from cryptography.hazmat.backends import default_backend from cryptography.hazmat.primitives import hashes from cryptography.hazmat.primitives import serialization from cryptography.hazmat.primitives.asymmetric.ed25519 import Ed25519PrivateKey, Ed25519PublicKey from cryptography.hazmat.primitives.asymmetric.x25519 import X25519PrivateKey, X25519PublicKey from cryptography.hazmat.primitives.kdf.hkdf import HKDF from cryptography.fernet import Fernet from time import sleep from .vendor import umsgpack as umsgpack import threading import base64 import math import time import RNS import traceback class LinkCallbacks: def __init__(self): self.link_established = None self.link_closed = None self.packet = None self.resource = None self.resource_started = None self.resource_concluded = None class Link: """ This class. :param destination: A :ref:`RNS.Destination` instance which to establish a link to. :param owner: Internal use by :ref:`RNS.Transport`, ignore this argument. :param peer_pub_bytes: Internal use, ignore this argument. :param peer_sig_pub_bytes: Internal use, ignore this argument. """ CURVE = RNS.Identity.CURVE """ The curve used for Elliptic Curve DH key exchanges """ ECPUBSIZE = 32+32 KEYSIZE = 32 MDU = math.floor((RNS.Reticulum.MDU-RNS.Identity.AES_HMAC_OVERHEAD)/RNS.Identity.AES128_BLOCKSIZE)*RNS.Identity.AES128_BLOCKSIZE - 1 # TODO: This should not be hardcoded, # but calculated from something like # first-hop RTT latency and distance DEFAULT_TIMEOUT = 15.0 """ Default timeout for link establishment in seconds. """ TIMEOUT_FACTOR = 3 STALE_GRACE = 2 KEEPALIVE = 180 """ Interval for sending keep-alive packets on established links in seconds. """ PENDING = 0x00 HANDSHAKE = 0x01 ACTIVE = 0x02 STALE = 0x03 CLOSED = 0x04 TIMEOUT = 0x01 INITIATOR_CLOSED = 0x02 DESTINATION_CLOSED = 0x03 ACCEPT_NONE = 0x00 ACCEPT_APP = 0x01 ACCEPT_ALL = 0x02 resource_strategies = [ACCEPT_NONE, ACCEPT_APP, ACCEPT_ALL] @staticmethod def validate_request(owner, data, packet): if len(data) == (Link.ECPUBSIZE): try: link = Link(owner = owner, peer_pub_bytes=data[:Link.ECPUBSIZE//2], peer_sig_pub_bytes=data[Link.ECPUBSIZE//2:Link.ECPUBSIZE]) link.set_link_id(packet) link.destination = packet.destination RNS.log("Validating link request "+RNS.prettyhexrep(link.link_id), RNS.LOG_VERBOSE) link.handshake() link.attached_interface = packet.receiving_interface link.prove() link.request_time = time.time() RNS.Transport.register_link(link) link.last_inbound = time.time() link.start_watchdog() RNS.log("Incoming link request "+str(link)+" accepted", RNS.LOG_VERBOSE) return link except Exception as e: RNS.log("Validating link request failed", RNS.LOG_VERBOSE) traceback.print_exc() return None else: RNS.log("Invalid link request payload size, dropping request", RNS.LOG_VERBOSE) return None def __init__(self, destination=None, owner=None, peer_pub_bytes = None, peer_sig_pub_bytes = None): if destination != None and destination.type != RNS.Destination.SINGLE: raise TypeError("Links can only be established to the \"single\" destination type") self.rtt = None self.callbacks = LinkCallbacks() self.resource_strategy = Link.ACCEPT_NONE self.outgoing_resources = [] self.incoming_resources = [] self.last_inbound = 0 self.last_outbound = 0 self.tx = 0 self.rx = 0 self.txbytes = 0 self.rxbytes = 0 self.default_timeout = Link.DEFAULT_TIMEOUT self.proof_timeout = self.default_timeout self.timeout_factor = Link.TIMEOUT_FACTOR self.keepalive = Link.KEEPALIVE self.watchdog_lock = False self.status = Link.PENDING self.type = RNS.Destination.LINK self.owner = owner self.destination = destination self.attached_interface = None self.