I am trying my hand a reversing a malicious js script to find out what it does. the script is really long but there is one part I dont fully understand and hope you can help. I will only show a small part of the script with the relevant parts to help with this problem so as to avoid anyone accidentally running it.
The following line calls the function UU multiple times:
ib[0] = O(Arw,UU(1017-980)+UU(19+81)+UU(32*3)+UU(51+25)+UU(4508/98+0)+UU(671-606)+UU(1677/43+0)+UU(631-522)+UU(5*23)+UU(7719/83-0)+UU(6+93)+UU(4*23));
The function UU has the following setup:
function UU(s)
{
var Ea = ",!)Q ;Zrvz2^#HgS{I~1(O`ba'&l%$mqVCXG9#w0]d.-8W_34[kA5<n/RBDLsFN\\tpY6E7fy?oi|+\"xJ>ThUc=uKjeM:}*P";
var h=30090;
var yz=h+29060;
var mm=yz/650;
var PF=mm-60; 31
var i = Ea[L(s)](s-PF);
return i;
}
Part of the operation to get the return value "i" calls the function L:
function L(R)
{
return "\x63\x68\x61\x72A\x74";
}
Question: what is function L returning?
I believe the function L is trying to obfuscate its return value so as to make analysis harder. I am not sure if I need to convert this to ASCII or Decimal in order to accurately complete the string lookup in function UU
Those are escape characters. It is fairly easy to look up the values in the ASCII table, but you can also console.log the string to see the resulting value.
console.log("\x63\x68\x61\x72A\x74");
It evaluates to charAt.
Related
So I came across an interesting piece of javascript that I can't quit figure out. It appears to me at first to be either regex function or a unicode string, that is then passed onto an eval function for processing. I have been trying for quite some time to decode it, but I don't seem to be making any headway. I'm hoping someone might be able to tell me what is going on here, and maybe show me how to decode it.
Edit: So it turns out that the code I posted before was flawed from a previous decoding attempt. This is the corrected code.
$(window).load(function() {
var d = '960';
var d1 = '960';
var q = 'u94';
var uw = $("#u94");
var _0xf924 = ["1m 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C};18(!B[5][B[4]](/^/,1j)){17(C--){14[C]=I[C]||C};I=[U(H){O 14[H]}];H=U(){O B[6]};C=1};17(C--){18(I[C]){P=P[B[4]](1i 1h(B[7]+H(C)+B[7],B[8]),I[C])}};O P}(B[0],10,1e,B[3][B[2]](B[1]),0,{}))", "|", "split", "|||||||||x5C|x35|x31|x5D|x5B|x34|x36|x30|x37|x38|x32|x39|x33|x2C|x7C|x78|x65|x29|x28|x22|x3D|x3B|x20|x5F|x24|x2B|x7B|x7D|_0xaced|_0x985ex3|x2F|x64|x6E|x61|_0x985ex5|_0x985ex4|x6C|x69|x73|x66|x44|return|_0x985ex1|x26|x63|x2D|x77|function|x62|x74|x21|x2A|x41||x72|x75|x70|_0x985ex6|x6F|x45|while|if|x43|x67|x42|x71|x3E|144|x3A|x3C|RegExp|new|String|x46|x49|var|x7A|x68|x6D|eval|_0x985ex2|x76", "", "fromCharCode", "replace", "\\w+", "\\b", "g"];
eval(function(_0x4a22x1, _0x4a22x2, _0x4a22x3, _0x4a22x4, _0x4a22x5, _0x4a22x6) {
_0x4a22x5 = function(_0x4a22x3) {
return (_0x4a22x3 < _0x4a22x2 ? _0xf924[4] : _0x4a22x5(parseInt(_0x4a22x3 / _0x4a22x2))) + ((_0x4a22x3 = _0x4a22x3 % _0x4a22x2) > 35 ? String[_0xf924[5]](_0x4a22x3 + 29) : _0x4a22x3.toString(36))
};
if (!_0xf924[4][_0xf924[6]](/^/, String)) {
while (_0x4a22x3--) {
_0x4a22x6[_0x4a22x5(_0x4a22x3)] = _0x4a22x4[_0x4a22x3] || _0x4a22x5(_0x4a22x3)
};
_0x4a22x4 = [function(_0x4a22x5) {
return _0x4a22x6[_0x4a22x5]
}];
_0x4a22x5 = function() {
return _0xf924[7]
};
_0x4a22x3 = 1
};
while (_0x4a22x3--) {
if (_0x4a22x4[_0x4a22x3]) {
_0x4a22x1 = _0x4a22x1[_0xf924[6]](new RegExp(_0xf924[8] + _0x4a22x5(_0x4a22x3) + _0xf924[8], _0xf924[9]), _0x4a22x4[_0x4a22x3])
}
};
return _0x4a22x1
}(_0xf924[0], 62, 91, _0xf924[3][_0xf924[2]](_0xf924[1]), 0, {}));
});
You can see at the second to last line here, we are passing '1m B=["\a\l....' to the function inside the eval. When I first saw this, I thought it was a Regex of some kind that was then converted by the browser as text, but to my knowledge, there isn't a way to convert it back? Looking into this further, I was told that it could all be unicode, but trying to convert the string back into characters has failed in ever converter I have tried. Am I way off base here?
