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[dotnetoauth.git] / src / DotNetOpenAuth / OpenId / ChannelElements / SigningBindingElement.cs

//-----------------------------------------------------------------------
// <copyright file="SigningBindingElement.cs" company="Andrew Arnott">
//     Copyright (c) Andrew Arnott. All rights reserved.
// </copyright>
//-----------------------------------------------------------------------

namespace DotNetOpenAuth.OpenId.ChannelElements {
        using System;
        using System.Collections.Generic;
        using System.Diagnostics;
        using System.Linq;
        using System.Net.Security;
        using DotNetOpenAuth.Loggers;
        using DotNetOpenAuth.Messaging;
        using DotNetOpenAuth.Messaging.Bindings;
        using DotNetOpenAuth.Messaging.Reflection;
        using DotNetOpenAuth.OpenId.Messages;
        using DotNetOpenAuth.OpenId.Provider;
        using DotNetOpenAuth.OpenId.RelyingParty;

        /// <summary>
        /// Signs and verifies authentication assertions.
        /// </summary>
        internal class SigningBindingElement : IChannelBindingElement {
                /// <summary>
                /// The association store used by Relying Parties to look up the secrets needed for signing.
                /// </summary>
                private readonly IAssociationStore<Uri> rpAssociations;

                /// <summary>
                /// The association store used by Providers to look up the secrets needed for signing.
                /// </summary>
                private readonly IAssociationStore<AssociationRelyingPartyType> opAssociations;

                /// <summary>
                /// The security settings at the Provider.
                /// Only defined when this element is instantiated to service a Provider.
                /// </summary>
                private readonly ProviderSecuritySettings opSecuritySettings;

                /// <summary>
                /// A logger specifically used for logging verbose text on everything about the signing process.
                /// </summary>
                private static ILog signingLogger = Logger.Create(typeof(SigningBindingElement));

                /// <summary>
                /// Initializes a new instance of the SigningBindingElement class for use by a Relying Party.
                /// </summary>
                /// <param name="associationStore">The association store used to look up the secrets needed for signing.  May be null for dumb Relying Parties.</param>
                internal SigningBindingElement(IAssociationStore<Uri> associationStore) {
                        this.rpAssociations = associationStore;
                }

                /// <summary>
                /// Initializes a new instance of the SigningBindingElement class for use by a Provider.
                /// </summary>
                /// <param name="associationStore">The association store used to look up the secrets needed for signing.</param>
                /// <param name="securitySettings">The security settings.</param>
                internal SigningBindingElement(IAssociationStore<AssociationRelyingPartyType> associationStore, ProviderSecuritySettings securitySettings) {
                        ErrorUtilities.VerifyArgumentNotNull(associationStore, "associationStore");
                        ErrorUtilities.VerifyArgumentNotNull(securitySettings, "securitySettings");

                        this.opAssociations = associationStore;
                        this.opSecuritySettings = securitySettings;
                }

                #region IChannelBindingElement Properties

                /// <summary>
                /// Gets the protection offered (if any) by this binding element.
                /// </summary>
                /// <value><see cref="MessageProtections.TamperProtection"/></value>
                public MessageProtections Protection {
                        get { return MessageProtections.TamperProtection; }
                }

                /// <summary>
                /// Gets or sets the channel that this binding element belongs to.
                /// </summary>
                public Channel Channel { get; set; }

                #endregion

                /// <summary>
                /// Gets a value indicating whether this binding element is on a Provider channel.
                /// </summary>
                private bool IsOnProvider {
                        get { return this.opAssociations != null; }
                }

