From 1f2e1fb6d5bfc0952a250c95723b115fc2f6b916 Mon Sep 17 00:00:00 2001
From: Christopher Jeffrey <chjjeffrey@gmail.com>
Date: Wed, 17 Feb 2016 21:32:29 -0800
Subject: [PATCH] add an extra failsafe check to checksig before normalizing
 DER sig length.

---
 lib/bcoin/script.js | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/lib/bcoin/script.js b/lib/bcoin/script.js
index 6ea3fcc6..a7ecacdc 100644
--- a/lib/bcoin/script.js
+++ b/lib/bcoin/script.js
@@ -292,7 +292,10 @@ script.concat = function concat(scripts) {
   return s;
 };
 
-script.checksig = function checksig(msg, sig, key) {
+script.checksig = function checksig(msg, sig, key, flags) {
+  if (flags == null)
+    flags = constants.flags.STANDARD_VERIFY_FLAGS;
+
   if (key.getPublic)
     key = key.getPublic();
 
@@ -306,8 +309,13 @@ script.checksig = function checksig(msg, sig, key) {
 
   // Attempt to normalize the signature
   // length before passing to elliptic.
+  // Note: We only do this for historical data!
   // https://github.com/indutny/elliptic/issues/78
-  sig = script.normalizeDER(sig);
+  if (!((flags & constants.flags.VERIFY_DERSIG)
+      || (flags & constants.flags.VERIFY_LOW_S)
+      || (flags & constants.flags.VERIFY_STRICTENC))) {
+    sig = script.normalizeDER(sig);
+  }
 
   // Use a try catch in case there are
   // any uncaught errors for bad inputs in verify().
@@ -898,7 +906,7 @@ script.execute = function execute(data, stack, tx, index, flags, recurse) {
 
         hash = tx.signatureHash(index, subscript, type);
 
-        res = script.checksig(hash, sig, key);
+        res = script.checksig(hash, sig, key, flags);
         if (o === 'checksigverify') {
           if (!res)
             return false;
@@ -959,7 +967,7 @@ script.execute = function execute(data, stack, tx, index, flags, recurse) {
 
           res = false;
           for (; !res && j < n; j++)
-            res = script.checksig(hash, sig, keys[j]);
+            res = script.checksig(hash, sig, keys[j], flags);
 
           if (res)
             succ++;