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// Copyright 2025 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <cstddef>
#include <cstdint>
#include <initializer_list>
#include <memory>
#include "base/test/metrics/histogram_tester.h"
#include "components/viz/test/test_context_provider.h"
#include "testing/gtest/include/gtest/gtest.h"
#include "third_party/blink/public/common/fingerprinting_protection/canvas_noise_token.h"
#include "third_party/blink/renderer/bindings/core/v8/v8_binding_for_testing.h"
#include "third_party/blink/renderer/bindings/core/v8/v8_union_float16array_float32array_uint8clampedarray.h"
#include "third_party/blink/renderer/core/canvas_interventions/canvas_interventions_enums.h"
#include "third_party/blink/renderer/core/canvas_interventions/canvas_interventions_helper.h"
#include "third_party/blink/renderer/core/frame/frame_test_helpers.h"
#include "third_party/blink/renderer/core/frame/local_dom_window.h"
#include "third_party/blink/renderer/core/html/canvas/canvas_rendering_context.h"
#include "third_party/blink/renderer/core/html/canvas/html_canvas_element.h"
#include "third_party/blink/renderer/core/html/canvas/image_data.h"
#include "third_party/blink/renderer/core/offscreencanvas/offscreen_canvas.h"
#include "third_party/blink/renderer/core/testing/page_test_base.h"
#include "third_party/blink/renderer/modules/canvas/canvas2d/canvas_rendering_context_2d.h"
#include "third_party/blink/renderer/modules/canvas/canvas2d/canvas_style_test_utils.h"
#include "third_party/blink/renderer/modules/canvas/canvas2d/path_2d.h"
#include "third_party/blink/renderer/modules/canvas/offscreencanvas2d/offscreen_canvas_rendering_context_2d.h"
#include "third_party/blink/renderer/platform/graphics/gpu/shared_gpu_context.h"
#include "third_party/blink/renderer/platform/graphics/test/gpu_memory_buffer_test_platform.h"
#include "third_party/blink/renderer/platform/graphics/test/gpu_test_utils.h"
#include "third_party/blink/renderer/platform/heap/persistent.h"
#include "third_party/blink/renderer/platform/runtime_feature_state/runtime_feature_state_override_context.h"
#include "third_party/blink/renderer/platform/testing/runtime_enabled_features_test_helpers.h"
namespace blink {
// Raster interface that always returns the same randomized image when read
// back.
class CanvasNoiseTestRasterInterface : public viz::TestRasterInterface {
public:
CanvasNoiseTestRasterInterface() { set_gpu_rasterization(true); }
private:
UNSAFE_BUFFER_USAGE bool ReadbackImagePixels(
const gpu::Mailbox& source_mailbox,
const SkImageInfo& dst_info,
GLuint dst_row_bytes,
int src_x,
int src_y,
int plane_index,
void* dst_pixels) override {
size_t size = dst_info.computeByteSize(dst_row_bytes);
uint8_t* data = static_cast<uint8_t*>(dst_pixels);
for (size_t i = 0; i < size; ++i) {
data[i] = (i % 4 == 3) ? 255 : i % 256;
}
return true;
}
};
class CanvasNoiseTest : public PageTestBase {
public:
void SetUp() override {
test_context_provider_ = viz::TestContextProvider::CreateRaster(
std::make_unique<CanvasNoiseTestRasterInterface>());
InitializeSharedGpuContextRaster(test_context_provider_.get());
PageTestBase::SetUp();
GetDocument().GetSettings()->SetAcceleratedCompositingEnabled(true);
NavigateTo(KURL("https://test.example"));
SetHtmlInnerHTML("<body><canvas id='c' width='300' height='300'></body>");
UpdateAllLifecyclePhasesForTest();
canvas_element_ = To<HTMLCanvasElement>(GetElementById("c"));
CanvasContextCreationAttributesCore attributes;
attributes.alpha = true;
attributes.desynchronized = true;
attributes.premultiplied_alpha = false;
attributes.will_read_frequently =
CanvasContextCreationAttributesCore::WillReadFrequently::kFalse;
canvas_element_->GetCanvasRenderingContext(/*canvas_type=*/"2d",
attributes);
canvas_element_->GetOrCreateCanvasResourceProvider();
CanvasNoiseToken::Set(0x1234567890123456);
EnableInterventions();
}
void TearDown() override {
PageTestBase::TearDown();
SharedGpuContext::Reset();
CanvasRenderingContext::GetCanvasPerformanceMonitor().ResetForTesting();
}
HTMLCanvasElement& CanvasElement() const { return *canvas_element_; }
