Bug 1430173 - Reduce the precision of all explicit clocks to 2ms. r=baku, a=RyanVM

Backport to ESR where we don't have the ResistFingerprinting component.

MozReview-Commit-ID: 9bjycHjR3SF

--HG--
extra : transplant_source : %EA%03%21%0A%E9%3F%8E%CD%7C%D79f%96%85%96%00%5D%7F%95X

dom/base/File.cpp

@@ -29,6 +29,7 @@
 #include "nsStringStream.h"
 #include "nsJSUtils.h"
 #include "nsPrintfCString.h"
+#include "mozilla/TimerClamping.h"
 #include "mozilla/SHA1.h"
 #include "mozilla/CheckedInt.h"
 #include "mozilla/Preferences.h"
@@ -727,7 +728,7 @@ BlobImplBase::GetLastModified(ErrorResult& aRv)
     mLastModificationDate = PR_Now();
   }
 
-  return mLastModificationDate / PR_USEC_PER_MSEC;
+  return TimerClamping::ReduceUsTimeValue(mLastModificationDate) / PR_USEC_PER_MSEC;
 }
 
 void

dom/base/MultipartBlobImpl.cpp

@@ -17,6 +17,7 @@
 #include "nsContentUtils.h"
 #include "nsIScriptError.h"
 #include "nsIXPConnect.h"
+#include "mozilla/TimerClamping.h"
 #include <algorithm>
 
 using namespace mozilla;
@@ -270,8 +271,7 @@ MultipartBlobImpl::SetLengthAndModifiedDate(ErrorResult& aRv)
     //   var x = new Date(); var f = new File(...);
     //   x.getTime() < f.dateModified.getTime()
     // could fail.
-    mLastModificationDate =
-      lastModifiedSet ? lastModified * PR_USEC_PER_MSEC : JS_Now();
+    mLastModificationDate = TimerClamping::ReduceUsTimeValue(lastModifiedSet ? lastModified * PR_USEC_PER_MSEC : JS_Now());
   }
 }
 

dom/base/TimerClamping.cpp

@@ -0,0 +1,35 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "TimerClamping.h"
+
+namespace mozilla {
+
+/* static */
+double
+TimerClamping::ReduceSTimeValue(double aTime)
+{
+  static const double maxResolutionS = .002;
+  return floor(aTime / maxResolutionS) * maxResolutionS;
+}
+
+/* static */
+double
+TimerClamping::ReduceMsTimeValue(double aTime)
+{
+  static const double maxResolutionMs = 2;
+  return floor(aTime / maxResolutionMs) * maxResolutionMs;
+}
+
+/* static */
+double
+TimerClamping::ReduceUsTimeValue(double aTime)
+{
+  static const double maxResolutionUs = 2000;
+  return floor(aTime / maxResolutionUs) * maxResolutionUs;
+}
+
+}

dom/base/TimerClamping.h

@@ -0,0 +1,22 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef TimerClamping_h___
+#define TimerClamping_h___
+
+namespace mozilla {
+
+class TimerClamping
+{
+public:
+  static double ReduceSTimeValue(double aTime);
+  static double ReduceMsTimeValue(double aTime);
+  static double ReduceUsTimeValue(double aTime);
+};
+
+}
+
+#endif /* TimerClamping_h___ */

dom/base/moz.build

@@ -143,6 +143,7 @@ EXPORTS.mozilla += [
     'CORSMode.h',
     'FeedWriterEnabled.h',
     'TextInputProcessor.h',
+    'TimerClamping.h',
     'UseCounter.h',
 ]
 
@@ -363,6 +364,7 @@ UNIFIED_SOURCES += [
     'TextInputProcessor.cpp',
     'ThirdPartyUtil.cpp',
     'Timeout.cpp',
+    'TimerClamping.cpp',
     'TreeWalker.cpp',
     'WebKitCSSMatrix.cpp',
     'WebSocket.cpp',

dom/console/Console.cpp

@@ -30,6 +30,7 @@
 #include "nsContentUtils.h"
 #include "nsDocShell.h"
 #include "nsProxyRelease.h"
+#include "mozilla/TimerClamping.h"
 #include "mozilla/ConsoleTimelineMarker.h"
 #include "mozilla/TimestampTimelineMarker.h"
 
