Merge bitcoin/bitcoin#22513: rpc: Allow walletprocesspsbt to sign without finalizing

a99ed8986554fa1ecc854e43ea373d957e598db8 psbt: sign without finalizing (Andrew Chow)

Pull request description:

  It can be useful to sign an input with `walletprocesspsbt` but not finalize that input if it is complete. This PR adds another option to `walletprocesspsbt` to be able to do that. We will still finalize by default.

  This does not materially change the PSBT workflow since `finalizepsbt` needs to be called in order to extract the tx for broadcast.

ACKs for top commit:
  meshcollider:
    utACK a99ed8986554fa1ecc854e43ea373d957e598db8
  Sjors:
    utACK a99ed89

Tree-SHA512: c88e5d3222109c5f4e763b1b9d97ce4655f68f2985a4509caab2d4e7f5bac5047328fd69696e82a330f5c5a333e0312568ae293515689b77a4747ca2f17caca6

1 files changed, 6 insertions, 2 deletions

diff --git a/src/psbt.cpp b/src/psbt.cpp
index b3d8e052bc..6585766807 100644
--- a/src/psbt.cpp
+++ b/src/psbt.cpp
@@ -247,7 +247,7 @@ PrecomputedTransactionData PrecomputePSBTData(const PartiallySignedTransaction&
     return txdata;
 }
 
-bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, const PrecomputedTransactionData* txdata, int sighash, SignatureData* out_sigdata)
+bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, int index, const PrecomputedTransactionData* txdata, int sighash,  SignatureData* out_sigdata, bool finalize)
 {
     PSBTInput& input = psbt.inputs.at(index);
     const CMutableTransaction& tx = *psbt.tx;
@@ -295,6 +295,10 @@ bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction&
     }
     // Verify that a witness signature was produced in case one was required.
     if (require_witness_sig && !sigdata.witness) return false;
+
+    // If we are not finalizing, set sigdata.complete to false to not set the scriptWitness
+    if (!finalize && sigdata.complete) sigdata.complete = false;
+
     input.FromSignatureData(sigdata);
 
     // If we have a witness signature, put a witness UTXO.
@@ -324,7 +328,7 @@ bool FinalizePSBT(PartiallySignedTransaction& psbtx)
     bool complete = true;
     const PrecomputedTransactionData txdata = PrecomputePSBTData(psbtx);
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
-        complete &= SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, SIGHASH_ALL);
+        complete &= SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, SIGHASH_ALL, nullptr, true);
     }
 
     return complete;