CanvasRenderingContext2D* Context2D() const {
return static_cast<CanvasRenderingContext2D*>(
CanvasElement().RenderingContext());
}
Document& GetDocument() const { return *GetFrame().DomWindow()->document(); }
ScriptState* GetScriptState() {
return ToScriptStateForMainWorld(GetDocument().GetFrame());
}
void DisableInterventions() {
GetFrame()
.DomWindow()
->GetRuntimeFeatureStateOverrideContext()
->SetCanvasInterventionsForceDisabled();
}
void EnableInterventions() {
GetFrame()
.DomWindow()
->GetRuntimeFeatureStateOverrideContext()
->SetCanvasInterventionsForceEnabled();
}
base::span<uint8_t> GetNoisedPixels(ExecutionContext* ec) {
scoped_refptr<StaticBitmapImage> snapshot =
Context2D()->GetImage(FlushReason::kTesting);
num_readbacks_++;
return GetPixels(Context2D(), CanvasElement().width(),
CanvasElement().height());
}
static base::span<uint8_t> GetPixels(BaseRenderingContext2D* context,
size_t width,
size_t height) {
NonThrowableExceptionState exception_state;
return context->getImageData(0, 0, width, height, exception_state)
->data()
->GetAsUint8ClampedArray()
->AsSpan();
}
static int GetNumChangedPixels(base::span<uint8_t> pixels_no_interventions,
base::span<uint8_t> pixels_with_interventions,
int max_channel_diff) {
EXPECT_EQ(pixels_with_interventions.size(), pixels_no_interventions.size());
int num_changed_pixel_values = 0;
int too_large_diffs = 0;
for (size_t i = 0; i < pixels_no_interventions.size(); ++i) {
int diff =
std::max(pixels_no_interventions[i], pixels_with_interventions[i]) -
std::min(pixels_no_interventions[i], pixels_with_interventions[i]);
if (diff > 0) {
++num_changed_pixel_values;
}
if (diff > max_channel_diff) {
++too_large_diffs;
}
}
EXPECT_EQ(too_large_diffs, 0);
return num_changed_pixel_values;
}
void ExpectInterventionHappened() {
NonThrowableExceptionState exception_state;
DisableInterventions();
String data_url_no_interventions =
CanvasElement().toDataURL("image/png", exception_state);
base::span<uint8_t> pixels_no_interventions = GetPixels(
Context2D(), CanvasElement().width(), CanvasElement().height());
EnableInterventions();
EXPECT_TRUE(Context2D()->HasTriggerForIntervention());
EXPECT_TRUE(Context2D()->ShouldTriggerIntervention());
String data_url_with_interventions =
CanvasElement().toDataURL("image/png", exception_state);
num_readbacks_++;
EXPECT_NE(data_url_no_interventions, data_url_with_interventions);
int num_changed_pixel_values =
GetNumChangedPixels(pixels_no_interventions,
GetPixels(Context2D(), CanvasElement().width(),
CanvasElement().height()),
/*max_channel_diff=*/3);
num_readbacks_++;
EXPECT_GT(num_changed_pixel_values, 0);
}
void ExpectInterventionDidNotHappen() {
NonThrowableExceptionState exception_state;
DisableInterventions();
String data_url_no_interventions =
CanvasElement().toDataURL("image/png", exception_state);
base::span<uint8_t> pixels_no_interventions = GetPixels(
Context2D(), CanvasElement().width(), CanvasElement().height());
EnableInterventions();
EXPECT_FALSE(Context2D()->HasTriggerForIntervention());
EXPECT_FALSE(Context2D()->ShouldTriggerIntervention());
String data_url_with_interventions =
CanvasElement().toDataURL("image/png", exception_state);
EXPECT_EQ(data_url_no_interventions, data_url_with_interventions);
EXPECT_EQ(pixels_no_interventions,
GetPixels(Context2D(), CanvasElement().width(),
CanvasElement().height()));
}
void DrawSomethingWithTrigger() {
Context2D()->setShadowBlur(10);
Context2D()->setShadowColor("red");
Context2D()->fillRect(0, 0, 10, 10);
}
int GetNumReadbacksHappened() { return num_readbacks_; }
int num_readbacks_ = 0;
ScopedTestingPlatformSupport<GpuMemoryBufferTestPlatform>
accelerated_compositing_scope_;
ScopedAccelerated2dCanvasForTest accelerated_canvas_enabled_scope_ = true;
scoped_refptr<viz::TestContextProvider> test_context_provider_;
std::unique_ptr<frame_test_helpers::WebViewHelper> web_view_helper_;
Persistent<HTMLCanvasElement> canvas_element_;
};
TEST_F(CanvasNoiseTest, MaybeNoiseSnapshotNoiseWhenCanvasInterventionsEnabled) {
base::HistogramTester histogram_tester;
auto* window = GetFrame().DomWindow();
// Enable CanvasInterventions.