@@ -1338,7 +1339,7 @@ Console::MethodInternal(JSContext* aCx, MethodName aMethodName,
       TimeDuration duration =
         mozilla::TimeStamp::Now() - workerPrivate->NowBaseTimeStamp();
 
-      monotonicTimer = duration.ToMilliseconds();
+      monotonicTimer = TimerClamping::ReduceMsTimeValue(duration.ToMilliseconds());
     }
   }
 

dom/events/Event.cpp

@@ -32,6 +32,7 @@
 #include "nsJSEnvironment.h"
 #include "nsLayoutUtils.h"
 #include "nsPIWindowRoot.h"
+#include "mozilla/TimerClamping.h"
 #include "WorkerPrivate.h"
 
 namespace mozilla {
@@ -1084,6 +1085,12 @@ Event::DefaultPrevented(JSContext* aCx) const
 
 double
 Event::TimeStamp() const
+{
+  return TimerClamping::ReduceMsTimeValue(TimeStampImpl());
+}
+
+double
+Event::TimeStampImpl() const
 {
   if (!sReturnHighResTimeStamp) {
     return static_cast<double>(mEvent->mTime);

dom/events/Event.h

@@ -62,6 +62,7 @@ private:
   void ConstructorInit(EventTarget* aOwner,
                        nsPresContext* aPresContext,
                        WidgetEvent* aEvent);
+  double TimeStampImpl() const;
 
 public:
   static Event* FromSupports(nsISupports* aSupports)

dom/media/DOMMediaStream.cpp

@@ -9,6 +9,7 @@
 #include "nsIScriptError.h"
 #include "nsIUUIDGenerator.h"
 #include "nsPIDOMWindow.h"
+#include "mozilla/TimerClamping.h"
 #include "mozilla/dom/MediaStreamBinding.h"
 #include "mozilla/dom/MediaStreamTrackEvent.h"
 #include "mozilla/dom/LocalMediaStreamBinding.h"
@@ -544,8 +545,8 @@ DOMMediaStream::CurrentTime()
   if (!mPlaybackStream) {
     return 0.0;
   }
-  return mPlaybackStream->
-    StreamTimeToSeconds(mPlaybackStream->GetCurrentTime() - mLogicalStreamStartTime);
+  return TimerClamping::ReduceSTimeValue(mPlaybackStream->
+    StreamTimeToSeconds(mPlaybackStream->GetCurrentTime() - mLogicalStreamStartTime));
 }
 
 void

dom/media/webaudio/AudioContext.cpp

@@ -41,6 +41,7 @@
 #include "nsNetUtil.h"
 #include "nsPIDOMWindow.h"
 #include "nsPrintfCString.h"
+#include "mozilla/TimerClamping.h"
 #include "OscillatorNode.h"
 #include "PannerNode.h"
 #include "PeriodicWave.h"
@@ -746,7 +747,7 @@ double
 AudioContext::CurrentTime() const
 {
   MediaStream* stream = Destination()->Stream();
-  return stream->StreamTimeToSeconds(stream->GetCurrentTime());
+  return TimerClamping::ReduceSTimeValue(stream->StreamTimeToSeconds(stream->GetCurrentTime()));
 }
 
 void

dom/performance/Performance.cpp

@@ -21,6 +21,7 @@
 #include "mozilla/dom/PerformanceObserverBinding.h"
 #include "mozilla/IntegerPrintfMacros.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/TimerClamping.h"
 #include "WorkerPrivate.h"
 #include "WorkerRunnable.h"
 
@@ -228,9 +229,9 @@ Performance::ClearResourceTimings()
 DOMHighResTimeStamp
 Performance::RoundTime(double aTime) const
 {
-  // Round down to the nearest 20us, because if the timer is too accurate people
+  // Round down to the nearest 2ms, because if the timer is too accurate people
   // can do nasty timing attacks with it.
-  const double maxResolutionMs = 0.020;
+  const double maxResolutionMs = 2;
   return floor(aTime / maxResolutionMs) * maxResolutionMs;
 }
 

dom/performance/PerformanceTiming.cpp

@@ -21,7 +21,7 @@ PerformanceTiming::PerformanceTiming(Performance* aPerformance,
                                      DOMHighResTimeStamp aZeroTime)
   : mPerformance(aPerformance),
     mFetchStart(0.0),
-    mZeroTime(aZeroTime),
+    mZeroTime(TimerClamping::ReduceMsTimeValue(aZeroTime)),
     mRedirectCount(0),
     mTimingAllowed(true),
     mAllRedirectsSameOrigin(true),
@@ -117,7 +117,7 @@ PerformanceTiming::FetchStartHighRes()
         ? TimeStampToDOMHighRes(mAsyncOpen)
         : 0.0;
   }
-  return mFetchStart;
+  return TimerClamping::ReduceMsTimeValue(mFetchStart);
 }
 
 DOMTimeMilliSec
@@ -203,7 +203,7 @@ PerformanceTiming::RedirectStartHighRes()
   if (!nsContentUtils::IsPerformanceTimingEnabled() || !IsInitialized()) {
     return mZeroTime;
   }
-  return TimeStampToDOMHighResOrFetchStart(mRedirectStart);
+  return TimeStampToReducedDOMHighResOrFetchStart(mRedirectStart);
 }
 
 DOMTimeMilliSec
@@ -236,7 +236,7 @@ PerformanceTiming::RedirectEndHighRes()
   if (!nsContentUtils::IsPerformanceTimingEnabled() || !IsInitialized()) {
     return mZeroTime;
   }
-  return TimeStampToDOMHighResOrFetchStart(mRedirectEnd);
+  return TimeStampToReducedDOMHighResOrFetchStart(mRedirectEnd);
 }
 
 DOMTimeMilliSec
@@ -259,7 +259,7 @@ PerformanceTiming::DomainLookupStartHighRes()
   if (!nsContentUtils::IsPerformanceTimingEnabled() || !IsInitialized()) {
     return mZeroTime;
   }
-  return TimeStampToDOMHighResOrFetchStart(mDomainLookupStart);
+  return TimeStampToReducedDOMHighResOrFetchStart(mDomainLookupStart);
 }
 
 DOMTimeMilliSec
@@ -276,7 +276,7 @@ PerformanceTiming::DomainLookupEndHighRes()
   }
   // Bug 1155008 - nsHttpTransaction is racy. Return DomainLookupStart when null
   return mDomainLookupEnd.IsNull() ? DomainLookupStartHighRes()
-                                   : TimeStampToDOMHighRes(mDomainLookupEnd);
+                                   : TimerClamping::ReduceMsTimeValue(TimeStampToDOMHighRes(mDomainLookupEnd));
 }
 
 DOMTimeMilliSec
@@ -292,7 +292,7 @@ PerformanceTiming::ConnectStartHighRes()
     return mZeroTime;
   }
   return mConnectStart.IsNull() ? DomainLookupEndHighRes()
-                                : TimeStampToDOMHighRes(mConnectStart);
+                                : TimerClamping::ReduceMsTimeValue(TimeStampToDOMHighRes(mConnectStart));
 }
 
 DOMTimeMilliSec
@@ -329,7 +329,7 @@ PerformanceTiming::ConnectEndHighRes()
   }
   // Bug 1155008 - nsHttpTransaction is racy. Return ConnectStart when null
   return mConnectEnd.IsNull() ? ConnectStartHighRes()
-                              : TimeStampToDOMHighRes(mConnectEnd);
+                              : TimerClamping::ReduceMsTimeValue(TimeStampToDOMHighRes(mConnectEnd));
 }
 
 DOMTimeMilliSec
@@ -344,7 +344,7 @@ PerformanceTiming::RequestStartHighRes()
   if (!nsContentUtils::IsPerformanceTimingEnabled() || !IsInitialized()) {
     return mZeroTime;
   }
-  return TimeStampToDOMHighResOrFetchStart(mRequestStart);
+  return TimeStampToReducedDOMHighResOrFetchStart(mRequestStart);
 }
 
