def header_protection_mask(self, sample: bytes) -> bytes:
if self.cipher_suite == CipherSuite.CHACHA20_POLY1305_SHA256:
encryptor = Cipher(
algorithms.ChaCha20(key=self.hp, nonce=sample),
mode=None,
backend=default_backend(),
).encryptor()
buf = bytearray(5)
encryptor.update_into(bytes(5), buf)
return bytes(buf)
else:
encryptor = Cipher(algorithms.AES(self.hp),
mode=modes.ECB(),
backend=default_backend()).encryptor()
buf = bytearray(31)
encryptor.update_into(sample, buf)
return buf[:5]
def encrypt(mode, key, iv, inputBytes):
backend = default_backend()
encryptor = Cipher(algorithms.AES(key), mode, backend=backend).encryptor()
if isinstance(mode, modes.CBC):
length = ceil(len(inputBytes) / AES_BLOCK_SIZE) * AES_BLOCK_SIZE
else:
length = len(inputBytes) + AES_BLOCK_SIZE - 1
buf = bytearray(length)
lenEncrypted = encryptor.update_into(inputBytes, buf)
ct = bytes(buf[:lenEncrypted]) + encryptor.finalize()
return ct
def decrypt_packet(data):
data = bytearray(data)
data_len = len(data)
offset = 0
if data[4] not in IQUIC.VERSIONS:
return None
salt = IQUIC.QUIC_VERSION_PARAMETERS[data[4]]['salt']
offset = 5
dcid_len = data[offset]
dcid = data[offset + 1:offset + 1 + dcid_len]
offset += 1 + dcid_len
if offset >= data_len:
return None
scid_len = data[offset]
scid = data[offset + 1:offset + 1 + scid_len]
offset += 1 + scid_len
if offset >= data_len:
return None
token_len = data[offset]
token = data[offset + 1:offset + 1 + token_len]
offset += 2 + token_len
if offset >= data_len:
return None
initial_secret = IQUIC.hmac(salt, SHA256(), dcid)
client_initial_secret = IQUIC.kdf_tls13(initial_secret, b'client in',
32)
key = IQUIC.kdf_tls13(client_initial_secret, b'quic key', 16)
iv = IQUIC.kdf_tls13(client_initial_secret, b'quic iv', 12)
hp = IQUIC.kdf_tls13(client_initial_secret, b'quic hp', 16)
hp_encryptor = Cipher(algorithms.AES(hp),
mode=modes.ECB(),
backend=default_backend()).encryptor()
buf = bytearray(31)
sample = data[offset + 4:offset + 4 + IQUIC.SAMPLE_SIZE]
hp_encryptor.update_into(sample, buf)
mask = buf[:5]
data[0] ^= mask[0] & 0x0F
pn_length = (data[0] & 0x03) + 1
if offset + pn_length >= data_len:
return None
for i in range(pn_length):
data[offset + i] ^= mask[1 + i]
pn = data[offset:offset + pn_length]
plain_header = data[:offset + pn_length]
nonce = bytearray(len(iv) - pn_length) + bytearray(pn)
for i in range(len(iv)):
nonce[i] ^= iv[i]
cipher = Cipher(AES(key), GCM(iv), backend=default_backend())
payload = cipher.decryptor().update(bytes(data[offset + pn_length:]))
return payload[4:]
