From d6534199e5261bac85e8b48aace2cf7b4b6cf041 Mon Sep 17 00:00:00 2001
From: Luke Dashjr <luke-jr+git@utopios.org>
Date: Wed, 1 Feb 2023 15:04:24 -0500
Subject: [PATCH] HACK: script: Treat OP_FALSE OP_IF sequence as a policy
 violation ("upgradable nop")

---
 src/script/interpreter.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index 11b1a1c887..9c0201d8c4 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -504,6 +504,14 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript&
                     return set_error(serror, SCRIPT_ERR_MINIMALDATA);
                 }
                 stack.push_back(vchPushValue);
+                if ((flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS) && opcode == OP_FALSE) {
+                    auto pc_tmp = pc;
+                    opcodetype next_opcode;
+                    valtype dummy_data;
+                    if (script.GetOp(pc_tmp, next_opcode, dummy_data) && next_opcode == OP_IF) {
+                        return set_error(serror, SCRIPT_ERR_DISCOURAGE_UPGRADABLE_NOPS);
+                    }
+                }
             } else if (fExec || (OP_IF <= opcode && opcode <= OP_ENDIF))
             switch (opcode)
             {
-- 
2.39.2