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Commit a11f14e75fee0141fca2c4e4da9962a5cb046003

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Parents : c32086c

Author : Mark Qvist <mark@unsigned.io>

Date : 2024-09-04T17:37:18+02:00

Implemented ratchets

Changes

6 files changed, 170 insertions(+), 48 deletions(-)

M RNS/Destination.py +16 -11

M RNS/Identity.py +135 -28

M RNS/Link.py +1 -1

M RNS/Packet.py +14 -5

M RNS/Reticulum.py +1 -1

M RNS/Transport.py +3 -2

Diff

diff --git a/RNS/Destination.py b/RNS/Destination.py

index 736dcba3..92e47359 100755

--- a/RNS/Destination.py

+++ b/RNS/Destination.py

@@ -1,6 +1,6 @@

# MIT License

# Permission is hereby granted, free of charge, to any person obtaining a copy

# of this software and associated documentation files (the "Software"), to deal

@@ -72,7 +72,7 @@ class Destination:

directions = [IN, OUT]

PR_TAG_WINDOW = 30

- RATCHET_COUNT = 128

+ RATCHET_COUNT = 256

@staticmethod

def expand_name(identity, app_name, *aspects):

@@ -219,7 +219,7 @@ class Destination:

def rotate_ratchets(self):

if self.ratchets != None:

RNS.log("Rotating ratchets for "+str(self), RNS.LOG_DEBUG) # TODO: Remove

- new_ratchet = RNS.Identity.generate_ratchet()

+ new_ratchet = RNS.Identity._generate_ratchet()

self.ratchets.insert(0, new_ratchet)

if len (self.ratchets) > Destination.RATCHET_COUNT:

self.ratchets = self.ratchets[:Destination.RATCHET_COUNT]

@@ -241,6 +241,7 @@ class Destination:

if self.direction != Destination.IN:

raise TypeError("Only IN destination types can be announced")

+ ratchet = b""

now = time.time()

stale_responses = []

for entry_tag in self.path_responses:

@@ -269,8 +270,8 @@ class Destination:

if self.ratchets != None:

self.rotate_ratchets()

- ratchet_pub = RNS.Identity.ratchet_public_bytes(self.ratchets[0])

- RNS.log(f"Including {len(ratchet_pub)*8}-bit ratchet {RNS.hexrep(ratchet_pub)} in announce", RNS.LOG_DEBUG) # TODO: Remove

+ ratchet = RNS.Identity._ratchet_public_bytes(self.ratchets[0])

+ RNS.log(f"Including {len(ratchet)*8}-bit ratchet {RNS.hexrep(ratchet)} in announce", RNS.LOG_DEBUG) # TODO: Remove

if app_data == None and self.default_app_data != None:

if isinstance(self.default_app_data, bytes):

@@ -280,13 +281,12 @@ class Destination:

if isinstance(returned_app_data, bytes):

app_data = returned_app_data

- signed_data = self.hash+self.identity.get_public_key()+self.name_hash+random_hash

+ signed_data = self.hash+self.identity.get_public_key()+self.name_hash+random_hash+ratchet

if app_data != None:

signed_data += app_data

signature = self.identity.sign(signed_data)

- announce_data = self.identity.get_public_key()+self.name_hash+random_hash+signature

+ announce_data = self.identity.get_public_key()+self.name_hash+random_hash+ratchet+signature

if app_data != None:

announce_data += app_data

@@ -298,8 +298,13 @@ class Destination:

else:

announce_context = RNS.Packet.NONE

- announce_packet = RNS.Packet(self, announce_data, RNS.Packet.ANNOUNCE, context = announce_context, attached_interface = attached_interface)

+ if ratchet:

+ context_flag = RNS.Packet.FLAG_SET

+ else:

+ context_flag = RNS.Packet.FLAG_UNSET

+ announce_packet = RNS.Packet(self, announce_data, RNS.Packet.ANNOUNCE, context = announce_context,

