| <!DOCTYPE html> |
| <script src="../../../resources/testharness.js"></script> |
| <script src="../../../resources/testharnessreport.js"></script> |
| <script> |
| const canvasSize = 10; |
| |
| assertImageEmpty = async function (dataUrl) { |
| const readbackCanvas = document.createElement("canvas"); |
| const readbackCtx = readbackCanvas.getContext('2d'); |
| const img = new Image(); |
| img.src = dataUrl; |
| await img.decode(); |
| readbackCtx.drawImage(img, 0, 0); |
| imageData = readbackCtx.getImageData(0, 0, canvasSize, canvasSize); |
| assert_array_equals(imageData.data, |
| new Array(canvasSize * canvasSize * 4).fill(0), |
| "Expected image to be empty."); |
| }; |
| |
| promise_test(async t => { |
| const image = new Image(); |
| // Notice that we don't set the image.crossOrigin property. |
| image.src = "http://localhost:8000/security/resources/abe-allow-star.php"; |
| await image.decode(); |
| const canvas = document.createElement('canvas'); |
| canvas.width = canvas.height = canvasSize; |
| |
| const offscreen = canvas.transferControlToOffscreen(); |
| const ctx = offscreen.getContext('2d'); |
| ctx.drawImage(image, 0, 0); |
| |
| // Tests that the placerholder canvas is empty until the offscreen frame |
| // propagates and unreadable afterward. |
| readbackCanvas = async (reject) => { |
| (async () => { |
| // Should either throw if the frame propagated, or be an empty image. |
| const dataUrl = canvas.toDataURL(); |
| await assertImageEmpty(dataUrl); |
| })() |
| // Try again, until the frame propagates and `toDataURL` throws. |
| .then(() => requestAnimationFrame(() => readbackCanvas(reject))) |
| .catch(reject); |
| }; |
| |
| // Succeeds when `toDataURL` throws. The test will fail with a timeout if it |
| // never happens. |
| await promise_rejects_dom(t, 'SecurityError', |
| // Create a promise whose `reject` handler will be called asynchronously, |
| // now or in any future animation frames. |
| new Promise((_, reject) => readbackCanvas(reject))); |
| |
| }, "Verify that the placeholder <canvas> associated with an OffscreenCanvas tainted with cross-origin content cannot be read once commit has propagated."); |
| |
| </script> |
