From c08a11ca4ab46b714427f8a8789984a4728ea167 Mon Sep 17 00:00:00 2001
From: Taco de Wolff <tacodewolff@gmail.com>
Date: Sat, 13 Oct 2018 23:47:19 +1300
Subject: [PATCH] Fix panic for conditional comments, fixes #229

---
 html/html.go      | 4 ++--
 html/html_test.go | 2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/html/html.go b/html/html.go
index 2fdc454baa..8ed61f0d2b 100644
--- a/html/html.go
+++ b/html/html.go
@@ -75,10 +75,10 @@ func (o *Minifier) Minify(m *minify.M, w io.Writer, r io.Reader, _ map[string]st
 				return err
 			}
 		case html.CommentToken:
-			if o.KeepConditionalComments && len(t.Text) > 6 && (bytes.HasPrefix(t.Text, []byte("[if ")) || bytes.Equal(t.Text, []byte("[endif]")) || bytes.Equal(t.Text, []byte("<![endif]"))) {
+			if o.KeepConditionalComments && len(t.Text) > 6 && (bytes.HasPrefix(t.Text, []byte("[if ")) || bytes.HasSuffix(t.Text, []byte("[endif]")) || bytes.HasSuffix(t.Text, []byte("[endif]--"))) {
 				// [if ...] is always 7 or more characters, [endif] is only encountered for downlevel-revealed
 				// see https://msdn.microsoft.com/en-us/library/ms537512(v=vs.85).aspx#syntax
-				if bytes.HasPrefix(t.Data, []byte("<!--[if ")) && len(t.Data) > len("<!--[if ]><![endif]-->") { // downlevel-hidden
+				if bytes.HasPrefix(t.Data, []byte("<!--[if ")) && bytes.HasSuffix(t.Data, []byte("<![endif]-->")) { // downlevel-hidden
 					begin := bytes.IndexByte(t.Data, '>') + 1
 					end := len(t.Data) - len("<![endif]-->")
 					if _, err := w.Write(t.Data[:begin]); err != nil {
diff --git a/html/html_test.go b/html/html_test.go
index dbd11eee32..65822b99b9 100644
--- a/html/html_test.go
+++ b/html/html_test.go
@@ -180,7 +180,9 @@ func TestHTMLKeepConditionalComments(t *testing.T) {
 	}{
 		{`<!--[if IE 6]> <b> </b> <![endif]-->`, `<!--[if IE 6]><b></b><![endif]-->`},
 		{`<![if IE 6]> <b> </b> <![endif]>`, `<![if IE 6]><b></b><![endif]>`},
+		{`<!--[if IE 6]--> <b> </b> <!--[endif]-->`, `<!--[if IE 6]--><b></b><!--[endif]-->`},
 		{`<!--[if !mso]><!--> <b> </b> <!--<![endif]-->`, `<!--[if !mso]><!--><b></b><!--<![endif]-->`},
+		{`<!--[if gt IE 6]><!--> <b> </b> <![endif]-->`, `<!--[if gt IE 6]><!--><b></b><![endif]-->`},
 	}
 
 	m := minify.New()