Bug 1746750 - Part 2. Add new WebIDL method variants to support OffscreenCanvasRenderingContext2D. r=lsalzman

This patch is a non-functional change. It overloads some WebIDL methods
of CanvasRenderingContext2D to account for the difference between the
main thread and worker prototypes.

Differential Revision: https://phabricator.services.mozilla.com/D135353

dom/canvas/CanvasRenderingContext2D.cpp

@@ -4271,6 +4271,12 @@ bool CanvasRenderingContext2D::IsPointInPath(JSContext* aCx, double aX,
                                              double aY,
                                              const CanvasWindingRule& aWinding,
                                              nsIPrincipal& aSubjectPrincipal) {
+  return IsPointInPath(aCx, aX, aY, aWinding, Some(&aSubjectPrincipal));
+}
+
+bool CanvasRenderingContext2D::IsPointInPath(
+    JSContext* aCx, double aX, double aY, const CanvasWindingRule& aWinding,
+    Maybe<nsIPrincipal*> aSubjectPrincipal) {
   if (!FloatValidate(aX, aY)) {
     return false;
   }
@@ -4282,6 +4288,9 @@ bool CanvasRenderingContext2D::IsPointInPath(JSContext* aCx, double aX,
                                                aSubjectPrincipal)) {
       return false;
     }
+  } else if (mOffscreenCanvas &&
+             mOffscreenCanvas->ShouldResistFingerprinting()) {
+    return false;
   }
 
   EnsureUserSpacePath(aWinding);
@@ -4300,7 +4309,15 @@ bool CanvasRenderingContext2D::IsPointInPath(JSContext* aCx,
                                              const CanvasPath& aPath, double aX,
                                              double aY,
                                              const CanvasWindingRule& aWinding,
-                                             nsIPrincipal&) {
+                                             nsIPrincipal& aSubjectPrincipal) {
+  return IsPointInPath(aCx, aPath, aX, aY, aWinding, Some(&aSubjectPrincipal));
+}
+
+bool CanvasRenderingContext2D::IsPointInPath(JSContext* aCx,
+                                             const CanvasPath& aPath, double aX,
+                                             double aY,
+                                             const CanvasWindingRule& aWinding,
+                                             Maybe<nsIPrincipal*>) {
   if (!FloatValidate(aX, aY)) {
     return false;
   }
@@ -4317,6 +4334,12 @@ bool CanvasRenderingContext2D::IsPointInPath(JSContext* aCx,
 
 bool CanvasRenderingContext2D::IsPointInStroke(
     JSContext* aCx, double aX, double aY, nsIPrincipal& aSubjectPrincipal) {
+  return IsPointInStroke(aCx, aX, aY, Some(&aSubjectPrincipal));
+}
+
+bool CanvasRenderingContext2D::IsPointInStroke(
+    JSContext* aCx, double aX, double aY,
+    Maybe<nsIPrincipal*> aSubjectPrincipal) {
   if (!FloatValidate(aX, aY)) {
     return false;
   }
@@ -4328,6 +4351,9 @@ bool CanvasRenderingContext2D::IsPointInStroke(
                                                aSubjectPrincipal)) {
       return false;
     }
+  } else if (mOffscreenCanvas &&
+             mOffscreenCanvas->ShouldResistFingerprinting()) {
+    return false;
   }
 
   EnsureUserSpacePath();
@@ -4348,10 +4374,16 @@ bool CanvasRenderingContext2D::IsPointInStroke(
                                     mTarget->GetTransform());
 }
 
+bool CanvasRenderingContext2D::IsPointInStroke(
+    JSContext* aCx, const CanvasPath& aPath, double aX, double aY,
+    nsIPrincipal& aSubjectPrincipal) {
+  return IsPointInStroke(aCx, aPath, aX, aY, Some(&aSubjectPrincipal));
+}
+
 bool CanvasRenderingContext2D::IsPointInStroke(JSContext* aCx,
                                                const CanvasPath& aPath,
                                                double aX, double aY,
-                                               nsIPrincipal&) {
+                                               Maybe<nsIPrincipal*>) {
   if (!FloatValidate(aX, aY)) {
     return false;
   }
@@ -5050,7 +5082,14 @@ void CanvasRenderingContext2D::DrawWindow(nsGlobalWindowInner& aWindow,
 already_AddRefed<ImageData> CanvasRenderingContext2D::GetImageData(
     JSContext* aCx, int32_t aSx, int32_t aSy, int32_t aSw, int32_t aSh,
     nsIPrincipal& aSubjectPrincipal, ErrorResult& aError) {
-  if (!mCanvasElement && !mDocShell) {
+  return GetImageData(aCx, aSx, aSy, aSw, aSh, Some(&aSubjectPrincipal),
+                      aError);
+}
+
+already_AddRefed<ImageData> CanvasRenderingContext2D::GetImageData(
+    JSContext* aCx, int32_t aSx, int32_t aSy, int32_t aSw, int32_t aSh,
+    Maybe<nsIPrincipal*> aSubjectPrincipal, ErrorResult& aError) {
+  if (!mCanvasElement && !mDocShell && !mOffscreenCanvas) {
     NS_ERROR("No canvas element and no docshell in GetImageData!!!");
     aError.Throw(NS_ERROR_DOM_SECURITY_ERR);
     return nullptr;
@@ -5058,6 +5097,7 @@ already_AddRefed<ImageData> CanvasRenderingContext2D::GetImageData(
 
