--- 1/draft-ietf-uta-xmpp-04.txt 2015-01-23 19:14:52.601679999 -0800 +++ 2/draft-ietf-uta-xmpp-05.txt 2015-01-23 19:14:52.621680481 -0800 @@ -1,20 +1,20 @@ Network Working Group P. Saint-Andre Internet-Draft &yet Updates: 6120 (if approved) T. Alkemade Intended status: Standards Track -Expires: May 30, 2015 November 26, 2014 +Expires: July 27, 2015 January 23, 2015 Use of Transport Layer Security (TLS) in the Extensible Messaging and Presence Protocol (XMPP) - draft-ietf-uta-xmpp-04 + draft-ietf-uta-xmpp-05 Abstract This document provides recommendations for the use of Transport Layer Security (TLS) in the Extensible Messaging and Presence Protocol (XMPP). This document updates RFC 6120. Status of This Memo This Internet-Draft is submitted in full conformance with the @@ -23,25 +23,25 @@ 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 May 30, 2015. + This Internet-Draft will expire on July 27, 2015. Copyright Notice - Copyright (c) 2014 IETF Trust and the persons identified as the + Copyright (c) 2015 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 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 @@ -132,46 +132,51 @@ Stream Management extension; see [XEP-0198] for further details. 3.4. Authenticated Connections Both the core XMPP specification [RFC6120] and the "CertID" specification [RFC6125] provide recommendations and requirements for certificate validation in the context of authenticated connections. This document does not supersede those specifications. Wherever possible, it is best to prefer authenticated connections (along with SASL [RFC4422]), as already stated in the core XMPP specification - [RFC6120]. In particular, clients MUST authenticate servers. - Because this document does not mandate that servers need to - authenticate peer servers, unauthenticated server-to-server - connections are allowed (consistent with current practice on the XMPP - network). + [RFC6120]. In particular, clients MUST authenticate servers and + servers MUST authenticate clients. This document does not mandate + that servers need to authenticate peer servers (see next section). This document does not modify the recommendations in [RFC6120] regarding the Subject Alternative Names (or other certificate details) that need to be supported for authentication of XMPP - connections. + connections using PKIX certificates. + + The Domain Name Associations (DNA) specification [I-D.ietf-xmpp-dna] + describes a framework for XMPP server authentication methods, which + include not only PKIX but also DNS-Based Authentication of Named + Entities (DANE) as defined in [I-D.ietf-dane-srv] and PKIX over + Secure HTTP (POSH) as defined in [I-D.ietf-xmpp-posh]. 3.5. Unauthenticated Connections Given the pervasiveness of passive eavesdropping, even an unauthenticated connection might be better than an unencrypted connection (this is similar to the "better than nothing security" - approach for IPsec [RFC5386]). In particular, because of current - deployment challenges for authenticated connections between XMPP - servers (see [I-D.ietf-xmpp-dna] and [I-D.ietf-xmpp-posh] for - details), it can be reasonable for XMPP server implementations to - accept unauthenticated connections when the Server Dialback protocol - [XEP-0220] is used for weak identity verification; this will at least - enable encryption of server-to-server connections. Unauthenticated - connections include connections negotiated using anonymous Diffie- - Hellman algorithms or using self-signed certificates, among other - scenarios. + approach for IPsec [RFC5386]). Unauthenticated connections include + connections negotiated using anonymous Diffie-Hellman algorithms or + using self-signed certificates, among other scenarios. In + particular, because of current deployment challenges for + authenticated connections between XMPP servers (see + [I-D.ietf-xmpp-dna] and [I-D.ietf-xmpp-posh] for details), it can be + reasonable for XMPP server implementations to accept unauthenticated + connections when Server Dialback keys [XEP-0220] are used; although + such keys on their own provide only weak identity verification (made + stronger through the use of DNSSEC [RFC4033]), this at least enables + encryption of server-to-server connections. 3.6. Server Name Indication Although there is no harm in supporting the TLS Server Name Indication (SNI) extension [RFC6066], this is not necessary since the same function is served in XMPP by the 'to' address of the initial stream header as explained in Section 4.7.2 of [RFC6120]. 3.7. Human Factors @@ -196,21 +201,21 @@ This document requests no actions of the IANA. 5. Security Considerations The use of TLS can help limit the information available for correlation to the network and transport layer headers as opposed to the application layer. As typically deployed, XMPP technologies do not leave application-layer routing data (such as XMPP 'to' and 'from' addresses) at rest on intermediate systems, since there is only one hop between any two given XMPP servers. As a result, - encrypting all hops (sending client to sender's server, sender's + encrypting all hops (sender's client to sender's server, sender's server to recipient's server, recipient's server to recipient's client) can help to limit the amount of "metadata" that might leak. It is possible that XMPP servers themselves might be compromised. In that case, per-hop encryption would not protect XMPP communications, and even end-to-end encryption of (parts of) XMPP stanza payloads would leave addressing information and XMPP roster data in the clear. By the same token, it is possible that XMPP clients (or the end-user devices on which such clients are installed) could also be compromised, leaving users utterly at the mercy of an adversary. @@ -223,21 +228,21 @@ encryption technologies will serve to protect XMPP communications to a measurable degree, compared to the alternatives. 6. References 6.1. Normative References [I-D.ietf-uta-tls-bcp] Sheffer, Y., Holz, R., and P. Saint-Andre, "Recommendations for Secure Use of TLS and DTLS", draft- - ietf-uta-tls-bcp-07 (work in progress), November 2014. + ietf-uta-tls-bcp-08 (work in progress), December 2014. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4949] Shirey, R., "Internet Security Glossary, Version 2", RFC 4949, August 2007. [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, August 2008. @@ -245,39 +250,49 @@ Protocol (XMPP): Core", RFC 6120, March 2011. [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS)", RFC 6125, March 2011. 6.2. Informative References + [I-D.ietf-dane-srv] + Finch, T., Miller, M., and P. Saint-Andre, "Using DNS- + Based Authentication of Named Entities (DANE) TLSA records + with SRV and MX records.", draft-ietf-dane-srv-08 (work in + progress), October 2014. + [I-D.ietf-uta-tls-attacks] Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing Current Attacks on TLS and DTLS", draft-ietf-uta-tls- attacks-05 (work in progress), October 2014. [I-D.ietf-xmpp-dna] Saint-Andre, P. and M. Miller, "Domain Name Associations (DNA) in the Extensible Messaging and Presence Protocol (XMPP)", draft-ietf-xmpp-dna-08 (work in progress), October 2014. [I-D.ietf-xmpp-posh] Miller, M. and P. Saint-Andre, "PKIX over Secure HTTP (POSH)", draft-ietf-xmpp-posh-02 (work in progress), October 2014. [RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence Protocol (XMPP): Core", RFC 3920, October 2004. + [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. + Rose, "DNS Security Introduction and Requirements", RFC + 4033, March 2005. + [RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and Security Layer (SASL)", RFC 4422, June 2006. [RFC5386] Williams, N. and M. Richardson, "Better-Than-Nothing Security: An Unauthenticated Mode of IPsec", RFC 5386, November 2008. [RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions: Extension Definitions", RFC 6066, January 2011.