OAuth.xaml.cs

// Copyright 2017 Esri.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
// You may obtain a copy of the License at: http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an 
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific 
// language governing permissions and limitations under the License.

using Esri.ArcGISRuntime.Mapping;
using Esri.ArcGISRuntime.Portal;
using Esri.ArcGISRuntime.Security;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Xamarin.Forms;


#if __IOS__
using Xamarin.Auth;
using Xamarin.Forms.Platform.iOS;
using UIKit;
#endif

#if __ANDROID__
using Android.App;
using Xamarin.Auth;
using System.IO;
#endif

namespace ArcGISRuntime.Samples.OAuth
{
    [ArcGISRuntime.Samples.Shared.Attributes.Sample(
           "Authenticate with OAuth",
           "Security",
           "This sample demonstrates how to authenticate with ArcGIS Online (or your own portal) using OAuth2 to access a secure web map (or the secured layers it contains). Accessing secured items requires a login on the portal (an ArcGIS Online account, for example).",
           "1. When you run the sample, the app will load a web map that contains premium content.\n2. You will be challenged for an ArcGIS Online login to view that layer (world traffic).\n3. Enter your ArcGIS Online user name and password.\n4. If you authenticate successfully, the traffic layer will display, otherwise the map will contain only the public basemap layer.\n5. You can alter the code to supply OAuth configuration settings specific to your app.",
           "Authentication, Security, OAuth")]
    public partial class OAuth : ContentPage, IOAuthAuthorizeHandler
    {
        // Constants for OAuth-related values.
        // - The URL of the portal to authenticate with
        private const string ServerUrl = "https://www.arcgis.com/sharing/rest";
        // - The Client ID for an app registered with the server (the ID below is for a public app created by the ArcGIS Runtime team).
        private const string AppClientId = @"lgAdHkYZYlwwfAhC";
        // - An optional client secret for the app (only needed for the OAuthAuthorizationCode authorization type).
        private const string ClientSecret = "";
        // - A URL for redirecting after a successful authorization (this must be a URL configured with the app).
        private const string OAuthRedirectUrl = @"my-ags-app://auth";
        // - The ID for a web map item hosted on the server (the ID below is for a traffic map of Paris).
        private const string WebMapId = "e5039444ef3c48b8a8fdc9227f9be7c1";

        public OAuth()
        {
            InitializeComponent();

            // Call a function to initialize the app and request a web map (with secured layers) to display.
            Initialize();
        }

        private async void Initialize()
        {
            try
            {
                // Set up the AuthenticationManager to use OAuth for secure ArcGIS Online requests.
                SetOAuthInfo();

                // Connect to the portal (ArcGIS Online, for example).
                ArcGISPortal arcgisPortal = await ArcGISPortal.CreateAsync(new Uri(ServerUrl));

                // Get a web map portal item using its ID.
                // If the item contains layers not shared publicly, the user will be challenged for credentials at this point.
                PortalItem portalItem = await PortalItem.CreateAsync(arcgisPortal, WebMapId);
            
                // Create a new map with the portal item and display it in the map view.
                // If authentication failed, only the public layers will be displayed.
                Map myMap = new Map(portalItem);
                MyMapView.Map = myMap;
            }
            catch (Exception e)
            {
                await ((Page)Parent).DisplayAlert("Error", e.ToString(), "OK");
            }
        }

        private void SetOAuthInfo()
        {
            // Register the server information with the AuthenticationManager.
            ServerInfo serverInfo = new ServerInfo
            {
                ServerUri = new Uri(ServerUrl),
                TokenAuthenticationType = TokenAuthenticationType.OAuthImplicit,
                OAuthClientInfo = new OAuthClientInfo
                {
                    ClientId = AppClientId,
                    RedirectUri = new Uri(OAuthRedirectUrl)
                }
            };

            // If a client secret has been configured, set the authentication type to OAuthAuthorizationCode.
            if (!String.IsNullOrEmpty(ClientSecret))
            {
                // Use OAuthAuthorizationCode if you need a refresh token (and have specified a valid client secret).
                serverInfo.TokenAuthenticationType = TokenAuthenticationType.OAuthAuthorizationCode;
                serverInfo.OAuthClientInfo.ClientSecret = ClientSecret;
            }

            // Register this server with AuthenticationManager.
            AuthenticationManager.Current.RegisterServer(serverInfo);
            
            // Use a function in this class to challenge for credentials.
            AuthenticationManager.Current.ChallengeHandler = new ChallengeHandler(CreateCredentialAsync);

            // Set the OAuthAuthorizeHandler component (this class) for Android or iOS platforms.
#if __ANDROID__ || __IOS__
            AuthenticationManager.Current.OAuthAuthorizeHandler = this;
#endif
        }
        
