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Posted 17 May 2003

The case for a channel-schema concept

, 17 May 2003 CPOL
An article about .NET remoting channel schemas
// Stephen Toub
// SecureServerChannelSinkProvider.cs

using System;
using System.Net;
using System.Collections;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;

namespace MsdnMag.Remoting
	/// <summary>Used to create a secure server channel sink.</summary>
	public class SecureServerChannelSinkProvider : IServerChannelSinkProvider
		#region Member Variables
		/// <summary>The next sink provider in the sink provider chain.</summary>
		private IServerChannelSinkProvider _next = null;
		/// <summary>The name of the symmetric algorithm to use.</summary>
		private string _algorithm = "DES";
		/// <summary>Whether OAEP padding should be used.</summary>
		private bool _oaep = false;
		/// <summary>Whether the server requires the client to use the secure client sink.</summary>
		private bool _requireSecurity = false;
		/// <summary>The minimum amount of time (s) information about a client connection should be retained.</summary>
		private double _connectionAgeLimit = 60.0;
		/// <summary>How often (s) the connection sweeper should run.</summary>
		private double _sweepFrequency = 15.0;
		/// <summary>List of client IP's that should have the opposite security requirement.</summary>
		private IPAddress [] _securityExemptionList = null;

		#region Construction
		/// <summary>Initializes the sink provider.</summary>
		public SecureServerChannelSinkProvider()

		/// <summary>Initializes the sink provider.</summary>
		/// <param name="properties">Parameters specified in the config file.</param>
		/// <param name="providerData">Sink provider data.</param>
		public SecureServerChannelSinkProvider(IDictionary properties, ICollection providerData)
			// Read in web.config parameters
			foreach (DictionaryEntry entry in properties)
				switch ((String)entry.Key)
					case "algorithm":
						_algorithm = (string)entry.Value;

					case "oaep":
						_oaep = bool.Parse((string)entry.Value);

					case "connectionAgeLimit":
						_connectionAgeLimit = double.Parse((string)entry.Value); 
						if (_connectionAgeLimit < 0) throw new ArgumentException("Connection age limit must be greater than 0.", "_connectionAgeLimit");

					case "sweepFrequency":
						_sweepFrequency = double.Parse((string)entry.Value); 
						if (_sweepFrequency < 0) throw new ArgumentException("Sweep frequency must be greater than 0.", "_sweepFrequency");

					case "requireSecurity":
						_requireSecurity = bool.Parse((string)entry.Value);

					case "securityExemptionList":
						// Get the semicolon separated list of IP addresses and parse them
						// all into an array of IPAddress objects
						string ipList = (string)entry.Value;
						if (ipList != null && ipList != string.Empty) 
							string [] values = ipList.Split(';');
							_securityExemptionList = new IPAddress[values.Length];
							for(int i=0; i<values.Length; i++) _securityExemptionList[i] = IPAddress.Parse(values[i].Trim());

						throw new ArgumentException("Invalid configuration entry: " + (String)entry.Key);

		#region Sink Creation
		/// <summary>Creates the channel sink.</summary>
		/// <param name="channel">The channel for which to create the channel sink chain.</param>
		/// <returns>The new channel sink.</returns>
		public IServerChannelSink CreateSink(IChannelReceiver channel)
			IServerChannelSink nextSink = null;
			if (_next != null) 
				// Call CreateSink on the next sink provider in the chain.  This will return
				// to us the actual next sink object.  If the next sink is null, uh oh!
				if ((nextSink = _next.CreateSink(channel)) == null) return null;

			// Create this sink, passing to it the previous sink in the chain so that it knows
			// to whom messages should be passed.
			return new SecureServerChannelSink(
				nextSink, _algorithm, _oaep, 
				_connectionAgeLimit, _sweepFrequency, 
				_requireSecurity, _securityExemptionList);

		/// <summary>Returns the channel data for the channel that the current sink is associated with.</summary>
		/// <param name="channelData">An IChannelDataStore object in which the channel data is to be returned.</param>
		public void GetChannelData(System.Runtime.Remoting.Channels.IChannelDataStore channelData)
			// Do nothing.  No channel specific data.

		/// <summary>Gets or sets the next sink provider in the channel sink provider chain.</summary>
		public System.Runtime.Remoting.Channels.IServerChannelSinkProvider Next
			get { return _next; }
			set { _next = value; }

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About the Author

Wytek Szymanski
Web Developer
United States United States
I am a consultant, trainer, software archtect/engineer, since the early 1980s, working in the greater area of Boston, MA, USA.

My work comprises the entire spectrum of software, shrink-wrapped applications, IT client-server, systems and protocol related work, compilers and operating systems, and more ....

I am currently focused on platform development for distributed computing in service oriented data centers.

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