[wallet] abort when attempting to fund a transaction above maxtxfee

FundTransaction calls GetMinimumFee which, when the fee rate is absurdly high, quietly reduced the fee to -maxtxfee. Becaue an absurdly high fee rate is usually the result of a fat finger, aborting seems safer behavior.

Github-Pull: #16257
Rebased-From: 806b0052c3b45415862f74f20ba5f389e5b673de

1 files changed, 5 insertions, 0 deletions

diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 8d52f7eeca..92dc0f5d31 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -2671,6 +2671,11 @@ bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, int& nC
         }
     }
 
+    if (nFeeRet > maxTxFee) {
+        strFailReason = _("Fee exceeds maximum configured by -maxtxfee");
+        return false;
+    }
+
     return true;
 }