SSL Cheat Sheet

Here’s a cheat sheet for SSL (Secure Sockets Layer) and its successor, TLS (Transport Layer Security), which are cryptographic protocols designed to provide communication security over a computer network.

Key Concepts

SSL/TLS:

  • SSL is the predecessor to TLS.
  • TLS is the modern and more secure version.
  • Both are cryptographic protocols for secure communication.

SSL/TLS Handshake

  • ClientHello:
    • Client initiates communication and specifies supported cryptographic algorithms.
  • ServerHello:
    • Server responds with selected cryptographic algorithms and digital certificate (if required).
  • Key Exchange:
    • Server and client exchange key information securely.
  • Finished:
    • Both parties confirm the establishment of a secure connection.

Certificates

  • Digital Certificate:
    • Issued by a Certificate Authority (CA).
    • Contains public key and information about the entity.
  • Certificate Chain:
    • A sequence of certificates, starting from the server’s certificate and ending at a trusted root certificate.

Cipher Suites

  • Definition:
    • A combination of key exchange algorithm, encryption algorithm, and message authentication code.
  • Common Cipher Suites:
    • TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
    • TLS_RSA_WITH_AES_128_CBC_SHA256

Perfect Forward Secrecy (PFS)

  • Definition:
    • Ensures that a compromise of long-term keys doesn’t compromise past session keys.
  • Cipher Suites for PFS:
    • TLS_ECDHE_*
    • TLS_DHE_*

TLS Versions

  • TLS 1.0, 1.1, 1.2, 1.3:
    • Use the latest TLS version for security.
    • TLS 1.0 and 1.1 are considered insecure and deprecated.

SSL/TLS Tools

  • OpenSSL:
    • A versatile toolkit for SSL/TLS.
    • Generate private keys, create CSRs, and more.
  • Wireshark:
    • Analyze SSL/TLS traffic.
    • Useful for debugging and monitoring.

SSL/TLS Deployment Best Practices

  • Disable Weak Ciphers:
    • Configure servers to support only strong ciphers.
  • Keep Software Updated:
    • Regularly update SSL/TLS libraries and applications.
  • Use HSTS (HTTP Strict Transport Security):
    • Instructs web browsers to use secure connections only.
  • Implement OCSP Stapling:
    • Reduces reliance on Certificate Revocation Lists (CRLs).

Troubleshooting

  • Check Certificate Expiry:
    • Certificates have a validity period; ensure they are up to date.
  • Review Server Logs:
    • Look for SSL/TLS-related errors or warnings.
  • SSL Labs Server Test:
    • Use online tools like SSL Labs to assess your server’s SSL/TLS configuration.

Future Trends

  • TLS 1.3:
    • Provides improved security and performance.
    • Deploys a more efficient handshake and eliminates insecure algorithms.

This cheat sheet covers fundamental concepts and best practices related to SSL/TLS. Always stay informed about the latest security developments and vulnerabilities in SSL/TLS protocols.