window->GetRuntimeFeatureStateOverrideContext()
->SetCanvasInterventionsForceEnabled();
DrawSomethingWithTrigger();
scoped_refptr<StaticBitmapImage> snapshot =
Context2D()->GetImage(FlushReason::kTesting);
scoped_refptr<StaticBitmapImage> snapshot_copy = snapshot;
EXPECT_TRUE(CanvasInterventionsHelper::MaybeNoiseSnapshot(Context2D(), window,
snapshot));
num_readbacks_++;
histogram_tester.ExpectUniqueSample(
kNoiseReasonMetricName,
static_cast<int>(CanvasNoiseReason::kAllConditionsMet), 1);
histogram_tester.ExpectTotalCount(kNoiseDurationMetricName, 1);
histogram_tester.ExpectUniqueSample(
kCanvasSizeMetricName, CanvasElement().width() * CanvasElement().height(),
1);
EXPECT_NE(snapshot_copy, snapshot);
histogram_tester.ExpectUniqueSample(kCanvasOperationMetricName,
CanvasOperationType::kSetShadowBlur |
CanvasOperationType::kSetShadowColor,
GetNumReadbacksHappened());
histogram_tester.ExpectTotalCount(kCanvasOperationMetricName,
GetNumReadbacksHappened());
}
TEST_F(CanvasNoiseTest,
MaybeNoiseSnapshotDoesNotNoiseWhenCanvasInterventionsDisabled) {
base::HistogramTester histogram_tester;
auto* window = GetFrame().DomWindow();
// Disable CanvasInterventions.
window->GetRuntimeFeatureStateOverrideContext()
->SetCanvasInterventionsForceDisabled();
DrawSomethingWithTrigger();
scoped_refptr<StaticBitmapImage> snapshot =
Context2D()->GetImage(FlushReason::kTesting);
scoped_refptr<StaticBitmapImage> snapshot_copy = snapshot;
EXPECT_FALSE(CanvasInterventionsHelper::MaybeNoiseSnapshot(Context2D(),
window, snapshot));
histogram_tester.ExpectUniqueSample(
kNoiseReasonMetricName,
static_cast<int>(CanvasNoiseReason::kNotEnabledInMode), 1);
histogram_tester.ExpectTotalCount(kNoiseDurationMetricName, 0);
histogram_tester.ExpectTotalCount(kCanvasSizeMetricName, 0);
EXPECT_EQ(snapshot_copy, snapshot);
histogram_tester.ExpectTotalCount(kCanvasOperationMetricName, 0);
}
TEST_F(CanvasNoiseTest, MaybeNoiseSnapshotDoesNotNoiseForCpuCanvas) {
CanvasElement().DisableAcceleration();
base::HistogramTester histogram_tester;
auto* window = GetFrame().DomWindow();
// Enable CanvasInterventions.
