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canvas: Apply large size limitations (#36445)

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To prevent any potential crash/OOM issues with "canvas" element
from "rogue" applications let's apply large size limitations for context
canvas2d's draw target to Servo (similar approach in Firefox/Chromium -
they limits width and height to 32767/65535 pixels).

Fixes: #36155, #34117, #30164, #24710

--
- [x] ./mach build -d does not report any errors
- [x] ./mach test-tidy does not report any errors
- [x] There are tests for these changes

tests/wpt/tests/html/canvas/element/canvas-host/2d.canvas.host.size.large.html

tests/wpt/tests/html/canvas/offscreen/canvas-host/2d.canvas.host.size.large.html

tests/wpt/tests/html/canvas/offscreen/canvas-host/2d.canvas.host.size.large.worker.js

Signed-off-by: Andrei Volykhin <andrei.volykhin@gmail.com>
This commit is contained in:
Andrei Volykhin 2025-04-29 16:48:30 +03:00 • committed by GitHub
parent bd6928f3dc
commit 6b2a755736
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GPG key ID: B5690EEEBB952194
7 changed files with 87 additions and 53 deletions
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87
components/script/canvas_state.rs
View file

@ -152,6 +152,8 @@ pub(crate) struct CanvasState {
canvas_id: CanvasId,
#[no_trace]
image_key: ImageKey,
#[no_trace]
size: Cell<Size2D<u64>>,
state: DomRefCell<CanvasContextState>,
origin_clean: Cell<bool>,
#[ignore_malloc_size_of = "Arc"]
@ -176,6 +178,7 @@ impl CanvasState {
profiled_ipc::channel(global.time_profiler_chan().clone()).unwrap();
let script_to_constellation_chan = global.script_to_constellation_chan();
debug!("Asking constellation to create new canvas thread.");
let size = adjust_canvas_size(size);
script_to_constellation_chan
.send(ScriptToConstellationMessage::CreateCanvasPaintThread(
size, sender,
@ -194,6 +197,7 @@ impl CanvasState {
CanvasState {
ipc_renderer,
canvas_id,
size: Cell::new(size),
state: DomRefCell::new(CanvasContextState::new()),
origin_clean: Cell::new(true),
image_cache: global.image_cache(),
@ -221,7 +225,15 @@ impl CanvasState {
self.canvas_id
}
pub(crate) fn is_paintable(&self) -> bool {
!self.size.get().is_empty()
}
pub(crate) fn send_canvas_2d_msg(&self, msg: Canvas2dMsg) {
if !self.is_paintable() {
return;
}
self.ipc_renderer
.send(CanvasMsg::Canvas2d(msg, self.get_canvas_id()))
.unwrap()
@ -229,6 +241,10 @@ impl CanvasState {
/// Updates WR image and blocks on completion
pub(crate) fn update_rendering(&self) {
if !self.is_paintable() {
return;
}
let (sender, receiver) = ipc::channel().unwrap();
self.ipc_renderer
.send(CanvasMsg::Canvas2d(
@ -239,16 +255,27 @@ impl CanvasState {
receiver.recv().unwrap();
}
// https://html.spec.whatwg.org/multipage/#concept-canvas-set-bitmap-dimensions
/// <https://html.spec.whatwg.org/multipage/#concept-canvas-set-bitmap-dimensions>
pub(crate) fn set_bitmap_dimensions(&self, size: Size2D<u64>) {
self.reset_to_initial_state();
self.size.replace(adjust_canvas_size(size));
self.ipc_renderer
.send(CanvasMsg::Recreate(Some(size), self.get_canvas_id()))
.send(CanvasMsg::Recreate(
Some(self.size.get()),
self.get_canvas_id(),
))
.unwrap();
}
pub(crate) fn reset(&self) {
self.reset_to_initial_state();
if !self.is_paintable() {
return;
}
self.ipc_renderer
.send(CanvasMsg::Recreate(None, self.get_canvas_id()))
.unwrap();
@ -347,7 +374,6 @@ impl CanvasState {
pub(crate) fn get_rect(&self, canvas_size: Size2D<u64>, rect: Rect<u64>) -> Vec<u8> {
assert!(self.origin_is_clean());
assert!(Rect::from_size(canvas_size).contains_rect(&rect));
let (sender, receiver) = ipc::channel().unwrap();
@ -398,18 +424,22 @@ impl CanvasState {
dw: Option<f64>,
dh: Option<f64>,
) -> ErrorResult {
if !self.is_paintable() {
return Ok(());
}
let result = match image {
CanvasImageSource::HTMLCanvasElement(ref canvas) => {
// https://html.spec.whatwg.org/multipage/#check-the-usability-of-the-image-argument
if !canvas.is_valid() {
// <https://html.spec.whatwg.org/multipage/#check-the-usability-of-the-image-argument>
if canvas.get_size().is_empty() {
return Err(Error::InvalidState);
}
self.draw_html_canvas_element(canvas, htmlcanvas, sx, sy, sw, sh, dx, dy, dw, dh)
},
CanvasImageSource::OffscreenCanvas(ref canvas) => {
// https://html.spec.whatwg.org/multipage/#check-the-usability-of-the-image-argument
if !canvas.is_valid() {
// <https://html.spec.whatwg.org/multipage/#check-the-usability-of-the-image-argument>
if canvas.get_size().is_empty() {
return Err(Error::InvalidState);
}
@ -528,11 +558,6 @@ impl CanvasState {
dw: Option<f64>,
dh: Option<f64>,
) -> ErrorResult {
// 1. Check the usability of the image argument
if !canvas.is_valid() {
return Err(Error::InvalidState);
}
let canvas_size = canvas.get_size();
let dw = dw.unwrap_or(canvas_size.width as f64);
let dh = dh.unwrap_or(canvas_size.height as f64);
@ -1403,13 +1428,13 @@ impl CanvasState {
},
};
ImageData::new(
global,
size.width,
size.height,
Some(self.get_rect(canvas_size, read_rect)),
can_gc,
)
let data = if self.is_paintable() {
Some(self.get_rect(canvas_size, read_rect))
} else {
None
};
ImageData::new(global, size.width, size.height, data, can_gc)
}
// https://html.spec.whatwg.org/multipage/#dom-context-2d-putimagedata
@ -1445,6 +1470,10 @@ impl CanvasState {
dirty_width: i32,
dirty_height: i32,
) {
if !self.is_paintable() {
return;
}
// FIXME(nox): There are many arithmetic operations here that can
// overflow or underflow, this should probably be audited.
@ -2013,3 +2042,23 @@ where
style.font_family.to_css_string()
)
}
fn adjust_canvas_size(size: Size2D<u64>) -> Size2D<u64> {
// Firefox limits width/height to 32767 pixels and Chromium to 65535 pixels,
// but slows down dramatically before it reaches that limit.
// We limit by area instead, giving us larger maximum dimensions,
// in exchange for a smaller maximum canvas size.
const MAX_CANVAS_AREA: u64 = 32768 * 8192;
// Max width/height to 65535 in CSS pixels.
const MAX_CANVAS_SIZE: u64 = 65535;
if !size.is_empty() &&
size.greater_than(Size2D::new(MAX_CANVAS_SIZE, MAX_CANVAS_SIZE))
.none() &&
size.area() < MAX_CANVAS_AREA
{
size
} else {
Size2D::zero()
}
}

