electrum

Electrum Bitcoin wallet
git clone https://git.parazyd.org/electrum
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commit 5b1da260410c61c375c688d8adbaaabdfd257cda
parent 5da3820a287e0b79e1c789f55140fb87cab4b9bc
Author: SomberNight <somber.night@protonmail.com>
Date:   Thu, 17 May 2018 14:30:27 +0200

bolt-04: decryption of errors

Diffstat:
Mlib/lnbase.py | 65++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----
Mlib/tests/test_lnbase.py | 16++++++++++++++++
2 files changed, 76 insertions(+), 5 deletions(-)

diff --git a/lib/lnbase.py b/lib/lnbase.py @@ -18,7 +18,7 @@ import time import binascii import hashlib import hmac -from typing import Sequence +from typing import Sequence, Union import cryptography.hazmat.primitives.ciphers.aead as AEAD from cryptography.hazmat.primitives.ciphers import Cipher, algorithms from cryptography.hazmat.backends import default_backend @@ -1617,18 +1617,17 @@ class OnionPacket: def get_bolt04_onion_key(key_type: bytes, secret: bytes) -> bytes: - if key_type not in (b'rho', b'mu', b'um'): + if key_type not in (b'rho', b'mu', b'um', b'ammag'): raise Exception('invalid key_type {}'.format(key_type)) key = hmac.new(key_type, msg=secret, digestmod=hashlib.sha256).digest() return key -def new_onion_packet(payment_path_pubkeys: Sequence[bytes], session_key: bytes, - hops_data: Sequence[OnionHopsDataSingle], associated_data: bytes) -> OnionPacket: +def get_shared_secrets_along_route(payment_path_pubkeys: Sequence[bytes], + session_key: bytes) -> Sequence[bytes]: num_hops = len(payment_path_pubkeys) hop_shared_secrets = num_hops * [b''] ephemeral_key = session_key - # compute shared key for each hop for i in range(0, num_hops): hop_shared_secrets[i] = get_ecdh(ephemeral_key, payment_path_pubkeys[i]) @@ -1638,6 +1637,13 @@ def new_onion_packet(payment_path_pubkeys: Sequence[bytes], session_key: bytes, ephemeral_key_int = int.from_bytes(ephemeral_key, byteorder="big") ephemeral_key_int = ephemeral_key_int * blinding_factor_int % SECP256k1.order ephemeral_key = ephemeral_key_int.to_bytes(32, byteorder="big") + return hop_shared_secrets + + +def new_onion_packet(payment_path_pubkeys: Sequence[bytes], session_key: bytes, + hops_data: Sequence[OnionHopsDataSingle], associated_data: bytes) -> OnionPacket: + num_hops = len(payment_path_pubkeys) + hop_shared_secrets = get_shared_secrets_along_route(payment_path_pubkeys, session_key) filler = generate_filler(b'rho', num_hops, PER_HOP_FULL_SIZE, hop_shared_secrets) mix_header = bytes(HOPS_DATA_SIZE) @@ -1726,6 +1732,55 @@ def process_onion_packet(onion_packet: OnionPacket, associated_data: bytes, are_we_final = False return ProcessedOnionPacket(are_we_final, hop_data, next_onion_packet) + +class FailedToDecodeOnionError(Exception): pass + + +class OnionRoutingFailureMessage: + + def __init__(self, code: int, data: bytes): + self.code = code + self.data = data + + +def _decode_onion_error(error_packet: bytes, payment_path_pubkeys: Sequence[bytes], + session_key: bytes) -> (bytes, int): + """Returns the decoded error bytes, and the index of the sender of the error.""" + num_hops = len(payment_path_pubkeys) + hop_shared_secrets = get_shared_secrets_along_route(payment_path_pubkeys, session_key) + for i in range(num_hops): + ammag_key = get_bolt04_onion_key(b'ammag', hop_shared_secrets[i]) + um_key = get_bolt04_onion_key(b'um', hop_shared_secrets[i]) + stream_bytes = generate_cipher_stream(ammag_key, len(error_packet)) + error_packet = xor_bytes(error_packet, stream_bytes) + hmac_computed = hmac.new(um_key, msg=error_packet[32:], digestmod=hashlib.sha256).digest() + hmac_found = error_packet[:32] + if hmac_computed == hmac_found: + return error_packet, i + raise FailedToDecodeOnionError() + + +def decode_onion_error(error_packet: bytes, payment_path_pubkeys: Sequence[bytes], + session_key: bytes) -> (OnionRoutingFailureMessage, int): + """Returns the failure message, and the index of the sender of the error.""" + decrypted_error, sender_index = _decode_onion_error(error_packet, payment_path_pubkeys, session_key) + failure_msg = get_failure_msg_from_onion_error(decrypted_error) + return failure_msg, sender_index + + +def get_failure_msg_from_onion_error(decrypted_error_packet: bytes) -> OnionRoutingFailureMessage: + # get failure_msg bytes from error packet + failure_len = int.from_bytes(decrypted_error_packet[32:34], byteorder='big') + failure_msg = decrypted_error_packet[34:34+failure_len] + # create failure message object + failure_code = int.from_bytes(failure_msg[:2], byteorder='big') + failure_data = failure_msg[2:] + return OnionRoutingFailureMessage(failure_code, failure_data) + + +# <----- bolt 04, "onion" + + def count_trailing_zeros(index): """ BOLT-03 (where_to_put_secret) """ try: diff --git a/lib/tests/test_lnbase.py b/lib/tests/test_lnbase.py @@ -385,6 +385,22 @@ class Test_LNBase(unittest.TestCase): self.assertEqual(hops_data[i].per_hop.to_bytes(), processed_packet.hop_data.per_hop.to_bytes()) packet = processed_packet.next_packet + def test_decode_onion_error(self): + # test vector from bolt-04 + payment_path_pubkeys = [ + bfh('02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619'), + bfh('0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c'), + bfh('027f31ebc5462c1fdce1b737ecff52d37d75dea43ce11c74d25aa297165faa2007'), + bfh('032c0b7cf95324a07d05398b240174dc0c2be444d96b159aa6c7f7b1e668680991'), + bfh('02edabbd16b41c8371b92ef2f04c1185b4f03b6dcd52ba9b78d9d7c89c8f221145'), + ] + session_key = bfh('4141414141414141414141414141414141414141414141414141414141414141') + error_packet_for_node_0 = bfh('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') + decoded_error, index_of_sender = lnbase._decode_onion_error(error_packet_for_node_0, payment_path_pubkeys, session_key) + self.assertEqual(bfh('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'), + decoded_error) + self.assertEqual(4, index_of_sender) + def test_shachain_store(self): tests = [ {