bitcoin_scripts/

convert.rs

// BP foundation libraries Bitcoin crates implementing the foundations of
// Bitcoin protocol by LNP/BP Association (https://lnp-bp.org)
//
// 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>.

//! Helper traits and supplementary types for converting different types of
//! bitcoin_scripts and keys into each other.

use amplify::Wrapper;
use bitcoin::blockdata::script;
use bitcoin::blockdata::witness::Witness;
use bitcoin::{secp256k1, Script};
#[cfg(feature = "miniscript")]
use miniscript::descriptor::DescriptorType;
#[cfg(feature = "miniscript")]
use miniscript::{Descriptor, MiniscriptKey, ToPublicKey};

use crate::{LockScript, PubkeyScript, RedeemScript, ScriptSet, SigScript, WitnessScript};

/// Descriptor category specifies way how the `scriptPubkey` is structured
#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Debug, Display, Hash)]
#[repr(u8)]
pub enum ConvertInfo {
    /// Bare descriptors: `pk` and bare bitcoin_scripts, including `OP_RETURN`s.
    ///
    /// The script or public key gets right into `scriptPubkey`, i.e. as
    /// **P2PK** (for a public key) or as custom script (mostly used for
    /// `OP_RETURN`)
    #[display("bare")]
    Bare,

    /// Hash-based descriptors: `pkh` for public key hashes and BIP-16 `sh` for
    /// **P2SH** bitcoin_scripts.
    ///
    /// We hash public key or script and use non-SegWit `scriptPubkey`
    /// encoding, i.e. **P2PKH** or **P2SH** with corresponding non-segwit
    /// transaction input `scriptSig` containing copy of [`crate::LockScript`]
    /// in `redeemScript` field
    #[display("hashed")]
    Hashed,

    /// SegWit descriptors for legacy wallets defined in BIP 141 as P2SH nested
    /// types <https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki#P2WPKH_nested_in_BIP16_P2SH>:
    /// `sh(wpkh)` and `sh(wsh)`
    ///
    /// Compatibility variant for SegWit outputs when the SegWit version and
    /// program are encoded as [`crate::RedeemScript`] in `scriptSig`
    /// transaction input field, while the original public key or
    /// [`crate::WitnessScript`] are stored in `witness`. `scriptPubkey`
    /// contains a normal **P2SH** composed agains the `redeemScript` from
    /// `scriptSig` (**P2SH-P2WPKH** and **P2SH-P2WSH** variants).
    ///
    /// This type works with only with witness version v0, i.e. not applicable
    /// for Taproot.
    #[display("nested")]
    NestedV0,

    /// Native SegWit descriptors: `wpkh` for public keys and `wsh` for
    /// bitcoin_scripts
    ///
    /// We produce either **P2WPKH** or **P2WSH** output and use witness field
    /// in transaction input to store the original [`crate::LockScript`] or the
    /// public key
    #[display("segwit")]
    SegWitV0,

    /// Native Taproot descriptors: `taproot`
    #[display("taproot")]
    Taproot,
}

#[cfg(feature = "miniscript")]
impl<Pk> From<&Descriptor<Pk>> for ConvertInfo
where
    Pk: MiniscriptKey + ToPublicKey,
{
    fn from(descriptor: &Descriptor<Pk>) -> Self {
        match (descriptor.desc_type(), descriptor) {
            (DescriptorType::Bare, _) => ConvertInfo::Bare,
            (DescriptorType::Sh, _)
            | (DescriptorType::ShSortedMulti, _)
            | (DescriptorType::Pkh, _) => ConvertInfo::Hashed,
            (DescriptorType::Wpkh, _)
            | (DescriptorType::WshSortedMulti, _)
            | (DescriptorType::Wsh, _) => ConvertInfo::SegWitV0,
            (DescriptorType::ShWsh, _)
            | (DescriptorType::ShWpkh, _)
            | (DescriptorType::ShWshSortedMulti, _) => ConvertInfo::NestedV0,
            (_, Descriptor::Tr(_)) => ConvertInfo::Taproot,
            _ => unreachable!("taproot descriptor type for non-taproot descriptor"),
        }
    }
}

