OpenID Connect: Skip IdP Redirect If EndSessionEndpoint Is Missing

Hey everyone! Let's dive into a discussion about enhancing OpenID Connect (OIDC) in ASP.NET Core. Specifically, we're talking about how to handle scenarios where the Identity Provider (IdP) doesn't provide an EndSessionEndpoint. This can lead to some hiccups during sign-out, and we're here to explore a smoother way to manage it.

The Issue: Missing EndSessionEndpoint

So, here's the deal: when you're setting up your application to use OpenID Connect, you might encounter situations where your users are authenticating against various IdPs. These IdPs might not always support the same features. One crucial feature is the EndSessionEndpoint, which is used to initiate a sign-out at the IdP level. Now, if this endpoint is missing, calling SignOut can throw an exception, which isn't the best user experience, right?

Why This Matters

Think about it – you're building a robust application, and you want it to handle different scenarios gracefully. You don't want a missing configuration to bring down the whole sign-out process. Imagine a user trying to log out, and instead of a smooth transition, they're greeted with an error message. Not ideal, right? This is where we need a solution that's both flexible and user-friendly. We want to ensure that even if the EndSessionEndpoint is absent, the application doesn't crash and burn. Instead, we want it to intelligently skip the IdP redirect and proceed with the sign-out callback, ensuring a seamless experience for the user.

The Current Workaround

Currently, many developers are manually checking for the EndSessionEndpoint before calling SignOut. If it's missing, they clear the cookie themselves. While this works, it's not the most elegant solution. It adds extra code and complexity, and it's something that the OIDC middleware could potentially handle for us. It's like having to manually check the weather forecast every morning before deciding what to wear, when your smart home could just do it for you. We're aiming for that smart home level of convenience and efficiency here.

The Proposal: A Graceful Skip

So, what's the solution we're cooking up? The idea is to add an option to OpenIdConnectOptions that allows us to silently skip the redirect to the IdP when the EndSessionEndpoint is not set. This means that instead of throwing an exception, the application would simply redirect to the sign-out callback. It's like having a safety net that catches you when things don't go exactly as planned.

How It Would Work

Imagine a simple toggle in your OIDC setup that says, "If the EndSessionEndpoint is missing, no worries, just skip it and carry on." This is the essence of the proposal. By setting a property, like IgnoreMissingEndSessionEndpoint, to true, you're telling the middleware to handle this scenario gracefully. This approach not only simplifies the code but also makes the application more resilient to variations in IdP configurations. It’s about making the system smarter and more adaptable to real-world conditions.

Benefits of This Approach

• Improved User Experience: No more unexpected errors during sign-out.
• Simplified Code: Less manual checking and handling of edge cases.
• Greater Flexibility: Easily handle IdPs with varying levels of OIDC support.
• Increased Resilience: The application is more robust against missing configurations.

Diving Deeper: Motivation and Goals

Let's get into the nitty-gritty. Our main motivation here is to provide a smoother experience for users in scenarios where they're using their own OIDC-compliant IdPs. Often, these setups mean we don't have prior knowledge of all the features supported by the IdP. We've hit a snag where calling SignOut throws an exception if EndSessionEndpoint is missing. Currently, we're doing manual checks, which isn't ideal.

The Core Goal

The core goal is simple: we want to introduce a setting that, when toggled, will skip the IdP redirect and go straight to the sign-out callback if the EndSessionEndpoint is missing. It's about making the system more adaptable and less prone to errors when faced with incomplete configurations. We aim to create a more resilient and user-friendly authentication process.

Why This Matters for Developers

For developers, this means less boilerplate code and fewer headaches. Instead of writing custom checks and workarounds, you can simply set an option and let the middleware handle the rest. It's about abstracting away the complexities and allowing you to focus on building the core features of your application. This change is a step towards making the authentication process more streamlined and less error-prone.