EDIT: See below for update! I exceeded the character limit, lol!
This line var uw = $("#u94"); almost certainly means it's using content from the page itself to do the decoding.
The easiest way I can think of to try to get the code that is actually running is to return to where you found the code and open up your dev tools. Find the code again (I am guessing it's probably dynamically generated) and then without leaving the page copy/paste it into the text editor of your choice and do the following:
1) Change the first line like this
$(window).load(function() { -> (function() {
2) Change the last line like this:
}); -> })() (now you have a self-calling function)
3) Just before the last return add a console.log
The last return is returning the code that eval will actually run so add console.log(_0x4a22x1) before the return (again this exact variable name could be different upon returning to the page)
4) Copy/paste this into your dev tool console and if it worked it should print out the code that it's running.
NOTE: It's entirely possible that once the code runs the first time it removes the element (currently #u94) that contains something you need to run the code (so it could not work). So if it doesn't log the code out, then the first thing I would do it is a normal View page source (or curl the html) and find out what the #u94 element contains and adapt the code as necessary.
Good luck!
I was going through some downloaded javascripts and found code is written in Hexadecimal values instead of the 'normal' js syntax. For example:
if (!_0x7cd2x2[_0x2dae[19]](_0x2dae[18])) {
var _0x7cd2x8 = true;
_0x7cd2x2[_0x2dae[21]](_0x2dae[20]);
} else {
var _0x7cd2x8 = false;
_0x7cd2x2[_0x2dae[21]](_0x2dae[22]);
}
;
if (_0x7cd2x2[_0x2dae[19]](_0x2dae[23])) {
var _0x7cd2x9 = true
}
;
Can somebody please help me in understanding the code and how it was done.
So, in fact, the code above is 100% perfectly valid javascript. The original script has been run through an obfuscator in order to make it difficult to understand.
Most likely whichever obfuscator was used replaces variable names with numbers, prefixes them with "_" and prints the number as a hex value.
To understand the code you will need the entire sample, and a lot of patience.
I am looking at the source of pace.js and it has a pretty long source code of about a thousand lines. You can view the source here.
I need to debug this code. Is there any tool or method in JavaScript using which one can identify how many unique functions are there in a given plugin? I found one way which is:
Paste the code in a text editor
Identify each function individually
Paste a console.log("i am so and so function").
Run the script and copy paste the result from the console in a text editor
Count the number of functions
Is there a easier way to do this?
This approach first finds all the functions in the window object. Then passes those function references to 'getInnerFunction()' which matches the function against a regular expression to detect any inner functions. Finally the count of functions is returned.
However it will not be able to detect inner functions of native function present in the browser, since they return
function FUNCTION NAME {
[native code]
}
this as the to string output.
For other cases this should work. Just call fnCount() and you will receive the number of functions present (subtract 2 from the result to exclude these 2 functions).
