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We can use the relationship between the array and the dec function to hone in on the correct one. To make a long story short, Im releasing a Javascript deobfuscation tool called REstringer, both as code and as an online tool. Your question is unclear. How can I remove a specific item from an array in JavaScript? _0xca830a), Converts computed to static member expressions and beautifies the code. Now, I take that value and replace the function call with it. Just a quick reminder - Im going to be using the flAST package to flatten the AST to make it easier to find code structures that are referencing each other, and replace them with the deobfuscate strings. However, the readability is not improved anyway as the whole code makes use of the string array. Is there an easy way to deobfuscate this javascript? ), // Replace the BinaryExpression with the simplified value, * Writes the deobfuscated code to output.js, // Replace the BinaryExpression with a new node of inferred type, Deobfuscating Javascript via AST: Removing Dead or Unreachable Code, Deobfuscating Javascript via AST: A Peculiar JSFuck-esque Case, Though not directly applicable to this code snippet, another problem is worth mentioning. How do I remove a property from a JavaScript object? The best answers are voted up and rise to the top, Not the answer you're looking for? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. I have been trying to deobfuscate it myself by hand, but my javascript is perhaps not that strong. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. You should format your document first before doing other tasks so it reduces chance of your code become corrupt. To learn more, see our tips on writing great answers. If I understand correctly, the array won't end up rotated (the function taking (C,o) is just noise), and I should be able to just substitute the indices from R into the rest and simplify to get the following equivalent code: But this seems like nonsense. There are indicators of a VM environment. An example with simple proxy functions for other functions, An example with proxy functions for arithmetic, Unpacks arrays containing literals (strings, numbers etc) and replaces all references to them, Removes simple proxy functions (calls to another function), array proxy functions and arithmetic proxy functions (binary expressions), Renames unreadable hexadecimal identifiers (e.g. Make even obfuscated JavaScript code readable. Okay, thats all I have to cover for today. All formatting tools affects selected text, or all text in editor if none selected. If anyone wants to take a look at the file they can find it here. I hope we all meet again in REstringer 2: The Search for More Obfuscation, and may the Schwartz be with you! What should I follow, if two altimeters show different altitudes? A node representation of undefined or null still will not be falsy, since a node is an object. Guys blog deals with a different obfuscation type though - the Augmented Array Function Replacements (skipped the un-augmented version). To tell the deobfuscator to execute this function, you can use the "#execute" directive like so: The deobfuscator will then evaluate this function and attempt to replace any calls to it with the correct values: A few important points about function evaluation: Either install the module locally via npm install js-deobfuscator and import as usual or install globally npm install -g js-deobfuscator and use the js-deobfuscator CLI: Alternatively use the online version at deobfuscate.io. If youre interested, you can find the source code for all the examples in this repository. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. I collect these files and analyze them. Thankfully for us, the path.evaluate() method can also be used for UnaryExpressions. dec = () => {}; This solution is still lacking, though, since it does not cover all possible scenarios. After processing the obfuscated script with the babel plugin above, we get the following result: Thats a lot of simplification! Is there any known 80-bit collision attack? So putting that all together, we have the following logic for our deobfuscator: Traverse the ast for nodes of type BinaryExpression and UnaryExpression. SpiderMonkey is a modified version of Mozilla's C implementation of JavaScript, with some extra functions to help with malware analysis. If we had a video livestream of a clock being sent to Mars, what would we see? Horizontal and vertical centering in xltabular. Heres a cleaned up version of this method: This description wouldnt be complete without a list of currently available safe and unsafe methods: Id love to go into more details in the future about how I implemented the eval mechanism, how the caching works, choices I made regarding what can and cannot be deobfuscated at any given time, or how I collect context recursively.