Fake a channel backup file to attempt fund recovery
If for any reason a node suffers from data loss and there is no channel.backup for one or more channels, then the funds in the channel would theoretically be lost forever. If the remote node is still online and still knows about the channel, there is hope. We can initiate DLP (Data Loss Protocol) and ask the remote node to force-close the channel and to provide us with the per_commit_point that is needed to derive the private key for our part of the force-close transaction output. But to initiate DLP, we would need to have a channel.backup file. Fortunately, if we have enough information about the channel, we can create a faked/skeleton channel.backup file that at least lets us talk to the other node and ask them to do their part. Then we can later brute-force the private key for the transaction output of our part of the funds (see rescueclosed command).
There are two versions of this command: The first one is to create a fake backup for a single channel where all flags (except --from_channel_graph) need to be set. This is the easiest to use since it only relies on data that is publicly available (for example on 1ml.com) but involves more manual work. The second version of the command only takes the --from_channel_graph and --multi_file flags and tries to assemble all channels found in the public network graph (must be provided in the JSON format that the 'lncli describegraph' command returns) into a fake backup file. This is the most convenient way to use this command but requires one to have a fully synced lnd node.
Any fake channel backup needs to be used with the custom fork of lnd specifically built for this purpose: https://github.com/guggero/lnd/releases Also the debuglevel must be set to debug (lnd.conf, set 'debuglevel=debug') when running the above lnd for it to produce the correct log file that will be needed for the rescueclosed command.
chantools fakechanbackup [flags]
chantools fakechanbackup \ --capacity 123456 \ --channelpoint f39310xxxxxxxxxx:1 \ --remote_node_addr firstname.lastname@example.org:9735 \ --short_channel_id 566222x300x1 \ --multi_file fake.backup chantools fakechanbackup --from_channel_graph lncli_describegraph.json \ --multi_file fake.backup
--bip39 read a classic BIP39 seed and passphrase from the terminal instead of asking for lnd seed format or providing the --rootkey flag --capacity uint the channel's capacity in satoshis --channelpoint string funding transaction outpoint of the channel to rescue (<txid>:<txindex>) as it is displayed on 1ml.com --from_channel_graph string the full LN channel graph in the JSON format that the 'lncli describegraph' returns -h, --help help for fakechanbackup --multi_file string the fake channel backup file to create (default "results/fake-2021-11-11-13-31-59.backup") --remote_node_addr string the remote node connection information in the format pubkey@host:port --rootkey string BIP32 HD root key of the wallet to use for encrypting the backup; leave empty to prompt for lnd 24 word aezeed --short_channel_id string the short channel ID in the format <blockheight>x<transactionindex>x<outputindex>
-r, --regtest Indicates if regtest parameters should be used -t, --testnet Indicates if testnet parameters should be used