rust-bitcoin-unsafe-fast/examples/ecdsa-psbt.rs

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//! Implements an example PSBT workflow.
//!
//! The workflow we simulate is that of a setup using a watch-only online wallet (contains only
//! public keys) and a cold-storage signing wallet (contains the private keys).
//!
//! You can verify the workflow using `bitcoind` and `bitcoin-cli`.
//!
//! ## Example Setup
//!
//! 1. Start Bitcoin Core in Regtest mode, for example:
//!
//! `bitcoind -regtest -server -daemon -fallbackfee=0.0002 -rpcuser=admin -rpcpassword=pass -rpcallowip=127.0.0.1/0 -rpcbind=127.0.0.1 -blockfilterindex=1 -peerblockfilters=1`
//!
//! 2. Define a shell alias to `bitcoin-cli`, for example:
//!
//! `alias bt=bitcoin-cli -rpcuser=admin -rpcpassword=pass -rpcport=18443`
//!
//! 3. Create (or load) a default wallet, for example:
//!
//! `bt createwallet <wallet-name>`
//!
//! 4. Mine some blocks, for example:
//!
//! `bt generatetoaddress 110 $(bt getnewaddress)`
//!
//! 5. Get the details for a UTXO to fund the PSBT with:
//!
//! `bt listunspent`
//!
use std::fmt;
use std::str::FromStr;
use std::collections::BTreeMap;
use bitcoin::{Address, Amount, Network, OutPoint, PublicKey, PrivateKey, Sequence, Script, Transaction, Txid, TxOut, TxIn, Witness};
use bitcoin::consensus::encode;
use bitcoin::hashes::hex::{self, FromHex};
use bitcoin::secp256k1::{Secp256k1, Signing, Verification};
use bitcoin::util::address;
use bitcoin::util::amount::ParseAmountError;
use bitcoin::util::bip32::{self, ChildNumber, DerivationPath, ExtendedPrivKey, ExtendedPubKey, Fingerprint, IntoDerivationPath};
use bitcoin::util::psbt::{self, Input, Psbt, PsbtSighashType};
use self::psbt_sign::*;
type Result<T> = std::result::Result<T, Error>;
// Get this from the output of `bt dumpwallet <file>`.
const EXTENDED_MASTER_PRIVATE_KEY: &str = "tprv8ZgxMBicQKsPeSHZFZWT8zxie2dXWcwemnTkf4grVzMvP2UABUxqbPTCHzZ4ztwhBghpfFw27sJqEgW6y1ZTZcfvCUdtXE1L6qMF7TBdbqQ";
// Set these with valid data from output of step 5 above. Please note, input utxo must be a p2wpkh.
const INPUT_UTXO_TXID: &str = "295f06639cde6039bf0c3dbf4827f0e3f2b2c2b476408e2f9af731a8d7a9c7fb";
const INPUT_UTXO_VOUT: u32 = 0;
const INPUT_UTXO_SCRIPT_PUBKEY: &str = "00149891eeb8891b3e80a2a1ade180f143add23bf5de";
const INPUT_UTXO_VALUE: &str = "50 BTC";
// Get this from the desciptor,
// "wpkh([97f17dca/0'/0'/0']02749483607dafb30c66bd93ece4474be65745ce538c2d70e8e246f17e7a4e0c0c)#m9n56cx0".
const INPUT_UTXO_DERIVATION_PATH: &str = "m/0h/0h/0h";
// Grab an address to receive on: `bt generatenewaddress` (obviously contrived but works as an example).
const RECEIVE_ADDRESS: &str = "bcrt1qcmnpjjjw78yhyjrxtql6lk7pzpujs3h244p7ae"; // The address to receive the coins we send.
