CFINSPEC-77 : Add ipnat resource

Signed-off-by: Sonu Saha <sonu.saha@progress.com>

docs-chef-io/content/inspec/resources/ipnat.md

@@ -0,0 +1,65 @@
++++
+title = "ipnat resource"
+draft = false
+gh_repo = "inspec"
+platform = "bsd"
+platform = "solaris"
+
+[menu]
+  [menu.inspec]
+    title = "ipnat"
+    identifier = "inspec/resources/os/ipnat.md ipnat resource"
+    parent = "inspec/resources/os"
++++
+
+Use the `ipnat` Chef InSpec audit resource to test rules that are defined for `IP NAT`. The ipnat utility is responsible for adding or removing set of rules to and from the IP NAT. Rules are added to the end of the internal lists, matching the order in which they appear when given to ipnat. `ipnat -l` helps to view the list of current NAT table entry mappings. The rule match is done against the output rules of `ipnat -l`.
+
+## Availability
+
+### Installation
+
+This resource is distributed along with Chef InSpec itself. You can use it automatically.
+
+### Version
+
+This resource first became available in v4.52.x of InSpec.
+
+## Syntax
+
+An `ipnat` resource block declares tests for rules set for IP NAT:
+
+    describe ipnat do
+      it { should have_rule("RULE") }
+    end
+
+where
+
+- `have_rule('RULE')` tests the active rule for IP NAT. This must match the entire line taken from `ipnat -l`.
+
+## Examples
+
+The following examples show how to use this Chef InSpec audit resource.
+
+### Test if there is a rule for mapping of the internally used IP address to an ISP provided 8-bit subnet at 10.9.0.1 on the network interface en0
+
+    describe ipnat do
+      it { should have_rule("map en0 192.0.0.0/8 -> 10.9.0.1/24") }
+    end
+
+### Test if there is a rule for NAT that specifies to use the builtin ftp-proxy
+
+    describe ipnat do
+      it { should have_rule("map en0 192.0.0.0/8 -> 10.9.0.1/32 proxy port ftp ftp/tcp") }
+    end
+
+Note that the rule specification must exactly match what's in the output of `ipnat -l`, which will depend on how you've built your rules.
+
+## Matchers
+
+For a full list of available matchers, please visit our [matchers page](/inspec/matchers/).
+
+### have_rule
+
+The `have_rule` matcher tests the named rule against the information in the output rule of `ipnat -l`:
+
+    it { should have_rule("RULE") }

lib/inspec/resources/ipnat.rb

@@ -0,0 +1,60 @@
+require "inspec/resources/command"
+#require "pry-byebug"
+module Inspec::Resources
+  class IpNat < Inspec.resource(1)
+    name "ipnat"
+    supports platform: "freebsd"
+    supports platform: "solaris"
+    desc "Use the ipnat InSpec audit resource to test rules that are defined for NAT"
+    example <<~EXAMPLE
+      describe ipnat do
+        it { should have_rule("map net1 192.168.0.0/24 -> 0/32") }
+      end
+    EXAMPLE
+
+    def initialize
+      # checks if the instance is either bsd or solaris
+      return if inspec.os.bsd? || inspec.os.solaris?
+
+      # ensures, all calls are aborted for non-supported os
+      @ipnat_cache = []
+      skip_resource "The `ipnat` resource is not supported on your OS yet."
+    end
+
+    def has_rule?(rule = nil)
+      # checks if the rule is part of the ruleset
+      retrieve_rules.any? { |line| line.casecmp(rule) == 0 }
+    end
+
+    def retrieve_rules
+      # this would be true if the OS family was not bsd/solaris when checked in initliaze
+      return @ipnat_cache if defined?(@ipnat_cache)
+
+      # construct ipnat command to show the list of current NAT table entry mappings
+      bin = find_ipnat_or_error
+      ipnat_cmd = "#{bin} -l"
+      cmd = inspec.command(ipnat_cmd)
+      #binding.pry
+      # Return empty array when command is not executed successfully
+      # or there is no output since no rules are active
+      return [] if cmd.exit_status.to_i != 0 || cmd.stdout == ""
+
+      # split rules, returns array or rules
+      @ipnat_cache = cmd.stdout.split("\n").map(&:strip)
+    end
+
+    def to_s
+      format("Ipnat").strip
+    end
+
+    private
+
+    def find_ipnat_or_error
+      %w{/usr/sbin/ipnat /sbin/ipnat ipnat}.each do |cmd|
+        return cmd if inspec.command(cmd).exist?
+      end
+
+      raise Inspec::Exceptions::ResourceFailed, "Could not find `ipnat`"
+    end
+  end
+end

