Merge bitcoin/bitcoin#21576: rpc, gui: bumpfee signer support

2c07cfacd1745844a1d3c57f2e8617549b9815d7 gui: bumpfee signer support (Sjors Provoost)
7e02a3329797211ed5d35e5f5e7b919c099b78ba rpc: bumpfee signer support (Sjors Provoost)
304ece994504220c355577170409b9200941f2af rpc: document bools in FillPSBT() calls (Sjors Provoost)

Pull request description:

  The `bumpfee` RPC call and GUI fee bump interface now work with an external signer.

ACKs for top commit:
  achow101:
    ACK 2c07cfacd1745844a1d3c57f2e8617549b9815d7
  furszy:
    code review ACK 2c07cfac
  jarolrod:
    tACK 2c07cfa

Tree-SHA512: 0c7b931f76fac67c9e33b9b935f29af6f69ac67a5ffcc586ed2f1676feac427735b1d971723b29ef332bb6fb5762949598ebbf728587e8f0ded95a9bfbb3e7a4

2 files changed, 24 insertions, 6 deletions

diff --git a/src/wallet/feebumper.cpp b/src/wallet/feebumper.cpp
index 6d7bb299cc..7343e8860b 100644
--- a/src/wallet/feebumper.cpp
+++ b/src/wallet/feebumper.cpp
@@ -293,7 +293,22 @@ 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)
diff --git a/src/wallet/rpc/spend.cpp b/src/wallet/rpc/spend.cpp
index fb5e9a425e..24bcae40e0 100644
--- a/src/wallet/rpc/spend.cpp
+++ b/src/wallet/rpc/spend.cpp
@@ -82,10 +82,10 @@ static UniValue FinishTransaction(const std::shared_ptr<CWallet> pwallet, const
     PartiallySignedTransaction psbtx(rawTx);
 
     // First fill transaction with our data without signing,
-    // so external signers are not asked sign more than once.
+    // so external signers are not asked to sign more than once.
     bool complete;
-    pwallet->FillPSBT(psbtx, complete, SIGHASH_DEFAULT, false, true);
-    const TransactionError err{pwallet->FillPSBT(psbtx, complete, SIGHASH_DEFAULT, true, false)};
+    pwallet->FillPSBT(psbtx, complete, SIGHASH_DEFAULT, /*sign=*/false, /*bip32derivs=*/true);
+    const TransactionError err{pwallet->FillPSBT(psbtx, complete, SIGHASH_DEFAULT, /*sign=*/true, /*bip32derivs=*/false)};
     if (err != TransactionError::OK) {
         throw JSONRPCTransactionError(err);
     }
@@ -993,7 +993,7 @@ static RPCHelpMan bumpfee_helper(std::string method_name)
     std::shared_ptr<CWallet> const pwallet = GetWalletForJSONRPCRequest(request);
     if (!pwallet) return UniValue::VNULL;
 
-    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.");
     }
 
@@ -1071,6 +1071,9 @@ 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.");
         }
 
@@ -1667,7 +1670,7 @@ RPCHelpMan walletcreatefundedpsbt()
     // Fill transaction with out data but don't sign
     bool bip32derivs = request.params[4].isNull() ? true : request.params[4].get_bool();
     bool complete = true;
-    const TransactionError err{wallet.FillPSBT(psbtx, complete, 1, false, bip32derivs)};
+    const TransactionError err{wallet.FillPSBT(psbtx, complete, 1, /*sign=*/false, /*bip32derivs=*/bip32derivs)};
     if (err != TransactionError::OK) {
         throw JSONRPCTransactionError(err);
     }