I want to customize individual javascript functions so that they behave differently then the default javascript engine (without recompiling the whole browser))
I was trying to get the eval function to misbehave in an demo addon I've been working on. Basically I wanted to see how hard it would be to fool various javascript fingerprinting frameworks, some of which rely on how some javascript functions react. I was hoping that firefox was flexible enough to dodge some of these fingerprinting attempts but I have not been able to modify it in an addon alone. Does anyone know if there is a way to do this? Even a project that already alters these kinds of functions, that I could dig through to investigate how this could be done?
Thank you,
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Ok, you have been here awhile so will give you this google search I did and see if these extensions help you do what you want.
https://addons.mozilla.org/en-US/firefox/addon/custom-style-script/
https://addons.mozilla.org/en-US/firefox/addon/execute-js/
https://addons.mozilla.org/en-US/firefox/addon/toggle-js/
Please let us know if this solved your issue or if need further assistance.
further if do a search using javascript in Firefox Add-ons Manager there is about 275 to go through and check to see if there is something you want so doing a google search might nail down to what you want Firefox Extension javascript Compiler will give you some results for making your own if so wish to.
Ok, thats a bit to chew threw, but I want to thank you for it. I'll start looking through it now.
Thx
So I tried both using addons.mozilla.org/en-US/firefox/addon/custom-style-script and I created a simple addon that just executes:
var eval=new Object();
eval.toString=function(){return "AAAAAAAAAA"};
alert("eval.toString().length == ["+eval.toString().length+"]");
And loading a page like:
<div id="m"></div>
<script>
var m = document.getElementById("m");
m.innerHTML = eval.toString().length;
</script>
and the alert will display:
"eval.toString().length == [10]"
but on the webpage itself it displays 37. Somehow the function is getting overwritten, but only temporary for the addon? Do you know if these things are maybe read-only or something?
Được chỉnh sửa bởi cor-el vào
(the posted reply got cut off, missing:
div id="m"> /div>
)
Nobody? I was hoping someone knew how modify these kinda of functions.
You can use a Greasemonkey userscript to inject some changes into web pages as/before they load. You definitely can use this method to redefine properties, but I don't know about modifying functions.
Example with properties:
The key for user script purposes is to use this line to set up your changes before the page's own DOM is built:
// @run-at document-start
See: https://wiki.greasespot.net/Metadata_Block#.40run-at
Regarding eval specifically, there are some discouraging comments here: https://stackoverflow.com/questions/2566973/how-override-eval-function-in-javascript