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525 lines
22 KiB
525 lines
22 KiB
# -*- coding: utf-8 -*-
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#
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# Electrum - lightweight Bitcoin client
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# Copyright (C) 2018 The Electrum developers
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#
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# Permission is hereby granted, free of charge, to any person
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# obtaining a copy of this software and associated documentation files
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# (the "Software"), to deal in the Software without restriction,
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# including without limitation the rights to use, copy, modify, merge,
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# publish, distribute, sublicense, and/or sell copies of the Software,
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# and to permit persons to whom the Software is furnished to do so,
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# subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be
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# included in all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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import queue
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import traceback
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import sys
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import binascii
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import hashlib
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import hmac
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from collections import namedtuple, defaultdict
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from typing import Sequence, Union, Tuple
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from cryptography.hazmat.primitives.ciphers import Cipher, algorithms
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from cryptography.hazmat.backends import default_backend
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from . import bitcoin
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from . import ecc
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from . import crypto
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from .crypto import sha256
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from .util import PrintError, bh2u, profiler, xor_bytes
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from .lnutil import get_ecdh
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class ChannelInfo(PrintError):
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def __init__(self, channel_announcement_payload):
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self.channel_id = channel_announcement_payload['short_channel_id']
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self.node_id_1 = channel_announcement_payload['node_id_1']
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self.node_id_2 = channel_announcement_payload['node_id_2']
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assert type(self.node_id_1) is bytes
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assert type(self.node_id_2) is bytes
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assert list(sorted([self.node_id_1, self.node_id_2])) == [self.node_id_1, self.node_id_2]
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self.capacity_sat = None
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self.policy_node1 = None
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self.policy_node2 = None
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def set_capacity(self, capacity):
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# TODO call this after looking up UTXO for funding txn on chain
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self.capacity_sat = capacity
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def on_channel_update(self, msg_payload):
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assert self.channel_id == msg_payload['short_channel_id']
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flags = int.from_bytes(msg_payload['flags'], 'big')
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direction = flags & 1
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if direction == 0:
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self.policy_node1 = ChannelInfoDirectedPolicy(msg_payload)
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else:
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self.policy_node2 = ChannelInfoDirectedPolicy(msg_payload)
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self.print_error('channel update', binascii.hexlify(self.channel_id).decode("ascii"), flags)
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def get_policy_for_node(self, node_id):
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if node_id == self.node_id_1:
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return self.policy_node1
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elif node_id == self.node_id_2:
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return self.policy_node2
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else:
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raise Exception('node_id {} not in channel {}'.format(node_id, self.channel_id))
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class ChannelInfoDirectedPolicy:
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def __init__(self, channel_update_payload):
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self.cltv_expiry_delta = channel_update_payload['cltv_expiry_delta']
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self.htlc_minimum_msat = channel_update_payload['htlc_minimum_msat']
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self.fee_base_msat = channel_update_payload['fee_base_msat']
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self.fee_proportional_millionths = channel_update_payload['fee_proportional_millionths']
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self.cltv_expiry_delta = int.from_bytes(self.cltv_expiry_delta, "big")
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self.htlc_minimum_msat = int.from_bytes(self.htlc_minimum_msat, "big")
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self.fee_base_msat = int.from_bytes(self.fee_base_msat, "big")
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self.fee_proportional_millionths = int.from_bytes(self.fee_proportional_millionths, "big")
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class ChannelDB(PrintError):
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def __init__(self):
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self._id_to_channel_info = {}
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self._channels_for_node = defaultdict(set) # node -> set(short_channel_id)
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def get_channel_info(self, channel_id):
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return self._id_to_channel_info.get(channel_id, None)
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def get_channels_for_node(self, node_id):
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"""Returns the set of channels that have node_id as one of the endpoints."""
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return self._channels_for_node[node_id]
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def on_channel_announcement(self, msg_payload):
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short_channel_id = msg_payload['short_channel_id']
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self.print_error('channel announcement', binascii.hexlify(short_channel_id).decode("ascii"))
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channel_info = ChannelInfo(msg_payload)
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self._id_to_channel_info[short_channel_id] = channel_info
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self._channels_for_node[channel_info.node_id_1].add(short_channel_id)
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self._channels_for_node[channel_info.node_id_2].add(short_channel_id)
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def on_channel_update(self, msg_payload):
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short_channel_id = msg_payload['short_channel_id']
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try:
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channel_info = self._id_to_channel_info[short_channel_id]
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except KeyError:
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self.print_error("could not find", short_channel_id)
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else:
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channel_info.on_channel_update(msg_payload)
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def remove_channel(self, short_channel_id):
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try:
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channel_info = self._id_to_channel_info[short_channel_id]
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except KeyError:
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self.print_error('cannot find channel {}'.format(short_channel_id))
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return
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self._id_to_channel_info.pop(short_channel_id, None)
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for node in (channel_info.node_id_1, channel_info.node_id_2):
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try:
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self._channels_for_node[node].remove(short_channel_id)
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except KeyError:
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pass
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class RouteEdge:
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def __init__(self, node_id: bytes, short_channel_id: bytes,
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channel_policy: ChannelInfoDirectedPolicy):
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# "if you travel through short_channel_id, you will reach node_id"
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self.node_id = node_id
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self.short_channel_id = short_channel_id
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self.channel_policy = channel_policy
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class LNPathFinder(PrintError):
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def __init__(self, channel_db):
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self.channel_db = channel_db
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self.blacklist = set()
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def _edge_cost(self, short_channel_id: bytes, start_node: bytes, payment_amt_msat: int,
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ignore_cltv=False) -> float:
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"""Heuristic cost of going through a channel.
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direction: 0 or 1. --- 0 means node_id_1 -> node_id_2
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"""
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channel_info = self.channel_db.get_channel_info(short_channel_id)
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if channel_info is None:
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return float('inf')
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channel_policy = channel_info.get_policy_for_node(start_node)
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if channel_policy is None: return float('inf')
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cltv_expiry_delta = channel_policy.cltv_expiry_delta
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htlc_minimum_msat = channel_policy.htlc_minimum_msat
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fee_base_msat = channel_policy.fee_base_msat
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fee_proportional_millionths = channel_policy.fee_proportional_millionths
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if payment_amt_msat is not None:
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if payment_amt_msat < htlc_minimum_msat:
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return float('inf') # payment amount too little
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if channel_info.capacity_sat is not None and \
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payment_amt_msat // 1000 > channel_info.capacity_sat:
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return float('inf') # payment amount too large
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amt = payment_amt_msat or 50000 * 1000 # guess for typical payment amount
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fee_msat = fee_base_msat + amt * fee_proportional_millionths / 1000000
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# TODO revise
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# paying 10 more satoshis ~ waiting one more block
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fee_cost = fee_msat / 1000 / 10
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cltv_cost = cltv_expiry_delta if not ignore_cltv else 0
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return cltv_cost + fee_cost + 1
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@profiler
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def find_path_for_payment(self, from_node_id: bytes, to_node_id: bytes,
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amount_msat: int=None) -> Sequence[Tuple[bytes, bytes]]:
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"""Return a path between from_node_id and to_node_id.
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Returns a list of (node_id, short_channel_id) representing a path.
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To get from node ret[n][0] to ret[n+1][0], use channel ret[n+1][1];
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i.e. an element reads as, "to get to node_id, travel through short_channel_id"
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"""
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if amount_msat is not None: assert type(amount_msat) is int
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# TODO find multiple paths??
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# run Dijkstra
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distance_from_start = defaultdict(lambda: float('inf'))
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distance_from_start[from_node_id] = 0
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prev_node = {}
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nodes_to_explore = queue.PriorityQueue()
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nodes_to_explore.put((0, from_node_id))
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while nodes_to_explore.qsize() > 0:
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dist_to_cur_node, cur_node = nodes_to_explore.get()
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if cur_node == to_node_id:
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break
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if dist_to_cur_node != distance_from_start[cur_node]:
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# queue.PriorityQueue does not implement decrease_priority,
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# so instead of decreasing priorities, we add items again into the queue.
