Implemented basis Token Endpoint fetching

Added retrieving of Token Endpoint if only the Issuer is provided to the builder

Added some documentation to OAuth2Client and IOAuth2Client

Remove synchronous `Build` method.

Author: Lyphion

projects/RabbitMQ.Client.OAuth2/IOAuth2Client.cs

@@ -36,7 +36,19 @@ namespace RabbitMQ.Client.OAuth2
 {
     public interface IOAuth2Client
     {
+        /// <summary>
+        /// Request a new AccessToken from the Token Endpoint.
+        /// </summary>
+        /// <param name="cancellationToken">Cancellation token for this request</param>
+        /// <returns>Token with Access and Refresh Token</returns>
         Task<IToken> RequestTokenAsync(CancellationToken cancellationToken = default);
+
+        /// <summary>
+        /// Request a new AccessToken using the Refresh Token from the Token Endpoint.
+        /// </summary>
+        /// <param name="token">Token with the Refresh Token</param>
+        /// <param name="cancellationToken">Cancellation token for this request</param>
+        /// <returns>Token with Access and Refresh Token</returns>
         Task<IToken> RefreshTokenAsync(IToken token, CancellationToken cancellationToken = default);
     }
 }

projects/RabbitMQ.Client.OAuth2/OAuth2Client.cs

@@ -42,58 +42,147 @@ namespace RabbitMQ.Client.OAuth2
 {
     public class OAuth2ClientBuilder
     {
+        /// <summary>
+        /// Discovery endpoint subpath for all OpenID Connect issuers.
+        /// </summary>
+        const string DISCOVERY_ENDPOINT = ".well-known/openid-configuration";
+
         private readonly string _clientId;
         private readonly string _clientSecret;
-        private readonly Uri _tokenEndpoint;
+
+        // At least one of the following Uris is not null
+        private readonly Uri? _tokenEndpoint;
+        private readonly Uri? _issuer;
+
         private string? _scope;
         private IDictionary<string, string>? _additionalRequestParameters;
         private HttpClientHandler? _httpClientHandler;
 
-        public OAuth2ClientBuilder(string clientId, string clientSecret, Uri tokenEndpoint)
+        /// <summary>
+        /// Create a new builder for creating <see cref="OAuth2Client"/>s.
+        /// </summary>
+        /// <param name="clientId">Id of the client</param>
+        /// <param name="clientSecret">Secret of the client</param>
+        /// <param name="tokenEndpoint">Endpoint to receive the Access Token</param>
+        /// <param name="issuer">Issuer of the Access Token. Used to automaticly receive the Token Endpoint while building</param>
+        /// <remarks>
+        /// Either <paramref name="tokenEndpoint"/> or <paramref name="issuer"/> must be provided.
+        /// </remarks>
+        public OAuth2ClientBuilder(string clientId, string clientSecret, Uri? tokenEndpoint = null, Uri? issuer = null)
         {
             _clientId = clientId ?? throw new ArgumentNullException(nameof(clientId));
             _clientSecret = clientSecret ?? throw new ArgumentNullException(nameof(clientSecret));
-            _tokenEndpoint = tokenEndpoint ?? throw new ArgumentNullException(nameof(tokenEndpoint));
+
+            if (tokenEndpoint is null && issuer is null)
+            {
+                throw new ArgumentException("Either tokenEndpoint or issuer is required");
+            }
+
+            _tokenEndpoint = tokenEndpoint;
+            _issuer = issuer;
         }
 
+        /// <summary>
+        /// Set the requested scopes for the client.
+        /// </summary>
+        /// <param name="scope">OAuth scopes to request from the Issuer</param>
         public OAuth2ClientBuilder SetScope(string scope)
         {
             _scope = scope ?? throw new ArgumentNullException(nameof(scope));
             return this;
         }
 
+        /// <summary>
+        /// Set custom HTTP Client handler for requests of the OAuth2 client.
+        /// </summary>
+        /// <param name="handler">Custom handler for HTTP requests</param>
         public OAuth2ClientBuilder SetHttpClientHandler(HttpClientHandler handler)
         {
             _httpClientHandler = handler ?? throw new ArgumentNullException(nameof(handler));
             return this;
         }
 
