PushPreimage

PushPreimage is called by the client to push the preimage to the server. This returns the musig2 signatures that the client needs to sweep the htlc.

Source: swapserverrpc/instantout.proto

gRPC

rpc PushPreimage (PushPreimageRequest) returns (PushPreimageResponse);

Code Samples

gRPC

Javascript

const fs = require('fs');
const grpc = require('@grpc/grpc-js');
const protoLoader = require('@grpc/proto-loader');

const GRPC_HOST = 'localhost:11010'
const MACAROON_PATH = 'LOOP_DIR/regtest/loop.macaroon'
const TLS_PATH = 'LOOP_DIR/tls.cert'

const loaderOptions = {
  keepCase: true,
  longs: String,
  enums: String,
  defaults: true,
  oneofs: true,
};
const packageDefinition = protoLoader.loadSync('swapserverrpc/instantout.proto', loaderOptions);
const looprpc = grpc.loadPackageDefinition(packageDefinition).looprpc;
process.env.GRPC_SSL_CIPHER_SUITES = 'HIGH+ECDSA';
const tlsCert = fs.readFileSync(TLS_PATH);
const sslCreds = grpc.credentials.createSsl(tlsCert);
const macaroon = fs.readFileSync(MACAROON_PATH).toString('hex');
const macaroonCreds = grpc.credentials.createFromMetadataGenerator(function(args, callback) {
  let metadata = new grpc.Metadata();
  metadata.add('macaroon', macaroon);
  callback(null, metadata);
});
let creds = grpc.credentials.combineChannelCredentials(sslCreds, macaroonCreds);
let client = new looprpc.InstantSwapServer(GRPC_HOST, creds);
let request = {
  preimage: <bytes>,
  client_nonces: <bytes>,
  client_sweep_addr: <string>,
  musig_tx_fee_rate: <uint64>,
};
client.pushPreimage(request, function(err, response) {
  console.log(response);
});
// Console output:
//  {
//    "musig2_sweep_sigs": <bytes>,
//    "server_nonces": <bytes>,
//  }

Python

import codecs, grpc, os
# Generate the following 2 modules by compiling the swapserverrpc/instantout.proto with the grpcio-tools.
# See https://github.com/lightningnetwork/lnd/blob/master/docs/grpc/python.md for instructions.
import instantout_pb2 as looprpc, instantout_pb2_grpc as instantoutstub

GRPC_HOST = 'localhost:11010'
MACAROON_PATH = 'LOOP_DIR/regtest/loop.macaroon'
TLS_PATH = 'LOOP_DIR/tls.cert'

# create macaroon credentials
macaroon = codecs.encode(open(MACAROON_PATH, 'rb').read(), 'hex')
def metadata_callback(context, callback):
  callback([('macaroon', macaroon)], None)
auth_creds = grpc.metadata_call_credentials(metadata_callback)
# create SSL credentials
os.environ['GRPC_SSL_CIPHER_SUITES'] = 'HIGH+ECDSA'
cert = open(TLS_PATH, 'rb').read()
ssl_creds = grpc.ssl_channel_credentials(cert)
# combine macaroon and SSL credentials
combined_creds = grpc.composite_channel_credentials(ssl_creds, auth_creds)
# make the request
channel = grpc.secure_channel(GRPC_HOST, combined_creds)
stub = instantoutstub.InstantSwapServerStub(channel)
request = looprpc.PushPreimageRequest(
  preimage=<bytes>,
  client_nonces=<bytes>,
  client_sweep_addr=<string>,
  musig_tx_fee_rate=<uint64>,
)
response = stub.PushPreimage(request)
print(response)
# {
#    "musig2_sweep_sigs": <bytes>,
#    "server_nonces": <bytes>,
# }

Shell

# There is no CLI command for this RPC

Messages

looprpc.PushPreimageRequest

Source: swapserverrpc/instantout.proto

Field	gRPC Type	REST Type	REST Placement
preimage The preimage that the client generated for the swap.	bytes	unknown	unknown
client_nonces The nonces that the client used to generate the sweepless sweep sigs.	bytes[]	unknown	unknown
client_sweep_addr The address that the client wants to sweep the htlc to.	string	unknown	unknown
musig_tx_fee_rate The fee rate in sat/kw that the client wants to use for the sweep.	uint64	unknown	unknown

looprpc.PushPreimageResponse

Source: swapserverrpc/instantout.proto

Field	gRPC Type	REST Type
musig2_sweep_sigs The sweep sigs that the server generated for the htlc.	bytes[]	unknown
server_nonces The nonces that the server used to generate the sweepless sweep sigs.	bytes[]	unknown