opensim-development – Rev 1
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/*
* Copyright (c) Contributors, http://opensimulator.org/
* See CONTRIBUTORS.TXT for a full list of copyright holders.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the OpenSimulator Project nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
using System;
using System.Collections.Generic;
using System.Reflection;
using log4net;
namespace OpenSim.Framework
{
public class BasicDOSProtector
{
public enum ThrottleAction
{
DoThrottledMethod,
DoThrow
}
private readonly CircularBuffer<int> _generalRequestTimes; // General request checker
private readonly BasicDosProtectorOptions _options;
private readonly Dictionary<string, CircularBuffer<int>> _deeperInspection; // per client request checker
private readonly Dictionary<string, int> _tempBlocked; // blocked list
private readonly Dictionary<string, int> _sessions;
private readonly System.Timers.Timer _forgetTimer; // Cleanup timer
private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
private readonly System.Threading.ReaderWriterLockSlim _blockLockSlim = new System.Threading.ReaderWriterLockSlim();
private readonly System.Threading.ReaderWriterLockSlim _sessionLockSlim = new System.Threading.ReaderWriterLockSlim();
public BasicDOSProtector(BasicDosProtectorOptions options)
{
_generalRequestTimes = new CircularBuffer<int>(options.MaxRequestsInTimeframe + 1, true);
_generalRequestTimes.Put(0);
_options = options;
_deeperInspection = new Dictionary<string, CircularBuffer<int>>();
_tempBlocked = new Dictionary<string, int>();
_sessions = new Dictionary<string, int>();
_forgetTimer = new System.Timers.Timer();
_forgetTimer.Elapsed += delegate
{
_forgetTimer.Enabled = false;
List<string> removes = new List<string>();
_blockLockSlim.EnterReadLock();
foreach (string str in _tempBlocked.Keys)
{
if (
Util.EnvironmentTickCountSubtract(Util.EnvironmentTickCount(),
_tempBlocked[str]) > 0)
removes.Add(str);
}
_blockLockSlim.ExitReadLock();
lock (_deeperInspection)
{
_blockLockSlim.EnterWriteLock();
for (int i = 0; i < removes.Count; i++)
{
_tempBlocked.Remove(removes[i]);
_deeperInspection.Remove(removes[i]);
_sessions.Remove(removes[i]);
}
_blockLockSlim.ExitWriteLock();
}
foreach (string str in removes)
{
m_log.InfoFormat("[{0}] client: {1} is no longer blocked.",
_options.ReportingName, str);
}
_blockLockSlim.EnterReadLock();
if (_tempBlocked.Count > 0)
_forgetTimer.Enabled = true;
_blockLockSlim.ExitReadLock();
};
_forgetTimer.Interval = _options.ForgetTimeSpan.TotalMilliseconds;
}
/// <summary>
/// Given a string Key, Returns if that context is blocked
/// </summary>
/// <param name="key">A Key identifying the context</param>
/// <returns>bool Yes or No, True or False for blocked</returns>
public bool IsBlocked(string key)
{
bool ret = false;
_blockLockSlim.EnterReadLock();
ret = _tempBlocked.ContainsKey(key);
_blockLockSlim.ExitReadLock();
return ret;
}
/// <summary>
/// Process the velocity of this context
/// </summary>
/// <param name="key"></param>
/// <param name="endpoint"></param>
/// <returns></returns>
public bool Process(string key, string endpoint)
{
if (_options.MaxRequestsInTimeframe < 1 || _options.RequestTimeSpan.TotalMilliseconds < 1)
return true;
string clientstring = key;
_blockLockSlim.EnterReadLock();
if (_tempBlocked.ContainsKey(clientstring))
{
_blockLockSlim.ExitReadLock();
if (_options.ThrottledAction == ThrottleAction.DoThrottledMethod)
return false;
else
throw new System.Security.SecurityException("Throttled");
}
_blockLockSlim.ExitReadLock();
lock (_generalRequestTimes)
_generalRequestTimes.Put(Util.EnvironmentTickCount());
if (_options.MaxConcurrentSessions > 0)
{
int sessionscount = 0;
_sessionLockSlim.EnterReadLock();
if (_sessions.ContainsKey(key))