                #region IChannelBindingElement Methods

                /// <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>
                /// True if the <paramref name="message"/> applied to this binding element
                /// and the operation was successful.  False otherwise.
                /// </returns>
                public bool PrepareMessageForSending(IProtocolMessage message) {
                        var signedMessage = message as ITamperResistantOpenIdMessage;
                        if (signedMessage != null) {
                                Logger.DebugFormat("Signing {0} message.", message.GetType().Name);
                                Association association = this.GetAssociation(signedMessage);
                                signedMessage.AssociationHandle = association.Handle;
                                signedMessage.SignedParameterOrder = this.GetSignedParameterOrder(signedMessage);
                                signedMessage.Signature = this.GetSignature(signedMessage, association);
                                return true;
                        }

                        return false;
                }

                /// <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>
                /// True if the <paramref name="message"/> applied to this binding element
                /// and the operation was successful.  False if the operation did not apply to this message.
                /// </returns>
                /// <exception cref="ProtocolException">
                /// Thrown when the binding element rules indicate that this message is invalid and should
                /// NOT be processed.
                /// </exception>
                public bool PrepareMessageForReceiving(IProtocolMessage message) {
                        var signedMessage = message as ITamperResistantOpenIdMessage;
                        if (signedMessage != null) {
                                Logger.DebugFormat("Verifying incoming {0} message signature of: {1}", message.GetType().Name, signedMessage.Signature);

                                EnsureParametersRequiringSignatureAreSigned(signedMessage);

                                Association association = this.GetSpecificAssociation(signedMessage);
                                if (association != null) {
                                        string signature = this.GetSignature(signedMessage, association);
                                        if (!string.Equals(signedMessage.Signature, signature, StringComparison.Ordinal)) {
                                                Logger.Error("Signature verification failed.");
                                                throw new InvalidSignatureException(message);
                                        }
                                } else {
                                        ErrorUtilities.VerifyInternal(this.Channel != null, "Cannot verify private association signature because we don't have a channel.");

                                        // We did not recognize the association the provider used to sign the message.
                                        // Ask the provider to check the signature then.
                                        var indirectSignedResponse = (IndirectSignedResponse)signedMessage;
                                        var checkSignatureRequest = new CheckAuthenticationRequest(indirectSignedResponse);
                                        var checkSignatureResponse = this.Channel.Request<CheckAuthenticationResponse>(checkSignatureRequest);
                                        if (!checkSignatureResponse.IsValid) {
                                                Logger.Error("Provider reports signature verification failed.");
                                                throw new InvalidSignatureException(message);
                                        }

                                        // If the OP confirms that a handle should be invalidated as well, do that.
                                        if (!string.IsNullOrEmpty(checkSignatureResponse.InvalidateHandle)) {
                                                if (this.rpAssociations != null) {
                                                        this.rpAssociations.RemoveAssociation(indirectSignedResponse.ProviderEndpoint, checkSignatureResponse.InvalidateHandle);
                                                }
                                        }
                                }

                                return true;
                        }

                        return false;
                }

                #endregion

                /// <summary>
                /// Ensures that all message parameters that must be signed are in fact included
                /// in the signature.
                /// </summary>
                /// <param name="signedMessage">The signed message.</param>
                private static void EnsureParametersRequiringSignatureAreSigned(ITamperResistantOpenIdMessage signedMessage) {
                        // Verify that the signed parameter order includes the mandated fields.
                        // We do this in such a way that derived classes that add mandated fields automatically
                        // get included in the list of checked parameters.
                        Protocol protocol = Protocol.Lookup(signedMessage.Version);
                        var partsRequiringProtection = from part in MessageDescription.Get(signedMessage.GetType(), signedMessage.Version).Mapping.Values
                                                       where part.RequiredProtection != ProtectionLevel.None
                                                       select part.Name;
                        ErrorUtilities.VerifyInternal(partsRequiringProtection.All(name => name.StartsWith(protocol.openid.Prefix, StringComparison.Ordinal)), "Signing only works when the parameters start with the 'openid.' prefix.");
                        string[] signedParts = signedMessage.SignedParameterOrder.Split(',');
                        var unsignedParts = from partName in partsRequiringProtection
                                            where !signedParts.Contains(partName.Substring(protocol.openid.Prefix.Length))
                                            select partName;
                        ErrorUtilities.VerifyProtocol(!unsignedParts.Any(), OpenIdStrings.SignatureDoesNotIncludeMandatoryParts, string.Join(", ", unsignedParts.ToArray()));
                }

