Commit de975c21 authored by Kathleen Brade's avatar Kathleen Brade Committed by Georg Koppen
Browse files

Bug #6786: Do not expose system colors to CSS or canvas. 

This patch also contains a hack to use properly contrasting colors if the
desktop theme specifies white on black for text colors (see
https://trac.torproject.org/projects/tor/ticket/7920). These color choices are
also not exposed to content.
parent 46305cbb

dom/canvas/CanvasGradient.h

+3 −1
Original line number Diff line number Diff line
@@ -62,8 +62,9 @@ public: 
  }



protected:

  CanvasGradient(CanvasRenderingContext2D* aContext, Type aType)

  CanvasGradient(CanvasRenderingContext2D* aContext, mozilla::css::Loader *aLoader, Type aType)

    : mContext(aContext)

    , mCSSLoader(aLoader)

    , mType(aType)

  {

  }
@@ -71,6 +72,7 @@ protected: 
  nsRefPtr<CanvasRenderingContext2D> mContext;

  nsTArray<mozilla::gfx::GradientStop> mRawStops;

  mozilla::RefPtr<mozilla::gfx::GradientStops> mStops;

  mozilla::css::Loader* mCSSLoader; // not ref counted, it owns us

  Type mType;

  virtual ~CanvasGradient() {}

};

dom/canvas/CanvasRenderingContext2D.cpp

+21 −5
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ 
#include "nsCSSParser.h"

#include "mozilla/css/StyleRule.h"

#include "mozilla/css/Declaration.h"

#include "mozilla/css/Loader.h"

#include "nsComputedDOMStyle.h"

#include "nsStyleSet.h"
@@ -181,9 +182,10 @@ class CanvasRadialGradient : public CanvasGradient 
{

public:

  CanvasRadialGradient(CanvasRenderingContext2D* aContext,

                       mozilla::css::Loader *aLoader,

                       const Point &aBeginOrigin, Float aBeginRadius,

                       const Point &aEndOrigin, Float aEndRadius)

    : CanvasGradient(aContext, Type::RADIAL)

    : CanvasGradient(aContext, aLoader, Type::RADIAL)

    , mCenter1(aBeginOrigin)

    , mCenter2(aEndOrigin)

    , mRadius1(aBeginRadius)
@@ -201,8 +203,9 @@ class CanvasLinearGradient : public CanvasGradient 
{

public:

  CanvasLinearGradient(CanvasRenderingContext2D* aContext,

                       mozilla::css::Loader *aLoader,

                       const Point &aBegin, const Point &aEnd)

    : CanvasGradient(aContext, Type::LINEAR)

    : CanvasGradient(aContext, aLoader, Type::LINEAR)

    , mBegin(aBegin)

    , mEnd(aEnd)

  {
@@ -667,8 +670,16 @@ CanvasGradient::AddColorStop(float offset, const nsAString& colorstr, ErrorResul 
    return;

  }



  nsIPresShell* presShell = nullptr;

  if (mCSSLoader) {

    nsIDocument *doc = mCSSLoader->GetDocument();

    if (doc)

      presShell = doc->GetShell();

  }



  nscolor color;

  if (!nsRuleNode::ComputeColor(value, nullptr, nullptr, color)) {

  if (!nsRuleNode::ComputeColor(value, presShell ? presShell->GetPresContext() : nullptr,

                                nullptr, color)) {

    rv.Throw(NS_ERROR_DOM_SYNTAX_ERR);

    return;

  }
@@ -1917,8 +1928,11 @@ CanvasRenderingContext2D::GetFillRule(nsAString& aString) 
already_AddRefed<CanvasGradient>

CanvasRenderingContext2D::CreateLinearGradient(double x0, double y0, double x1, double y1)

{

  nsIDocument *doc = mCanvasElement ? mCanvasElement->OwnerDoc() : nullptr;

  mozilla::css::Loader *cssLoader = doc ? doc->CSSLoader() : nullptr;



  nsRefPtr<CanvasGradient> grad =

    new CanvasLinearGradient(this, Point(x0, y0), Point(x1, y1));

    new CanvasLinearGradient(this, cssLoader, Point(x0, y0), Point(x1, y1));



  return grad.forget();

}
@@ -1933,8 +1947,10 @@ CanvasRenderingContext2D::CreateRadialGradient(double x0, double y0, double r0, 
    return nullptr;

