1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
|
/*
* 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;
}
}
|
