raziee
جمعه 10 آذر 1391, 08:32 صبح
کدهای زیر از "Block DoS attacks easily in ASP.NET (http://madskristensen.net/post/Block-DoS-attacks-easily-in-ASPNET.aspx)" گرفته شده است.
مطاله "HttpModule to block external referrers in ASP.NET (http://madskristensen.net/post/HttpModule-to-block-external-referrers-in-ASPNET.aspx)" هم خالی از لطف نیست.
#region Using
using System;
using System.Web;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Timers;
#endregion
/// <summary>
/// Block the response to attacking IP addresses.
/// </summary>
public class DosAttackModule : IHttpModule
{
#region IHttpModule Members
void IHttpModule.Dispose()
{
// Nothing to dispose;
}
void IHttpModule.Init(HttpApplication context)
{
context.BeginRequest += new EventHandler(context_BeginRequest);
}
#endregion
#region Private fields
private static Dictionary<string, short> _IpAdresses = new Dictionary<string, short>();
private static Stack<string> _Banned = new Stack<string>();
private static Timer _Timer = CreateTimer();
private static Timer _BannedTimer = CreateBanningTimer();
#endregion
private const int BANNED_REQUESTS = 10;
private const int REDUCTION_INTERVAL = 1000; // 1 second
private const int RELEASE_INTERVAL = 5 * 60 * 1000; // 5 minutes
private void context_BeginRequest(object sender, EventArgs e)
{
string ip = HttpContext.Current.Request.UserHostAddress;
if (_Banned.Contains(ip))
{
HttpContext.Current.Response.StatusCode = 403;
HttpContext.Current.Response.End();
}
CheckIpAddress(ip);
}
/// <summary>
/// Checks the requesting IP address in the collection
/// and bannes the IP if required.
/// </summary>
private static void CheckIpAddress(string ip)
{
if (!_IpAdresses.ContainsKey(ip))
{
_IpAdresses[ip] = 1;
}
else if (_IpAdresses[ip] == BANNED_REQUESTS)
{
_Banned.Push(ip);
_IpAdresses.Remove(ip);
}
else
{
_IpAdresses[ip]++;
}
}
#region Timers
/// <summary>
/// Creates the timer that substract a request
/// from the _IpAddress dictionary.
/// </summary>
private static Timer CreateTimer()
{
Timer timer = GetTimer(REDUCTION_INTERVAL);
timer.Elapsed += new ElapsedEventHandler(TimerElapsed);
return timer;
}
/// <summary>
/// Creates the timer that removes 1 banned IP address
/// everytime the timer is elapsed.
/// </summary>
/// <returns></returns>
private static Timer CreateBanningTimer()
{
Timer timer = GetTimer(RELEASE_INTERVAL);
timer.Elapsed += delegate { _Banned.Pop(); };
return timer;
}
/// <summary>
/// Creates a simple timer instance and starts it.
/// </summary>
/// <param name="interval">The interval in milliseconds.</param>
private static Timer GetTimer(int interval)
{
Timer timer = new Timer();
timer.Interval = interval;
timer.Start();
return timer;
}
/// <summary>
/// Substracts a request from each IP address in the collection.
/// </summary>
private static void TimerElapsed(object sender, ElapsedEventArgs e)
{
foreach (string key in _IpAdresses.Keys)
{
_IpAdresses[key]--;
if (_IpAdresses[key] == 0)
_IpAdresses.Remove(key);
}
}
#endregion
}