Google Api

Yavsc/GoogleApiSupport/Google.Apis.Auth/OAuth2/Web/AuthWebUtility.cs

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+/*
+Copyright 2013 Google Inc
+
+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 System;
+using System.Threading.Tasks;
+
+using Google.Apis.Auth.OAuth2.Responses;
+using Google.Apis.Util.Store;
+
+namespace Google.Apis.Auth.OAuth2.Web
+{
+    /// <summary>Auth Utility methods for web development.</summary>
+    public class AuthWebUtility
+    {
+        /// <summary>Extracts the redirect URI from the state OAuth2 parameter.</summary>
+        /// <remarks>
+        /// If the data store is not <c>null</c>, this method verifies that the state parameter which was returned
+        /// from the authorization server is the same as the one we set before redirecting to the authorization server.
+        /// </remarks>
+        /// <param name="dataStore">The data store which contains the original state parameter.</param>
+        /// <param name="userId">User identifier.</param>
+        /// <param name="state">
+        /// The authorization state parameter which we got back from the authorization server.
+        /// </param>
+        /// <returns>Redirect URI to the address which initializes the authorization code flow.</returns>
+        public static async Task<string> ExtracRedirectFromState(IDataStore dataStore, string userId, string state)
+        {
+            var oauthState = state;
+            if (dataStore != null)
+            {
+                var userKey = AuthorizationCodeWebApp.StateKey + userId;
+                var expectedState = await dataStore.GetAsync<string>(userKey).ConfigureAwait(false);
+
+                // Verify that the stored state is equal to the one we got back from the authorization server.
+                if (!Object.Equals(oauthState, expectedState))
+                {
+                    throw new TokenResponseException(new TokenErrorResponse
+                    {
+                        Error = "State is invalid"
+                    });
+                }
+                await dataStore.DeleteAsync<string>(userKey).ConfigureAwait(false);
+                oauthState = oauthState.Substring(0, oauthState.Length - AuthorizationCodeWebApp.StateRandomLength);
+            }
+
+            return oauthState;
+        }
+    }
+}