[Consensus] Readd checks removed in 3b778f5

Two importants checks were removed while refactoring to add zPIV
staking. Their equivalents were added to zPIV staking but missing for
simple PIV staking. We add them back with this commit.

src/kernel.cpp

@@ -412,13 +412,14 @@ bool CheckProofOfStake(const CBlock block, uint256& hashProofOfStake, std::uniqu
         stake = std::unique_ptr<CStakeInput>(pivInput);
     }
 
-    CBlockIndex* pindex = stake->GetIndexFrom();
-    if (!pindex)
-        return error("%s: Failed to find the block index", __func__);
+    //Get the
+    CBlockIndex* pindexfrom = stake->GetIndexFrom();
+    if (!pindexfrom)
+        return error("%s: Failed to find the block index for stake origin", __func__);
 
     // Read block header
-    CBlock blockprev;
-    if (!ReadBlockFromDisk(blockprev, pindex->GetBlockPos()))
+    CBlock blockfrom;
+    if (!ReadBlockFromDisk(blockfrom, pindexfrom->GetBlockPos()))
         return error("CheckProofOfStake(): INFO: failed to find block");
 
     uint256 bnTargetPerCoinDay;
@@ -428,8 +429,14 @@ bool CheckProofOfStake(const CBlock block, uint256& hashProofOfStake, std::uniqu
     if (!stake->GetModifier(nStakeModifier))
         return error("%s failed to get modifier for stake input\n", __func__);
 
-    unsigned int nBlockFromTime = blockprev.nTime;
+    unsigned int nBlockFromTime = blockfrom.nTime;
     unsigned int nTxTime = block.nTime;
+    if (!txin.IsZerocoinSpend()) { //Equivalent for zPIV is checked above in ContextualCheckZerocoinStake()
+        if (nTxTime < nBlockFromTime) // Transaction timestamp nTxTime
+            return error("CheckStakeKernelHash() : nTime violation - nBlockFromTime=%d nTimeTx=%d", nBlockFromTime, nTxTime);
+        if (nBlockFromTime + nStakeMinAge > nTxTime) // Min age requirement
+            return error("CheckStakeKernelHash() : min age violation - nBlockFromTime=%d nStakeMinAge=%d nTimeTx=%d", nBlockFromTime, nStakeMinAge, nTxTime);
+    }
     if (!CheckStake(stake->GetUniqueness(), stake->GetValue(), nStakeModifier, bnTargetPerCoinDay, nBlockFromTime,
                     nTxTime, hashProofOfStake)) {
         return error("CheckProofOfStake() : INFO: check kernel failed on coinstake %s, hashProof=%s \n",

src/kernel.h

@@ -29,7 +29,7 @@ bool Stake(CStakeInput* stakeInput, unsigned int nBits, unsigned int nTimeBlockF
 
 // Check kernel hash target and coinstake signature
 // Sets hashProofOfStake on success return
-bool CheckProofOfStake(const CBlock block, uint256& hashProofOfStake, std::unique_ptr<CStakeInput>& stake);
+bool CheckProofOfStake(const CBlock block, uint256& hashProofOfStake, std::unique_ptr<CStakeInput>& stake, int nPreviousBlockHeight);
 
 // Check whether the coinstake timestamp meets protocol
 bool CheckCoinStakeTimestamp(int64_t nTimeBlock, int64_t nTimeTx);