Scope: What We're Focusing On

For clarity, let's define what we're focusing on and what we're not. This proposal is specifically about handling the case where the EndSessionEndpoint is missing in the discovery document. We're not trying to solve all the problems related to OIDC sign-out, just this particular one.

In Scope: Empty EndSessionEndpoint

If the discovery document comes back and the EndSessionEndpoint is empty, that's what we're addressing. This is the specific scenario where we want to provide a more graceful fallback. It’s about ensuring that our application can handle this common situation without throwing an error.

Out of Scope: Other Sign-Out Issues

We're not tackling other issues like missing ID tokens or other exceptions during sign-out. Those are important, but they're separate concerns. Similarly, this proposal isn’t about general error handling during logout or dealing with misconfigured IdPs beyond the missing EndSessionEndpoint. We're laser-focused on this one specific issue to keep the scope manageable and the solution targeted.

Risks and Unknowns: What Could Go Wrong?

With any proposal, it's crucial to consider the potential risks and unknowns. How might developers misinterpret or misuse this feature? Could it restrict us from future enhancements? What about performance, security, and correctness concerns?

Potential Misuse

One concern is how developers might interpret the new option. It's essential to name it clearly (more on that later) to avoid confusion. We need to ensure that developers understand this setting is specifically for cases where the EndSessionEndpoint is genuinely missing, not as a general way to skip IdP sign-out. Clear documentation and examples will be key here.

Future Restrictions

We also need to think about whether this change might limit future enhancements. Could it make it harder to add more sophisticated sign-out options down the road? We don't believe so, but it's a question worth asking. The goal is to design a solution that's both effective now and flexible enough to accommodate future needs.

Perf, Security, and Correctness

From a performance perspective, this change should be minimal. It's essentially a conditional check and a skip, which shouldn't add significant overhead. Security-wise, there aren't apparent concerns, as we're merely altering the flow when an endpoint is missing. Correctness is paramount, and we'll need thorough testing to ensure the new option behaves as expected in various scenarios. We need to make sure that skipping the redirect doesn't inadvertently bypass critical sign-out steps.

Examples: How Developers Would Use It

Let's look at some examples of how developers might use this new feature. This will help illustrate the simplicity and elegance of the proposed solution.

Code Snippet

Here's a quick example of how the code might look:

services.AddOpenIdConnect(options => {
    options.IgnoreMissingEndSessionEndpoint = true; // Default false, need better name
});

In this snippet, we're adding the IgnoreMissingEndSessionEndpoint option to the OpenIdConnectOptions. Setting it to true tells the middleware to skip the IdP redirect if the EndSessionEndpoint is missing. Notice the comment about needing a better name – that's a crucial point we'll discuss later.

Real-World Scenario

Imagine a developer building an application that integrates with multiple IdPs. Some IdPs might support the EndSessionEndpoint, while others might not. With this new option, the developer can configure the application to handle both scenarios gracefully. They don't need to write custom logic to check for the endpoint; the middleware takes care of it.

This is about making the developer's life easier and the application more robust. By providing a simple, declarative way to handle missing EndSessionEndpoint configurations, we're reducing the chances of errors and improving the overall development experience.

Extra Thoughts: Naming and Next Steps

Before we wrap up, let's touch on a couple of extra points. First, the naming of the option – IgnoreMissingEndSessionEndpoint – is a placeholder. We need a better name that clearly conveys the purpose of the option without being too verbose. Something like SkipIdpSignOutIfMissingEndpoint might be more descriptive.

The Big Question: Is This the Right Approach?

This is where your feedback comes in! Do you think this is the right way to handle missing EndSessionEndpoint configurations? Are there alternative approaches we should consider? Your insights are invaluable in shaping the final solution.

What's Next?

The next step is to gather feedback and refine the proposal based on your input. If there's consensus that this is a valuable addition, we can move forward with implementing it. I'm happy to open a PR for this if the change is welcomed. 😄

In the same vein, if there's already a way to achieve this behavior, please let me know! That would also close this discussion. Thanks for reading, and let's make OIDC in ASP.NET Core even better!