security-and-privacy/CanvasBlocker
security-and-privacy/CanvasBlocker
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Prevented error when wrong object is passed to the faked functions.

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Solves the fourth problem in #114.
This commit is contained in:
kkapsner 2017-05-05 09:18:11 +02:00
parent 231e33ffb7
commit a9c7d97708
3 changed files with 60 additions and 45 deletions
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2
lib/intercept.js
View File

@ -73,7 +73,7 @@
setRandomSupplyByType(prefs("rng")); setRandomSupplyByType(prefs("rng"));
var fake = changedFunction.fakeGenerator(prefs, function(messageId){ var fake = changedFunction.fakeGenerator(prefs, function(messageId){
notify({url, errorStack: error.stack, messageId}); notify({url, errorStack: error.stack, messageId});
}, original); }, window, original);
switch (fake){ switch (fake){
case true: case true:
return original; return original;

100
lib/modifiedAPI.js
View File

@ -44,19 +44,25 @@
} }
function getFakeCanvas(window, original){ function getFakeCanvas(window, original){
var context = getContext(window, original); try {
var {imageData, source} = getImageData(window, context); // original may not be a canvas -> we must not leak an error
var desc = imageData.data; var context = getContext(window, original);
var l = desc.length; var {imageData, source} = getImageData(window, context);
var rng = randomSupply.getRng(l, window); var desc = imageData.data;
var l = desc.length;
var rng = randomSupply.getRng(l, window);
for (var i = 0; i < l; i += 1){ for (var i = 0; i < l; i += 1){
desc[i] = rng(source[i], i); desc[i] = rng(source[i], i);
}
var canvas = original.cloneNode(true);
context = window.HTMLCanvasElement.prototype.getContext.call(canvas, "2d");
context.putImageData(imageData, 0, 0);
return canvas;
}
catch (e){
return original;
} }
var canvas = original.cloneNode(true);
context = window.HTMLCanvasElement.prototype.getContext.call(canvas, "2d");
context.putImageData(imageData, 0, 0);
return canvas;
} }
function randomMixImageData(window, imageData1, imageData2){ function randomMixImageData(window, imageData1, imageData2){
var data1 = imageData1.data; var data1 = imageData1.data;
@ -77,9 +83,6 @@
return imageData2; return imageData2;
} }
function getWindow(canvas){
return canvas.ownerDocument.defaultView;
}
function hasType(status, type){ function hasType(status, type){
return status.type.indexOf(type) !== -1; return status.type.indexOf(type) !== -1;
} }
@ -114,11 +117,10 @@
} }
}, },
object: "HTMLCanvasElement", object: "HTMLCanvasElement",
fakeGenerator: function(prefs, notify){ fakeGenerator: function(prefs, notify, window, original){
return function(context, contextAttributes){ return function(context, contextAttributes){
var window = getWindow(this);
canvasContextType.set(this, context); canvasContextType.set(this, context);
return window.HTMLCanvasElement.prototype.getContext.apply(this, arguments); return original.apply(this, window.Array.from(arguments));
}; };
} }
}, },
@ -136,11 +138,10 @@
return status; return status;
}, },
object: "HTMLCanvasElement", object: "HTMLCanvasElement",
fakeGenerator: function(prefs, notify){ fakeGenerator: function(prefs, notify, window, original){
return function toDataURL(){ return function toDataURL(){
notify("fakedReadout"); notify("fakedReadout");
var window = getWindow(this); return original.apply(getFakeCanvas(window, this), window.Array.from(arguments));
return window.HTMLCanvasElement.prototype.toDataURL.apply(getFakeCanvas(window, this), arguments);
}; };
} }
}, },
@ -158,11 +159,10 @@
return status; return status;
}, },
object: "HTMLCanvasElement", object: "HTMLCanvasElement",
fakeGenerator: function(prefs, notify){ fakeGenerator: function(prefs, notify, window, original){
return function toBlob(callback){ return function toBlob(callback){
notify("fakedReadout"); notify("fakedReadout");
var window = getWindow(this); return original.apply(getFakeCanvas(window, this), window.Array.from(arguments));
return window.HTMLCanvasElement.prototype.toBlob.apply(getFakeCanvas(window, this), arguments);
}; };
}, },
exportOptions: {allowCallbacks: true} exportOptions: {allowCallbacks: true}
@ -181,11 +181,10 @@
return status; return status;
}, },
object: "HTMLCanvasElement", object: "HTMLCanvasElement",
fakeGenerator: function(prefs, notify){ fakeGenerator: function(prefs, notify, window, original){
return function mozGetAsFile(callback){ return function mozGetAsFile(callback){
notify("fakedReadout"); notify("fakedReadout");
var window = getWindow(this); return original.apply(getFakeCanvas(window, this), window.Array.from(arguments));
return window.HTMLCanvasElement.prototype.mozGetAsFile.apply(getFakeCanvas(window, this), arguments);
}; };
} }
}, },
@ -203,19 +202,25 @@
return status; return status;
}, },
