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//-----------------------------------------------------------------------
// <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) {
Requires.NotNull(association, "association");
return association.HashBitLength >= this.MinimumHashBitLength && association.HashBitLength <= this.MaximumHashBitLength;
}
}
}
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