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
|
require 'ipaddr'
module ActionDispatch
# This middleware calculates the IP address of the remote client that is
# making the request. It does this by checking various headers that could
# contain the address, and then picking the last-set address that is not
# on the list of trusted IPs. This follows the precedent set by e.g.
# {the Tomcat server}[https://issues.apache.org/bugzilla/show_bug.cgi?id=50453],
# with {reasoning explained at length}[http://blog.gingerlime.com/2012/rails-ip-spoofing-vulnerabilities-and-protection]
# by @gingerlime. A more detailed explanation of the algorithm is given
# at GetIp#calculate_ip.
#
# Some Rack servers concatenate repeated headers, like {HTTP RFC 2616}[http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.2]
# requires. Some Rack servers simply drop preceding headers, and only report
# the value that was {given in the last header}[http://andre.arko.net/2011/12/26/repeated-headers-and-ruby-web-servers].
# If you are behind multiple proxy servers (like NGINX to HAProxy to Unicorn)
# then you should test your Rack server to make sure your data is good.
#
# IF YOU DON'T USE A PROXY, THIS MAKES YOU VULNERABLE TO IP SPOOFING.
# This middleware assumes that there is at least one proxy sitting around
# and setting headers with the client's remote IP address. If you don't use
# a proxy, because you are hosted on e.g. Heroku without SSL, any client can
# claim to have any IP address by setting the X-Forwarded-For header. If you
# care about that, then you need to explicitly drop or ignore those headers
# sometime before this middleware runs.
class RemoteIp
class IpSpoofAttackError < StandardError; end
# The default trusted IPs list simply includes IP addresses that are
# guaranteed by the IP specification to be private addresses. Those will
# not be the ultimate client IP in production, and so are discarded. See
# http://en.wikipedia.org/wiki/Private_network for details.
TRUSTED_PROXIES = [
"127.0.0.1", # localhost IPv4
"::1", # localhost IPv6
"fc00::/7", # private IPv6 range fc00::/7
"10.0.0.0/8", # private IPv4 range 10.x.x.x
"172.16.0.0/12", # private IPv4 range 172.16.0.0 .. 172.31.255.255
"192.168.0.0/16", # private IPv4 range 192.168.x.x
].map { |proxy| IPAddr.new(proxy) }
attr_reader :check_ip, :proxies
# Create a new +RemoteIp+ middleware instance.
#
# The +ip_spoofing_check+ option is on by default. When on, an exception
# is raised if it looks like the client is trying to lie about its own IP
# address. It makes sense to turn off this check on sites aimed at non-IP
# clients (like WAP devices), or behind proxies that set headers in an
# incorrect or confusing way (like AWS ELB).
#
# The +custom_proxies+ argument can take an Array of string, IPAddr, or
# Regexp objects which will be used instead of +TRUSTED_PROXIES+. If a
# single string, IPAddr, or Regexp object is provided, it will be used in
# addition to +TRUSTED_PROXIES+. Any proxy setup will put the value you
# want in the middle (or at the beginning) of the X-Forwarded-For list,
# with your proxy servers after it. If your proxies aren't removed, pass
# them in via the +custom_proxies+ parameter. That way, the middleware will
# ignore those IP addresses, and return the one that you want.
def initialize(app, ip_spoofing_check = true, custom_proxies = nil)
@app = app
@check_ip = ip_spoofing_check
@proxies = if custom_proxies.blank?
TRUSTED_PROXIES
elsif custom_proxies.respond_to?(:any?)
custom_proxies
else
Array(custom_proxies) + TRUSTED_PROXIES
end
end
# Since the IP address may not be needed, we store the object here
# without calculating the IP to keep from slowing down the majority of
# requests. For those requests that do need to know the IP, the
# GetIp#calculate_ip method will calculate the memoized client IP address.
def call(env)
req = ActionDispatch::Request.new env
req.remote_ip = GetIp.new(req, check_ip, proxies)
@app.call(req.env)
end
# The GetIp class exists as a way to defer processing of the request data
# into an actual IP address. If the ActionDispatch::Request#remote_ip method
# is called, this class will calculate the value and then memoize it.
class GetIp
def initialize(req, check_ip, proxies)
@req = req
@check_ip = check_ip
@proxies = proxies
end
# Sort through the various IP address headers, looking for the IP most
# likely to be the address of the actual remote client making this
# request.
#
# REMOTE_ADDR will be correct if the request is made directly against the
# Ruby process, on e.g. Heroku. When the request is proxied by another
# server like HAProxy or NGINX, the IP address that made the original
# request will be put in an X-Forwarded-For header. If there are multiple
# proxies, that header may contain a list of IPs. Other proxy services
# set the Client-Ip header instead, so we check that too.
#
# As discussed in {this post about Rails IP Spoofing}[http://blog.gingerlime.com/2012/rails-ip-spoofing-vulnerabilities-and-protection/],
# while the first IP in the list is likely to be the "originating" IP,
# it could also have been set by the client maliciously.
#
# In order to find the first address that is (probably) accurate, we
# take the list of IPs, remove known and trusted proxies, and then take
# the last address left, which was presumably set by one of those proxies.
def calculate_ip
# Set by the Rack web server, this is a single value.
remote_addr = ips_from(@req.remote_addr).last
# Could be a CSV list and/or repeated headers that were concatenated.
client_ips = ips_from(@req.client_ip).reverse
forwarded_ips = ips_from(@req.x_forwarded_for).reverse
# +Client-Ip+ and +X-Forwarded-For+ should not, generally, both be set.
# If they are both set, it means that either:
#
# 1) This request passed through two proxies with incompatible IP header
# conventions.
# 2) The client passed one of +Client-Ip+ or +X-Forwarded-For+
# (whichever the proxy servers weren't using) themselves.
#
# Either way, there is no way for us to determine which header is the
# right one after the fact. Since we have no idea, if we are concerned
# about IP spoofing we need to give up and explode. (If you're not
# concerned about IP spoofing you can turn the +ip_spoofing_check+
# option off.)
should_check_ip = @check_ip && client_ips.last && forwarded_ips.last
if should_check_ip && !forwarded_ips.include?(client_ips.last)
# We don't know which came from the proxy, and which from the user
raise IpSpoofAttackError, "IP spoofing attack?! " +
"HTTP_CLIENT_IP=#{@req.client_ip.inspect} " +
"HTTP_X_FORWARDED_FOR=#{@req.x_forwarded_for.inspect}"
end
# We assume these things about the IP headers:
#
# - X-Forwarded-For will be a list of IPs, one per proxy, or blank
# - Client-Ip is propagated from the outermost proxy, or is blank
# - REMOTE_ADDR will be the IP that made the request to Rack
ips = [forwarded_ips, client_ips, remote_addr].flatten.compact
# If every single IP option is in the trusted list, just return REMOTE_ADDR
filter_proxies(ips).first || remote_addr
end
# Memoizes the value returned by #calculate_ip and returns it for
# ActionDispatch::Request to use.
def to_s
@ip ||= calculate_ip
end
protected
def ips_from(header)
return [] unless header
# Split the comma-separated list into an array of strings
ips = header.strip.split(/[,\s]+/)
ips.select do |ip|
begin
# Only return IPs that are valid according to the IPAddr#new method
range = IPAddr.new(ip).to_range
# we want to make sure nobody is sneaking a netmask in
range.begin == range.end
rescue ArgumentError
nil
end
end
end
def filter_proxies(ips)
ips.reject do |ip|
@proxies.any? { |proxy| proxy === ip }
end
end
end
end
end
|