  }



  nsIDocument *doc = mCanvasElement ? mCanvasElement->OwnerDoc() : nullptr;

  mozilla::css::Loader *cssLoader = doc ? doc->CSSLoader() : nullptr;

  nsRefPtr<CanvasGradient> grad =

    new CanvasRadialGradient(this, Point(x0, y0), r0, Point(x1, y1), r1);

    new CanvasRadialGradient(this, cssLoader, Point(x0, y0), r0, Point(x1, y1), r1);



  return grad.forget();

}

layout/base/nsLayoutUtils.cpp

+50 −0
Original line number Diff line number Diff line
@@ -5097,13 +5097,63 @@ ShouldDarkenColors(nsPresContext* aPresContext) 
nscolor

nsLayoutUtils::GetColor(nsIFrame* aFrame, nsCSSProperty aProperty)

{

  if (aProperty == eCSSProperty_color)

  {

    nscolor nativeColor = NS_RGB(0, 0, 0);

    if (GetNativeTextColor(aFrame, nativeColor))

      return nativeColor;

  }



  nscolor color = aFrame->GetVisitedDependentColor(aProperty);

  if (ShouldDarkenColors(aFrame->PresContext())) {

    color = DarkenColor(color);

  }



  return color;

}



bool

nsLayoutUtils::GetNativeTextColor(nsIFrame* aFrame, nscolor& aColor)

{

  nsPresContext *presContext = aFrame->PresContext();

  if (!presContext->IsChrome()) {

    // If native appearance was used to draw the background of the containing

    // frame, return a contrasting native foreground color instead of the

    // color from the element's style.  This avoids a problem where black

    // text was displayed on a black background when a Windows theme such as

    // "High Contrast Black" was used.  The background is drawn inside

    // nsNativeThemeWin::ClassicDrawWidgetBackground().

    //

    // Because both the background color and this foreground color are used

    // directly without exposing the colors via CSS computed styles, the

    // native colors are not leaked to content.

    nsIFrame* bgFrame =

                    nsCSSRendering::FindNonTransparentBackgroundFrame(aFrame);

    if (bgFrame) {

      const nsStyleDisplay* displayData = bgFrame->StyleDisplay();

      uint8_t widgetType = displayData->mAppearance;

      nsITheme *theme = presContext->GetTheme();

      if (theme && widgetType && theme->ThemeSupportsWidget(presContext,

                                                            bgFrame,

                                                            widgetType)) {

        bool isDisabled = false;

        nsIContent* frameContent = bgFrame->GetContent();

        if (frameContent && frameContent->IsElement()) {

          EventStates es = frameContent->AsElement()->State();

          isDisabled = es.HasState(NS_EVENT_STATE_DISABLED); 

        } 



        if (NS_SUCCEEDED(LookAndFeel::GetColorForNativeAppearance(widgetType,

                                                       isDisabled, &aColor))) {

            return true;

        }

      }

    }

  }



  return false;

}



gfxFloat

nsLayoutUtils::GetSnappedBaselineY(nsIFrame* aFrame, gfxContext* aContext,

                                   nscoord aY, nscoord aAscent)

layout/base/nsLayoutUtils.h

+4 −0
Original line number Diff line number Diff line
@@ -1474,6 +1474,10 @@ public: 
  // Get a suitable foreground color for painting aProperty for aFrame.

  static nscolor GetColor(nsIFrame* aFrame, nsCSSProperty aProperty);



  // Get the native text color if appropriate.  If false is returned, callers

  // should fallback to the CSS color.

  static bool GetNativeTextColor(nsIFrame* aFrame, nscolor& aColor);



  // Get a baseline y position in app units that is snapped to device pixels.

  static gfxFloat GetSnappedBaselineY(nsIFrame* aFrame, gfxContext* aContext,

                                      nscoord aY, nscoord aAscent);

layout/generic/nsFrame.cpp

+5 −1
Original line number Diff line number Diff line
@@ -1575,7 +1575,11 @@ nsIFrame::DisplayCaret(nsDisplayListBuilder* aBuilder, 
nscolor

nsIFrame::GetCaretColorAt(int32_t aOffset)

{

  // Use text color.

  nscolor color = NS_RGB(0, 0, 0);

  if (nsLayoutUtils::GetNativeTextColor(this, color))

    return color;



  // Use CSS text color.

  return StyleColor()->mColor;

}