window->GetRuntimeFeatureStateOverrideContext()
->SetCanvasInterventionsForceEnabled();
DrawSomethingWithTrigger();
scoped_refptr<StaticBitmapImage> snapshot =
Context2D()->GetImage(FlushReason::kTesting);
scoped_refptr<StaticBitmapImage> snapshot_copy = snapshot;
EXPECT_FALSE(CanvasInterventionsHelper::MaybeNoiseSnapshot(Context2D(),
window, snapshot));
histogram_tester.ExpectUniqueSample(
kNoiseReasonMetricName, static_cast<int>(CanvasNoiseReason::kNoGpu), 1);
histogram_tester.ExpectTotalCount(kNoiseDurationMetricName, 0);
histogram_tester.ExpectTotalCount(kCanvasSizeMetricName, 0);
EXPECT_EQ(snapshot_copy, snapshot);
histogram_tester.ExpectTotalCount(kCanvasOperationMetricName, 0);
}
TEST_F(CanvasNoiseTest, MaybeNoiseSnapshotDifferentNoiseTokenNoiseDiffers) {
base::HistogramTester histogram_tester;
NonThrowableExceptionState exception_state;
auto* window = GetFrame().DomWindow();
window->GetRuntimeFeatureStateOverrideContext()
->SetCanvasInterventionsForceEnabled();
DrawSomethingWithTrigger();
// Save a copy of the image data to reset.
base::span<uint8_t> original_noised_pixels = GetNoisedPixels(window);
// Sanity check to ensure GetNoisedPixels performs the same noising
// pattern without changing the noise token.
// This will still update the histogram.
EXPECT_EQ(original_noised_pixels, GetNoisedPixels(window));
// Now change the noise token.
CanvasNoiseToken::Set(0xdeadbeef);
base::span<uint8_t> updated_noised_pixels = GetNoisedPixels(window);
EXPECT_NE(original_noised_pixels, updated_noised_pixels);
histogram_tester.ExpectUniqueSample(kCanvasOperationMetricName,
CanvasOperationType::kSetShadowBlur |
CanvasOperationType::kSetShadowColor,
GetNumReadbacksHappened());
histogram_tester.ExpectTotalCount(kCanvasOperationMetricName,
GetNumReadbacksHappened());
}
TEST_F(CanvasNoiseTest, NoTriggerOnFillRect) {
base::HistogramTester tester;
V8TestingScope scope;
SetFillStyleString(Context2D(), GetScriptState(), "red");
Context2D()->fillRect(0, 0, 10, 10);
ExpectInterventionDidNotHappen();
tester.ExpectTotalCount(kCanvasOperationMetricName, 0);
}
TEST_F(CanvasNoiseTest, TriggerOnShadowBlur) {
base::HistogramTester tester;
Context2D()->setShadowBlur(10);
Context2D()->setShadowColor("red");
Context2D()->fillRect(0, 0, 10, 10);
// Two successful readbacks occur in this function, histograms should reflect
// this.
ExpectInterventionHappened();
tester.ExpectBucketCount(kCanvasOperationMetricName,
CanvasOperationType::kSetShadowBlur |
CanvasOperationType::kSetShadowColor,
GetNumReadbacksHappened());
tester.ExpectTotalCount(kCanvasOperationMetricName,
GetNumReadbacksHappened());
}
TEST_F(CanvasNoiseTest, TriggerOnArc) {
base::HistogramTester tester;
NonThrowableExceptionState exception_state;
Context2D()->beginPath();
Context2D()->arc(10, 10, 10, 0, 6, false, exception_state);
Context2D()->stroke();
ExpectInterventionHappened();
tester.ExpectBucketCount(kCanvasOperationMetricName,
CanvasOperationType::kArc,
GetNumReadbacksHappened());
tester.ExpectTotalCount(kCanvasOperationMetricName,
GetNumReadbacksHappened());
}
TEST_F(CanvasNoiseTest, TriggerOnEllipse) {
base::HistogramTester tester;
NonThrowableExceptionState exception_state;
Context2D()->beginPath();
Context2D()->ellipse(10, 10, 5, 7, 3, 0, 3, false, exception_state);
Context2D()->fill();
ExpectInterventionHappened();
tester.ExpectBucketCount(kCanvasOperationMetricName,
CanvasOperationType::kEllipse,
