< draft-ietf-uta-xmpp-04.txt   draft-ietf-uta-xmpp-05.txt >
Network Working Group P. Saint-Andre Network Working Group P. Saint-Andre
Internet-Draft &yet Internet-Draft &yet
Updates: 6120 (if approved) T. Alkemade Updates: 6120 (if approved) T. Alkemade
Intended status: Standards Track 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 Use of Transport Layer Security (TLS) in the Extensible Messaging and
Presence Protocol (XMPP) Presence Protocol (XMPP)
draft-ietf-uta-xmpp-04 draft-ietf-uta-xmpp-05
Abstract Abstract
This document provides recommendations for the use of Transport Layer This document provides recommendations for the use of Transport Layer
Security (TLS) in the Extensible Messaging and Presence Protocol Security (TLS) in the Extensible Messaging and Presence Protocol
(XMPP). This document updates RFC 6120. (XMPP). This document updates RFC 6120.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." 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 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. document authors. All rights reserved.
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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Stream Management extension; see [XEP-0198] for further details. Stream Management extension; see [XEP-0198] for further details.
3.4. Authenticated Connections 3.4. Authenticated Connections
Both the core XMPP specification [RFC6120] and the "CertID" Both the core XMPP specification [RFC6120] and the "CertID"
specification [RFC6125] provide recommendations and requirements for specification [RFC6125] provide recommendations and requirements for
certificate validation in the context of authenticated connections. certificate validation in the context of authenticated connections.
This document does not supersede those specifications. Wherever This document does not supersede those specifications. Wherever
possible, it is best to prefer authenticated connections (along with possible, it is best to prefer authenticated connections (along with
SASL [RFC4422]), as already stated in the core XMPP specification SASL [RFC4422]), as already stated in the core XMPP specification
[RFC6120]. In particular, clients MUST authenticate servers. [RFC6120]. In particular, clients MUST authenticate servers and
Because this document does not mandate that servers need to servers MUST authenticate clients. This document does not mandate
authenticate peer servers, unauthenticated server-to-server that servers need to authenticate peer servers (see next section).
connections are allowed (consistent with current practice on the XMPP
network).
This document does not modify the recommendations in [RFC6120] This document does not modify the recommendations in [RFC6120]
regarding the Subject Alternative Names (or other certificate regarding the Subject Alternative Names (or other certificate
details) that need to be supported for authentication of XMPP 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 3.5. Unauthenticated Connections
Given the pervasiveness of passive eavesdropping, even an Given the pervasiveness of passive eavesdropping, even an
unauthenticated connection might be better than an unencrypted unauthenticated connection might be better than an unencrypted
connection (this is similar to the "better than nothing security" connection (this is similar to the "better than nothing security"
approach for IPsec [RFC5386]). In particular, because of current approach for IPsec [RFC5386]). Unauthenticated connections include
deployment challenges for authenticated connections between XMPP connections negotiated using anonymous Diffie-Hellman algorithms or
servers (see [I-D.ietf-xmpp-dna] and [I-D.ietf-xmpp-posh] for using self-signed certificates, among other scenarios. In
details), it can be reasonable for XMPP server implementations to particular, because of current deployment challenges for
accept unauthenticated connections when the Server Dialback protocol authenticated connections between XMPP servers (see
[XEP-0220] is used for weak identity verification; this will at least [I-D.ietf-xmpp-dna] and [I-D.ietf-xmpp-posh] for details), it can be
enable encryption of server-to-server connections. Unauthenticated reasonable for XMPP server implementations to accept unauthenticated
connections include connections negotiated using anonymous Diffie- connections when Server Dialback keys [XEP-0220] are used; although
Hellman algorithms or using self-signed certificates, among other such keys on their own provide only weak identity verification (made
scenarios. stronger through the use of DNSSEC [RFC4033]), this at least enables
encryption of server-to-server connections.
3.6. Server Name Indication 3.6. Server Name Indication
Although there is no harm in supporting the TLS Server Name Although there is no harm in supporting the TLS Server Name
Indication (SNI) extension [RFC6066], this is not necessary since the Indication (SNI) extension [RFC6066], this is not necessary since the
same function is served in XMPP by the 'to' address of the initial same function is served in XMPP by the 'to' address of the initial
stream header as explained in Section 4.7.2 of [RFC6120]. stream header as explained in Section 4.7.2 of [RFC6120].
