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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.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<api-destination>` instance which to establish a link to.
:param owner: Internal use by :ref:`RNS.Transport<api-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)
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