   // Check only if we have a canvas element; if we were created with a docshell,
   // then it's special internal use.
+  // FIXME(aosmond): OffscreenCanvas security check??!
   if (IsWriteOnly() ||
       (mCanvasElement && !mCanvasElement->CallerCanRead(aCx))) {
     // XXX ERRMSG we need to report an error to developers here! (bug 329026)
@@ -5105,7 +5145,7 @@ already_AddRefed<ImageData> CanvasRenderingContext2D::GetImageData(
 
 nsresult CanvasRenderingContext2D::GetImageDataArray(
     JSContext* aCx, int32_t aX, int32_t aY, uint32_t aWidth, uint32_t aHeight,
-    nsIPrincipal& aSubjectPrincipal, JSObject** aRetval) {
+    Maybe<nsIPrincipal*> aSubjectPrincipal, JSObject** aRetval) {
   MOZ_ASSERT(aWidth && aHeight);
 
   // Restrict the typed array length to INT32_MAX because that's all we support
@@ -5170,6 +5210,8 @@ nsresult CanvasRenderingContext2D::GetImageDataArray(
     nsCOMPtr<Document> ownerDoc = mCanvasElement->OwnerDoc();
     usePlaceholder = !CanvasUtils::IsImageExtractionAllowed(ownerDoc, aCx,
                                                             aSubjectPrincipal);
+  } else if (mOffscreenCanvas) {
+    usePlaceholder = mOffscreenCanvas->ShouldResistFingerprinting();
   }
 
   do {

dom/canvas/CanvasRenderingContext2D.h

@@ -15,6 +15,7 @@
 #include "mozilla/Atomics.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/EnumeratedArray.h"
+#include "mozilla/Maybe.h"
 #include "mozilla/RefPtr.h"
 #include "mozilla/SurfaceFromElementResult.h"
 #include "mozilla/UniquePtr.h"
@@ -208,13 +209,23 @@ class CanvasRenderingContext2D : public nsICanvasRenderingContextInternal,
   bool IsPointInPath(JSContext* aCx, double aX, double aY,
                      const CanvasWindingRule& aWinding,
                      nsIPrincipal& aSubjectPrincipal);
+  bool IsPointInPath(JSContext* aCx, double aX, double aY,
+                     const CanvasWindingRule& aWinding,
+                     Maybe<nsIPrincipal*> aSubjectPrincipal);
   bool IsPointInPath(JSContext* aCx, const CanvasPath& aPath, double aX,
                      double aY, const CanvasWindingRule& aWinding,
                      nsIPrincipal&);
+  bool IsPointInPath(JSContext* aCx, const CanvasPath& aPath, double aX,
+                     double aY, const CanvasWindingRule& aWinding,
+                     Maybe<nsIPrincipal*>);
   bool IsPointInStroke(JSContext* aCx, double aX, double aY,
                        nsIPrincipal& aSubjectPrincipal);
+  bool IsPointInStroke(JSContext* aCx, double aX, double aY,
+                       Maybe<nsIPrincipal*> aSubjectPrincipal);
   bool IsPointInStroke(JSContext* aCx, const CanvasPath& aPath, double aX,
                        double aY, nsIPrincipal&);
+  bool IsPointInStroke(JSContext* aCx, const CanvasPath& aPath, double aX,
+                       double aY, Maybe<nsIPrincipal*>);
   void FillText(const nsAString& aText, double aX, double aY,
                 const Optional<double>& aMaxWidth,
                 mozilla::ErrorResult& aError);
@@ -254,6 +265,9 @@ class CanvasRenderingContext2D : public nsICanvasRenderingContextInternal,
                                            int32_t aSw, int32_t aSh,
                                            nsIPrincipal& aSubjectPrincipal,
                                            ErrorResult&);
+  already_AddRefed<ImageData> GetImageData(
+      JSContext*, int32_t aSx, int32_t aSy, int32_t aSw, int32_t aSh,
+      Maybe<nsIPrincipal*> aSubjectPrincipal, ErrorResult&);
   void PutImageData(ImageData&, int32_t aDx, int32_t aDy, ErrorResult&);
   void PutImageData(ImageData&, int32_t aDx, int32_t aDy, int32_t aDirtyX,
                     int32_t aDirtyY, int32_t aDirtyWidth, int32_t aDirtyHeight,
@@ -516,7 +530,7 @@ class CanvasRenderingContext2D : public nsICanvasRenderingContextInternal,
  protected:
   nsresult GetImageDataArray(JSContext* aCx, int32_t aX, int32_t aY,
                              uint32_t aWidth, uint32_t aHeight,
-                             nsIPrincipal& aSubjectPrincipal,
+                             Maybe<nsIPrincipal*> aSubjectPrincipal,
                              JSObject** aRetval);
 
