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JWT – (JSON Web Token) for PHP

A Php implementation of JSON Web Token.

Installing

Install with composer

Algorithms and Usage

The JWT spec supports NONE, HMAC, RSASSA, ECDSA and RSASSA-PSS algorithms for cryptographic signing.

Supported algorithms:

• None
• HMAC 256
• RSA 256

NONE - unsigned token

<?php

use Jwt\Jwt;
use Jwt\Algorithm\NoneAlgorithm;

$token = Jwt::encode('string', new NoneAlgorithm());

echo $token; // eyJ0eXAiOiJKV1QiLCJhbGciOiJub25lIn0.eyJkYXRhIjoic3RyaW5nIn0.

HMAC

• HS256 - HMAC using SHA-256 hash algorithm

HS256

<?php

use Jwt\Jwt;
use Jwt\Algorithm\HS256Algorithm;

$token = Jwt::encode('string', $alg = new HS256Algorithm('secret'));

echo $token; // eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJkYXRhIjoic3RyaW5nIn0.RncJbCyf4zd0pu1N02u_rKwEezkmd94r3i5sWLk1ceU

// decode, you must passed allowed algorithm(s) to prevent attackers to control the choice of algorithm
$decoded = Jwt::decode($token, ['algorithm' => $alg]);

echo $decoded['data']; // 'string'

RSA

• RS256 - RSA using SHA-256 hash algorithm

RS256 - RSA using SHA-256 hash algorithm

<?php

use Jwt\Jwt;
use Jwt\Algorithm\RS256Algorithm;

$privateKey = __DIR__ . '/key.pem';
$publicKey = __DIR__ . '/key.pub';

$token = Jwt::encode('string', $alg = new RS256Algorithm($privateKey, $publicKey));

echo $token; // eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJkYXRhIjoic3RyaW5nIn0.RncJbCyf4zd0pu1N02u_rKwEezkmd94r3i5sWLk1ceU

// decode, you must passed allowed algorithm(s) to prevent attackers to control the choice of algorithm
$decoded = Jwt::decode($token, ['algorithm' => $alg]);

echo $decoded['data']; // 'string'

Support for reserved claim names

JSON Web Token defines some reserved claim names and defines how they should be used. JWT supports these reserved claim names:

• 'exp' (Expiration Time) Claim
• 'nbf' (Not Before Time) Claim
• 'iss' (Issuer) Claim
• 'aud' (Audience) Claim
• 'jti' (JWT ID) Claim
• 'iat' (Issued At) Claim
• 'sub' (Subject) Claim

Expiration Time Claim

The exp (expiration time) claim identifies the expiration time on or after which the JWT MUST NOT be accepted for processing. The processing of the exp claim requires that the current date/time MUST be before the expiration date/time listed in the exp claim. Implementers MAY provide for some small leeway, usually no more than a few minutes, to account for clock skew. Its value MUST be a number containing a NumericDate value. Use of this claim is OPTIONAL.

Handle Expiration Claim

<?php

use Jwt\Jwt;
use Jwt\Algorithm\HS256Algorithm;
use Jwt\Exception\ExpiredException;

$payload = [
    Jwt::CLAIM_EXPIRATION => strtotime('1 day'),
    'data' => 'my data'
];

$token = Jwt::encode($payload, $alg = new HS256Algorithm('secret'));

try {
    $token = Jwt::decode($token, ['algorithm' => $alg]);
} catch (ExpiredException $e) {
    // Handle expired token, e.g. logout user or deny access
}

Adding Leeway

<?php

use Jwt\Jwt;
use Jwt\Algorithm\HS256Algorithm;
use Jwt\Exception\ExpiredException;

$leeway = 30; // 30 sec

$payload = [
    Jwt::CLAIM_EXPIRATION => strtotime('1 day'),
    'data' => 'my data'
];

$token = Jwt::encode($payload, $alg = new HS256Algorithm('secret'));

try {
    $token = Jwt::decode($token, ['algorithm' => $alg, 'leeway' => $leeway]);
} catch (ExpiredException $e) {
    // Handle expired token, e.g. logout user or deny access
}

Not Before Time Claim

The nbf (not before) claim identifies the time before which the JWT MUST NOT be accepted for processing. The processing of the nbf claim requires that the current date/time MUST be after or equal to the not-before date/time listed in the nbf claim. Implementers MAY provide for some small leeway, usually no more than a few minutes, to account for clock skew. Its value MUST be a number containing a NumericDate value. Use of this claim is OPTIONAL.