// These should be correct if the UTXO above should is for 50 BTC.
const OUTPUT_AMOUNT_BTC: &str = "1 BTC";
const CHANGE_AMOUNT_BTC: &str = "48.99999 BTC"; // 1000 sat transaction fee.
const NETWORK: Network = Network::Regtest;
fn main() -> Result<()> {
let secp = Secp256k1::new();
let (offline, fingerprint, account_0_xpub, input_xpub) = ColdStorage::new(&secp, EXTENDED_MASTER_PRIVATE_KEY)?;
let online = WatchOnly::new(account_0_xpub, input_xpub, fingerprint);
let created = online.create_psbt(&secp)?;
let updated = online.update_psbt(created)?;
let signed = offline.sign_psbt(&secp, updated)?;
let finalized = online.finalize_psbt(signed)?;
// You can use `bt sendrawtransaction` to broadcast the extracted transaction.
let tx = finalized.extract_tx();
tx.verify(|_| Some(previous_output())).expect("failed to verify transaction");
let hex = encode::serialize_hex(&tx);
println!("You should now be able to broadcast the following transaction: \n\n{}", hex);
Ok(())
}
// We cache the pubkeys for convenience because it requires a scep context to convert the private key.
/// An example of an offline signer i.e., a cold-storage device.
struct ColdStorage {
/// The master extended private key.
master_xpriv: ExtendedPrivKey,
/// The master extended public key.
master_xpub: ExtendedPubKey,
}
/// The data exported from an offline wallet to enable creation of a watch-only online wallet.
/// (wallet, fingerprint, account_0_xpub, input_utxo_xpub)
type ExportData = (ColdStorage, Fingerprint, ExtendedPubKey, ExtendedPubKey);
impl ColdStorage {
/// Constructs a new `ColdStorage` signer.
///
/// # Returns
///
/// The newly created signer along with the data needed to configure a watch-only wallet.
fn new<C: Signing>(secp: &Secp256k1<C>, xpriv: &str)-> Result<ExportData> {
let master_xpriv = ExtendedPrivKey::from_str(xpriv)?;
let master_xpub = ExtendedPubKey::from_priv(secp, &master_xpriv);
// Hardened children require secret data to derive.
let path = "m/84h/0h/0h".into_derivation_path()?;
let account_0_xpriv = master_xpriv.derive_priv(secp, &path)?;
let account_0_xpub = ExtendedPubKey::from_priv(secp, &account_0_xpriv);
let path = INPUT_UTXO_DERIVATION_PATH.into_derivation_path()?;
let input_xpriv = master_xpriv.derive_priv(secp, &path)?;
let input_xpub = ExtendedPubKey::from_priv(secp, &input_xpriv);
let wallet = ColdStorage {
master_xpriv,
master_xpub,
};
let fingerprint = wallet.master_fingerprint();
Ok((wallet, fingerprint, account_0_xpub, input_xpub))
}
/// Returns the fingerprint for the master extended public key.
fn master_fingerprint(&self) -> Fingerprint {
self.master_xpub.fingerprint()
}
/// Signs `psbt` with this signer.
fn sign_psbt<C: Signing>(&self, secp: &Secp256k1<C>, mut psbt: Psbt) -> Result<Psbt> {
let sk = self.private_key_to_sign(secp, &psbt.inputs[0])?;
psbt_sign::sign(&mut psbt, &sk, 0, secp)?;
Ok(psbt)
}
/// Returns the private key required to sign `input` if we have it.
fn private_key_to_sign<C: Signing>(&self, secp: &Secp256k1<C>, input: &Input) -> Result<PrivateKey> {
match input.bip32_derivation.iter().next() {
Some((pk, (fingerprint, path))) => {
if *fingerprint != self.master_fingerprint() {
return Err(Error::WrongFingerprint);
}
let sk = self.master_xpriv.derive_priv(secp, &path)?.to_priv();
if *pk != sk.public_key(secp).inner {
return Err(Error::WrongPubkey);
}
Ok(sk)
},
None => Err(Error::MissingBip32Derivation),
}
}
}
/// An example of an watch-only online wallet.
struct WatchOnly {
/// The xpub for account 0 derived from derivation path "m/84h/0h/0h".
account_0_xpub: ExtendedPubKey,
/// The xpub derived from `INPUT_UTXO_DERIVATION_PATH`.
input_xpub: ExtendedPubKey,
/// The master extended pubkey fingerprint.
master_fingerprint: Fingerprint,
}
impl WatchOnly {
/// Constructs a new watch-only wallet.
