FinalizePsbt

FinalizePsbt expects a partial transaction with all inputs and outputs fully declared and tries to sign all inputs that belong to the wallet. Lnd must be the last signer of the transaction. That means, if there are any unsigned non-witness inputs or inputs without UTXO information attached or inputs without witness data that do not belong to lnd's wallet, this method will fail. If no error is returned, the PSBT is ready to be extracted and the final TX within to be broadcast.

NOTE: This method does NOT publish the transaction once finalized. It is the caller's responsibility to either publish the transaction on success or unlock/release any locked UTXOs in case of an error in this method.

Source: walletrpc/walletkit.proto

gRPC

rpc FinalizePsbt (FinalizePsbtRequest) returns (FinalizePsbtResponse);

REST

HTTP Method	Path
POST	/v2/wallet/psbt/finalize

Code Samples

gRPC

Javascript

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

const GRPC_HOST = 'localhost:10009'
const MACAROON_PATH = 'LND_DIR/data/chain/bitcoin/regtest/admin.macaroon'
const TLS_PATH = 'LND_DIR/tls.cert'

const loaderOptions = {
  keepCase: true,
  longs: String,
  enums: String,
  defaults: true,
  oneofs: true,
};
const packageDefinition = protoLoader.loadSync(['lightning.proto', 'walletrpc/walletkit.proto'], loaderOptions);
const walletrpc = grpc.loadPackageDefinition(packageDefinition).walletrpc;
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 walletrpc.WalletKit(GRPC_HOST, creds);
let request = {
  funded_psbt: <bytes>,
  account: <string>,
};
client.finalizePsbt(request, function(err, response) {
  console.log(response);
});
// Console output:
//  {
//    "signed_psbt": <bytes>,
//    "raw_final_tx": <bytes>,
//  }

Python

import codecs, grpc, os
# Generate the following 2 modules by compiling the walletrpc/walletkit.proto with the grpcio-tools.
# See https://github.com/lightningnetwork/lnd/blob/master/docs/grpc/python.md for instructions.
import walletkit_pb2 as walletrpc, walletkit_pb2_grpc as walletkitstub

GRPC_HOST = 'localhost:10009'
MACAROON_PATH = 'LND_DIR/data/chain/bitcoin/regtest/admin.macaroon'
TLS_PATH = 'LND_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 = walletkitstub.WalletKitStub(channel)
request = walletrpc.FinalizePsbtRequest(
  funded_psbt=<bytes>,
  account=<string>,
)
response = stub.FinalizePsbt(request)
print(response)
# {
#    "signed_psbt": <bytes>,
#    "raw_final_tx": <bytes>,
# }

REST

Javascript

const fs = require('fs');
const request = require('request');

const REST_HOST = 'localhost:8080'
const MACAROON_PATH = 'LND_DIR/data/chain/bitcoin/regtest/admin.macaroon'

let requestBody = {
  funded_psbt: <string>, // <bytes> (base64 encoded)
  account: <string>, // <string> 
};
let options = {
  url: `https://${REST_HOST}/v2/wallet/psbt/finalize`,
  // Work-around for self-signed certificates.
  rejectUnauthorized: false,
  json: true,
  headers: {
    'Grpc-Metadata-macaroon': fs.readFileSync(MACAROON_PATH).toString('hex'),
  },
  form: JSON.stringify(requestBody),
}
request.post(options, function(error, response, body) {
  console.log(body);
});
// Console output:
//  {
//    "signed_psbt": <string>, // <bytes> 
//    "raw_final_tx": <string>, // <bytes> 
//  }

Python

import base64, codecs, json, requests

REST_HOST = 'localhost:8080'
MACAROON_PATH = 'LND_DIR/data/chain/bitcoin/regtest/admin.macaroon'
TLS_PATH = 'LND_DIR/tls.cert'

url = f'https://{REST_HOST}/v2/wallet/psbt/finalize'
macaroon = codecs.encode(open(MACAROON_PATH, 'rb').read(), 'hex')
headers = {'Grpc-Metadata-macaroon': macaroon}
data = {
  'funded_psbt': base64.b64encode(<bytes>),
  'account': <string>,
}
r = requests.post(url, headers=headers, data=json.dumps(data), verify=TLS_PATH)
print(r.json())
# {
#    "signed_psbt": <bytes>,
#    "raw_final_tx": <bytes>,
# }

Shell

$ lncli wallet psbt finalize --help

NAME:
   lncli wallet psbt finalize - Finalize a Partially Signed Bitcoin Transaction (PSBT).

USAGE:
   lncli wallet psbt finalize [command options] funded_psbt

DESCRIPTION:
   
  The finalize command expects a partial transaction with all inputs
  and outputs fully declared and tries to sign all inputs that belong to
  the wallet. Lnd must be the last signer of the transaction. That means,
  if there are any unsigned non-witness inputs or inputs without UTXO
  information attached or inputs without witness data that do not belong
  to lnd's wallet, this method will fail. If no error is returned, the
  PSBT is ready to be extracted and the final TX within to be broadcast.

  This method does NOT publish the transaction after it's been finalized
  successfully.
  

OPTIONS:
   --funded_psbt value  the base64 encoded PSBT to finalize
   --account value      (optional) the name of the account to finalize the PSBT with
   

Messages

walletrpc.FinalizePsbtRequest

Source: walletrpc/walletkit.proto

Field	gRPC Type	REST Type	REST Placement
funded_psbt A PSBT that should be signed and finalized. The PSBT must contain all required inputs, outputs, UTXO data and partial signatures of all other signers.	bytes	string	body
account The name of the account to finalize the PSBT with. If empty, the default wallet account is used.	string	string	body

walletrpc.FinalizePsbtResponse

Source: walletrpc/walletkit.proto

Field	gRPC Type	REST Type
signed_psbt The fully signed and finalized transaction in PSBT format.	bytes	string
raw_final_tx The fully signed and finalized transaction in the raw wire format.	bytes	string