davide/purple-electrumwallet
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onion_message: let caller specify considered channels for blinded paths.

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This allows restricting blinded paths to channels that have sufficient receive
capacity for payment.

NOTE: this might have privacy issues, as this can be used to probe channel capacity.
Maybe randomize leeway?

@f321x: changed to use scid alias in create_blinded_path
This commit is contained in:
Sander van Grieken
2025-11-18 16:43:20 +01:00
committed by f321x
parent 2b6ad68145
commit 3e3bffa4a2
1 changed files with 27 additions and 18 deletions
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electrum/onion_message.py
+27 -18
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@@ -56,6 +56,7 @@ if TYPE_CHECKING:
from electrum.network import Network
from electrum.lnrouter import NodeInfo
from electrum.lntransport import LNPeerAddr
from electrum.lnchannel import Channel
from asyncio import Task
logger = get_logger(__name__)
@@ -77,7 +78,8 @@ def create_blinded_path(
final_recipient_data: dict,
*,
hop_extras: Optional[Sequence[dict]] = None,
dummy_hops: Optional[int] = 0
dummy_hops: Optional[int] = 0,
channels: Optional[Sequence['Channel']] = None,
) -> dict:
# dummy hops could be inserted anywhere in the path, but for compatibility just add them at the end
# because blinded paths are usually constructed towards ourselves, and we know we can handle dummy hops.
@@ -96,10 +98,18 @@ def create_blinded_path(
if is_non_final_node:
# spec: alt: short_channel_id instead of next_node_id
recipient_data = {
# TODO: SHOULD add padding data to ensure all encrypted_data_tlv(i) have the same length
'next_node_id': {'node_id': path[i+1]}
}
if channels: # use short_channel_id for payments
scid = channels[i].get_remote_scid_alias() or channels[i].short_channel_id
recipient_data = {
# TODO: SHOULD add padding data to ensure all encrypted_data_tlv(i) have the same length
'short_channel_id': {'short_channel_id': scid}
}
else:
recipient_data = {
# TODO: SHOULD add padding data to ensure all encrypted_data_tlv(i) have the same length
'next_node_id': {'node_id': path[i+1]}
}
if hop_extras and i < len(hop_extras): # extra hop data for debugging for now
recipient_data.update(hop_extras[i])
else:
@@ -382,13 +392,11 @@ def get_blinded_reply_paths(
path_id: bytes,
*,
max_paths: int = REQUEST_REPLY_PATHS_MAX,
preferred_node_id: bytes = None
) -> Sequence[dict]:
"""construct a list of blinded reply-paths for onion message.
"""
mydata = {'path_id': {'data': path_id}} # same path_id used in every reply path
paths, payinfo = get_blinded_paths_to_me(lnwallet, mydata, max_paths=max_paths,
preferred_node_id=preferred_node_id, onion_message=True)
paths, payinfo = get_blinded_paths_to_me(lnwallet, mydata, max_paths=max_paths, onion_message=True)
return paths
@@ -397,7 +405,7 @@ def get_blinded_paths_to_me(
final_recipient_data: dict,
*,
max_paths: int = PAYMENT_PATHS_MAX,
preferred_node_id: bytes = None,
my_channels: Optional[Sequence['Channel']] = None,
onion_message: bool = False
) -> Tuple[Sequence[dict], Sequence[dict]]:
"""construct a list of blinded paths.
@@ -405,13 +413,14 @@ def get_blinded_paths_to_me(
- uses channels peers if not onion_message
- uses current onion_message capable channel peers if exist and if onion_message
- otherwise, uses current onion_message capable peers if onion_message
- prefers preferred_node_id if given
- reply_path introduction points are direct peers only (TODO: longer paths)"""
# TODO: build longer paths and/or add dummy hops to increase privacy
my_active_channels = [chan for chan in lnwallet.channels.values() if chan.is_active()]
my_channels = my_active_channels
if not my_channels:
my_active_channels = [chan for chan in lnwallet.channels.values() if chan.is_active()]
my_channels = my_active_channels
if onion_message:
my_channels = [chan for chan in my_active_channels if lnwallet.lnpeermgr.get_peer_by_pubkey(chan.node_id) and
my_channels = [chan for chan in my_channels if lnwallet.lnpeermgr.get_peer_by_pubkey(chan.node_id) and
lnwallet.lnpeermgr.get_peer_by_pubkey(chan.node_id).their_features.supports(LnFeatures.OPTION_ONION_MESSAGE_OPT)]
result = []
@@ -420,8 +429,8 @@ def get_blinded_paths_to_me(
local_height = lnwallet.network.get_local_height()
if len(my_channels):
# randomize list, but prefer preferred_node_id
rchans = sorted(my_channels, key=lambda x: random() if x.node_id != preferred_node_id else 0)
# randomize list
rchans = sorted(my_channels, key=lambda x: random())
for chan in rchans[:max_paths]:
hop_extras = None
if not onion_message: # add hop_extras and payinfo, assumption: len(blinded_path) == 2 (us and peer)
@@ -470,15 +479,15 @@ def get_blinded_paths_to_me(
'features': bytes(0)
})
blinded_path = create_blinded_path(os.urandom(32), [chan.node_id, mynodeid], final_recipient_data,
hop_extras=hop_extras)
hop_extras=hop_extras, channels=[chan] if not onion_message else None)
result.append(blinded_path)
elif onion_message:
# we can use peers even without channels for onion messages
my_onionmsg_peers = [peer for peer in lnwallet.lnpeermgr.peers.values() if
peer.their_features.supports(LnFeatures.OPTION_ONION_MESSAGE_OPT)]
if len(my_onionmsg_peers):
# randomize list, but prefer preferred_node_id
rpeers = sorted(my_onionmsg_peers, key=lambda x: random() if x.pubkey != preferred_node_id else 0)
# randomize list
rpeers = sorted(my_onionmsg_peers, key=lambda x: random())
for peer in rpeers[:max_paths]:
blinded_path = create_blinded_path(os.urandom(32), [peer.pubkey, mynodeid], final_recipient_data)
result.append(blinded_path)