Adding identity server authentication to .NET Core 3 app fails with 'Key type not specified.'

I'm trying to add identity server authentication to a .NET Core 3 API project.

I've added this code

public void ConfigureServices(IServiceCollection services)
{
    … 

    var identityBuilder = services.AddIdentityServer();

    identityBuilder.AddApiAuthorization<ApplicationUser, DbContext>();

    services
        .AddAuthentication()
        .AddIdentityServerJwt();

    var fileName = Path.Combine("Certificates", "certificatefile.pfx");
    var cert = new X509Certificate2(fileName, "veryDifficultPassword");
    identityBuilder.AddSigningCredential(cert);

    … 
}

And:

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    … 
    app.UseAuthentication();
    app.UseIdentityServer(); // <--- this line throws error.
    app.UseAuthorization();
    … 
}

There is a file which is read and loaded properly in the /Certificates folder—I can inspect the cert variable and it looks correct.

Everything I have tried so far ends with the line app.UseIdentityServer(); blowing up with:

System.InvalidOperationException: 'Key type not specified.'

Any suggestions?

Update: Including stacktrace

System.InvalidOperationException
  HResult=0x80131509
  Message=Key type not specified.
  Source=Microsoft.AspNetCore.ApiAuthorization.IdentityServer
  StackTrace:
   at Microsoft.AspNetCore.ApiAuthorization.IdentityServer.ConfigureSigningCredentials.LoadKey()
   at Microsoft.AspNetCore.ApiAuthorization.IdentityServer.ConfigureSigningCredentials.Configure(ApiAuthorizationOptions options)
   at Microsoft.Extensions.Options.OptionsFactory`1.Create(String name)
   at Microsoft.Extensions.Options.OptionsManager`1.<>c__DisplayClass5_0.<Get>b__0()
   at System.Lazy`1.ViaFactory(LazyThreadSafetyMode mode)
   at System.Lazy`1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor)
   at System.Lazy`1.CreateValue()
   at System.Lazy`1.get_Value()
   at Microsoft.Extensions.Options.OptionsCache`1.GetOrAdd(String name, Func`1 createOptions)
   at Microsoft.Extensions.Options.OptionsManager`1.Get(String name)
   at Microsoft.Extensions.Options.OptionsManager`1.get_Value()
   at Microsoft.Extensions.DependencyInjection.IdentityServerBuilderConfigurationExtensions.<>c.<AddClients>b__7_1(IServiceProvider sp)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitFactory(FactoryCallSite factoryCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitCache(ServiceCallSite callSite, RuntimeResolverContext context, ServiceProviderEngineScope serviceProviderEngine, RuntimeResolverLock lockType)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitRootCache(ServiceCallSite singletonCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitDisposeCache(ServiceCallSite transientCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitConstructor(ConstructorCallSite constructorCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSiteMain(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.VisitDisposeCache(ServiceCallSite transientCallSite, RuntimeResolverContext context)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteVisitor`2.VisitCallSite(ServiceCallSite callSite, TArgument argument)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.CallSiteRuntimeResolver.Resolve(ServiceCallSite callSite, ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.DynamicServiceProviderEngine.<>c__DisplayClass1_0.<RealizeService>b__0(ServiceProviderEngineScope scope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngine.GetService(Type serviceType, ServiceProviderEngineScope serviceProviderEngineScope)
   at Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceProviderEngineScope.GetService(Type serviceType)
   at Microsoft.AspNetCore.Builder.IdentityServerApplicationBuilderExtensions.TestService(IServiceProvider serviceProvider, Type service, ILogger logger, String message, Boolean doThrow)
   at Microsoft.AspNetCore.Builder.IdentityServerApplicationBuilderExtensions.Validate(IApplicationBuilder app)
   at Microsoft.AspNetCore.Builder.IdentityServerApplicationBuilderExtensions.UseIdentityServer(IApplicationBuilder app, IdentityServerMiddlewareOptions options)
   at Boskapstorget.API.Startup.Configure(IApplicationBuilder app, IWebHostEnvironment env) in C:\Private\Kod\Boskapstorget\Backend\src\Boskapstorget.API\Startup.cs:line 86
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Microsoft.AspNetCore.Hosting.ConfigureBuilder.Invoke(Object instance, IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.ConfigureBuilder.<>c__DisplayClass4_0.<Build>b__0(IApplicationBuilder builder)
   at Microsoft.AspNetCore.Hosting.GenericWebHostBuilder.<>c__DisplayClass13_0.<UseStartup>b__2(IApplicationBuilder app)
   at Microsoft.AspNetCore.Mvc.Filters.MiddlewareFilterBuilderStartupFilter.<>c__DisplayClass0_0.<Configure>g__MiddlewareFilterBuilder|0(IApplicationBuilder builder)
   at Microsoft.AspNetCore.HostFilteringStartupFilter.<>c__DisplayClass0_0.<Configure>b__0(IApplicationBuilder app)
   at Microsoft.AspNetCore.Hosting.GenericWebHostService.<StartAsync>d__31.MoveNext()

