1 files changed, 64 insertions, 2 deletions
diff --git a/src/wallet/scriptpubkeyman.cpp b/src/wallet/scriptpubkeyman.cpp
index b5272be83b..0c1da43b48 100644
--- a/src/wallet/scriptpubkeyman.cpp
+++ b/src/wallet/scriptpubkeyman.cpp
@@ -1974,9 +1974,71 @@ SigningResult DescriptorScriptPubKeyMan::SignMessage(const std::string& message,
     return SigningResult::OK;
 }
 
-TransactionError DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbt, int sighash_type, bool sign, bool bip32derivs) const
+TransactionError DescriptorScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psbtx, int sighash_type, bool sign, bool bip32derivs) const
 {
-    return TransactionError::INVALID_PSBT;
+    for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
+        const CTxIn& txin = psbtx.tx->vin[i];
+        PSBTInput& input = psbtx.inputs.at(i);
+
+        if (PSBTInputSigned(input)) {
+            continue;
+        }
+
+        // Verify input looks sane. This will check that we have at most one uxto, witness or non-witness.
+        if (!input.IsSane()) {
+            return TransactionError::INVALID_PSBT;
+        }
+
+        // Get the Sighash type
+        if (sign && input.sighash_type > 0 && input.sighash_type != sighash_type) {
+            return TransactionError::SIGHASH_MISMATCH;
+        }
+
+        // Get the scriptPubKey to know which SigningProvider to use
+        CScript script;
+        if (!input.witness_utxo.IsNull()) {
+            script = input.witness_utxo.scriptPubKey;
+        } else if (input.non_witness_utxo) {
+            if (txin.prevout.n >= input.non_witness_utxo->vout.size()) {
+                return TransactionError::MISSING_INPUTS;
+            }
+            script = input.non_witness_utxo->vout[txin.prevout.n].scriptPubKey;
+        } else {
+            // There's no UTXO so we can just skip this now
+            continue;
+        }
+        SignatureData sigdata;
+        input.FillSignatureData(sigdata);
+
+        std::unique_ptr<FlatSigningProvider> keys = MakeUnique<FlatSigningProvider>();
+        std::unique_ptr<FlatSigningProvider> script_keys = GetSigningProvider(script, sign);
+        if (script_keys) {
+            *keys = Merge(*keys, *script_keys);
+        } else {
+            // Maybe there are pubkeys listed that we can sign for
+            script_keys = MakeUnique<FlatSigningProvider>();
+            for (const auto& pk_pair : input.hd_keypaths) {
+                const CPubKey& pubkey = pk_pair.first;
+                std::unique_ptr<FlatSigningProvider> pk_keys = GetSigningProvider(pubkey);
+                if (pk_keys) {
+                    *keys = Merge(*keys, *pk_keys);
+                }
+            }
+        }
+
+        SignPSBTInput(HidingSigningProvider(keys.get(), !sign, !bip32derivs), psbtx, i, sighash_type);
+    }
+
+    // Fill in the bip32 keypaths and redeemscripts for the outputs so that hardware wallets can identify change
+    for (unsigned int i = 0; i < psbtx.tx->vout.size(); ++i) {
+        std::unique_ptr<SigningProvider> keys = GetSolvingProvider(psbtx.tx->vout.at(i).scriptPubKey);
+        if (!keys) {
+            continue;
+        }
+        UpdatePSBTOutput(HidingSigningProvider(keys.get(), true, !bip32derivs), psbtx, i);
+    }
+
+    return TransactionError::OK;
 }
 
 const CKeyMetadata* DescriptorScriptPubKeyMan::GetMetadata(const CTxDestination& dest) const