Adding a method for exchanging 2FA token to the SAML response (#44)

* .NET Framework 471 architecture added. Version bump to 1.2.3

* renaming the audience for saml response parameter

* fixing the wrong casing

* version bump

* samlResponse added to the TokenResponse

* bumping version to 1.3

* version update, method name update

* fixing the linter formatting error

DuoUniversal.Tests/TestExchangeCode.cs

@@ -31,6 +31,15 @@ public async Task TestSuccess()
             Assert.AreEqual(idToken.Username, USERNAME);
         }
 
+        [Test]
+        public async Task TestSamlResponseSuccess()
+        {
+            string goodResponse = GoodApiResponseWithSamlResponse();
+            var client = MakeClient(new HttpResponder(HttpStatusCode.OK, new StringContent(goodResponse)));
+            string samlResponse = await client.ExchangeAuthorizationCodeForSamlResponse(CODE, USERNAME);
+            Assert.NotNull(samlResponse);
+        }
+
         [Test]
         [TestCase(HttpStatusCode.MovedPermanently)] // 301
         [TestCase(HttpStatusCode.BadRequest)] // 400
@@ -56,12 +65,21 @@ public void TestHttpException()
         [TestCase("!@#user$%^name*&(")]
         public void TestUsernameMismatch(string username)
         {
-            // Will have the USERNAME specified above
+            // Will have the USERNAME specified in the parent class
             string goodResponse = GoodApiResponse();
             var client = MakeClient(new HttpResponder(HttpStatusCode.OK, new StringContent(goodResponse)));
             Assert.ThrowsAsync<DuoException>(async () => await client.ExchangeAuthorizationCodeFor2faResult(CODE, username));
         }
 
+        [Test]
+        [TestCase("not username")]
+        public void TestUsernameMismatchSamlResponseFailure(string username)
+        {
+            string goodResponse = GoodApiResponseWithSamlResponse();
+            var client = MakeClient(new HttpResponder(HttpStatusCode.OK, new StringContent(goodResponse)));
+            Assert.ThrowsAsync<DuoException>(async () => await client.ExchangeAuthorizationCodeForSamlResponse(CODE, username));
+        }
+
         private static string GoodApiResponse()
         {
             var responseValues = new Dictionary<string, string>
@@ -73,5 +91,18 @@ private static string GoodApiResponse()
             };
             return JsonSerializer.Serialize(responseValues);
         }
+
+        private static string GoodApiResponseWithSamlResponse()
+        {
+            var responseValues = new Dictionary<string, string>
+            {
+                {"access_token", "access token"},
+                {"expires_in", "1"},
+                {"id_token", CreateTokenJwt()},
+                {"token_type", "Bearer"},
+                {"saml_response", "saml_response"}
+            };
+            return JsonSerializer.Serialize(responseValues);
+        }
     }
 }

DuoUniversal/Client.cs

@@ -95,14 +95,12 @@ public string GenerateAuthUri(string username, string state)
         }
 
         /// <summary>
-        /// Send the authorization code provided by Duo back to Duo in exchange for an Id Token authenticating the user and
-        /// providing details about the authentication.
+        /// Send the authorization code provided by Duo back to Duo in exchange for a full Duo response.
         /// Will raise a DuoException if the username does not match the Id Token.
         /// </summary>
         /// <param name="duoCode">The one-time use code issued by Duo</param>
-        /// <param name="username">The username expected to have authenticated with Duo</param>
-        /// <returns>An IdToken authenticating the user and describing the authentication</returns>
-        public async Task<IdToken> ExchangeAuthorizationCodeFor2faResult(string duoCode, string username)
+        /// <returns>A TokenResponse authenticating the user and describing the authentication</returns>
+        private async Task<TokenResponse> ExchangeAuthorizationCodeResponse(string duoCode)
         {
             string tokenEndpoint = CustomizeApiUri(TOKEN_ENDPOINT);
 
