Web Application Security Fundamentals #09: HTTPS, TLS, & Certificate Security

HTTPS (HTTP Secure) = HTTP + TLS encryption. Melindungi confidentiality (eavesdropping), integrity (tampering), dan authenticity (impersonation) data in transit.

Tujuan Pembelajaran

• Memahami TLS 1.2 vs 1.3 (handshake, cipher suites)
• Certificate management (self-signed, CA-signed, renewal)
• HSTS (HTTP Strict Transport Security)
• Certificate pinning
• Testing TLS configuration

HTTPS Setup

Self-Signed Certificate (Development)

# Generate private key + certificate
openssl req -x509 -newkey rsa:2048 -keyout key.pem -out cert.pem -days 365 -nodes

# Start HTTPS server
python3 -m http.server 8443 --certificate cert.pem --key key.pem

CA-Signed Certificate (Production)

# Generate Certificate Signing Request (CSR)
openssl req -new -key key.pem -out csr.pem

# Submit to CA (Let's Encrypt, GlobalSign, etc)
# Receive certificate signed by trusted CA
# Configure server:

# nginx config
server {
    listen 443 ssl http2;
    server_name api.example.com;
    
    ssl_certificate /etc/ssl/certs/cert.pem;
    ssl_certificate_key /etc/ssl/private/key.pem;
    
    # TLS 1.2+
    ssl_protocols TLSv1.2 TLSv1.3;
    
    # Strong ciphers
    ssl_ciphers HIGH:!aNULL:!MD5;
    ssl_prefer_server_ciphers on;
    
    # HSTS
    add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
    
    # Redirect HTTP to HTTPS
    if ($scheme != "https") {
        return 301 https://$server_name$request_uri;
    }
    
    # ... rest of config
}

Certificate Validation

# ❌ VULNERABLE - No certificate validation
import requests
response = requests.get('https://api.example.com', verify=False)

# ✅ SECURE - Validate certificate
response = requests.get('https://api.example.com', verify=True)
# verify=True (default) checks:
# - Certificate chain validity
# - Hostname match
# - Not expired

HSTS (HTTP Strict Transport Security)

Strict-Transport-Security: max-age=31536000; includeSubDomains; preload

max-age=31536000  : 1 year (browser remember)
includeSubDomains : Apply to subdomains too
preload           : Include dalam HSTS preload list

Impact:

• Browser automatically upgrade HTTP → HTTPS
• No insecure redirects
• Prevent session cookie theft via network downgrade

Certificate Pinning

Hardcode expected certificate pub key di app. Mencegah MITM via rogue CA:

// iOS certificate pinning
func urlSession(_ session: URLSession, didReceive challenge: URLAuthenticationChallenge,
                completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {
    
    guard let cert = challenge.protectionSpace.serverTrust else {
        completionHandler(.cancelAuthenticationChallenge, nil)
        return
    }
    
    let pubKey = SecCertificateCopyPublicKey(SecTrustGetCertificateAtIndex(cert, 0)!)
    let expectedKey = "my-pinned-public-key-base64"  // Hardcoded
    
    if publicKeyMatches(pubKey, expectedKey) {
        completionHandler(.useCredential, URLCredential(trust: cert))
    } else {
        completionHandler(.cancelAuthenticationChallenge, nil)
    }
}

Testing TLS Configuration

# Check TLS version
curl -I --tlsv1.2 https://api.example.com
# Should work for TLS 1.2+

# Check ciphers
echo | openssl s_client -connect api.example.com:443 2>&1 | grep "Cipher"

# Test for vulnerabilities
nmap --script ssl-enum-ciphers -p 443 api.example.com

# Online tool
https://www.ssllabs.com/ssltest/

Checklist

• [ ] HTTPS untuk all endpoints
• [ ] HTTP redirects to HTTPS
• [ ] Valid certificate (not self-signed in production)
• [ ] HSTS header set (max-age ≥ 31536000)
• [ ] TLS 1.2+ (disable older protocols)
• [ ] Strong cipher suites
• [ ] Certificate renewed before expiry
• [ ] No pinning issues on certificate renewal

Kesimpulan

HTTPS adalah table stakes. Tanpa TLS, semua data di-transmit plaintext → attackers dapat intercept, modify, forge.

Modul berikutnya (#10) membahas Security Headers.

Next: #10 - Security Headers (CSP, X-Frame-Options, etc)