Don't blow up if the user doesn't set a filename

Can't actually require FILENAME or REMOTE_FILENAME because I don't know
if you're going to upload or download. However, there shouldn't be a
stacktrace when you just try to go with neither.

lib/rex/proto/tftp/client.rb

@@ -54,7 +54,7 @@ class Client
 		self.peer_port = params["PeerPort"] || 69
 		self.context = params["Context"] || {}
 		self.local_file = params["LocalFile"]
-		self.remote_file = params["RemoteFile"] || ::File.split(self.local_file).last
+		self.remote_file = params["RemoteFile"] || (::File.split(self.local_file).last if self.local_file)
 		self.mode = params["Mode"] || "octet"
 		self.action = params["Action"] || (raise ArgumentError, "Need an action.")
 		self.block_size = params["BlockSize"] || 512

modules/auxiliary/admin/tftp/tftp_transfer_util.rb

@@ -60,7 +60,8 @@ class Metasploit3 < Msf::Auxiliary
 	end
 
 	def remote_file
-		datastore['REMOTE_FILENAME'] || ::File.split(datastore['FILENAME']).last
+		return datastore['REMOTE_FILENAME'] if datastore['REMOTE_FILENAME']
+		return ::File.split(datastore['FILENAME']).last if datastore['FILENAME']
 	end
 
 	def rport
@@ -138,8 +139,24 @@ class Metasploit3 < Msf::Auxiliary
 	end
 
 	def run
-		run_upload()   if action.name == 'Upload'
-		run_download() if action.name == 'Download'
+		case action.name
+		when 'Upload'
+			if file
+				run_upload()
+			else
+				print_error "Need at least a local file name or file data to upload."
+				return
+			end
+		when 'Download'
+			if remote_file
+				run_download()
+			else
+				print_error "Need at least a remote file name to download."
+				return
+			end
+		else
+			print_error "Unknown action: '#{action.name}'"
+		end
 		while not @tftp_client.complete
 			select(nil,nil,nil,1)
 			print_status [rtarget,"TFTP transfer operation complete."].join