   void PutImageData_explicit(int32_t aX, int32_t aY, ImageData&,

dom/canvas/CanvasUtils.cpp

@@ -51,24 +51,26 @@ using namespace mozilla::gfx;
 namespace mozilla::CanvasUtils {
 
 bool IsImageExtractionAllowed(dom::Document* aDocument, JSContext* aCx,
-                              nsIPrincipal& aPrincipal) {
+                              Maybe<nsIPrincipal*> aPrincipal) {
   // Do the rest of the checks only if privacy.resistFingerprinting is on.
   if (!nsContentUtils::ShouldResistFingerprinting(aDocument)) {
     return true;
   }
 
   // Don't proceed if we don't have a document or JavaScript context.
-  if (!aDocument || !aCx) {
+  if (!aDocument || !aCx || !aPrincipal) {
     return false;
   }
 
+  nsIPrincipal& subjectPrincipal = *aPrincipal.ref();
+
   // The system principal can always extract canvas data.
-  if (aPrincipal.IsSystemPrincipal()) {
+  if (subjectPrincipal.IsSystemPrincipal()) {
     return true;
   }
 
   // Allow extension principals.
-  auto principal = BasePrincipal::Cast(&aPrincipal);
+  auto* principal = BasePrincipal::Cast(&subjectPrincipal);
   if (principal->AddonPolicy() || principal->ContentScriptAddonPolicy()) {
     return true;
   }

dom/canvas/CanvasUtils.h

@@ -56,7 +56,7 @@ bool IsOffscreenCanvasEnabled(JSContext* aCx, JSObject* aObj);
 
 // Check site-specific permission and display prompt if appropriate.
 bool IsImageExtractionAllowed(dom::Document* aDocument, JSContext* aCx,
-                              nsIPrincipal& aPrincipal);
+                              Maybe<nsIPrincipal*> aPrincipal);
 
 // Make a double out of |v|, treating undefined values as 0.0 (for
 // the sake of sparse arrays).  Return true iff coercion

dom/html/HTMLCanvasElement.cpp

@@ -800,7 +800,8 @@ already_AddRefed<CanvasCaptureMediaStream> HTMLCanvasElement::CaptureStream(
   // If no permission, arrange for the frame capture listener to return
   // all-white, opaque image data.
   bool usePlaceholder = !CanvasUtils::IsImageExtractionAllowed(
-      OwnerDoc(), nsContentUtils::GetCurrentJSContext(), aSubjectPrincipal);
+      OwnerDoc(), nsContentUtils::GetCurrentJSContext(),
+      Some(&aSubjectPrincipal));
 
   rv = RegisterFrameCaptureListener(stream->FrameCaptureListener(),
                                     usePlaceholder);
@@ -820,7 +821,7 @@ nsresult HTMLCanvasElement::ExtractData(JSContext* aCx,
   // Check site-specific permission and display prompt if appropriate.
   // If no permission, return all-white, opaque image data.
   bool usePlaceholder = !CanvasUtils::IsImageExtractionAllowed(
-      OwnerDoc(), aCx, aSubjectPrincipal);
+      OwnerDoc(), aCx, Some(&aSubjectPrincipal));
   return ImageEncoder::ExtractData(aType, aOptions, GetSize(), usePlaceholder,
                                    mCurrentContext, mCanvasRenderer, aStream);
 }
@@ -904,7 +905,7 @@ void HTMLCanvasElement::ToBlob(JSContext* aCx, BlobCallback& aCallback,
   // Check site-specific permission and display prompt if appropriate.
   // If no permission, return all-white, opaque image data.
   bool usePlaceholder = !CanvasUtils::IsImageExtractionAllowed(
-      OwnerDoc(), aCx, aSubjectPrincipal);
+      OwnerDoc(), aCx, Some(&aSubjectPrincipal));
   CanvasRenderingContextHelper::ToBlob(aCx, global, aCallback, aType, aParams,
                                        usePlaceholder, aRv);
 }