__encryption_disabled = False if self.destination == None: self.initiator = False else: self.initiator = True self.fernet = None self.prv = X25519PrivateKey.generate() self.sig_prv = Ed25519PrivateKey.generate() self.pub = self.prv.public_key() self.pub_bytes = self.pub.public_bytes( encoding=serialization.Encoding.Raw, format=serialization.PublicFormat.Raw ) self.sig_pub = self.sig_prv.public_key() self.sig_pub_bytes = self.sig_pub.public_bytes( encoding=serialization.Encoding.Raw, format=serialization.PublicFormat.Raw ) if peer_pub_bytes == None: self.peer_pub = None self.peer_pub_bytes = None else: self.load_peer(peer_pub_bytes, peer_sig_pub_bytes) if (self.initiator): self.request_data = self.pub_bytes+self.sig_pub_bytes self.packet = RNS.Packet(destination, self.request_data, packet_type=RNS.Packet.LINKREQUEST) self.packet.pack() self.set_link_id(self.packet) RNS.Transport.register_link(self) self.request_time = time.time() self.start_watchdog() self.packet.send() self.had_outbound() RNS.log("Link request "+RNS.prettyhexrep(self.link_id)+" sent to "+str(self.destination), RNS.LOG_VERBOSE) def load_peer(self, peer_pub_bytes, peer_sig_pub_bytes): self.peer_pub_bytes = peer_pub_bytes self.peer_pub = X25519PublicKey.from_public_bytes(self.peer_pub_bytes) self.peer_sig_pub_bytes = peer_sig_pub_bytes self.peer_sig_pub = Ed25519PublicKey.from_public_bytes(self.peer_sig_pub_bytes) if not hasattr(self.peer_pub, "curve"): self.peer_pub.curve = Link.CURVE def set_link_id(self, packet): self.link_id = packet.getTruncatedHash() self.hash = self.link_id def handshake(self): self.status = Link.HANDSHAKE self.shared_key = self.prv.exchange(self.peer_pub) self.derived_key = HKDF( algorithm=hashes.SHA256(), length=32, salt=self.get_salt(), info=self.get_context(), ).derive(self.shared_key) def prove(self): signed_data = self.link_id+self.pub_bytes+self.sig_pub_bytes signature = self.owner.identity.sign(signed_data) proof_data = self.pub_bytes+self.sig_pub_bytes+signature proof = RNS.Packet(self, proof_data, packet_type=RNS.Packet.PROOF, context=RNS.Packet.LRPROOF) proof.send() self.had_outbound() def prove_packet(self, packet): signature = self.sign(packet.packet_hash) # TODO: Hardcoded as explicit proof for now # if RNS.Reticulum.should_use_implicit_proof(): # proof_data = signature # else: # proof_data = packet.packet_hash + signature proof_data = packet.packet_hash + signature proof = RNS.Packet(self, proof_data, RNS.Packet.PROOF) proof.send() self.had_outbound() def validate_proof(self, packet): if self.initiator and len(packet.data) == Link.ECPUBSIZE+RNS.Identity.KEYSIZE//8: peer_pub_bytes = packet.data[:Link.ECPUBSIZE//2] peer_sig_pub_bytes = packet.data[Link.ECPUBSIZE//2:Link.ECPUBSIZE] signed_data = self.link_id+peer_pub_bytes+peer_sig_pub_bytes signature = packet.data[Link.ECPUBSIZE:RNS.Identity.KEYSIZE//8+Link.ECPUBSIZE] if self.destination.identity.validate(signature, signed_data): self.load_peer(peer_pub_bytes, peer_sig_pub_bytes) self.handshake() self.rtt = time.time() - self.request_time self.attached_interface = packet.receiving_interface RNS.Transport.activate_link(self) RNS.log("Link "+str(self)+" established with "+str(self.destination)+", RTT is "+str(self.rtt), RNS.LOG_VERBOSE) rtt_data = umsgpack.packb(self.rtt) rtt_packet = RNS.Packet(self, rtt_data, context=RNS.Packet.LRRTT) RNS.log("Sending RTT packet", RNS.LOG_EXTREME); rtt_packet.send() self.had_outbound() self.status = Link.ACTIVE if self.callbacks.link_established != None: thread = threading.Thread(target=self.callbacks.link_established, args=(self,)) thread.setDaemon(True) thread.start() else: RNS.log("Invalid link proof signature received by "+str(self)+". Ignoring.", RNS.LOG_DEBUG) def rtt_packet(self, packet): try: # TODO: This is crude, we should use the delta # to model a more representative per-bit round # trip time, and use that to set a sensible RTT # expectancy for the link. This will have to do # for now though. measured_rtt = time.time() - self.request_time plaintext = self.decrypt(packet.data) rtt = umsgpack.unpackb(plaintext) self.rtt = max(measured_rtt, rtt) self.status = Link.ACTIVE if self.owner.callbacks.link_established != None: self.owner.callbacks.link_established(self) except Exception as e: RNS.log("Error occurred while