///
/// A watch-only wallet would typically be online and connected to the Bitcoin network. We
/// 'import' into the wallet the `account_0_xpub` and `master_fingerprint`.
///
/// The reason for importing the `input_xpub` is so one can use bitcoind to grab a valid input
/// to verify the workflow presented in this file.
fn new(account_0_xpub: ExtendedPubKey, input_xpub: ExtendedPubKey, master_fingerprint: Fingerprint) -> Self {
WatchOnly { account_0_xpub, input_xpub, master_fingerprint }
}
/// Creates the PSBT, in BIP174 parlance this is the 'Creater'.
fn create_psbt<C: Verification>(&self, secp: &Secp256k1<C>) -> Result<Psbt> {
let to_address = Address::from_str(RECEIVE_ADDRESS)?;
let to_amount = Amount::from_str(OUTPUT_AMOUNT_BTC)?;
let (_, change_address, _) = self.change_address(secp)?;
let change_amount = Amount::from_str(CHANGE_AMOUNT_BTC)?;
let tx = Transaction {
version: 2,
lock_time: 0,
input: vec![
TxIn {
previous_output: OutPoint {
txid: Txid::from_hex(INPUT_UTXO_TXID)?,
vout: INPUT_UTXO_VOUT,
},
script_sig: Script::new(),
sequence: Sequence::MAX, // Disable LockTime and RBF.
witness: Witness::default(),
},
],
output: vec![
TxOut {
value: to_amount.to_sat(),
script_pubkey: to_address.script_pubkey(),
},
TxOut {
value: change_amount.to_sat(),
script_pubkey: change_address.script_pubkey(),
}
],
};
let psbt = Psbt::from_unsigned_tx(tx)?;
Ok(psbt)
}
/// Updates the PSBT, in BIP174 parlance this is the 'Updater'.
fn update_psbt(&self, mut psbt: Psbt) -> Result<Psbt> {
let mut input = Input { witness_utxo: Some(previous_output()), ..Default::default() };
let pk = self.input_xpub.to_pub();
let wpkh = pk.wpubkey_hash().expect("a compressed pubkey");
let redeem_script = Script::new_v0_p2wpkh(&wpkh);
input.redeem_script = Some(redeem_script);
let fingerprint = self.master_fingerprint;
let path = input_derivation_path()?;
let mut map = BTreeMap::new();
map.insert(pk.inner, (fingerprint, path));
input.bip32_derivation = map;
let ty = PsbtSighashType::from_str("SIGHASH_ALL").map_err(|_| Error::SighashTypeParse)?;
input.sighash_type = Some(ty);
psbt.inputs = vec![input];
Ok(psbt)
}
/// Finalizes the PSBT, in BIP174 parlance this is the 'Finalizer'.
fn finalize_psbt(&self, mut psbt: Psbt) -> Result<Psbt> {
use bitcoin::util::psbt::serialize::Serialize;
if psbt.inputs.is_empty() {
return Err(Error::InputsEmpty);
}
let sigs: Vec<_> = psbt.inputs[0].partial_sigs.values().collect();
let mut script_witness: Witness = Witness::new();
script_witness.push(&sigs[0].serialize());
script_witness.push(self.input_xpub.to_pub().serialize());
psbt.inputs[0].final_script_witness = Some(script_witness);
// Clear all the data fields as per the spec.
psbt.inputs[0].partial_sigs = BTreeMap::new();
psbt.inputs[0].sighash_type = None;
psbt.inputs[0].redeem_script = None;
psbt.inputs[0].witness_script = None;
psbt.inputs[0].bip32_derivation = BTreeMap::new();
Ok(psbt)
}
/// Returns data for the first change address (standard BIP84 derivation path
/// "m/84h/0h/0h/1/0"). A real wallet would have access to the chain so could determine if an
/// address has been used or not. We ignore this detail and just re-use the first change address
/// without loss of generality.
