Audit Node Modules With YARA Rules

(New Rules, Feedbacks, PRs are highly appreciated)

Table of content

• Purpose
• Software Requirements
• How to use
• CI/CD integration
• Adding YARA new rules

Purpose

• The purpose of this tool is to run a given set of YARA rules against the given node_module folder.

• With this approach, We can define YARA rules to identify suspicious scripts which are injected into node packages.

• Mainly inspired by these articles.

  • Malicious packages in npm. Here’s what to do
  • Malicious NPM packages target Amazon, Slack with new dependency attacks
  • Hunting malicious NPM packages

• This package can be added to the CI/CD pipeline as mentioned below (CI/CD integration).

Software Requirements

• Docker
• Docker Compose
• Makefile

How to use

1. Clone this repo

git clone https://github.com/rpgeeganage/audit-node-modules-with-yara.git

2. Execute audit operation

make NODE_MODULE_FOLDER_TO_AUDIT=<path to node_module> run

e.g:

make NODE_MODULE_FOLDER_TO_AUDIT=../restful4up/node_modules run

Report

The report is available in artifacts/output.json.

A sample report looks as follows

[
 {
  "rule": "evil_package_1",
  "string_information": [
   "0x6:$name: \"name\": \"nodecaffe\",",
   "0x1f:$version: \"version\": \"0.0.1\""
  ]
 },
 {
  "rule": "evil_package_2",
  "string_information": [
   "0x6:$name: \"name\": \"sqlserver\",",
   "0x1f:$version: \"version\": \"4.0.5\""
  ]
 },
 {
  "rule": "evil_package_3",
  "string_information": [
   "0x1d:$scripts: \"scripts\":",
   "0x39:$install: \"mkdir -p ~/Desktop/sploit && touch ~/Desktop/sploit/haxx\""
  ]
 }
]

CI/CD Integration

We can use this tool with CI/CD as mentioned below.

#!/bin/bash
make NODE_MODULE_FOLDER_TO_AUDIT=../restful4up/node_modules run

suspicious_file_count=$(jq length artifacts/output.json)

exit $suspicious_file_count

Adding YARA new rules

When we need to add new YARA rules, they must be added to the yara_rules folder with extension .yara.

(Existing rules are created based on this article. They might be outdated)

Sample YARA rule

Let's create a rule for this possible malicious package.

A possible rule is as below.

rule evil
{
    meta:
        name = "evil@0.0.1"

    strings:
        $scripts = /"scripts":/
        $install = /"mkdir -p ~\/Desktop\/sploit && touch ~\/Desktop\/sploit\/haxx"/

    condition:
        all of them
}

Save this rule in yara_rules folder as evil.yara, and good to go