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SSL/TLS / SASL

SSL/TLS (Tranport Layer Security)​

Transport Layer Security (TLS), and its now-deprecated predecessor, Secure Sockets Layer(SSL), are cryptographic protocols designed to provide communications security over a computer network.Several versions of the protocols find widespread use in applications such as web browsing, email, instant messaging, and voice over IP(VoIP).Websites can use TLS to secure all communications between their servers and web browsers.

The TLS protocol aims primarily to provide privacy and data integrity between two or more communicating computer applications.When secured by TLS, connections between a client (e.g., a web browser) and a server (e.g., wikipedia.org) should have one or more of the following properties:

  • The connection is private (or secure) because symmetric cryptography is used to encrypt the data transmitted. The keys for this symmetric encryption are generated uniquely for each connection and are based on a shared secret that was negotiated at the start of the session. The server and client negotiate the details of which encryption algorithm and cryptographic keys to use before the first byte of data is transmitted. The negotiation of a shared secret is both secure (the negotiated secret is unavailable to eavesdroppers and cannot be obtained, even by an attacker who places themselves in the middle of the connection) and reliable (no attacker can modify the communications during the negotiation without being detected).
  • The identity of the communicating parties can beauthenticatedusing public-key cryptography. This authentication can be made optional, but is generally required for at least one of the parties (typically the server).
  • The connection isreliablebecause each message transmitted includes a message integrity check using a message authentication code to prevent undetected loss or alteration of the data during transmission.

https://en.wikipedia.org/wiki/Transport_Layer_Security

Simple Authentication and Security Layer (SASL) is​

Simple Authentication and Security Layer (SASL) is an Internet Engineering Task Force standard (RFC 4422) framework for authentication and optional data security in connection-oriented protocols. It decouples mechanisms from applications, enabling secure authentication via methods like CRAM-MD5, GSSAPI, and SCRAM. Beyond authentication, SASL optionally provides a security layer ensuring data integrity and confidentiality.

Key Aspects of SASL Security Layer​

  • Framework for Authentication: SASL allows application protocols (e.g., SMTP, IMAP, LDAP, Kafka) to delegate authentication to various mechanisms.
  • Security Layer Negotiation: After authentication, SASL can establish a security layer (using mechanisms like DIGEST-MD5) to protect subsequent communication.
  • Data Protection (QOP): The negotiated Quality-of-Protection (QOP) can provide data integrity (ensuring data hasn't been tempered) and confidentiality (encryption).
  • Common Mechanisms: Popular mechanisms include PLAIN, LOGIN, CRAM-MD5, DIGEST-MD5, and GSSAPI (Kerberos).
  • Implementation: In Java, SASL providers are registered with the Java Cryptography Architecture (JCA).

How a SASL Session Works​

  1. Client Request: The client connects and requests authentication, often listing supported mechanisms.
  2. Server Response: The server responds with supported mechanisms.
  3. Mechanism Selection: The client selects a mechanism and initiates the exchange.
  4. Authentication Exchange: A series of challenges and responses occur.
  5. Security Layer: If supported, a security layer is established for the session.

Commonly used with Transport Layer Security (TLS), SASL provides a flexible, robust method for securing application-level communication.

Introduction to Simple Authentication Security Layer (SASL) - Developer's Guide to Oracle Solaris 11 Security

Simple Authentication and Security Layer - Wikipedia

SSL vs SASL_SSL​

SSL (or TLS) provides encryption and certificate-based authentication to secure data in transit, ideal for straightforward, secure connections. SASL_SSL combines SASL (Simple Authentication and Security Layer) for flexible user-based authentication with SSL encryption, making it ideal for enterprise environments requiring Kerberos, LDAP, or SCRAM authentication over a secure channel.

Key Differences​

  • Authentication Method: SSL uses X.509 certificates to authenticate, while SASL_SSL uses username/password (PLAIN/SCRAM) or Kerberos (GSSAPI).
  • Security Level: Both provide encryption. However, SASL_SSL ensures authenticated access control, whereas raw SSL only verifies that the client has a valid certificate.
  • Use Case: SSL is common for cloud/simple deployments. SASL_SSL is standard for enterprise security, requiring integration with authentication servers.
  • Complexity: SSL requires certificate management (keystores/truststores). SASL_SSL requires managing authentication secrets (e.g., JAAS files) in addition to SSL certificates.

When to use which?​

  • Use SSL: If you only need encryption and basic certificate authentication (e.g., mutual TLS).
  • Use SASL_SSL: If you need to enforce user-level access control, integrate with Active Directory/Kerberos, or use SCRAM/PLAIN mechanisms.