        // ChallengeHandler function that will be called whenever access to a secured resource is attempted.
        public async Task<Credential> CreateCredentialAsync(CredentialRequestInfo info)
        {
            Credential credential = null;

            try
            {
                // IOAuthAuthorizeHandler will challenge the user for OAuth credentials.
                credential = await AuthenticationManager.Current.GenerateCredentialAsync(info.ServiceUri);
            }
            catch (TaskCanceledException) { return credential; }
            catch (Exception)
            {
                // Exception will be reported in calling function.
                throw;
            }

            return credential;
        }

        #region IOAuthAuthorizationHandler implementation
        // Use a TaskCompletionSource to track the completion of the authorization.
        private TaskCompletionSource<IDictionary<string, string>> _taskCompletionSource;

        // IOAuthAuthorizeHandler.AuthorizeAsync implementation.
        public Task<IDictionary<string, string>> AuthorizeAsync(Uri serviceUri, Uri authorizeUri, Uri callbackUri)
        {
            // If the TaskCompletionSource is not null, authorization may already be in progress and should be canceled.
            if (_taskCompletionSource != null)
            {
                // Try to cancel any existing authentication task.
                _taskCompletionSource.TrySetCanceled();
            }

            // Create a task completion source.
            _taskCompletionSource = new TaskCompletionSource<IDictionary<string, string>>();
#if __ANDROID__ || __IOS__

#if __ANDROID__
            // Get the current Android Activity.
            Activity activity = (Activity)ArcGISRuntime.Droid.MainActivity.Instance;
#endif
#if __IOS__
            // Get the current iOS ViewController.
            UIViewController viewController = null;
            Device.BeginInvokeOnMainThread(() =>
            {
                viewController = UIApplication.SharedApplication.KeyWindow.RootViewController;
            });
#endif
            // Create a new Xamarin.Auth.OAuth2Authenticator using the information passed in.
            OAuth2Authenticator authenticator = new OAuth2Authenticator(
                clientId: AppClientId,
                scope: "",
                authorizeUrl: authorizeUri,
                redirectUrl: callbackUri)
            {
                ShowErrors = false,
                // Allow the user to cancel the OAuth attempt.
                AllowCancel = true
            };

            // Define a handler for the OAuth2Authenticator.Completed event.
            authenticator.Completed += (sender, authArgs) =>
            {
                try
                {
#if __IOS__
                    // Dismiss the OAuth UI when complete.
                    viewController.DismissViewController(true, null);
#endif

                    // Check if the user is authenticated.
                    if (authArgs.IsAuthenticated)
                    {
                        // If authorization was successful, get the user's account.
                        Xamarin.Auth.Account authenticatedAccount = authArgs.Account;

                        // Set the result (Credential) for the TaskCompletionSource.
                        _taskCompletionSource.SetResult(authenticatedAccount.Properties);
                    }
                    else
                    {
                        throw new Exception("Unable to authenticate user.");
                    }
                }
                catch (Exception ex)
                {
                    // If authentication failed, set the exception on the TaskCompletionSource.
                    _taskCompletionSource.TrySetException(ex);

                    // Cancel authentication.
                    authenticator.OnCancelled();
                }
                finally
                {
                    // Dismiss the OAuth login.
#if __ANDROID__ 
                    activity.FinishActivity(99);
#endif
                }
            };

            // If an error was encountered when authenticating, set the exception on the TaskCompletionSource.
            authenticator.Error += (sndr, errArgs) =>
            {
                // If the user cancels, the Error event is raised but there is no exception ... best to check first.
                if (errArgs.Exception != null)
                {
                    _taskCompletionSource.TrySetException(errArgs.Exception);
                }
                else
                {
                    // Login canceled: dismiss the OAuth login.
                    if (_taskCompletionSource != null)
                    {
                        _taskCompletionSource.TrySetCanceled();
#if __ANDROID__ 
                        activity.FinishActivity(99);
#endif
                    }
                }

                // Cancel authentication.
                authenticator.OnCancelled();
            };

            // Present the OAuth UI so the user can enter user name and password.
#if __ANDROID__
            var intent = authenticator.GetUI(activity);
            activity.StartActivityForResult(intent, 99);
#endif
#if __IOS__
            // Present the OAuth UI (on the app's UI thread) so the user can enter user name and password.
            Device.BeginInvokeOnMainThread(() =>
            {
                viewController.PresentViewController(authenticator.GetUI(), true, null);
            });
#endif

#endif // (If Android or iOS)
            // Return completion source task so the caller can await completion.
            return _taskCompletionSource.Task;
        }
#endregion 
    }
}