReallySimpleJWT\Jwt object.

use ReallySimpleJWT\Build;
use ReallySimpleJWT\Validate;
use ReallySimpleJWT\Encode;

require 'vendor/autoload.php';

$build = new Build('JWT', new Validate(), new Encode());

$token = $build->setContentType('JWT')
    ->setHeaderClaim('info', 'foo')
    ->setSecret('!secReT$123*')
    ->setIssuer('localhost')
    ->setSubject('admins')
    ->setAudience('https://google.com')
    ->setExpiration(time() + 30)
    ->setNotBefore(time() - 30)
    ->setIssuedAt(time())
    ->setJwtId('123ABC')
    ->setPayloadClaim('uid', 12)
    ->build();

Access the Token

A ReallySimpleJWT\Jwt object is returned when a developer calls the build() method on the ReallySimpleJWT\Build class. The Jwt class offers two methods getToken() and getSecret(). The former returns the generated JSON Web Token and the latter returns the secret used for the token signature.

To parse a JSON Web Token via the ReallySimpleJWT\Parse class a developer must first create a new ReallySimpleJWT\Jwt object by injecting the token and secret.

use ReallySimpleJWT\Jwt;

require 'vendor/autoload.php';

$token = 'aaa.bbb.ccc';
$secret = '!secReT$123*';

$jwt = new Jwt($token, $secret);

// Return the token
$jwt->getToken();

// Return the secret
$jwt->getSecret();

Parse and Validate Token

The ReallySimpleJWT\Parse class allows a developer to parse and validate a JSON Web Token. Four validation methods are available which can all be chained:

  • validate() confirms the structure of the token and the validity of the signature.
  • validateExpiration() confirms the token expiration claim (exp) has not expired.
  • validateNotBefore() confirms the token not before claim (nbf) has elapsed.
  • validateAudience() confirms the token audience claim (aud) matches what is expected.
  • validateAlgorithm() confirms the token algorithm claim (alg) matches what is expected and is valid (See: RFC 7518).

Each validation method will throw a ReallySimpleJWT\Exception\ValidateException if there is anything wrong with the supplied token.

The parse() method which should be called after validation is complete will decode the JSON Web Token. It will then return the result as a ReallySimpleJWT\Parsed object. This will provide access to the claims data the token holds in the header and the payload.

use ReallySimpleJWT\Parse;
use ReallySimpleJWT\Jwt;
use ReallySimpleJWT\Validate;
use ReallySimpleJWT\Encode;

require 'vendor/autoload.php';

$token = 'aaa.bbb.ccc';
$secret = '!secReT$123*';

$jwt = new Jwt($token, $secret);

$parse = new Parse($jwt, new Validate(), new Encode());

$parsed = $parse->validate()
    ->validateExpiration()
    ->validateNotBefore()
    ->validateAudience('https://example.com')
    ->validateAudience('https://test.com')
    ->parse();

// Return the token header claims as an associative array.
$parsed->getHeader();

// Return the token payload claims as an associative array.
$parsed->getPayload();

Access Token Claims Data

The ReallySimpleJWT\Parsed class is returned when a developer calls the parse() method on the ReallySimpleJWT\Parse class.

It provides a number of helper methods to gain access to the token claim data. A developer can call the getHeader() and getPayload() methods to gain access to the respective claim data as associative arrays.

Alternatively a developer can call one of the RFC compliant claim methods:

Header

  • getAlgorithm()
  • getType()
  • getContentType()

Payload

  • getIssuer()
  • getSubject()
  • getAudience()
  • getExpiration()
  • getNotBefore()
  • getIssuedAt()
  • getJwtId()
  • getExpiresIn()
  • getUsableIn()

Custom Encoding

By default this library hashes and encodes the JWT signature via hash_hmac() using the sha256 algorithm. If a developer would like to use a customised form of encoding they just need to generate a custom encode class which complies with the ReallySimpleJWT\Interfaces\Encoder interface.

interface EncodeInterface
{
    public function getAlgorithm(): string;

    public function encode(string $toEncode): string;

    public function decode(string $toDecode): string;

    public function signature(string $header, string $payload, string $secret): string;
}

Error Messages and Codes

The ReallySimpleJWT library will in a number of situations throw exceptions to highlight problems when creating and parsing JWT tokens. The error codes, messages and their explanations are below.

