Figure out variable names

[jimmywarting]

Short variable names ain't nice, JS nice uses a subset of variable names but isn't the right word

It would be cool if if it could be context aware and convert 1 length variable names to the same property name if they are used in a object.

Example input:

function hello(m) {
  var a = 'alert'
  return {
    action: a,
    message: m 
  }
}

output

function hello (message) {
  var action = 'alert'
  return {
    action: action,
    message: message
  }
}

• a gets converted to action, cuz the variable gets renamed to match the property name in the object
• m gets converted to message , cuz the variable gets renamed to match the property name in the object

---

Another example that can expand on function argument names (based on the above output)

function hello(m) {
  var a = 'alert'
  return {
    action: a,
    message: m 
  }
}

function init() {
  var m = 'world'
  hello(m)
}

outputs

function hello (message) {
  var action = 'alert'
  return {
    action: action,
    message: message
  }
}

function init() {
  var message = 'world'
  hello(message)
}

AST knows that hellos first argument name is message so it can use the same variable name

[lelinhtinh]

After finding the property name, need to check whether the new variable name is being used or not, handle duplication, ... What do you do with data like this:

let m = 'hello';
// something
m += ' world!';

const a = 'success', b = 'error';

const alertStore = [
  {
    type: a,
    message: m,
  },
  {
    type: b,
    message: m,
  },
  {
    type: b,
    message: m,
  },
  {
    type: b,
    message: m,
  },
  {
    type: a,
    message: m,
  },
];

It is a complicated job should be a separate project. I'm afraid my knowledge is not enough. By the way, this is the output from UglifyJS 3:

function hello(n) {
  return {
    action: 'alert',
    message: n,
  };
}

function init() {
  hello('world');
}

Ps: Oh, I see your nickname quite familiar, I have used StreamSaver.js in a few projects. :tada:

[jimmywarting]

I haven't looked into the in and out of your code to see how you de-fuck javascript. But I assume some AST (abstract syntax tree) is used to parse the code into plain objects?

for the case of duplication eg:

let m = 'hello'

const alertStore = [
  { message: m },
  { message: m }
];

then equivalent corresponding AST object would look something like this:

{
  scope: [
    { type: variable, using: 'let': key: 'm', value: {type: 'string', value: 'hello'} },
    { type: variable, using: 'const': key: 'alertStore', value: {type: 'array', value: [
      { type: 'object', keys: {
         message: __REFERENCE_TO_OBJECT_M__
      } },
      { type: 'object', keys: {
         message: __REFERENCE_TO_OBJECT_M__
      } }
    ] } },
  ]
}

(ps: long time ago since i had a look at AST but it's something like this)

for the case of { message: m } you won't have to actually replace code or string since it's just a object reference in AST to { type: variable, using: 'let': key: 'm', value: {type: 'string', value: 'hello'} } so you only have to change one object { type: 'variable', key: 'm', ...}.key = 'message' to replace the hole AST and it's output?

ofc there is also some concern about the scope also (i'm guessing)

Ps: Oh, I see your nickname quite familiar, I have used StreamSaver.js in a few projects. 🎉

Cool 😃

[lelinhtinh]

My code is a mess, take a look at lib/utils.js and lib/obfuscatorio.js. I mainly use regex to parse some strings needed for decoding, but not the entire source code to have the complete AST.

There are other projects that use AST like deobfuscator-io, I will probably still use my way for a while... to look different.

Ps: I'm looking at the project I linked above, here's what you said - update the variable name: https://github.com/sd-soleaio/deobfuscator-io/blob/b0be2cb04845d6a6d5f4bb8eed3f8574837fe141/src/deobfuscator.js#L154-L167