c# - OWIN OpenIdConnect Middleware IDX10311 nonce cannot be validated

Question

I have an application using the OWIN middleware for OpenIdConnect. The startup.cs file uses the standard implementation of app.UseOpenIdConnectAuthentication. The cookie is set to the browser, but it errors with:

IDX10311: RequireNonce is 'true' (default) but validationContext.Nonce is null. A nonce cannot be validated. If you don't need to check the nonce, set OpenIdConnectProtocolValidator.RequireNonce to 'false'.

I've found that when running fiddler as I do for most debug projects this behavior happens. The error is returned, but if I go back to the site everything is working and my user is authenticated. Has anyone seen this behavior when running fiddler?

With fiddler:

• SecurityTokenValidated notification in OpenIdConnect is executed twice.
• After the second pass through the IDX10311 error is thrown
• Browser contains the valid cookie, going back to the page I can view the valid User.Identity data.

Running without fiddler:

• SecurityTokenValidated executes once in OpenIdConnect
• No error thrown, proceeds to load up controller action for post authentication redirect Uri
• Cookie also valid and User.Identity data correct.

Ideas? I can get around it without running fiddler, but when debugging it would be nice to also run fiddler to inspect traffic.

Answer 1

Maybe is this the cause?

Hello there, I think I found the root cause of this issue.

I'm summing up my discoveries:

1. The problem is in the OpenIdConnect.nonce.OpenIdConnect cookie

2. This cookie is set from the app (let's call this "ID Client") as soon as the OpenID Middleware init an authentication session

3. The cookie should be sent back from the browser to the "ID Client" as soon as the authentication has been completed. My assumption is that this cookie is needed to have a double check from the ID client point of view (i.e. did I really started an OpenID Connect authorization flow?)

4. A lot of confusion in me was caused by the "Nonce" term, used both in this cookie and in the OpenID Connect flow from the ID server.

5. The exception, in my case, was caused by the missing cookie (not the nonce of the ID Server), simply because it wasn't sent by the browser back to the "ID client"

So the main root, in my case, was this: OpenIdConnect.nonce.OpenIdConnect cookie was not sent back to the ID Client by the browser. In some cases (i.e. Chrome, Firefox and Edge) cookie was sent correctly, while in others (IE11, Safari) it wasn't.

After a lot of research, I discovered that the problem was on the Cookie restriction policy, defined on the browser. In my case, the "ID client" is embedded in an <iframe>. This cause the "ID Client" to be seen as a "third-party client", because the user didn't navigate to that URL directly in the main window. Because this is a third-party, for some browsers, it's cookies have to be blocked. Indeed the same effect may be obtained on Chrome, by setting "Block third-party cookies".

So, I have to conclude that:

a) If iframe is a must (as in my case, because "ID Clients" are apps that must run inside the graphic content of the our main platform app), I think the only solution is to intercept the error, and handle it with a page, asking the user to enable third party cookies.

b) If iframe is not a must, it should suffice opening the "ID Client" in a new window.

Hope this helps somebody, because I got crazy!

Marco