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75.0.3770.53
cromite/build/patches/getClientRects-getBoundingClientRect-measureText-add-fingerprinting-mitigation.patch
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csagan5 ca366d39b9 Release 75.0.3770.50
2019-05-22 06:11:41 +02:00

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From: csagan5 <32685696+csagan5@users.noreply.github.com>
Date: Fri, 30 Mar 2018 10:09:03 +0200
Subject: getClientRects, getBoundingClientRect, measureText: add
fingerprinting mitigation
Scale the result of Range::getClientRects, Element::getBoundingClientRect and
Canvas::measureText by a random +/-3/1000000th of the original value for each
float in the returned Rect/Quad.
Rationale is that the returned values are within the same order of magnitude
of the floating point precision being used for fingerprinting and sufficient
to poison the well.
See also: http://www.gsd.inesc-id.pt/~mpc/pubs/fingerprinting-trustcom2016.pdf
---
third_party/blink/renderer/core/dom/document.cc | 13 +++++++++++++
third_party/blink/renderer/core/dom/document.h | 5 +++++
third_party/blink/renderer/core/dom/element.cc | 16 ++++++++++++++++
third_party/blink/renderer/core/dom/range.cc | 18 +++++++++++++++++-
.../blink/renderer/core/html/canvas/text_metrics.cc | 18 ++++++++++++++++++
.../blink/renderer/core/html/canvas/text_metrics.h | 2 ++
.../canvas/canvas2d/canvas_rendering_context_2d.cc | 10 +++++++++-
7 files changed, 80 insertions(+), 2 deletions(-)
diff --git a/third_party/blink/renderer/core/dom/document.cc b/third_party/blink/renderer/core/dom/document.cc
--- a/third_party/blink/renderer/core/dom/document.cc
+++ b/third_party/blink/renderer/core/dom/document.cc
@@ -34,6 +34,7 @@
#include "base/auto_reset.h"
#include "base/macros.h"
#include "base/optional.h"
+#include "base/rand_util.h"
#include "cc/input/overscroll_behavior.h"
#include "cc/input/scroll_snap_data.h"
#include "services/metrics/public/cpp/mojo_ukm_recorder.h"
@@ -738,6 +739,10 @@ Document::Document(const DocumentInit& initializer,
// also depend on the url NOT getting immediately set in opened windows.
// See fast/dom/early-frame-url.html
// and fast/dom/location-new-window-no-crash.html, respectively.
+ // add X/Y noise factors that will be used to mitigate fingerprinting
+ shuffleFactorX_ = base::RandDouble();
+ shuffleFactorY_ = base::RandDouble();
+
// FIXME: Can/should we unify this behavior?
if (initializer.ShouldSetURL()) {
SetURL(initializer.Url());
@@ -797,6 +802,14 @@ Range* Document::CreateRangeAdjustedToTreeScope(const TreeScope& tree_scope,
Position::BeforeNode(*shadow_host));
}
+double Document::GetShuffleFactorX() {
+ return shuffleFactorX_;
+}
+
+double Document::GetShuffleFactorY() {
+ return shuffleFactorY_;
+}
+
SelectorQueryCache& Document::GetSelectorQueryCache() {
if (!selector_query_cache_)
selector_query_cache_ = std::make_unique<SelectorQueryCache>();
diff --git a/third_party/blink/renderer/core/dom/document.h b/third_party/blink/renderer/core/dom/document.h
--- a/third_party/blink/renderer/core/dom/document.h
+++ b/third_party/blink/renderer/core/dom/document.h
@@ -392,6 +392,9 @@ class CORE_EXPORT Document : public ContainerNode,
has_xml_declaration_ = has_xml_declaration ? 1 : 0;
}
+ double GetShuffleFactorX();
+ double GetShuffleFactorY();
+
String visibilityState() const;
bool IsPageVisible() const;
bool hidden() const;
@@ -1814,6 +1817,8 @@ class CORE_EXPORT Document : public ContainerNode,
Vector<AXContext*> ax_contexts_;
Member<AXObjectCache> ax_object_cache_;
Member<DocumentMarkerController> markers_;
+ double shuffleFactorX_, shuffleFactorY_;
+
bool update_focus_appearance_after_layout_ = false;
diff --git a/third_party/blink/renderer/core/dom/element.cc b/third_party/blink/renderer/core/dom/element.cc
--- a/third_party/blink/renderer/core/dom/element.cc
+++ b/third_party/blink/renderer/core/dom/element.cc
@@ -1321,6 +1321,15 @@ DOMRectList* Element::getClientRects() {
DCHECK(element_layout_object);
GetDocument().AdjustFloatQuadsForScrollAndAbsoluteZoom(
quads, *element_layout_object);
+
+ // scale all quads
+ auto shuffleX = 1 + (GetDocument().GetShuffleFactorX() - 0.5) * 0.000003;
+ auto shuffleY = 1 + (GetDocument().GetShuffleFactorY() - 0.5) * 0.000003;
+
+ for (FloatQuad& quad : quads) {
+ quad.Scale(shuffleX, shuffleY);
+ }
+
return DOMRectList::Create(quads);
}
