OpenID Tools Library

WARNING: this library is under heavy development and should not be used in production!

This library provides some common tools that you might find useful when working with OpenID family of specifications.

Installation

Library can be installed by using Composer:

composer require simplesamlphp/openid

OpenID Federation

The initial functionality of the library revolves around the OpenID Federation specification. To use it, create an instance of the class \SimpleSAML\OpenID\Federation

<?php

declare(strict_types=1);

namespace Your\Super\App;

use SimpleSAML\OpenID\Algorithms\SignatureAlgorithmBag;
use SimpleSAML\OpenID\Algorithms\SignatureAlgorithmEnum;
use SimpleSAML\OpenID\SupportedAlgorithms;
use Psr\SimpleCache\CacheInterface;
use Psr\Log\LoggerInterface;
use SimpleSAML\OpenID\Federation;
use Symfony\Component\HttpFoundation\Response;

class Test
{
    public function __construct(
        protected CacheInterface $cache,
        protected LoggerInterface $logger,
    ) {
    }
    
    public function __invoke(): Response
    {
        // Instantiation example by using default options.
        // * 'RS256' as supported algorithm
        // * no caching support (not recommended for production environment)
        // * no logging support
        $federationTools = new Federation();
        
        // Instantiation example by injecting some of the dependencies 
        // Define the supported signature algorithms:
        $supportedAlgorithms = new SupportedAlgorithms(
            new SignatureAlgorithmBag(
                SignatureAlgorithmEnum::RS256,
                // ... if needed, add other supported signature algorithms here
            )
        );
        
        // Define the maximum cache TTL for federation artifacts. This will be used together with 'exp'
        // claim to resolve the maximum cache time for trust chains, entity statements, etc.
        $maxCacheDuration = new DateInterval('PT6H');
        
        // Instantiate by injecting own options / dependencies:
        $federationTools = new Federation(
            supportedAlgorithms: $supportedAlgorithms,
            maxCacheDuration: $maxCacheDuration,
            cache: $this->cache, // \Psr\SimpleCache\CacheInterface
            logger: $this->logger, // \Psr\Log\LoggerInterface
        );
        
        // Continue with using available tools ...
        
        return new Response();
    }
}

Trust chain resolver

Once you have a \SimpleSAML\OpenID\Federation instantiated, you can continue with using available tools. The first tool we will take a look at is trust chain resolver. This tool can be used to try and resolve the (shortest) trust chain for given leaf entity (subject) and trusted anchors:

// ... 

try {
    /** @var \SimpleSAML\OpenID\Federation $federationTools */
    /** @var \SimpleSAML\OpenID\Federation\TrustChainBag $trustChainBag */
    $trustChainBag = $federationTools->trustChainResolver()->for(
        'https://leaf-entity-id.example.org/', // Trust chain subject (leaf entity).
        [ 
            // List of valid trust anchors.
            'https://trust-achor-id.example.org/',
            'https://other-trust-achor-id.example.org/',
        ],
    );
} catch (\Throwable $exception) {
    $this->loggerService->error('Could not resolve trust chain: ' . $exception->getMessage())
    return;
}

If the trust chain is successfully resolved, this will return an instance of \SimpleSAML\OpenID\Federation\TrustChainBag. Otherwise, exception will be thrown. From the TrustChainBag you can get the TrustChain using several methods.

// ... 

try {
    /** @var \SimpleSAML\OpenID\Federation\TrustChain $trustChain */
    /** @var \SimpleSAML\OpenID\Federation\TrustChainBag $trustChainBag */
    // Simply get the shortest available chain.
    $trustChain = $trustChainBag->getShortest();
    // Get the shortest chain, but take into account the Trust Anchor priority.
    $trustChain = $trustChainBag->getShortestByTrustAnchorPriority(
        'https://other-trust-achor-id.example.org/', // Get chain for this Trust Anchor even if the chain is longer.
        'https://trust-achor-id.example.org/',
    );
} catch (\Throwable $exception) {
    $this->loggerService->error('Could not resolve trust chain: ' . $exception->getMessage())
    return;
}

Once you have the Trust Chain, you can try and get the resolved metadata for particular entity type. Resolved metadata means that all metadata policies from all intermediates have been successfully applied. Here is one example for trying to get metadata for OpenID RP, which will return an array (or null if no metadata is available for given entity type):

// ... 

$entityType = \SimpleSAML\OpenID\Codebooks\EntityTypesEnum::OpenIdRelyingParty;

try {
    /** @var \SimpleSAML\OpenID\Federation\TrustChain $trustChain */
    $metadata = $trustChain->getResolvedMetadata($entityType);
} catch (\Throwable $exception) {
    $this->loggerService->error(
        sprintf(
            'Error resolving metadata for entity type %s. Error: %s.',
            $entityType->value,
            $exception->getMessage(),        
        ),   
    );
    return;
}

if (is_null($metadata)) {
    $this->loggerService->error(
        sprintf(
            'No metadata available for entity type %s.',
            $entityType->value,      
        ),
    );
    return;
}

If getting metadata results in an exception, the metadata is considered invalid and is to be discarded.

Additional verification of signatures

The whole trust chain (each entity statement) has been verified using public keys from JWKS claims in configuration / subordinate statements. As per specification recommendation, you can also validate the signature of the Trust Chain Configuration Statement by using the Trust Anchor public keys (JWKS) that you have acquired in some secure out-of-band way (so to not only rely on TLS protection while fetching Trust Anchor Configuration Statement):

// ... 

// Get entity statement for the resolved Trust Anchor:
/** @var \SimpleSAML\OpenID\Federation\TrustChain $trustChain */
$trustAnchorConfigurationStatement = $trustChain->getResolvedTrustAnchor();
// Get data that you need to prepare appropriate public keys, for example, the entity ID:
$trustAnchorEntityId = $trustAnchorConfigurationStatement->getIssuer();

// Prepare JWKS array containing Trust Anchor public keys that you have acquired in secure out-of-band way ...
/** @var array $trustAnchorJwks */

try {    
    $trustAnchorConfigurationStatement->verifyWithKeySet($trustAnchorJwks);
} catch (\Throwable $exception) {
    $this->loggerService->error('Could not verify trust anchor configuration statement signature: ' .
    $exception->getMessage());
    return;
}