Merge bitcoin#19215: psbt: Include and allow both non_witness_utxo an…

…d witness_utxo for segwit inputs

84d295e tests: Check that segwit inputs in psbt have both UTXO types (Andrew Chow)
4600479 psbt: always put a non_witness_utxo and don't remove it (Andrew Chow)
5279d8b psbt: Allow both non_witness_utxo and witness_utxo (Andrew Chow)
72f6bec rpc: show both UTXOs in decodepsbt (Andrew Chow)

Pull request description:

  Due to recent changes to hardware wallets, the full previous transaction will need to be provided for segwit inputs. Since some software may be checking for the existence of a `witness_utxo` to determine whether to produce a segwit signature, we keep that field to ease the transition.

  Because all of the sanity checks implemented by the `IsSane` functions were related to having mixed segwit and non-segwit data in a PSBT, those functions are removed as those checks are no longer proper.

  Some tests are updated/removed to accommodate this and a simple test added to check that both UTXOs are being added to segwit inputs.

  As discussed in the wallet IRC meeting, our own signer will not require `non_witness_utxo` for segwit inputs.

ACKs for top commit:
  Sjors:
    utACK 84d295e (didn't retest compared to 836d6fc, but fortunately HWI's CI tracks our master branch, with a bunch of hardware wallet simulators)
  ryanofsky:
    Code review re-ACK 84d295e. No changes since last review, but now I understand the context better. I think it would good to improve the comments as suggested bitcoin#19215 (comment) and maybe refer to
  meshcollider:
    utACK 84d295e

Tree-SHA512: ccc1fd3c16ac3859f5aca4fa489bd40f68be0b81bbdc4dd51188bbf28827a8642dc8b605a37318e5f16cf40f1c4910052dace2f27eca21bb58435f02a443e940

src/psbt.cpp

@@ -42,14 +42,6 @@ bool PartiallySignedTransaction::Merge(const PartiallySignedTransaction& psbt)
     return true;
 }
 
-bool PartiallySignedTransaction::IsSane() const
-{
-    for (PSBTInput input : inputs) {
-        if (!input.IsSane()) return false;
-    }
-    return true;
-}
-
 bool PartiallySignedTransaction::AddInput(const CTxIn& txin, PSBTInput& psbtin)
 {
     if (std::find(tx->vin.begin(), tx->vin.end(), txin) != tx->vin.end()) {
@@ -142,11 +134,6 @@ void PSBTInput::Merge(const PSBTInput& input)
     if (final_script_sig.empty() && !input.final_script_sig.empty()) final_script_sig = input.final_script_sig;
 }
 
-bool PSBTInput::IsSane() const
-{
-    return true;
-}
-
 void PSBTOutput::FillSignatureData(SignatureData& sigdata) const
 {
     if (!redeem_script.empty()) {
@@ -231,11 +218,6 @@ bool SignPSBTInput(const SigningProvider& provider, PartiallySignedTransaction&
     // Get UTXO
     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.
         COutPoint prevout = tx.vin[index].prevout;
@@ -308,10 +290,6 @@ TransactionError CombinePSBTs(PartiallySignedTransaction& out, const std::vector
             return TransactionError::PSBT_MISMATCH;
         }
     }
-    if (!out.IsSane()) {
-        return TransactionError::INVALID_PSBT;
-    }
-
     return TransactionError::OK;
 }
 

src/psbt.h

@@ -56,7 +56,6 @@ struct PSBTInput
     void FillSignatureData(SignatureData& sigdata) const;
     void FromSignatureData(const SignatureData& sigdata);
     void Merge(const PSBTInput& input);
-    bool IsSane() const;
     PSBTInput() {}
 
     template <typename Stream>
@@ -229,7 +228,6 @@ struct PSBTOutput
     void FillSignatureData(SignatureData& sigdata) const;
     void FromSignatureData(const SignatureData& sigdata);
     void Merge(const PSBTOutput& output);
-    bool IsSane() const;
     PSBTOutput() {}
 
