Merge pull request #461 from TheBlueMatt/2020-08-mut-sighash

Expose the witnesses of the tx being hashed in SigHashCache
This commit is contained in:
Andrew Poelstra 2020-09-10 13:04:51 +00:00 committed by GitHub
commit 4e737f708a
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 42 additions and 12 deletions

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@ -25,6 +25,8 @@ use blockdata::script::Script;
use blockdata::transaction::{Transaction, TxIn, SigHashType}; use blockdata::transaction::{Transaction, TxIn, SigHashType};
use consensus::encode::Encodable; use consensus::encode::Encodable;
use std::ops::{Deref, DerefMut};
/// Parts of a sighash which are common across inputs or signatures, and which are /// Parts of a sighash which are common across inputs or signatures, and which are
/// sufficient (in conjunction with a private key) to sign the transaction /// sufficient (in conjunction with a private key) to sign the transaction
#[derive(Clone, PartialEq, Eq, Debug)] #[derive(Clone, PartialEq, Eq, Debug)]
@ -102,9 +104,9 @@ impl SighashComponents {
} }
/// A replacement for SigHashComponents which supports all sighash modes /// A replacement for SigHashComponents which supports all sighash modes
pub struct SigHashCache<'a> { pub struct SigHashCache<R: Deref<Target=Transaction>> {
/// Access to transaction required for various introspection /// Access to transaction required for various introspection
tx: &'a Transaction, tx: R,
/// Hash of all the previous outputs, computed as required /// Hash of all the previous outputs, computed as required
hash_prevouts: Option<sha256d::Hash>, hash_prevouts: Option<sha256d::Hash>,
/// Hash of all the input sequence nos, computed as required /// Hash of all the input sequence nos, computed as required
@ -113,12 +115,12 @@ pub struct SigHashCache<'a> {
hash_outputs: Option<sha256d::Hash>, hash_outputs: Option<sha256d::Hash>,
} }
impl<'a> SigHashCache<'a> { impl<R: Deref<Target=Transaction>> SigHashCache<R> {
/// Compute the sighash components from an unsigned transaction and auxiliary /// Compute the sighash components from an unsigned transaction and auxiliary
/// in a lazy manner when required. /// in a lazy manner when required.
/// For the generated sighashes to be valid, no fields in the transaction may change except for /// For the generated sighashes to be valid, no fields in the transaction may change except for
/// script_sig and witnesses. /// script_sig and witnesses.
pub fn new(tx: &Transaction) -> SigHashCache { pub fn new(tx: R) -> Self {
SigHashCache { SigHashCache {
tx: tx, tx: tx,
hash_prevouts: None, hash_prevouts: None,
@ -189,6 +191,7 @@ impl<'a> SigHashCache<'a> {
zero_hash.consensus_encode(&mut enc).unwrap(); zero_hash.consensus_encode(&mut enc).unwrap();
} }
{
let txin = &self.tx.input[input_index]; let txin = &self.tx.input[input_index];
txin txin
@ -198,6 +201,7 @@ impl<'a> SigHashCache<'a> {
script_code.consensus_encode(&mut enc).unwrap(); script_code.consensus_encode(&mut enc).unwrap();
value.consensus_encode(&mut enc).unwrap(); value.consensus_encode(&mut enc).unwrap();
txin.sequence.consensus_encode(&mut enc).unwrap(); txin.sequence.consensus_encode(&mut enc).unwrap();
}
if sighash != SigHashType::Single && sighash != SigHashType::None { if sighash != SigHashType::Single && sighash != SigHashType::None {
self.hash_outputs().consensus_encode(&mut enc).unwrap(); self.hash_outputs().consensus_encode(&mut enc).unwrap();
@ -215,6 +219,32 @@ impl<'a> SigHashCache<'a> {
} }
} }
impl<R: DerefMut<Target=Transaction>> SigHashCache<R> {
/// When the SigHashCache is initialized with a mutable reference to a transaction instead of a
/// regular reference, this method is available to allow modification to the witnesses.
///
/// This allows in-line signing such as
/// ```
/// use bitcoin::blockdata::transaction::{Transaction, SigHashType};
/// use bitcoin::util::bip143::SigHashCache;
/// use bitcoin::Script;
///
/// let mut tx_to_sign = Transaction { version: 2, lock_time: 0, input: Vec::new(), output: Vec::new() };
/// let input_count = tx_to_sign.input.len();
///
/// let mut sig_hasher = SigHashCache::new(&mut tx_to_sign);
/// for inp in 0..input_count {
/// let prevout_script = Script::new();
/// let _sighash = sig_hasher.signature_hash(inp, &prevout_script, 42, SigHashType::All);
/// // ... sign the sighash
/// sig_hasher.access_witness(inp).push(Vec::new());
/// }
/// ```
pub fn access_witness(&mut self, input_index: usize) -> &mut Vec<Vec<u8>> {
&mut self.tx.input[input_index].witness
}
}
#[cfg(test)] #[cfg(test)]
#[allow(deprecated)] #[allow(deprecated)]
mod tests { mod tests {