First, copy-pasta and add a test

Author: Tod Beardsley

lib/msf/base/simple/auxiliary.rb

@@ -92,6 +92,39 @@ def run_simple(opts = {}, &block)
 		Msf::Simple::Auxiliary.run_simple(self, opts, &block)
 	end
 
+	#
+	# Initiates a check, setting up the exploit to be used.  The following
+	# options can be specified:
+	#
+	# LocalInput
+	#
+	# 	The local input handle that data can be read in from.
+	#
+	# LocalOutput
+	#
+	# 	The local output through which data can be displayed.
+	#
+	def self.check_simple(mod, opts)
+		if opts['LocalInput']
+			mod.init_ui(opts['LocalInput'], opts['LocalOutput'])
+		end
+
+		# Validate the option container state so that options will
+		# be normalized
+		mod.validate
+
+		# Run check
+		mod.check
+	end
+
+	#
+	# Calls the class method.
+	#
+	def check_simple(opts)
+		Msf::Simple::Auxiliary.check_simple(self, opts)
+	end
+
+
 protected
 
 	#

lib/msf/core/auxiliary.rb

@@ -44,6 +44,16 @@ def initialize(info = {})
 		self.queue   = Array.new
 	end
 
+	#
+	# Checks to see if the target is vulnerable, returning unsupported if it's
+	# not supported.
+	#
+	# This method is designed to be overriden by exploit modules.
+	#
+	def check
+		Msf::Exploit::CheckCode::Unsupported
+	end
+
 	#
 	# Creates a singleton instance of this auxiliary class
 	#

lib/msf/ui/console/command_dispatcher/auxiliary.rb

@@ -27,6 +27,7 @@ class Auxiliary
 	#
 	def commands
 		super.update({
+			"check"    => "Check to see if a target is vulnerable",
 			"run"   => "Launches the auxiliary module",
 			"rerun" => "Reloads and launches the auxiliary module",
 			"exploit" => "This is an alias for the run command",
@@ -57,6 +58,45 @@ def name
 		"Auxiliary"
 	end
 
+	#
+	# Checks to see if a target is vulnerable.
+	#
+	def cmd_check(*args)
+		defanged?
+
+		begin
+
+			code = mod.check_simple(
+				'LocalInput'  => driver.input,
+				'LocalOutput' => driver.output)
+
+			if (code and code.kind_of?(Array) and code.length > 1)
+
+				if (code == Msf::Exploit::CheckCode::Vulnerable)
+					print_good(code[1])
+				else
+					print_status(code[1])
+				end
+
+			else
+				print_error("Check failed: The state could not be determined.")
+			end
+
+		rescue ::Interrupt
+			raise $!
+		rescue ::Exception => e
+			print_error("Module check failed: #{e.class} #{e}")
+			if(e.class.to_s != 'Msf::OptionValidateError')
+				print_error("Call stack:")
+				e.backtrace.each do |line|
+					break if line =~ /lib.msf.base.simple/
+					print_error("  #{line}")
+				end
+			end
+		end
+	end
+
+
 	#
 	# Reloads an auxiliary module and executes it
 	#

test/modules/auxiliary/test/check.rb

@@ -0,0 +1,47 @@
+##
+# This file is part of the Metasploit Framework and may be subject to
+# redistribution and commercial restrictions. Please see the Metasploit
+# Framework web site for more information on licensing and terms of use.
+#   http://metasploit.com/framework/
+##
+
+require 'msf/core'
+
+class Metasploit3 < Msf::Auxiliary
+
+	include Msf::Auxiliary::Report
+	include Msf::Exploit::Remote::HttpClient
+
+	def initialize(info = {})
+		super(update_info(info,
+			'Name'           => "Check Test",
+			'Description'    => %q{
+					This module ensures that 'check' actually functions for Auxiilary modules.
+			},
+			'References'     =>
+				[
+					[ 'OSVDB', '0' ]
+				],
+			'Author'         =>
+				[
+					'todb'
+				],
+			'License'        => MSF_LICENSE
+		))
+
+		register_options(
+			[
+				Opt::RPORT(80)
+			], self.class)
+	end
+
+	def check
+		print_debug "Check is successful"
+		return Msf::Exploit::CheckCode::Vulnerable
+	end
+
+	def run
+		print_debug "Run is successful."
+	end
+
+end

test/scripts/test-check.rc

@@ -0,0 +1,7 @@
+# Usage:
+# msfconsole -qLm test/modules -r test/scripts/test-check.rc
+
+use auxiliary/test/check
+set rhost www.metasploit.com
+check
+exit