use universal Gitea OAuth configuration (#1442)

https://docs.gitea.com/next/development/oauth2-provider?_highlight=oauth#pre-configured-applications

Tested with https://try.gitea.io/

Fixes #1426

src/shared/Core.Tests/GenericOAuthConfigTests.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using GitCredentialManager.Tests.Objects;
 using Xunit;
 
@@ -9,7 +10,9 @@ public class GenericOAuthConfigTests
         [Fact]
         public void GenericOAuthConfig_TryGet_Valid_ReturnsTrue()
         {
-            var remoteUri = new Uri("https://example.com");
+            var protocol = "https";
+            var host = "example.com";
+            var remoteUri = new Uri($"{protocol}://{host}");
             const string expectedClientId = "115845b0-77f8-4c06-a3dc-7d277381fad1";
             const string expectedClientSecret = "4D35385D9F24";
             const string expectedUserName = "TEST_USER";
@@ -44,7 +47,12 @@ public void GenericOAuthConfig_TryGet_Valid_ReturnsTrue()
                 RemoteUri = remoteUri
             };
 
-            bool result = GenericOAuthConfig.TryGet(trace, settings, remoteUri, out GenericOAuthConfig config);
+            var input = new InputArguments(new Dictionary<string, string> {
+                {"protocol", protocol},
+                {"host", host}, 
+            });
+
+            bool result = GenericOAuthConfig.TryGet(trace, settings, input, out GenericOAuthConfig config);
 
             Assert.True(result);
             Assert.Equal(expectedClientId, config.ClientId);
@@ -57,5 +65,39 @@ public void GenericOAuthConfig_TryGet_Valid_ReturnsTrue()
             Assert.Equal(expectedUserName, config.DefaultUserName);
             Assert.True(config.UseAuthHeader);
         }
+
+        [Fact]
+        public void GenericOAuthConfig_TryGet_Gitea()
+        {
+            var protocol = "https";
+            var host = "example.com";
+            var remoteUri = new Uri($"{protocol}://{host}");
+            const string expectedClientId = GenericOAuthConfig.WellKnown.GiteaClientId;
+            string[] expectedScopes = Array.Empty<string>();
+            var expectedRedirectUri = GenericOAuthConfig.WellKnown.LocalIPv4RedirectUri;
+            var expectedAuthzEndpoint = new Uri(remoteUri, GenericOAuthConfig.WellKnown.GiteaAuthzEndpoint);
+            var expectedTokenEndpoint = new Uri(remoteUri, GenericOAuthConfig.WellKnown.GiteaTokenEndpoint);
+
+            var trace = new NullTrace();
+            var settings = new TestSettings
+            {
+                RemoteUri = remoteUri
+            };
+
+            var input = new InputArguments(new Dictionary<string, string> {
+                {"protocol", protocol},
+                {"host", host},
+                {"wwwauth", "Basic realm=\"Gitea\""}
+            });
+
+            bool result = GenericOAuthConfig.TryGet(trace, settings, input, out GenericOAuthConfig config);
+
+            Assert.True(result);
+            Assert.Equal(expectedClientId, config.ClientId);
+            Assert.Equal(expectedRedirectUri, config.RedirectUri);
+            Assert.Equal(expectedScopes, config.Scopes);
+            Assert.Equal(expectedAuthzEndpoint, config.Endpoints.AuthorizationEndpoint);
+            Assert.Equal(expectedTokenEndpoint, config.Endpoints.TokenEndpoint);
+        }
     }
 }

src/shared/Core/GenericHostProvider.cs

@@ -63,7 +63,7 @@ public override async Task<ICredential> GenerateCredentialAsync(InputArguments i
                 // Cannot check WIA or OAuth support for non-HTTP based protocols
             }
             // Check for an OAuth configuration for this remote
-            else if (GenericOAuthConfig.TryGet(Context.Trace, Context.Settings, uri, out GenericOAuthConfig oauthConfig))
+            else if (GenericOAuthConfig.TryGet(Context.Trace, Context.Settings, input, out GenericOAuthConfig oauthConfig))
             {
                 Context.Trace.WriteLine($"Found generic OAuth configuration for '{uri}':");
                 Context.Trace.WriteLine($"\tAuthzEndpoint   = {oauthConfig.Endpoints.AuthorizationEndpoint}");

src/shared/Core/GenericOAuthConfig.cs

@@ -1,32 +1,55 @@
 using System;
+using System.Collections.Generic;
+using System.Linq;
 using GitCredentialManager.Authentication.OAuth;
 
 namespace GitCredentialManager
 {
     public class GenericOAuthConfig
     {
-        public static bool TryGet(ITrace trace, ISettings settings, Uri remoteUri, out GenericOAuthConfig config)
+        public static bool TryGet(ITrace trace, ISettings settings, InputArguments input, out GenericOAuthConfig config)
         {
             config = new GenericOAuthConfig();
+            Uri authzEndpointUri = null;
+            Uri tokenEndpointUri = null;
+            var remoteUri = input.GetRemoteUri();
 
