Merge pull request #30 from Bluetooth-Devices/fix-remove-cipher-update

feat: remove cipher update

Author: Ernst79

src/bthome_ble/bthome_v2_encryption.py

@@ -26,7 +26,6 @@ def decrypt_payload(
     print("CryptData:", payload.hex())
     print("Mic:", mic.hex())
     cipher = AES.new(key, AES.MODE_CCM, nonce=nonce, mac_len=4)
-    cipher.update(b"\x11")
     print()
     print("Starting Decryption data")
     try:
@@ -71,7 +70,6 @@ def encrypt_payload(
     """Encrypt payload."""
     nonce = b"".join([mac, uuid16, sw_version, count_id])  # 6+2+1+4 = 13 bytes
     cipher = AES.new(key, AES.MODE_CCM, nonce=nonce, mac_len=4)
-    cipher.update(b"\x11")
     ciphertext, mic = cipher.encrypt_and_digest(data)
     print("MAC:", mac.hex())
     print("Binkey:", key.hex())
@@ -96,7 +94,7 @@ def main() -> None:
     count_id = bytes(bytearray.fromhex("00112233"))  # count id (change every message)
     mac = binascii.unhexlify("5448E68F80A5")  # MAC
     uuid16 = b"\xD2\xFC"
-    sw_version = b"\x42"
+    sw_version = b"\x41"
     bindkey = binascii.unhexlify("231d39c1d7cc1ab1aee224cd096db932")
 
     payload = encrypt_payload(

src/bthome_ble/parser.py

@@ -493,7 +493,8 @@ def _decrypt_bthome(self, data: bytes, bthome_mac: bytes, sw_version: int) -> by
         # nonce: mac [6], uuid16 [2 (v1) or 3 (v2)], count_id [4]
         nonce = b"".join([bthome_mac, uuid, count_id])
         cipher = AES.new(self.bindkey, AES.MODE_CCM, nonce=nonce, mac_len=4)
-        cipher.update(b"\x11")
+        if sw_version == 1:
+            cipher.update(b"\x11")
 
         # decrypt the data
         try:

tests/test_parser_v2.py

@@ -221,7 +221,7 @@ def test_bindkey_wrong():
 def test_bindkey_correct():
     """Test BTHome parser with correct encryption key."""
     bindkey = "231d39c1d7cc1ab1aee224cd096db932"
-    data_string = b"\x41\xa4\x72\x66\xc9\x5f\x73\x00\x11\x22\x33\xb7\xce\xd8\xe5"
+    data_string = b"\x41\xa4\x72\x66\xc9\x5f\x73\x00\x11\x22\x33\x78\x23\x72\x14"
     advertisement = bytes_to_service_info(
         data_string,
         local_name="TEST DEVICE",
@@ -276,7 +276,7 @@ def test_bindkey_correct():
 def test_bindkey_verified_can_be_unset():
     """Test BTHome parser with wrong encryption key."""
     bindkey = "814aac74c4f17b6c1581e1ab87816b99"
-    data_string = b'\x41\xfb\xa45\xe4\xd3\xc3\x12\xfb\x00\x11"3W\xd9\n\x99'
+    data_string = b"\x41\xa4\x72\x66\xc9\x5f\x73\x00\x11\x22\x33\x78\x23\x72\x14"
     advertisement = bytes_to_service_info(
         data_string,
         local_name="ATC_8D18B2",

tests/test_v2_encryption.py

@@ -10,7 +10,7 @@ def test_encryption_example():
     count_id = bytes(bytearray.fromhex("00112233"))  # count id (change every message)
     mac = binascii.unhexlify("5448E68F80A5")  # MAC
     uuid16 = b"\xd2\xfc"
-    sw_version = b"\x42"
+    sw_version = b"\x41"
     bindkey = binascii.unhexlify("231d39c1d7cc1ab1aee224cd096db932")
 
     encrypted_payload = encrypt_payload(
@@ -23,7 +23,7 @@ def test_encryption_example():
     )
     assert (
         encrypted_payload
-        == b"\xd2\xfc\x42\x69\x6c\x8c\x91\x85\x6f\x00\x11\x22\x33\x04\x5b\xbc\x2a"
+        == b"\xd2\xfc\x41\xa4\x72\x66\xc9\x5f\x73\x00\x11\x22\x33\x78\x23\x72\x14"
     )
     assert decrypt_aes_ccm(key=bindkey, mac=mac, data=encrypted_payload) == {
         "humidity": 50.55,