From c65d475f9a29a596c4a170126593c39945e0d7b2 Mon Sep 17 00:00:00 2001
From: wolfbeast <mcwerewolf@gmail.com>
Date: Tue, 21 Nov 2017 11:13:05 +0100
Subject: Force punycode display for IDNs with a <dotless-i/j, combining mark
 above> sequence.

---
 netwerk/dns/nsIDNService.cpp | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/netwerk/dns/nsIDNService.cpp b/netwerk/dns/nsIDNService.cpp
index d4f31027e..73a189b67 100644
--- a/netwerk/dns/nsIDNService.cpp
+++ b/netwerk/dns/nsIDNService.cpp
@@ -797,6 +797,7 @@ bool nsIDNService::isLabelSafe(const nsAString &label)
 
   Script lastScript = Script::INVALID;
   uint32_t previousChar = 0;
+  uint32_t baseChar = 0; // last non-diacritic seen (base char for marks)
   uint32_t savedNumberingSystem = 0;
 // Simplified/Traditional Chinese check temporarily disabled -- bug 857481
 #if 0
@@ -846,11 +847,19 @@ bool nsIDNService::isLabelSafe(const nsAString &label)
       }
     }
 
-    // Check for consecutive non-spacing marks
-    if (previousChar != 0 &&
-        previousChar == ch &&
-        GetGeneralCategory(ch) == HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK) {
-      return false;
+    if (GetGeneralCategory(ch) == HB_UNICODE_GENERAL_CATEGORY_NON_SPACING_MARK) {
+      // Check for consecutive non-spacing marks
+      if (previousChar != 0 && previousChar == ch) {
+        return false;
+      }
+      // Check for diacritics on dotless-i or dotless-j, which would be
+      // indistinguishable from normal accented letter.
+      if ((baseChar == 0x0237 || baseChar == 0x0131) &&
+          ((ch >= 0x0300 && ch <= 0x0314) || ch == 0x031a)) {
+        return false;
+      }
+    } else {
+       baseChar = ch;
     }
 
     // Simplified/Traditional Chinese check temporarily disabled -- bug 857481
-- 
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