+        /// <summary>
+        /// Add a additional request parameter to each HTTP request.
+        /// </summary>
+        /// <param name="param">Name of the parameter</param>
+        /// <param name="paramValue">Value of the parameter</param>
         public OAuth2ClientBuilder AddRequestParameter(string param, string paramValue)
         {
-            if (param == null)
+            if (param is null)
             {
-                throw new ArgumentNullException("param is null");
+                throw new ArgumentNullException(nameof(param));
             }
 
-            if (paramValue == null)
+            if (paramValue is null)
             {
-                throw new ArgumentNullException("paramValue is null");
+                throw new ArgumentNullException(nameof(paramValue));
             }
 
-            if (_additionalRequestParameters == null)
-            {
-                _additionalRequestParameters = new Dictionary<string, string>();
-            }
+            _additionalRequestParameters ??= new Dictionary<string, string>();
             _additionalRequestParameters[param] = paramValue;
 
             return this;
         }
 
-        public IOAuth2Client Build()
+        /// <summary>
+        /// Build the <see cref="OAuth2Client"/> with the provided properties of the builder.
+        /// </summary>
+        /// <param name="cancellationToken">Cancellation token for this method</param>
+        /// <returns>Configured OAuth2Client</returns>
+        public async ValueTask<IOAuth2Client> BuildAsync(CancellationToken cancellationToken = default)
         {
+            // Check if Token Endpoint is missing -> Use Issuer to receive Token Endpoint
+            if (_tokenEndpoint is null)
+            {
+                Uri tokenEndpoint = await GetTokenEndpointFromIssuerAsync(cancellationToken).ConfigureAwait(false);
+                return new OAuth2Client(_clientId, _clientSecret, tokenEndpoint,
+                    _scope, _additionalRequestParameters, _httpClientHandler);
+            }
+
             return new OAuth2Client(_clientId, _clientSecret, _tokenEndpoint,
                 _scope, _additionalRequestParameters, _httpClientHandler);
         }
+
+        /// <summary>
+        /// Receive Token Endpoint from discovery page of the Issuer.
+        /// </summary>
+        /// <param name="cancellationToken">Cancellation token for this request</param>
+        /// <returns>Uri of the Token Endpoint</returns>
+        private async Task<Uri> GetTokenEndpointFromIssuerAsync(CancellationToken cancellationToken = default)
+        {
+            if (_issuer is null)
+            {
+                throw new InvalidOperationException("The issuer is required");
+            }
+
+            using HttpClient httpClient = _httpClientHandler is null
+                ? new HttpClient()
+                : new HttpClient(_httpClientHandler, false);
+
+            httpClient.DefaultRequestHeaders.Accept.Clear();
+            httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
+
+            // Build endpoint from Issuer and dicovery endpoint, we can't use the Uri overload because the Issuer Uri may not have a trailing '/'
+            string tempIssuer = _issuer.AbsoluteUri.EndsWith("/") ? _issuer.AbsoluteUri : _issuer.AbsoluteUri + "/";
+            Uri discoveryEndpoint = new Uri(tempIssuer + DISCOVERY_ENDPOINT);
+
+            using HttpRequestMessage req = new HttpRequestMessage(HttpMethod.Get, discoveryEndpoint);
+            using HttpResponseMessage response = await httpClient.SendAsync(req, cancellationToken)
+                .ConfigureAwait(false);
+
+            response.EnsureSuccessStatusCode();
+
+            OpenIDConnectDiscovery? discovery = await response.Content.ReadFromJsonAsync<OpenIDConnectDiscovery>(cancellationToken: cancellationToken)
+                .ConfigureAwait(false);
+
+            if (discovery is null || string.IsNullOrEmpty(discovery.TokenEndpoint))
+            {
+                throw new InvalidOperationException("No token endpoint was found");
+            }
+
+            return new Uri(discovery.TokenEndpoint);
+        }
     }
 
     /**
@@ -119,7 +208,7 @@ internal class OAuth2Client : IOAuth2Client, IDisposable
 
         public static readonly IDictionary<string, string> EMPTY = new Dictionary<string, string>();
 
