Update the client IP extraction resolution base on the latest RFC.

- Update the list of HTTP headers to look for IP
- Add support to parsing HTTP IP Headers with multiple IP addresses
- Update specs
- Change Tracing::ClientIp module methods visibility

LICENSE-3rdparty.csv

@@ -5,3 +5,4 @@ lib/datadog/tracing/contrib/utils/quantization/http.rb,https://github.com/ruby/u
 ext/ddtrace_profiling_native_extension/private_vm_api_access,https://github.com/ruby/ruby,BSD-2-Clause,"Copyright (C) 1993-2013 Yukihiro Matsumoto. All rights reserved."
 msgpack,https://rubygems.org/gems/msgpack,Apache-2.0,"Copyright (c) 2008-2015 Sadayuki Furuhashi"
 debase-ruby_core_source,https://rubygems.org/gems/debase-ruby_core_source,MIT for gem and BSD-2-Clause for Ruby sources,"Copyright (c) 2012 Gabriel Horner. Files from Ruby sources are Copyright (C) 1993-2013 Yukihiro Matsumoto. All rights reserved."
+lib/datadog/core/vendor/ipaddr,https://github.com/ruby/ipaddr/blob/master/lib/ipaddr.rb,BSD 2-Clause "Simplified" License,"Copyright (c) 2002 Hajimu UMEMOTO <[email protected]> Copyright (c) 2007-2017 Akinori MUSHA <[email protected]>"

lib/datadog/appsec/contrib/rack/gateway/request.rb

@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
 require_relative '../../../instrumentation/gateway/argument'
+require_relative '../../../../core/header_collection'
 require_relative '../../../../tracing/client_ip'
-require_relative '../../../../tracing/contrib/rack/header_collection'
 
 module Datadog
   module AppSec
@@ -85,16 +85,9 @@ def form_hash
 
             def client_ip
               remote_ip = remote_addr
-              headers = Datadog::Tracing::Contrib::Rack::Header::RequestHeaderCollection.new(env)
+              header_collection = Datadog::Core::HeaderCollection.from_hash(headers)
 
-              result = Datadog::Tracing::ClientIp.raw_ip_from_request(headers, remote_ip)
-
-              if result.raw_ip
-                ip = Datadog::Tracing::ClientIp.strip_decorations(result.raw_ip)
-                return unless Datadog::Tracing::ClientIp.valid_ip?(ip)
-
-                ip
-              end
+              Datadog::Tracing::ClientIp.extract_client_ip(header_collection, remote_ip)
             end
           end
         end