I don't think that the code you have added to install a signing certificate has caused the problem. The code in the stacktrace is being executed because identityBuilder.AddApiAuthorization<ApplicationUser, DbContext>(); calls AddSigningCredentials() which eventually configures code to look in appsettings.json for key definition Microsoft.AspNetCore.ApiAuthorization.IdentityServer.ConfigureSigningCredentials:

public SigningCredentials LoadKey()
{
    var key = new KeyDefinition();
    _configuration.Bind(key);
    switch (key.Type)
    {
        case KeySources.Development:
            var developmentKeyPath = Path.Combine(Directory.GetCurrentDirectory(), key.FilePath ?? DefaultTempKeyRelativePath);
            var createIfMissing = key.Persisted ?? true;
            _logger.LogInformation($"Loading development key at '{developmentKeyPath}'.");
            var developmentKey = new RsaSecurityKey(SigningKeysLoader.LoadDevelopment(developmentKeyPath, createIfMissing))
            {
                KeyId = "Development"
            };
            return new SigningCredentials(developmentKey, "RS256");
        case KeySources.File:
            var pfxPath = Path.Combine(Directory.GetCurrentDirectory(), key.FilePath);
            var pfxPassword = key.Password;
            var storageFlags = GetStorageFlags(key);
            _logger.LogInformation($"Loading certificate file at '{pfxPath}' with storage flags '{key.StorageFlags}'.");
            return new SigningCredentials(new X509SecurityKey(SigningKeysLoader.LoadFromFile(pfxPath, key.Password, storageFlags)), "RS256");
        case KeySources.Store:
            if (!Enum.TryParse<StoreLocation>(key.StoreLocation, out var storeLocation))
            {
                throw new InvalidOperationException($"Invalid certificate store location '{key.StoreLocation}'.");
            }
            _logger.LogInformation($"Loading certificate with subject '{key.Name}' in '{key.StoreLocation}\\{key.StoreName}'.");
            return new SigningCredentials(new X509SecurityKey(SigningKeysLoader.LoadFromStoreCert(key.Name, key.StoreName, storeLocation, GetCurrentTime())), "RS256");
        case null:
            throw new InvalidOperationException($"Key type not specified.");
        default:
            throw new InvalidOperationException($"Invalid key type '{key.Type ?? "(null)"}'.");
    }
}

You are hitting the null case because your appsettings.json or appsettings.Development.json file does not configure the Key.

I can reproduce your problem in 2 ways:

Commenting out the key configuration in appsetting.Development.json

{
  "Logging": {
    "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
    }
  },
  "IdentityServer": {
    //"Key": {
    //  "Type": "Development"
    //}
  }
}

This assumes you are running\debugging in Development environment

The second way to reproduce is to configure to run in Production which doesn't have a Key definition by default in appsettings.json

I think the solution to your problem would be to define the certificate file in appsettings.json or appsettings.Development.json:

{
  "Logging": {
    "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
    }
  },
  "IdentityServer": {
    "Key": {
      "Type": "File",
      "FilePath": "Certificates\\certificatefile.pfx",
      "Password": "veryDifficultPassword"
    }
  }
}

and remove this code

var fileName = Path.Combine("Certificates", "certificatefile.pfx");
var cert = new X509Certificate2(fileName, "veryDifficultPassword");
identityBuilder.AddSigningCredential(cert);