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
|
# Copyright (c) 2016 DeNA Co., Ltd., Ichito Nagata
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to
# deal in the Software without restriction, including without limitation the
# rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
# sell copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
# IN THE SOFTWARE.
#
require File.expand_path(File.dirname(__FILE__)) + "/lru_cache.rb"
class DoSDetector
def initialize(config={})
config = {
:strategy => CountingStrategy.new,
:callback => self.class.default_callback,
:forwarded => true,
:cache_size => 128,
}.merge(config)
@strategy = config[:strategy]
@callback = config[:callback]
@forwarded = !!(config[:forwarded])
@cache = LRUCache.new(config[:cache_size])
raise "strategy must not be nil" if @strategy.nil?
raise "callback must not be nil" if @callback.nil?
end
def self.default_callback
Proc.new do |env, detected, ip|
if detected
[ 403, { "Content-Type" => "text/plain" }, [ "Forbidden" ] ]
else
[ 399, {}, [] ]
end
end
end
def self.fallthrough_callback
Proc.new do |env, detected, ip, vars|
if detected
vars ||= {}
env_headers = vars.merge({:ip => ip}).map { |k, v| [ "x-fallthru-set-dos-#{k}", v.to_s ] }.to_h
[ 399, env_headers, [] ]
else
[ 399, {}, [] ]
end
end
end
def call(env)
now = Time.now.to_i
ip = env['REMOTE_ADDR']
if @forwarded && (xff = env['HTTP_X_FORWARDED_FOR'])
ip = xff.split(",")[0]
end
unless client = @cache.get(ip)
client = { :ip => ip }
@cache.set(ip, client)
end
detected, *args = @strategy.detect?(client, now, env)
return @callback.call(env, detected, ip, *args)
end
class CountingStrategy
def initialize(config={})
config = {
:period => 10,
:threshold => 100,
:ban_period => 300,
}.merge(config)
@period = config[:period]
@threshold = config[:threshold]
@ban_period = config[:ban_period]
raise "period must be greater than zero" if @period <= 0
raise "threshold must be greater than zero" if @threshold <= 0
raise "ban_period must not be negative" if @ban_period < 0
end
def detect?(client, now, env)
count = countup(client, now)
banned_until = client[:banned_until] || 0
if banned_until >= now
detected = true
else
detected = count >= @threshold
if detected
banned_until = now + @ban_period
client[:banned_until] = banned_until
end
end
return detected, { :count => count, :banned_until => banned_until }
end
private
def countup(client, now)
count = client[:count] || 0
period_index = client[:period_index] || 0
current_period_index = (now / @period).floor
if current_period_index > period_index
count -= (current_period_index - period_index) * @threshold
count = 0 if count < 0
client[:period_index] = current_period_index
end
count += 1
client[:count] = count
return count
end
end
end
|