processing RTT packet, tearing down link", RNS.LOG_ERROR) traceback.print_exc() self.teardown() def get_salt(self): return self.link_id def get_context(self): return None def no_inbound_for(self): """ :returns: The time in seconds since last inbound packet on the link. """ return time.time() - self.last_inbound def no_outbound_for(self): """ :returns: The time in seconds since last outbound packet on the link. """ return time.time() - self.last_outbound def inactive_for(self): """ :returns: The time in seconds since activity on the link. """ return min(self.no_inbound_for(), self.no_outbound_for()) def had_outbound(self): self.last_outbound = time.time() def teardown(self): """ Closes the link and purges encryption keys. New keys will be used if a new link to the same destination is established. """ if self.status != Link.PENDING and self.status != Link.CLOSED: teardown_packet = RNS.Packet(self, self.link_id, context=RNS.Packet.LINKCLOSE) teardown_packet.send() self.had_outbound() self.status = Link.CLOSED if self.initiator: self.teardown_reason = Link.INITIATOR_CLOSED else: self.teardown_reason = Link.DESTINATION_CLOSED self.link_closed() def teardown_packet(self, packet): try: plaintext = self.decrypt(packet.data) if plaintext == self.link_id: self.status = Link.CLOSED if self.initiator: self.teardown_reason = Link.DESTINATION_CLOSED else: self.teardown_reason = Link.INITIATOR_CLOSED self.link_closed() except Exception as e: pass def link_closed(self): for resource in self.incoming_resources: resource.cancel() for resource in self.outgoing_resources: resource.cancel() self.prv = None self.pub = None self.pub_bytes = None self.shared_key = None self.derived_key = None if self.callbacks.link_closed != None: self.callbacks.link_closed(self) def start_watchdog(self): thread = threading.Thread(target=self.__watchdog_job) thread.setDaemon(True) thread.start() def __watchdog_job(self): while not self.status == Link.CLOSED: while (self.watchdog_lock): sleep(max(self.rtt, 0.025)) if not self.status == Link.CLOSED: # Link was initiated, but no response # from destination yet if self.status == Link.PENDING: next_check = self.request_time + self.proof_timeout sleep_time = next_check - time.time() if time.time() >= self.request_time + self.proof_timeout: RNS.log("Link establishment timed out", RNS.LOG_VERBOSE) self.status = Link.CLOSED self.teardown_reason = Link.TIMEOUT self.link_closed() sleep_time = 0.001 elif self.status == Link.HANDSHAKE: next_check = self.request_time + self.proof_timeout sleep_time = next_check - time.time() if time.time() >= self.request_time + self.proof_timeout: RNS.log("Timeout waiting for RTT packet from link initiator", RNS.LOG_DEBUG) self.status = Link.CLOSED self.teardown_reason = Link.TIMEOUT self.link_closed() sleep_time = 0.001 elif self.status == Link.ACTIVE: if time.time() >= self.last_inbound + self.keepalive: sleep_time = self.rtt * self.timeout_factor + Link.STALE_GRACE self.status = Link.STALE if self.initiator: self.send_keepalive() else: sleep_time = (self.last_inbound + self.keepalive) - time.time() elif self.status == Link.STALE: sleep_time = 0.001 self.status = Link.CLOSED self.teardown_reason = Link.TIMEOUT self.link_closed() if sleep_time == 0: RNS.log("Warning! Link watchdog sleep time of 0!", RNS.LOG_ERROR) if sleep_time == None or sleep_time < 0: RNS.log("Timing error! Tearing down link "+str(self)+" now.", RNS.LOG_ERROR) self.teardown() sleep_time = 0.1 sleep(sleep_time) def send_keepalive(self): keepalive_packet = RNS.Packet(self, bytes([0xFF]), context=RNS.Packet.KEEPALIVE) keepalive_packet.send() self.had_outbound() def receive(self, packet): self.watchdog_lock = True if not self.status == Link.CLOSED and not (self.initiator and packet.context == RNS.Packet.KEEPALIVE and packet.data == bytes([0xFF])): if packet.receiving_interface != self.attached_interface: RNS.log("Link-associated packet received on unexpected interface! Someone might be trying to