GetNumReadbacksHappened());
tester.ExpectTotalCount(kCanvasOperationMetricName,
GetNumReadbacksHappened());
}
TEST_F(CanvasNoiseTest, TriggerOnSetGlobalCompositeOperation) {
base::HistogramTester tester;
V8TestingScope scope;
Context2D()->setGlobalCompositeOperation("multiply");
SetFillStyleString(Context2D(), GetScriptState(), "red");
Context2D()->fillRect(0, 0, 10, 10);
ExpectInterventionHappened();
tester.ExpectBucketCount(kCanvasOperationMetricName,
CanvasOperationType::kGlobalCompositionOperation,
GetNumReadbacksHappened());
tester.ExpectTotalCount(kCanvasOperationMetricName,
GetNumReadbacksHappened());
}
TEST_F(CanvasNoiseTest, TriggerOnFillText) {
base::HistogramTester tester;
Context2D()->fillText("CanvasNoiseTest", 0, 0);
ExpectInterventionHappened();
tester.ExpectBucketCount(kCanvasOperationMetricName,
CanvasOperationType::kFillText,
GetNumReadbacksHappened());
tester.ExpectTotalCount(kCanvasOperationMetricName,
GetNumReadbacksHappened());
}
TEST_F(CanvasNoiseTest, TriggerOnStrokeText) {
base::HistogramTester tester;
Context2D()->strokeText("CanvasNoiseTest", 0, 0);
ExpectInterventionHappened();
tester.ExpectBucketCount(kCanvasOperationMetricName,
CanvasOperationType::kStrokeText,
GetNumReadbacksHappened());
tester.ExpectTotalCount(kCanvasOperationMetricName,
GetNumReadbacksHappened());
}
TEST_F(CanvasNoiseTest, TriggerOnFillWithPath2DNoNoise) {
base::HistogramTester histogram_tester;
V8TestingScope scope;
Path2D* canvas_path = Path2D::Create(GetScriptState());
canvas_path->lineTo(10, 10);
canvas_path->lineTo(15, 15);
canvas_path->closePath();
Context2D()->fill(canvas_path);
EXPECT_FALSE(canvas_path->HasTriggerForIntervention());
scoped_refptr<StaticBitmapImage> snapshot =
Context2D()->GetImage(FlushReason::kTesting);
scoped_refptr<StaticBitmapImage> snapshot_copy = snapshot;
EXPECT_FALSE(CanvasInterventionsHelper::MaybeNoiseSnapshot(
Context2D(), GetFrame().DomWindow(), snapshot));
histogram_tester.ExpectUniqueSample(
kNoiseReasonMetricName, static_cast<int>(CanvasNoiseReason::kNoTrigger),
1);
histogram_tester.ExpectTotalCount(kNoiseDurationMetricName, 0);
histogram_tester.ExpectTotalCount(kCanvasSizeMetricName, 0);
ExpectInterventionDidNotHappen();
histogram_tester.ExpectTotalCount(kCanvasOperationMetricName, 0);
}
TEST_F(CanvasNoiseTest, TriggerOnFillWithPath2DWithNoise) {
base::HistogramTester histogram_tester;
NonThrowableExceptionState exception_state;
V8TestingScope scope;
Path2D* canvas_path = Path2D::Create(GetScriptState());
canvas_path->lineTo(10, 10);
canvas_path->lineTo(15, 15);
canvas_path->closePath();
EXPECT_FALSE(canvas_path->HasTriggerForIntervention());
canvas_path->arc(10, 10, 10, 0, 6, false, exception_state);
EXPECT_TRUE(canvas_path->HasTriggerForIntervention());
ExpectInterventionDidNotHappen();
histogram_tester.ExpectTotalCount(kCanvasOperationMetricName, 0);
Context2D()->fill(canvas_path);
ExpectInterventionHappened();
histogram_tester.ExpectBucketCount(kCanvasOperationMetricName,
CanvasOperationType::kArc,
GetNumReadbacksHappened());
histogram_tester.ExpectTotalCount(kCanvasOperationMetricName,
GetNumReadbacksHappened());
}
TEST_F(CanvasNoiseTest, OffscreenCanvasNoise) {
base::HistogramTester histogram_tester;
V8TestingScope scope;
auto* host = OffscreenCanvas::Create(scope.GetScriptState(), 300, 300);
OffscreenCanvasRenderingContext2D* context =
static_cast<OffscreenCanvasRenderingContext2D*>(
