From 63dd30393cde7e3a53ac8734ee594affe321748b Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Fri, 30 Sep 2016 11:20:58 -0700
Subject: [PATCH] script: implement minimalif.

---
 lib/protocol/constants.js |  3 ++-
 lib/script/script.js      | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/lib/protocol/constants.js b/lib/protocol/constants.js
index dadbb30f..c49f4697 100644
--- a/lib/protocol/constants.js
+++ b/lib/protocol/constants.js
@@ -775,8 +775,9 @@ exports.flags = {
   VERIFY_CHECKSEQUENCEVERIFY: (1 << 10),
   VERIFY_WITNESS: (1 << 11),
   VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM: (1 << 12),
-  VERIFY_MAST: (1 << 13),
+  VERIFY_MINIMALIF: (1 << 13),
   VERIFY_NULLFAIL: (1 << 14),
+  VERIFY_MAST: (1 << 15), // should be 1 << 13
   VERIFY_SEQUENCE: (1 << 0),
   MEDIAN_TIME_PAST: (1 << 1)
 };
diff --git a/lib/script/script.js b/lib/script/script.js
index f8421663..ec9a0c38 100644
--- a/lib/script/script.js
+++ b/lib/script/script.js
@@ -362,33 +362,52 @@ Script.prototype.execute = function execute(stack, flags, tx, index, version) {
         case opcodes.OP_IF:
         case opcodes.OP_NOTIF: {
           val = false;
+
           if (negate === 0) {
             if (stack.length < 1)
               throw new ScriptError('UNBALANCED_CONDITIONAL', op, ip);
+
             val = Script.bool(stack.pop());
+
+            if (version == 1 && (flags & constants.flags.VERIFY_MINIMALIF)) {
+              if (val.length > 1)
+                throw new ScriptError('MINIMALIF');
+
+              if (val.length === 1 && val[0] !== 1)
+                throw new ScriptError('MINIMALIF');
+            }
+
             if (op === opcodes.OP_NOTIF)
               val = !val;
           }
+
           state.push(val);
+
           if (!val)
             negate++;
+
           break;
         }
         case opcodes.OP_ELSE: {
           if (state.length === 0)
             throw new ScriptError('UNBALANCED_CONDITIONAL', op, ip);
+
           state[state.length - 1] = !state[state.length - 1];
+
           if (!state[state.length - 1])
             negate++;
           else
             negate--;
+
           break;
         }
         case opcodes.OP_ENDIF: {
           if (state.length === 0)
             throw new ScriptError('UNBALANCED_CONDITIONAL', op, ip);
+
           if (!state.pop())
             negate--;
+
           break;
         }
         case opcodes.OP_VERIF: