Added PsbtInputSatisfier

Author: sanket1729

src/psbt/finalizer.rs

@@ -21,7 +21,7 @@
 
 use super::super::Error as MsError;
 use super::{sanity_check, Psbt};
-use super::{Error, InputError};
+use super::{Error, InputError, PsbtInputSatisfier};
 use bitcoin::secp256k1;
 use bitcoin::util::bip143::SigHashCache;
 use bitcoin::{self, PublicKey, Script, SigHashType};
@@ -301,13 +301,13 @@ pub fn finalize(psbt: &mut Psbt) -> Result<(), super::Error> {
     for index in 0..psbt.inputs.len() {
         // Get a descriptor for this input
         let desc = get_descriptor(&psbt, index).map_err(|e| Error::InputError(e, index))?;
-        let input = &mut psbt.inputs[index];
 
         //generate the satisfaction witness and scriptsig
         let (witness, script_sig) = desc
-            .get_satisfication(&input)
+            .get_satisfication(PsbtInputSatisfier::new(&psbt, index))
             .map_err(|e| Error::InputError(InputError::MiniscriptError(e), index))?;
 
+        let input = &mut psbt.inputs[index];
         //Fill in the satisfactions
         input.final_script_sig = if script_sig.is_empty() {
             None

src/psbt/mod.rs

@@ -21,7 +21,6 @@
 
 use std::{error, fmt};
 
-use bitcoin::util::psbt;
 use bitcoin::util::psbt::PartiallySignedTransaction as Psbt;
 
 use bitcoin;
@@ -183,9 +182,35 @@ impl fmt::Display for Error {
     }
 }
 
-impl<Pk: MiniscriptKey + ToPublicKey> Satisfier<Pk> for psbt::Input {
+/// Psbt satisfier for at inputs at a particular index
+/// Takes in &psbt because multiple inputs will share
+/// the same psbt structure
+/// All operations on this structure will panic if index
+/// is more than number of inputs in pbst
+pub struct PsbtInputSatisfier<'psbt> {
+    /// pbst
+    pub psbt: &'psbt Psbt,
+    /// input index
+    pub index: usize,
+}
+
+impl<'psbt> PsbtInputSatisfier<'psbt> {
+    /// create a new PsbtInputsatisfier from
+    /// psbt and index
+    pub fn new(psbt: &'psbt Psbt, index: usize) -> Self {
+        Self {
+            psbt: psbt,
+            index: index,
+        }
+    }
+}
+
+impl<'psbt, Pk: MiniscriptKey + ToPublicKey> Satisfier<Pk> for PsbtInputSatisfier<'psbt> {
     fn lookup_sig(&self, pk: &Pk) -> Option<BitcoinSig> {
-        if let Some(rawsig) = self.partial_sigs.get(&pk.to_public_key()) {
+        if let Some(rawsig) = self.psbt.inputs[self.index]
+            .partial_sigs
+            .get(&pk.to_public_key())
+        {
             // We have already previously checked that all signatures have the
             // correct sighash flag.
             bitcoinsig_from_rawsig(rawsig).ok()
@@ -195,7 +220,7 @@ impl<Pk: MiniscriptKey + ToPublicKey> Satisfier<Pk> for psbt::Input {
     }
 
     fn lookup_pkh_sig(&self, pkh: &Pk::Hash) -> Option<(bitcoin::PublicKey, BitcoinSig)> {
-        if let Some((pk, sig)) = self
+        if let Some((pk, sig)) = self.psbt.inputs[self.index]
             .partial_sigs
             .iter()
             .filter(|&(pubkey, _sig)| pubkey.to_pubkeyhash() == Pk::hash_to_hash160(pkh))