from cryptography.hazmat.backends import default_backend from cryptography.hazmat.primitives import hashes from cryptography.hazmat.primitives import serialization from cryptography.hazmat.primitives.asymmetric import ec 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_started = None self.resource_concluded = None class Link: CURVE = ec.SECP256R1() ECPUBSIZE = 91 BLOCKSIZE = 16 AES_HMAC_OVERHEAD = 58 MDU = math.floor((RNS.Reticulum.MDU-AES_HMAC_OVERHEAD)/BLOCKSIZE)*BLOCKSIZE - 1 # TODO: This should not be hardcoded, # but calculated from something like # first-hop RTT latency and distance DEFAULT_TIMEOUT = 15.0 TIMEOUT_FACTOR = 3 STALE_GRACE = 2 KEEPALIVE = 180 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 validateRequest(owner, data, packet): if len(data) == (Link.ECPUBSIZE): try: link = Link(owner = owner, peer_pub_bytes = data[:Link.ECPUBSIZE]) link.setLinkID(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.registerLink(link) link.last_inbound = time.time() link.start_watchdog() # TODO: Why was link_established callback here? Seems weird # to call this before RTT packet has been received #if self.owner.callbacks.link_established != None: # self.owner.callbacks.link_established(link) 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): 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.prv = ec.generate_private_key(Link.CURVE, default_backend()) self.pub = self.prv.public_key() self.pub_bytes = self.pub.public_bytes( encoding=serialization.Encoding.DER, format=serialization.PublicFormat.SubjectPublicKeyInfo ) if peer_pub_bytes == None: self.peer_pub = None self.peer_pub_bytes = None else: self.loadPeer(peer_pub_bytes) if (self.initiator): self.request_data = self.pub_bytes self.packet = RNS.Packet(destination, self.request_data, packet_type=RNS.Packet.LINKREQUEST) self.packet.pack() self.setLinkID(self.packet) RNS.Transport.registerLink(self) self.request_time = time.time() self.start_watchdog() self.packet.send() RNS.log("Link request "+RNS.prettyhexrep(self.link_id)+" sent to "+str(self.destination), RNS.LOG_VERBOSE) def loadPeer(self, peer_pub_bytes): self.peer_pub_bytes = peer_pub_bytes self.peer_pub = serialization.load_der_public_key(peer_pub_bytes, backend=default_backend()) if not hasattr(self.peer_pub, "curve"): self.peer_pub.curve = Link.CURVE def setLinkID(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(ec.ECDH(), self.peer_pub) self.derived_key = HKDF( algorithm=hashes.SHA256(), length=32, salt=self.getSalt(), info=self.getContext(), backend=default_backend() ).derive(self.shared_key) def prove(self): signed_data = self.link_id+self.pub_bytes signature = self.owner.identity.sign(signed_data) proof_data = self.pub_bytes+signature proof = RNS.Packet(self, proof_data, packet_type=RNS.Packet.PROOF, context=RNS.Packet.LRPROOF) proof.send() 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() def validateProof(self, packet): if self.initiator: peer_pub_bytes = packet.data[:Link.ECPUBSIZE] signed_data = self.link_id+peer_pub_bytes signature = packet.data[Link.ECPUBSIZE:RNS.Identity.KEYSIZE//8+Link.ECPUBSIZE] if self.destination.identity.validate(signature, signed_data): self.loadPeer(peer_pub_bytes) self.handshake() self.rtt = time.time() - self.request_time self.attached_interface = packet.receiving_interface RNS.Transport.activateLink(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.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), RNS.LOG_VERBOSE) # TODO: should we really do this, or just wait # for a valid one? Needs analysis. self.teardown() 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 getSalt(self): return self.link_id def getContext(self): return None def inactive_for(self): return min(time.time() - self.last_inbound, time.time() - self.last_outbound) def teardown(self): 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.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() 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: thread = threading.Thread(target=self.callbacks.resource, args=(packet)) thread.setDaemon(True) thread.start() 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() # 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.validateProof(packet.data) self.watchdog_lock = False def encrypt(self, plaintext): if self.__encryption_disabled: return plaintext try: # TODO: Optimise this re-allocation fernet = Fernet(base64.urlsafe_b64encode(self.derived_key)) ciphertext = base64.urlsafe_b64decode(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: fernet = Fernet(base64.urlsafe_b64encode(self.derived_key)) plaintext = 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.prv.sign(message, ec.ECDSA(hashes.SHA256())) def validate(self, signature, message): try: self.peer_pub.verify(signature, message, ec.ECDSA(hashes.SHA256())) return True except Exception as e: return False def link_established_callback(self, callback): self.callbacks.link_established = callback def link_closed_callback(self, callback): self.callbacks.link_closed = callback def packet_callback(self, callback): self.callbacks.packet = callback # Called when an incoming resource transfer is started def resource_started_callback(self, callback): self.callbacks.resource_started = callback # Called when a resource transfer is concluded def resource_concluded_callback(self, callback): 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): 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 disableEncryption(self): 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)