Handle Not Before Claim

<?php

use Jwt\Jwt;
use Jwt\Algorithm\HS256Algorithm;
use Jwt\Exception\BeforeValidException;

$payload = [
    Jwt::CLAIM_NOT_BEFORE => strtotime('1 day'),
    'data' => 'my data'
];

$token = Jwt::encode($payload, $alg = new HS256Algorithm('secret'));

try {
    $token = Jwt::decode($token, ['algorithm' => $alg]);
} catch (BeforeValidException $e) {
    // Handle invalid token, e.g. logout user or deny access
}

Issuer Claim

The iss (issuer) claim identifies the principal that issued the JWT. The processing of this claim is generally application specific. The iss value is a case-sensitive string containing a StringOrURI value. Use of this claim is OPTIONAL.

Handle Issuer Claim

See the payload verification section.

Audience Claim

The aud (audience) claim identifies the recipients that the JWT is intended for. Each principal intended to process the JWT MUST identify itself with a value in the audience claim. If the principal processing the claim does not identify itself with a value in the aud claim when this claim is present, then the JWT MUST be rejected. In the general case, the aud value is an array of case-sensitive strings, each containing a StringOrURI value. In the special case when the JWT has one audience, the aud value MAY be a single case-sensitive string containing a StringOrURI value. The interpretation of audience values is generally application specific. Use of this claim is OPTIONAL.

Handle Audience Claim

See the payload verification section.

JWT ID Claim

The jti (JWT ID) claim provides a unique identifier for the JWT. The identifier value MUST be assigned in a manner that ensures that there is a negligible probability that the same value will be accidentally assigned to a different data object; if the application uses multiple issuers, collisions MUST be prevented among values produced by different issuers as well. The jti claim can be used to prevent the JWT from being replayed. The jti value is a case-sensitive string. Use of this claim is OPTIONAL.

Handle JWT ID claim

See the payload verification section.

Issued At Claim

The iat (issued at) claim identifies the time at which the JWT was issued. This claim can be used to determine the age of the JWT. Its value MUST be a number containing a NumericDate value. Use of this claim is OPTIONAL.

Handle Issued At Claim

See the payload verification section.

Subject Claim

The sub (subject) claim identifies the principal that is the subject of the JWT. The Claims in a JWT are normally statements about the subject. The subject value MUST either be scoped to be locally unique in the context of the issuer or be globally unique. The processing of this claim is generally application specific. The sub value is a case-sensitive string containing a StringOrURI value. Use of this claim is OPTIONAL.

Handle Subject Claim

See the payload verification section.

Payload verification

Payload data can be verified when decoding the token using the verify option. Expiration and Not Before claims are ALWAYS checked.

<?php

use Jwt\Jwt;
use Jwt\Algorithm\HS256Algorithm;
use Jwt\Exception\VerificationException;

$payload = [
    // expiration claim
    Jwt::CLAIM_EXPIRATION => strtotime('1 day'),
    // issuer claim
    Jwt::CLAIM_ISSUER => 'my-web-app',
    // custom claims
    'user' => 'administrator'
];

$token = Jwt::encode($payload, $alg = new HS256Algorithm('secret'));

// Decode with verification of the payload
// Expiration, and Not before claims are verified automatically

// we will verify the token when decoding
$verify = [
    Jwt::CLAIM_ISSUER => 'my-web-app',
    // we can use closures for value verification
    'user' => function ($value) {
        if ($value === 'administrator') {
            return true;
        }
        return false;
    }
];

try {
    $decoded = Jwt::decode($token, ['algorithm' => $alg, 'verify' => $verify]);
} catch (VerificationException $e) {
    // something is wrong with the token
    // do something!
    switch ($e->getCode()) {
        case VerificationException::CLAIM_IS_MISSING:
            // claim is missing
            break;
        case VerificationException::CLAIM_VALUE_IS_INVALID:
            // invalid claim value
            break;
    }
}

Tests

Run the tests using phpunit:

$ phpunit

Credits

Jwt was inspired by jwt for ruby and firebase/jwt for php.