** Please correct me if there is any problem with the function matching regular expression.
function fnCount(){
var keys = Object.keys(window);
var property;
var count = 0;
for(var i=0;i<keys.length; i++){
property = window[keys[i]];
if(typeof(property) === 'function'){
count += getInnerFunction(property);
}
}
return count;
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function getInnerFunction(property){
var fn = property.toString();
var fnCount = fn.match(/function.*\(.*\).*{.*/g).length;
return fnCount;
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Open notepad++, press CTRL+F, type function, click Find all...
In Javascript what is the best way to handle scenarios when you have a set of arrays to perform tasks on sets of data and sometimes you do not want to include all of the arrays but instead a combination.
My arrays are labeled in this small snippet L,C,H,V,B,A,S and to put things into perspective the code is around 2500 lines like this. (I have removed code notes from this post)
if(C[0].length>0){
L=L[1].concat(+(MIN.apply(this,L[0])).toFixed(7));
C=C[1].concat(C[0][0]);
H=H[1].concat(+(MAX.apply(this,H[0])).toFixed(7));
V=V[1].concat((V[0].reduce(function(a,b){return a+b}))/(V[0].length));
B=B[1].concat((MAX.apply(this,B[0])-MIN.apply(this,B[0]))/2);
A=A[1].concat((MAX.apply(this,A[0])-MIN.apply(this,A[0]))/2);
D=D[1].concat((D[0].reduce(function(a,b){return a+b}))/(D[0].length));
S=S[1].concat((S[0].reduce(function(a,b){return a+b}))/(S[0].length));
}
It would seem counter-productive in this case to litter the code with tones of bool conditions asking on each loop or code section if an array was included in the task and even more silly to ask inside each loop iteration with say an inline condition as these would also slow down the processing and also make the code look like a maze or rabbit hole.
Is there a logical method / library to ignore instruction or skip if an option was set to false
All I have come up with so far is kind of pointless inline thing
var op=[0,1,1,0,0,0,0,0]; //options
var L=[],C=[],H=[],V=[],B=[],A=[],D=[],S=[];
op[0]&&[L[0]=1];
op[1]&&[C[0]=1,console.log('test, do more than one thing')];
op[2]&&[H[0]=1];
op[3]&&[V[0]=1];
op[4]&&[B[0]=1];
op[5]&&[A[0]=1];
op[6]&&[A[0]=1];
It works in that it sets only C[0] and H[0] to 1 as the options require, but it fails as it needs to ask seven questions per iteration of a loop as it may be done inside a loop. Rather than make seven versions of the the loop or code section, and rather than asking questions inside each loop is there another style / method?
I have also noticed that if I create an array then at some point make it equal to NaN rather than undefined or null the console does not complain
var L=[],C=[],H=[],V=[],B=[],A=[],D=[],S=[];
L=NaN;
L[0]=1;
//1
console.log(L); //NaN
L=undefined;
L[0]=1
//TypeError: Cannot set property '0' of undefined
L=null
L[0]=1
//TypeError: Cannot set property '0' of null
Am I getting warmer? I would assume that if I performed some math on L[0] when isNaN(L)===true that the math is being done but not stored so the line isn't being ignored really..
If I understand what you want I would do something like this.
var op = [...],
opchoice = {
//these can return nothing, no operation, or a new value.
'true': function(val){ /*operation do if true*/ },
'false': function(val){ /*operation do if false*/ },
//add more operations here.
//keys must be strings, or transformed into strings with operation method.
operation: function(val){
//make the boolean a string key.
return this[''+(val == 'something')](val);
}
};
var endop = [];//need this to prevent infinite recursion(loop).
var val;
while(val = op.shift()){
//a queue operation.
endop.push(opchoice.operation(val));
}
I'm sure this is not exactly what you want, but it's close to fulfilling the want of not having a ton of conditions every where.
Your other option is on every line do this.
A = isNaN(A) ? A.concat(...) : A;
Personally I prefer the other method.
