rpc: bumpfee signer support

2 files changed, 20 insertions, 2 deletions

diff --git a/src/wallet/feebumper.cpp b/src/wallet/feebumper.cpp
index 73042424ad..c66754bfcb 100644
--- a/src/wallet/feebumper.cpp
+++ b/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)
diff --git a/src/wallet/rpc/spend.cpp b/src/wallet/rpc/spend.cpp
index 13df213065..602d7aec96 100644
--- a/src/wallet/rpc/spend.cpp
+++ b/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.");
         }