1 files changed, 104 insertions, 0 deletions
diff --git a/src/DotNetOpenAuth.OAuth2.AuthorizationServer/OAuth2/ChannelElements/MessageValidationBindingElement.cs b/src/DotNetOpenAuth.OAuth2.AuthorizationServer/OAuth2/ChannelElements/MessageValidationBindingElement.cs
new file mode 100644
index 0000000..46a3de2
--- /dev/null
+++ b/src/DotNetOpenAuth.OAuth2.AuthorizationServer/OAuth2/ChannelElements/MessageValidationBindingElement.cs
@@ -0,0 +1,104 @@
+//-----------------------------------------------------------------------
+// <copyright file="MessageValidationBindingElement.cs" company="Outercurve Foundation">
+//     Copyright (c) Outercurve Foundation. All rights reserved.
+// </copyright>
+//-----------------------------------------------------------------------
+
+namespace DotNetOpenAuth.OAuth2.ChannelElements {
+	using System;
+	using System.Collections.Generic;
+	using System.Diagnostics.Contracts;
+	using System.Linq;
+	using System.Text;
+	using DotNetOpenAuth.OAuth2.Messages;
+	using Messaging;
+
+	/// <summary>
+	/// A guard for all messages to or from an Authorization Server to ensure that they are well formed,
+	/// have valid secrets, callback URIs, etc.
+	/// </summary>
+	internal class MessageValidationBindingElement : AuthServerBindingElementBase {
+		/// <summary>
+		/// Gets the protection commonly offered (if any) by this binding element.
+		/// </summary>
+		/// <remarks>
+		/// This value is used to assist in sorting binding elements in the channel stack.
+		/// </remarks>
+		public override MessageProtections Protection {
+			get { return MessageProtections.None; }
+		}
+
+		/// <summary>
+		/// Prepares a message for sending based on the rules of this channel binding element.
+		/// </summary>
+		/// <param name="message">The message to prepare for sending.</param>
+		/// <returns>
+		/// The protections (if any) that this binding element applied to the message.
+		/// Null if this binding element did not even apply to this binding element.
+		/// </returns>
+		/// <remarks>
+		/// Implementations that provide message protection must honor the
+		/// <see cref="MessagePartAttribute.RequiredProtection"/> properties where applicable.
+		/// </remarks>
+		public override MessageProtections? ProcessOutgoingMessage(IProtocolMessage message) {
+			var accessTokenResponse = message as AccessTokenSuccessResponse;
+			if (accessTokenResponse != null) {
+				var directResponseMessage = (IDirectResponseProtocolMessage)accessTokenResponse;
+				var accessTokenRequest = (AccessTokenRequestBase)directResponseMessage.OriginatingRequest;
+				ErrorUtilities.VerifyProtocol(accessTokenRequest.GrantType != GrantType.ClientCredentials || accessTokenResponse.RefreshToken == null, OAuthStrings.NoGrantNoRefreshToken);
+			}
+
+			return null;
+		}
+
+		/// <summary>
+		/// Performs any transformation on an incoming message that may be necessary and/or
+		/// validates an incoming message based on the rules of this channel binding element.
+		/// </summary>
+		/// <param name="message">The incoming message to process.</param>
+		/// <returns>
+		/// The protections (if any) that this binding element applied to the message.
+		/// Null if this binding element did not even apply to this binding element.
+		/// </returns>
+		/// <exception cref="ProtocolException">
+		/// Thrown when the binding element rules indicate that this message is invalid and should
+		/// NOT be processed.
+		/// </exception>
+		/// <remarks>
+		/// Implementations that provide message protection must honor the
+		/// <see cref="MessagePartAttribute.RequiredProtection"/> properties where applicable.
+		/// </remarks>
+		public override MessageProtections? ProcessIncomingMessage(IProtocolMessage message) {
+			bool applied = false;
+
+			// Check that the client secret is correct for client authenticated messages.
+			var authenticatedClientRequest = message as AuthenticatedClientRequestBase;
+			if (authenticatedClientRequest != null) {
+				var client = this.AuthorizationServer.GetClientOrThrow(authenticatedClientRequest.ClientIdentifier);
+				string secret = client.Secret;
+				ErrorUtilities.VerifyProtocol(!string.IsNullOrEmpty(secret), Protocol.unauthorized_client); // an empty secret is not allowed for client authenticated calls.
+				ErrorUtilities.VerifyProtocol(MessagingUtilities.EqualsConstantTime(secret, authenticatedClientRequest.ClientSecret), Protocol.incorrect_client_credentials);
+				applied = true;
+			}
+
+			// Check that authorization requests come with an acceptable callback URI.
+			var authorizationRequest = message as EndUserAuthorizationRequest;
+			if (authorizationRequest != null) {
+				var client = this.AuthorizationServer.GetClientOrThrow(authorizationRequest.ClientIdentifier);
+				ErrorUtilities.VerifyProtocol(authorizationRequest.Callback == null || client.IsCallbackAllowed(authorizationRequest.Callback), OAuthStrings.ClientCallbackDisallowed, authorizationRequest.Callback);
+				ErrorUtilities.VerifyProtocol(authorizationRequest.Callback != null || client.DefaultCallback != null, OAuthStrings.NoCallback);
+				applied = true;
+			}
+
+			// Check that the callback URI in a direct message from the client matches the one in the indirect message received earlier.
+			var request = message as AccessTokenAuthorizationCodeRequestAS;
+			if (request != null) {
+				IAuthorizationCodeCarryingRequest tokenRequest = request;
+				tokenRequest.AuthorizationDescription.VerifyCallback(request.Callback);
+				applied = true;
+			}
+
+			return applied ? (MessageProtections?)MessageProtections.None : null;
+		}
+	}
+}