-            if (!settings.TryGetSetting(
+            if (input.WwwAuth.Any(x => x.Contains("Basic realm=\"Gitea\"", StringComparison.OrdinalIgnoreCase)))
+            {
+                trace.WriteLine($"Using universal Gitea OAuth configuration");
+                // https://docs.gitea.com/next/development/oauth2-provider?_highlight=oauth#pre-configured-applications
+                config.ClientId = WellKnown.GiteaClientId;
+                authzEndpointUri = new Uri(remoteUri, WellKnown.GiteaAuthzEndpoint);
+                tokenEndpointUri = new Uri(remoteUri, WellKnown.GiteaTokenEndpoint);
+                config.RedirectUri = WellKnown.LocalIPv4RedirectUri;
+            }
+
+            if (settings.TryGetSetting(
                     Constants.EnvironmentVariables.OAuthAuthzEndpoint,
                     Constants.GitConfiguration.Credential.SectionName,
                     Constants.GitConfiguration.Credential.OAuthAuthzEndpoint,
-                    out string authzEndpoint) ||
-                !Uri.TryCreate(remoteUri, authzEndpoint, out Uri authzEndpointUri))
+                    out string authzEndpoint))
+            {
+                Uri.TryCreate(remoteUri, authzEndpoint, out authzEndpointUri);
+            }
+
+            if (authzEndpointUri == null)
             {
                 trace.WriteLine($"Invalid OAuth configuration - missing/invalid authorize endpoint: {authzEndpoint}");
                 config = null;
                 return false;
             }
 
-            if (!settings.TryGetSetting(
+            if (settings.TryGetSetting(
                     Constants.EnvironmentVariables.OAuthTokenEndpoint,
                     Constants.GitConfiguration.Credential.SectionName,
                     Constants.GitConfiguration.Credential.OAuthTokenEndpoint,
-                    out string tokenEndpoint) ||
-                !Uri.TryCreate(remoteUri, tokenEndpoint, out Uri tokenEndpointUri))
+                    out string tokenEndpoint))
+            {
+                Uri.TryCreate(remoteUri, tokenEndpoint, out tokenEndpointUri);
+            }
+
+            if (tokenEndpointUri == null)
             {
                 trace.WriteLine($"Invalid OAuth configuration - missing/invalid token endpoint: {tokenEndpoint}");
                 config = null;
@@ -74,12 +97,12 @@ public static bool TryGet(ITrace trace, ISettings settings, Uri remoteUri, out G
                     Constants.EnvironmentVariables.OAuthRedirectUri,
                     Constants.GitConfiguration.Credential.SectionName,
                     Constants.GitConfiguration.Credential.OAuthRedirectUri,
-                    out string redirectUrl) &&
-                Uri.TryCreate(redirectUrl, UriKind.Absolute, out Uri redirectUri))
+                    out string redirectUrl) && Uri.TryCreate(redirectUrl, UriKind.Absolute, out Uri redirectUri))
             {
                 config.RedirectUri = redirectUri;
             }
-            else
+
+            if (config.RedirectUri == null)
             {
                 trace.WriteLine($"Invalid OAuth configuration - missing/invalid redirect URI: {redirectUrl}");
                 config = null;
@@ -134,5 +157,15 @@ public static bool TryGet(ITrace trace, ISettings settings, Uri remoteUri, out G
         public string DefaultUserName { get; set; }
 
         public bool SupportsDeviceCode => Endpoints.DeviceAuthorizationEndpoint != null;
+
+    public static class WellKnown
+    {
+        // https://docs.gitea.com/next/development/oauth2-provider?_highlight=oauth#pre-configured-applications
+        public const string GiteaClientId = "e90ee53c-94e2-48ac-9358-a874fb9e0662";
+        // https://docs.gitea.com/next/development/oauth2-provider?_highlight=oauth#endpoints
+        public const string GiteaAuthzEndpoint = "/login/oauth/authorize";
+        public const string GiteaTokenEndpoint = "/login/oauth/access_token";
+        public static Uri LocalIPv4RedirectUri = new Uri("http://127.0.0.1");
+    }
     }
 }