psbt: Add sighash types to PSBT when not DEFAULT or ALL

When an atypical sighash type is specified by the user, add it to the PSBT so that further signing can enforce sighash type matching.
achow101 · Jan 9, 2025 · 83641b0 · 83641b0
1 parent fe62c50
commit 83641b0
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Showing 2 changed files with 46 additions and 1 deletion.
diff --git a/src/psbt.cpp b/src/psbt.cpp
@@ -423,6 +423,12 @@ PSBTError SignPSBTInput(const SigningProvider& provider, PartiallySignedTransact
     if (!sighash) sighash = utxo.scriptPubKey.IsPayToTaproot() ? SIGHASH_DEFAULT : SIGHASH_ALL;
     if (input.sighash_type && input.sighash_type != sighash) {
         return PSBTError::SIGHASH_MISMATCH;
+    } else {
+        if ((!utxo.scriptPubKey.IsPayToTaproot() && (sighash != SIGHASH_ALL && sighash != SIGHASH_DEFAULT)) ||
+            (utxo.scriptPubKey.IsPayToTaproot() && sighash != SIGHASH_DEFAULT)
+        ) {
+            input.sighash_type = sighash;
+        }
     }
     Assert(sighash.has_value());
 
@@ -502,7 +508,8 @@ bool FinalizePSBT(PartiallySignedTransaction& psbtx)
     bool complete = true;
     const PrecomputedTransactionData txdata = PrecomputePSBTData(psbtx);
     for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
-        complete &= (SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, std::nullopt, nullptr, true) == PSBTError::OK);
+        PSBTInput& input = psbtx.inputs.at(i);
+        complete &= (SignPSBTInput(DUMMY_SIGNING_PROVIDER, psbtx, i, &txdata, input.sighash_type, nullptr, true) == PSBTError::OK);
     }
 
     return complete;

diff --git a/test/functional/rpc_psbt.py b/test/functional/rpc_psbt.py
@@ -237,6 +237,43 @@ def test_sighash_mismatch(self):
 
         wallet.unloadwallet()
 
+    def test_sighash_adding(self):
+        self.log.info("Test adding of sighash type field")
+        self.nodes[0].createwallet("sighash_adding")
+        wallet = self.nodes[0].get_wallet_rpc("sighash_adding")
+        def_wallet = self.nodes[0].get_wallet_rpc(self.default_wallet_name)
+
+        addr = wallet.getnewaddress(address_type="bech32")
+        def_wallet.sendtoaddress(addr, 5)
+        self.generate(self.nodes[0], 6)
+
+        # Make a PSBT
+        psbt = wallet.walletcreatefundedpsbt([], [{def_wallet.getnewaddress(): 1}])["psbt"]
+        psbt = wallet.walletprocesspsbt(psbt=psbt, sighashtype="ALL|ANYONECANPAY", finalize=False)["psbt"]
+
+        # Check that the PSBT has a sighash field on all inputs
+        dec_psbt = self.nodes[0].decodepsbt(psbt)
+        for input in dec_psbt["inputs"]:
+            assert_equal(input["sighash"], "ALL|ANYONECANPAY")
+
+        # Make sure we can still finalize the transaction
+        fin_res = self.nodes[0].finalizepsbt(psbt)
+        assert_equal(fin_res["complete"], True)
+        fin_hex = fin_res["hex"]
+
+        # Change the sighash field to a different value and make sure we still finalize to the same thing
+        mod_psbt = PSBT.from_base64(psbt)
+        mod_psbt.i[0].map[PSBT_IN_SIGHASH_TYPE] = (SIGHASH_ALL).to_bytes(4, byteorder="little")
+        psbt = mod_psbt.to_base64()
+        fin_res = self.nodes[0].finalizepsbt(psbt)
+        assert_equal(fin_res["complete"], True)
+        assert_equal(fin_res["hex"], fin_hex)
+
+        self.nodes[0].sendrawtransaction(fin_res["hex"])
+        self.generate(self.nodes[0], 1)
+
+        wallet.unloadwallet()
+
     def assert_change_type(self, psbtx, expected_type):
         """Assert that the given PSBT has a change output with the given type."""
 
@@ -1088,6 +1125,7 @@ def test_psbt_input_keys(psbt_input, keys):
         assert_raises_rpc_error(-8, "'all' is not a valid sighash parameter.", self.nodes[2].descriptorprocesspsbt, psbt, [descriptor], sighashtype="all")
 
         self.test_sighash_mismatch()
+        self.test_sighash_adding()
 
 if __name__ == '__main__':
     PSBTTest(__file__).main()