 DOMTimeMilliSec
@@ -363,7 +363,7 @@ PerformanceTiming::ResponseStartHighRes()
      (!mCacheReadStart.IsNull() && mCacheReadStart < mResponseStart)) {
     mResponseStart = mCacheReadStart;
   }
-  return TimeStampToDOMHighResOrFetchStart(mResponseStart);
+  return TimeStampToReducedDOMHighResOrFetchStart(mResponseStart);
 }
 
 DOMTimeMilliSec
@@ -384,7 +384,7 @@ PerformanceTiming::ResponseEndHighRes()
   }
   // Bug 1155008 - nsHttpTransaction is racy. Return ResponseStart when null
   return mResponseEnd.IsNull() ? ResponseStartHighRes()
-                               : TimeStampToDOMHighRes(mResponseEnd);
+                               : TimerClamping::ReduceMsTimeValue(TimeStampToDOMHighRes(mResponseEnd));
 }
 
 DOMTimeMilliSec

dom/performance/PerformanceTiming.h

@@ -10,6 +10,7 @@
 #include "mozilla/Attributes.h"
 #include "nsContentUtils.h"
 #include "nsDOMNavigationTiming.h"
+#include "mozilla/TimerClamping.h"
 #include "nsWrapperCache.h"
 #include "Performance.h"
 
@@ -68,10 +69,10 @@ public:
    *          page), if the given TimeStamp is valid. Otherwise, it will return
    *          the FetchStart timing value.
    */
-  inline DOMHighResTimeStamp TimeStampToDOMHighResOrFetchStart(TimeStamp aStamp)
+  inline DOMHighResTimeStamp TimeStampToReducedDOMHighResOrFetchStart(TimeStamp aStamp)
   {
     return (!aStamp.IsNull())
-        ? TimeStampToDOMHighRes(aStamp)
+        ? TimerClamping::ReduceMsTimeValue(TimeStampToDOMHighRes(aStamp))
         : FetchStartHighRes();
   }
 
@@ -119,7 +120,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetNavigationStart();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetNavigationStart());
   }
 
   DOMTimeMilliSec UnloadEventStart()
@@ -127,7 +128,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetUnloadEventStart();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetUnloadEventStart());
   }
 
   DOMTimeMilliSec UnloadEventEnd()
@@ -135,7 +136,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetUnloadEventEnd();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetUnloadEventEnd());
   }
 
   uint16_t GetRedirectCount() const;
@@ -185,7 +186,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetDomLoading();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetDomLoading());
   }
 
   DOMTimeMilliSec DomInteractive() const
@@ -193,7 +194,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetDomInteractive();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetDomInteractive());
   }
 
   DOMTimeMilliSec DomContentLoadedEventStart() const
@@ -201,7 +202,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetDomContentLoadedEventStart();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetDomContentLoadedEventStart());
   }
 
   DOMTimeMilliSec DomContentLoadedEventEnd() const
@@ -209,7 +210,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetDomContentLoadedEventEnd();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetDomContentLoadedEventEnd());
   }
 
   DOMTimeMilliSec DomComplete() const
@@ -217,7 +218,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetDomComplete();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetDomComplete());
   }
 
   DOMTimeMilliSec LoadEventStart() const
@@ -225,7 +226,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetLoadEventStart();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetLoadEventStart());
   }
 
   DOMTimeMilliSec LoadEventEnd() const
@@ -233,7 +234,7 @@ public:
     if (!nsContentUtils::IsPerformanceTimingEnabled()) {
       return 0;
     }
-    return GetDOMTiming()->GetLoadEventEnd();
+    return TimerClamping::ReduceMsTimeValue(GetDOMTiming()->GetLoadEventEnd());
   }
 
 private:

js/src/jsdate.cpp

@@ -1232,7 +1232,10 @@ date_parse(JSContext* cx, unsigned argc, Value* vp)
 static ClippedTime
 NowAsMillis()
 {
-    return TimeClip(static_cast<double>(PRMJ_Now()) / PRMJ_USEC_PER_MSEC);
+    const double maxResolutionMs = 2;
+    double timestamp = static_cast<double>(PRMJ_Now()) / PRMJ_USEC_PER_MSEC;
+    timestamp = floor(timestamp / maxResolutionMs) * maxResolutionMs;
+    return TimeClip(timestamp);
 }
 
 bool