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Deobfuscator for javascript samples obfuscated by obfuscator.io.
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0x1Avram/js-deobfuscator
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Deobfuscator forTimofey Kachalov'sjavascript-obfuscator - also available atobfuscator.io.
The code here is not secure. It uses 'eval' for convenience purposes and could easily be exploited by someone with malicious intent. That is why this should only be used in secure and isolated environments. Under no circumstances should anyone run this on a real environment - at least, use a virtual machine or something to protect your system !!!
- Clone this project:
git clone https://github.com/0x1Avram/js-deobfuscator.git- Install node.js (I used version 16.15)
- Install dependencies by running this command in the folder root:
npm install- Enjoy
I included binaries built for Windows/Linux in the release section (for the windows one, you will need to add the proper '.exe' extension in order to use it). Those binaries where built using pkg and can be run on a system standalone, without the need to install node.js or any other dependencies.Their respective SHA256 hashes can be found in the release section as well.
For those wanting to build this into an executable themselves, installpkg and then run this command in the folder root
pkg index.jsTo showcase the deobfuscator capabilities, I included some sets of original + obfuscated + deobfuscated samples in the 'Examples' folder.Some of those use examples fromjavascript-obfuscator orjavascript-algorithms.Here are their respective copyright licenses:
Copyright (C) 2016-2022 Timofey Kachalov.Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.The MIT License (MIT)Copyright (c) 2018 Oleksii TrekhlebPermission is hereby granted, free of charge, to any person obtaining a copyof this software and associated documentation files (the "Software"), to dealin the Software without restriction, including without limitation the rightsto use, copy, modify, merge, publish, distribute, sublicense, and/or sellcopies of the Software, and to permit persons to whom the Software isfurnished to do so, subject to the following conditions:The above copyright notice and this permission notice shall be included in allcopies or substantial portions of the Software.THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS ORIMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THEAUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHERLIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THESOFTWARE.The "main" script is index.js. Calling it with a '-h' argument should display the command line options.The deobfuscator tries to automatically detect the stringarray related code. If it manages to do so correctly, it can be run by just specifying the input and output path.
node ./index.js -i obfuscated.txt -o deobfuscated.txtOtherwise, the code for the stringarray needs to be placed in separate files and given as input. Example:
node ./index.js -s stringarray.txt -w stringarraywrappers.txt -n _0x471d,_0x9cad,_0x4cd9 -r stringarrayrotate.txt -i obfuscated.txt -o output.txtMore examples regarding how the stringarray related code looks like along with command lines can be found in the 'Examples' folder.
Detailed information about the command line options:
node .\index.js -hUsage: program [options]Options: --version Show version number [boolean] -i, --inputPath Path of input (obfuscated) file. [string] [default: "input.txt"] -o, --outputPath Path where the output (deobfuscated) file is stored. [string] [default: "output.txt"] -d, --debug Display debug log messages (for large input files, debug log might be large). [boolean] [default: false] -a, --debugall Display all AST operations for debugging. The 'debug' option needs to be set for this to work. [boolean] [default: false] -l, --separateloggers Use a separate logger for each deobfuscation stage. This will lead to the creation of a debug log file for each deobfuscation stage (11 stages). This is useful so that instead of a single huge debug log file, several smaller ones are created (one per each stage). The 'debug' option needs to be set for this to work. [boolean] [default: false] -f, --writedifffiles Write before&after files for each transformation modifying the source code(used for debugging). The files are written in the working directory of the script. [boolean] [default: false] -s, --stringarray [StringArray] The path at which the code for the string array is found(can be just an array or a function containing the array). [string] [default: ""] -w, --stringarraywrappers [StringArray] The path at which the code for the string wrappers is found(there can be multiple wrappers depending on the 'string-array-encoding' obfuscation option) (the wrappers can contain the self defending code). [string] [default: ""] -n, --stringarraywrappernames [StringArray] The names of the string array wrapper functions in a comma separated string without spaces. (these are the functions from the code indicated by the 'stringarraywrappers' path). [string] [default: ""] -r, --stringarrayrotate [string] [default: ""] -c, --cleanuplog [boolean] [default: false] -h, --help Show help [boolean]Examples: -s stringarray.txt -w stringarraywrappers.txt -n _0x471d,_0x9cad,_0x4cd9 -r stringarrayrotate.txt -i obfuscated.txt -o output.txt -i obfuscated.txt -o deobfuscated.txtFrom my testing, this seems to work fine with current versions of the obfuscator.However, older versions of the obfuscator may output a different AST and that might complicate things. If you happen to stumble across a case where this should work but it doesn't, open an issue and I'll look into it.
There are some scenarios where the deobfuscator might crash because an AST cannot be generated from the input. This is a limitation from the esprima parser used by the deobfuscator which does not support all new JavaScript features. If this error is encountered, a message suggesting that the code needs to be transpiled before deobfuscation will be displayed. The transpilation to an older JavaScript version for which esprima correctly parses the script can be done usingBabel and the parsing of the script can be checked with tools such asastexplorer.
- Create directory with the file you are trying to deobfuscate inside directory
- Initialize node project with default configuration:
npm init -y- Install babel:
npm install --save-dev @babel/core @babel/cli @babel/preset-env- Create '.babelrc' file inside directory with the following content
{ "presets": ["@babel/preset-env"], "compact": false}- Run babel via CLI for transpilation
Example for transpiling 'a.txt' file to 'output.js' file. ('a.txt' is the input file, not parsed by espirma; 'output.js' is the output file, successfully parsed by esprima):
npx babel a.txt -o output.jsThe MIT License (MIT)
Copyright (c) 20220x1Avram
Permission is hereby granted, free of charge, to any person obtaining a copy of thissoftware and associated documentation files (the "Software"), to deal in the Softwarewithout restriction, including without limitation the rights to use, copy, modify,merge, publish, distribute, sublicense, and/or sell copies of the Software, and topermit persons to whom the Software is furnished to do so, subject to the followingconditions:
The above copyright notice and this permission notice shall be included in all copiesor substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR APARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHTHOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTIONOF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THESOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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