-        private HttpClient _httpClient;
+        private readonly HttpClient _httpClient;
 
         public OAuth2Client(string clientId, string clientSecret, Uri tokenEndpoint,
             string? scope,
@@ -132,73 +221,64 @@ public OAuth2Client(string clientId, string clientSecret, Uri tokenEndpoint,
             _additionalRequestParameters = additionalRequestParameters ?? EMPTY;
             _tokenEndpoint = tokenEndpoint;
 
-            if (httpClientHandler is null)
-            {
-                _httpClient = new HttpClient();
-            }
-            else
-            {
-                _httpClient = new HttpClient(httpClientHandler, false);
-            }
+            _httpClient = httpClientHandler is null
+                ? new HttpClient()
+                : new HttpClient(httpClientHandler, false);
 
             _httpClient.DefaultRequestHeaders.Accept.Clear();
             _httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
         }
 
+        /// <inheritdoc />
         public async Task<IToken> RequestTokenAsync(CancellationToken cancellationToken = default)
         {
             using HttpRequestMessage req = new HttpRequestMessage(HttpMethod.Post, _tokenEndpoint);
             req.Content = new FormUrlEncodedContent(BuildRequestParameters());
 
-            using HttpResponseMessage response = await _httpClient.SendAsync(req)
+            using HttpResponseMessage response = await _httpClient.SendAsync(req, cancellationToken)
                 .ConfigureAwait(false);
 
             response.EnsureSuccessStatusCode();
 
-            JsonToken? token = await response.Content.ReadFromJsonAsync<JsonToken>()
+            JsonToken? token = await response.Content.ReadFromJsonAsync<JsonToken>(cancellationToken: cancellationToken)
                 .ConfigureAwait(false);
 
             if (token is null)
             {
                 // TODO specific exception?
                 throw new InvalidOperationException("token is null");
             }
-            else
-            {
-                return new Token(token);
-            }
+
+            return new Token(token);
         }
 
+        /// <inheritdoc />
         public async Task<IToken> RefreshTokenAsync(IToken token,
             CancellationToken cancellationToken = default)
         {
-            if (token.RefreshToken == null)
+            if (token.RefreshToken is null)
             {
                 throw new InvalidOperationException("Token has no Refresh Token");
             }
 
-            using HttpRequestMessage req = new HttpRequestMessage(HttpMethod.Post, _tokenEndpoint)
-            {
-                Content = new FormUrlEncodedContent(BuildRefreshParameters(token))
-            };
+            using HttpRequestMessage req = new HttpRequestMessage(HttpMethod.Post, _tokenEndpoint);
+            req.Content = new FormUrlEncodedContent(BuildRefreshParameters(token));
 
-            using HttpResponseMessage response = await _httpClient.SendAsync(req)
+            using HttpResponseMessage response = await _httpClient.SendAsync(req, cancellationToken)
                 .ConfigureAwait(false);
 
             response.EnsureSuccessStatusCode();
 
-            JsonToken? refreshedToken = await response.Content.ReadFromJsonAsync<JsonToken>()
+            JsonToken? refreshedToken = await response.Content.ReadFromJsonAsync<JsonToken>(cancellationToken: cancellationToken)
                 .ConfigureAwait(false);
 
             if (refreshedToken is null)
             {
                 // TODO specific exception?
                 throw new InvalidOperationException("refreshed token is null");
             }
-            else
-            {
-                return new Token(refreshedToken);
-            }
+
+            return new Token(refreshedToken);
         }
 
         public void Dispose()
@@ -214,9 +294,9 @@ private Dictionary<string, string> BuildRequestParameters()
                 { CLIENT_SECRET, _clientSecret }
             };
 
