Implemented links

.gitignore

@@ -1,4 +1,5 @@
 .DS_Store
 *.pyc
 t.py
+t2.py
 TODO

Notes/Header format

@@ -1,8 +1,8 @@
 header types
 -----------------
-type 1			00	One byte header, one 10 byte address field
-type 2			01	One byte header, two 10 byte address fields
-type 3			10	Reserved
+type 1			00	Two byte header, one 10 byte address field
+type 2			01	Two byte header, two 10 byte address fields
+type 3			10	Two byte header, one 10 byte address field, used for link request proofs
 type 4			11	Reserved for extended header format
 
 

RNS/Destination.py

@@ -9,6 +9,11 @@ from cryptography.hazmat.primitives import serialization
 from cryptography.hazmat.primitives.asymmetric import rsa
 from cryptography.hazmat.primitives.asymmetric import padding
 
+class Callbacks:
+	def __init__(self):
+		self.link_established = None
+		self.packet = None
+		self.proof = None
 
 class Destination:
 	KEYSIZE    = RNS.Identity.KEYSIZE;
@@ -59,11 +64,14 @@ class Destination:
 		if "." in app_name: raise ValueError("Dots can't be used in app names") 
 		if not type in Destination.types: raise ValueError("Unknown destination type")
 		if not direction in Destination.directions: raise ValueError("Unknown destination direction")
+		self.callbacks = Callbacks()
 		self.type = type
 		self.direction = direction
 		self.proof_strategy = Destination.PROVE_NONE
 		self.mtu = 0
 
+		self.links = []
+
 		if identity != None and type == Destination.SINGLE:
 			aspects = aspects+(identity.hexhash,)
 
@@ -87,11 +95,14 @@ class Destination:
 		return "<"+self.name+"/"+self.hexhash+">"
 
 
-	def setCallback(self, callback):
-		self.callback = callback
+	def link_established_callback(self, callback):
+		self.callbacks.link_established = callback
 
-	def setProofCallback(self, callback):
-		self.proofcallback = callback
+	def packet_callback(self, callback):
+		self.callbacks.packet = callback
+
+	def proof_callback(self, callback):
+		self.callbacks.proof = callback
 
 	def setProofStrategy(self, proof_strategy):
 		if not proof_strategy in Destination.proof_strategies:
@@ -101,9 +112,19 @@ class Destination:
 
 	def receive(self, packet):
 		plaintext = self.decrypt(packet.data)
-		if plaintext != None and self.callback != None:
-			self.callback(plaintext, packet)
+		if plaintext != None:
+			if packet.packet_type == RNS.Packet.LINKREQUEST:
+				self.incomingLinkRequest(plaintext, packet)
 
+			if packet.packet_type == RNS.Packet.RESOURCE:
+				if self.callbacks.packet != None:
+					self.callbacks.packet(plaintext, packet)
+
+	def incomingLinkRequest(self, data, packet):
+		link = RNS.Link.validateRequest(self, data, packet)
+		if link != None:
+			RNS.log(str(self)+" accepted link request", RNS.LOG_DEBUG)
+			self.links.append(link)
 
 	def createKeys(self):
 		if self.type == Destination.PLAIN:

RNS/Identity.py

@@ -14,9 +14,9 @@ from cryptography.hazmat.primitives.asymmetric import rsa
 from cryptography.hazmat.primitives.asymmetric import padding
 
 class Identity:
-	# Configure key size
-	KEYSIZE    = 1536
-	DERKEYSIZE = 1808
+	#KEYSIZE    = 1536
+	KEYSIZE    = 1024
+	DERKEYSIZE = KEYSIZE+272
 
 	# Padding size, not configurable
 	PADDINGSIZE= 336
@@ -223,7 +223,7 @@ class Identity:
 						)
 					)
 			except:
-				RNS.log("Decryption by "+RNS.prettyhexrep(self.hash)+" failed")
+				RNS.log("Decryption by "+RNS.prettyhexrep(self.hash)+" failed", RNS.LOG_VERBOSE)
 				
 			return plaintext;
 		else:

RNS/Link.py

@@ -0,0 +1,174 @@
+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
+		self.resource_completed = None
+
+class Link:
+	CURVE = ec.SECP256R1()
+	ECPUBSIZE = 91
+
+	PENDING = 0x00
+	ACTIVE = 0x01
+
+	@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)
+				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):
+		self.callbacks = LinkCallbacks()
+		self.status = Link.PENDING
+		self.type = RNS.Destination.LINK
+		self.owner = owner
+		self.destination = destination
+		self.attached_interface = None
+		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
+		proof = RNS.Packet(self, proof_data, packet_type=RNS.Packet.PROOF, header_type=RNS.Packet.HEADER_3)
+		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)
+			if self.callbacks.link_established != None:
+				self.callbacks.link_established(self)
+			RNS.log("Link "+str(self)+" established with "+str(self.destination), RNS.LOG_VERBOSE)
+		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:
+			plaintext = self.decrypt(packet.data)
+			if (self.callbacks.packet != None):
+				self.callbacks.packet(plaintext, packet)
+
+	def encrypt(self, plaintext):
+		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):
+		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
+
+	def resource_started_callback(self, callback):
+		self.callbacks.resource_started = callback
+
+	def resource_completed_callback(self, callback):
+		self.callbacks.resource_completed = callback
+
+	def __str__(self):
+		return RNS.prettyhexrep(self.link_id)

RNS/Packet.py

@@ -12,7 +12,7 @@ class Packet:
 
 	HEADER_1     = 0x00;	# Normal header format
 	HEADER_2     = 0x01;	# Header format used for link packets in transport
-	HEADER_3     = 0x02;	# Reserved
+	HEADER_3     = 0x02;	# Normal header format, but used to indicate a link request proof
 	HEADER_4     = 0x03;	# Reserved
 	header_types = [HEADER_1, HEADER_2, HEADER_3, HEADER_4]
 
@@ -30,7 +30,7 @@ class Packet:
 			self.transport_id   = transport_id
 			self.data 		    = data
 			self.flags	 	    = self.getPackedFlags()
-			self.MTU     		= self.destination.MTU
+			self.MTU     		= RNS.Reticulum.MTU
 
 			self.raw    		= None
 			self.packed 		= False
@@ -45,7 +45,10 @@ class Packet:
 		self.packet_hash = None
 
 	def getPackedFlags(self):
-		packed_flags = (self.header_type << 6) | (self.transport_type << 4) | (self.destination.type << 2) | self.packet_type
+		if self.header_type == Packet.HEADER_3:
+			packed_flags = (self.header_type << 6) | (self.transport_type << 4) | RNS.Destination.LINK | self.packet_type
+		else:
+			packed_flags = (self.header_type << 6) | (self.transport_type << 4) | (self.destination.type << 2) | self.packet_type
 		return packed_flags
 
 	def pack(self):
@@ -58,10 +61,14 @@ class Packet:
 			else:
 				raise IOError("Packet with header type 2 must have a transport ID")
 
-		self.header += self.destination.hash
-		if self.packet_type != Packet.ANNOUNCE:
-			self.ciphertext = self.destination.encrypt(self.data)
-		else:
+		if self.header_type == Packet.HEADER_1:
+			self.header += self.destination.hash
+			if self.packet_type != Packet.ANNOUNCE:
+				self.ciphertext = self.destination.encrypt(self.data)
+			else:
+				self.ciphertext = self.data
+		if self.header_type == Packet.HEADER_3:
+			self.header += self.destination.link_id
 			self.ciphertext = self.data
 
 		self.raw = self.header + self.ciphertext
@@ -93,9 +100,10 @@ class Packet:
 
 	def send(self):
 		if not self.sent:
-			self.pack()
-			#RNS.log("Size: "+str(len(self.raw))+" header is "+str(len(self.header))+" payload is "+str(len(self.ciphertext)), RNS.LOG_DEBUG)
-			RNS.Transport.outbound(self.raw)
+			if not self.packed:
+				self.pack()
+	
+			RNS.Transport.outbound(self)
 			self.packet_hash = RNS.Identity.fullHash(self.raw)
 			self.sent_at = time.time()
 			self.sent = True

RNS/Reticulum.py

@@ -8,7 +8,7 @@ import os.path
 import os
 import RNS
 
-import traceback
+#import traceback
 
 class Reticulum:
 	MTU          = 500

RNS/Transport.py

@@ -10,15 +10,23 @@ class Transport:
 
 	interfaces	 	= []
 	destinations    = []
+	pending_links   = []
+	active_links	= []
 	packet_hashlist = []
 
 	@staticmethod
-	def outbound(raw):
-		Transport.cacheRaw(raw)
+	def outbound(packet):
+		Transport.cacheRaw(packet.raw)
 		for interface in Transport.interfaces:
 			if interface.OUT:
-				RNS.log("Transmitting "+str(len(raw))+" bytes via: "+str(interface), RNS.LOG_DEBUG)
-				interface.processOutgoing(raw)
+				should_transmit = True
+				if packet.destination.type == RNS.Destination.LINK:
+					if interface != packet.destination.attached_interface:
+						should_transmit = False
+
+				if should_transmit:
+					RNS.log("Transmitting "+str(len(packet.raw))+" bytes via: "+str(interface), RNS.LOG_DEBUG)
+					interface.processOutgoing(packet.raw)
 
 	@staticmethod
 	def inbound(raw, interface=None):
@@ -30,24 +38,45 @@ class Transport:
 			packet = RNS.Packet(None, raw)
 			packet.unpack()
 			packet.packet_hash = packet_hash
+			packet.receiving_interface = interface
 
 			if packet.packet_type == RNS.Packet.ANNOUNCE:
 				if RNS.Identity.validateAnnounce(packet):
 					Transport.cache(packet)
-			
-			if packet.packet_type == RNS.Packet.RESOURCE:
+
+			if packet.packet_type == RNS.Packet.LINKREQUEST:
 				for destination in Transport.destinations:
 					if destination.hash == packet.destination_hash and destination.type == packet.destination_type:
 						packet.destination = destination
 						destination.receive(packet)
 						Transport.cache(packet)
+			
+			if packet.packet_type == RNS.Packet.RESOURCE:
+				if packet.destination_type == RNS.Destination.LINK:
+					for link in Transport.active_links:
+						if link.link_id == packet.destination_hash:
+							link.receive(packet)
+							Transport.cache(packet)
+				else:
+					for destination in Transport.destinations:
+						if destination.hash == packet.destination_hash and destination.type == packet.destination_type:
+							packet.destination = destination
+							destination.receive(packet)
+							Transport.cache(packet)
 
 			if packet.packet_type == RNS.Packet.PROOF:
-				for destination in Transport.destinations:
-					if destination.hash == packet.destination_hash:
-						if destination.proofcallback != None:
-							destination.proofcallback(packet)
-						# TODO: add universal proof handling
+				if packet.header_type == RNS.Packet.HEADER_3:
+					# This is a link request proof, forward
+					# to a waiting link request
+					for link in Transport.pending_links:
+						if link.link_id == packet.destination_hash:
+							link.validateProof(packet)
+				else:
+					for destination in Transport.destinations:
+						if destination.hash == packet.destination_hash:
+							if destination.proofcallback != None:
+								destination.proofcallback(packet)
+							# TODO: add universal proof handling
 
 	@staticmethod
 	def registerDestination(destination):
@@ -55,9 +84,35 @@ class Transport:
 		if destination.direction == RNS.Destination.IN:
 			Transport.destinations.append(destination)
 
+	@staticmethod
+	def registerLink(link):
+		RNS.log("Registering link "+str(link))
+		if link.initiator:
+			Transport.pending_links.append(link)
+		else:
+			Transport.active_links.append(link)
+
+	@staticmethod
+	def activateLink(link):
+		RNS.log("Activating link "+str(link))
+		if link in Transport.pending_links:
+			Transport.pending_links.remove(link)
+			Transport.active_links.append(link)
+			link.status = RNS.Link.ACTIVE
+		else:
+			RNS.log("Attempted to activate a link that was not in the pending table", RNS.LOG_ERROR)
+
+
+	@staticmethod
+	def shouldCache(packet):
+		# TODO: Implement sensible rules for which
+		# packets to cache
+		return False
+
 	@staticmethod
 	def cache(packet):
-		RNS.Transport.cacheRaw(packet.raw)
+		if RNS.Transport.shouldCache(packet):
+			RNS.Transport.cacheRaw(packet.raw)
 
 	@staticmethod
 	def cacheRaw(raw):

RNS/__init__.py

@@ -4,6 +4,7 @@ import time
 
 from .Reticulum import Reticulum
 from .Identity import Identity
+from .Link import Link
 from .Transport import Transport
 from .Destination import Destination
 from .Packet import Packet