lib/datadog/core/utils/network.rb

@@ -0,0 +1,140 @@
+# frozen_string_literal: true
+
+require 'ipaddr'
+require_relative '../vendor/ipaddr'
+
+module Datadog
+  module Core
+    module Utils
+      # Common Network utility functions.
+      module Network
+        DEFAULT_IP_HEADERS_NAMES = %w[
+          x-forwarded-for
+          x-real-ip
+          true-client-ip
+          x-client-ip
+          x-forwarded
+          forwarded-for
+          x-cluster-client-ip
+          fastly-client-ip
+          cf-connecting-ip
+          cf-connecting-ipv6
+        ].freeze
+
+        class << self
+          # Returns a client IP associated with the request if it was
+          #   retrieved successfully.
+          #
+          #
+          # @param [Datadog::Core::HeaderCollection, #get, nil] headers The request headers
+          # @param [Array<String>] list of headers to check.
+          # @return [String] IP value without the port and the zone indentifier.
+          # @return [nil] when no valid IP value found.
+          def stripped_ip_from_request_headers(headers, ip_headers_to_check: DEFAULT_IP_HEADERS_NAMES)
+            ip = ip_header(headers, ip_headers_to_check)
+
+            ip ? ip.to_s : nil
+          end
+
+          # @param [String] IP value.
+          # @return [String] IP value without the port and the zone indentifier.
+          # @return [nil] when no valid IP value found.
+          def stripped_ip(ip)
+            ip = ip_to_ipaddr(ip)
+            ip ? ip.to_s : nil
+          end
+
+          private
+
+          # @param [String] IP value.
+          # @return [IPaddr]
+          # @return [nil] when no valid IP value found.
+          def ip_to_ipaddr(ip)
+            return unless ip
+
+            clean_ip = if likely_ipv4?(ip)
+                         strip_ipv4_port(ip)
+                       else
+                         strip_zone_specifier(strip_ipv6_port(ip))
+                       end
+
+            begin
+              IPAddr.new(clean_ip)
+            rescue IPAddr::Error
+              nil
+            end
+          end
+
+          def ip_header(headers, ip_headers_to_check)
+            return unless headers
+
+            ip_headers_to_check.each do |name|
+              value = headers.get(name)
+
+              next unless value
+
+              ips = value.split(',')
+              ips.each do |ip|
+                parsed_ip = ip_to_ipaddr(ip.strip)
+
+                return parsed_ip if global_ip?(parsed_ip)
+              end
+            end
+
+            nil
+          end
+
+          # Returns whether the given value is more likely to be an IPv4 than an IPv6 address.
+          #
+          # This is done by checking if a dot (`'.'`) character appears before a colon (`':'`) in the value.
+          # The rationale is that in valid IPv6 addresses, colons will always preced dots,
+          #   and in valid IPv4 addresses dots will always preced colons.
+          def likely_ipv4?(value)
+            dot_index = value.index('.') || value.size
+            colon_index = value.index(':') || value.size
+
+            dot_index < colon_index
+          end
+
+          def strip_zone_specifier(ipv6)
+            ipv6.gsub(/%.*/, '')
+          end
+
+          def strip_ipv6_port(ip)
+            if /\[(.*)\](?::\d+)?/ =~ ip
+              Regexp.last_match(1)
+            else
+              ip
+            end
+          end
+
+          def strip_ipv4_port(ip)
+            ip.gsub(/:\d+\z/, '')
+          end
+
+          def global_ip?(parsed_ip)
+            parsed_ip && !private?(parsed_ip) && !loopback?(parsed_ip) && !link_local?(parsed_ip)
+          end
+
+          # TODO: remove once we drop support for ruby 2.1, 2.2, 2.3, 2.4
+          # replace with ip.private?
+          def private?(ip)
+            Datadog::Core::Vendor::IPAddr.private?(ip)
+          end
+
+          # TODO: remove once we drop support for ruby 2.1, 2.2, 2.3, 2.4
+          # replace with ip.link_local?
+          def link_local?(ip)
+            Datadog::Core::Vendor::IPAddr.link_local?(ip)
+          end
+
+          # TODO: remove once we drop support for ruby 2.1, 2.2, 2.3, 2.4
+          # replace with ip.loopback
+          def loopback?(ip)
+            Datadog::Core::Vendor::IPAddr.loopback?(ip)
+          end
+        end
+      end
+    end
+  end
+end

lib/datadog/core/vendor/ipaddr.rb

@@ -0,0 +1,78 @@
+# Copyright (c) 2002 Hajimu UMEMOTO <[email protected]>
+# Copyright (c) 2007-2017 Akinori MUSHA <[email protected]>
+
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+# 2. 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.
+
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 AUTHOR OR 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.
+
+module Datadog
+  module Core
+    module Vendor
+      # vendor code from https://github.com/ruby/ipaddr/blob/master/lib/ipaddr.rb
+      # Ruby version below 2.5 does not have the IpAddr#private? method
+      # We have to vendor the code because ruby versions below 2.5 did not extract ipaddr as a gem
+      # So we can not specify a specific version for ipaddr for ruby versions: 2.1, 2.2, 2.3, 2.4
+      module IPAddr
+        class << self
+          def private?(ip)
+            addr = ip.instance_variable_get(:@addr)
+
+            case ip.family
+            when Socket::AF_INET
+              addr & 0xff000000 == 0x0a000000 ||    # 10.0.0.0/8
+                addr & 0xfff00000 == 0xac100000 ||  # 172.16.0.0/12
+                addr & 0xffff0000 == 0xc0a80000     # 192.168.0.0/16
+            when Socket::AF_INET6
+              addr & 0xfe00_0000_0000_0000_0000_0000_0000_0000 == 0xfc00_0000_0000_0000_0000_0000_0000_0000
+            else
+              raise IPAddr::AddressFamilyError, 'unsupported address family'
+            end
+          end
+
+          def link_local?(ip)
+            addr = ip.instance_variable_get(:@addr)
+
+            case ip.family
+            when Socket::AF_INET
+              addr & 0xffff0000 == 0xa9fe0000 # 169.254.0.0/16
+            when Socket::AF_INET6
+              addr & 0xffc0_0000_0000_0000_0000_0000_0000_0000 == 0xfe80_0000_0000_0000_0000_0000_0000_0000
+            else
+              raise IPAddr::AddressFamilyError, 'unsupported address family'
+            end
+          end
+
+          def loopback?(ip)
+            addr = ip.instance_variable_get(:@addr)
+
+            case ip.family
+            when Socket::AF_INET
+              addr & 0xff000000 == 0x7f000000
+            when Socket::AF_INET6
+              addr == 1
+            else
+              raise IPAddr::AddressFamilyError, 'unsupported address family'
+            end
+          end
+        end
+      end
+    end
+  end
+end