TRAM P. Patil Internet-Draft T. Reddy Intended status: Standards Track G. Salgueiro Expires: April 9, 2015 Cisco M. Petit-Huguenin Impedance Mismatch October 6, 2014 Application Layer Protocol Negotiation (ALPN) labels for Session Traversal Utilities for NAT (STUN) Usages draft-ietf-tram-alpn-06 Abstract Application Layer Protocol Negotiation (ALPN) labels for Session Traversal Utilities for NAT (STUN) usages, such as Traversal Using Relays around NAT (TURN) and NAT discovery, are defined in this document to allow an application layer negotiate STUN usages within the Transport Layer Security (TLS) connection. ALPN protocol identifiers defined in this document apply to both TLS and Datagram Transport Layer Security (DTLS). 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 April 9, 2015. Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. 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 Patil, et al. Expires April 9, 2015 [Page 1] Internet-Draft ALPN for STUN/TURN October 2014 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 2. ALPN Labels for STUN . . . . . . . . . . . . . . . . . . . . 3 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 6.1. Normative References . . . . . . . . . . . . . . . . . . 4 6.2. Informative References . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction STUN can be securely transported using TLS-over-TCP (referred to as TLS [RFC5246]), as specified in [RFC5389], or TLS-over-UDP (referred to as DTLS [RFC6347]), as specified in [RFC7350]. ALPN [RFC7301] enables an endpoint to positively identify an application protocol in TLS/DTLS and distinguish it from other TLS/ DTLS protocols. With ALPN, the client sends the list of supported application protocols as part of the TLS/DTLS ClientHello message. The server chooses a protocol and sends the selected protocol as part of the TLS/DTLS ServerHello message. Application protocol negotiation can thus be accomplished within the TLS/DTLS handshake, without adding network round-trips. STUN protocol usages, such as TURN [RFC5766], can be used to identify the purpose of a flow without initiating a session. This capability is useful and adds efficiency, as shown in the following scenarios. 1. Consider an Enterprise network that deploys a TURN server in a DeMilitarized Zone (DMZ) to audit all media sessions from inside the Enterprise premises to any external peer. In this deployment, an Enterprise firewall could use the TURN ALPN identifier to detect the use of a TURN server that is outside the Enterprise domain (i.e., a TURN server provided by an application server, access network, etc). 2. If a firewall is configured to block all outgoing traffic except for TCP traffic to specific ports (e.g., 443 for HTTPS), a TURN Patil, et al. Expires April 9, 2015 [Page 2] Internet-Draft ALPN for STUN/TURN October 2014 server listening on its default ports (3478 for TCP/UDP, 5349 for TLS) would not be reachable. However, despite the restrictions imposed by the firewall, a TURN server can still be reached on the allowed HTTPS port if the TURN ALPN identifier is used to establish usage of TURN as part of the TLS handshake. This document defines entries in the "Application Layer Protocol Negotiation (ALPN) Protocol IDs" registry established by [RFC7301] to identify STUN protocol usages. 2. ALPN Labels for STUN The document proposes the following ALPN labels to identify STUN protocol [RFC5389] usages. 'stun.turn': Label to identify the specific use of STUN over (D)TLS for TURN (Section 4.6 of [RFC7350]). 'stun.nat-discovery': Label to identify the specific use of STUN over (D)TLS for NAT discovery (Section 4.1 of [RFC7350]). 3. IANA Considerations The following entries are to be added to the "Application Layer Protocol Negotiation (ALPN) Protocol IDs" registry established by [RFC7301]. The "stun.turn" label identifies the use of TURN usage (D)TLS: Protocol: Traversal Using Relays around NAT (TURN) Identification Sequence: 0x73 0x74 0x75 0x6E 0x2E 0x74 0x75 0x72 0x6E ("stun.turn") Specification: This document (RFCXXXX) The "stun.nat-discovery" label identifies the use of STUN for the purposes of NAT discovery over (D)TLS: Protocol: NAT discovery using Session Traversal Utilities for NAT (STUN) Identification Sequence: 0x73 0x74 0x75 0x6E 0x2E 0x6e 0x61 0x74 0x2d 0x64 0x69 0x73 0x63 0x6f 0x76 0x65 0x72 0x79 ("stun.nat- discovery") Specification: This document (RFCXXXX) Patil, et al. Expires April 9, 2015 [Page 3] Internet-Draft ALPN for STUN/TURN October 2014 4. Security Considerations The ALPN STUN protocol identifier does not introduce any specific security considerations beyond those detailed in the TLS ALPN Extension specification [RFC7301]. It also does not impact security of TLS/DTLS session establishment nor application data exchange. 5. Acknowledgements This work benefited from the discussions and invaluable input by the various members of the TRAM working group. These include Simon Perrault, Paul Kyzivat, Brandon Williams and Andrew Hutton. Special thanks to Martin Thomson and Oleg Moskalenko for their constructive comments, suggestions, and early reviews that were critical to the formulation and refinement of this document. 6. References 6.1. Normative References [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. [RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, "Session Traversal Utilities for NAT (STUN)", RFC 5389, October 2008. [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer Security Version 1.2", RFC 6347, January 2012. [RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan, "Transport Layer Security (TLS) Application-Layer Protocol Negotiation Extension", RFC 7301, July 2014. [RFC7350] Petit-Huguenin, M. and G. Salgueiro, "Datagram Transport Layer Security (DTLS) as Transport for Session Traversal Utilities for NAT (STUN)", RFC 7350, August 2014. 6.2. Informative References [RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using Relays around NAT (TURN): Relay Extensions to Session Traversal Utilities for NAT (STUN)", RFC 5766, April 2010. Patil, et al. Expires April 9, 2015 [Page 4] Internet-Draft ALPN for STUN/TURN October 2014 Authors' Addresses Prashanth Patil Cisco Systems, Inc. Bangalore India Email: praspati@cisco.com Tirumaleswar Reddy Cisco Systems, Inc. Cessna Business Park, Varthur Hobli Sarjapur Marathalli Outer Ring Road Bangalore, Karnataka 560103 India Email: tireddy@cisco.com Gonzalo Salgueiro Cisco Systems, Inc. 7200-12 Kit Creek Road Research Triangle Park, NC 27709 US Email: gsalguei@cisco.com Marc Petit-Huguenin Impedance Mismatch USA Email: marc@petit-huguenin.org Patil, et al. Expires April 9, 2015 [Page 5]