#[cfg(feature = "miniscript")]
impl<Pk> From<Descriptor<Pk>> for ConvertInfo
where
    Pk: MiniscriptKey + ToPublicKey,
{
    #[inline]
    fn from(descriptor: Descriptor<Pk>) -> Self { Self::from(&descriptor) }
}

impl ConvertInfo {
    /// Detects whether conversion is a non-nested segwit
    #[inline]
    pub fn is_segwit(self) -> bool { !matches!(self, ConvertInfo::Bare | ConvertInfo::Hashed) }

    /// Detects whether conversion is a taproot conversion
    #[inline]
    pub fn is_taproot(self) -> bool { !matches!(self, ConvertInfo::Taproot { .. }) }
}

/// Errors converting to [`LockScript`] type returned by
/// [`ToLockScript::to_lock_script`].
#[derive(
    Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash, Debug, Display, Error
)]
#[display(doc_comments)]
pub enum LockScriptError {
    /// attempt to generate segwit script with uncompressed pubkey {0}
    UncompressedPubkeyInWitness(bitcoin::PublicKey),

    /// taproot does not have a lock-script representation
    Taproot,
}

/// Conversion to [`LockScript`], which later may be used for creating different
/// end-point bitcoin_scripts, like [`PubkeyScript`], [`SigScript`], [`Witness`]
/// etc.
pub trait ToLockScript {
    /// Converts data type to [`LockScript`]. Errors on uncompressed public keys
    /// in segwit context and use of taproot, which does not have a
    /// [`LockScript`] representation (see [`LockScriptError`]).
    fn to_lock_script(&self, strategy: ConvertInfo) -> Result<LockScript, LockScriptError>;
}

/// Conversion for data types (public keys, different types of script) into
/// a `scriptPubkey` (using [`PubkeyScript`] type) using particular conversion
/// [`ConvertInfo`]
pub trait ToPubkeyScript {
    /// Converts data type to [`PubkeyScript`]. Returns `None` if the conversion
    /// is applied to uncompressed public key in segwit context and for taproot
    /// context, where different types of bitcoin_scripts and public keys are
    /// required.
    fn to_pubkey_script(&self, strategy: ConvertInfo) -> Option<PubkeyScript>;
}

/// Script set generation from public keys or a given [`LockScript`] (with
/// [`crate::TapScript`] support planned for the future).
pub trait ToScripts
where
    Self: ToPubkeyScript,
{
    /// Construct all transaction script-produced data; fail by returning `None`
    /// on non-compressed public keys in segwit context
    fn to_scripts(&self, strategy: ConvertInfo) -> Option<ScriptSet> {
        Some(ScriptSet {
            pubkey_script: self.to_pubkey_script(strategy)?,
            sig_script: self.to_sig_script(strategy)?,
            witness: self.to_witness(strategy),
        })
    }

    /// Construct `scriptSig`; fail by returning `None` on non-compressed public
    /// keys in segwit context
    fn to_sig_script(&self, strategy: ConvertInfo) -> Option<SigScript>;

    /// Construct `witness` for segwit contexts only; return `None` on other
    /// contexts
    fn to_witness(&self, strategy: ConvertInfo) -> Option<Witness>;
}

impl ToPubkeyScript for WitnessScript {
    /// Generates `scriptPubkey` for segwit non-taproot contexts. Fails by
    /// returning `None` for the following contexts:
    /// - [`ConvertInfo::Bare`] since no `witness` structure will be present in
    ///   the output transaction;
    /// - [`ConvertInfo::Hashed`] since no `witness` structure will be present
    ///   in the output transaction
    /// - [`ConvertInfo::Taproot`] since taproot does not have an associated
    ///   [`WitnessScript`].
    fn to_pubkey_script(&self, strategy: ConvertInfo) -> Option<PubkeyScript> {
        match strategy {
            ConvertInfo::Bare => None,
            ConvertInfo::Hashed => None,
            ConvertInfo::NestedV0 => Some(RedeemScript::from(self.clone()).to_p2sh()),
            ConvertInfo::SegWitV0 => Some(Script::new_v0_p2wsh(&self.script_hash()).into()),
            ConvertInfo::Taproot => None,
        }
    }
}

