[Validation] Reject under-minting blocks

Author: random-zebra

src/masternode-payments.cpp

@@ -198,10 +198,11 @@ void DumpMasternodePayments()
 
 bool IsBlockValueValid(int nHeight, CAmount& nExpectedValue, CAmount nMinted, CAmount& nBudgetAmt)
 {
+    const Consensus::Params& consensus = Params().GetConsensus();
     if (!masternodeSync.IsSynced()) {
         //there is no budget data to use to check anything
         //super blocks will always be on these blocks, max 100 per budgeting
-        if (nHeight % Params().GetConsensus().nBudgetCycleBlocks < 100) {
+        if (nHeight % consensus.nBudgetCycleBlocks < 100) {
             if (Params().IsTestnet()) {
                 return true;
             }
@@ -218,7 +219,9 @@ bool IsBlockValueValid(int nHeight, CAmount& nExpectedValue, CAmount nMinted, CA
         }
     }
 
-    return nMinted <= nExpectedValue;
+    // !todo: remove after V6 enforcement and default it to true
+    const bool isV6UpgradeEnforced = consensus.NetworkUpgradeActive(nHeight, Consensus::UPGRADE_V6_0);
+    return (!isV6UpgradeEnforced || nMinted >= 0) && nMinted <= nExpectedValue;
 }
 
 bool IsBlockPayeeValid(const CBlock& block, const CBlockIndex* pindexPrev)

src/test/budget_tests.cpp

@@ -56,11 +56,13 @@ BOOST_AUTO_TEST_CASE(budget_value)
 BOOST_FIXTURE_TEST_CASE(block_value, TestnetSetup)
 {
     enableMnSyncAndSuperblocksPayment();
-    // regular block
     int nHeight = 100; std::string strError;
     const CAmount nBlockReward = GetBlockValue(nHeight);
     CAmount nExpectedRet = nBlockReward;
     CAmount nBudgetAmtRet = 0;
+
+    // regular block
+    BOOST_CHECK(IsBlockValueValid(nHeight, nExpectedRet, 0, nBudgetAmtRet));
     BOOST_CHECK(IsBlockValueValid(nHeight, nExpectedRet, nBlockReward-1, nBudgetAmtRet));
     BOOST_CHECK_EQUAL(nExpectedRet, nBlockReward);
     BOOST_CHECK_EQUAL(nBudgetAmtRet, 0);
@@ -127,6 +129,16 @@ BOOST_FIXTURE_TEST_CASE(block_value, TestnetSetup)
     BOOST_CHECK_EQUAL(nBudgetAmtRet, 0);
 }
 
+BOOST_FIXTURE_TEST_CASE(block_value_undermint, RegTestingSetup)
+{
+    int nHeight = 100;
+    CAmount nExpectedRet = GetBlockValue(nHeight);
+    CAmount nBudgetAmtRet = 0;
+    // under-minting blocks are invalid after v6
+    BOOST_CHECK(IsBlockValueValid(nHeight, nExpectedRet, -1, nBudgetAmtRet));
+    UpdateNetworkUpgradeParameters(Consensus::UPGRADE_V6_0, Consensus::NetworkUpgrade::ALWAYS_ACTIVE);
+    BOOST_CHECK(!IsBlockValueValid(nHeight, nExpectedRet, -1, nBudgetAmtRet));
+}
 
 /**
  * 1) Create two proposals and two budget finalizations with a different proposal payment order: