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import asyncio
import hashlib
import logging
import socket
import struct
import time
from typing import (
Any,
Callable,
Dict,
List,
Optional,
Text,
Tuple,
TypeVar,
Union,
cast,
)
from . import stun
from .utils import random_transaction_id
logger = logging.getLogger(__name__)
DEFAULT_CHANNEL_REFRESH_TIME = 500
DEFAULT_ALLOCATION_LIFETIME = 600
TCP_TRANSPORT = 0x06000000
UDP_TRANSPORT = 0x11000000
UDP_SOCKET_BUFFER_SIZE = 262144
_ProtocolT = TypeVar("_ProtocolT", bound=asyncio.BaseProtocol)
def is_channel_data(data: bytes) -> bool:
return (data[0] & 0xC0) == 0x40
def make_integrity_key(username: str, realm: str, password: str) -> bytes:
return hashlib.md5(":".join([username, realm, password]).encode("utf8")).digest()
class TurnStreamMixin:
datagram_received: Callable
transport: asyncio.BaseTransport
def data_received(self, data: bytes) -> None:
if not hasattr(self, "buffer"):
self.buffer = b""
self.buffer += data
while len(self.buffer) >= 4:
_, length = struct.unpack("!HH", self.buffer[0:4])
length += stun.padding_length(length)
if is_channel_data(self.buffer):
full_length = 4 + length
else:
full_length = 20 + length
if len(self.buffer) < full_length:
break
addr = self.transport.get_extra_info("peername")
self.datagram_received(self.buffer[0:full_length], addr)
self.buffer = self.buffer[full_length:]
def _padded(self, data: bytes) -> bytes:
# TCP and TCP-over-TLS must pad messages to 4-byte boundaries.
padding = stun.padding_length(len(data))
if padding:
data += bytes(padding)
return data
class TurnClientMixin:
_send: Callable
def __init__(
self,
server: Tuple[str, int],
username: Optional[str],
password: Optional[str],
lifetime: int,
channel_refresh_time: int,
) -> None:
self.channel_refresh_at: Dict[int, float] = {}
self.channel_to_peer: Dict[int, Tuple[str, int]] = {}
self.peer_connect_waiters: Dict[
Tuple[str, int], List[asyncio.Future[None]]
] = {}
self.peer_to_channel: Dict[Tuple[str, int], int] = {}
self.channel_number = 0x4000
self.channel_refresh_time = channel_refresh_time
self.integrity_key: Optional[bytes] = None
self.lifetime = lifetime
self.nonce: Optional[bytes] = None
self.password = password
self.receiver = None
self.realm: Optional[str] = None
self.refresh_task: Optional[asyncio.Task] = None
self.relayed_address: Optional[Tuple[str, int]] = None
self.server = server
self.transactions: Dict[bytes, stun.Transaction] = {}
self.username = username
async def channel_bind(self, channel_number: int, addr: Tuple[str, int]) -> None:
request = stun.Message(
message_method=stun.Method.CHANNEL_BIND, message_class=stun.Class.REQUEST
)
request.attributes["CHANNEL-NUMBER"] = channel_number
request.attributes["XOR-PEER-ADDRESS"] = addr
await self.request_with_retry(request)
logger.info("TURN channel bound %d %s", channel_number, addr)
async def connect(self) -> Tuple[str, int]:
"""
Create a TURN allocation.