+ attached_interface = attached_interface, context_flag=context_flag)

if send:

announce_packet.send()

else:

@@ -485,7 +490,7 @@ class Destination:

return plaintext

if self.type == Destination.SINGLE and self.identity != None:

- return self.identity.encrypt(plaintext)

+ return self.identity.encrypt(plaintext, ratchet=RNS.Identity.get_ratchet(self.hash))

if self.type == Destination.GROUP:

if hasattr(self, "prv") and self.prv != None:

@@ -510,7 +515,7 @@ class Destination:

return ciphertext

if self.type == Destination.SINGLE and self.identity != None:

- return self.identity.decrypt(ciphertext)

+ return self.identity.decrypt(ciphertext, ratchets=self.ratchets)

if self.type == Destination.GROUP:

if hasattr(self, "prv") and self.prv != None:

diff --git a/RNS/Identity.py b/RNS/Identity.py

index 010c1fd2..c7786634 100644

--- a/RNS/Identity.py

+++ b/RNS/Identity.py

@@ -1,6 +1,6 @@

# MIT License

# Permission is hereby granted, free of charge, to any person obtaining a copy

# of this software and associated documentation files (the "Software"), to deal

@@ -50,7 +50,10 @@ class Identity:

KEYSIZE = 256*2

"""

X25519 key size in bits. A complete key is the concatenation of a 256 bit encryption key, and a 256 bit signing key.

- """

+ """

+ RATCHETSIZE = 256

+ RATCHET_EXPIRY = 60*60*24*30

# Non-configurable constants

FERNET_OVERHEAD = RNS.Cryptography.Fernet.FERNET_OVERHEAD

@@ -67,6 +70,7 @@ class Identity:

# Storage

known_destinations = {}

+ known_ratchets = {}

@staticmethod

def remember(packet_hash, destination_hash, public_key, app_data = None):

@@ -222,29 +226,102 @@ class Identity:

return Identity.truncated_hash(os.urandom(Identity.TRUNCATED_HASHLENGTH//8))

@staticmethod

- def generate_ratchet():

+ def _ratchet_public_bytes(ratchet):

+ return X25519PrivateKey.from_private_bytes(ratchet).public_key().public_bytes()

+ @staticmethod

+ def _generate_ratchet():

ratchet_prv = X25519PrivateKey.generate()

ratchet_pub = ratchet_prv.public_key()

return ratchet_prv.private_bytes()

@staticmethod

- def ratchet_public_bytes(ratchet):

- return X25519PrivateKey.from_private_bytes(ratchet).public_key().public_bytes()

+ def _remember_ratchet(destination_hash, ratchet):

+ RNS.log(f"Remembering ratchet {RNS.hexrep(ratchet)} for {RNS.prettyhexrep(destination_hash)}", RNS.LOG_DEBUG) # TODO: Remove

+ try:

+ Identity.known_ratchets[destination_hash] = ratchet

+ hexhash = RNS.hexrep(destination_hash, delimit=False)

+ ratchet_data = {"ratchet": ratchet, "received": time.time()}

+ ratchetdir = RNS.Reticulum.storagepath+"/ratchets"

+ if not os.path.isdir(ratchetdir):

+ os.makedirs(ratchetdir)

+ outpath = f"{ratchetdir}/{hexhash}.out"

+ finalpath = f"{ratchetdir}/{hexhash}"

+ ratchet_file = open(outpath, "wb")

+ ratchet_file.write(umsgpack.packb(ratchet_data))

+ ratchet_file.close()

+ os.rename(outpath, finalpath)

+ except Exception as e:

+ RNS.log(f"Could not persist ratchet for {RNS.prettyhexrep(destination_hash)} to storage.", RNS.LOG_ERROR)

+ RNS.log(f"The contained exception was: {e}")

+ RNS.trace_exception(e)

+ @staticmethod

+ def get_ratchet(destination_hash):

+ if not destination_hash in Identity.known_ratchets:

+ RNS.log(f"Trying to load ratchet for {RNS.prettyhexrep(destination_hash)} from storage") # TODO: Remove

+ ratchetdir = RNS.Reticulum.storagepath+"/ratchets"

+ hexhash = RNS.hexrep(destination_hash, delimit=False)

+ ratchet_path = f"{ratchetdir}/hexhash"

+ if os.path.isfile(ratchet_path):

+ try:

+ ratchet_file = open(ratchet_path, "rb")

+ ratchet_data = umsgpack.unpackb(ratchets_file.read())

+ if time.time() < ratchet_data["received"]+Identity.RATCHET_EXPIRY and len(ratchet_data["ratchet"]) == Identity.RATCHETSIZE//8:

+ Identity.known_ratchets[destination_hash] = ratchet_data["ratchet"]

+ else:

+ return None

+ except Exception as e:

+ RNS.log(f"An error occurred while loading ratchet data for {RNS.prettyhexrep(destination_hash)} from storage.", RNS.LOG_ERROR)

+ RNS.log(f"The contained exception was: {e}", RNS.LOG_ERROR)

+ return None

+ if destination_hash in Identity.known_ratchets:

+ return Identity.known_ratchets[destination_hash]

+ else:

+ return None

@staticmethod

def validate_announce(packet, only_validate_signature=False):

try:

if packet.packet_type == RNS.Packet.ANNOUNCE:

+ keysize = Identity.KEYSIZE//8

+ ratchetsize = Identity.RATCHETSIZE//8

+ name_hash_len = Identity.NAME_HASH_LENGTH//8

+ sig_len = Identity.SIGLENGTH//8

destination_hash = packet.destination_hash

- public_key = packet.data[:Identity.KEYSIZE//8]

- name_hash = packet.data[Identity.KEYSIZE//8:Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8]

- random_hash = packet.data[Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8:Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8+10]

- signature = packet.data[Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8+10:Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8+10+Identity.SIGLENGTH//8]

- app_data = b""

- if len(packet.data) > Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8+10+Identity.SIGLENGTH//8:

- app_data = packet.data[Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8+10+Identity.SIGLENGTH//8:]

- signed_data = destination_hash+public_key+name_hash+random_hash+app_data

+ # Get public key bytes from announce

+ public_key = packet.data[:keysize]

+ # If the packet context flag is set,

+ # this announce contains a new ratchet

+ if packet.context_flag == RNS.Packet.FLAG_SET:

+ name_hash = packet.data[keysize:keysize+name_hash_len ]

+ random_hash = packet.data[keysize+name_hash_len:keysize+name_hash_len+10]

+ ratchet = packet.data[keysize+name_hash_len+10:keysize+name_hash_len+10+ratchetsize]

+ signature = packet.data[keysize+name_hash_len+10+ratchetsize:keysize+name_hash_len+10+ratchetsize+sig_len]

+ app_data = b""

+ if len(packet.data) > keysize+name_hash_len+10+sig_len+ratchetsize:

+ app_data = packet.data[keysize+name_hash_len+10+sig_len+ratchetsize:]

+ # If the packet context flag is not set,

+ # this announce does not contain a ratchet

+ else:

+ ratchet = b""

+ name_hash = packet.data[keysize:keysize+name_hash_len]

+ random_hash = packet.data[keysize+name_hash_len:keysize+name_hash_len+10]

+ signature = packet.data[keysize+name_hash_len+10:keysize+name_hash_len+10+sig_len]

+ app_data = b""

+ if len(packet.data) > keysize+name_hash_len+10+sig_len:

+ app_data = packet.data[keysize+name_hash_len+10+sig_len:]

+ signed_data = destination_hash+public_key+name_hash+random_hash+ratchet+app_data

if not len(packet.data) > Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8+10+Identity.SIGLENGTH//8:

app_data = None

@@ -291,6 +368,9 @@ class Identity:

else:

RNS.log("Valid announce for "+RNS.prettyhexrep(destination_hash)+" "+str(packet.hops)+" hops away, received on "+str(packet.receiving_interface)+signal_str, RNS.LOG_EXTREME)

+ if ratchet:

+ Identity._remember_ratchet(destination_hash, ratchet)

return True

else:

@@ -479,7 +559,7 @@ class Identity:

def get_context(self):

return None

- def encrypt(self, plaintext):

+ def encrypt(self, plaintext, ratchet=None):

"""

Encrypts information for the identity.