host->GetCanvasRenderingContext(
scope.GetExecutionContext(),
CanvasRenderingContext::CanvasRenderingAPI::k2D,
CanvasContextCreationAttributesCore()));
context->fillText("CanvasNoiseTest", 0, 0);
EXPECT_TRUE(context->HasTriggerForIntervention());
EXPECT_TRUE(context->ShouldTriggerIntervention());
host->GetExecutionContext()
->GetRuntimeFeatureStateOverrideContext()
->SetCanvasInterventionsForceDisabled();
base::span<uint8_t> pixels_no_interventions =
GetPixels(context, host->width(), host->height());
host->GetExecutionContext()
->GetRuntimeFeatureStateOverrideContext()
->SetCanvasInterventionsForceEnabled();
int num_changed_pixel_values =
GetNumChangedPixels(pixels_no_interventions,
GetPixels(context, host->width(), host->height()),
/*max_channel_diff=*/3);
EXPECT_GT(num_changed_pixel_values, 0);
histogram_tester.ExpectUniqueSample(
kCanvasOperationMetricName,
static_cast<int>(CanvasOperationType::kFillText), 1);
histogram_tester.ExpectTotalCount(kCanvasOperationMetricName, 1);
}
TEST_F(CanvasNoiseTest, NoiseDiffersPerSite) {
base::HistogramTester histogram_tester;
Context2D()->fillText("CanvasNoiseTest", 0, 0);
base::span<uint8_t> pixels_test_site =
GetPixels(Context2D(), CanvasElement().width(), CanvasElement().height());
CanvasRenderingContext::GetCanvasPerformanceMonitor().ResetForTesting();
// Navigate to a different origin.
NavigateTo(KURL("https://different.example"));
// Need to re-enable after navigating.
EnableInterventions();
SetHtmlInnerHTML("<body><canvas id='c' width='300' height='300'></body>");
UpdateAllLifecyclePhasesForTest();
auto* diff_canvas_element = To<HTMLCanvasElement>(GetElementById("c"));
CanvasContextCreationAttributesCore attributes;
attributes.alpha = true;
attributes.desynchronized = true;
attributes.premultiplied_alpha = false;
attributes.will_read_frequently =
CanvasContextCreationAttributesCore::WillReadFrequently::kFalse;
auto* diff_context = static_cast<CanvasRenderingContext2D*>(
diff_canvas_element->GetCanvasRenderingContext(/*canvas_type=*/"2d",
attributes));
diff_context->fillText("CanvasNoiseTest", 0, 0);
// We're taking 2 canvases with different noise applied to them, so the max
// difference for per pixel value is 6 (= 2 * max noise per channel).
// Still need to figure out why the noise is higher than expected.
int num_changed_pixel_values =
GetNumChangedPixels(pixels_test_site,
GetPixels(diff_context, diff_canvas_element->width(),
diff_canvas_element->height()),
/*max_channel_diff=*/6);
EXPECT_GT(num_changed_pixel_values, 0);
histogram_tester.ExpectUniqueSample(
kCanvasOperationMetricName,
static_cast<int>(CanvasOperationType::kFillText), 2);
histogram_tester.ExpectTotalCount(kCanvasOperationMetricName, 2);
}
TEST_F(CanvasNoiseTest, NumberOfNoisedReadbackPerPage) {
base::HistogramTester histogram_tester;
NonThrowableExceptionState exception_state;
DrawSomethingWithTrigger();
CanvasElement().toDataURL("image/png", exception_state);
CanvasElement().toDataURL("image/jpeg", exception_state);
Context2D()->getImageData(0, 0, 10, 10, exception_state);
CanvasRenderingContext::GetCanvasPerformanceMonitor().ResetForTesting();
// Navigate away from page to destroy the execution context.
NavigateTo(KURL("https://different.example"));
histogram_tester.ExpectUniqueSample(
"FingerprintingProtection.CanvasNoise.NoisedReadbacksPerContext", 3, 1);
}
} // namespace blink
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