[rpc/node] check for high fee before ATMP in clients

Check absurd fee in BroadcastTransaction and RPC,
return TransactionError::MAX_FEE_EXCEEDED instead
of TxValidationResult::TX_NOT_STANDARD because this
is client preference, not a node-wide policy.

1 files changed, 9 insertions, 1 deletions

diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index e60e0a2d9..35b75d6c4 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -947,12 +947,20 @@ static RPCHelpMan testmempoolaccept()
 
     TxValidationState state;
     bool test_accept_res;
-    CAmount fee;
+    CAmount fee{0};
     {
         LOCK(cs_main);
         test_accept_res = AcceptToMemoryPool(mempool, state, std::move(tx),
             nullptr /* plTxnReplaced */, false /* bypass_limits */, max_raw_tx_fee, /* test_accept */ true, &fee);
     }
+
+    // Check that fee does not exceed maximum fee
+    if (test_accept_res && max_raw_tx_fee && fee > max_raw_tx_fee) {
+        result_0.pushKV("allowed", false);
+        result_0.pushKV("reject-reason", "max-fee-exceeded");
+        result.push_back(std::move(result_0));
+        return result;
+    }
     result_0.pushKV("allowed", test_accept_res);
 
     // Only return the fee and vsize if the transaction would pass ATMP.