@@ -491,7 +571,13 @@ class Identity:

ephemeral_key = X25519PrivateKey.generate()

ephemeral_pub_bytes = ephemeral_key.public_key().public_bytes()

- shared_key = ephemeral_key.exchange(self.pub)

+ if ratchet != None:

+ RNS.log(f"Encrypting with ratchet {RNS.hexrep(ratchet)}", RNS.LOG_DEBUG) # TODO: Remove

+ target_public_key = X25519PublicKey.from_public_bytes(ratchet)

+ else:

+ target_public_key = self.pub

+ shared_key = ephemeral_key.exchange(target_public_key)

derived_key = RNS.Cryptography.hkdf(

length=32,

@@ -509,7 +595,7 @@ class Identity:

raise KeyError("Encryption failed because identity does not hold a public key")

- def decrypt(self, ciphertext_token):

+ def decrypt(self, ciphertext_token, ratchets=None):

"""

Decrypts information for the identity.

@@ -523,19 +609,40 @@ class Identity:

try:

peer_pub_bytes = ciphertext_token[:Identity.KEYSIZE//8//2]

peer_pub = X25519PublicKey.from_public_bytes(peer_pub_bytes)

- shared_key = self.prv.exchange(peer_pub)

- derived_key = RNS.Cryptography.hkdf(

- length=32,

- derive_from=shared_key,

- salt=self.get_salt(),

- context=self.get_context(),

- )

- fernet = Fernet(derived_key)

ciphertext = ciphertext_token[Identity.KEYSIZE//8//2:]

- plaintext = fernet.decrypt(ciphertext)

+ if ratchets:

+ for ratchet in ratchets:

+ try:

+ ratchet_prv = X25519PrivateKey.from_private_bytes(ratchet)

+ shared_key = ratchet_prv.exchange(peer_pub)

+ derived_key = RNS.Cryptography.hkdf(

+ length=32,

+ derive_from=shared_key,

+ salt=self.get_salt(),

+ context=self.get_context(),

+ )

+ fernet = Fernet(derived_key)

+ plaintext = fernet.decrypt(ciphertext)

+ RNS.log(f"Decrypted with ratchet {RNS.hexrep(ratchet_prv.public_key().public_bytes())}", RNS.LOG_DEBUG) # TODO: Remove

+ break

+ except Exception as e:

+ pass

+ # RNS.log("Decryption using this ratchet failed", RNS.LOG_DEBUG) # TODO: Remove

+ if plaintext == None:

+ shared_key = self.prv.exchange(peer_pub)

+ derived_key = RNS.Cryptography.hkdf(

+ length=32,

+ derive_from=shared_key,

+ salt=self.get_salt(),

+ context=self.get_context(),

+ )

+ fernet = Fernet(derived_key)

+ plaintext = fernet.decrypt(ciphertext)

except Exception as e:

RNS.log("Decryption by "+RNS.prettyhexrep(self.hash)+" failed: "+str(e), RNS.LOG_DEBUG)

diff --git a/RNS/Link.py b/RNS/Link.py

index 47570171..95fdb123 100644

--- a/RNS/Link.py

+++ b/RNS/Link.py

@@ -1,6 +1,6 @@

# MIT License

# Permission is hereby granted, free of charge, to any person obtaining a copy

# of this software and associated documentation files (the "Software"), to deal

diff --git a/RNS/Packet.py b/RNS/Packet.py

index e47f05b4..4246aca9 100755

--- a/RNS/Packet.py

+++ b/RNS/Packet.py

@@ -1,6 +1,6 @@

# MIT License

# Permission is hereby granted, free of charge, to any person obtaining a copy

# of this software and associated documentation files (the "Software"), to deal

@@ -83,6 +83,10 @@ class Packet:

