Log leaked constants and fail rake spec on leak

MSP-11130

Instead of printing the leaked constants to stderr, log them to
`log/leaked-constants.log`.  In task action for spec, read
`log/leaked-constants.log`.  If it exists, print each leaked constants
(and it appropriate it's module full name) and then exit with 1.  If the
file does not exist, do nothing.

Rakefile

@@ -9,3 +9,4 @@ require 'metasploit/framework/require'
 Metasploit::Framework::Require.optionally_active_record_railtie
 
 Metasploit::Framework::Application.load_tasks
+Metasploit::Framework::Spec::Constants.define_task

lib/metasploit/framework/spec/constants.rb

@@ -3,6 +3,10 @@
 # Monitor constants created by module loading to ensure that the loads in one example don't interfere with the
 # assertions in another example.
 module Metasploit::Framework::Spec::Constants
+  # Regex parsing loaded module constants
+  LOADED_MODULE_CHILD_CONSTANT_REGEXP = /^Mod(?<unpacked_full_name>[0-9a-f]+)$/
+  # Path to log holding leaked constants from last spec run.
+  LOG_PATHNAME = Pathname.new('log/leaked-constants.log')
   # The parent namespace constant that can have children added when loading modules.
   PARENT_CONSTANT = Msf::Modules
 
@@ -11,16 +15,62 @@ def self.configure!
     unless @configured
       RSpec.configure do |config|
         config.after(:suite) do
-          ::Metasploit::Framework::Spec::Constants.each { |child_name|
-            $stderr.puts "#{child_name} not removed from #{PARENT_CONSTANT}"
-          }
+          count = 0
+
+          LOG_PATHNAME.open('w') do |f|
+            count = ::Metasploit::Framework::Spec::Constants.each { |child_name|
+              f.puts child_name
+            }
+          end
+
+          if count > 0
+            $stderr.puts "#{count} #{'constant'.pluralize(count)} leaked under #{PARENT_CONSTANT}.  " \
+                         "See #{LOG_PATHNAME} for details."
+          else
+            LOG_PATHNAME.delete
+          end
         end
       end
 
       @configured = true
     end
   end
 
+  # Adds action to `spec` task so that `rake spec` fails if `log/leaked-constants.log` exists after printing out the
+  # leaked constants.
+  #
+  # @return [void]
+  def self.define_task
+    Rake::Task.define_task(:spec) do
+      if LOG_PATHNAME.exist?
+        $stderr.puts "Leaked constants detected under #{PARENT_CONSTANT}:"
+
+        LOG_PATHNAME.open do |f|
+          f.each_line do |line|
+            constant = line.strip
+            decoded = ''
+
+            match = LOADED_MODULE_CHILD_CONSTANT_REGEXP.match(constant)
+
+            if match
+              potential_full_name = [match[:unpacked_full_name]].pack('H*')
+
+              module_type, _reference_name = potential_full_name.split('/', 2)
+
+              if Msf::MODULE_TYPES.include? module_type
+                decoded = " # #{potential_full_name}"
+              end
+            end
+
+            $stderr.puts "  #{constant}#{decoded}"
+          end
+        end
+
+        exit 1
+      end
+    end
+  end
+
   # Yields each constant under {PARENT_CONSTANT}.
   #
   # @yield [child_name]