Using DNSSEC and DANE as a Prooftype for XMPP Delegation
draft-miller-xmpp-dnssec-prooftype-00

Network Working Group                                          M. Miller
Internet-Draft                                            P. Saint-Andre
Intended status: Standards Track                     Cisco Systems, Inc.
Expires: December 13, 2012                                  June 6, 2012

        Using DNSSEC and DANE as a Prooftype for XMPP Delegation
                 draft-miller-xmpp-dnssec-prooftype-00

Abstract

   This document defines a model for securely delegating an XMPP service
   for a domain to a host associated with a different domain.

Status of this Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on December 13, 2012.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  2
   3.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . .  2
   4.  Use of DNSSEC  . . . . . . . . . . . . . . . . . . . . . . . .  3
   5.  Use of DANE  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     5.1.  No Delegation  . . . . . . . . . . . . . . . . . . . . . .  3

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     5.2.  Insecure Delegation  . . . . . . . . . . . . . . . . . . .  4
     5.3.  Secure Delegation  . . . . . . . . . . . . . . . . . . . .  4
     5.4.  TLSA Certificate Usage 3 Considerations  . . . . . . . . .  4
   6.  Internationalization Considerations  . . . . . . . . . . . . .  4
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  4
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  5
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  6

1.  Introduction

   In the core XMPP specification [RFC6120], the domain to which an XMPP
   initiating entity wants to connect is asserted via the 'to' attribute
   of the <stream:stream> header, and the TLS certificate offered by the
   receiving server is required to match this source domain (e.g.,
   "im.example.com").  However, this model can cause problems if the
   source domain is delegated (via DNS SRV records [RFC2782]) to a host
   associated with a different domain that is derived via SRV (e.g.,
   "hosting.example.net"), since the derived domain might also be the
   delegate for a number of other source domains and, for operational
   and security reasons, a hosting server is rarely able to present a
   certificate that matches the source domain.

   Absent the use of DNS Security [RFC4033], delegation via SRV does not
   provide a strong basis for checking the derived domain rather than
   the source domain.  This document describes how the use of DNSSEC
   with SRV results in more secure delegation, such that the initiating
   XMPP server can legitimately check the derived domain rather than the
   source domain.

2.  Terminology

   This document inherits XMPP-related terminology from [RFC6120], DNS-
   related terminology from [RFC1034], [RFC1035], [RFC2782] and
   [RFC4033], and security-related terminology from [RFC4949] and
   [RFC5280].  The terms "source domain" and "derived domain" are used
   as defined in the "CertID" specification [RFC6125].

   This document is applicable to connections made from an XMPP client
   to an XMPP server ("_xmpp-client._tcp") or between XMPP servers
   ("_xmpp-server._tcp").  In both cases, the XMPP initiating entity
   acts as a TLS client and the XMPP receiving entity acts as a TLS
   server.  Therefore, to simplify discussion this document uses "_xmpp-
   client._tcp" to describe to both cases, unless otherwise indicated.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

3.  Requirements

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   An XMPP initiating entity (TLS client) that wishes to use this
   prooftype MUST do so before exchanging stanzas addressed to the
   source domain.  In general, this means the prooftype MUST be
   completed before the XMPP stream is restarted following STARTTLS
   negotiation (as specified in [RFC6120]). However, connections between
   XMPP servers MAY also use this prooftype to verify delegations of
   additional source domains onto an existing connection, such as
   multiplexing via [XEP-0220].

4.  Use of DNSSEC

   An XMPP initiating entity (TLS client) that wishes to use this
   prooftype performs the following actions:

   1.  Query for the appropriate SRV resource record for the source
       domain (e.g.  "_xmpp-client._tcp.im.example.com").

   2.  If there is no SRV resource record, pursue the fallback methods
       described in [RFC6120].

   3.  If there is an SRV resource record, validate that the SRV record
       answer is secure according to [RFC4033]; if the answer is
       insecure or bogus, then delegation to the derived domain (as
       indicated by the "target host" field) is insecure and the TLS
       client MUST verify the certificate against the source domain as
       described in [RFC6120].

   4.  If there is an SRV record, for each derived domain from the SRV
       record answer (e.g.  "hosting.example.net"), query for the "A"
       and/or "AAAA" resource records as described in [RFC6120].

   5.  For each derived domain, validate that the address record answers
       are provably secure according to [RFC4033]

   6.  If any answer is insecure or bogus, then the TLS client MUST NOT
       consider a connection to that derived domain as securely
       delegated from the source domain; when verifying the certificate,
       the TLS client MUST do so against the source domain as described
       in [RFC6120].

