README

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, set all the RFC standard JWT claims and set their own private claims.

What is a JSON Web Token?
Setup
Basic Usage
Advanced Usage
Error Messages and Codes
Token Security
- Signature Secret

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:

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

// 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 key. See Token Security for more information on this.

Setup

Via Composer on the command line:

composer require placetopay/reallysimplejwt

Via composer.json:

"require": {
    "placetopay/reallysimplejwt": "^2.1"
}

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;

$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;

$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;

$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;

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

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

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

Factory Methods

The ReallySimpleJWT\Token class also provides two factory methods to gain access to the core ReallySimpleJWT\Build and ReallySimpleJWT\Parse classes.

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;

$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;

$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. Three 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.

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;

$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()
    ->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()

Customised 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\EncodeInterface.

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	Token could not be parsed.	Something weird happened ;) undefined problem with the token.
3	Signature is invalid.	Signature does not match header / payload content. Could not replicate signature with provided header and payload.
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 `*&!@%^#$`` by default or user defined.
10	Invalid Audience claim.	The aud claim can either be a string or an array of strings nothing else.

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\EncodeInterface. See section Customised Encoding

Signature Secret

This JWT library does not imposes strict secret string security. However a good practice could be to set a strict pattern to validate the secret.

# setting a secret string pattern for validation
\ReallySimpleJWT\Validate::$secretPattern = '/^.*$/';

// Same validation without special characters
\ReallySimpleJWT\Validate::$secretPattern = /^.*(?=.{12,}+)(?=.*[0-9]+)(?=.*[A-Z]+)(?=.*[a-z]+).*$/;

// 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.

License

MIT

Author

Rob Waller

Twitter: @robdwaller

placetopay / reallysimplejwt

Maintainers

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