impl ToPubkeyScript for RedeemScript {
    /// Generates `scriptPubkey` matching the given [`RedeemScript`]. Fails by
    /// returning `None` for the following contexts, where `redeemScript` is not
    /// present:
    /// - [`ConvertInfo::Bare`];
    /// - [`ConvertInfo::SegWitV0`];
    /// - [`ConvertInfo::Taproot`].
    fn to_pubkey_script(&self, strategy: ConvertInfo) -> Option<PubkeyScript> {
        match strategy {
            ConvertInfo::Bare => None,
            ConvertInfo::Hashed => Some(self.to_p2sh()),
            ConvertInfo::NestedV0 => Some(self.to_p2sh()),
            ConvertInfo::SegWitV0 => None,
            ConvertInfo::Taproot => None,
        }
    }
}

impl ToPubkeyScript for LockScript {
    /// Never returns [`None`]
    fn to_pubkey_script(&self, strategy: ConvertInfo) -> Option<PubkeyScript> {
        Some(match strategy {
            ConvertInfo::Bare => self.to_inner().into(),
            ConvertInfo::Hashed => Script::new_p2sh(&self.script_hash()).into(),
            ConvertInfo::SegWitV0 => Script::new_v0_p2wsh(&self.wscript_hash()).into(),
            ConvertInfo::NestedV0 => WitnessScript::from(self.clone()).to_p2sh_wsh(),
            ConvertInfo::Taproot => return None,
        })
    }
}

impl ToScripts for LockScript {
    /// Never returns [`None`]
    fn to_sig_script(&self, strategy: ConvertInfo) -> Option<SigScript> {
        Some(match strategy {
            // sigScript must contain just a plain signatures, which will be
            // added later
            ConvertInfo::Bare => SigScript::default(),
            ConvertInfo::Hashed => script::Builder::new()
                .push_slice(WitnessScript::from(self.clone()).as_bytes())
                .into_script()
                .into(),
            ConvertInfo::NestedV0 => {
                // Here we support only V0 version, since V1 version can't
                // be generated from `LockScript` and will require
                // `TapScript` source
                RedeemScript::from(WitnessScript::from(self.clone())).into()
            }
            // For any segwit version the scriptSig must be empty (with the
            // exception to the case of P2SH-embedded outputs, which is already
            // covered above
            _ => SigScript::default(),
        })
    }

    fn to_witness(&self, strategy: ConvertInfo) -> Option<Witness> {
        match strategy {
            ConvertInfo::Bare | ConvertInfo::Hashed => None,
            ConvertInfo::SegWitV0 | ConvertInfo::NestedV0 => {
                let witness_script = WitnessScript::from(self.clone());
                Some(Witness::from_vec(vec![witness_script.to_bytes()]))
            }
            ConvertInfo::Taproot => None,
        }
    }
}

impl ToPubkeyScript for bitcoin::PublicKey {
    fn to_pubkey_script(&self, strategy: ConvertInfo) -> Option<PubkeyScript> {
        match strategy {
            ConvertInfo::Bare => Some(Script::new_p2pk(self).into()),
            ConvertInfo::Hashed => Some(Script::new_p2pkh(&self.pubkey_hash()).into()),
            // Uncompressed key in SegWit context
            ConvertInfo::NestedV0 | ConvertInfo::SegWitV0 if !self.compressed => None,
            ConvertInfo::NestedV0 | ConvertInfo::SegWitV0 => self.inner.to_pubkey_script(strategy),
            // Bitcoin public key can't be used in Taproot context
            ConvertInfo::Taproot => None,
        }
    }
}