test/fixtures/cmd/ipnat-l

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+List of active MAP/Redirect filters:
+map en0 192.0.0.0/8 -> 10.9.0.1/32 proxy port ftp ftp/tcp
+map en0 192.0.0.0/8 -> 10.9.0.1/32 portmap tcp/udp 20000:40000 mssclamp 1452
+map en0 192.0.0.0/8 -> 10.9.0.1/32
+map net1 192.168.0.0/24 -> 0/32
+
+List of active sessions:

test/helpers/mock_loader.rb

@@ -369,6 +369,9 @@ class MockLoader
       # ip6tables
       "/usr/sbin/ip6tables  -S" => cmd.call("ip6tables-s"),
       %{sh -c 'type "/usr/sbin/ip6tables"'} => empty.call,
+      # ipnat
+      "/usr/sbin/ipnat -l" => cmd.call("ipnat-l"),
+      %{type "/usr/sbin/ipnat"} => empty.call,
       # apache_conf
       "sh -c 'find /etc/apache2/ports.conf -type f -maxdepth 1'" => cmd.call("find-apache2-ports-conf"),
       "sh -c 'find /etc/httpd/conf.d/*.conf -type f -maxdepth 1'" => cmd.call("find-httpd-ssl-conf"),

test/unit/resources/ipnat_test.rb

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+require "helper"
+require "inspec/resource"
+require "inspec/resources/ipnat"
+
+describe "Inspec::Resources::Ipnat" do
+  # freebsd11
+  it "verify ipfilter on freebsd" do
+    resource = MockLoader.new(:freebsd11).load_resource("ipnat")
+    _(resource.has_rule?("map net1 192.168.0.0/24 -> 0/32")).must_equal true
+    _(resource.has_rule?("map en0 192.0.0.0/8 -> 10.9.0.1/32")).must_equal true
+    _(resource.has_rule?("map en0 192.0.0.0/8 -> 10.9.0.1/32 proxy port ftp ftp/tcp")).must_equal true
+    _(resource.has_rule?(nil)).must_equal false
+  end
+
+  # solaris11
+  it "verify ipfilter on freebsd" do
+    resource = MockLoader.new(:solaris11).load_resource("ipnat")
+    _(resource.has_rule?("map net1 192.168.0.0/24 -> 0/32")).must_equal true
+    _(resource.has_rule?("map en0 192.0.0.0/8 -> 10.9.0.1/32")).must_equal true
+    _(resource.has_rule?("map en0 192.0.0.0/8 -> 10.9.0.1/32 proxy port ftp ftp/tcp")).must_equal true
+    _(resource.has_rule?(nil)).must_equal false
+  end
+
+  # undefined
+  it "verify ipfilter on unsupported os" do
+    resource = MockLoader.new(:undefined).load_resource("ipnat")
+    _(resource.has_rule?("map net1 192.168.0.0/24 -> 0/32")).must_equal false
+    _(resource.has_rule?("map en0 192.0.0.0/8 -> 10.9.0.1/32")).must_equal false
+    _(resource.has_rule?("map en0 192.0.0.0/8 -> 10.9.0.1/32 proxy port ftp ftp/tcp")).must_equal false
+  end
+
+end