-            if (_scope != null && _scope.Length > 0)
+            if (!string.IsNullOrEmpty(_scope))
             {
-                dict.Add(SCOPE, _scope);
+                dict.Add(SCOPE, _scope!);
             }
 
             dict.Add(GRANT_TYPE, GRANT_TYPE_CLIENT_CREDENTIALS);
@@ -227,8 +307,7 @@ private Dictionary<string, string> BuildRequestParameters()
         private Dictionary<string, string> BuildRefreshParameters(IToken token)
         {
             Dictionary<string, string> dict = BuildRequestParameters();
-            dict.Remove(GRANT_TYPE);
-            dict.Add(GRANT_TYPE, REFRESH_TOKEN);
+            dict[GRANT_TYPE] = REFRESH_TOKEN;
 
             if (_scope != null)
             {
@@ -284,4 +363,26 @@ public long ExpiresIn
             get; set;
         }
     }
+
+    /// <summary>
+    /// Minimal version of the properties of the discovery endpoint.
+    /// </summary>
+    internal class OpenIDConnectDiscovery
+    {
+        public OpenIDConnectDiscovery()
+        {
+            TokenEndpoint = string.Empty;
+        }
+
+        public OpenIDConnectDiscovery(string tokenEndpoint)
+        {
+            TokenEndpoint = tokenEndpoint;
+        }
+
+        [JsonPropertyName("token_endpoint")]
+        public string TokenEndpoint
+        {
+            get; set;
+        }
+    }
 }

projects/RabbitMQ.Client.OAuth2/PublicAPI.Shipped.txt

@@ -7,8 +7,7 @@ RabbitMQ.Client.OAuth2.IToken.HasExpired.get -> bool
 RabbitMQ.Client.OAuth2.IToken.RefreshToken.get -> string
 RabbitMQ.Client.OAuth2.OAuth2ClientBuilder
 RabbitMQ.Client.OAuth2.OAuth2ClientBuilder.AddRequestParameter(string param, string paramValue) -> RabbitMQ.Client.OAuth2.OAuth2ClientBuilder
-RabbitMQ.Client.OAuth2.OAuth2ClientBuilder.Build() -> RabbitMQ.Client.OAuth2.IOAuth2Client
-RabbitMQ.Client.OAuth2.OAuth2ClientBuilder.OAuth2ClientBuilder(string clientId, string clientSecret, System.Uri tokenEndpoint) -> void
+RabbitMQ.Client.OAuth2.OAuth2ClientBuilder.OAuth2ClientBuilder(string! clientId, string! clientSecret, System.Uri? tokenEndpoint = null, System.Uri? issuer = null) -> void
 RabbitMQ.Client.OAuth2.OAuth2ClientBuilder.SetScope(string scope) -> RabbitMQ.Client.OAuth2.OAuth2ClientBuilder
 RabbitMQ.Client.OAuth2.OAuth2ClientCredentialsProvider
 RabbitMQ.Client.OAuth2.OAuth2ClientCredentialsProvider.Name.get -> string

projects/RabbitMQ.Client.OAuth2/PublicAPI.Unshipped.txt

@@ -10,6 +10,7 @@ RabbitMQ.Client.OAuth2.CredentialsRefresherEventSource.Stopped(string! name) ->
 RabbitMQ.Client.OAuth2.IOAuth2Client.RefreshTokenAsync(RabbitMQ.Client.OAuth2.IToken! token, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<RabbitMQ.Client.OAuth2.IToken!>!
 RabbitMQ.Client.OAuth2.IOAuth2Client.RequestTokenAsync(System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<RabbitMQ.Client.OAuth2.IToken!>!
 RabbitMQ.Client.OAuth2.NotifyCredentialsRefreshedAsync
+RabbitMQ.Client.OAuth2.OAuth2ClientBuilder.BuildAsync(System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.ValueTask<RabbitMQ.Client.OAuth2.IOAuth2Client!>
 RabbitMQ.Client.OAuth2.OAuth2ClientBuilder.SetHttpClientHandler(System.Net.Http.HttpClientHandler! handler) -> RabbitMQ.Client.OAuth2.OAuth2ClientBuilder!
 RabbitMQ.Client.OAuth2.OAuth2ClientCredentialsProvider.Dispose() -> void
 RabbitMQ.Client.OAuth2.OAuth2ClientCredentialsProvider.GetCredentialsAsync(System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<RabbitMQ.Client.Credentials!>!