fn change_address<C: Verification>(&self, secp: &Secp256k1<C>) -> Result<(PublicKey, Address, DerivationPath)> {
let path = vec![ChildNumber::from_normal_idx(1)?, ChildNumber::from_normal_idx(0)?];
let derived = self.account_0_xpub.derive_pub(secp, &path)?;
let pk = derived.to_pub();
let addr = Address::p2wpkh(&pk, NETWORK)?;
let path = path.into_derivation_path()?;
Ok((pk, addr, path))
}
}
fn input_derivation_path() -> Result<DerivationPath> {
let path = INPUT_UTXO_DERIVATION_PATH.into_derivation_path()?;
Ok(path)
}
fn previous_output() -> TxOut {
let script_pubkey = Script::from_hex(INPUT_UTXO_SCRIPT_PUBKEY).expect("failed to parse input utxo scriptPubkey");
let amount = Amount::from_str(INPUT_UTXO_VALUE).expect("failed to parse input utxo value");
TxOut {
value: amount.to_sat(),
script_pubkey,
}
}
#[derive(Clone, Debug, PartialEq, Eq)]
enum Error {
/// Bip32 error.
Bip32(bip32::Error),
/// PSBT error.
Psbt(psbt::Error),
/// PSBT sighash error.
PsbtSighash(SighashError),
/// Bitcoin_hashes hex error.
Hex(hex::Error),
/// Address error.
Address(address::Error),
/// Parse amount error.
ParseAmount(ParseAmountError),
/// Parsing sighash type string failed.
SighashTypeParse,
/// PSBT inputs field is empty.
InputsEmpty,
/// BIP32 data missing.
MissingBip32Derivation,
/// Fingerprint does not match that in input.
WrongFingerprint,
/// Pubkey for derivation path does not match that in input.
WrongPubkey,
}
impl std::error::Error for Error {
fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
None
}
}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{:?}", self)
}
}
impl From<bip32::Error> for Error {
fn from(e: bip32::Error) -> Error {
Error::Bip32(e)
}
}
impl From<psbt::Error> for Error {
fn from(e: psbt::Error) -> Error {
Error::Psbt(e)
}
}
impl From<SighashError> for Error {
fn from(e: SighashError) -> Error {
Error::PsbtSighash(e)
}
}
impl From<hex::Error> for Error {
fn from(e: hex::Error) -> Error {
Error::Hex(e)
}
}
impl From<address::Error> for Error {
fn from(e: address::Error) -> Error {
Error::Address(e)
}
}
impl From<ParseAmountError> for Error {
fn from(e: ParseAmountError) -> Error {
Error::ParseAmount(e)
}
}
/// This module implements signing a PSBT. It is based on code in `rust-miniscript` with a bit of a
/// look at `bdk` as well. Since this example only uses ECDSA signatures the signing code is
/// sufficient however before we can merge this into the main `rust-bitcoin` crate we need to handle
/// taproot as well. See PR: https://github.com/rust-bitcoin/rust-bitcoin/pull/957
///
/// All functions that take a `psbt` argument should be implemented on `Psbt` and use `self` instead.
mod psbt_sign {
use std::fmt;
use std::ops::Deref;
use bitcoin::{EcdsaSig, EcdsaSighashType, EcdsaSigError, PrivateKey, SchnorrSighashType, Script, Transaction, TxOut};
use bitcoin::psbt::{Input, Prevouts, Psbt, PsbtSighashType};
use bitcoin::util::sighash::{self, SighashCache};
use bitcoin::util::taproot::TapLeafHash;
use secp256k1::{Message, Signing, Secp256k1};
/// Signs the input at `input_index` with private key `sk`.