manipulate your communication!", RNS.LOG_ERROR) else: self.last_inbound = time.time() self.rx += 1 self.rxbytes += len(packet.data) if self.status == Link.STALE: self.status = Link.ACTIVE if packet.packet_type == RNS.Packet.DATA: if packet.context == RNS.Packet.NONE: plaintext = self.decrypt(packet.data) if self.callbacks.packet != None: thread = threading.Thread(target=self.callbacks.packet, args=(plaintext, packet)) thread.setDaemon(True) thread.start() if self.destination.proof_strategy == RNS.Destination.PROVE_ALL: packet.prove() elif self.destination.proof_strategy == RNS.Destination.PROVE_APP: if self.destination.callbacks.proof_requested: self.destination.callbacks.proof_requested(packet) elif packet.context == RNS.Packet.LRRTT: if not self.initiator: self.rtt_packet(packet) elif packet.context == RNS.Packet.LINKCLOSE: self.teardown_packet(packet) elif packet.context == RNS.Packet.RESOURCE_ADV: packet.plaintext = self.decrypt(packet.data) if self.resource_strategy == Link.ACCEPT_NONE: pass elif self.resource_strategy == Link.ACCEPT_APP: if self.callbacks.resource != None: if self.callbacks.resource(resource): RNS.Resource.accept(packet, self.callbacks.resource_concluded) elif self.resource_strategy == Link.ACCEPT_ALL: RNS.Resource.accept(packet, self.callbacks.resource_concluded) elif packet.context == RNS.Packet.RESOURCE_REQ: plaintext = self.decrypt(packet.data) if ord(plaintext[:1]) == RNS.Resource.HASHMAP_IS_EXHAUSTED: resource_hash = plaintext[1+RNS.Resource.MAPHASH_LEN:RNS.Identity.HASHLENGTH//8+1+RNS.Resource.MAPHASH_LEN] else: resource_hash = plaintext[1:RNS.Identity.HASHLENGTH//8+1] for resource in self.outgoing_resources: if resource.hash == resource_hash: resource.request(plaintext) elif packet.context == RNS.Packet.RESOURCE_HMU: plaintext = self.decrypt(packet.data) resource_hash = plaintext[:RNS.Identity.HASHLENGTH//8] for resource in self.incoming_resources: if resource_hash == resource.hash: resource.hashmap_update_packet(plaintext) elif packet.context == RNS.Packet.RESOURCE_ICL: plaintext = self.decrypt(packet.data) resource_hash = plaintext[:RNS.Identity.HASHLENGTH//8] for resource in self.incoming_resources: if resource_hash == resource.hash: resource.cancel() elif packet.context == RNS.Packet.KEEPALIVE: if not self.initiator and packet.data == bytes([0xFF]): keepalive_packet = RNS.Packet(self, bytes([0xFE]), context=RNS.Packet.KEEPALIVE) keepalive_packet.send() self.had_outbound() # TODO: find the most efficient way to allow multiple # transfers at the same time, sending resource hash on # each packet is a huge overhead. Probably some kind # of hash -> sequence map elif packet.context == RNS.Packet.RESOURCE: for resource in self.incoming_resources: resource.receive_part(packet) elif packet.packet_type == RNS.Packet.PROOF: if packet.context == RNS.Packet.RESOURCE_PRF: resource_hash = packet.data[0:RNS.Identity.HASHLENGTH//8] for resource in self.outgoing_resources: if resource_hash == resource.hash: resource.validate_proof(packet.data) self.watchdog_lock = False def encrypt(self, plaintext): if self.__encryption_disabled: return plaintext try: if not self.fernet: self.fernet = Fernet(base64.urlsafe_b64encode(self.derived_key)) ciphertext = base64.urlsafe_b64decode(self.fernet.encrypt(plaintext)) return ciphertext except Exception as e: RNS.log("Encryption on link "+str(self)+" failed. The contained exception was: "+str(e), RNS.LOG_ERROR) def decrypt(self, ciphertext): if self.