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# so there are duplicates in the queue, that we discard now:
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continue
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for edge_channel_id in self.channel_db.get_channels_for_node(cur_node):
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if edge_channel_id in self.blacklist: continue
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channel_info = self.channel_db.get_channel_info(edge_channel_id)
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node1, node2 = channel_info.node_id_1, channel_info.node_id_2
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neighbour = node2 if node1 == cur_node else node1
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ignore_cltv_delta_in_edge_cost = cur_node == from_node_id
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edge_cost = self._edge_cost(edge_channel_id, cur_node, amount_msat,
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ignore_cltv=ignore_cltv_delta_in_edge_cost)
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alt_dist_to_neighbour = distance_from_start[cur_node] + edge_cost
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if alt_dist_to_neighbour < distance_from_start[neighbour]:
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distance_from_start[neighbour] = alt_dist_to_neighbour
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prev_node[neighbour] = cur_node, edge_channel_id
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nodes_to_explore.put((alt_dist_to_neighbour, neighbour))
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else:
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return None # no path found
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# backtrack from end to start
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cur_node = to_node_id
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path = []
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while cur_node != from_node_id:
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prev_node_id, edge_taken = prev_node[cur_node]
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path += [(cur_node, edge_taken)]
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cur_node = prev_node_id
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path.reverse()
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return path
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def create_route_from_path(self, path, from_node_id: bytes) -> Sequence[RouteEdge]:
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assert type(from_node_id) is bytes
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if path is None:
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raise Exception('cannot create route from None path')
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route = []
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prev_node_id = from_node_id
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for node_id, short_channel_id in path:
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channel_info = self.channel_db.get_channel_info(short_channel_id)
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if channel_info is None:
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raise Exception('cannot find channel info for short_channel_id: {}'.format(bh2u(short_channel_id)))
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channel_policy = channel_info.get_policy_for_node(prev_node_id)
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if channel_policy is None:
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raise Exception('cannot find channel policy for short_channel_id: {}'.format(bh2u(short_channel_id)))
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route.append(RouteEdge(node_id, short_channel_id, channel_policy))
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prev_node_id = node_id
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return route
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# bolt 04, "onion" ----->
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NUM_MAX_HOPS_IN_PATH = 20
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HOPS_DATA_SIZE = 1300 # also sometimes called routingInfoSize in bolt-04
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PER_HOP_FULL_SIZE = 65 # HOPS_DATA_SIZE / 20
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NUM_STREAM_BYTES = HOPS_DATA_SIZE + PER_HOP_FULL_SIZE
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PER_HOP_HMAC_SIZE = 32
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class UnsupportedOnionPacketVersion(Exception): pass
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class InvalidOnionMac(Exception): pass
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class OnionPerHop:
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def __init__(self, short_channel_id: bytes, amt_to_forward: bytes, outgoing_cltv_value: bytes):
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self.short_channel_id = short_channel_id
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self.amt_to_forward = amt_to_forward
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self.outgoing_cltv_value = outgoing_cltv_value
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def to_bytes(self) -> bytes:
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ret = self.short_channel_id
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ret += self.amt_to_forward
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ret += self.outgoing_cltv_value
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ret += bytes(12) # padding
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if len(ret) != 32:
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raise Exception('unexpected length {}'.format(len(ret)))
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return ret
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@classmethod
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def from_bytes(cls, b: bytes):
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if len(b) != 32:
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raise Exception('unexpected length {}'.format(len(b)))
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return OnionPerHop(
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short_channel_id=b[:8],
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amt_to_forward=b[8:16],
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outgoing_cltv_value=b[16:20]
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)
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class OnionHopsDataSingle: # called HopData in lnd
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def __init__(self, per_hop: OnionPerHop = None):
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self.realm = 0
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self.per_hop = per_hop
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self.hmac = None
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def to_bytes(self) -> bytes:
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ret = bytes([self.realm])
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ret += self.per_hop.to_bytes()
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ret += self.hmac if self.hmac is not None else bytes(PER_HOP_HMAC_SIZE)
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if len(ret) != PER_HOP_FULL_SIZE:
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raise Exception('unexpected length {}'.format(len(ret)))
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return ret
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@classmethod
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def from_bytes(cls, b: bytes):
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if len(b) != PER_HOP_FULL_SIZE:
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raise Exception('unexpected length {}'.format(len(b)))
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ret = OnionHopsDataSingle()
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ret.realm = b[0]
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if ret.realm != 0:
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raise Exception('only realm 0 is supported')
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ret.per_hop = OnionPerHop.from_bytes(b[1:33])
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ret.hmac = b[33:]
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return ret
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class OnionPacket:
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def __init__(self, public_key: bytes, hops_data: bytes, hmac: bytes):
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self.version = 0
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self.public_key = public_key
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self.hops_data = hops_data # also called RoutingInfo in bolt-04
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self.hmac = hmac
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def to_bytes(self) -> bytes:
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ret = bytes([self.version])
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ret += self.public_key
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ret += self.hops_data
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ret += self.hmac
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if len(ret) != 1366:
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raise Exception('unexpected length {}'.format(len(ret)))
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return ret
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@classmethod
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def from_bytes(cls, b: bytes):
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if len(b) != 1366:
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raise Exception('unexpected length {}'.format(len(b)))
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version = b[0]
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if version != 0:
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raise UnsupportedOnionPacketVersion('version {} is not supported'.format(version))
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return OnionPacket(
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public_key=b[1:34],
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hops_data=b[34:1334],
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hmac=b[1334:]
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)
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def get_bolt04_onion_key(key_type: bytes, secret: bytes) -> bytes:
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if key_type not in (b'rho', b'mu', b'um', b'ammag'):
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raise Exception('invalid key_type {}'.format(key_type))
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key = hmac.new(key_type, msg=secret, digestmod=hashlib.sha256).digest()
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return key
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def get_shared_secrets_along_route(payment_path_pubkeys: Sequence[bytes],
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session_key: bytes) -> Sequence[bytes]:
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num_hops = len(payment_path_pubkeys)
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hop_shared_secrets = num_hops * [b'']
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ephemeral_key = session_key
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# compute shared key for each hop
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for i in range(0, num_hops):
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hop_shared_secrets[i] = get_ecdh(ephemeral_key, payment_path_pubkeys[i])
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ephemeral_pubkey = ecc.ECPrivkey(ephemeral_key).get_public_key_bytes()
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blinding_factor = sha256(ephemeral_pubkey + hop_shared_secrets[i])
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blinding_factor_int = int.from_bytes(blinding_factor, byteorder="big")
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ephemeral_key_int = int.from_bytes(ephemeral_key, byteorder="big")
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ephemeral_key_int = ephemeral_key_int * blinding_factor_int % ecc.CURVE_ORDER
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ephemeral_key = ephemeral_key_int.to_bytes(32, byteorder="big")
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return hop_shared_secrets
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def new_onion_packet(payment_path_pubkeys: Sequence[bytes], session_key: bytes,
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hops_data: Sequence[OnionHopsDataSingle], associated_data: bytes) -> OnionPacket:
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num_hops = len(payment_path_pubkeys)
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hop_shared_secrets = get_shared_secrets_along_route(payment_path_pubkeys, session_key)
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filler = generate_filler(b'rho', num_hops, PER_HOP_FULL_SIZE, hop_shared_secrets)
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mix_header = bytes(HOPS_DATA_SIZE)
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next_hmac = bytes(PER_HOP_HMAC_SIZE)
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# compute routing info and MAC for each hop
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for i in range(num_hops-1, -1, -1):
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rho_key = get_bolt04_onion_key(b'rho', hop_shared_secrets[i])
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mu_key = get_bolt04_onion_key(b'mu', hop_shared_secrets[i])
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hops_data[i].hmac = next_hmac
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stream_bytes = generate_cipher_stream(rho_key, NUM_STREAM_BYTES)
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mix_header = mix_header[:-PER_HOP_FULL_SIZE]
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mix_header = hops_data[i].to_bytes() + mix_header
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mix_header = xor_bytes(mix_header, stream_bytes)
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if i == num_hops - 1 and len(filler) != 0:
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mix_header = mix_header[:-len(filler)] + filler
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packet = mix_header + associated_data
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next_hmac = hmac.new(mu_key, msg=packet, digestmod=hashlib.sha256).digest()
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return OnionPacket(
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public_key=ecc.ECPrivkey(session_key).get_public_key_bytes(),
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hops_data=mix_header,
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hmac=next_hmac)
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def generate_filler(key_type: bytes, num_hops: int, hop_size: int,
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shared_secrets: Sequence[bytes]) -> bytes:
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filler_size = (NUM_MAX_HOPS_IN_PATH + 1) * hop_size
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filler = bytearray(filler_size)