pub fn sign<C: Signing>(psbt: &mut Psbt, sk: &PrivateKey, input_index: usize, secp: &Secp256k1<C>) -> Result<(), SighashError> {
check_index_is_within_bounds(psbt, input_index)?;
let mut cache = SighashCache::new(&psbt.unsigned_tx);
let (msg, sighash_ty) = sighash(psbt, input_index, &mut cache, None)?;
let sig = secp.sign_ecdsa(&msg, &sk.inner);
let mut final_signature = Vec::with_capacity(75);
final_signature.extend_from_slice(&sig.serialize_der());
final_signature.push(sighash_ty.to_u32() as u8);
let pk = sk.public_key(secp);
psbt.inputs[input_index]
.partial_sigs
.insert(pk, EcdsaSig::from_slice(&final_signature)?);
Ok(())
}
/// Returns the sighash message to sign along with the sighash type.
fn sighash<T: Deref<Target=Transaction>>(
psbt: &Psbt,
input_index: usize,
cache: &mut SighashCache<T>,
tapleaf_hash: Option<TapLeafHash>,
) -> Result<(Message, PsbtSighashType), SighashError> {
check_index_is_within_bounds(psbt, input_index)?;
let input = &psbt.inputs[input_index];
let prevouts = prevouts(psbt)?;
let utxo = spend_utxo(psbt, input_index)?;
let script = utxo.script_pubkey.clone(); // scriptPubkey for input spend utxo.
if script.is_v1_p2tr() {
return taproot_sighash(input, prevouts, input_index, cache, tapleaf_hash);
}
let hash_ty = input
.sighash_type
.map(|ty| ty.ecdsa_hash_ty())
.unwrap_or(Ok(EcdsaSighashType::All))
.map_err(|_| SighashError::InvalidSighashType)?; // Only support standard sighash types.
let is_wpkh = script.is_v0_p2wpkh();
let is_wsh = script.is_v0_p2wsh();
let is_nested_wpkh = script.is_p2sh()
&& input.redeem_script.as_ref()
.map(|s| s.is_v0_p2wpkh()).unwrap_or(false);
let is_nested_wsh = script.is_p2sh()
&& input.redeem_script.as_ref()
.map(|x| x.is_v0_p2wsh()).unwrap_or(false);
let is_segwit = is_wpkh || is_wsh || is_nested_wpkh || is_nested_wsh;
let sighash = if is_segwit {
if is_wpkh || is_nested_wpkh {
let script_code = if is_wpkh {
Script::p2wpkh_script_code(&script).ok_or(SighashError::NotWpkh)?
} else {
Script::p2wpkh_script_code(input.redeem_script.as_ref().expect("checked above"))
.ok_or(SighashError::NotWpkh)?
};
cache.segwit_signature_hash(input_index, &script_code, utxo.value, hash_ty)?
} else {
let script_code = input.witness_script.as_ref().ok_or(SighashError::MissingWitnessScript)?;
cache.segwit_signature_hash(input_index, script_code, utxo.value, hash_ty)?
}
} else {
let script_code = if script.is_p2sh() {
input.redeem_script.as_ref().ok_or(SighashError::MissingRedeemScript)?
} else {
&script
};
cache.legacy_signature_hash(input_index, script_code, hash_ty.to_u32())?
};
Ok((Message::from_slice(&sighash).expect("sighashes are 32 bytes"), hash_ty.into()))
}
/// Returns the prevouts for this PSBT.
fn prevouts(psbt: &Psbt) -> Result<Vec<&TxOut>, SighashError> {
let len = psbt.inputs.len();
let mut utxos = Vec::with_capacity(len);
for i in 0..len {
utxos.push(spend_utxo(psbt, i)?);
}
Ok(utxos)
}
/// Returns the spending utxo for this PSBT's input at `input_index`.
fn spend_utxo(psbt: &Psbt, input_index: usize) -> Result<&TxOut, SighashError> {
check_index_is_within_bounds(psbt, input_index)?;
let input = &psbt.inputs[input_index];
let utxo = if let Some(witness_utxo) = &input.witness_utxo {
witness_utxo
} else if let Some(non_witness_utxo) = &input.non_witness_utxo {
let vout = psbt.unsigned_tx.input[input_index].previous_output.vout;
&non_witness_utxo.output[vout as usize]
} else {
return Err(SighashError::MissingSpendUtxo);
};
Ok(utxo)
}
/// Checks `input_index` is within bounds for the PSBT `inputs` array and
/// for the PSBT `unsigned_tx` `input` array.
fn check_index_is_within_bounds(psbt: &Psbt, input_index: usize) -> Result<(), SighashError> {
if input_index >= psbt.inputs.len() {
return Err(SighashError::IndexOutOfBounds(input_index, psbt.inputs.len()));
}
if input_index >= psbt.unsigned_tx.input.len() {
return Err(SighashError::IndexOutOfBounds(input_index, psbt.unsigned_tx.input.len()));
}
Ok(())
}
/// Returns the sighash message and sighash type for this `input`.
fn taproot_sighash<T: Deref<Target=Transaction>>(
input: &Input,
prevouts: Vec<&TxOut>,
input_index: usize,
cache: &mut SighashCache<T>,
tapleaf_hash: Option<TapLeafHash>,
) -> Result<(Message, PsbtSighashType), SighashError> {
// Note that as per PSBT spec we should have access to spent utxos for the transaction. Even
// if the transaction does not require SIGHASH_ALL, we create `Prevouts::All` for simplicity.
let prevouts = Prevouts::All(&prevouts);
let hash_ty = input
.sighash_type
.map(|ty| ty.schnorr_hash_ty())
.unwrap_or(Ok(SchnorrSighashType::Default))
.map_err(|_e| SighashError::InvalidSighashType)?;
let sighash = match tapleaf_hash {
Some(leaf_hash) => {
cache.taproot_script_spend_signature_hash(input_index, &prevouts, leaf_hash, hash_ty)?
}
None => {
cache.taproot_key_spend_signature_hash(input_index, &prevouts, hash_ty)?
}
};
let msg = Message::from_slice(&sighash).expect("sighashes are 32 bytes");
Ok((msg, hash_ty.into()))
}
/// Errors encountered while calculating the sighash message.
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone)]
pub enum SighashError {
/// Input index out of bounds (actual index, maximum index allowed).
IndexOutOfBounds(usize, usize),
/// Missing spending utxo.
MissingSpendUtxo,
/// Missing witness script.
MissingWitnessScript,
/// Missing Redeem script.
MissingRedeemScript,
/// Invalid Sighash type.
InvalidSighashType,
/// The `scriptPubkey` is not a P2WPKH script.
NotWpkh,
/// Sighash computation error.
SighashComputation(sighash::Error),
/// An ECDSA key-related error occurred.
EcdsaSig(EcdsaSigError),
}
impl fmt::Display for SighashError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
SighashError::IndexOutOfBounds(ind, len) => {
write!(f, "index {}, psbt input len: {}", ind, len)
}
SighashError::MissingSpendUtxo => write!(f, "missing spend utxon in PSBT"),
SighashError::MissingWitnessScript => write!(f, "missing witness script"),
SighashError::MissingRedeemScript => write!(f, "missing redeem script"),
SighashError::InvalidSighashType => write!(f, "invalid sighash type"),
SighashError::NotWpkh => write!(f, "the scriptPubkey is not a P2WPKH script"),
// If merged into rust-bitcoin these two should use `write_err!`.
SighashError::SighashComputation(e) => write!(f, "sighash: {}", e),
SighashError::EcdsaSig(e) => write!(f, "ecdsa: {}", e),
}
}
}
impl From<sighash::Error> for SighashError {
fn from(e: sighash::Error) -> Self {
SighashError::SighashComputation(e)
}
}
impl From<EcdsaSigError> for SighashError {
fn from(e: EcdsaSigError) -> Self {
SighashError::EcdsaSig(e)
}
}
#[cfg(feature = "std")]
impl std::error::Error for SighashError {
fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
use self::SighashError::*;
match self {
IndexOutOfBounds(_, _)
| MissingSpendUtxo
| MissingWitnessScript
| MissingRedeemScript
| InvalidSighashType
| NotWpkh => None,
SighashComputation(e) => Some(e),
EcdsaSig(e) => Some(e),
}
}
}
}