Using Xamarin's Cognito Federated Identities

Question

I suppose my question, Understanding Cognito Identities , was not specific enough. I still cannot figure out how to use federated authentication from the Xamarin application. Here is what I am trying, but it is really pretty random, because I cannot find any sample code for this task. I tried putting a breakpoint on the AddLogin line, and it never gets hit, although a breakpoint on two lines hits. There are too many new technologies in this code so I know where to start to identify the problem. (I x'd the identifier pool identifier in the code below, but the real one is there.) At this point, I'm just trying to get evidence that I can uniquely identify / verify my Amazon account and possibly add it to my user pool. But I can't even get the code to fully execute or report an error.

 Login().ContinueWith(t => { if (t.Exception != null) Toast.MakeText(ApplicationContext, t.Exception.ToString(), ToastLength.Long).Show(); }); public async Task Login() { CognitoAWSCredentials credentials = new CognitoAWSCredentials( "us-east-2:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx", // Identity pool ID RegionEndpoint.USEast2 // Region ); var client = new Amazon.SecurityToken.AmazonSecurityTokenServiceClient(credentials); var request = new Amazon.SecurityToken.Model.GetFederationTokenRequest(" [e-mail] "); var response = await client.GetFederationTokenAsync(request); credentials.AddLogin("www.amazon.com", response.Credentials.SessionToken); } 

Answer 1

It took a lot of searching, but I think I figured it out. Setting up services and getting a client ID is not too complicated (well documented) compared to code development, so this answer will focus on the code. Google is particularly complex due to changes made to their OAuth implementation, which prevents some forms of authentication from working. For Google IDs to work with Cognito, the API must be updated. Use NuGet to link to the following API versions or later:

• Xamarin.Auth 1.5.0.3
• Xamarin.Android.Support.v4 25.4.0.2
• Xamarin.Android.Support.CustomTabs 25.4.0.2
• AWSSDK.CognitoIdentity 3.3.2.14
• AWSSDK.Core 3.3.17.8
• Verification 2.4.15
• Xamarin.Android.Support.Annotations 25.4.0.2

This code is in the main action:

 protected override void OnCreate(Bundle savedInstanceState) { // (etc) credentials = new CognitoAWSCredentials( "us-east-2:00000000-0000-0000-0000-000000000000", // Identity pool ID RegionEndpoint.USEast2 // Region ); // (etc) } private void ShowMessage(string message) { AlertDialog dlgAlert = new AlertDialog.Builder(this).Create(); dlgAlert.SetMessage(message); dlgAlert.SetButton("Close", (s, args) => { dlgAlert.Dismiss(); }); dlgAlert.Show(); } public void Logout() { credentials.Clear(); } public void Login() { if (!string.IsNullOrEmpty(credentials.GetCachedIdentityId()) || credentials.CurrentLoginProviders.Length > 0) { if (!bDidLogin) ShowMessage(string.Format("I still remember you're {0} ", credentials.GetIdentityId())); bDidLogin = true; return; } bDidLogin = true; auth = new Xamarin.Auth.OAuth2Authenticator( "my-google-client-id.apps.googleusercontent.com", string.Empty, "openid", new System.Uri("https://accounts.google.com/o/oauth2/v2/auth"), new System.Uri("com.mynamespace.myapp:/oauth2redirect"), new System.Uri("https://www.googleapis.com/oauth2/v4/token"), isUsingNativeUI: true); auth.Completed += Auth_Completed; StartActivity(auth.GetUI(this)); } private void Auth_Completed(object sender, Xamarin.Auth.AuthenticatorCompletedEventArgs e) { if (e.IsAuthenticated) { var http = new System.Net.Http.HttpClient(); var idToken = e.Account.Properties["id_token"]; credentials.AddLogin("accounts.google.com", idToken); AmazonCognitoIdentityClient cli = new AmazonCognitoIdentityClient(credentials, RegionEndpoint.USEast2); var req = new Amazon.CognitoIdentity.Model.GetIdRequest(); req.Logins.Add("accounts.google.com", idToken); req.IdentityPoolId = "us-east-2:00000000-0000-0000-0000-000000000000"; cli.GetIdAsync(req).ContinueWith((task) => { if ((task.Status == TaskStatus.RanToCompletion) && (task.Result != null)) ShowMessage(string.Format("Identity {0} retrieved", task.Result.IdentityId)); else ShowMessage(task.Exception.InnerException!=null ? task.Exception.InnerException.Message : task.Exception.Message); }); } else ShowMessage("Login cancelled"); } 

Then there is another action to handle the callback from the redirect URL in the Google authentication process:

 [Activity(Label = "GoodleAuthInterceptor")] [IntentFilter(actions: new[] { Intent.ActionView }, Categories = new[] { Intent.CategoryDefault, Intent.CategoryBrowsable }, DataSchemes = new[] { "com.mynamespace.myapp" }, DataPaths = new[] { "/oauth2redirect" })] public class GoodleAuthInterceptor : Activity { protected override void OnCreate(Bundle savedInstanceState) { base.OnCreate(savedInstanceState); Android.Net.Uri uri_android = Intent.Data; Uri uri_netfx = new Uri(uri_android.ToString()); MainActivity.auth?.OnPageLoading(uri_netfx); Finish(); } }