From 31725d8b36fba9bb7810a3e6729a5c6c06de6b74 Mon Sep 17 00:00:00 2001
From: Blake Kaplan <mrbkap@gmail.com>
Date: Wed, 13 Oct 2010 11:37:25 -0700
Subject: [PATCH] Bug 603845 - Protect ourselves against compartments that have
 null principals. r=gal

---
 js/src/xpconnect/wrappers/AccessCheck.cpp | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/js/src/xpconnect/wrappers/AccessCheck.cpp b/js/src/xpconnect/wrappers/AccessCheck.cpp
index ea989b82fda5..e21da3dedba7 100644
--- a/js/src/xpconnect/wrappers/AccessCheck.cpp
+++ b/js/src/xpconnect/wrappers/AccessCheck.cpp
@@ -60,9 +60,17 @@ GetCompartmentPrincipal(JSCompartment *compartment)
 bool
 AccessCheck::isSameOrigin(JSCompartment *a, JSCompartment *b)
 {
+    nsIPrincipal *aprin = GetCompartmentPrincipal(a);
+    nsIPrincipal *bprin = GetCompartmentPrincipal(b);
+
+    // If either a or b doesn't have principals, we don't have enough
+    // information to tell. Seeing as how this is Gecko, we are default-unsafe
+    // in this case.
+    if (!aprin || !bprin)
+        return true;
+
     PRBool cond;
-    return NS_SUCCEEDED(GetCompartmentPrincipal(a)->Equals(GetCompartmentPrincipal(b), &cond)) &&
-           cond;
+    return NS_SUCCEEDED(aprin->Equals(bprin, &cond)) && cond;
 }
 
 bool