1 files changed, 95 insertions, 0 deletions
diff --git a/src/DotNetOpenAuth.OpenId/OpenId/SecuritySettings.cs b/src/DotNetOpenAuth.OpenId/OpenId/SecuritySettings.cs
new file mode 100644
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+++ b/src/DotNetOpenAuth.OpenId/OpenId/SecuritySettings.cs
@@ -0,0 +1,95 @@
+//-----------------------------------------------------------------------
+// <copyright file="SecuritySettings.cs" company="Andrew Arnott">
+//     Copyright (c) Andrew Arnott. All rights reserved.
+// </copyright>
+//-----------------------------------------------------------------------
+
+namespace DotNetOpenAuth.OpenId {
+	using System;
+	using System.Collections.Generic;
+	using System.Collections.Specialized;
+	using System.Diagnostics.Contracts;
+	using DotNetOpenAuth.Messaging;
+
+	/// <summary>
+	/// Security settings that may be applicable to both relying parties and providers.
+	/// </summary>
+	[Serializable]
+	public abstract class SecuritySettings {
+		/// <summary>
+		/// Gets the default minimum hash bit length.
+		/// </summary>
+		internal const int MinimumHashBitLengthDefault = 160;
+
+		/// <summary>
+		/// Gets the maximum hash bit length default for relying parties.
+		/// </summary>
+		internal const int MaximumHashBitLengthRPDefault = 256;
+
+		/// <summary>
+		/// Gets the maximum hash bit length default for providers.
+		/// </summary>
+		internal const int MaximumHashBitLengthOPDefault = 512;
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="SecuritySettings"/> class.
+		/// </summary>
+		/// <param name="isProvider">A value indicating whether this class is being instantiated for a Provider.</param>
+		protected SecuritySettings(bool isProvider) {
+			this.MaximumHashBitLength = isProvider ? MaximumHashBitLengthOPDefault : MaximumHashBitLengthRPDefault;
+			this.MinimumHashBitLength = MinimumHashBitLengthDefault;
+		}
+
+		/// <summary>
+		/// Gets or sets the minimum hash length (in bits) allowed to be used in an <see cref="Association"/>
+		/// with the remote party.  The default is 160.
+		/// </summary>
+		/// <remarks>
+		/// SHA-1 (160 bits) has been broken.  The minimum secure hash length is now 256 bits.
+		/// The default is still a 160 bit minimum to allow interop with common remote parties,
+		/// such as Yahoo! that only supports 160 bits.  
+		/// For sites that require high security such as to store bank account information and 
+		/// health records, 256 is the recommended value.
+		/// </remarks>
+		public int MinimumHashBitLength { get; set; }
+
+		/// <summary>
+		/// Gets or sets the maximum hash length (in bits) allowed to be used in an <see cref="Association"/>
+		/// with the remote party.  The default is 256 for relying parties and 512 for providers.
+		/// </summary>
+		/// <remarks>
+		/// The longer the bit length, the more secure the identities of your visitors are.
+		/// Setting a value higher than 256 on a relying party site may reduce performance
+		/// as many association requests will be denied, causing secondary requests or even
+		/// authentication failures.
+		/// Setting a value higher than 256 on a provider increases security where possible
+		/// without these side-effects.
+		/// </remarks>
+		public int MaximumHashBitLength { get; set; }
+
+		/// <summary>
+		/// Determines whether a named association fits the security requirements.
+		/// </summary>
+		/// <param name="protocol">The protocol carrying the association.</param>
+		/// <param name="associationType">The value of the openid.assoc_type parameter.</param>
+		/// <returns>
+		/// 	<c>true</c> if the association is permitted given the security requirements; otherwise, <c>false</c>.
+		/// </returns>
+		internal bool IsAssociationInPermittedRange(Protocol protocol, string associationType) {
+			int lengthInBits = HmacShaAssociation.GetSecretLength(protocol, associationType) * 8;
+			return lengthInBits >= this.MinimumHashBitLength && lengthInBits <= this.MaximumHashBitLength;
+		}
+
+		/// <summary>
+		/// Determines whether a given association fits the security requirements.
+		/// </summary>
+		/// <param name="association">The association to check.</param>
+		/// <returns>
+		/// 	<c>true</c> if the association is permitted given the security requirements; otherwise, <c>false</c>.
+		/// </returns>
+		internal bool IsAssociationInPermittedRange(Association association) {
+			Contract.Requires<ArgumentNullException>(association != null);
+			return association.HashBitLength >= this.MinimumHashBitLength && association.HashBitLength <= this.MaximumHashBitLength;
+		}
+	}
+}