It looks like you repeat many of the operations. These operations should be functions so at least you do not redefine the same function over and over again (it is also an optimization to do so).
function get_min(x)
{
return +(MIN.apply(this, a[0])).toFixed(7);
}
function get_max(x)
{
return +(MAX.apply(this, a[0])).toFixed(7);
}
function get_average(x)
{
return (x[0].reduce(function(a, b) {return a + b})) / (x[0].length);
}
function get_mean(x)
{
return (MAX.apply(this, x[0]) - MIN.apply(this, x[0])) / 2;
}
if(C[0].length > 0)
{
L = L[1].concat(get_min(L));
C = C[1].concat(C[0][0]);
H = H[1].concat(get_max(H));
V = V[1].concat(get_average(V));
B = B[1].concat(get_mean(B));
A = A[1].concat(get_mean(A);
D = D[1].concat(get_average(D));
S = S[1].concat(get_average(S));
}
You could also define an object with prototype functions, but it is not clear whether it would be useful (outside of putting those functions in a namespace).
In regard to the idea/concept of having a test, what you've found is probably the best way in JavaScript.
op[0] && S = S[1].concat(get_average(S));
And if you want to apply multiple operators when op[0] is true, use parenthesis and commas:
op[3] && (V = V[1].concat(get_average(V)),
B = B[1].concat(get_mean(B)),
A = A[1].concat(get_mean(A));
op[0] && (D = D[1].concat(get_average(D)),
S = S[1].concat(get_average(S)));
However, this is not any clearer, to a programmer, than an if() block as shown in your question. (Actually, many programmers may have to read it 2 or 3 times before getting it.)
Yet, there is another solution which is to use another function layer. In that last example, you would do something like this:
function VBA()
{
V = V[1].concat(get_average(V));
B = B[1].concat(get_mean(B));
A = A[1].concat(get_mean(A));
}
function DS()
{
D = D[1].concat(get_average(D));
S = S[1].concat(get_average(S));
}
op = [DS,null,null,VBA,null,null,...];
for(key in op)
{
// optional: if(op[key].hasOwnProperty(key)) ... -- verify that we defined that key
if(op[key])
{
op[key](); // call function
}
}
So in other words you have an array of functions and can use a for() loop to go through the various items and if defined, call the function.
All of that will very much depend on the number of combinations you have. You mentioned 2,500 lines of code, but the number of permutations may be such that writing it one way or the other will possibly not reduce the total number of lines, but it will make it easier to maintain because many lines are moved to much smaller code snippet making the overall program easier to understand.
P.S. To make it easier to read and debug later, I strongly suggest you put more spaces everywhere, as shown above. If you want to save space, use a compressor (minimizer), Google or Yahoo! both have one that do a really good job. No need to write your code pre-compressed.
So today I got interested in learning a script that randomizes each letter/number, such as 0000-0000 and each 0 gets randomized by random letter or number. In my previous post I asked about how to do it and got the script, however; the problem I'm having now is completely understanding the code.
jQuery(document).ready(function ($) {
function randomised(len) {
return Math.floor(Math.random() * len);
}
function randomiseString(str){
var charSet = "abcdefghijklmnopqrstuvwxyz0123456789";
var _str = str.replace(/[^-]/g,function(a){
return charSet[randomised(charSet.length)]
});
return _str;
}
$('.combination').text(function(i,t){
return randomiseString(t);
});
});
So this is the code, and here are some of the stuff I'm wondering about:
var _str = str.replace(/[^-]/g,function(a){
return charSet[randomised(charSet.length)]
});
1) So this is the main part that makes the randomization. I'm now having perhaps silly thoughts but I'm wondering how can I force upper-case all the letters I've set above. I know I could just replace those letters with upper-case letters, but I'd like to know how can I do it with code. Also if I understand correctly it makes the charSet an array?
var _str = str.replace(/[^-]/g,function(a)
2) Why does the function have (a) value? Does it make any difference weather I leave it blank or not?
Thanks in advance!
Javascript doesn't require that the parameters passed to a function match the parameters expected by the function at all. This means that you can safely omit the parameters to any function if you don't need them, and in the code above, instead of
function (a) {
// code that doesn't use a
}
you could use
function () {
// ...
}