split hcpy into HCSocket and restore HTTPS PSK support as well

HCSocket.py

@@ -0,0 +1,166 @@
+# Create a websocket that wraps a connection to a
+# Bosh-Siemens Home Connect device
+import socket
+import ssl
+import sslpsk
+import websocket
+import sys
+import json
+import re
+import time
+import io
+from base64 import urlsafe_b64decode as base64url
+from datetime import datetime
+from Crypto.Cipher import AES
+from Crypto.Hash import HMAC, SHA256
+from Crypto.Random import get_random_bytes
+
+# Convience to compute an HMAC on a message
+def hmac(key,msg):
+	mac = HMAC.new(key, msg=msg, digestmod=SHA256).digest()
+	return mac
+
+def now():
+	return datetime.now().strftime("%Y-%m-%d %H:%M:%S.%f")
+
+# Monkey patch for sslpsk in pip using the old _sslobj
+def _sslobj(sock):
+    if (3, 5) <= sys.version_info <= (3, 7):
+        return sock._sslobj._sslobj
+    else:
+        return sock._sslobj
+sslpsk.sslpsk._sslobj = _sslobj
+
+
+class HCSocket:
+	def __init__(self, host, psk64, iv64=None):
+		self.host = host
+		self.psk = base64url(psk64 + '===')
+
+		if iv64:
+			# an HTTP self-encrypted socket
+			self.http = True
+			self.iv = base64url(iv64 + '===')
+			self.enckey = hmac(self.psk, b'ENC')
+			self.mackey = hmac(self.psk, b'MAC')
+			self.port = 80
+			self.uri = "ws://" + host + ":80/homeconnect"
+		else:
+			self.http = False
+			self.port = 443
+			self.uri = "wss://" + host + ":443/homeconnect"
+
+		self.reconnect()
+
+	# restore the encryption state for a fresh connection
+	# this is only used by the HTTP connection
+	def reset(self):
+		if not self.http:
+			return
+		self.last_rx_hmac = bytes(16)
+		self.last_tx_hmac = bytes(16)
+
+		self.aes_encrypt = AES.new(self.enckey, AES.MODE_CBC, self.iv)
+		self.aes_decrypt = AES.new(self.enckey, AES.MODE_CBC, self.iv)
+
+	# hmac an inbound or outbound message, chaining the last hmac too
+	def hmac_msg(self, direction, enc_msg):
+		hmac_msg = self.iv + direction + enc_msg
+		return hmac(self.mackey, hmac_msg)[0:16]
+
+	def decrypt(self,buf):
+		if len(buf) < 32:
+			print("Short message?", buf.hex(), file=sys.stderr)
+			return None
+		if len(buf) % 16 != 0:
+			print("Unaligned message? probably bad", buf.hex(), file=sys.stderr)
+
+		# split the message into the encrypted message and the first 16-bytes of the HMAC
+		enc_msg = buf[0:-16]
+		their_hmac = buf[-16:]
+
+		# compute the expected hmac on the encrypted message
+		our_hmac = self.hmac_msg(b'\x43' + self.last_rx_hmac, enc_msg)
+
+		if their_hmac != our_hmac:
+			print("HMAC failure", their_hmac.hex(), our_hmac.hex(), file=sys.stderr)
+			return None
+
+		self.last_rx_hmac = their_hmac
+
+		# decrypt the message with CBC, so the last message block is mixed in
+		msg = self.aes_decrypt.decrypt(enc_msg)
+
+		# check for padding and trim it off the end
+		pad_len = msg[-1]
+		if len(msg) < pad_len:
+			print("padding error?", msg.hex())
+			return None
+
+		return msg[0:-pad_len]
+
+	def encrypt(self, clear_msg):
+		# convert the UTF-8 string into a byte array
+		clear_msg = bytes(clear_msg, 'utf-8')
+
+		# pad the buffer, adding an extra block if necessary
+		pad_len = 16 - (len(clear_msg) % 16)
+		if pad_len == 1:
+			pad_len += 16
+		pad = b'\x00' + get_random_bytes(pad_len-2) + bytearray([pad_len])
+
+		clear_msg = clear_msg + pad
+
+		# encrypt the padded message with CBC, so there is chained
+		# state from the last cipher block sent
+		enc_msg = self.aes_encrypt.encrypt(clear_msg)
+
+		# compute the hmac of the encrypted message, chaining the
+		# hmac of the previous message plus direction 'E'
+		self.last_tx_hmac = self.hmac_msg(b'\x45' + self.last_tx_hmac, enc_msg)
+
+		# append the new hmac to the message
+		return enc_msg + self.last_tx_hmac
+
+	def reconnect(self):
+		self.reset()
+		sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+		sock.connect((self.host,self.port))
+
+		if not self.http:
+			sock = sslpsk.wrap_socket(
+				sock,
+				ssl_version = ssl.PROTOCOL_TLSv1_2,
+				ciphers = 'ECDHE-PSK-CHACHA20-POLY1305',
+				psk = self.psk,
+			)
+
+		print(now(), "CON:", self.uri)
+		self.ws = websocket.WebSocket()
+		self.ws.connect(self.uri,
+			socket = sock,
+			origin = "",
+		)
+
+	def send(self, msg):
+		print(now(), "TX:", msg)
+		buf = json.dumps(msg, separators=(',', ':') )
+		# swap " for '
+		buf = re.sub("'", '"', buf)
+		if self.http:
+			self.ws.send_binary(self.encrypt(buf))
+		else:
+			self.ws.send(buf)
+
+	def recv(self):
+		buf = self.ws.recv()
+		if buf is None or buf == "":
+			return None
+
+		if self.http:
+			buf = self.decrypt(buf)
+		if buf is None:
+			return None
+
+		print(now(), "RX:", buf)
+		return buf