JavaScript AST analysis. This package has been created to export the NodeSecure 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.
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..
- 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.
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-rayCreate 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 "node:fs";
const { warnings, dependencies } = runASTAnalysis(
readFileSync("./file.js", "utf-8")
);
console.log(dependencies);
console.dir(warnings, { depth: null });The analysis will return: http (in try), crypto, util and fs.
[!TIP] There is also a lot of suspicious code example in the
./examplescases directory. Feel free to try the tool on these files.
This section describes how use warnings export.
type WarningName = "parsing-error"
| "encoded-literal"
| "unsafe-regex"
| "unsafe-stmt"
| "short-identifiers"
| "suspicious-literal"
| "suspicious-file"
| "obfuscated-code"
| "weak-crypto"
| "unsafe-import"
| "shady-link";
declare const warnings: Record<WarningName, {
i18n: string;
severity: "Information" | "Warning" | "Critical";
experimental?: boolean;
}>;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.getTokenSync(jsxray.warnings["parsing-error"].i18n));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(""). |
| 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. |
| suspicious-file | ✔️ | A suspicious file with more than ten encoded-literal in it |
| 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...) |
| shady-link | ✔️ | The code contains shady/unsafe link |
You can also create custom probes to detect specific pattern in the code you are analyzing.
A probe is a pair of two functions (validateNode and main) that will be called on each node of the AST. It will return a warning if the pattern is detected.
Below a basic probe that detect a string assignation to danger:
export const customProbes = [
{
name: "customProbeUnsafeDanger",
validateNode: (node, sourceFile) => [
node.type === "VariableDeclaration" && node.declarations[0].init.value === "danger"
],
main: (node, options) => {
const { sourceFile, data: calleeName } = options;
if (node.declarations[0].init.value === "danger") {
sourceFile.addWarning("unsafe-danger", calleeName, node.loc);
return ProbeSignals.Skip;
}
return null;
}
}
];You can pass an array of probes to the runASTAnalysis/runASTAnalysisOnFile functions as options, or directly to the AstAnalyser constructor.
| Name | Type | Description | Default Value |
|---|---|---|---|
customParser |
SourceParser | undefined |
An optional custom parser to be used for parsing the source code. | JsSourceParser |
customProbes |
Probe[] | undefined |
An array of custom probes to be used during AST analysis. | [] |
skipDefaultProbes |
boolean | undefined |
If true, default probes will be skipped and only custom probes will be used. |
false |
Here using the example probe upper:
import { runASTAnalysis } from "@nodesecure/js-x-ray";
// add your customProbes here (see example above)
const result = runASTAnalysis("const danger = 'danger';", { customProbes, skipDefaultProbes: true });
console.log(result);Result:
✗ node example.js
{
idsLengthAvg: 0,
stringScore: 0,
warnings: [ { kind: 'unsafe-danger', location: [Array], source: 'JS-X-Ray' } ],
dependencies: Map(0) {},
isOneLineRequire: false
}Congrats, you have created your first custom probe! 🎉
[!TIP] Check the types in index.d.ts and types/api.d.ts for more details about the
options
runASTAnalysis(str: string, options?: RuntimeOptions & AstAnalyserOptions): Report
interface RuntimeOptions {
module?: boolean;
removeHTMLComments?: boolean;
isMinified?: boolean;
}interface AstAnalyserOptions {
customParser?: SourceParser;
customProbes?: Probe[];
skipDefaultProbes?: 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[];
idsLengthAvg: number;
stringScore: number;
isOneLineRequire: boolean;
}runASTAnalysisOnFile(pathToFile: string, options?: RuntimeFileOptions & AstAnalyserOptions): Promise< ReportOnFile >
interface RuntimeFileOptions {
module?: boolean;
removeHTMLComments?: boolean;
packageName?: string;
}interface AstAnalyserOptions {
customParser?: SourceParser;
customProbes?: Probe[];
skipDefaultProbes?: boolean;
}Run the SAST scanner on a given JavaScript file.
export type ReportOnFile = {
ok: true,
warnings: Warning[];
dependencies: ASTDeps;
isMinified: boolean;
} | {
ok: false,
warnings: Warning[];
}Click on one of the links to access the documentation of the workspace:
| name | package and link |
|---|---|
| estree-ast-utils | @nodesecure/estree-ast-utils |
| sec-literal | @nodesecure/sec-literal |
| ts-source-parser | @nodesecure/ts-source-parser |
These packages are available in the Node Package Repository and can be easily installed with npm or yarn.
$ npm i @nodesecure/estree-ast-util
# or
$ yarn add @nodesecure/estree-ast-util
Thanks goes to these wonderful people (emoji key):
MIT