js-x-ray

JavaScript AST analysis. This package has been created to export the Node-Secure AST Analysis to enable better code evolution and allow better access to developers and researchers.

The goal is to quickly identify dangerous code and patterns for developers and Security researchers. Interpreting the results of this tool will still require you to have a set of security notions.

Note I have no particular background in security. I'm simply becoming more and more interested and passionate about static code analysis. But I would be more than happy to learn that my work can help prevent potential future attacks (or leaks).

Goals

The objective of the project is to successfully detect all potentially suspicious JavaScript codes.. The target is obviously codes that are added or injected for malicious purposes..

Most of the time these hackers will try to hide the behaviour of their codes as much as possible to avoid being spotted or easily understood... The work of the library is to understand and analyze these patterns that will allow us to detect malicious code..

Features Highlight

• Retrieve required dependencies and files for Node.js.
• Detect unsafe RegEx.
• Get warnings when the AST Analysis as a problem or when not able to follow a statement.
• Highlight common attack patterns and API usages.
• Capable to follow the usage of dangerous Node.js globals.
• Detect obfuscated code and when possible the tool that has been used.

Getting Started

This package is available in the Node Package Repository and can be easily installed with npm or yarn.

$ npm i @nodesecure/js-x-ray
# or
$ yarn add @nodesecure/js-x-ray

Usage example

Create a local .js file with the following content:

try  {
    require("http");
}
catch (err) {
    // do nothing
}
const lib = "crypto";
require(lib);
require("util");
require(Buffer.from("6673", "hex").toString());

---

Then use js-x-ray to run an analysis of the JavaScript code:

import { runASTAnalysis } from "@nodesecure/js-x-ray";
import { readFileSync } from "fs";

const str = readFileSync("./file.js", "utf-8");
const { warnings, dependencies } = runASTAnalysis(str);

const dependenciesName = [...dependencies];
const inTryDeps = [...dependencies.getDependenciesInTryStatement()];

console.log(dependenciesName);
console.log(inTryDeps);
console.log(warnings);

The analysis will return: http (in try), crypto, util and fs.

Warning There is also a lot of suspicious code example in the ./examples cases directory. Feel free to try the tool on these files.

Warnings

This section describes how use warnings export.

The structure of the warnings is as follows:

/**
 * @property {object}  warnings                - The default values for Constants.
 * @property {string}  warnings[name]          - The default warning name (parsingError, unsafeImport etc...).
 * @property {string}  warnings[name].i18n     - i18n token.
 * @property {string}  warnings[name].code     - Used to perform unit tests.
 * @property {string}  warnings[name].severity - Warning severity.
 */
 
export const warnings = Object.freeze({
    parsingError: {
      i18n: "sast_warnings.ast_error"
      code: "ast-error",
      severity: "Information"
    },
    ...otherWarnings
  });

We make a call to i18n through the package NodeSecure/i18n to get the translation.

import * as jsxray from "@nodesecure/js-x-ray";
import * as i18n from "@nodesecure/i18n";

console.log(i18n.getToken(jsxray.warnings.parsingError.i18n));

Warnings Legends

Warning versions of NodeSecure greather than v0.7.0 are no longer compatible with the warnings table below.

This section describe all the possible warnings returned by JSXRay. Click on the warning name for additional information and examples.

name	experimental	description
parsing-error	❌	The AST parser throw an error
unsafe-import	❌	Unable to follow an import (require, require.resolve) statement/expr.
unsafe-regex	❌	A RegEx as been detected as unsafe and may be used for a ReDoS Attack.
unsafe-stmt	❌	Usage of dangerous statement like eval() or Function("").
unsafe-assign	❌	Assignment of a protected global like process or require.
encoded-literal	❌	An encoded literal has been detected (it can be an hexa value, unicode sequence or a base64 string)
short-identifiers	❌	This mean that all identifiers has an average length below 1.5.
suspicious-literal	❌	A suspicious literal has been found in the source code.
obfuscated-code	✔️	There's a very high probability that the code is obfuscated.
weak-crypto	✔️	The code probably contains a weak crypto algorithm (md5, sha1...)

API

runASTAnalysis(str: string, options?: RuntimeOptions): Report

interface RuntimeOptions {
    module?: boolean;
    isMinified?: boolean;
}

The method take a first argument which is the code you want to analyse. It will return a Report Object:

interface Report {
    dependencies: ASTDeps;
    warnings: Warning<BaseWarning>[];
    idsLengthAvg: number;
    stringScore: number;
    isOneLineRequire: boolean;
}

runASTAnalysisOnFile(pathToFile: string, options?: RuntimeFileOptions): Promise< ReportOnFile >

interface RuntimeOptions {
    module?: boolean;
    isMinified?: boolean;
}

Run the SAST scanner on a given JavaScript file.

export type ReportOnFile = {
  ok: true,
  warnings: Warning<BaseWarning>[];
  dependencies: ASTDeps;
  isMinified: boolean;
} | {
  ok: false,
  warnings: Warning<BaseWarning>[];
}

Contributors ✨

Thanks goes to these wonderful people (emoji key):

Gentilhomme 💻 📖 👀 🛡️ 🐛

Nicolas Hallaert 📖

Antoine 💻

Mathieu 💻

Vincent Dhennin 💻 ⚠️

Tony Gorez 💻 📖 ⚠️

License

MIT