   7.  For each address record answer that is a provably secure, the TLS
       client SHOULD consider a connection to that derived domain as
       securely delegated; when verifying the certificate (as described
       in [RFC6125]), the TLS client SHOULD do so against the derived
       domain but MAY also verify the certificate against the source
       domain.

5.  Use of DANE

   [DANE] provides additional tools to verify the keys used in TLS
   connections.  Whether it is appropriate to use [DANE] for TLS
   certificate verification depends on the delegation status of the
   source domain, as described in the following sections.

5.1.  No Delegation

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   If the source domain has not been delegated to a derived domain,
   i.e., if the source domain and the derived domain are identical
   (e.g., "im.example.com"), then the TLS client MAY query for a TLSA
   resource record as described in [DANE], where the prepared domain
   name MUST contain the source domain and a port of 5222 for client-to-
   server streams  (e.g.  "_5222._tcp.im.example.com") or 5269 for
   server-to-server streams (e.g.  "_5269._tcp.im.example.com").

   In this case, the TLS client MUST perform certificate verification
   against the source domain as described in [RFC6120].

5.2.  Insecure Delegation

   If the delegation of a source domain to a derived domain is not
   secure, then the TLS client MUST NOT make a TLSA record query to the
   derived domain as described in [DANE].  Instead, the TLS client MUST
   perform certificate verification against the source domain as
   described in [RFC6120], and MAY make a TLSA query against the source
   domain.

5.3.  Secure Delegation

   If the source domain has been delegated to a derived domain in a
   secure manner as described under [protocol], then the TLS client
   SHOULD query for a TLSA resource record as described in [DANE], where
   the prepared domain name MUST contain the derived domain and a port
   of 5222 for client-to-server streams or 5269 for server-to-server
   streams (e.g.  "_5222._tcp.hosting.example.net").

   If no TLSA resource records exist for the specified service, then the
   TLA client MUST perform certificate verification against the source
   domain as described in [RFC6120].

   If TLSA resource records exist for the specified service, then the
   TLS client MUST perform certificate verification against the derived
   domain, using the information from the TLSA answer as the basis for
   verification as described in [DANE].

5.4.  TLSA Certificate Usage 3 Considerations

   If a TLSA resource record specifies certificate usage 3 (also known
   as "domain-issued certificate"), verification MUST NOT consider the
   source or derived domain.  Instead, the target certificate MUST match
   the TLSA record, as specified in [DANE].  If matched, the TLS
   connection MUST considered valid for the source domain regardless of
   the target certificate's information.

6.  Internationalization Considerations

   If the SRV, A/AAAA, and TLSA record queries are for an
   internationalized domain name, then they need to use the A-label form
   as defined in [RFC5890].

7.  Security Considerations

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   This document supplements but does not supersede the security
   considerations provided in [RFC4033], [RFC6120], [RFC6125], and
   [DANE].

8.  IANA Considerations

   This document has no actions for the IANA.

9.  References

   [DANE]     Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
              of Named Entities (DANE) Transport Layer Security (TLS)
              Protocol: TLSA", Internet-Draft draft-ietf-dane-
              protocol-21, May 2012.

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, November 1987.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2782]  Gulbrandsen, A., Vixie, P. and L. Esibov, "A DNS RR for
              specifying the location of services (DNS SRV)", RFC 2782,
              February 2000.

   [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D. and S.
              Rose, "DNS Security Introduction and Requirements", RFC
              4033, May 2005.

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2", RFC
              4949, August 2007.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R. and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, May 2008.

   [RFC5890]  Klensin, J., "Internationalized Domain Names for
              Applications (IDNA): Definitions and Document Framework",
              RFC 5890, August 2010.

   [RFC6120]  Saint-Andre, P., "Extensible Messaging and Presence
              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.

   [XEP-0220]

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              Miller, J, Saint-Andre, P and P Hancke, "Server Dialback",
              XSF XEP 0220, August 2011.

Authors' Addresses

   Matthew Miller
   Cisco Systems, Inc.
   1899 Wynkoop Street, Suite 600
   Denver, CO 80202
   USA
   
   Email: mamille2@cisco.com

   Peter Saint-Andre
   Cisco Systems, Inc.
   1899 Wynkoop Street, Suite 600
   Denver, CO 80202
   USA
   
   Email: psaintan@cisco.com

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