Certificate Management for APIs

Proper certificate management is crucial for maintaining API security and availability. Unlike web browsers where users might click through certificate warnings, API clients typically fail hard on certificate errors. This strict behavior makes proper certificate configuration and management essential for API operations.

// Node.js example of certificate configuration for API server
const https = require('https');
const fs = require('fs');
const express = require('express');

const app = express();

// Load certificates
const serverOptions = {
    key: fs.readFileSync('/path/to/private-key.pem'),
    cert: fs.readFileSync('/path/to/certificate.pem'),
    ca: fs.readFileSync('/path/to/ca-chain.pem'),
    
    // Security configurations
    ciphers: [
        'ECDHE-RSA-AES128-GCM-SHA256',
        'ECDHE-RSA-AES256-GCM-SHA384',
        'ECDHE-RSA-CHACHA20-POLY1305'
    ].join(':'),
    honorCipherOrder: true,
    minVersion: 'TLSv1.2',
    
    // Enable session resumption
    sessionTimeout: 300,
    
    // OCSP stapling
    requestOCSP: true
};

// Create HTTPS server
const server = https.createServer(serverOptions, app);

// API routes
app.get('/api/data', (req, res) => {
    res.json({ secure: true, protocol: req.protocol });
});

// Certificate monitoring endpoint
app.get('/api/cert-info', (req, res) => {
    const cert = req.connection.getPeerCertificate();
    res.json({
        issuer: cert.issuer,
        subject: cert.subject,
        validFrom: cert.valid_from,
        validTo: cert.valid_to,
        remainingDays: Math.floor((new Date(cert.valid_to) - new Date()) / (1000 * 60 * 60 * 24))
    });
});

server.listen(443, () => {
    console.log('Secure API server running on https://localhost:443');
});

Automated certificate renewal prevents the most common cause of API outages: expired certificates. Implement Let's Encrypt with automatic renewal for public-facing APIs. Use ACME protocol clients like Certbot or Caddy that handle renewal automatically. For internal APIs, integrate with your organization's PKI infrastructure for automated certificate lifecycle management.

Certificate transparency monitoring helps detect unauthorized certificates issued for your API domains. Monitor CT logs for certificates matching your domains and alert on unexpected issuances. This monitoring can detect compromise of certificate authorities or DNS hijacking attempts. Implement CAA records to restrict which CAs can issue certificates for your domains.