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
import base64
import RNS
import traceback
class LinkCallbacks:
def __init__(self):
self.link_established = None
self.packet = None
self.resource_started = None
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self.resource_concluded = None
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class Link:
CURVE = ec.SECP256R1()
ECPUBSIZE = 91
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BLOCKSIZE = 16
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PENDING = 0x00
ACTIVE = 0x01
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ACCEPT_NONE = 0x00
ACCEPT_APP = 0x01
ACCEPT_ALL = 0x02
resource_strategies = [ACCEPT_NONE, ACCEPT_APP, ACCEPT_ALL]
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@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)
RNS.log("Validating link request "+RNS.prettyhexrep(link.link_id), RNS.LOG_VERBOSE)
link.handshake()
link.attached_interface = packet.receiving_interface
link.prove()
RNS.Transport.registerLink(link)
if link.owner.callbacks.link_established != None:
link.owner.callbacks.link_established(link)
RNS.log("Incoming link request "+str(link)+" accepted", RNS.LOG_VERBOSE)
except Exception as e:
RNS.log("Validating link request failed", RNS.LOG_VERBOSE)
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traceback.print_exc()
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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):
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if destination != None and destination.type != RNS.Destination.SINGLE:
raise TypeError("Links can only be established to the \"single\" destination type")
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self.rtt = None
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self.callbacks = LinkCallbacks()
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self.resource_strategy = Link.ACCEPT_NONE
self.outgoing_resources = []
self.incoming_resources = []
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self.status = Link.PENDING
self.type = RNS.Destination.LINK
self.owner = owner
self.destination = destination
self.attached_interface = None
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self.__encryption_disabled = False
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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.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())
self.peer_pub.curce = Link.CURVE
def setLinkID(self, packet):
self.link_id = RNS.Identity.truncatedHash(packet.raw)
self.hash = self.link_id
def handshake(self):
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
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proof = RNS.Packet(self, proof_data, packet_type=RNS.Packet.PROOF, context=RNS.Packet.LRPROOF)
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proof.send()
def validateProof(self, packet):
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.attached_interface = packet.receiving_interface
RNS.Transport.activateLink(self)
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RNS.log("Link "+str(self)+" established with "+str(self.destination), RNS.LOG_VERBOSE)
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if self.callbacks.link_established != None:
self.callbacks.link_established(self)
else:
RNS.log("Invalid link proof signature received by "+str(self), RNS.LOG_VERBOSE)
def getSalt(self):
return self.link_id
def getContext(self):
return None
def receive(self, packet):
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:
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if packet.packet_type == RNS.Packet.DATA:
if packet.context == RNS.Packet.NONE:
plaintext = self.decrypt(packet.data)
if (self.callbacks.packet != None):
self.callbacks.packet(plaintext, 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:
self.callbacks.resource(packet)
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()
# TODO: find the most efficient way to allow multiple
# transfers at the same time, sending resource hash on
# each packet is a huge overhead
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)
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def encrypt(self, plaintext):
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if self.__encryption_disabled:
return plaintext
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try:
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):
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if self.__encryption_disabled:
return ciphertext
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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)
def link_established_callback(self, callback):
self.callbacks.link_established = callback
def packet_callback(self, callback):
self.callbacks.packet = callback
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# Called when an incoming resource transfer is started
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def resource_started_callback(self, callback):
self.callbacks.resource_started = callback
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# Called when a resource transfer is concluded
def resource_concluded_callback(self, callback):
self.callbacks.resource_concluded = callback
def setResourceStrategy(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 incoming 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
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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()
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def encryption_disabled(self):
return self.__encryption_disabled
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def __str__(self):
return RNS.prettyhexrep(self.link_id)