Merge #13917: Additional safety checks in PSBT signer

5df6f089b53c5b5859e5a3454c026447e4752f82 More tests of signer checks (Andrew Chow)
7c8bffdc24e005c3044a9a80bbc227b2a39b8605 Test that a non-witness script as witness utxo is not signed (Andrew Chow)
8254e9950f67d750c7f5905bfdef526d825965ed Additional sanity checks in SignPSBTInput (Pieter Wuille)
c05712cb590c8c76729a71d75a290c67ae9e3c06 Only wipe wrong UTXO type data if overwritten by wallet (Pieter Wuille)

Pull request description:

  The current PSBT signing code can end up producing a non-segwit signature, while only the UTXO being spent is provided in the PSBT (as opposed to the entire transaction being spent). This may be used to trick a user to incorrectly decide a transaction has the semantics he intends to sign.

  Fix this by refusing to sign if there is any mismatch between the provided data and what is being signed.

Tree-SHA512: b55790d79d8166e05513fc4c603a982a33710e79dc3c045060cddac6b48a1be3a28ebf8db63f988b6567b15dd27fd09bbaf48846e323c8635376ac20178956f4

1 files changed, 9 insertions, 6 deletions

diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index c03dbc5d2c..281fd46146 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -4504,10 +4504,11 @@ bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, const C
 
         // If we don't know about this input, skip it and let someone else deal with it
         const uint256& txhash = txin.prevout.hash;
-        const auto& it = pwallet->mapWallet.find(txhash);
+        const auto it = pwallet->mapWallet.find(txhash);
         if (it != pwallet->mapWallet.end()) {
             const CWalletTx& wtx = it->second;
             CTxOut utxo = wtx.tx->vout[txin.prevout.n];
+            // Update both UTXOs from the wallet.
             input.non_witness_utxo = wtx.tx;
             input.witness_utxo = utxo;
         }
@@ -4524,11 +4525,13 @@ bool FillPSBT(const CWallet* pwallet, PartiallySignedTransaction& psbtx, const C
             complete &= SignPSBTInput(PublicOnlySigningProvider(pwallet), *psbtx.tx, input, sigdata, i, sighash_type);
         }
 
-        // Drop the unnecessary UTXO
-        if (sigdata.witness) {
-            input.non_witness_utxo = nullptr;
-        } else {
-            input.witness_utxo.SetNull();
+        if (it != pwallet->mapWallet.end()) {
+            // Drop the unnecessary UTXO if we added both from the wallet.
+            if (sigdata.witness) {
+                input.non_witness_utxo = nullptr;
+            } else {
+                input.witness_utxo.SetNull();
+            }
         }
 
         // Get public key paths