     template <typename Stream>
@@ -330,7 +328,6 @@ struct PartiallySignedTransaction
     /** Merge psbt into this. The two psbts must have the same underlying CTransaction (i.e. the
       * same actual Bitcoin transaction.) Returns true if the merge succeeded, false otherwise. */
     [[nodiscard]] bool Merge(const PartiallySignedTransaction& psbt);
-    bool IsSane() const;
     bool AddInput(const CTxIn& txin, PSBTInput& psbtin);
     bool AddOutput(const CTxOut& txout, const PSBTOutput& psbtout);
     PartiallySignedTransaction() {}
@@ -478,10 +475,6 @@ struct PartiallySignedTransaction
         if (outputs.size() != tx->vout.size()) {
             throw std::ios_base::failure("Outputs provided does not match the number of outputs in transaction.");
         }
-        // Sanity check
-        if (!IsSane()) {
-            throw std::ios_base::failure("PSBT is not sane.");
-        }
     }
 
     template <typename Stream>

src/rpc/rawtransaction.cpp

@@ -1264,6 +1264,7 @@ UniValue decodepsbt(const JSONRPCRequest& request)
         const PSBTInput& input = psbtx.inputs[i];
         UniValue in(UniValue::VOBJ);
         // UTXOs
+        bool have_a_utxo = false;
         if (input.non_witness_utxo) {
             UniValue non_wit(UniValue::VOBJ);
             TxToUniv(*input.non_witness_utxo, uint256(), non_wit, false);
@@ -1275,7 +1276,9 @@ UniValue decodepsbt(const JSONRPCRequest& request)
                 // Hack to just not show fee later
                 have_all_utxos = false;
             }
-        } else {
+            have_a_utxo = true;
+        }
+        if (!have_a_utxo) {
             have_all_utxos = false;
         }
 

src/test/fuzz/psbt.cpp

@@ -33,7 +33,6 @@ FUZZ_TARGET(psbt)
     }
 
     (void)psbt.IsNull();
-    (void)psbt.IsSane();
 
     std::optional<CMutableTransaction> tx = psbt.tx;
     if (tx) {
@@ -44,7 +43,6 @@ FUZZ_TARGET(psbt)
     for (const PSBTInput& input : psbt.inputs) {
         (void)PSBTInputSigned(input);
         (void)input.IsNull();
-        (void)input.IsSane();
     }
 
     for (const PSBTOutput& output : psbt.outputs) {

src/wallet/scriptpubkeyman.cpp

@@ -713,11 +713,6 @@ TransactionError LegacyScriptPubKeyMan::FillPSBT(PartiallySignedTransaction& psb
             continue;
         }
 
-        // Verify input looks sane. This will check that we have at most one uxto.
-        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;

src/wallet/wallet.cpp

@@ -3005,11 +3005,6 @@ TransactionError CWallet::FillPSBT(PartiallySignedTransaction& psbtx, bool& comp
             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;
-        }
-
         // If we have no utxo, grab it from the wallet.
         if (!input.non_witness_utxo) {
             const uint256& txhash = txin.prevout.hash;

test/functional/rpc_psbt.py

@@ -68,6 +68,9 @@ def run_test(self):
         # spend single key from node 1
         rawtx = self.nodes[1].walletcreatefundedpsbt([{"txid":txid,"vout":p2pkh_pos}], {self.nodes[1].getnewaddress():9.99})['psbt']
         walletprocesspsbt_out = self.nodes[1].walletprocesspsbt(rawtx)
+        # Make sure it has both types of UTXOs
+        decoded = self.nodes[1].decodepsbt(walletprocesspsbt_out['psbt'])
+        assert 'non_witness_utxo' in decoded['inputs'][0]
         assert_equal(walletprocesspsbt_out['complete'], True)
         self.nodes[1].sendrawtransaction(self.nodes[1].finalizepsbt(walletprocesspsbt_out['psbt'])['hex'])