LRRTT = 0xFE # Packet is a link request round-trip time measurement

LRPROOF = 0xFF # Packet is a link request proof

+ # Context flag values

+ FLAG_SET = 0x01

+ FLAG_UNSET = 0x00

# This is used to calculate allowable

# payload sizes

HEADER_MAXSIZE = RNS.Reticulum.HEADER_MAXSIZE

@@ -102,7 +106,9 @@ class Packet:

TIMEOUT_PER_HOP = RNS.Reticulum.DEFAULT_PER_HOP_TIMEOUT

- def __init__(self, destination, data, packet_type = DATA, context = NONE, transport_type = RNS.Transport.BROADCAST, header_type = HEADER_1, transport_id = None, attached_interface = None, create_receipt = True):

+ def __init__(self, destination, data, packet_type = DATA, context = NONE, transport_type = RNS.Transport.BROADCAST,

+ header_type = HEADER_1, transport_id = None, attached_interface = None, create_receipt = True, context_flag=FLAG_UNSET):

if destination != None:

if transport_type == None:

transport_type = RNS.Transport.BROADCAST

@@ -111,6 +117,7 @@ class Packet:

self.packet_type = packet_type

self.transport_type = transport_type

self.context = context

+ self.context_flag = context_flag

self.hops = 0;

self.destination = destination

@@ -142,9 +149,10 @@ class Packet:

def get_packed_flags(self):

if self.context == Packet.LRPROOF:

- packed_flags = (self.header_type << 6) | (self.transport_type << 4) | (RNS.Destination.LINK << 2) | self.packet_type

+ packed_flags = (self.header_type << 6) | (self.context_flag << 5) | (self.transport_type << 4) | (RNS.Destination.LINK << 2) | self.packet_type

else:

- packed_flags = (self.header_type << 6) | (self.transport_type << 4) | (self.destination.type << 2) | self.packet_type

+ packed_flags = (self.header_type << 6) | (self.context_flag << 5) | (self.transport_type << 4) | (self.destination.type << 2) | self.packet_type

return packed_flags

def pack(self):

@@ -216,7 +224,8 @@ class Packet:

self.hops = self.raw[1]

self.header_type = (self.flags & 0b01000000) >> 6

- self.transport_type = (self.flags & 0b00110000) >> 4

+ self.context_flag = (self.flags & 0b00100000) >> 5

+ self.transport_type = (self.flags & 0b00010000) >> 4

self.destination_type = (self.flags & 0b00001100) >> 2

self.packet_type = (self.flags & 0b00000011)

diff --git a/RNS/Reticulum.py b/RNS/Reticulum.py

index a681a986..d28ca082 100755

--- a/RNS/Reticulum.py

+++ b/RNS/Reticulum.py

@@ -1,6 +1,6 @@

# MIT License

# Permission is hereby granted, free of charge, to any person obtaining a copy

# of this software and associated documentation files (the "Software"), to deal

diff --git a/RNS/Transport.py b/RNS/Transport.py

index f3604602..a8d978be 100755

--- a/RNS/Transport.py

+++ b/RNS/Transport.py

@@ -1,6 +1,6 @@

# MIT License

# Permission is hereby granted, free of charge, to any person obtaining a copy

# of this software and associated documentation files (the "Software"), to deal

@@ -403,7 +403,8 @@ class Transport:

header_type = RNS.Packet.HEADER_2,

transport_type = Transport.TRANSPORT,

transport_id = Transport.identity.hash,

- attached_interface = attached_interface

+ attached_interface = attached_interface,

+ context_flag = packet.context_flag,

)

new_packet.hops = announce_entry[4]

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