From e748772fff87929366f707742cee3bb3cc0fe11b Mon Sep 17 00:00:00 2001
From: Duke <duke@hush.is>
Date: Sat, 17 May 2025 10:23:51 -0400
Subject: [PATCH] Validate -ac_minopreturnfee as a consensus rule

---
 src/main.cpp | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/src/main.cpp b/src/main.cpp
index 513413421..ff3c3ea64 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -2678,6 +2678,31 @@ namespace Consensus {
         if (!MoneyRange(nFees))
             return state.DoS(100, error("CheckInputs(): nFees out of range"),
                              REJECT_INVALID, "bad-txns-fee-outofrange");
+
+        //NOTE: Since we have access to fee here, verify that opreturn pays
+        //required minimum fee, even though this is a check on outputs not
+        //inputs. If we don't do it here we would need to duplicate already
+        //done work somewhere else
+
+        if ( ASSETCHAINS_MINOPRETURNFEE > 0 ) {
+            BOOST_FOREACH(const CTxOut& txout, tx.vout) {
+                const bool isopret = txout.scriptPubKey.IsOpReturn();
+
+                // HUSH+DRGX do not use -ac_minopreturnfee so this does not (yet)
+                // affect those chains, they will need a height activated consensus
+                // change
+
+                if ( isopret ) {
+                    // Is there any difference between nTxFee and nFees ?
+                    // They seem to be 2 vars with the same value
+                    fprintf(stderr,"%s: opreturn=1 nFees=%ld nTxFee=%ld\n", __func__, nFees, nTxFee);
+                    if (nTxFee < ASSETCHAINS_MINOPRETURNFEE) {
+                        return state.DoS(100,error("CheckInputs(): tx does not have required mininum fee for OP_RETURN"), REJECT_INVALID, "bad-txns-minopreturnfee");
+                    }
+                }
+            }
+        }
+
         return true;
     }
 }// namespace Consensus