Refactor ssh connection within class for future improvements.

ssh-audit.py

@@ -27,8 +27,6 @@ from __future__ import print_function
 import os, io, sys, socket, struct
 
 SSH_BANNER = 'SSH-2.0-OpenSSH_7.2'
-SOCK_CONN_TIMEOUT = 3.0
-SOCK_READ_TIMEOUT = 5.0
 
 def usage():
 	p = os.path.basename(sys.argv[0])
@@ -95,6 +93,7 @@ class Kex(object):
 
 class ReadBuf(object):
 	def __init__(self, data = None):
+		super(ReadBuf, self).__init__()
 		self._buf = io.BytesIO(data) if data else io.BytesIO()
 		self._len = len(data) if data else 0
 	
@@ -118,19 +117,69 @@ class ReadBuf(object):
 		list_size = self.read_int()
 		return self.read(list_size).decode().split(',')
 
-class SockBuf(ReadBuf):
-	def __init__(self, s):
-		super(SockBuf, self).__init__()
-		self.__sock = s
+class SSH(object):
+	MSG_KEXINIT     = 20
+	MSG_NEWKEYS     = 21
+	MSG_KEXDH_INIT  = 30
+	MSG_KEXDH_REPLY = 32
 	
-	def recv(self, size = 2048):
-		data = self.__sock.recv(size)
-		pos = self._buf.tell()
-		self._buf.seek(0, 2)
-		self._buf.write(data)
-		self._len += len(data)
-		self._buf.seek(pos, 0)
+	class Socket(ReadBuf):
+		def __init__(self, host, port, cto = 3.0, rto = 5.0):
+			super(SSH.Socket, self).__init__()
+			try:
+				self.__sock = socket.create_connection((host, port), cto)
+				self.__sock.settimeout(rto)
+			except Exception as e:
+				out.fail('[fail] {}'.format(e))
+				sys.exit(1)
 		
+		def __enter__(self):
+			return self
+		
+		def recv(self, size = 2048):
+			data = self.__sock.recv(size)
+			pos = self._buf.tell()
+			self._buf.seek(0, 2)
+			self._buf.write(data)
+			self._len += len(data)
+			self._buf.seek(pos, 0)
+		
+		def send(self, data):
+			self.__sock.send(data)
+		
+		def read_packet(self):
+			block_size = 8
+			if self.unread_len < block_size:
+				self.recv()
+			header = self.read(block_size)
+			packet_size = struct.unpack('>I', header[:4])[0]
+			rest = header[4:]
+			lrest = len(rest)
+			padding = ord(rest[0:1])
+			packet_type = ord(rest[1:2])
+			if (packet_size - lrest) % block_size != 0:
+				out.fail('[exception] invalid ssh packet (block size)')
+				sys.exit(1)
+			rlen = packet_size - lrest
+			if self.unread_len < rlen:
+				self.recv()
+			buf = self.read(rlen)
+			packet = rest[2:] + buf[0:packet_size - lrest]
+			payload = packet[0:packet_size - padding]
+			return packet_type, payload
+		
+		def __del__(self):
+			self.__cleanup()
+		
+		def __exit__(self, ex_type, ex_value, tb):
+			self.__cleanup()
+		
+		def __cleanup(self):
+			try:
+				self.__sock.shutdown(socket.SHUT_RDWR)
+				self.__sock.close()
+			except:
+				pass
 
 def get_ssh_ver(versions):
 	tv = []
@@ -309,26 +358,6 @@ def process_kex(kex):
 	process_algorithms('mac', kex.server.mac, maxlen)
 	out.sep()
 
-def read_ssh_packet(sbuf):
-	block_size = 8
-	if sbuf.unread_len < block_size:
-		sbuf.recv()
-	header = sbuf.read(block_size)
-	packet_size = struct.unpack('>I', header[:4])[0]
-	rest = header[4:]
-	lrest = len(rest)
-	padding = ord(rest[0:1])
-	packet_type = ord(rest[1:2])
-	if (packet_size - lrest) % block_size != 0:
-		out.fail('[exception] invalid ssh packet (block size)')
-		sys.exit(1)
-	rlen = packet_size - lrest
-	if sbuf.unread_len < rlen:
-		sbuf.recv()
-	buf = sbuf.read(rlen)
-	packet = rest[2:] + buf[0:packet_size - lrest]
-	payload = packet[0:packet_size - padding]
-	return packet_type, payload
 
 def parse_int(v):
 	try:
@@ -355,30 +384,20 @@ def parse_args():
 
 def main():
 	host, port = parse_args()
-	s = None
-	try:
-		s = socket.create_connection((host, port), SOCK_CONN_TIMEOUT)
-		s.settimeout(SOCK_READ_TIMEOUT)
-		sbuf = SockBuf(s)
-		s.send(SSH_BANNER.encode() + b'\r\n')
-		sbuf.recv()
-		banner = sbuf.read_line()
-		out.head('# general')
-		out.good('[info] banner: ' + banner)
-		if banner.startswith('SSH-1.99-'):
-			out.fail('[fail] protocol SSH1 enabled')
-		packet_type, payload = read_ssh_packet(sbuf)
-		if packet_type != 20:
-			out.fail('[exception] did not receive MSG_KEXINIT (20), instead received unknown message ({0})'.format(packet_type))
-			sys.exit(1)
-		kex = Kex.parse(payload)
-		process_kex(kex)
-	except Exception as e:
-		out.fail('[fail] {}'.format(e))
+	s = SSH.Socket(host, port)
+	s.send(SSH_BANNER.encode() + b'\r\n')
+	s.recv()
+	banner = s.read_line()
+	out.head('# general')
+	out.good('[info] banner: ' + banner)
+	if banner.startswith('SSH-1.99-'):
+		out.fail('[fail] protocol SSH1 enabled')
+	packet_type, payload = s.read_packet()
+	if packet_type != SSH.MSG_KEXINIT:
+		out.fail('[exception] did not receive MSG_KEXINIT (20), instead received unknown message ({0})'.format(packet_type))
 		sys.exit(1)
-	finally:
-		if s:
-			s.close()
+	kex = Kex.parse(payload)
+	process_kex(kex)
 
 if __name__ == '__main__':
 	out = Output()