security-and-privacy/CanvasBlocker
security-and-privacy/CanvasBlocker
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Improved input faking performance further

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fixes #517
This commit is contained in:
kkapsner 2021-01-13 20:06:03 +01:00
parent 1f1d7052a1
commit 945c2716c9
2 changed files with 13 additions and 8 deletions
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17
lib/modifiedCanvasAPI.js
View File

@ -227,24 +227,25 @@
notify("fakedInput"); notify("fakedInput");
let oldImageData; let oldImageData;
let x, y, width, height; let x, y, width, height;
const getImageData = window.CanvasRenderingContext2D.prototype.getImageData;
const border = 4; const border = 4;
try { try {
// "this" is not trustable - it may be not a context // "this" is not trustable - it may be not a context
const measurement = window.CanvasRenderingContext2D.prototype.measureText.call(this, args[0]); const measurement = window.CanvasRenderingContext2D.prototype.measureText.call(this, args[0]);
width = Math.ceil(measurement.actualBoundingBoxRight + measurement.actualBoundingBoxLeft) + border; const left = Math.max(0, measurement.actualBoundingBoxLeft);
height = Math.ceil(measurement.actualBoundingBoxDescent + measurement.actualBoundingBoxAscent) + border; const top = Math.max(0, measurement.actualBoundingBoxAscent);
x = Math.max(0, args[1] - width); width = Math.ceil(measurement.actualBoundingBoxRight + left) + 2 * border;
y = Math.max(0, args[2] - height); height = Math.ceil(measurement.actualBoundingBoxDescent + top) + 2 * border;
width = Math.min(3 * width, this.canvas.width - x); x = args[1] - border - left;
height = Math.min(3 * height, this.canvas.height - y); y = args[2] - border - top;
oldImageData = window.CanvasRenderingContext2D.prototype.getImageData.call(this, x, y, width, height); oldImageData = getImageData.call(this, x, y, width, height);
} }
catch (error){ catch (error){
// nothing to do here // nothing to do here
} }
// if "this" is not a correct context the next line will throw an error // if "this" is not a correct context the next line will throw an error
const ret = original.call(this, ...args); const ret = original.call(this, ...args);
const newImageData = window.CanvasRenderingContext2D.prototype.getImageData.call(this, x, y, width, height); const newImageData = getImageData.call(this, x, y, width, height);
this.putImageData(randomMixImageData(window, oldImageData, newImageData), x, y); this.putImageData(randomMixImageData(window, oldImageData, newImageData), x, y);
return ret; return ret;
} }

4
versions/updates.json
View File

@ -161,6 +161,10 @@
{ {
"version": "1.5Alpha20210104", "version": "1.5Alpha20210104",
"update_link": "https://canvasblocker.kkapsner.de/versions/canvasblocker_beta-1.5Alpha20210104-an+fx.xpi" "update_link": "https://canvasblocker.kkapsner.de/versions/canvasblocker_beta-1.5Alpha20210104-an+fx.xpi"
},
{
"version": "1.5Alpha20210112",
"update_link": "https://canvasblocker.kkapsner.de/versions/canvasblocker_beta-1.5Alpha20210112-an+fx.xpi"
} }
] ]
} }