Merge #14780: PSBT backports to 0.17

7bee41452b Add test for conversion from non-witness to witness UTXO (Pieter Wuille)
ff56bb9b44 Add regression test for PSBT signing bug #14473 (Glenn Willen)
db445d4e5a Refactor PSBTInput signing to enforce invariant (Glenn Willen)
ad94165db9 Simplify arguments to SignPSBTInput (Glenn Willen)
39ece4fc28 Add bool PSBTInputSigned (Glenn Willen)
70ee1f8709 New PartiallySignedTransaction constructor from CTransction (Glenn Willen)
a9eab081d5 Remove redundant txConst parameter to FillPSBT (Glenn Willen)
cfdd6b2f6c More concise conversion of CDataStream to string (Glenn Willen)
a3fe125490 check that a separator is found for psbt inputs, outputs, and global map (Andrew Chow)

Pull request description:

  This is a backport of #14588, #14377, and #14197's test to 0.17.

Tree-SHA512: 07535ec69a878a63b549e5e463345e233f34662dff805202614cf2ffc896c6d1981363e6d06d02db2e02d815075ad8ebdc5f93f637052cff8c8cbe6c8dfa096a

1 files changed, 34 insertions, 10 deletions

diff --git a/src/script/sign.cpp b/src/script/sign.cpp
index 1ab5051ff..f97d6a253 100644
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -233,10 +233,17 @@ bool ProduceSignature(const SigningProvider& provider, const BaseSignatureCreato
     return sigdata.complete;
 }
 
-bool SignPSBTInput(const SigningProvider& provider, const CMutableTransaction& tx, PSBTInput& input, SignatureData& sigdata, int index, int sighash)
+bool PSBTInputSigned(PSBTInput& input)
 {
-    // if this input has a final scriptsig or scriptwitness, don't do anything with it
-    if (!input.final_script_sig.empty() || !input.final_script_witness.IsNull()) {
+    return !input.final_script_sig.empty() || !input.final_script_witness.IsNull();
+}
+
+bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction& psbt, SignatureData& sigdata, int index, int sighash)
+{
+    PSBTInput& input = psbt.inputs.at(index);
+    const CMutableTransaction& tx = *psbt.tx;
+
+    if (PSBTInputSigned(input)) {
         return true;
     }
 
@@ -246,15 +253,19 @@ bool SignPSBTInput(const SigningProvider& provider, const CMutableTransaction& t
     // Get UTXO
     bool require_witness_sig = false;
     CTxOut utxo;
+
+    // Verify input sanity, which checks that at most one of witness or non-witness utxos is provided.
+    if (!input.IsSane()) {
+        return false;
+    }
+
     if (input.non_witness_utxo) {
         // If we're taking our information from a non-witness UTXO, verify that it matches the prevout.
-        if (input.non_witness_utxo->GetHash() != tx.vin[index].prevout.hash) return false;
-        // If both witness and non-witness UTXO are provided, verify that they match. This check shouldn't
-        // matter, as the PSBT deserializer enforces only one of both is provided, and the only way both
-        // can be present is when they're added simultaneously by FillPSBT (in which case they always match).
-        // Still, check in order to not rely on callers to enforce this.
-        if (!input.witness_utxo.IsNull() && input.non_witness_utxo->vout[tx.vin[index].prevout.n] != input.witness_utxo) return false;
-        utxo = input.non_witness_utxo->vout[tx.vin[index].prevout.n];
+        COutPoint prevout = tx.vin[index].prevout;
+        if (input.non_witness_utxo->GetHash() != prevout.hash) {
+            return false;
+        }
+        utxo = input.non_witness_utxo->vout[prevout.n];
     } else if (!input.witness_utxo.IsNull()) {
         utxo = input.witness_utxo;
         // When we're taking our information from a witness UTXO, we can't verify it is actually data from
@@ -272,6 +283,13 @@ bool SignPSBTInput(const SigningProvider& provider, const CMutableTransaction& t
     // Verify that a witness signature was produced in case one was required.
     if (require_witness_sig && !sigdata.witness) return false;
     input.FromSignatureData(sigdata);
+
+    // If we have a witness signature, use the smaller witness UTXO.
+    if (sigdata.witness) {
+        input.witness_utxo = utxo;
+        input.non_witness_utxo = nullptr;
+    }
+
     return sig_complete;
 }
 
@@ -491,6 +509,12 @@ bool IsSolvable(const SigningProvider& provider, const CScript& script)
     return false;
 }
 
+PartiallySignedTransaction::PartiallySignedTransaction(const CTransaction& tx) : tx(tx)
+{
+    inputs.resize(tx.vin.size());
+    outputs.resize(tx.vout.size());
+}
+
 bool PartiallySignedTransaction::IsNull() const
 {
     return !tx && inputs.empty() && outputs.empty() && unknown.empty();