[tbb-commits] [tor-browser/tor-browser-38.1.0esr-5.0-1] fixup! Bug 15646: Prevent keyboard layout fingerprinting in KeyboardEvent

[mikeperry at torproject.org]

commit 0396e4f834a31ec0cc7b9c4b853417891a09c43c
Author: Arthur Edelstein <arthuredelstein at gmail.com>
Date:   Mon Jul 27 17:17:15 2015 -0700

    fixup! Bug 15646: Prevent keyboard layout fingerprinting in KeyboardEvent
---
 dom/events/KeyCodeConsensus.h |    9 +++++++--
 dom/events/KeyboardEvent.cpp  |   10 +++++++++-
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/dom/events/KeyCodeConsensus.h b/dom/events/KeyCodeConsensus.h
index 5493c36..53ec7f6 100644
--- a/dom/events/KeyCodeConsensus.h
+++ b/dom/events/KeyCodeConsensus.h
@@ -5,14 +5,15 @@
 
 #include "nsString.h"
 #include "nsDataHashtable.h"
+#include "mozilla/StaticMutex.h"
 
 // KEY_INTERNAL is called by KEY or SHIFT.
-#define KEY_INTERNAL(key, code, keyCode, shift)                    \
+#define KEY_INTERNAL(key, code, keyCode, shift)                     \
     gCodes->Put(NS_LITERAL_STRING(key), NS_LITERAL_STRING(#code));  \
     gKeyCodes->Put(NS_LITERAL_STRING(key), keyCode);                \
     gShiftStates->Put(NS_LITERAL_STRING(key), shift);
 
-// KEY and SHIFT Assign a consensus codeName and keyCode for the given keyName.
+// KEY and SHIFT assign a consensus codeName and keyCode for the given keyName.
 // KEY indicates that shift is off.
 #define KEY(key, code, keyCode) KEY_INTERNAL(key, code, keyCode, false)
 // SHIFT indicates that shift is on.
@@ -26,12 +27,16 @@ static nsDataHashtable<nsStringHashKey, uint32_t>* gKeyCodes;
 // gShiftStates provides a shift value for each keyName.
 static nsDataHashtable<nsStringHashKey, bool>* gShiftStates;
 
+static StaticMutex createKeyCodesMutex;
+
 // Populate the global static maps gCodes, gKeCodes, gShiftStates
 // with their constant values.
 static void createKeyCodes()
 {
   if (gCodes) return;
 
+  StaticMutexAutoLock lock(createKeyCodesMutex);
+
   gCodes = new nsDataHashtable<nsStringHashKey, nsString>();
   gKeyCodes = new nsDataHashtable<nsStringHashKey, uint32_t>();
   gShiftStates = new nsDataHashtable<nsStringHashKey, bool>();
diff --git a/dom/events/KeyboardEvent.cpp b/dom/events/KeyboardEvent.cpp
index 8829b8f..76e6e39 100644
--- a/dom/events/KeyboardEvent.cpp
+++ b/dom/events/KeyboardEvent.cpp
@@ -46,7 +46,15 @@ NS_INTERFACE_MAP_END_INHERITING(UIEvent)
 bool
 KeyboardEvent::AltKey()
 {
-  return mEvent->AsKeyboardEvent()->IsAlt();
+  bool altState = mEvent->AsKeyboardEvent()->IsAlt();
+  if (ResistFingerprinting()) {
+    nsString keyName;
+    GetKey(keyName);
+    bool exists = gCodes->Get(keyName, nullptr);
+    return exists ? false : altState;
+  } else {
+    return altState;
+  }
 }
 
 NS_IMETHODIMP