import functools import logging import time from typing import ( TYPE_CHECKING, Callable, Dict, KeysView, List, NamedTuple, Set, Tuple, cast, ) from async_service import Service import base58 from lru import LRU import trio from libp2p.crypto.keys import PrivateKey from libp2p.exceptions import ParseError, ValidationError from libp2p.host.host_interface import IHost from libp2p.io.exceptions import IncompleteReadError from libp2p.network.exceptions import SwarmException from libp2p.network.stream.exceptions import StreamClosed, StreamEOF, StreamReset from libp2p.network.stream.net_stream_interface import INetStream from libp2p.peer.id import ID from libp2p.typing import TProtocol from libp2p.utils import encode_varint_prefixed, read_varint_prefixed_bytes from .abc import IPubsub, ISubscriptionAPI from .pb import rpc_pb2 from .pubsub_notifee import PubsubNotifee from .subscription import TrioSubscriptionAPI from .typing import AsyncValidatorFn, SyncValidatorFn, ValidatorFn from .validators import PUBSUB_SIGNING_PREFIX, signature_validator if TYPE_CHECKING: from .abc import IPubsubRouter # noqa: F401 from typing import Any # noqa: F401 # Ref: https://github.com/libp2p/go-libp2p-pubsub/blob/40e1c94708658b155f30cf99e4574f384756d83c/topic.go#L97 # noqa: E501 SUBSCRIPTION_CHANNEL_SIZE = 32 logger = logging.getLogger("libp2p.pubsub") def get_peer_and_seqno_msg_id(msg: rpc_pb2.Message) -> bytes: # NOTE: `string(from, seqno)` in Go return msg.seqno + msg.from_id class TopicValidator(NamedTuple): validator: ValidatorFn is_async: bool class Pubsub(Service, IPubsub): host: IHost router: "IPubsubRouter" peer_receive_channel: "trio.MemoryReceiveChannel[ID]" dead_peer_receive_channel: "trio.MemoryReceiveChannel[ID]" seen_messages: LRU subscribed_topics_send: Dict[str, "trio.MemorySendChannel[rpc_pb2.Message]"] subscribed_topics_receive: Dict[str, "TrioSubscriptionAPI"] peer_topics: Dict[str, Set[ID]] peers: Dict[ID, INetStream] topic_validators: Dict[str, TopicValidator] counter: int # uint64 # Indicate if we should enforce signature verification strict_signing: bool sign_key: PrivateKey event_handle_peer_queue_started: trio.Event event_handle_dead_peer_queue_started: trio.Event def __init__( self, host: IHost, router: "IPubsubRouter", cache_size: int = None, strict_signing: bool = True, msg_id_constructor: Callable[ [rpc_pb2.Message], bytes ] = get_peer_and_seqno_msg_id, ) -> None: """ Construct a new Pubsub object, which is responsible for handling all Pubsub-related messages and relaying messages as appropriate to the Pubsub router (which is responsible for choosing who to send messages to). Since the logic for choosing peers to send pubsub messages to is in the router, the same Pubsub impl can back floodsub, gossipsub, etc. """ self.host = host self.router = router self._msg_id_constructor = msg_id_constructor # Attach this new Pubsub object to the router self.router.attach(self) peer_send, peer_receive = trio.open_memory_channel[ID](0) dead_peer_send, dead_peer_receive = trio.open_memory_channel[ID](0) # Only keep the receive channels in `Pubsub`. # Therefore, we can only close from the receive side. self.peer_receive_channel = peer_receive self.dead_peer_receive_channel = dead_peer_receive # Register a notifee self.host.get_network().register_notifee( PubsubNotifee(peer_send, dead_peer_send) ) # Register stream handlers for each pubsub router protocol to handle # the pubsub streams opened on those protocols for protocol in router.get_protocols(): self.host.set_stream_handler(protocol, self.stream_handler) # keeps track of seen messages as LRU cache if cache_size is None: self.cache_size = 128 else: self.cache_size = cache_size self.strict_signing = strict_signing if strict_signing: self.sign_key = self.host.get_private_key() else: self.sign_key = None self.seen_messages = LRU(self.cache_size) # Map of topics we are subscribed to blocking queues # for when the given topic receives a message self.subscribed_topics_send = {} self.subscribed_topics_receive = {} # Map of topic to peers to keep track of what peers are subscribed to self.peer_topics = {} # Create peers map, which maps peer_id (as string) to stream (to a given peer) self.peers = {} # Map of topic to topic validator self.topic_validators = {} self.counter = int(time.time()) self.event_handle_peer_queue_started = trio.Event() self.event_handle_dead_peer_queue_started = trio.Event() async def run(self) -> None: