Unable to validate issuer when trying to access API

Question

so here's a quick explanation of my issue - my current setup is and IdentityServer4 implementation with ASP.NET Core Identity, an API resource protected by it and a Xamarin.Android application that is the client. My current issue is that the client(Android) cannot get anything from the API because of the following error(from the API logs):

"Bearer" was not authenticated. Failure message: "IDX10205: Issuer validation failed. Issuer: 'http://10.0.2.2:5000'. Did not match: validationParameters.ValidIssuer: 'null' or validationParameters.ValidIssuers: 'http://127.0.0.1:5000'."

Basically, since I'm using the Android emulator, in order to call something that's on localhost on my machine, I need to use the 10.0.2.2 URL for it. Then the problem pops up - the Identity Server is fine with authenticating, I can login fine, I get an access token, but after that I need to call the API. And that's where the error happens - it's expecting an issuer that is with the same authority(127.0.0.1:5000) but receives the 10.0.2.2:5000, which is the authority for the Android client.

So, my question is - is there a way to somehow specify that 10.0.2.2 is also a valid issuer, or do I have to start thinking about deploying both the API and the Identity Server just so I can test the client. I'd really like it if there was a way to have the whole solution running on my local machine rather than having to deploy for every little thing I want to try out.

Any help will be appreciated very much.

user_4631952 · Answer

So, I managed to work around the issue by simply running the Web part of it so it's visible on my local network. What I did in more detail - in the Program.cs where I create the host, I use the .UseUrls("http://*:5001") method, and then I run the app with dotnet run.

In this way your app is accessible in your local network via the IP address of your machine and the port you've specified. Also, in order for this to work, you'd have to define a new Outbound Rule in your Firewall to allow traffic through that port you're using. Hope this helps someone else as well, this turned out to be the easiest way to get what I need to work, and that's after fighting with IIS for a while trying to get it to work through there as well.

user_1184603 · Answer

Short answer: In IIS, don't leave the site binding host name set as blank.

Longer explenation:

I received a similar error, but could see that for some reason it was trying to match the issuer domain name vs IP (the domain does point to the IP, but I guess it tries to validate the two strings). I could see this error after allowing logging : IdentityModelEventSource.ShowPII = true.

Microsoft.IdentityModel.Tokens.SecurityTokenInvalidIssuerException: IDX10205: Issuer validation failed. Issuer: 'http://ec2XXXXXom'. Did not match: validationParameters.ValidIssuer: 'http://34.111.111.29' or validationParameters.ValidIssuers: 'null'. at Microsoft.IdentityModel.Tokens.Validators.ValidateIssuer(String issuer, SecurityToken securityToken, TokenValidationParameters validationParameters)

In IIS I previously had the host name set as blank (I am using the server name as domain name) - and therefore it set the issuer using the IP of the server. When I specifically set the site domain name, it worked.

Unable to validate issuer when trying to access API

3 Answers