impl ToScripts for bitcoin::PublicKey {
    fn to_sig_script(&self, strategy: ConvertInfo) -> Option<SigScript> {
        Some(match strategy {
            // scriptSig must contain just a plain signatures, which will be
            // added later
            ConvertInfo::Bare => SigScript::default(),
            ConvertInfo::Hashed => script::Builder::new()
                .push_slice(&self.to_bytes())
                .into_script()
                .into(),
            ConvertInfo::NestedV0 => {
                let redeem_script =
                    LockScript::from(self.to_pubkey_script(ConvertInfo::SegWitV0)?.into_inner());
                script::Builder::new()
                    .push_slice(redeem_script.as_bytes())
                    .into_script()
                    .into()
            }
            // For any segwit version the scriptSig must be empty (with the
            // exception to the case of P2SH-embedded outputs, which is already
            // covered above
            _ => SigScript::default(),
        })
    }

    fn to_witness(&self, strategy: ConvertInfo) -> Option<Witness> {
        match strategy {
            ConvertInfo::Bare | ConvertInfo::Hashed => None,
            ConvertInfo::SegWitV0 | ConvertInfo::NestedV0 => {
                Some(Witness::from_vec(vec![self.to_bytes()]))
            }
            // Bitcoin public key can't be used in Taproot context
            ConvertInfo::Taproot => None,
        }
    }
}

impl ToPubkeyScript for secp256k1::PublicKey {
    /// Never returns [`None`]
    fn to_pubkey_script(&self, strategy: ConvertInfo) -> Option<PubkeyScript> {
        let pk = bitcoin::PublicKey::new(*self);
        Some(
            match strategy {
                ConvertInfo::Bare => Script::new_p2pk(&pk),
                ConvertInfo::Hashed => Script::new_p2pkh(&pk.pubkey_hash()),
                ConvertInfo::SegWitV0 => Script::new_v0_p2wpkh(&pk.wpubkey_hash()?),
                ConvertInfo::NestedV0 => {
                    let pubkey_script = Script::new_p2pkh(&pk.pubkey_hash());
                    let redeem_script = RedeemScript::from_inner(pubkey_script);
                    Script::new_p2sh(&redeem_script.script_hash())
                }
                ConvertInfo::Taproot => return None,
            }
            .into(),
        )
    }
}

impl ToScripts for secp256k1::PublicKey {
    #[inline]
    fn to_sig_script(&self, strategy: ConvertInfo) -> Option<SigScript> {
        bitcoin::PublicKey::new(*self).to_sig_script(strategy)
    }

    #[inline]
    fn to_witness(&self, strategy: ConvertInfo) -> Option<Witness> {
        bitcoin::PublicKey::new(*self).to_witness(strategy)
    }
}

/// Shorthand methods for converting into different forms of [`PubkeyScript`]
pub trait ToP2pkh {
    /// Convert to P2PKH `scriptPubkey`
    fn to_p2pkh(&self) -> Option<PubkeyScript>;
    /// Convert to segwit native P2WPKH `scriptPubkey`
    fn to_p2wpkh(&self) -> Option<PubkeyScript>;
    /// Convert to segwit legacy P2WPKH-in-P2SH `scriptPubkey`
    fn to_p2sh_wpkh(&self) -> Option<PubkeyScript>;
}

#[cfg(feature = "miniscript")]
impl<T> ToP2pkh for T
where
    T: ToPublicKey,
{
    fn to_p2pkh(&self) -> Option<PubkeyScript> {
        self.to_public_key().to_pubkey_script(ConvertInfo::Hashed)
    }

    fn to_p2wpkh(&self) -> Option<PubkeyScript> {
        self.to_public_key().to_pubkey_script(ConvertInfo::SegWitV0)
    }

    fn to_p2sh_wpkh(&self) -> Option<PubkeyScript> {
        self.to_public_key().to_pubkey_script(ConvertInfo::NestedV0)
    }
}