sessionscount = _sessions[key];
_sessionLockSlim.ExitReadLock();
if (sessionscount > _options.MaxConcurrentSessions)
{
// Add to blocking and cleanup methods
lock (_deeperInspection)
{
_blockLockSlim.EnterWriteLock();
if (!_tempBlocked.ContainsKey(clientstring))
{
_tempBlocked.Add(clientstring,
Util.EnvironmentTickCount() +
(int) _options.ForgetTimeSpan.TotalMilliseconds);
_forgetTimer.Enabled = true;
m_log.WarnFormat("[{0}]: client: {1} is blocked for {2} milliseconds based on concurrency, X-ForwardedForAllowed status is {3}, endpoint:{4}", _options.ReportingName, clientstring, _options.ForgetTimeSpan.TotalMilliseconds, _options.AllowXForwardedFor, endpoint);
}
else
_tempBlocked[clientstring] = Util.EnvironmentTickCount() +
(int) _options.ForgetTimeSpan.TotalMilliseconds;
_blockLockSlim.ExitWriteLock();
}
}
else
ProcessConcurrency(key, endpoint);
}
if (_generalRequestTimes.Size == _generalRequestTimes.Capacity &&
(Util.EnvironmentTickCountSubtract(Util.EnvironmentTickCount(), _generalRequestTimes.Get()) <
_options.RequestTimeSpan.TotalMilliseconds))
{
//Trigger deeper inspection
if (DeeperInspection(key, endpoint))
return true;
if (_options.ThrottledAction == ThrottleAction.DoThrottledMethod)
return false;
else
throw new System.Security.SecurityException("Throttled");
}
return true;
}
private void ProcessConcurrency(string key, string endpoint)
{
_sessionLockSlim.EnterWriteLock();
if (_sessions.ContainsKey(key))
_sessions[key] = _sessions[key] + 1;
else
_sessions.Add(key,1);
_sessionLockSlim.ExitWriteLock();
}
public void ProcessEnd(string key, string endpoint)
{
_sessionLockSlim.EnterWriteLock();
if (_sessions.ContainsKey(key))
{
_sessions[key]--;
if (_sessions[key] <= 0)
_sessions.Remove(key);
}
else
_sessions.Add(key, 1);
_sessionLockSlim.ExitWriteLock();
}
/// <summary>
/// At this point, the rate limiting code needs to track 'per user' velocity.
/// </summary>
/// <param name="key">Context Key, string representing a rate limiting context</param>
/// <param name="endpoint"></param>
/// <returns></returns>
private bool DeeperInspection(string key, string endpoint)
{
lock (_deeperInspection)
{
string clientstring = key;
if (_deeperInspection.ContainsKey(clientstring))
{
_deeperInspection[clientstring].Put(Util.EnvironmentTickCount());
if (_deeperInspection[clientstring].Size == _deeperInspection[clientstring].Capacity &&
(Util.EnvironmentTickCountSubtract(Util.EnvironmentTickCount(), _deeperInspection[clientstring].Get()) <
_options.RequestTimeSpan.TotalMilliseconds))
{
//Looks like we're over the limit
_blockLockSlim.EnterWriteLock();
if (!_tempBlocked.ContainsKey(clientstring))
_tempBlocked.Add(clientstring, Util.EnvironmentTickCount() + (int)_options.ForgetTimeSpan.TotalMilliseconds);
else
_tempBlocked[clientstring] = Util.EnvironmentTickCount() + (int)_options.ForgetTimeSpan.TotalMilliseconds;
_blockLockSlim.ExitWriteLock();
m_log.WarnFormat("[{0}]: client: {1} is blocked for {2} milliseconds, X-ForwardedForAllowed status is {3}, endpoint:{4}", _options.ReportingName, clientstring, _options.ForgetTimeSpan.TotalMilliseconds, _options.AllowXForwardedFor, endpoint);
return false;
}
//else
// return true;
}
else
{
_deeperInspection.Add(clientstring, new CircularBuffer<int>(_options.MaxRequestsInTimeframe + 1, true));
_deeperInspection[clientstring].Put(Util.EnvironmentTickCount());
_forgetTimer.Enabled = true;
}
}
return true;
}
}
public class BasicDosProtectorOptions
{
public int MaxRequestsInTimeframe;
public TimeSpan RequestTimeSpan;
public TimeSpan ForgetTimeSpan;
public bool AllowXForwardedFor;
public string ReportingName = "BASICDOSPROTECTOR";
public BasicDOSProtector.ThrottleAction ThrottledAction = BasicDOSProtector.ThrottleAction.DoThrottledMethod;
public int MaxConcurrentSessions;
}
}