self.manager.run_daemon_task(self.handle_peer_queue) self.manager.run_daemon_task(self.handle_dead_peer_queue) await self.manager.wait_finished() @property def my_id(self) -> ID: return self.host.get_id() @property def protocols(self) -> Tuple[TProtocol, ...]: return tuple(self.router.get_protocols()) @property def topic_ids(self) -> KeysView[str]: return self.subscribed_topics_receive.keys() def get_hello_packet(self) -> rpc_pb2.RPC: """Generate subscription message with all topics we are subscribed to only send hello packet if we have subscribed topics.""" packet = rpc_pb2.RPC() for topic_id in self.topic_ids: packet.subscriptions.extend( [rpc_pb2.RPC.SubOpts(subscribe=True, topicid=topic_id)] ) return packet async def continuously_read_stream(self, stream: INetStream) -> None: """ Read from input stream in an infinite loop. Process messages from other nodes. :param stream: stream to continously read from """ peer_id = stream.muxed_conn.peer_id while self.manager.is_running: incoming: bytes = await read_varint_prefixed_bytes(stream) rpc_incoming: rpc_pb2.RPC = rpc_pb2.RPC() rpc_incoming.ParseFromString(incoming) if rpc_incoming.publish: # deal with RPC.publish for msg in rpc_incoming.publish: if not self._is_subscribed_to_msg(msg): continue logger.debug( "received `publish` message %s from peer %s", msg, peer_id ) self.manager.run_task(self.push_msg, peer_id, msg) if rpc_incoming.subscriptions: # deal with RPC.subscriptions # We don't need to relay the subscription to our # peers because a given node only needs its peers # to know that it is subscribed to the topic (doesn't # need everyone to know) for message in rpc_incoming.subscriptions: logger.debug( "received `subscriptions` message %s from peer %s", message, peer_id, ) self.handle_subscription(peer_id, message) # NOTE: Check if `rpc_incoming.control` is set through `HasField`. # This is necessary because `control` is an optional field in pb2. # Ref: https://developers.google.com/protocol-buffers/docs/reference/python-generated#singular-fields-proto2 # noqa: E501 if rpc_incoming.HasField("control"): # Pass rpc to router so router could perform custom logic logger.debug( "received `control` message %s from peer %s", rpc_incoming.control, peer_id, ) await self.router.handle_rpc(rpc_incoming, peer_id) def set_topic_validator( self, topic: str, validator: ValidatorFn, is_async_validator: bool ) -> None: """ Register a validator under the given topic. One topic can only have one validtor. :param topic: the topic to register validator under :param validator: the validator used to validate messages published to the topic :param is_async_validator: indicate if the validator is an asynchronous validator """ self.topic_validators[topic] = TopicValidator(validator, is_async_validator) def remove_topic_validator(self, topic: str) -> None: """ Remove the validator from the given topic. :param topic: the topic to remove validator from """ self.topic_validators.pop(topic, None) def get_msg_validators(self, msg: rpc_pb2.Message) -> Tuple[TopicValidator, ...]: """ Get all validators corresponding to the topics in the message. :param msg: the message published to the topic """ return tuple( self.topic_validators[topic] for topic in msg.topicIDs if topic in self.topic_validators ) async def stream_handler(self, stream: INetStream) -> None: """ Stream handler for pubsub. Gets invoked whenever a new stream is created on one of the supported pubsub protocols. :param stream: newly created stream """ peer_id = stream.muxed_conn.peer_id try: await self.continuously_read_stream(stream) except (StreamEOF, StreamReset, ParseError, IncompleteReadError) as error: logger.debug( "fail to read from peer %s, error=%s," "closing the stream and remove the peer from record", peer_id, error, ) await stream.reset() self._handle_dead_peer(peer_id) async def wait_until_ready(self) -> None: await self.event_handle_peer_queue_started.wait() await self.event_handle_dead_peer_queue_started.wait() async def _handle_new_peer(self, peer_id: ID) -> None: try: stream: INetStream = await self.host.new_stream(peer_id, self.protocols) except SwarmException as error: logger.debug("fail to add new peer %s, error %s", peer_id, error) return # Send hello packet hello = self.get_hello_packet() try: await stream.write(encode_varint_prefixed(hello.SerializeToString())) except StreamClosed: logger.debug("Fail to add new peer %s: stream closed", peer_id) return # TODO: Check if the peer in black list. try: self.router.add_peer(peer_id, stream.get_protocol()) except Exception as error: logger.debug("fail to add new peer %s, error %s", peer_id, error) return self.peers[peer_id] = stream logger.debug("added new peer %s", peer_id) def _handle_dead_peer(self, peer_id: ID) -> None: if peer_id not in self.peers: return del self.peers[peer_id] for topic in self.peer_topics: if peer_id in self.peer_topics[topic]: self.peer_topics[topic].discard(peer_id) self.router.remove_peer(peer_id) logger.debug("removed dead peer %s", peer_id) async def handle_peer_queue(self) -> None: """Continuously read from peer queue and each time a new peer is found, open a stream to the peer using a supported pubsub protocol pubsub protocols we support.""" async with self.peer_receive_channel: self.event_handle_peer_queue_started.set() async for peer_id in self.peer_receive_channel: # Add Peer self.manager.run_task(self._handle_new_peer, peer_id) async def handle_dead_peer_queue(self) -> None: """Continuously read from dead peer channel and close the stream between that peer and remove peer info from pubsub and pubsub router.""" async with self.dead_peer_receive_channel: self.event_handle_dead_peer_queue_started.set() async for peer_id in self.dead_peer_receive_channel: # Remove Peer self._handle_dead_peer(peer_id) def handle_subscription( self, origin_id: ID, sub_message: rpc_pb2.RPC.SubOpts ) -> None: """ Handle an incoming subscription message from a peer. Update internal mapping to mark the peer as subscribed or unsubscribed to topics as defined in the subscription message. :param origin_id: id of the peer who subscribe to the message :param sub_message: RPC.SubOpts """ if sub_message.subscribe: if sub_message.topicid not in self.peer_topics: self.peer_topics[sub_message.topicid] = set([origin_id]) elif origin_id not in self.peer_topics[sub_message.topicid]: # Add peer to topic self.peer_topics[sub_message.topicid].add(origin_id) else: if sub_message.topicid in self.peer_topics: if origin_id in self.peer_topics[sub_message.topicid]: self.peer_topics[sub_message.topicid].discard(origin_id) def notify_subscriptions(self, publish_message: rpc_pb2.Message) -> None: """ Put incoming message from a peer onto my blocking queue. :param publish_message: RPC.Message format """ # Check if this message has any topics that we are subscribed to for topic in publish_message.topicIDs: if topic in self.topic_ids: # we are subscribed to a topic this message was sent for, # so add message to the subscription output queue # for each topic try: self.subscribed_topics_send[topic].send_nowait(publish_message) except trio.WouldBlock: # Channel is full, ignore this message. logger.warning( "fail to deliver message to subscription for topic %s", topic ) async def subscribe(self, topic_id: str) -> ISubscriptionAPI: """ Subscribe ourself to a topic. :param topic_id: topic_id to subscribe to """ logger.debug("subscribing to topic %s", topic_id) # Already subscribed if topic_id in self.topic_ids: return self.subscribed_topics_receive[topic_id] send_channel, receive_channel = trio.open_memory_channel[rpc_pb2.Message]( SUBSCRIPTION_CHANNEL_SIZE ) subscription = TrioSubscriptionAPI( receive_channel, unsubscribe_fn=functools.partial(self.unsubscribe, topic_id), ) self.subscribed_topics_send[topic_id] = send_channel self.subscribed_topics_receive[topic_id] = subscription # Create subscribe message packet: rpc_pb2.RPC = rpc_pb2.RPC() packet.subscriptions.extend( [rpc_pb2.RPC.SubOpts(subscribe=True, topicid=topic_id)] ) # Send out subscribe message to all peers await self.message_all_peers(packet.SerializeToString()) # Tell router we are joining this topic await self.router.join(topic_id) # Return the subscription for messages on this topic return subscription async def unsubscribe(self, topic_id: str) -> None: """ Unsubscribe ourself from a topic. :param topic_id: topic_id to unsubscribe from """ logger.debug("unsubscribing from topic %s", topic_id) # Return if we already unsubscribed from the topic if topic_id not in self.topic_ids: return # Remove topic_id from the maps before yielding send_channel = self.subscribed_topics_send[topic_id] del self.subscribed_topics_send[topic_id] del self.subscribed_topics_receive[topic_id] # Only close the send side await send_channel.aclose() # Create unsubscribe message packet: rpc_pb2.RPC = rpc_pb2.RPC() packet.subscriptions.extend( [rpc_pb2.RPC.SubOpts(subscribe=False, topicid=topic_id)] ) # Send out unsubscribe message to all peers await self.message_all_peers(packet.SerializeToString()) # Tell router we are leaving this topic await self.router.leave(topic_id) async def message_all_peers(self, raw_msg: bytes) -> None: """ Broadcast a message to peers. :param raw_msg: raw contents of the message to broadcast """ # Broadcast message for stream in self.peers.values(): # Write message to stream try: await stream.write(encode_varint_prefixed(raw_msg)) except StreamClosed: peer_id = stream.muxed_conn.peer_id logger.debug("Fail to message peer %s: stream closed", peer_id) self._handle_dead_peer(peer_id) async def publish(self, topic_id: str, data: bytes) -> None: """ Publish data to a topic. :param topic_id: topic which we are going to publish the data to :param data: data which we are publishing """ msg = rpc_pb2.Message( data=data, topicIDs=[topic_id], # Origin is ourself. from_id=self.my_id.to_bytes(), seqno=self._next_seqno(), ) if self.strict_signing: priv_key = self.sign_key signature = priv_key.sign( PUBSUB_SIGNING_PREFIX.encode() + msg.SerializeToString() ) msg.key = self.host.get_public_key().serialize() msg.signature = signature await self.push_msg(self.my_id, msg) logger.debug("successfully published message %s", msg) async def validate_msg(self, msg_forwarder: ID, msg: rpc_pb2.Message) -> None: """ Validate the received message. :param msg_forwarder: the peer who forward us the message. :param msg: the message. """ sync_topic_validators: List[SyncValidatorFn] = [] async_topic_validators: List[AsyncValidatorFn] = [] for topic_validator in self.get_msg_validators(msg): if topic_validator.is_async: async_topic_validators.append( cast(AsyncValidatorFn, topic_validator.validator) ) else: sync_topic_validators.append( cast(SyncValidatorFn, topic_validator.validator) ) for validator in sync_topic_validators: if not validator(msg_forwarder, msg): raise ValidationError(f"Validation failed for msg={msg}") # TODO: Implement throttle on async validators if len(async_topic_validators) > 0: # TODO: Use a better pattern final_result: bool = True async def run_async_validator(func: AsyncValidatorFn) -> None: nonlocal final_result result = await func(msg_forwarder, msg) final_result = final_result and result async with trio.open_nursery() as nursery: for async_validator in async_topic_validators: nursery.start_soon(run_async_validator, async_validator) if not final_result: raise ValidationError(f"Validation failed for msg={msg}") async def push_msg(self, msg_forwarder: ID, msg: rpc_pb2.Message) -> None: """ Push a pubsub message to others. :param msg_forwarder: the peer who forward us the message. :param msg: the message we are going to push out. """ logger.debug("attempting to publish message %s", msg) # TODO: Check if the `source` is in the blacklist. If yes, reject. # TODO: Check if the `from` is in the blacklist. If yes, reject. # If the message is processed before, return(i.e., don't further process the message). if self._is_msg_seen(msg): return # Check if signing is required and if so validate the signature if self.strict_signing: # Validate the signature of the message if not signature_validator(msg): logger.debug("Signature validation failed for msg: %s", msg) return # Validate the message with registered topic validators. # If the validation failed, return(i.e., don't further process the message). try: await self.validate_msg(msg_forwarder, msg) except ValidationError: logger.debug( "Topic validation failed: sender %s sent data %s under topic IDs: %s %s:%s", msg_forwarder, msg.data.hex(), msg.topicIDs, base58.b58encode(msg.from_id).decode(), msg.seqno.hex(), ) return self._mark_msg_seen(msg) self.notify_subscriptions(msg) await self.router.publish(msg_forwarder, msg) def _next_seqno(self) -> bytes: """Make the next message sequence id.""" self.counter += 1 return self.counter.to_bytes(8, "big") def _is_msg_seen(self, msg: rpc_pb2.Message) -> bool: msg_id = self._msg_id_constructor(msg) return msg_id in self.seen_messages def _mark_msg_seen(self, msg: rpc_pb2.Message) -> None: msg_id = self._msg_id_constructor(msg) # FIXME: Mapping `msg_id` to `1` is quite awkward. Should investigate if there is a # more appropriate way. self.seen_messages[msg_id] = 1 def _is_subscribed_to_msg(self, msg: rpc_pb2.Message) -> bool: return any(topic in self.topic_ids for topic in msg.topicIDs)