                /// <summary>
                /// Gets the value to use for the openid.signed parameter.
                /// </summary>
                /// <param name="signedMessage">The signable message.</param>
                /// <returns>
                /// A comma-delimited list of parameter names, omitting the 'openid.' prefix, that determines
                /// the inclusion and order of message parts that will be signed.
                /// </returns>
                private string GetSignedParameterOrder(ITamperResistantOpenIdMessage signedMessage) {
                        ErrorUtilities.VerifyArgumentNotNull(signedMessage, "signedMessage");

                        Protocol protocol = Protocol.Lookup(signedMessage.Version);

                        MessageDescription description = MessageDescription.Get(signedMessage.GetType(), signedMessage.Version);
                        var signedParts = from part in description.Mapping.Values
                                          where (part.RequiredProtection & System.Net.Security.ProtectionLevel.Sign) != 0
                                                && part.GetValue(signedMessage) != null
                                          select part.Name;
                        string prefix = Protocol.V20.openid.Prefix;
                        ErrorUtilities.VerifyInternal(signedParts.All(name => name.StartsWith(prefix, StringComparison.Ordinal)), "All signed message parts must start with 'openid.'.");

                        if (this.opSecuritySettings.SignOutgoingExtensions) {
                                // Tack on any ExtraData parameters that start with 'openid.'.
                                List<string> extraSignedParameters = new List<string>(signedMessage.ExtraData.Count);
                                foreach (string key in signedMessage.ExtraData.Keys) {
                                        if (key.StartsWith(protocol.openid.Prefix, StringComparison.Ordinal)) {
                                                extraSignedParameters.Add(key);
                                        } else {
                                                Logger.DebugFormat("The extra parameter '{0}' will not be signed because it does not start with 'openid.'.", key);
                                        }
                                }
                                signedParts = signedParts.Concat(extraSignedParameters);
                        }

                        int skipLength = prefix.Length;
                        string signedFields = string.Join(",", signedParts.Select(name => name.Substring(skipLength)).ToArray());
                        return signedFields;
                }

                /// <summary>
                /// Calculates the signature for a given message.
                /// </summary>
                /// <param name="signedMessage">The message to sign or verify.</param>
                /// <param name="association">The association to use to sign the message.</param>
                /// <returns>The calculated signature of the method.</returns>
                private string GetSignature(ITamperResistantOpenIdMessage signedMessage, Association association) {
                        ErrorUtilities.VerifyArgumentNotNull(signedMessage, "signedMessage");
                        ErrorUtilities.VerifyNonZeroLength(signedMessage.SignedParameterOrder, "signedMessage.SignedParameterOrder");
                        ErrorUtilities.VerifyArgumentNotNull(association, "association");

                        // Prepare the parts to sign, taking care to replace an openid.mode value
                        // of check_authentication with its original id_res so the signature matches.
                        Protocol protocol = Protocol.Lookup(signedMessage.Version);
                        MessageDictionary dictionary = new MessageDictionary(signedMessage);
                        var parametersToSign = from name in signedMessage.SignedParameterOrder.Split(',')
                                               let prefixedName = Protocol.V20.openid.Prefix + name
                                               select new KeyValuePair<string, string>(prefixedName, dictionary[prefixedName]);

                        byte[] dataToSign = KeyValueFormEncoding.GetBytes(parametersToSign);
                        string signature = Convert.ToBase64String(association.Sign(dataToSign));

                        if (signingLogger.IsDebugEnabled) {
                                signingLogger.DebugFormat(
                                        "Signing these message parts: {0}{1}{0}Base64 representation of signed data: {2}{0}Signature: {3}",
                                        Environment.NewLine,
                                        parametersToSign.ToStringDeferred(),
                                        Convert.ToBase64String(dataToSign),
                                        signature);
                        }

                        return signature;
                }

                /// <summary>
                /// Gets the association to use to sign or verify a message.
                /// </summary>
                /// <param name="signedMessage">The message to sign or verify.</param>
                /// <returns>The association to use to sign or verify the message.</returns>
                private Association GetAssociation(ITamperResistantOpenIdMessage signedMessage) {
                        if (this.IsOnProvider) {
                                // We're on a Provider to either sign (smart/dumb) or verify a dumb signature.
                                return this.GetSpecificAssociation(signedMessage) ?? this.GetDumbAssociationForSigning();
                        } else {
                                // We're on a Relying Party verifying a signature.
                                IDirectedProtocolMessage directedMessage = (IDirectedProtocolMessage)signedMessage;
                                if (this.rpAssociations != null) {
                                        return this.rpAssociations.GetAssociation(directedMessage.Recipient, signedMessage.AssociationHandle);
                                } else {
                                        return null;
                                }
                        }
                }

                /// <summary>
                /// Gets a specific association referenced in a given message's association handle.
                /// </summary>
                /// <param name="signedMessage">The signed message whose association handle should be used to lookup the association to return.</param>
                /// <returns>The referenced association; or <c>null</c> if such an association cannot be found.</returns>
                /// <remarks>
                /// If the association handle set in the message does not match any valid association,
                /// the association handle property is cleared, and the 
                /// <see cref="ITamperResistantOpenIdMessage.InvalidateHandle"/> property is set to the
                /// handle that could not be found.
                /// </remarks>
                private Association GetSpecificAssociation(ITamperResistantOpenIdMessage signedMessage) {
                        Association association = null;

                        if (!string.IsNullOrEmpty(signedMessage.AssociationHandle)) {
                                if (this.IsOnProvider) {
                                        // Since we have an association handle, we're either signing with a smart association,
                                        // or verifying a dumb one.
                                        bool signing = string.IsNullOrEmpty(signedMessage.Signature);
                                        ErrorUtilities.VerifyInternal(signing == (signedMessage is PositiveAssertionResponse), "Ooops... somehow we think we're signing a message that isn't a positive assertion!");
                                        AssociationRelyingPartyType type = signing ? AssociationRelyingPartyType.Smart : AssociationRelyingPartyType.Dumb;
                                        association = this.opAssociations.GetAssociation(type, signedMessage.AssociationHandle);
                                        if (association == null) {
                                                // There was no valid association with the requested handle.
                                                // Let's tell the RP to forget about that association.
                                                signedMessage.InvalidateHandle = signedMessage.AssociationHandle;
                                                signedMessage.AssociationHandle = null;
                                        }
                                } else if (this.rpAssociations != null) { // if on a smart RP
                                        Uri providerEndpoint = ((IndirectSignedResponse)signedMessage).ProviderEndpoint;
                                        association = this.rpAssociations.GetAssociation(providerEndpoint, signedMessage.AssociationHandle);
                                }
                        }

                        return association;
                }

                /// <summary>
                /// Gets a private Provider association used for signing messages in "dumb" mode.
                /// </summary>
                /// <returns>An existing or newly created association.</returns>
                private Association GetDumbAssociationForSigning() {
                        // If no assoc_handle was given or it was invalid, the only thing 
                        // left to do is sign a message using a 'dumb' mode association.
                        Protocol protocol = Protocol.Default;
                        Association association = this.opAssociations.GetAssociation(AssociationRelyingPartyType.Dumb);
                        if (association == null) {
                                association = HmacShaAssociation.Create(protocol, protocol.Args.SignatureAlgorithm.HMAC_SHA256, AssociationRelyingPartyType.Dumb, this.opSecuritySettings);
                                this.opAssociations.StoreAssociation(AssociationRelyingPartyType.Dumb, association);
                        }

                        return association;
                }
        }
}