Ensure Windows single payloads use payload backend

This means the singles that define their own assembly will use the payload backend to generate it.

Author: scriptjunkie

lib/msf/core/payload.rb

@@ -185,6 +185,15 @@ def assembly
 		return module_info['Payload'] ? module_info['Payload']['Assembly'] : nil
 	end
 
+	#
+	# Sets the assembly string that describes the payload
+	# If this method is used to define the payload, a payload with no offsets will be created
+	#
+	def assembly=(asm)
+		module_info['Payload'] ||= {'Offsets' => {} }
+		module_info['Payload']['Assembly'] = asm
+	end
+
 	#
 	# Returns the offsets to variables that must be substitute, if any.
 	#

modules/payloads/singles/windows/dns_txt_query_exec.rb

@@ -253,6 +253,7 @@ def generate
 
 
 EOS
-		the_payload = Metasm::Shellcode.assemble(Metasm::Ia32.new, payload_data).encode_string
+		self.assembly = payload_data
+		super
 	end
 end

modules/payloads/singles/windows/download_exec.rb

@@ -387,6 +387,7 @@ def generate
 	db "#{server_host}", 0x00
 end:
 EOS
-		the_payload = Metasm::Shellcode.assemble(Metasm::Ia32.new, payload_data).encode_string
+		self.assembly = payload_data
+		super
 	end
 end

modules/payloads/singles/windows/messagebox.rb

@@ -266,7 +266,8 @@ def generate
 ;EXITFUNC
 	#{doexit}
 EOS
-		the_payload = Metasm::Shellcode.assemble(Metasm::Ia32.new, payload_data).encode_string
+		self.assembly = payload_data
+		super
 	end
 
 	#