OAuth Flow Security Checker
Validate OAuth 2.0 and OpenID Connect Authentication Flows
Ensure your OAuth/OIDC implementations are secure and compliant. Our checker analyzes your authentication flow configuration for common vulnerabilities, helping you identify and fix security risks like open redirects and token leakage before they become a problem.
OAuth Flow Security Checker
Validate your OAuth 2.0 and OpenID Connect flows against common security best practices.
This tool performs client-side checks for common OAuth 2.0 misconfigurations and is for educational purposes. It does not perform a live validation of your OAuth provider.
About This Tool
The OAuth Flow Security Checker is a dedicated tool for developers and security auditors working with modern authentication systems. OAuth 2.0 and OpenID Connect are powerful standards, but their flexibility can lead to complex and sometimes insecure implementations. A small misconfiguration—like a loose redirect URI or an incorrect response type—can open the door to serious vulnerabilities. This tool acts as a client-side linter for your OAuth flow. By inputting your configuration parameters, it runs a series of checks based on the latest industry best practices and IETF security recommendations. It instantly flags common pitfalls such as the use of the insecure Implicit flow, overly broad scopes, or redirect URIs that could be vulnerable to open redirect attacks. It's an educational and preventative utility designed to help you build more robust and secure authentication experiences, ensuring your users' data is protected.
How to Use This Tool
- Enter the full Redirect URI that your application has registered with the OAuth provider.
- Select the Response Type for your chosen OAuth flow (e.g., `code`).
- Enter the space-separated list of scopes your application is requesting (e.g., `openid profile email`).
- Click "Analyze Flow Security" to run the validation checks.
- Review the list of findings. The tool will provide passes for good practices and warnings or failures for potential vulnerabilities, along with suggestions for how to fix them.
In-Depth Guide
Understanding OAuth 2.0 Flows
OAuth 2.0 is an authorization framework, not an authentication protocol. It's about granting access, not proving identity. The most common and secure flow today is the **Authorization Code Flow with PKCE**. In this flow, the user is redirected to the auth server, logs in, and the server sends a temporary `code` back to the application's redirect URI. The application then exchanges this code for an access token on the backend. This prevents the token from ever being exposed in the browser history.
The Dangers of the Implicit Flow (`response_type=token`)
The Implicit Flow was an older method where the access token was returned directly in the URL fragment. This is now considered insecure and is deprecated. Because the token is in the URL, it can be leaked through browser history, referrer headers, or log files. This tool will always flag the use of `response_type=token` as a critical security failure. Always use the Authorization Code Flow (`response_type=code`).
What is an Open Redirect Vulnerability?
If a `redirect_uri` is not strictly validated, an attacker can trick a user into authorizing an application and then have the authorization code or token sent to a malicious site. For example, if you allow `https://myapp.com/redirect?to=*`, an attacker could craft a URL that sends the user to `evil.com`. Your authorization server must only accept redirects to a pre-registered, exact list of URIs.
The Importance of PKCE
PKCE (Proof Key for Code Exchange, pronounced "pixy") is an extension that adds another layer of security to the Authorization Code Flow. The client application creates a secret (`code_verifier`), transforms it (`code_challenge`), and sends the challenge to the auth server. When it exchanges the `code` for an access token, it must also send the original `code_verifier`. This proves that the client making the token request is the same one that initiated the flow, preventing authorization code interception attacks. It is now considered a mandatory part of modern OAuth for public clients like SPAs and mobile apps.