"""
request = stun.Message(
message_method=stun.Method.ALLOCATE, message_class=stun.Class.REQUEST
)
request.attributes["LIFETIME"] = self.lifetime
request.attributes["REQUESTED-TRANSPORT"] = UDP_TRANSPORT
response, _ = await self.request_with_retry(request)
time_to_expiry = response.attributes["LIFETIME"]
self.relayed_address = response.attributes["XOR-RELAYED-ADDRESS"]
logger.info(
"TURN allocation created %s (expires in %d seconds)",
self.relayed_address,
time_to_expiry,
)
# periodically refresh allocation
self.refresh_task = asyncio.create_task(self.refresh(time_to_expiry))
return self.relayed_address
def connection_lost(self, exc: Exception) -> None:
logger.debug("%s connection_lost(%s)", self, exc)
if self.receiver:
self.receiver.connection_lost(exc)
def connection_made(self, transport) -> None:
logger.debug("%s connection_made(%s)", self, transport)
self.transport = transport
def datagram_received(self, data: Union[bytes, Text], addr) -> None:
data = cast(bytes, data)
# demultiplex channel data
if len(data) >= 4 and is_channel_data(data):
channel, length = struct.unpack("!HH", data[0:4])
if len(data) >= length + 4 and self.receiver:
peer_address = self.channel_to_peer.get(channel)
if peer_address:
payload = data[4 : 4 + length]
self.receiver.datagram_received(payload, peer_address)
return
try:
message = stun.parse_message(data)
logger.debug("%s < %s %s", self, addr, message)
except ValueError:
return
if (
message.message_class == stun.Class.RESPONSE
or message.message_class == stun.Class.ERROR
) and message.transaction_id in self.transactions:
transaction = self.transactions[message.transaction_id]
transaction.response_received(message, addr)
async def delete(self) -> None:
"""
Delete the TURN allocation.
"""
if self.refresh_task:
self.refresh_task.cancel()
self.refresh_task = None
request = stun.Message(
message_method=stun.Method.REFRESH, message_class=stun.Class.REQUEST
)
request.attributes["LIFETIME"] = 0
try:
await self.request_with_retry(request)
except stun.TransactionError:
# we do not care, we need to shutdown
pass
logger.info("TURN allocation deleted %s", self.relayed_address)
self.transport.close()
async def refresh(self, time_to_expiry) -> None:
"""
Periodically refresh the TURN allocation.
"""
while True:
await asyncio.sleep(5 / 6 * time_to_expiry)
request = stun.Message(
message_method=stun.Method.REFRESH, message_class=stun.Class.REQUEST
)
request.attributes["LIFETIME"] = self.lifetime
response, _ = await self.request_with_retry(request)
time_to_expiry = response.attributes["LIFETIME"]
logger.info(
"TURN allocation refreshed %s (expires in %d seconds)",
self.relayed_address,
time_to_expiry,
)
async def request(
self, request: stun.Message
) -> Tuple[stun.Message, Tuple[str, int]]:
"""
Execute a STUN transaction and return the response.
"""
assert request.transaction_id not in self.transactions
if self.integrity_key:
self.__add_authentication(request)
transaction = stun.Transaction(request, self.server, self)
self.transactions[request.transaction_id] = transaction
try:
return await transaction.run()
finally:
del self.transactions[request.transaction_id]
async def request_with_retry(
self, request: stun.Message
) -> Tuple[stun.Message, Tuple[str, int]]:
"""
Execute a STUN transaction and return the response.
On recoverable errors it will retry the request.
"""
try:
response, addr = await self.request(request)
except stun.TransactionFailed as e:
error_code = e.response.attributes["ERROR-CODE"][0]
if (
"NONCE" in e.response.attributes
and self.username is not None
and self.password is not None
and (
(error_code == 401 and "REALM" in e.response.attributes)
or (error_code == 438 and self.realm is not None)
)
):
# update long-term credentials
self.nonce = e.response.attributes["NONCE"]
if error_code == 401:
self.realm = e.response.attributes["REALM"]
self.integrity_key = make_integrity_key(
self.username, self.realm, self.password
)
# retry request with authentication
request.transaction_id = random_transaction_id()
response, addr = await self.request(request)
else:
raise
return response, addr
async def send_data(self, data: bytes, addr: Tuple[str, int]) -> None:
"""
Send data to a remote host via the TURN server.
"""
# if a channel is being bound for the peer, wait
if addr in self.peer_connect_waiters:
loop = asyncio.get_event_loop()
waiter = loop.create_future()
self.peer_connect_waiters[addr].append(waiter)
await waiter
channel = self.peer_to_channel.get(addr)
now = time.time()
if channel is None:
self.peer_connect_waiters[addr] = []
channel = self.channel_number
self.channel_number += 1
# bind channel
await self.channel_bind(channel, addr)
# update state
self.channel_refresh_at[channel] = now + self.channel_refresh_time
self.channel_to_peer[channel] = addr
self.peer_to_channel[addr] = channel
# notify waiters
for waiter in self.peer_connect_waiters.pop(addr):
waiter.set_result(None)
elif now > self.channel_refresh_at[channel]:
# refresh channel
await self.channel_bind(channel, addr)
# update state
self.channel_refresh_at[channel] = now + self.channel_refresh_time
header = struct.pack("!HH", channel, len(data))
self._send(header + data)
def send_stun(self, message: stun.Message, addr: Tuple[str, int]) -> None:
"""
Send a STUN message to the TURN server.