Code Message Explanation
1 Token is invalid. Token must have three parts separated by dots.
2 Audience claim does not contain provided StringOrURI. The aud claim must contain the provided string or URI string provided.
3 Signature is invalid. Signature does not match header / payload content. Could not replicate signature with provided header, payload and secret.
4 Expiration claim has expired. The exp claim must be a valid date time number in the future.
5 Not Before claim has not elapsed. The nbf claim must be a valid date time number in the past.
6 Expiration claim is not set. Attempt was made to validate an Expiration claim which does not exist.
7 Not Before claim is not set. Attempt was made to validate a Not Before claim which does not exist.
8 Invalid payload claim. Payload claims must be key value pairs of the format string: mixed.
9 Invalid secret. Must be 12 characters in length, contain upper and lower case letters, a number, and a special character `*&!@%^#$``
10 Invalid Audience claim. The aud claim can either be a string or an array of strings nothing else.
11 Audience claim is not set. Attempt was made to validate an Audience claim which does not exist.
12 Algorithm claim is not valid. Algorithm should be a valid Digital Signature or MAC Algorithm, or none. See RFC 7518.
13 Algorithm claim is not set. Attempt was made to validate an Algorithm claim which does not exist.

Token Security

The JWT RFC 7519 allows for the creation of tokens without signatures and without secured / hashed signatures. The ReallySimpleJWT library however imposes security by default as there is no logical reason not to. All created tokens must have a signature and a strong secret, but the library will validate tokens without a secret or a strong secret. The library will not validate tokens without a signature.

It is possible to edit and enhance the implementation of the signature and its security level by creating a custom encode class that implements the ReallySimpleJWT\Interfaces\Encode interface, or a custom secret class which implements the ReallySimpleJWT\Interfaces\Secret interface. See sections Custom Encoding and Custom Secrets

Signature Secret

This JWT library imposes strict secret security as follows: the secret must be at least 12 characters in length; contain numbers; upper and lowercase letters; and one of the following special characters *&!@%^#$.

// Bad Secret
secret123

// Good Secret
sec!ReT423*&

The reason for this is that there are lots of JWT Crackers available meaning weak secrets are easy to crack thus rendering the security JWT offers useless.

Custom Secrets

While we advise strongly against using weak secrets for JWT signatures we do accept there are systems on the 'internets' which for one reason or another impose weak secrets on developers.

You can setup custom secret validation by creating your own secret class which implements the ReallySimpleJWT\Interfaces\Secret interface. You can then pass this custom secret class to the ReallySimpleJWT\Build class.

<?php

declare(strict_types=1);

namespace ReallySimpleJWT;

use ReallySimpleJWT\Interfaces\Secret;

class CustomSecret implements Secret
{
    public function validate(string $secret): bool
    {
        // Please do not copy this code, it is an example of weak secret validation.
        return (bool) preg_match('/[a-z]+/', $secret);
    }
}

// Create JWT Builder with Custom Secret Class.
$build = new Build(
    'JWT', 
    new Validate(), 
    new CustomSecret(), 
    new Encode()
);

Framework Integration With PSR-JWT Middleware

You can easily integrate ReallySimpleJWT with PSR-7 / PSR-15 compliant frameworks such as Slim PHP and Zend Expressive by using the PSR-JWT library.

For example integration with Slim PHP only requires a few lines of code:

// Can be added to any routes file in Slim, often index.php.
require '../../vendor/autoload.php';

$app->get('/jwt', function (Request $request, Response $response) {
    $response->getBody()->write("JSON Web Token is Valid!");

    return $response;
})->add(\PsrJwt\Factory\JwtAuth::middleware('Secret123!456$', 'jwt', 'Authentication Failed'));

Please read the PSR-JWT documentation to learn more about integration options for ReallySimpleJWT.

Browser Integration With RS-JWT

When you create JSON Web Tokens you may wish to read some of the information contained in the header and payload claims in the browser.

If you do, we have an NPM packages for that called RS-JWT.

Install:

npm install --save rs-jwt

Usage:

import { parseJwt } from 'rs-jwt'

const result = parseJwt('json.web.token')

// Return the header claims as an object.
const header = result.getHeader()

// Access the type claim.
console.log(header.typ)

// Return the payload claims as an object.
const payload = result.getPayload()

// Access the expiry claim.
console.log(payload.exp)

For more information see the project README or visit the NPM Page.

License

MIT

Author

Rob Waller

Twitter: @robdwaller