PHP OAuth 2.0 - Implementing Authorization Flows

OAuth 2.0 is a widely used protocol for securing APIs and allowing third-party applications to access user data. It provides various authorization flows for different scenarios. In this guide, we'll explore how to implement OAuth 2.0 in PHP:

Step 1: Choose an OAuth 2.0 Library

There are several PHP libraries available for OAuth 2.0. One of the popular choices is "League OAuth2 Server." Install it using Composer:

        composer require league/oauth2-server
    

Step 2: Configure OAuth 2.0 Server

Configure your OAuth 2.0 server by defining clients, scopes, and storage for tokens and authorization codes. Below is a basic configuration example:

        // Your server configuration
        $server = new League\OAuth2\Server\AuthorizationServer(
            $clientRepository,
            $accessTokenRepository,
            $scopeRepository,
            $privateKey,
            $encryptionKey
        );
    

Step 3: Create Endpoints for Authorization Flows

Create endpoints for the different OAuth 2.0 authorization flows, such as authorization code, implicit, client credentials, etc. Here's an example of an authorization code flow endpoint:

        $server->enableGrantType(
            new League\OAuth2\Server\Grant\AuthCodeGrant(
                $authCodeRepository,
                $refreshTokenRepository,
                new DateInterval('PT10M')
            )
        );
    

Step 4: Implement OAuth 2.0 in Your PHP Application

In your PHP application, handle OAuth 2.0 requests and responses. For example, when a client requests authorization, redirect the user to the authorization server:

        if (!$request->isAuthorized()) {
            // Redirect user to the authorization server
            $response->headers->set('Location', '/authorize?'.http_build_query($request->getAuthorizationRequest()));
            $response->setStatusCode(302);
            return $response;
        }
    

After successful authorization, handle token requests and secure your API endpoints with token validation.

Step 5: Protect Your API

Protect your API by validating access tokens before granting access to resources. Here's a basic example of token validation:

        $resourceServer = new League\OAuth2\Server\ResourceServer(
            $accessTokenRepository,
            $publicKey
        );
        
        try {
            $resourceServer->isValidRequest();
            $token = $resourceServer->getAccessToken();
        } catch (OAuthServerException $e) {
            $response = $e->generateHttpResponse(new \GuzzleHttp\Psr7\Response());
            return $response;
        }
    

Implementing OAuth 2.0 can be complex, and this is just a high-level overview. Make sure to follow the OAuth 2.0 specification and use an established library to ensure security and compliance with the protocol.