[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

2 files changed, 6 insertions, 7 deletions

diff --git a/src/wallet/fees.cpp b/src/wallet/fees.cpp
index d620e25f2b..0cac42ba72 100644
--- a/src/wallet/fees.cpp
+++ b/src/wallet/fees.cpp
@@ -21,13 +21,7 @@ CAmount GetRequiredFee(const CWallet& wallet, unsigned int nTxBytes)
 
 CAmount GetMinimumFee(const CWallet& wallet, unsigned int nTxBytes, const CCoinControl& coin_control, const CTxMemPool& pool, const CBlockPolicyEstimator& estimator, FeeCalculation* feeCalc)
 {
-    CAmount fee_needed = GetMinimumFeeRate(wallet, coin_control, pool, estimator, feeCalc).GetFee(nTxBytes);
-    // Always obey the maximum
-    if (fee_needed > maxTxFee) {
-        fee_needed = maxTxFee;
-        if (feeCalc) feeCalc->reason = FeeReason::MAXTXFEE;
-    }
-    return fee_needed;
+    return GetMinimumFeeRate(wallet, coin_control, pool, estimator, feeCalc).GetFee(nTxBytes);
 }
 
 CFeeRate GetRequiredFeeRate(const CWallet& wallet)
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;
 }