__encryption_disabled: return ciphertext try: if not self.fernet: self.fernet = Fernet(base64.urlsafe_b64encode(self.derived_key)) plaintext = self.fernet.decrypt(base64.urlsafe_b64encode(ciphertext)) return plaintext except Exception as e: RNS.log("Decryption failed on link "+str(self)+". The contained exception was: "+str(e), RNS.LOG_ERROR) RNS.log(traceback.format_exc(), RNS.LOG_ERROR) # TODO: Do we really need to do this? Or can we recover somehow? self.teardown() def sign(self, message): return self.sig_prv.sign(message) def validate(self, signature, message): try: self.peer_sig_pub.verify(signature, message) return True except Exception as e: return False def set_link_established_callback(self, callback): self.callbacks.link_established = callback def set_link_closed_callback(self, callback): self.callbacks.link_closed = callback def set_packet_callback(self, callback): """ Registers a function to be called when a packet has been received over this link. :param callback: A function or method with the signature *callback(message, packet)* to be called. """ self.callbacks.packet = callback def set_resource_callback(self, callback): """ Registers a function to be called when a resource has been advertised over this link. If the function returns *True* the resource will be accepted. If it returns *False* it will be ignored. :param callback: A function or method with the signature *callback(resource)* to be called. """ self.callbacks.resource = callback def set_resource_started_callback(self, callback): """ Registers a function to be called when a resource has begun transferring over this link. :param callback: A function or method with the signature *callback(resource)* to be called. """ self.callbacks.resource_started = callback def set_resource_concluded_callback(self, callback): """ Registers a function to be called when a resource has concluded transferring over this link. :param callback: A function or method with the signature *callback(resource)* to be called. """ self.callbacks.resource_concluded = callback def resource_concluded(self, resource): if resource in self.incoming_resources: self.incoming_resources.remove(resource) if resource in self.outgoing_resources: self.outgoing_resources.remove(resource) def set_resource_strategy(self, resource_strategy): """ Sets the resource strategy for the link. :param resource_strategy: One of ``RNS.Link.ACCEPT_NONE``, ``RNS.Link.ACCEPT_ALL`` or ``RNS.Link.ACCEPT_APP``. If ``RNS.Link.ACCEPT_APP`` is set, the `resource_callback` will be called to determine whether the resource should be accepted or not. :raises: *TypeError* if the resource strategy is unsupported. """ if not resource_strategy in Link.resource_strategies: raise TypeError("Unsupported resource strategy") else: self.resource_strategy = resource_strategy def register_outgoing_resource(self, resource): self.outgoing_resources.append(resource) def register_incoming_resource(self, resource): self.incoming_resources.append(resource) def cancel_outgoing_resource(self, resource): if resource in self.outgoing_resources: self.outgoing_resources.remove(resource) else: RNS.log("Attempt to cancel a non-existing outgoing resource", RNS.LOG_ERROR) def cancel_incoming_resource(self, resource): if resource in self.incoming_resources: self.incoming_resources.remove(resource) else: RNS.log("Attempt to cancel a non-existing incoming resource", RNS.LOG_ERROR) def ready_for_new_resource(self): if len(self.outgoing_resources) > 0: return False else: return True def disable_encryption(self): """ HAZARDOUS. This will downgrade the link to encryptionless. All information over the link will be sent in plaintext. Never use this in production applications. Should only be used for debugging purposes, and will disappear in a future version. If encryptionless links are not explicitly allowed in the users configuration file, Reticulum will terminate itself along with the client application and throw an error message to the user. """ if (RNS.Reticulum.should_allow_unencrypted()): RNS.log("The link "+str(self)+" was downgraded to an encryptionless link", RNS.LOG_NOTICE) self.__encryption_disabled = True else: RNS.log("Attempt to disable encryption on link, but encryptionless links are not allowed by config.", RNS.LOG_CRITICAL) RNS.log("Shutting down Reticulum now!", RNS.LOG_CRITICAL) RNS.panic() def encryption_disabled(self): return self.__encryption_disabled def __str__(self): return RNS.prettyhexrep(self.link_id)