AnonymousIdentifierProvider.cs

namespace OpenIdProviderMvc.Code {
	using System;
	using System.Web.Security;
	using DotNetOpenAuth.OpenId;
	using DotNetOpenAuth.OpenId.Provider;
	using OpenIdProviderMvc.Models;

	internal class AnonymousIdentifierProvider : PrivatePersonalIdentifierProviderBase {
		/// <summary>
		/// Initializes a new instance of the <see cref="AnonymousIdentifierProvider"/> class.
		/// </summary>
		internal AnonymousIdentifierProvider()
			: base(Util.GetAppPathRootedUri("anon?id=")) {
		}

		/// <summary>
		/// Gets the salt to use for generating an anonymous identifier for a given OP local identifier.
		/// </summary>
		/// <param name="localIdentifier">The OP local identifier.</param>
		/// <returns>The salt to use in the hash.</returns>
		/// <remarks>
		/// It is important that this method always return the same value for a given
		/// <paramref name="localIdentifier"/>.
		/// New salts can be generated for local identifiers without previously assigned salt
		/// values by calling <see cref="CreateSalt"/> or by a custom method.
		/// </remarks>
		protected override byte[] GetHashSaltForLocalIdentifier(Identifier localIdentifier) {
			// This is just a sample with no database... a real web app MUST return 
			// a reasonable salt here and have that salt be persistent for each user.
			var membership = (ReadOnlyXmlMembershipProvider)Membership.Provider;
			string username = User.GetUserFromClaimedIdentifier(new Uri(localIdentifier));
			string salt = membership.GetSalt(username);
			return Convert.FromBase64String(salt);

			// If users were encountered without a salt, one could be generated like this,
			// and would also need to be saved to the user's account.
			//// var newSalt = AnonymousIdentifierProviderBase.GetNewSalt(5);
			//// user.Salt = newSalt;
			//// return newSalt;
		}
	}
}