Getting "IDX10108: The address specified is not valid as per HTTPS scheme" when calling IdentityServer4 in AWS - ssl

Question

We've implemented an Identity Server using IdentityServer4 and have deployed it to AWS. It works great until we enabled https on the ELB. Now when the client tries to authenticate we get the following error:
Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[0]
An unhandled exception has occurred while executing the request
System.InvalidOperationException: IDX10803: Unable to obtain configuration from: 'https://int.mycompany.com/.well-known/openid-configuration'. ---> System.ArgumentException: IDX10108: The address specified is not valid as per HTTPS scheme. Please specify an https address for security reasons. If you want to test with http address, set the RequireHttps property on IDocumentRetriever to false.
From what I've read the client is not happy with the certificate. This could possibly be related to the host name of the identity server and the name in the certificate. We have a valid wildcard certificate with subject "*.mycompany.com". We configured the client with Authority as "https://int.mycompany.com" so that seems to line up.
I've also read in these load balancing configuration that some headers have to be forwarded to the middleware but I'm not exactly sure how that would work.

Answer 1

Looks like HTTPS request are not recognized as such. Try to add the following settings into ConfigureServices method in the Startup class:
services.Configure<ForwardedHeadersOptions>(options =>
{
options.ForwardedHeaders = ForwardedHeaders.XForwardedProto;
});
From HTTP Headers and Elastic Load Balancing AWS documentation:
The X-Forwarded-Proto request header helps you identify the protocol (HTTP or HTTPS) that a client used to connect to your server. Your server access logs contain only the protocol used between the server and the load balancer; they contain no information about the protocol used between the client and the load balancer. To determine the protocol used between the client and the load balancer, use the X-Forwarded-Proto request header. Elastic Load Balancing stores the protocol used between the client and the load balancer in the X-Forwarded-Proto request header and passes the header along to your server.