TLS Working Group M. Badra Internet-Draft Zayed University Intended status: Standards Track December 15, 2013 Expires: June 18, 2014 Passive Transport Layer Security (TLS) Clients draft-badra-tls-passive-client-00 Abstract This document describes a technique for a Transport Layer Security (TLS) server to initiate a TLS connection to a TLS client. This is accomplished by the TLS client listening on a port number sent from the client to the server during the initial TLS Handshake. This document defines a TLS extension for conveying a port number from the client to the server. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on June 18, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. Badra Expires June 18, 2014 [Page 1] Internet-Draft Passive TLS Clients December 2013 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions Used in This Document . . . . . . . . . . . . 2 2. Extension Overview . . . . . . . . . . . . . . . . . . . . . 2 2.1. Connection Initiation from Server to Client . . . . . . . 3 3. Security Considerations . . . . . . . . . . . . . . . . . . . 3 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 5. Normative References . . . . . . . . . . . . . . . . . . . . 3 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction In the current deployments of applications running over the Transport Layer Security (TLS) [RFC5246], the clients actively open the TLS connections and the servers passively listens for the incoming TLS connection on the TCP or UDP port numbers. This document describes a technique for a TLS server to initiate a TLS connection to a TLS client. This is accomplished by the TLS client listening on a port number sent from the client to the server during the initial TLS Handshake. This document describes a TLS extension for coveying a port number from the client to the server. 1.1. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 2. Extension Overview A new extension type (passive_mode(TBD)) is defined and MAY be included by the client in its ClientHello message. For servers aware of the password extension but not wishing to use it, they will gracefully revert to an ordinary TLS handshake or stop the negotiation. Badra Expires June 18, 2014 [Page 2] Internet-Draft Passive TLS Clients December 2013 enum { passive_mode(TBD), (65535) } ExtensionType; The "extension_data" field of this extension SHALL contain: uint16 port_number; The extension_data field of a passive_mode extension in a ServerHello MUST be empty. 2.1. Connection Initiation from Server to Client Once the initial handshaking is complete, the server MAY actively open a TCP or UDP connection to the client using the port number received in the ClientHello. Once the TCP or UDP connection has been established, the client takes initiative and sends the TLS ClientHello message to begin the TLS abbreviated handshake. 3. Security Considerations The security considerations described throughout [RFC5246] apply here as well. 4. IANA Considerations This document requires IANA to update its registry of TLS extensions to assign entry TBD as passive_mode. 5. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. Author's Address Mohamad Badra Zayed University Email: mbadra@gmail.com Badra Expires June 18, 2014 [Page 3]