"""
logger.debug("%s > %s %s", self, addr, message)
self._send(bytes(message))
def __add_authentication(self, request: stun.Message) -> None:
request.attributes["USERNAME"] = self.username
request.attributes["NONCE"] = self.nonce
request.attributes["REALM"] = self.realm
request.add_message_integrity(self.integrity_key)
class TurnClientTcpProtocol(TurnClientMixin, TurnStreamMixin, asyncio.Protocol):
"""
Protocol for handling TURN over TCP.
"""
def _send(self, data: bytes) -> None:
self.transport.write(self._padded(data))
def __repr__(self) -> str:
return "turn/tcp"
class TurnClientUdpProtocol(TurnClientMixin, asyncio.DatagramProtocol):
"""
Protocol for handling TURN over UDP.
"""
def _send(self, data: bytes) -> None:
self.transport.sendto(data)
def __repr__(self) -> str:
return "turn/udp"
class TurnTransport:
"""
Behaves like a Datagram transport, but uses a TURN allocation.
"""
def __init__(self, protocol, inner_protocol) -> None:
self.protocol = protocol
self.__inner_protocol = inner_protocol
self.__inner_protocol.receiver = protocol
self.__relayed_address = None
def close(self) -> None:
"""
Close the transport.
After the TURN allocation has been deleted, the protocol's
`connection_lost()` method will be called with None as its argument.
"""
asyncio.create_task(self.__inner_protocol.delete())
def get_extra_info(self, name: str, default: Any = None) -> Any:
"""
Return optional transport information.
- `'related_address'`: the related address
- `'sockname'`: the relayed address
"""
if name == "related_address":
return self.__inner_protocol.transport.get_extra_info("sockname")
elif name == "sockname":
return self.__relayed_address
return default
def sendto(self, data: bytes, addr: Tuple[str, int]) -> None:
"""
Sends the `data` bytes to the remote peer given `addr`.
This will bind a TURN channel as necessary.
"""
asyncio.create_task(self.__inner_protocol.send_data(data, addr))
async def _connect(self) -> None:
self.__relayed_address = await self.__inner_protocol.connect()
self.protocol.connection_made(self)
async def create_turn_endpoint(
protocol_factory: Callable[[], _ProtocolT],
server_addr: Tuple[str, int],
username: Optional[str],
password: Optional[str],
lifetime: int = DEFAULT_ALLOCATION_LIFETIME,
channel_refresh_time: int = DEFAULT_CHANNEL_REFRESH_TIME,
ssl: bool = False,
transport: str = "udp",
) -> Tuple[TurnTransport, _ProtocolT]:
"""
Create datagram connection relayed over TURN.
"""
loop = asyncio.get_event_loop()
inner_protocol: asyncio.BaseProtocol
inner_transport: asyncio.BaseTransport
if transport == "tcp":
inner_transport, inner_protocol = await loop.create_connection(
lambda: TurnClientTcpProtocol(
server_addr,
username=username,
password=password,
lifetime=lifetime,
channel_refresh_time=channel_refresh_time,
),
host=server_addr[0],
port=server_addr[1],
ssl=ssl,
)
else:
inner_transport, inner_protocol = await loop.create_datagram_endpoint(
lambda: TurnClientUdpProtocol(
server_addr,
username=username,
password=password,
lifetime=lifetime,
channel_refresh_time=channel_refresh_time,
),
remote_addr=server_addr,
)
sock = inner_transport.get_extra_info("socket")
if sock is not None:
sock.setsockopt(socket.SOL_SOCKET, socket.SO_RCVBUF, UDP_SOCKET_BUFFER_SIZE)
try:
protocol = protocol_factory()
turn_transport = TurnTransport(protocol, inner_protocol)
await turn_transport._connect()
except Exception:
inner_transport.close()
raise
return turn_transport, protocol
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