@@ -128,9 +126,21 @@ public async Task<IdToken> ExchangeAuthorizationCodeFor2faResult(string duoCode,
                 throw new DuoException("Error exchanging the code for a 2fa token", e);
             }
 
+            return tokenResponse;
+        }
+
+        /// <summary>
+        /// Extracts and validates the Id Token from the response.
+        /// Will raise a DuoException if the username does not match the Id Token.
+        /// </summary>
+        /// <param name="duoCode">The one-time use code issued by Duo</param>
+        /// <returns>A TokenResponse authenticating the user and describing the authentication</returns>
+        private IdToken ValidateIdTokenFromResponse(TokenResponse tokenResponse, string username)
+        {
             IdToken idToken;
             try
             {
+                string tokenEndpoint = CustomizeApiUri(TOKEN_ENDPOINT);
                 JwtUtils.ValidateJwt(tokenResponse.IdToken, ClientId, ClientSecret, tokenEndpoint);
                 idToken = Utils.DecodeToken(tokenResponse.IdToken);
             }
@@ -148,6 +158,48 @@ public async Task<IdToken> ExchangeAuthorizationCodeFor2faResult(string duoCode,
         }
 
 
+        /// <summary>
+        /// Send the authorization code provided by Duo back to Duo in exchange for an Id Token authenticating the user and
+        /// providing details about the authentication.
+        /// Will raise a DuoException if the username does not match the Id Token.
+        /// </summary>
+        /// <param name="duoCode">The one-time use code issued by Duo</param>
+        /// <param name="username">The username expected to have authenticated with Duo</param>
+        /// <returns>An IdToken authenticating the user and describing the authentication</returns>
+        public async Task<IdToken> ExchangeAuthorizationCodeFor2faResult(string duoCode, string username)
+        {
+            TokenResponse tokenResponse = await ExchangeAuthorizationCodeResponse(duoCode);
+            return ValidateIdTokenFromResponse(tokenResponse, username);
+
+        }
+
+        /// <summary>
+        /// Send the authorization code provided by Duo back to Duo in exchange for an SAML response, used for some integrations.
+        /// Will raise a DuoException if the username does not match the Id Token.
+        /// </summary>
+        /// <param name="duoCode">The one-time use code issued by Duo</param>
+        /// <param name="username">The username expected to have authenticated with Duo</param>
+        /// <returns>A string authenticating the user and containing the saml response</returns>
+        public async Task<string> ExchangeAuthorizationCodeForSamlResponse(string duoCode, string username)
+        {
+            string samlResponse;
+            TokenResponse tokenResponse = await ExchangeAuthorizationCodeResponse(duoCode);
+
+            try
+            {
+                // Calling this method to validate the token, before getting the samlResponse value
+                ValidateIdTokenFromResponse(tokenResponse, username);
+                samlResponse = tokenResponse.SamlResponse;
+            }
+            catch (Exception e)
+            {
+                throw new DuoException("Error while retrieveing saml response", e);
+            }
+
+            return samlResponse;
+        }
+
+
         /// <summary>
         /// Customize a URI template based on the Duo API Host value
         /// </summary>

DuoUniversal/DuoUniversal.csproj

@@ -6,7 +6,7 @@
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0;net471</TargetFrameworks>
     <PackageId>DuoUniversal</PackageId>
-    <Version>1.2.5</Version>
+    <Version>1.2.6</Version>
     <Authors>Duo Security</Authors>
     <Company>Duo Security</Company>
     <Copyright>Cisco Systems, Inc. and/or its affiliates</Copyright>

DuoUniversal/Models.cs

@@ -38,6 +38,8 @@ internal class TokenResponse
         public string TokenType { get; set; }
         [JsonPropertyName("expires_in")]
         public int ExpiresIn { get; set; }
+        [JsonPropertyName("saml_response")]
+        public string SamlResponse { get; set; }
     }
 
     public class IdToken