evo: prohibit any ProTx with legacy BLS version after basic BLS upgrade

Even though only ProUpRegTx updates the operator key field, it is not
good policy to allow transactions that don't use the version that
defines the masternode's currently active key scheme or higher.

Author: kwvg

src/evo/deterministicmns.cpp

@@ -1422,11 +1422,18 @@ bool CheckProUpServTx(CDeterministicMNManager& dmnman, const CTransaction& tx, g
     }
 
     auto mnList = dmnman.GetListForBlock(pindexPrev);
-    auto mn = mnList.GetMN(opt_ptx->proTxHash);
-    if (!mn) {
+    auto dmn = mnList.GetMN(opt_ptx->proTxHash);
+    if (!dmn) {
         return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-protx-hash");
     }
 
+    const bool is_v23_active{DeploymentActiveAfter(pindexPrev, Params().GetConsensus(), Consensus::DEPLOYMENT_V23)};
+
+    // Don't allow legacy scheme versioned transactions after upgrading to basic scheme
+    if (is_v23_active && dmn->pdmnState->nVersion >= ProTxVersion::BasicBLS && opt_ptx->nVersion == ProTxVersion::LegacyBLS) {
+        return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-protx-version-downgrade");
+    }
+
     // don't allow updating to addresses already used by other MNs
     for (const NetInfoEntry& entry : opt_ptx->netInfo.GetEntries()) {
         if (const auto& service_opt{entry.GetAddrPort()}; service_opt.has_value()) {
@@ -1447,7 +1454,7 @@ bool CheckProUpServTx(CDeterministicMNManager& dmnman, const CTransaction& tx, g
     }
 
     if (opt_ptx->scriptOperatorPayout != CScript()) {
-        if (mn->nOperatorReward == 0) {
+        if (dmn->nOperatorReward == 0) {
             // don't allow setting operator reward payee in case no operatorReward was set
             return state.Invalid(TxValidationResult::TX_BAD_SPECIAL, "bad-protx-operator-payee");
         }
@@ -1461,7 +1468,7 @@ bool CheckProUpServTx(CDeterministicMNManager& dmnman, const CTransaction& tx, g
         // pass the state returned by the function above
         return false;
     }
-    if (check_sigs && !CheckHashSig(*opt_ptx, mn->pdmnState->pubKeyOperator.Get(), state)) {
+    if (check_sigs && !CheckHashSig(*opt_ptx, dmn->pdmnState->pubKeyOperator.Get(), state)) {
         // pass the state returned by the function above
         return false;
     }
@@ -1489,6 +1496,13 @@ bool CheckProUpRegTx(CDeterministicMNManager& dmnman, const CTransaction& tx, gs
         return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-protx-hash");
     }
 
+    const bool is_v23_active{DeploymentActiveAfter(pindexPrev, Params().GetConsensus(), Consensus::DEPLOYMENT_V23)};
+
+    // Don't allow legacy scheme versioned transactions after upgrading to basic scheme
+    if (is_v23_active && dmn->pdmnState->nVersion >= ProTxVersion::BasicBLS && opt_ptx->nVersion == ProTxVersion::LegacyBLS) {
+        return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-protx-version-downgrade");
+    }
+
     // don't allow reuse of payee key for other keys (don't allow people to put the payee key onto an online server)
     if (payoutDest == CTxDestination(PKHash(dmn->pdmnState->keyIDOwner)) || payoutDest == CTxDestination(PKHash(opt_ptx->keyIDVoting))) {
         return state.Invalid(TxValidationResult::TX_BAD_SPECIAL, "bad-protx-payee-reuse");
@@ -1544,8 +1558,16 @@ bool CheckProUpRevTx(CDeterministicMNManager& dmnman, const CTransaction& tx, gs
 
     auto mnList = dmnman.GetListForBlock(pindexPrev);
     auto dmn = mnList.GetMN(opt_ptx->proTxHash);
-    if (!dmn)
+    if (!dmn) {
         return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-protx-hash");
+    }
+
+    const bool is_v23_active{DeploymentActiveAfter(pindexPrev, Params().GetConsensus(), Consensus::DEPLOYMENT_V23)};
+
+    // Don't allow legacy scheme versioned transactions after upgrading to basic scheme
+    if (is_v23_active && dmn->pdmnState->nVersion >= ProTxVersion::BasicBLS && opt_ptx->nVersion == ProTxVersion::LegacyBLS) {
+        return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-protx-version-downgrade");
+    }
 
     if (!CheckInputsHash(tx, *opt_ptx, state)) {
         // pass the state returned by the function above