Bug 1427229 - Perform validation when sending an EnumSet over IPC. r=botond,froydnj

MozReview-Commit-ID: Cmugi1ldc1Z

--HG--
extra : amend_source : 88b792772ce7948172a68fda03d6d61de66347de

ipc/glue/IPCMessageUtils.h

@@ -15,6 +15,7 @@
 #include "mozilla/DebugOnly.h"
 #include "mozilla/dom/ipc/StructuredCloneData.h"
 #include "mozilla/EnumSet.h"
+#include "mozilla/EnumTypeTraits.h"
 #include "mozilla/Maybe.h"
 #include "mozilla/net/WebSocketFrame.h"
 #include "mozilla/TimeStamp.h"
@@ -24,7 +25,9 @@
 #include "mozilla/TypeTraits.h"
 #include "mozilla/IntegerTypeTraits.h"
 
+#include <limits>
 #include <stdint.h>
+#include <type_traits>
 
 #include "nsExceptionHandler.h"
 #include "nsID.h"
@@ -934,21 +937,43 @@ template<typename T>
 struct ParamTraits<mozilla::EnumSet<T>>
 {
   typedef mozilla::EnumSet<T> paramType;
+  typedef typename mozilla::EnumSet<T>::serializedType serializedType;
 
   static void Write(Message* msg, const paramType& param)
   {
+    MOZ_RELEASE_ASSERT(IsLegalValue(param.serialize()));
     WriteParam(msg, param.serialize());
   }
 
   static bool Read(const Message* msg, PickleIterator* iter, paramType* result)
   {
-    decltype(result->serialize()) tmp;
+    serializedType tmp;
+
     if (ReadParam(msg, iter, &tmp)) {
-      result->deserialize(tmp);
-      return true;
+      if (IsLegalValue(tmp)) {
+        result->deserialize(tmp);
+        return true;
+      }
     }
+
     return false;
   }
+
+  static constexpr serializedType AllEnumBits()
+  {
+    return ~serializedType(0) >>
+           (std::numeric_limits<serializedType>::digits - (mozilla::MaxEnumValue<T>::value + 1));
+  }
+
+  static constexpr bool IsLegalValue(const serializedType value)
+  {
+    static_assert(mozilla::MaxEnumValue<T>::value < std::numeric_limits<serializedType>::digits,
+                  "Enum max value is not in the range!");
+    static_assert(std::is_unsigned<decltype(mozilla::MaxEnumValue<T>::value)>::value,
+                  "Type of MaxEnumValue<T>::value specialization should be unsigned!");
+
+    return (value & AllEnumBits()) == value;
+  }
 };
 
 template<class... Ts>

mfbt/EnumSet.h

@@ -27,6 +27,8 @@ template<typename T>
 class EnumSet
 {
 public:
+  typedef uint32_t serializedType;
+
   EnumSet()
     : mBitField(0)
   {
@@ -209,12 +211,12 @@ public:
     return mBitField == 0;
   }
 
-  uint32_t serialize() const
+  serializedType serialize() const
   {
     return mBitField;
   }
 
-  void deserialize(uint32_t aValue)
+  void deserialize(serializedType aValue)
   {
     incVersion();
     mBitField = aValue;
@@ -320,7 +322,7 @@ private:
   }
 
   static const size_t kMaxBits = 32;
-  uint32_t mBitField;
+  serializedType mBitField;
 
 #ifdef DEBUG
   uint64_t mVersion = 0;

mfbt/EnumTypeTraits.h

@@ -65,6 +65,29 @@ struct EnumTypeFitsWithin
   static_assert(std::is_integral<Storage>::value, "must provide an integral type");
 };
 
+/*
+ * Provides information about highest enum member value.
+ * Each specialization of struct MaxEnumValue should define
+ * "static constexpr unsigned int value".
+ *
+ * example:
+ *
+ *   enum ExampleEnum
+ *   {
+ *     CAT = 0,
+ *     DOG,
+ *     HAMSTER
+ *   };
+ *
+ *   template <>
+ *   struct MaxEnumValue<ExampleEnum>
+ *   {
+ *     static constexpr unsigned int value = static_cast<unsigned int>(HAMSTER);
+ *   };
+ */
+template <typename T>
+struct MaxEnumValue;  // no need to define the primary template
+
 } // namespace mozilla
 
 #endif /* mozilla_EnumTypeTraits_h */