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//-----------------------------------------------------------------------
// <copyright file="AssociateDiffieHellmanResponse.cs" company="Andrew Arnott">
// Copyright (c) Andrew Arnott. All rights reserved.
// </copyright>
//-----------------------------------------------------------------------
namespace DotNetOpenAuth.OpenId.Messages {
using System;
using System.Diagnostics.Contracts;
using System.Security.Cryptography;
using DotNetOpenAuth.Messaging;
using DotNetOpenAuth.Messaging.Reflection;
using DotNetOpenAuth.OpenId.Provider;
using Org.Mentalis.Security.Cryptography;
/// <summary>
/// The successful Diffie-Hellman association response message.
/// </summary>
/// <remarks>
/// Association response messages are described in OpenID 2.0 section 8.2. This type covers section 8.2.3.
/// </remarks>
internal class AssociateDiffieHellmanResponse : AssociateSuccessfulResponse {
/// <summary>
/// Initializes a new instance of the <see cref="AssociateDiffieHellmanResponse"/> class.
/// </summary>
/// <param name="responseVersion">The OpenID version of the response message.</param>
/// <param name="originatingRequest">The originating request.</param>
internal AssociateDiffieHellmanResponse(Version responseVersion, AssociateDiffieHellmanRequest originatingRequest)
: base(responseVersion, originatingRequest) {
}
/// <summary>
/// Gets or sets the Provider's Diffie-Hellman public key.
/// </summary>
/// <value>btwoc(g ^ xb mod p)</value>
[MessagePart("dh_server_public", IsRequired = true, AllowEmpty = false)]
internal byte[] DiffieHellmanServerPublic { get; set; }
/// <summary>
/// Gets or sets the MAC key (shared secret), encrypted with the secret Diffie-Hellman value.
/// </summary>
/// <value>H(btwoc(g ^ (xa * xb) mod p)) XOR MAC key. H is either "SHA1" or "SHA256" depending on the session type. </value>
[MessagePart("enc_mac_key", IsRequired = true, AllowEmpty = false)]
internal byte[] EncodedMacKey { get; set; }
/// <summary>
/// Creates the association at relying party side after the association response has been received.
/// </summary>
/// <param name="request">The original association request that was already sent and responded to.</param>
/// <returns>The newly created association.</returns>
/// <remarks>
/// The resulting association is <i>not</i> added to the association store and must be done by the caller.
/// </remarks>
protected override Association CreateAssociationAtRelyingParty(AssociateRequest request) {
var diffieHellmanRequest = request as AssociateDiffieHellmanRequest;
ErrorUtilities.VerifyArgument(diffieHellmanRequest != null, OpenIdStrings.DiffieHellmanAssociationRequired);
HashAlgorithm hasher = DiffieHellmanUtilities.Lookup(Protocol, this.SessionType);
byte[] associationSecret = DiffieHellmanUtilities.SHAHashXorSecret(hasher, diffieHellmanRequest.Algorithm, this.DiffieHellmanServerPublic, this.EncodedMacKey);
Association association = HmacShaAssociation.Create(Protocol, this.AssociationType, this.AssociationHandle, associationSecret, TimeSpan.FromSeconds(this.ExpiresIn));
return association;
}
/// <summary>
/// Creates the association at the provider side after the association request has been received.
/// </summary>
/// <param name="request">The association request.</param>
/// <param name="associationStore">The OpenID Provider's association store or handle encoder.</param>
/// <param name="securitySettings">The security settings of the Provider.</param>
/// <returns>
/// The newly created association.
/// </returns>
/// <remarks>
/// The response message is updated to include the details of the created association by this method,
/// but the resulting association is <i>not</i> added to the association store and must be done by the caller.
/// </remarks>
protected override Association CreateAssociationAtProvider(AssociateRequest request, IProviderAssociationStore associationStore, ProviderSecuritySettings securitySettings) {
var diffieHellmanRequest = request as AssociateDiffieHellmanRequest;
ErrorUtilities.VerifyInternal(diffieHellmanRequest != null, "Expected a DH request type.");
this.SessionType = this.SessionType ?? request.SessionType;
// Go ahead and create the association first, complete with its secret that we're about to share.
Association association = HmacShaAssociation.Create(this.Protocol, this.AssociationType, AssociationRelyingPartyType.Smart, associationStore, securitySettings);
// We now need to securely communicate the secret to the relying party using Diffie-Hellman.
// We do this by performing a DH algorithm on the secret and setting a couple of properties
// that will be transmitted to the Relying Party. The RP will perform an inverse operation
// using its part of a DH secret in order to decrypt the shared secret we just invented
// above when we created the association.
using (DiffieHellman dh = new DiffieHellmanManaged(
diffieHellmanRequest.DiffieHellmanModulus ?? AssociateDiffieHellmanRequest.DefaultMod,
diffieHellmanRequest.DiffieHellmanGen ?? AssociateDiffieHellmanRequest.DefaultGen,
AssociateDiffieHellmanRequest.DefaultX)) {
HashAlgorithm hasher = DiffieHellmanUtilities.Lookup(this.Protocol, this.SessionType);
this.DiffieHellmanServerPublic = DiffieHellmanUtilities.EnsurePositive(dh.CreateKeyExchange());
this.EncodedMacKey = DiffieHellmanUtilities.SHAHashXorSecret(hasher, dh, diffieHellmanRequest.DiffieHellmanConsumerPublic, association.SecretKey);
}
return association;
}
}
}
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