1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259
// Wallet-level libraries for bitcoin protocol by LNP/BP Association
//
// Written in 2020-2022 by
// Dr. Maxim Orlovsky <orlovsky@lnp-bp.org>
//
// This software is distributed without any warranty.
//
// You should have received a copy of the Apache-2.0 License
// along with this software.
// If not, see <https://opensource.org/licenses/Apache-2.0>.
//! Processing proprietary PSBT keys related to taproot-based OP_RETURN
//! (or tapret) commitments.
//!
//! NB: Wallets supporting tapret commitments must do that through the use of
//! deterministic bitcoin commitments crate (`bp-dpc`) in order to ensure
//! that multiple protocols can put commitment inside the same transaction
//! without collisions between them.
//!
//! This module provides support for marking PSBT outputs which may host
//! tapreturn commitment and populating PSBT with the data related to tapret
//! commitments.
use amplify::Slice32;
use bitcoin_scripts::taproot::DfsPath;
use confined_encoding::{ConfinedDecode, ConfinedEncode};
use crate::raw::ProprietaryKey;
use crate::Output;
/// PSBT proprietary key prefix used for tapreturn commitment.
pub const PSBT_TAPRET_PREFIX: &[u8] = b"TAPRET";
/// Proprietary key subtype for PSBT inputs containing the applied tapret tweak
/// information.
pub const PSBT_IN_TAPRET_TWEAK: u8 = 0x00;
/// Proprietary key subtype marking PSBT outputs which may host tapreturn
/// commitment.
pub const PSBT_OUT_TAPRET_HOST: u8 = 0x00;
/// Proprietary key subtype holding 32-byte commitment which will be put into
/// tapreturn tweak.
pub const PSBT_OUT_TAPRET_COMMITMENT: u8 = 0x01;
/// Proprietary key subtype holding merkle branch path to tapreturn tweak inside
/// the taptree structure.
pub const PSBT_OUT_TAPRET_PROOF: u8 = 0x02;
/// Extension trait for static functions returning tapreturn-related proprietary
/// keys.
pub trait ProprietaryKeyTapret {
/// Constructs [`PSBT_IN_TAPRET_TWEAK`] proprietary key.
fn tapret_tweak() -> ProprietaryKey {
ProprietaryKey {
prefix: PSBT_TAPRET_PREFIX.to_vec(),
subtype: PSBT_IN_TAPRET_TWEAK,
key: vec![],
}
}
/// Constructs [`PSBT_OUT_TAPRET_HOST`] proprietary key.
fn tapret_host() -> ProprietaryKey {
ProprietaryKey {
prefix: PSBT_TAPRET_PREFIX.to_vec(),
subtype: PSBT_OUT_TAPRET_HOST,
key: vec![],
}
}
/// Constructs [`PSBT_OUT_TAPRET_COMMITMENT`] proprietary key.
fn tapret_commitment() -> ProprietaryKey {
ProprietaryKey {
prefix: PSBT_TAPRET_PREFIX.to_vec(),
subtype: PSBT_OUT_TAPRET_COMMITMENT,
key: vec![],
}
}
/// Constructs [`PSBT_OUT_TAPRET_PROOF`] proprietary key.
fn tapret_proof() -> ProprietaryKey {
ProprietaryKey {
prefix: PSBT_TAPRET_PREFIX.to_vec(),
subtype: PSBT_OUT_TAPRET_PROOF,
key: vec![],
}
}
}
impl ProprietaryKeyTapret for ProprietaryKey {}
/// Errors processing tapret-related proprietary PSBT keys and their values.
#[derive(
Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash, Debug, Display, Error, From
)]
#[display(doc_comments)]
pub enum TapretKeyError {
/// output already contains commitment; there must be a single commitment
/// per output.
OutputAlreadyHasCommitment,
/// the output is not marked to host tapret commitments. Please first set
/// PSBT_OUT_TAPRET_HOST flag.
TapretProhibited,
/// The key contains invalid value
#[from(confined_encoding::Error)]
InvalidKeyValue,
}
/// Error decoding [`DfsPath`] inside PSBT data
#[derive(
Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash, Debug, Display, Error
)]
#[display("incorrect DFS path data inside PSBT proprietary key value")]
pub struct DfsPathEncodeError;
impl Output {
/// Returns whether this output may contain tapret commitment. This is
/// detected by the presence of [`PSBT_OUT_TAPRET_HOST`] key.
#[inline]
pub fn is_tapret_host(&self) -> bool {
self.proprietary
.contains_key(&ProprietaryKey::tapret_host())
}
/// Returns information on the specific path within taproot script tree
/// which is allowed as a place for tapret commitment. The path is taken
/// from [`PSBT_OUT_TAPRET_HOST`] key.
