Decoding non-alphanumeric code with Hackvertor

I saw this post from Thomas Stig Jacobsen. He uses eval to decompile the code, I thought there has to be a better way 🙂 so in literally about 30 minutes I managed to do it after a few tweaks to the JSReg code base. What does non-alphanumeric JavaScript look like?


$=~[];$={___:++$,$$$$:(![]+"")[$],__$:++$,$_$_:(![]+"")[$],_$_:++$,$_$$:({}+"")[$],$$_$:($[$]+"")[$],_$$:++$,$$$_:(!""+"")[$],$__:++$,$_$:++$,$$__:({}+"")[$],$$_:++$,$$$:++$,$___:++$,$__$:++$};$.$_=($.$_=$+"")[$.$_$]+($._$=$.$_[$.__$])+($.$$=($.$+"")[$.__$])+((!$)+"")[$._$$]+($.__=$.$_[$.$$_])+($.$=(!""+"")[$.__$])+($._=(!""+"")[$._$_])+$.$_[$.$_$]+$.__+$._$+$.$;$.$$=$.$+(!""+"")[$._$$]+$.__+$._+$.$+$.$$;$.$=($.___)[$.$_][$.$_];$.$($.$($.$$+"\""+$.$_$_+(![]+"")[$._$_]+$.$$$_+"\\"+$.__$+$.$$_+$._$_+$.__+"(\\\"\\"+$.__$+$.__$+$.___+$.$$$_+(![]+"")[$._$_]+(![]+"")[$._$_]+$._$+",\\"+$.$__+$.___+"\\"+$.__$+$.__$+$._$_+$.$_$_+"\\"+$.__$+$.$$_+$.$$_+$.$_$_+"\\"+$.__$+$._$_+$._$$+$.$$__+"\\"+$.__$+$.$$_+$._$_+"\\"+$.__$+$.$_$+$.__$+"\\"+$.__$+$.$$_+$.___+$.__+"\\\"\\"+$.$__+$.___+")"+"\"")())();


Produced by my friend Yosuke Hasegawa using his JJEncode.

How the hell do you decode that Gareth? (I hear you say). Quite easily actually. First off I extend the Hackvertor environment to allow sandboxed code to call the JSReg parser.


parser.extendWindow("$sandbox$", function(code){});


This makes “sandbox” a global function within each tag, I need to do this because I want to listen for any calls to “Function” and instead of eval’ing the results I simply want to return the string generated. To do this I add more code to the “sandbox” function to create an instance of JSReg and execute the code:-


parser.extendWindow("$sandbox$", function(code){
var js = JSReg.create(), result;
js.setDebugObjects({doNotFunctionEval:true,functionCode: function(code) {
code = code.replace("J.F();var $arguments$=J.A(arguments);",'');
result = code;
}});
try {
js.eval(code);
} catch(e){
return e;
}
return result;
});


So as you can see the magic happens in the debug objects of JSReg, I use the “doNotFunctionEval” to listen to Function but not eval the code sent. Then I use another listener to “functionCode” to intercept the results.

The final Hackvertor tag is dead simple:-

(function(){
return sandbox(code);
})();


The final results can be seen here:-
Decode non-alpha please feel free to go whoa now. That’s sandboxed code calling a unsandboxed function, sending a non-alpha string, sandboxing it, listening to the results and returning the decoded code. In the blink of an eye 🙂

Credits as always to Lever one and Jonas Magazinius for testing JSReg and making this possible.