Enforce correct coinstake payment

Author: panleone

src/validation.cpp

@@ -11,6 +11,7 @@
 #include "validation.h"
 
 #include "addrman.h"
+#include "amount.h"
 #include "blocksignature.h"
 #include "budget/budgetmanager.h"
 #include "chainparams.h"
@@ -1567,6 +1568,15 @@ static bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockInd
         CAmount txValueOut = tx.GetValueOut();
         if (!tx.IsCoinBase()) {
             CAmount txValueIn = view.GetValueIn(tx);
+            // Check that CoinStake pays the expected amount
+            if (tx.IsCoinStake() && isV6UpgradeEnforced) {
+                CAmount stakeMint = txValueOut - txValueIn;
+                CAmount nExpectedStakeMint = GetBlockValue(pindex->nHeight) - GetMasternodePayment(pindex->nHeight);
+                if (stakeMint != nExpectedStakeMint) {
+                    return state.DoS(100, error("%s: coinstake pays too much (actual=%s vs limit=%s)", __func__, FormatMoney(stakeMint), FormatMoney(nExpectedStakeMint)),
+                        REJECT_INVALID, "bad-blk-stake-amount");
+                }
+            }
             if (!tx.IsCoinStake())
                 nFees += txValueIn - txValueOut;
             nValueIn += txValueIn;