// IPrivacyProvider extension methods.// Copyright (C) 2010 Lex Li// // Permission is hereby granted, free of charge, to any person obtaining a copy of this// software and associated documentation files (the "Software"), to deal in the Software// without restriction, including without limitation the rights to use, copy, modify, merge,// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons// to whom the Software is furnished to do so, subject to the following conditions:// // The above copyright notice and this permission notice shall be included in all copies or// substantial portions of the Software.// // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER// DEALINGS IN THE SOFTWARE. /* * Created by SharpDevelop. * User: lextm * Date: 10/10/2010 * Time: 6:59 AM *  * To change this template use Tools | Options | Coding | Edit Standard Headers. */using System; namespace GSF.Net.Snmp.Security{    /// <summary>    /// Extension class for <see cref="IPrivacyProvider"/>.    /// </summary>    public static class PrivacyProviderExtension    {        /// <summary>        /// Converts to <see cref="Levels"/>.        /// </summary>        /// <returns>Levels.</returns>        public static Levels ToSecurityLevel(this IPrivacyProvider privacy)        {            if (privacy == null)            {                throw new ArgumentNullException(nameof(privacy));            }                            Levels flags;            if (privacy.AuthenticationProvider == DefaultAuthenticationProvider.Instance)            {                flags = 0;            }            else if (privacy is DefaultPrivacyProvider)            {                flags = Levels.Authentication;            }            else            {                flags = Levels.Authentication | Levels.Privacy;            }             return flags;        }         /// <summary>        /// Gets the scope data.        /// </summary>        /// <param name="privacy">The privacy provider.</param>        /// <param name="header">The header.</param>        /// <param name="parameters">The parameters.</param>        /// <param name="rawScopeData">The raw scope data.</param>        /// <returns>ISnmpData.</returns>        /// <exception cref="System.ArgumentNullException">        /// privacy        /// or        /// header        /// </exception>        public static ISnmpData GetScopeData(this IPrivacyProvider privacy, Header header, SecurityParameters parameters, ISnmpData rawScopeData)        {            if (privacy == null)            {                throw new ArgumentNullException(nameof(privacy));            }             if (header == null)            {                throw new ArgumentNullException(nameof(header));            }             return Levels.Privacy == (header.SecurityLevel & Levels.Privacy)                       ? privacy.Encrypt(rawScopeData, parameters)                       : rawScopeData;        }         /// <summary>        /// Computes the hash.        /// </summary>        /// <param name="version">The version.</param>        /// <param name="header">The header.</param>        /// <param name="parameters">The parameters.</param>        /// <param name="scope">The scope.</param>        /// <param name="privacy">The privacy provider.</param>        public static void ComputeHash(this IPrivacyProvider privacy, VersionCode version, Header header, SecurityParameters parameters, ISegment scope)        {            if (header == null)            {                throw new ArgumentNullException(nameof(header));            }             if (parameters == null)            {                throw new ArgumentNullException(nameof(parameters));            }             if (scope == null)            {                throw new ArgumentNullException(nameof(scope));            }             if (privacy == null)            {                throw new ArgumentNullException(nameof(privacy));            }             IAuthenticationProvider provider = privacy.AuthenticationProvider;            if (provider is DefaultAuthenticationProvider)            {                return;            }             if (0 == (header.SecurityLevel & Levels.Authentication))            {                return;            }             ISnmpData scopeData = privacy.GetScopeData(header, parameters, scope.GetData(version));            parameters.AuthenticationParameters = provider.ComputeHash(version, header, parameters, scopeData, privacy, null); // replace the hash.        }         /// <summary>        /// Verifies the hash.        /// </summary>        /// <param name="version">The version.</param>        /// <param name="header">The header.</param>        /// <param name="parameters">The parameters.</param>        /// <param name="scopeBytes">The scope bytes.</param>        /// <param name="privacy">The privacy provider.</param>        /// <param name="length">The length bytes.</param>        /// <returns>        /// Returns <c>true</c> if hash matches. Otherwise, returns <c>false</c>.        /// </returns>        public static bool VerifyHash(this IPrivacyProvider privacy, VersionCode version, Header header, SecurityParameters parameters, ISnmpData scopeBytes, byte[] length)        {            if (header == null)            {                throw new ArgumentNullException(nameof(header));            }             if (parameters == null)            {                throw new ArgumentNullException(nameof(parameters));            }             if (scopeBytes == null)            {                throw new ArgumentNullException(nameof(scopeBytes));            }             if (privacy == null)            {                throw new ArgumentNullException(nameof(privacy));            }             IAuthenticationProvider provider = privacy.AuthenticationProvider;            if (provider is DefaultAuthenticationProvider)            {                return true;            }             if (0 == (header.SecurityLevel & Levels.Authentication))            {                return true;            }             OctetString expected = parameters.AuthenticationParameters;            parameters.AuthenticationParameters = provider.CleanDigest; // clean the hash first.            OctetString newHash = provider.ComputeHash(version, header, parameters, scopeBytes, privacy, length);            parameters.AuthenticationParameters = expected; // restore the hash.            return newHash == expected;        }    }}