3.7. Human Factors 3.7. Human Factors
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This document requests no actions of the IANA. This document requests no actions of the IANA.
5. Security Considerations 5. Security Considerations
The use of TLS can help limit the information available for The use of TLS can help limit the information available for
correlation to the network and transport layer headers as opposed to correlation to the network and transport layer headers as opposed to
the application layer. As typically deployed, XMPP technologies do the application layer. As typically deployed, XMPP technologies do
not leave application-layer routing data (such as XMPP 'to' and not leave application-layer routing data (such as XMPP 'to' and
'from' addresses) at rest on intermediate systems, since there is 'from' addresses) at rest on intermediate systems, since there is
only one hop between any two given XMPP servers. As a result, 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 server to recipient's server, recipient's server to recipient's
client) can help to limit the amount of "metadata" that might leak. client) can help to limit the amount of "metadata" that might leak.
It is possible that XMPP servers themselves might be compromised. In It is possible that XMPP servers themselves might be compromised. In
that case, per-hop encryption would not protect XMPP communications, that case, per-hop encryption would not protect XMPP communications,
and even end-to-end encryption of (parts of) XMPP stanza payloads and even end-to-end encryption of (parts of) XMPP stanza payloads
would leave addressing information and XMPP roster data in the clear. 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 By the same token, it is possible that XMPP clients (or the end-user
devices on which such clients are installed) could also be devices on which such clients are installed) could also be
compromised, leaving users utterly at the mercy of an adversary. compromised, leaving users utterly at the mercy of an adversary.
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encryption technologies will serve to protect XMPP communications to encryption technologies will serve to protect XMPP communications to
a measurable degree, compared to the alternatives. a measurable degree, compared to the alternatives.
6. References 6. References
6.1. Normative References 6.1. Normative References
[I-D.ietf-uta-tls-bcp] [I-D.ietf-uta-tls-bcp]
Sheffer, Y., Holz, R., and P. Saint-Andre, Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of TLS and DTLS", draft- "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 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", RFC [RFC4949] Shirey, R., "Internet Security Glossary, Version 2", RFC
4949, August 2007. 4949, August 2007.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008. (TLS) Protocol Version 1.2", RFC 5246, August 2008.
skipping to change at page 6, line 19 skipping to change at page 6, line 22
Protocol (XMPP): Core", RFC 6120, March 2011. Protocol (XMPP): Core", RFC 6120, March 2011.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509 within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer (PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, March 2011. Security (TLS)", RFC 6125, March 2011.
6.2. Informative References 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] [I-D.ietf-uta-tls-attacks]
Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing Sheffer, Y., Holz, R., and P. Saint-Andre, "Summarizing
Current Attacks on TLS and DTLS", draft-ietf-uta-tls- Current Attacks on TLS and DTLS", draft-ietf-uta-tls-
attacks-05 (work in progress), October 2014. attacks-05 (work in progress), October 2014.
[I-D.ietf-xmpp-dna] [I-D.ietf-xmpp-dna]
Saint-Andre, P. and M. Miller, "Domain Name Associations Saint-Andre, P. and M. Miller, "Domain Name Associations
(DNA) in the Extensible Messaging and Presence Protocol (DNA) in the Extensible Messaging and Presence Protocol
(XMPP)", draft-ietf-xmpp-dna-08 (work in progress), (XMPP)", draft-ietf-xmpp-dna-08 (work in progress),
October 2014. October 2014.
[I-D.ietf-xmpp-posh] [I-D.ietf-xmpp-posh]
Miller, M. and P. Saint-Andre, "PKIX over Secure HTTP Miller, M. and P. Saint-Andre, "PKIX over Secure HTTP
(POSH)", draft-ietf-xmpp-posh-02 (work in progress), (POSH)", draft-ietf-xmpp-posh-02 (work in progress),
October 2014. October 2014.
[RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence [RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 3920, October 2004. 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 [RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and
Security Layer (SASL)", RFC 4422, June 2006. Security Layer (SASL)", RFC 4422, June 2006.
[RFC5386] Williams, N. and M. Richardson, "Better-Than-Nothing [RFC5386] Williams, N. and M. Richardson, "Better-Than-Nothing
Security: An Unauthenticated Mode of IPsec", RFC 5386, Security: An Unauthenticated Mode of IPsec", RFC 5386,
November 2008. November 2008.
[RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions: [RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions:
Extension Definitions", RFC 6066, January 2011. Extension Definitions", RFC 6066, January 2011.
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