1 files changed, 209 insertions, 0 deletions

diff --git a/OpenSim/Framework/BasicDOSProtector.cs b/OpenSim/Framework/BasicDOSProtector.cs
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+++ b/OpenSim/Framework/BasicDOSProtector.cs
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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 System.Timers.Timer _forgetTimer;  // Cleanup timer
+        private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
+        private readonly System.Threading.ReaderWriterLockSlim _lockSlim = 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>();
+            _forgetTimer = new System.Timers.Timer();
+            _forgetTimer.Elapsed += delegate
+            {
+                _forgetTimer.Enabled = false;
+
+                List<string> removes = new List<string>();
+                _lockSlim.EnterReadLock();
+                foreach (string str in _tempBlocked.Keys)
+                {
+                    if (
+                        Util.EnvironmentTickCountSubtract(Util.EnvironmentTickCount(),
+                                                          _tempBlocked[str]) > 0)
+                        removes.Add(str);
+                }
+                _lockSlim.ExitReadLock();
+                lock (_deeperInspection)
+                {
+                    _lockSlim.EnterWriteLock();
+                    for (int i = 0; i < removes.Count; i++)
+                    {
+                        _tempBlocked.Remove(removes[i]);
+                        _deeperInspection.Remove(removes[i]);
+                    }
+                    _lockSlim.ExitWriteLock();
+                }
+                foreach (string str in removes)
+                {
+                    m_log.InfoFormat("[{0}] client: {1} is no longer blocked.",
+                                     _options.ReportingName, str);
+                }
+                _lockSlim.EnterReadLock();
+                if (_tempBlocked.Count > 0)
+                    _forgetTimer.Enabled = true;
+                _lockSlim.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;
+             _lockSlim.EnterReadLock();
+            ret = _tempBlocked.ContainsKey(key);
+            _lockSlim.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;
+
+            _lockSlim.EnterReadLock();
+            if (_tempBlocked.ContainsKey(clientstring))
+            {
+                _lockSlim.ExitReadLock();
+
+                if (_options.ThrottledAction == ThrottleAction.DoThrottledMethod)
+                    return false;
+                else
+                    throw new System.Security.SecurityException("Throttled");
+            }
+            _lockSlim.ExitReadLock();
+
+            _generalRequestTimes.Put(Util.EnvironmentTickCount());
+
+            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;
+        }
+
+        /// <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
+                        _lockSlim.EnterWriteLock();
+                        if (!_tempBlocked.ContainsKey(clientstring))
+                            _tempBlocked.Add(clientstring, Util.EnvironmentTickCount() + (int)_options.ForgetTimeSpan.TotalMilliseconds);
+                        else
+                            _tempBlocked[clientstring] = Util.EnvironmentTickCount() + (int)_options.ForgetTimeSpan.TotalMilliseconds;
+                        _lockSlim.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;
+    }
+}