Pymet fix transport automatic roll over

data/meterpreter/meterpreter.py

@@ -469,8 +469,9 @@ class Transport(object):
 			pkt = self._get_packet()
 		except:
 			return None
+		if pkt is None:
+			return None
 		self.communication_last = time.time()
-		if pkt:
 		self.communication_active = True
 		return pkt
 
@@ -536,11 +537,13 @@ class HttpTransport(Transport):
 		request = urllib.Request(self.url, bytes('RECV', 'UTF-8'), self._http_request_headers)
 		url_h = urllib.urlopen(request, timeout=self.communication_timeout)
 		packet = url_h.read()
-		if not packet or len(packet) < 8:
+		if packet == '':
-			return None
+			return ''
+		if len(packet) < 8:
+			return None  # looks corrupt
 		pkt_length, _ = struct.unpack('>II', packet[:8])
 		if len(packet) != pkt_length:
-			return None
+			return None  # looks corrupt
 		return packet[8:]
 
 	def _send_packet(self, packet):
@@ -609,11 +612,13 @@ class TcpTransport(Transport):
 		self.socket = None
 
 	def _get_packet(self):
-		packet = None
 		first = self._first_packet
 		self._first_packet = False
-		if select.select([self.socket], [], [], 0.5)[0]:
+		if not select.select([self.socket], [], [], 0.5)[0]:
+			return ''
 		packet = self.socket.recv(8)
+		if packet == '':  # remote is closed
+			return None
 		if len(packet) != 8:
 			if first and len(packet) == 4:
 				received = 0