Reticulum/RNS/Link.py

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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
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from .vendor import umsgpack as umsgpack
import threading
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import base64
import math
import time
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import RNS
import traceback
class LinkCallbacks:
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def __init__(self):
self.link_established = None
self.link_closed = None
self.packet = None
self.resource_started = None
self.resource_concluded = None
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class Link:
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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
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def validate_request(owner, data, packet):
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if len(data) == (Link.ECPUBSIZE):
try:
link = Link(owner = owner, peer_pub_bytes = data[:Link.ECPUBSIZE])
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link.set_link_id(packet)
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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:
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self.load_peer(peer_pub_bytes)
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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()
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self.set_link_id(self.packet)
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RNS.Transport.registerLink(self)
self.request_time = time.time()
self.start_watchdog()
self.packet.send()
self.had_outbound()
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RNS.log("Link request "+RNS.prettyhexrep(self.link_id)+" sent to "+str(self.destination), RNS.LOG_VERBOSE)
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def load_peer(self, peer_pub_bytes):
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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
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def set_link_id(self, packet):
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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,
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salt=self.get_salt(),
info=self.get_context(),
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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()
self.had_outbound()
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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()
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def validate_proof(self, packet):
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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):
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self.load_peer(peer_pub_bytes)
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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.had_outbound()
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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()
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def get_salt(self):
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return self.link_id
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def get_context(self):
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return None
def no_inbound_for(self):
return time.time() - self.last_inbound
def no_outbound_for(self):
return time.time() - self.last_outbound
def inactive_for(self):
return min(self.no_inbound_for(), self.no_outbound_for())
def had_outbound(self):
self.last_outbound = time.time()
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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.had_outbound()
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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
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sleep(sleep_time)
def send_keepalive(self):
keepalive_packet = RNS.Packet(self, bytes([0xFF]), context=RNS.Packet.KEEPALIVE)
keepalive_packet.send()
self.had_outbound()
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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()
self.had_outbound()
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# 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:
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resource.validate_proof(packet.data)
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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()
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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)