From 41db9e92d572c0a8facdb94eafdf5d48bb4de1fd Mon Sep 17 00:00:00 2001
From: random-zebra <random.zebra@protonmail.com>
Date: Sat, 11 Sep 2021 18:52:29 +0200
Subject: [PATCH] [Validation] Restore pre-v5.3 guard for under-minting blocks
 rule

---
 src/masternode-payments.cpp |  7 +++++--
 src/test/budget_tests.cpp   | 14 +++++++++++---
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/src/masternode-payments.cpp b/src/masternode-payments.cpp
index 56ed72642ca5..e98249afff8e 100644
--- a/src/masternode-payments.cpp
+++ b/src/masternode-payments.cpp
@@ -224,7 +224,11 @@ bool IsBlockValueValid(int nHeight, CAmount& nExpectedValue, CAmount nMinted, CA
         }
     }
 
-    return nMinted >= 0 && nMinted <= nExpectedValue;
+    if (nMinted < 0 && consensus.NetworkUpgradeActive(nHeight, Consensus::UPGRADE_V5_3)) {
+        return false;
+    }
+
+    return nMinted <= nExpectedValue;
 }
 
 bool IsBlockPayeeValid(const CBlock& block, const CBlockIndex* pindexPrev)
@@ -328,7 +332,6 @@ bool CMasternodePayments::GetLegacyMasternodeTxOut(int nHeight, std::vector<CTxO
     CScript payee;
     if (!GetBlockPayee(nHeight, payee)) {
         //no masternode detected
-        const Consensus::Params& consensus = Params().GetConsensus();
         const uint256& hash = mnodeman.GetHashAtHeight(nHeight - 1);
         MasternodeRef winningNode = mnodeman.GetCurrentMasterNode(hash);
         if (winningNode) {
diff --git a/src/test/budget_tests.cpp b/src/test/budget_tests.cpp
index 79312309ef51..be57f4d85bd0 100644
--- a/src/test/budget_tests.cpp
+++ b/src/test/budget_tests.cpp
@@ -61,9 +61,6 @@ BOOST_FIXTURE_TEST_CASE(block_value, TestnetSetup)
     CAmount nExpectedRet = nBlockReward;
     CAmount nBudgetAmtRet = 0;
 
-    // under-minting
-    BOOST_CHECK(!IsBlockValueValid(nHeight, nExpectedRet, -1, nBudgetAmtRet));
-
     // regular block
     BOOST_CHECK(IsBlockValueValid(nHeight, nExpectedRet, 0, nBudgetAmtRet));
     BOOST_CHECK(IsBlockValueValid(nHeight, nExpectedRet, nBlockReward-1, nBudgetAmtRet));
@@ -132,6 +129,17 @@ 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 v5.3
+    BOOST_CHECK(IsBlockValueValid(nHeight, nExpectedRet, -1, nBudgetAmtRet));
+    UpdateNetworkUpgradeParameters(Consensus::UPGRADE_V5_3, 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:
          BudA pays propA and propB, BudB pays propB and propA.