///
/// # Returns
///
/// A value of the [`PSBT_OUT_TAPRET_HOST`] key, if present, or `None`
/// otherwise. The value is deserialized from the key value data, and if
/// the serialization fails a `Some(Err(`[`DfsPathEncodeError`]`))` is
/// returned.
pub fn tapret_dfs_path(&self) -> Option<Result<DfsPath, DfsPathEncodeError>> {
self.proprietary
.get(&ProprietaryKey::tapret_host())
.map(|data| DfsPath::confined_deserialize(data).map_err(|_| DfsPathEncodeError))
}
/// Sets information on the specific path within taproot script tree which
/// is allowed as a place for tapret commitment. The path is put into
/// [`PSBT_OUT_TAPRET_HOST`] key.
///
/// # Errors
///
/// Errors with [`TapretKeyError::OutputAlreadyHasCommitment`] if the
/// commitment is already present in the output.
pub fn set_tapret_dfs_path(&mut self, path: &DfsPath) -> Result<(), TapretKeyError> {
if self.tapret_dfs_path().is_some() {
return Err(TapretKeyError::OutputAlreadyHasCommitment);
}
self.proprietary.insert(
ProprietaryKey::tapret_host(),
path.confined_serialize()
.expect("DFS paths are always compact and serializable"),
);
Ok(())
}
/// Detects presence of a valid [`PSBT_OUT_TAPRET_COMMITMENT`].
///
/// If [`PSBT_OUT_TAPRET_COMMITMENT`] is absent or its value is invalid,
/// returns `false`. In the future, when `PSBT_OUT_TAPRET_COMMITMENT` will
/// become a standard and non-custom key, PSBTs with invalid key values
/// will error at deserialization and this function will return `false`
/// only in cases when the output does not have
/// `PSBT_OUT_TAPRET_COMMITMENT`.
pub fn has_tapret_commitment(&self) -> bool {
self.proprietary
.contains_key(&ProprietaryKey::tapret_commitment())
}
/// Returns valid tapret commitment from the [`PSBT_OUT_TAPRET_COMMITMENT`]
/// key, if present. If the commitment is absent or invalid, returns
/// `None`.
///
/// We do not error on invalid commitments in order to support future update
/// of this proprietary key to the standard one. In this case, the
/// invalid commitments (having non-32 bytes) will be filtered at the
/// moment of PSBT deserialization and this function will return `None`
/// only in situations when the commitment is absent.
pub fn tapret_commitment(&self) -> Option<Slice32> {
self.proprietary
.get(&ProprietaryKey::tapret_commitment())
.and_then(Slice32::from_slice)
}
/// Assigns value of the tapreturn commitment to this PSBT output, by
/// adding [`PSBT_OUT_TAPRET_COMMITMENT`] and [`PSBT_OUT_TAPRET_PROOF`]
/// proprietary keys containing the 32-byte commitment as its proof.
///
/// # Errors
///
/// Errors with [`TapretKeyError::OutputAlreadyHasCommitment`] if the
/// commitment is already present in the output, and with
/// [`TapretKeyError::TapretProhibited`] if tapret commitments are not
/// enabled for this output.
pub fn set_tapret_commitment(
&mut self,
commitment: impl Into<[u8; 32]>,
proof: &impl ConfinedEncode,
) -> Result<(), TapretKeyError> {
if !self.is_tapret_host() {
return Err(TapretKeyError::TapretProhibited);
}
if self.has_tapret_commitment() {
return Err(TapretKeyError::OutputAlreadyHasCommitment);
}
self.proprietary.insert(
ProprietaryKey::tapret_commitment(),
commitment.into().to_vec(),
);
self.proprietary
.insert(ProprietaryKey::tapret_proof(), proof.confined_serialize()?);
Ok(())
}
/// Detects presence of a valid [`PSBT_OUT_TAPRET_PROOF`].
///
/// If [`PSBT_OUT_TAPRET_PROOF`] is absent or its value is invalid,
/// returns `false`. In the future, when `PSBT_OUT_TAPRET_PROOF` will
/// become a standard and non-custom key, PSBTs with invalid key values
/// will error at deserialization and this function will return `false`
/// only in cases when the output does not have `PSBT_OUT_TAPRET_PROOF`.
pub fn has_tapret_proof(&self) -> bool {
self.proprietary
.contains_key(&ProprietaryKey::tapret_proof())
}
/// Returns valid tapret commitment proof from the [`PSBT_OUT_TAPRET_PROOF`]
/// key, if present. If the commitment is absent or invalid, returns `None`.
///
/// We do not error on invalid proofs in order to support future update of
/// this proprietary key to the standard one. In this case, the invalid
/// commitments (having non-32 bytes) will be filtered at the moment of PSBT
/// deserialization and this function will return `None` only in situations
/// when the commitment is absent.
///
/// Function returns generic type since the real type will create dependency
/// on `bp-dpc` crate, which will result in circular dependency with the
/// current crate.
pub fn tapret_proof<T>(&self) -> Result<Option<T>, TapretKeyError>
where
T: ConfinedDecode,
{
self.proprietary
.get(&ProprietaryKey::tapret_proof())
.map(T::confined_deserialize)
.transpose()
.map_err(TapretKeyError::from)
}
}