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for i in range(0, num_hops-1): # -1, as last hop does not obfuscate
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filler = filler[hop_size:]
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filler += bytearray(hop_size)
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stream_key = get_bolt04_onion_key(key_type, shared_secrets[i])
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stream_bytes = generate_cipher_stream(stream_key, filler_size)
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filler = xor_bytes(filler, stream_bytes)
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return filler[(NUM_MAX_HOPS_IN_PATH-num_hops+2)*hop_size:]
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def generate_cipher_stream(stream_key: bytes, num_bytes: int) -> bytes:
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algo = algorithms.ChaCha20(stream_key, nonce=bytes(16))
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cipher = Cipher(algo, mode=None, backend=default_backend())
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encryptor = cipher.encryptor()
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return encryptor.update(bytes(num_bytes))
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ProcessedOnionPacket = namedtuple("ProcessedOnionPacket", ["are_we_final", "hop_data", "next_packet"])
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# TODO replay protection
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def process_onion_packet(onion_packet: OnionPacket, associated_data: bytes,
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our_onion_private_key: bytes) -> ProcessedOnionPacket:
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shared_secret = get_ecdh(our_onion_private_key, onion_packet.public_key)
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# check message integrity
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mu_key = get_bolt04_onion_key(b'mu', shared_secret)
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calculated_mac = hmac.new(mu_key, msg=onion_packet.hops_data+associated_data,
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digestmod=hashlib.sha256).digest()
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if onion_packet.hmac != calculated_mac:
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raise InvalidOnionMac()
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# peel an onion layer off
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rho_key = get_bolt04_onion_key(b'rho', shared_secret)
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stream_bytes = generate_cipher_stream(rho_key, NUM_STREAM_BYTES)
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padded_header = onion_packet.hops_data + bytes(PER_HOP_FULL_SIZE)
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next_hops_data = xor_bytes(padded_header, stream_bytes)
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# calc next ephemeral key
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blinding_factor = sha256(onion_packet.public_key + shared_secret)
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blinding_factor_int = int.from_bytes(blinding_factor, byteorder="big")
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next_public_key_int = ecc.ECPubkey(onion_packet.public_key) * blinding_factor_int
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next_public_key = next_public_key_int.get_public_key_bytes()
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hop_data = OnionHopsDataSingle.from_bytes(next_hops_data[:PER_HOP_FULL_SIZE])
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next_onion_packet = OnionPacket(
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public_key=next_public_key,
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hops_data=next_hops_data[PER_HOP_FULL_SIZE:],
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hmac=hop_data.hmac
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)
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if hop_data.hmac == bytes(PER_HOP_HMAC_SIZE):
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# we are the destination / exit node
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are_we_final = True
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else:
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# we are an intermediate node; forwarding
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are_we_final = False
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return ProcessedOnionPacket(are_we_final, hop_data, next_onion_packet)
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class FailedToDecodeOnionError(Exception): pass
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class OnionRoutingFailureMessage:
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def __init__(self, code: int, data: bytes):
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self.code = code
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self.data = data
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def __repr__(self):
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return repr((self.code, self.data))
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def _decode_onion_error(error_packet: bytes, payment_path_pubkeys: Sequence[bytes],
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session_key: bytes) -> (bytes, int):
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"""Returns the decoded error bytes, and the index of the sender of the error."""
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num_hops = len(payment_path_pubkeys)
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hop_shared_secrets = get_shared_secrets_along_route(payment_path_pubkeys, session_key)
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for i in range(num_hops):
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ammag_key = get_bolt04_onion_key(b'ammag', hop_shared_secrets[i])
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um_key = get_bolt04_onion_key(b'um', hop_shared_secrets[i])
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stream_bytes = generate_cipher_stream(ammag_key, len(error_packet))
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error_packet = xor_bytes(error_packet, stream_bytes)
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hmac_computed = hmac.new(um_key, msg=error_packet[32:], digestmod=hashlib.sha256).digest()
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hmac_found = error_packet[:32]
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if hmac_computed == hmac_found:
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return error_packet, i
|
|
raise FailedToDecodeOnionError()
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def decode_onion_error(error_packet: bytes, payment_path_pubkeys: Sequence[bytes],
|
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session_key: bytes) -> (OnionRoutingFailureMessage, int):
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"""Returns the failure message, and the index of the sender of the error."""
|
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decrypted_error, sender_index = _decode_onion_error(error_packet, payment_path_pubkeys, session_key)
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failure_msg = get_failure_msg_from_onion_error(decrypted_error)
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return failure_msg, sender_index
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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:]
|
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return OnionRoutingFailureMessage(failure_code, failure_data)
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# <----- bolt 04, "onion"
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