36
components/script/dom/canvasrenderingcontext2d.rs
View file

@ -4,7 +4,7 @@
use canvas_traits::canvas::{Canvas2dMsg, CanvasId, CanvasMsg, FromScriptMsg};
use dom_struct::dom_struct;
use euclid::default::{Point2D, Rect, Size2D};
use euclid::default::Size2D;
use profile_traits::ipc;
use script_bindings::inheritance::Castable;
use script_layout_interface::HTMLCanvasDataSource;
@ -74,23 +74,12 @@ impl CanvasRenderingContext2D {
reflect_dom_object(boxed, global, can_gc)
}
// https://html.spec.whatwg.org/multipage/#concept-canvas-set-bitmap-dimensions
pub(crate) fn set_bitmap_dimensions(&self, size: Size2D<u32>) {
self.reset_to_initial_state();
self.canvas_state
.get_ipc_renderer()
.send(CanvasMsg::Recreate(
Some(size.to_u64()),
self.canvas_state.get_canvas_id(),
))
.unwrap();
}
// https://html.spec.whatwg.org/multipage/#reset-the-rendering-context-to-its-default-state
fn reset_to_initial_state(&self) {
self.canvas_state.reset_to_initial_state();
}
/// <https://html.spec.whatwg.org/multipage/#concept-canvas-set-bitmap-dimensions>
pub(crate) fn set_canvas_bitmap_dimensions(&self, size: Size2D<u64>) {
self.canvas_state.set_bitmap_dimensions(size);
}
@ -106,20 +95,17 @@ impl CanvasRenderingContext2D {
pub(crate) fn send_canvas_2d_msg(&self, msg: Canvas2dMsg) {
self.canvas_state.send_canvas_2d_msg(msg)
}
pub(crate) fn get_rect(&self, rect: Rect<u32>) -> Vec<u8> {
let rect = Rect::new(
Point2D::new(rect.origin.x as u64, rect.origin.y as u64),
Size2D::new(rect.size.width as u64, rect.size.height as u64),
);
self.canvas_state.get_rect(self.canvas.size(), rect)
}
}
impl LayoutCanvasRenderingContextHelpers for LayoutDom<'_, CanvasRenderingContext2D> {
fn canvas_data_source(self) -> HTMLCanvasDataSource {
let canvas_state = &self.unsafe_get().canvas_state;
HTMLCanvasDataSource::Image(canvas_state.image_key())
if canvas_state.is_paintable() {
HTMLCanvasDataSource::Image(canvas_state.image_key())
} else {
HTMLCanvasDataSource::Empty
}
}
}
@ -139,13 +125,11 @@ impl CanvasContext for CanvasRenderingContext2D {
}
fn resize(&self) {
self.set_bitmap_dimensions(self.size().cast())
self.set_canvas_bitmap_dimensions(self.size().cast())
}
fn get_image_data(&self) -> Option<Snapshot> {
let size = self.size();
if size.is_empty() {
if !self.canvas_state.is_paintable() {
return None;
}

2
components/script/dom/offscreencanvasrenderingcontext2d.rs
View file

@ -65,7 +65,7 @@ impl OffscreenCanvasRenderingContext2D {
}
pub(crate) fn set_canvas_bitmap_dimensions(&self, size: Size2D<u64>) {
self.context.set_bitmap_dimensions(size.cast());
self.context.set_canvas_bitmap_dimensions(size.cast());
}
pub(crate) fn send_canvas_2d_msg(&self, msg: Canvas2dMsg) {