1 files changed, 20 insertions, 0 deletions
diff --git a/dom/canvas/CanvasUtils.cpp b/dom/canvas/CanvasUtils.cpp
index c7cfed83f6..6c9addf596 100644
--- a/dom/canvas/CanvasUtils.cpp
+++ b/dom/canvas/CanvasUtils.cpp
@@ -126,5 +126,25 @@ CoerceDouble(const JS::Value& v, double* d)
     return true;
 }
 
+bool CheckWriteOnlySecurity(bool aCORSUsed, nsIPrincipal* aPrincipal) {
+  if (!aPrincipal) {
+    return true;
+  }
+
+  if (!aCORSUsed) {
+    nsIGlobalObject* incumbentSettingsObject = dom::GetIncumbentGlobal();
+    if (NS_WARN_IF(!incumbentSettingsObject)) {
+      return true;
+    }
+
+    nsIPrincipal* principal = incumbentSettingsObject->PrincipalOrNull();
+    if (NS_WARN_IF(!principal) || !(principal->Subsumes(aPrincipal))) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
 } // namespace CanvasUtils
 } // namespace mozilla