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Implemented ratchets
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Mark Qvist
parent
c32086c6f1
commit
a11f14e75f
6 changed files with 170 additions and 48 deletions
163
RNS/Identity.py
163
RNS/Identity.py
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@ -1,6 +1,6 @@
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# MIT License
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#
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# Copyright (c) 2016-2023 Mark Qvist / unsigned.io and contributors.
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# Copyright (c) 2016-2024 Mark Qvist / unsigned.io and contributors.
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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@ -50,7 +50,10 @@ class Identity:
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KEYSIZE = 256*2
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"""
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X25519 key size in bits. A complete key is the concatenation of a 256 bit encryption key, and a 256 bit signing key.
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"""
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"""
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RATCHETSIZE = 256
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RATCHET_EXPIRY = 60*60*24*30
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# Non-configurable constants
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FERNET_OVERHEAD = RNS.Cryptography.Fernet.FERNET_OVERHEAD
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@ -67,6 +70,7 @@ class Identity:
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# Storage
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known_destinations = {}
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known_ratchets = {}
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@staticmethod
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def remember(packet_hash, destination_hash, public_key, app_data = None):
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@ -222,29 +226,102 @@ class Identity:
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return Identity.truncated_hash(os.urandom(Identity.TRUNCATED_HASHLENGTH//8))
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@staticmethod
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def generate_ratchet():
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def _ratchet_public_bytes(ratchet):
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return X25519PrivateKey.from_private_bytes(ratchet).public_key().public_bytes()
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@staticmethod
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def _generate_ratchet():
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ratchet_prv = X25519PrivateKey.generate()
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ratchet_pub = ratchet_prv.public_key()
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return ratchet_prv.private_bytes()
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@staticmethod
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def ratchet_public_bytes(ratchet):
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return X25519PrivateKey.from_private_bytes(ratchet).public_key().public_bytes()
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def _remember_ratchet(destination_hash, ratchet):
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RNS.log(f"Remembering ratchet {RNS.hexrep(ratchet)} for {RNS.prettyhexrep(destination_hash)}", RNS.LOG_DEBUG) # TODO: Remove
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try:
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Identity.known_ratchets[destination_hash] = ratchet
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hexhash = RNS.hexrep(destination_hash, delimit=False)
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ratchet_data = {"ratchet": ratchet, "received": time.time()}
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ratchetdir = RNS.Reticulum.storagepath+"/ratchets"
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if not os.path.isdir(ratchetdir):
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os.makedirs(ratchetdir)
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outpath = f"{ratchetdir}/{hexhash}.out"
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finalpath = f"{ratchetdir}/{hexhash}"
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ratchet_file = open(outpath, "wb")
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ratchet_file.write(umsgpack.packb(ratchet_data))
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ratchet_file.close()
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os.rename(outpath, finalpath)
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except Exception as e:
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RNS.log(f"Could not persist ratchet for {RNS.prettyhexrep(destination_hash)} to storage.", RNS.LOG_ERROR)
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RNS.log(f"The contained exception was: {e}")
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RNS.trace_exception(e)
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@staticmethod
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def get_ratchet(destination_hash):
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if not destination_hash in Identity.known_ratchets:
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RNS.log(f"Trying to load ratchet for {RNS.prettyhexrep(destination_hash)} from storage") # TODO: Remove
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ratchetdir = RNS.Reticulum.storagepath+"/ratchets"
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hexhash = RNS.hexrep(destination_hash, delimit=False)
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ratchet_path = f"{ratchetdir}/hexhash"
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if os.path.isfile(ratchet_path):
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try:
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ratchet_file = open(ratchet_path, "rb")
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ratchet_data = umsgpack.unpackb(ratchets_file.read())
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if time.time() < ratchet_data["received"]+Identity.RATCHET_EXPIRY and len(ratchet_data["ratchet"]) == Identity.RATCHETSIZE//8:
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Identity.known_ratchets[destination_hash] = ratchet_data["ratchet"]
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else:
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return None
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except Exception as e:
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RNS.log(f"An error occurred while loading ratchet data for {RNS.prettyhexrep(destination_hash)} from storage.", RNS.LOG_ERROR)
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RNS.log(f"The contained exception was: {e}", RNS.LOG_ERROR)
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return None
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if destination_hash in Identity.known_ratchets:
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return Identity.known_ratchets[destination_hash]
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else:
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return None
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@staticmethod
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def validate_announce(packet, only_validate_signature=False):
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try:
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if packet.packet_type == RNS.Packet.ANNOUNCE:
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keysize = Identity.KEYSIZE//8
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ratchetsize = Identity.RATCHETSIZE//8
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name_hash_len = Identity.NAME_HASH_LENGTH//8
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sig_len = Identity.SIGLENGTH//8
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destination_hash = packet.destination_hash
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public_key = packet.data[:Identity.KEYSIZE//8]
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name_hash = packet.data[Identity.KEYSIZE//8:Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8]
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random_hash = packet.data[Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8:Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8+10]
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signature = packet.data[Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8+10:Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8+10+Identity.SIGLENGTH//8]
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app_data = b""
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if len(packet.data) > Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8+10+Identity.SIGLENGTH//8:
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app_data = packet.data[Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8+10+Identity.SIGLENGTH//8:]
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signed_data = destination_hash+public_key+name_hash+random_hash+app_data
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# Get public key bytes from announce
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public_key = packet.data[:keysize]
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# If the packet context flag is set,
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# this announce contains a new ratchet
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if packet.context_flag == RNS.Packet.FLAG_SET:
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name_hash = packet.data[keysize:keysize+name_hash_len ]
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random_hash = packet.data[keysize+name_hash_len:keysize+name_hash_len+10]
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ratchet = packet.data[keysize+name_hash_len+10:keysize+name_hash_len+10+ratchetsize]
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signature = packet.data[keysize+name_hash_len+10+ratchetsize:keysize+name_hash_len+10+ratchetsize+sig_len]
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app_data = b""
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if len(packet.data) > keysize+name_hash_len+10+sig_len+ratchetsize:
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app_data = packet.data[keysize+name_hash_len+10+sig_len+ratchetsize:]
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# If the packet context flag is not set,
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# this announce does not contain a ratchet
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else:
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ratchet = b""
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name_hash = packet.data[keysize:keysize+name_hash_len]
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random_hash = packet.data[keysize+name_hash_len:keysize+name_hash_len+10]
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signature = packet.data[keysize+name_hash_len+10:keysize+name_hash_len+10+sig_len]
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app_data = b""
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if len(packet.data) > keysize+name_hash_len+10+sig_len:
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app_data = packet.data[keysize+name_hash_len+10+sig_len:]
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signed_data = destination_hash+public_key+name_hash+random_hash+ratchet+app_data
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if not len(packet.data) > Identity.KEYSIZE//8+Identity.NAME_HASH_LENGTH//8+10+Identity.SIGLENGTH//8:
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app_data = None
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@ -291,6 +368,9 @@ class Identity:
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else:
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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)
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if ratchet:
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Identity._remember_ratchet(destination_hash, ratchet)
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return True
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else:
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@ -479,7 +559,7 @@ class Identity:
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def get_context(self):
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return None
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def encrypt(self, plaintext):
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def encrypt(self, plaintext, ratchet=None):
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"""
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Encrypts information for the identity.
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@ -491,7 +571,13 @@ class Identity:
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ephemeral_key = X25519PrivateKey.generate()
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ephemeral_pub_bytes = ephemeral_key.public_key().public_bytes()
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shared_key = ephemeral_key.exchange(self.pub)
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if ratchet != None:
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RNS.log(f"Encrypting with ratchet {RNS.hexrep(ratchet)}", RNS.LOG_DEBUG) # TODO: Remove
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target_public_key = X25519PublicKey.from_public_bytes(ratchet)
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else:
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target_public_key = self.pub
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shared_key = ephemeral_key.exchange(target_public_key)
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derived_key = RNS.Cryptography.hkdf(
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length=32,
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@ -509,7 +595,7 @@ class Identity:
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raise KeyError("Encryption failed because identity does not hold a public key")
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def decrypt(self, ciphertext_token):
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def decrypt(self, ciphertext_token, ratchets=None):
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"""
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Decrypts information for the identity.
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@ -523,19 +609,40 @@ class Identity:
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try:
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peer_pub_bytes = ciphertext_token[:Identity.KEYSIZE//8//2]
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peer_pub = X25519PublicKey.from_public_bytes(peer_pub_bytes)
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shared_key = self.prv.exchange(peer_pub)
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derived_key = RNS.Cryptography.hkdf(
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length=32,
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derive_from=shared_key,
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salt=self.get_salt(),
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context=self.get_context(),
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)
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fernet = Fernet(derived_key)
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ciphertext = ciphertext_token[Identity.KEYSIZE//8//2:]
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plaintext = fernet.decrypt(ciphertext)
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if ratchets:
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for ratchet in ratchets:
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try:
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ratchet_prv = X25519PrivateKey.from_private_bytes(ratchet)
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shared_key = ratchet_prv.exchange(peer_pub)
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derived_key = RNS.Cryptography.hkdf(
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length=32,
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derive_from=shared_key,
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salt=self.get_salt(),
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context=self.get_context(),
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)
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fernet = Fernet(derived_key)
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plaintext = fernet.decrypt(ciphertext)
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RNS.log(f"Decrypted with ratchet {RNS.hexrep(ratchet_prv.public_key().public_bytes())}", RNS.LOG_DEBUG) # TODO: Remove
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break
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except Exception as e:
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pass
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# RNS.log("Decryption using this ratchet failed", RNS.LOG_DEBUG) # TODO: Remove
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if plaintext == None:
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shared_key = self.prv.exchange(peer_pub)
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derived_key = RNS.Cryptography.hkdf(
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length=32,
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derive_from=shared_key,
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salt=self.get_salt(),
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context=self.get_context(),
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)
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fernet = Fernet(derived_key)
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plaintext = fernet.decrypt(ciphertext)
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except Exception as e:
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RNS.log("Decryption by "+RNS.prettyhexrep(self.hash)+" failed: "+str(e), RNS.LOG_DEBUG)
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