transaction: allow PSBT input to have both UTXO and WITNESS_UTXO

- make sure they are consistent
- only keep one of them internally (UTXO), and only serialise with UTXO (not both)

fixes #6429

electrum/tests/test_psbt.py

@@ -90,6 +90,12 @@ class TestValidPSBT(TestCaseForTestnet):
         finally:
             constants.set_testnet()
 
+    def test_valid_psbt__input_with_both_witness_utxo_and_nonwitness_utxo(self):
+        # Case: PSBT where an input has both WITNESS_UTXO and UTXO.
+        # test it does not raise
+        tx = tx_from_any(bytes.fromhex('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'))
+        self.assertEqual(1, len(tx.inputs()))
+
 
 class TestInvalidPSBT(TestCaseForTestnet):
     # test cases from BIP-0174
@@ -220,6 +226,11 @@ class TestInvalidPSBT(TestCaseForTestnet):
         with self.assertRaises(SerializationError):
             tx2 = tx_from_any('cHNidP8BAHMCAAAAATAa6YblFqHsisW0vGVz0y+DtGXiOtdhZ9aLOOcwtNvbAAAAAAD/////AnR7AQAAAAAAF6kUA6oXrogrXQ1Usl1jEE5P/s57nqKHYEOZOwAAAAAXqRS5IbG6b3IuS/qDtlV6MTmYakLsg4cAAAAAAAEBHwDKmjsAAAAAFgAU0tlLZK4IWH7vyO6xh8YB6Tn5A3wAAQAWABRi6emC//NN2COWEDFrCQzSo7dHywABACIAIIdrrYMvHRaAFe1BIyqeploYFdnvE8Dvh1n2S1srJ4plIQEAJVEhA7fOI6AcW0vwCmQlN836uzFbZoMyhnR471EwnSvVf4qHUa4A')
 
+    def test_invalid_psbt__input_with_both_witness_utxo_and_nonwitness_utxo_that_are_inconsistent(self):
+        # Case: PSBT where an input has both WITNESS_UTXO and UTXO but which are inconsistent.
+        with self.assertRaises(PSBTInputConsistencyFailure):
+            tx = tx_from_any(bytes.fromhex('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'))
+
 
 class TestPSBTSignerChecks(TestCaseForTestnet):
     # test cases from BIP-0174

electrum/transaction.py

@@ -1126,8 +1126,8 @@ class PSBTSection:
 class PartialTxInput(TxInput, PSBTSection):
     def __init__(self, *args, **kwargs):
         TxInput.__init__(self, *args, **kwargs)
-        self.utxo = None  # type: Optional[Transaction]
+        self._utxo = None  # type: Optional[Transaction]
-        self.witness_utxo = None  # type: Optional[TxOutput]
+        self._witness_utxo = None  # type: Optional[TxOutput]
         self.part_sigs = {}  # type: Dict[bytes, bytes]  # pubkey -> sig
         self.sighash = None  # type: Optional[int]
         self.bip32_paths = {}  # type: Dict[bytes, Tuple[bytes, Sequence[int]]]  # pubkey -> (xpub_fingerprint, path)
@@ -1145,6 +1145,26 @@ class PartialTxInput(TxInput, PSBTSection):
         self._is_p2sh_segwit = None  # type: Optional[bool]  # None means unknown
         self._is_native_segwit = None  # type: Optional[bool]  # None means unknown
 
+    @property
+    def utxo(self):
+        return self._utxo
+
+    @utxo.setter
+    def utxo(self, value: Optional[Transaction]):
+        self._utxo = value
+        self.validate_data()
+        self.ensure_there_is_only_one_utxo()
+
+    @property
+    def witness_utxo(self):
+        return self._witness_utxo
+
+    @witness_utxo.setter
+    def witness_utxo(self, value: Optional[TxOutput]):
+        self._witness_utxo = value
+        self.validate_data()
+        self.ensure_there_is_only_one_utxo()
+
     def to_json(self):
         d = super().to_json()
         d.update({
@@ -1177,6 +1197,10 @@ class PartialTxInput(TxInput, PSBTSection):
             if self.prevout.txid.hex() != self.utxo.txid():
                 raise PSBTInputConsistencyFailure(f"PSBT input validation: "
                                                   f"If a non-witness UTXO is provided, its hash must match the hash specified in the prevout")
+            if self.witness_utxo:
+                if self.utxo.outputs()[self.prevout.out_idx] != self.witness_utxo:
+                    raise PSBTInputConsistencyFailure(f"PSBT input validation: "
+                                                      f"If both non-witness UTXO and witness UTXO are provided, they must be consistent")
         # The following test is disabled, so we are willing to sign non-segwit inputs
         # without verifying the input amount. This means, given a maliciously modified PSBT,
         # for non-segwit inputs, we might end up burning coins as miner fees.
@@ -1208,16 +1232,12 @@ class PartialTxInput(TxInput, PSBTSection):
         if kt == PSBTInputType.NON_WITNESS_UTXO:
             if self.utxo is not None:
                 raise SerializationError(f"duplicate key: {repr(kt)}")
-            if self.witness_utxo is not None:
-                raise SerializationError(f"PSBT input cannot have both PSBT_IN_NON_WITNESS_UTXO and PSBT_IN_WITNESS_UTXO")
             self.utxo = Transaction(val)
             self.utxo.deserialize()
             if key: raise SerializationError(f"key for {repr(kt)} must be empty")
         elif kt == PSBTInputType.WITNESS_UTXO:
             if self.witness_utxo is not None:
                 raise SerializationError(f"duplicate key: {repr(kt)}")
-            if self.utxo is not None:
-                raise SerializationError(f"PSBT input cannot have both PSBT_IN_NON_WITNESS_UTXO and PSBT_IN_WITNESS_UTXO")
             self.witness_utxo = TxOutput.from_network_bytes(val)
             if key: raise SerializationError(f"key for {repr(kt)} must be empty")
         elif kt == PSBTInputType.PARTIAL_SIG:
@@ -1266,9 +1286,10 @@ class PartialTxInput(TxInput, PSBTSection):
             self._unknown[full_key] = val
 
     def serialize_psbt_section_kvs(self, wr):
+        self.ensure_there_is_only_one_utxo()
         if self.witness_utxo:
             wr(PSBTInputType.WITNESS_UTXO, self.witness_utxo.serialize_to_network())
-        elif self.utxo:
+        if self.utxo:
             wr(PSBTInputType.NON_WITNESS_UTXO, bfh(self.utxo.serialize_to_network(include_sigs=True)))
         for pk, val in sorted(self.part_sigs.items()):
             wr(PSBTInputType.PARTIAL_SIG, val, pk)