rpc: bumpfee signer support

Author: Sjors

src/wallet/feebumper.cpp

@@ -239,7 +239,22 @@ Result CreateRateBumpTransaction(CWallet& wallet, const uint256& txid, const CCo
 
 bool SignTransaction(CWallet& wallet, CMutableTransaction& mtx) {
     LOCK(wallet.cs_wallet);
-    return wallet.SignTransaction(mtx);
+
+    if (wallet.IsWalletFlagSet(WALLET_FLAG_EXTERNAL_SIGNER)) {
+        // Make a blank psbt
+        PartiallySignedTransaction psbtx(mtx);
+
+        // First fill transaction with our data without signing,
+        // so external signers are not asked to sign more than once.
+        bool complete;
+        wallet.FillPSBT(psbtx, complete, SIGHASH_ALL, false /* sign */, true /* bip32derivs */);
+        const TransactionError err = wallet.FillPSBT(psbtx, complete, SIGHASH_ALL, true /* sign */, false  /* bip32derivs */);
+        if (err != TransactionError::OK) return false;
+        complete = FinalizeAndExtractPSBT(psbtx, mtx);
+        return complete;
+    } else {
+        return wallet.SignTransaction(mtx);
+    }
 }
 
 Result CommitTransaction(CWallet& wallet, const uint256& txid, CMutableTransaction&& mtx, std::vector<bilingual_str>& errors, uint256& bumped_txid)

src/wallet/rpc/spend.cpp

@@ -1010,7 +1010,7 @@ static RPCHelpMan bumpfee_helper(std::string method_name)
     std::shared_ptr<CWallet> const pwallet = GetWalletForJSONRPCRequest(request);
     if (!pwallet) return NullUniValue;
 
-    if (pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS) && !want_psbt) {
+    if (pwallet->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS) && !pwallet->IsWalletFlagSet(WALLET_FLAG_EXTERNAL_SIGNER) && !want_psbt) {
         throw JSONRPCError(RPC_WALLET_ERROR, "bumpfee is not available with wallets that have private keys disabled. Use psbtbumpfee instead.");
     }
 
@@ -1088,6 +1088,9 @@ static RPCHelpMan bumpfee_helper(std::string method_name)
     // For psbtbumpfee, return the base64-encoded unsigned PSBT of the new transaction.
     if (!want_psbt) {
         if (!feebumper::SignTransaction(*pwallet, mtx)) {
+            if (pwallet->IsWalletFlagSet(WALLET_FLAG_EXTERNAL_SIGNER)) {
+                throw JSONRPCError(RPC_WALLET_ERROR, "Transaction incomplete. Try psbtbumpfee instead.");
+            }
             throw JSONRPCError(RPC_WALLET_ERROR, "Can't sign transaction.");
         }
 

test/functional/wallet_signer.py

@@ -13,6 +13,7 @@
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
+    assert_greater_than,
     assert_raises_rpc_error,
 )
 
@@ -150,7 +151,7 @@ def test_valid_signer(self):
         assert_equal(result[1], {'success': True})
         assert_equal(mock_wallet.getwalletinfo()["txcount"], 1)
         dest = self.nodes[0].getnewaddress(address_type='bech32')
-        mock_psbt = mock_wallet.walletcreatefundedpsbt([], {dest:0.5}, 0, {}, True)['psbt']
+        mock_psbt = mock_wallet.walletcreatefundedpsbt([], {dest:0.5}, 0, {'replaceable': True}, True)['psbt']
         mock_psbt_signed = mock_wallet.walletprocesspsbt(psbt=mock_psbt, sign=True, sighashtype="ALL", bip32derivs=True)
         mock_psbt_final = mock_wallet.finalizepsbt(mock_psbt_signed["psbt"])
         mock_tx = mock_psbt_final["hex"]
@@ -190,6 +191,7 @@ def test_valid_signer(self):
 
         self.log.info('Test send using hww1')
 
+        # Don't broadcast transaction yet so the RPC returns the raw hex
         res = hww.send(outputs={dest:0.5},options={"add_to_wallet": False})
         assert(res["complete"])
         assert_equal(res["hex"], mock_tx)
@@ -199,6 +201,25 @@ def test_valid_signer(self):
         res = hww.sendall(recipients=[{dest:0.5}, hww.getrawchangeaddress()],options={"add_to_wallet": False})
         assert(res["complete"])
         assert_equal(res["hex"], mock_tx)
+        # Broadcast transaction so we can bump the fee
+        hww.sendrawtransaction(res["hex"])
+
+        self.log.info('Prepare fee bumped mock PSBT')
+
+        # Now that the transaction is broadcast, bump fee in mock wallet:
+        orig_tx_id = res["txid"]
+        mock_psbt_bumped = mock_wallet.psbtbumpfee(orig_tx_id)["psbt"]
+        mock_psbt_bumped_signed = mock_wallet.walletprocesspsbt(psbt=mock_psbt_bumped, sign=True, sighashtype="ALL", bip32derivs=True)
+
+        with open(os.path.join(self.nodes[1].cwd, "mock_psbt"), "w", encoding="utf8") as f:
+            f.write(mock_psbt_bumped_signed["psbt"])
+
+        self.log.info('Test bumpfee using hww1')
+
+        # Bump fee
+        res = hww.bumpfee(orig_tx_id)
+        assert_greater_than(res["fee"], res["origfee"])
+        assert_equal(res["errors"], [])
 
         # # Handle error thrown by script
         # self.set_mock_result(self.nodes[4], "2")