@@ -1338,6 +1347,13 @@ DOMRect* Element::getBoundingClientRect() {
DCHECK(element_layout_object);
GetDocument().AdjustFloatRectForScrollAndAbsoluteZoom(result,
*element_layout_object);
+
+ // scale rect by 3/1000000th
+ auto shuffleX = 1 + (GetDocument().GetShuffleFactorX() - 0.5) * 0.000003;
+ auto shuffleY = 1 + (GetDocument().GetShuffleFactorY() - 0.5) * 0.000003;
+
+ result.Scale(shuffleX, shuffleY);
+
return DOMRect::FromFloatRect(result);
}
diff --git a/third_party/blink/renderer/core/dom/range.cc b/third_party/blink/renderer/core/dom/range.cc
--- a/third_party/blink/renderer/core/dom/range.cc
+++ b/third_party/blink/renderer/core/dom/range.cc
@@ -1643,11 +1643,27 @@ DOMRectList* Range::getClientRects() const {
Vector<FloatQuad> quads;
GetBorderAndTextQuads(quads);
+ // scale all quads by 3/1000000th
+ auto shuffleX = 1 + (owner_document_->GetShuffleFactorX() - 0.5) * 0.000003;
+ auto shuffleY = 1 + (owner_document_->GetShuffleFactorY() - 0.5) * 0.000003;
+
+ for (FloatQuad& quad : quads) {
+ quad.Scale(shuffleX, shuffleY);
+ }
+
return DOMRectList::Create(quads);
}
DOMRect* Range::getBoundingClientRect() const {
- return DOMRect::FromFloatRect(BoundingRect());
+ auto rect = BoundingRect();
+
+ // scale rect by 3/1000000th
+ auto shuffleX = 1 + (owner_document_->GetShuffleFactorX() - 0.5) * 0.000003;
+ auto shuffleY = 1 + (owner_document_->GetShuffleFactorY() - 0.5) * 0.000003;
+
+ rect.Scale(shuffleX, shuffleY);
+
+ return DOMRect::FromFloatRect(rect);
}
// TODO(editing-dev): We should make
diff --git a/third_party/blink/renderer/core/html/canvas/text_metrics.cc b/third_party/blink/renderer/core/html/canvas/text_metrics.cc
--- a/third_party/blink/renderer/core/html/canvas/text_metrics.cc
+++ b/third_party/blink/renderer/core/html/canvas/text_metrics.cc
@@ -45,6 +45,24 @@ void TextMetrics::Trace(Visitor* visitor) {
TextMetrics::TextMetrics() : baselines_(Baselines::Create()) {}
+void TextMetrics::Shuffle(const double factor) {
+ // x-direction
+ width_ *= factor;
+ actual_bounding_box_left_ *= factor;
+ actual_bounding_box_right_ *= factor;
+
+ // y-direction
+ font_bounding_box_ascent_ *= factor;
+ font_bounding_box_descent_ *= factor;
+ actual_bounding_box_ascent_ *= factor;
+ actual_bounding_box_descent_ *= factor;
+ em_height_ascent_ *= factor;
+ em_height_descent_ *= factor;
+ baselines_->setAlphabetic(baselines_->alphabetic() * factor);
+ baselines_->setHanging(baselines_->hanging() * factor);
+ baselines_->setIdeographic(baselines_->ideographic() * factor);
+}
+
void TextMetrics::Update(const Font& font,
const TextDirection& direction,
const TextBaseline& baseline,
diff --git a/third_party/blink/renderer/core/html/canvas/text_metrics.h b/third_party/blink/renderer/core/html/canvas/text_metrics.h
--- a/third_party/blink/renderer/core/html/canvas/text_metrics.h
+++ b/third_party/blink/renderer/core/html/canvas/text_metrics.h
@@ -71,6 +71,8 @@ class CORE_EXPORT TextMetrics final : public ScriptWrappable {
void Trace(Visitor*) override;
+ void Shuffle(const double factor);
+
private:
void Update(const Font&,
const TextDirection&,
diff --git a/third_party/blink/renderer/modules/canvas/canvas2d/canvas_rendering_context_2d.cc b/third_party/blink/renderer/modules/canvas/canvas2d/canvas_rendering_context_2d.cc
--- a/third_party/blink/renderer/modules/canvas/canvas2d/canvas_rendering_context_2d.cc
+++ b/third_party/blink/renderer/modules/canvas/canvas2d/canvas_rendering_context_2d.cc
@@ -33,6 +33,8 @@
#include "third_party/blink/renderer/modules/canvas/canvas2d/canvas_rendering_context_2d.h"
+#include "base/rand_util.h"
+
#include "third_party/blink/public/common/features.h"
#include "third_party/blink/public/platform/platform.h"
#include "third_party/blink/public/platform/task_type.h"
@@ -793,8 +795,14 @@ TextMetrics* CanvasRenderingContext2D::measureText(const String& text) {
else
direction = ToTextDirection(GetState().GetDirection(), canvas());
- return TextMetrics::Create(font, direction, GetState().GetTextBaseline(),
+ TextMetrics* textMetrics = TextMetrics::Create(font, direction, GetState().GetTextBaseline(),
GetState().GetTextAlign(), text);
+
+ // scale text metrics by 3/1000000th
+ auto shuffleFactor = 1 + (base::RandDouble() - 0.5) * 0.000003;
+ textMetrics->Shuffle(shuffleFactor);
+
+ return textMetrics;
}
void CanvasRenderingContext2D::DrawTextInternal(
--
2.11.0
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