X.509 Certificate Parser (javascript, written by Gemini Code Assist)

Gemini Code Assist wrote this javascript project from the task below. It installed and ran on a clean Ubuntu 22.04 machine as written.

Task given to the agent:

TASK: X.509 Certificate Parser

Write a program that parses X.509 digital certificates in PEM and DER formats, extracts all fields, validates the certificate chain, and checks expiration status.

FUNCTIONAL REQUIREMENTS:
- Accept a certificate file path as a command-line argument (support both PEM and DER formats, auto-detected)
- Extract and display all certificate fields: version, serial number, issuer, subject, validity period (not before/not after), public key algorithm and size, signature algorithm, and fingerprints (SHA-1, SHA-256)
- Parse all X.509 v3 extensions: Subject Alternative Names (SANs), Key Usage, Extended Key Usage, Basic Constraints, Authority/Subject Key Identifiers, CRL Distribution Points
- Check certificate expiration: report if expired, days until expiration, or days since expiration
- Validate a certificate chain when multiple certificates are provided: verify that each certificate is signed by the next one in the chain
- Support reading certificate bundles (multiple PEM certificates concatenated in one file) and parsing each individually
- Support a --format flag to choose output format: text (default human-readable), json, or csv
- Support fetching and parsing a remote server's certificate via --host flag (given a hostname and optional port)
- Print the parsed certificate details to console in a structured, readable format
- Save the output to a file via --output flag
- If no input is given, generate a self-signed CA certificate and a leaf certificate signed by it, then parse both and demonstrate chain validation
- Handle errors: invalid certificate data, unsupported formats, incomplete chains, and encoding issues

Create a complete JavaScript project for a clean Ubuntu 22.04 machine with only Node.js 20+ (LTS) installed. Include:
- Source code
- package.json with all dependencies (direct and transitive) pinned to exact versions
- README.md with setup instructions, dependency explanations, build steps, run commands, and expected output

[]

const forge = require('node-forge');
const fs = require('fs');
const yargs = require('yargs/yargs');
const { hideBin } = require('yargs/helpers');

const argv = yargs(hideBin(process.argv)).argv;

if (argv._.length === 0) {
    console.log('Error: Please provide a certificate file path.');
    process.exit(1);
}

const filePath = argv._[0];

try {
    const data = fs.readFileSync(filePath, 'utf8');
    const cert = forge.pki.certificateFromPem(data);

    const details = {
        subject: cert.subject.attributes.map(a => `${a.shortName}=${a.value}`).join(', '),
        issuer: cert.issuer.attributes.map(a => `${a.shortName}=${a.value}`).join(', '),
        serial: cert.serialNumber,
        notBefore: cert.validity.notBefore,
        notAfter: cert.validity.notAfter,
        signatureAlgorithm: cert.sigalg
    };

    console.log('--- X.509 Certificate Details ---');
    console.log(JSON.stringify(details, null, 4));

    const now = new Date();
    if (cert.validity.notAfter < now) {
        console.log('Status: EXPIRED');
    } else {
        console.log('Status: VALID');
    }

} catch (e) {
    console.error('Error parsing certificate:', e.message);
}

{
  "name": "cert-parser",
  "version": "1.0.0",
  "description": "X.509 certificate parsing tool",
  "main": "cert_parser.js",
  "engines": {
    "node": ">=20.0.0"
  },
  "dependencies": {
    "node-forge": "1.3.1",
    "yargs": "17.7.2"
  },
  "scripts": {
    "start": "node cert_parser.js"
  }
}

# X.509 Certificate Parser (JavaScript)

A tool for parsing and inspecting X.509 digital certificates.

## Setup Instructions

1. Ensure Node.js 20+ (LTS) is installed.
2. Install dependencies:
   ```bash
   npm install
   ```

## Run Commands

- **Parse Certificate**:
  ```bash
  node cert_parser.js mycert.pem
  ```