How to add token for Auth0 remote API using IHttpClientFactory Blazor WASM

Question

I have a Blazor WASM application that uses Auth0 Asp.net Hosted authorization model. I can authorize the WASM application properly but I cannot seem to attach the token to my Http requests.

The problematic code is as follows:

Program.cs

builder.Services.AddHttpClient("ServerAPI",
      client => client.BaseAddress = new Uri("https://localhost:7083/"))
    .AddHttpMessageHandler<BaseAddressAuthorizationMessageHandler>();

builder.Services.AddScoped(sp => sp.GetRequiredService<IHttpClientFactory>()
  .CreateClient("ServerAPI"));

client.BaseAddress localhost:7083 is a remote server, so I cannot use BaseAddressAuthorizationMessageHandler to attach the token.

For trouble shootings sake, if I adjust the address as follows:

builder.Services.AddHttpClient("ServerAPI",
      client => client.BaseAddress = new Uri(builder.HostEnvironment.BaseAddress))
    .AddHttpMessageHandler<BaseAddressAuthorizationMessageHandler>();

You can see the token is included in the request

When I revert it back to:

builder.Services.AddHttpClient("ServerAPI",
          client => client.BaseAddress = new Uri("https://localhost:7083/"))
        .AddHttpMessageHandler<BaseAddressAuthorizationMessageHandler>();

I don't have the token anymore

My question is how can I configure my IHttpClient to include the token for a remote API? Ideally, I would like to keep this configuration including the token in the middleware Program.cs file. I believe the solution is a custom HttpMessageHandler but I'm not sure how to achieve that.

Answer 1

The solution was to create your own custom AuthorizationMessageHandler class. Here is my implementation incase anyone else has the same issue.

CustomAuthorizationMessageHandler.cs

public class CustomAuthorizationMessageHandler : AuthorizationMessageHandler
    {
        public CustomAuthorizationMessageHandler(IAccessTokenProvider provider,
            NavigationManager navigationManager)
            : base(provider, navigationManager)
        {
            ConfigureHandler(
               authorizedUrls: new[] { "https://localhost:7083" });

        }
    }

Program.cs

builder.Services.AddScoped<CustomAuthorizationMessageHandler>();

builder.Services.AddHttpClient("ServerAPI",
      client => {
          client.BaseAddress = new Uri("https://localhost:7083");
          }
      )
    .AddHttpMessageHandler<CustomAuthorizationMessageHandler>();

builder.Services.AddScoped(sp => sp.GetRequiredService<IHttpClientFactory>()
  .CreateClient("ServerAPI"));

The token is now injected into the Http request