object: "CanvasRenderingContext2D", object: "CanvasRenderingContext2D",
fakeGenerator: function(prefs, notify, original){ fakeGenerator: function(prefs, notify, window, original){
var maxSize = prefs("maxFakeSize") || Number.POSITIVE_INFINITY; var maxSize = prefs("maxFakeSize") || Number.POSITIVE_INFINITY;
return function getImageData(sx, sy, sw, sh){ return function getImageData(sx, sy, sw, sh){
var window = getWindow(this.canvas);
if (sw * sh > maxSize){ if (sw * sh > maxSize){
return original.apply(this, window.Array.from(arguments)); return original.apply(this, window.Array.from(arguments));
} }
else { else {
notify("fakedReadout"); notify("fakedReadout");
var context = window.HTMLCanvasElement.prototype.getContext.call( var fakeCanvas;
getFakeCanvas(window, this.canvas), var context = this;
"2d" if (this && this.canvas) {
); fakeCanvas = getFakeCanvas(window, this.canvas);
}
if (fakeCanvas && fakeCanvas !== this.canvas){
context = window.HTMLCanvasElement.prototype.getContext.call(
getFakeCanvas(window, this.canvas),
"2d"
);
}
return original.apply(context, window.Array.from(arguments)); return original.apply(context, window.Array.from(arguments));
} }
}; };
@ -229,12 +234,17 @@
return status; return status;
}, },
object: "CanvasRenderingContext2D", object: "CanvasRenderingContext2D",
fakeGenerator: function(prefs, notify){ fakeGenerator: function(prefs, notify, window, original){
return function fillText(str, x, y){ return function fillText(str, x, y){
notify("fakedInput"); notify("fakedInput");
var window = getWindow(this.canvas); var oldImageData;
var oldImageData = getImageData(window, this).imageData; try {
var ret = window.CanvasRenderingContext2D.prototype.fillText.apply(this, arguments); // "this" is not trustable - it may be not a context
oldImageData = getImageData(window, this).imageData;
}
catch (e){}
// if "this" is not a correct context the next line will throw an error
var ret = original.apply(this, window.Array.from(arguments));
var newImageData = getImageData(window, this).imageData; var newImageData = getImageData(window, this).imageData;
this.putImageData(randomMixImageData(window, oldImageData, newImageData), 0, 0); this.putImageData(randomMixImageData(window, oldImageData, newImageData), 0, 0);
return ret; return ret;
@ -249,12 +259,17 @@
return status; return status;
}, },
object: "CanvasRenderingContext2D", object: "CanvasRenderingContext2D",
fakeGenerator: function(prefs, notify){ fakeGenerator: function(prefs, notify, window, original){
return function strokeText(str, x, y){ return function strokeText(str, x, y){
notify("fakedInput"); notify("fakedInput");
var window = getWindow(this.canvas); var oldImageData;
var oldImageData = getImageData(window, this).imageData; try {
var ret = window.CanvasRenderingContext2D.prototype.strokeText.apply(this, arguments); // "this" is not trustable - it may be not a context
oldImageData = getImageData(window, this).imageData;
}
catch (e){}
// if "this" is not a correct context the next line will throw an error
var ret = original.apply(this, window.Array.from(arguments));
var newImageData = getImageData(window, this).imageData; var newImageData = getImageData(window, this).imageData;
this.putImageData(randomMixImageData(window, oldImageData, newImageData), 0, 0); this.putImageData(randomMixImageData(window, oldImageData, newImageData), 0, 0);
return ret; return ret;
@ -269,13 +284,12 @@
return status; return status;
}, },
object: ["WebGLRenderingContext", "WebGL2RenderingContext"], object: ["WebGLRenderingContext", "WebGL2RenderingContext"],
fakeGenerator: function(prefs, notify){ fakeGenerator: function(prefs, notify, window, original){
return function readPixels(x, y, width, height, format, type, pixels){ return function readPixels(x, y, width, height, format, type, pixels){
// not able to use the getFakeCanvas function because the context type is wrong... // not able to use the getFakeCanvas function because the context type is wrong...
notify("fakedReadout"); notify("fakedReadout");
var xPixels = Cu.waiveXrays(pixels); var xPixels = Cu.waiveXrays(pixels);
var window = getWindow(this.canvas); var ret = original.apply(this, window.Array.from(arguments));
var ret = window.WebGLRenderingContext.prototype.readPixels.apply(this, arguments);
var l = xPixels.length; var l = xPixels.length;
var rng = randomSupply.getRng(l, window); var rng = randomSupply.getRng(l, window);

1
releaseNotes.txt
View File

@ -8,6 +8,7 @@ Version 0.3.8:
fixes: fixes:
- prevented error when canvas has size zero - prevented error when canvas has size zero
- frame script was not loaded in the first tab that was restored from the last session - frame script was not loaded in the first tab that was restored from the last session
- prevented error when wrong object is passed to the faked functions
Version 0.3.7: Version 0.3.7:
new features: new features: