network: randomise the order of address subscriptions

Before this, we were subscribing to our addresses in their bip32 order,
leaking this information to servers. While this leak seems mostly harmless,
it is trivial to fix.

electrum/lnwatcher.py

@@ -11,7 +11,7 @@ from typing import NamedTuple, Dict
 from . import util
 from .sql_db import SqlDB, sql
 from .wallet_db import WalletDB
-from .util import bh2u, bfh, log_exceptions, ignore_exceptions, TxMinedInfo
+from .util import bh2u, bfh, log_exceptions, ignore_exceptions, TxMinedInfo, random_shuffled_copy
 from .address_synchronizer import AddressSynchronizer, TX_HEIGHT_LOCAL, TX_HEIGHT_UNCONF_PARENT, TX_HEIGHT_UNCONFIRMED
 from .transaction import Transaction, TxOutpoint
 
@@ -278,8 +278,8 @@ class WatchTower(LNWatcher):
 
     async def start_watching(self):
         # I need to watch the addresses from sweepstore
-        l = await self.sweepstore.list_channels()
+        lst = await self.sweepstore.list_channels()
-        for outpoint, address in l:
+        for outpoint, address in random_shuffled_copy(lst):
             self.add_channel(outpoint, address)
 
     async def do_breach_remedy(self, funding_outpoint, closing_tx, spenders):

electrum/lnworker.py

@@ -35,7 +35,7 @@ from .crypto import sha256
 from .bip32 import BIP32Node
 from .util import bh2u, bfh, InvoiceError, resolve_dns_srv, is_ip_address, log_exceptions
 from .util import ignore_exceptions, make_aiohttp_session, SilentTaskGroup
-from .util import timestamp_to_datetime
+from .util import timestamp_to_datetime, random_shuffled_copy
 from .util import MyEncoder
 from .logging import Logger
 from .lntransport import LNTransport, LNResponderTransport
@@ -499,7 +499,7 @@ class LNWallet(LNWorker):
         # note: accessing channels (besides simple lookup) needs self.lock!
         self._channels = {}  # type: Dict[bytes, Channel]
         channels = self.db.get_dict("channels")
-        for channel_id, c in channels.items():
+        for channel_id, c in random_shuffled_copy(channels.items()):
             self._channels[bfh(channel_id)] = Channel(c, sweep_address=self.sweep_address, lnworker=self)
 
         self.pending_payments = defaultdict(asyncio.Future)  # type: Dict[bytes, asyncio.Future[BarePaymentAttemptLog]]
@@ -1397,7 +1397,7 @@ class LNBackups(Logger):
         self.wallet = wallet
         self.db = wallet.db
         self.channel_backups = {}
-        for channel_id, cb in self.db.get_dict("channel_backups").items():
+        for channel_id, cb in random_shuffled_copy(self.db.get_dict("channel_backups").items()):
             self.channel_backups[bfh(channel_id)] = ChannelBackup(cb, sweep_address=self.sweep_address, lnworker=self)
 
     @property

electrum/synchronizer.py

@@ -32,7 +32,7 @@ from aiorpcx import TaskGroup, run_in_thread, RPCError
 
 from . import util
 from .transaction import Transaction, PartialTransaction
-from .util import bh2u, make_aiohttp_session, NetworkJobOnDefaultServer
+from .util import bh2u, make_aiohttp_session, NetworkJobOnDefaultServer, random_shuffled_copy
 from .bitcoin import address_to_scripthash, is_address
 from .network import UntrustedServerReturnedError
 from .logging import Logger
@@ -240,7 +240,7 @@ class Synchronizer(SynchronizerBase):
             if history == ['*']: continue
             await self._request_missing_txs(history, allow_server_not_finding_tx=True)
         # add addresses to bootstrap
-        for addr in self.wallet.get_addresses():
+        for addr in random_shuffled_copy(self.wallet.get_addresses()):
             await self._add_address(addr)
         # main loop
         while True:

electrum/util.py

@@ -24,7 +24,7 @@ import binascii
 import os, sys, re, json
 from collections import defaultdict, OrderedDict
 from typing import (NamedTuple, Union, TYPE_CHECKING, Tuple, Optional, Callable, Any,
-                    Sequence, Dict, Generic, TypeVar)
+                    Sequence, Dict, Generic, TypeVar, List, Iterable)
 from datetime import datetime
 import decimal
 from decimal import Decimal
@@ -1398,3 +1398,12 @@ class JsonRPCClient:
         async def coro(*args):
             return await self.request(endpoint, *args)
         setattr(self, endpoint, coro)
+
+
+T = TypeVar('T')
+
+def random_shuffled_copy(x: Iterable[T]) -> List[T]:
+    """Returns a shuffled copy of the input."""
+    x_copy = list(x)  # copy
+    random.shuffle(x_copy)  # shuffle in-place
+    return x_copy