RFC 7568

RFC 7568 is a Request for Comments document published by the Internet Engineering Task Force (IETF) in June 2015. It formally declares the Transport Layer Security (TLS) protocol version 1.0 and above as the successors to the older Secure Sockets Layer (SSL) protocol. The document's primary purpose is to deprecate SSL 3.0, advising against its use in any new implementations due to inherent security vulnerabilities. This action was a direct response to the discovery of the POODLE attack, which demonstrated a critical weakness in the SSL 3.0 protocol's design.

● Introduction

The document was authored by Stephen Farrell and Kathleen Moriarty, prominent security experts within the IETF. It builds upon and updates an earlier standard, RFC 6176, which had already deprecated SSL 2.0. The introduction contextualizes the protocol's history, noting that SSL 3.0 was originally designed by Netscape Communications Corporation in the mid-1990s. While it served as the foundation for the modern TLS protocol, maintained by the IETF, its age and cryptographic design made it increasingly unsuitable for the modern internet. The publication of this Request for Comments represents a formal step in the Internet standards process to retire a vulnerable technology and guide implementers toward more secure alternatives like TLS 1.2.

● Deprecation of SSL 3.0

The core directive of the document is the explicit deprecation of SSL 3.0. Deprecation in the context of the IETF means the protocol is declared obsolete and unsuitable for further use, though it may still be implemented. The text states that SSL 3.0 MUST NOT be used, a strong normative requirement in Internet Engineering Task Force terminology. This recommendation applies to all contexts, including new implementations, existing deployments, and as a fallback protocol. The rationale is grounded in the protocol's lack of support for modern, robust cryptographic algorithms and its vulnerability to a class of attacks known as padding oracle attacks, which compromise the confidentiality of the encrypted session.

● The POODLE Attack

The immediate catalyst for the deprecation was the public disclosure of the POODLE attack (Padding Oracle On Downgraded Legacy Encryption) in October 2014 by security researchers at Google. This attack exploits a fundamental flaw in the block cipher mode used within SSL 3.0. An attacker can force a connection to downgrade from a secure protocol like TLS 1.2 to the older SSL 3.0, even if both client and server support newer versions. Once in SSL 3.0, the attacker can decrypt encrypted HTTP cookies and other sensitive data by analyzing padding bytes. The success of the POODLE attack against Google Chrome, Mozilla Firefox, and other major software demonstrated that the protocol's weaknesses were not merely theoretical but practically exploitable.

● Recommendations and Impact

RFC 7568 provides clear operational guidance, recommending that implementations disable SSL 3.0 by default and completely remove support where possible. It advocates for the exclusive use of TLS 1.0 or, preferably, later versions like TLS 1.2. The impact of this deprecation was widespread, affecting major technology companies and web standards. Organizations like the Payment Card Industry Security Standards Council (PCI SSC) updated their compliance requirements to forbid SSL 3.0. Browser vendors, including those behind Microsoft Edge, Apple Safari, and Opera, accelerated plans to remove support. The move also influenced protocols like HTTPS and frameworks used across the World Wide Web.

● IETF Process and Publication

The document was developed within the IETF's Transport Layer Security (TLS) working group, following the organization's consensus-based process. It was published as a Proposed Standard in June 2015, a status indicating solid technical consensus and implementation experience. The publication process involved review by the Internet Engineering Steering Group (IESG) and discussions on the IETF mailing lists. By issuing this Request for Comments, the IETF provided an authoritative, vendor-neutral statement that helped coordinate the global information technology industry's response to a critical security threat, phasing out a protocol that had become a liability for internet security.

Category:Internet standards Category:Computer security Category:Internet Engineering Task Force