draft-ietf-radext-dynamic-discovery-04.txt   draft-ietf-radext-dynamic-discovery-05.txt 
RADIUS Extensions Working Group S. Winter RADIUS Extensions Working Group S. Winter
Internet-Draft RESTENA Internet-Draft RESTENA
Intended status: Experimental M. McCauley Intended status: Experimental M. McCauley
Expires: December 30, 2012 OSC Expires: June 16, 2013 OSC
June 28, 2012 December 13, 2012
NAI-based Dynamic Peer Discovery for RADIUS/TLS and RADIUS/DTLS NAI-based Dynamic Peer Discovery for RADIUS/TLS and RADIUS/DTLS
draft-ietf-radext-dynamic-discovery-04 draft-ietf-radext-dynamic-discovery-05
Abstract Abstract
This document specifies a means to find authoritative RADIUS servers This document specifies a means to find authoritative RADIUS servers
for a given realm. It can be used in conjunction with RADIUS/TLS and for a given realm. It can be used in conjunction with RADIUS/TLS and
RADIUS/DTLS. RADIUS/DTLS.
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 December 30, 2012. This Internet-Draft will expire on June 16, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. DNS-based NAPTR/SRV Peer Discovery . . . . . . . . . . . . . . 3 2. DNS-based NAPTR/SRV Peer Discovery . . . . . . . . . . . . . . 3
2.1. Applicability . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Applicability . . . . . . . . . . . . . . . . . . . . . . 3
2.2. DNS RR definition . . . . . . . . . . . . . . . . . . . . 3 2.2. DNS RR definition . . . . . . . . . . . . . . . . . . . . 3
2.3. Realm to AAA server resolution algorithm . . . . . . . . . 5 2.3. Realm to RADIUS server resolution algorithm . . . . . . . 6
2.3.1. Input . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3.1. Input . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3.2. Output . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3.2. Output . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3.3. Algorithm . . . . . . . . . . . . . . . . . . . . . . 6 2.3.3. Algorithm . . . . . . . . . . . . . . . . . . . . . . 7
2.3.4. Validity of results . . . . . . . . . . . . . . . . . 7 2.3.4. Validity of results . . . . . . . . . . . . . . . . . 8
2.3.5. Delay considerations . . . . . . . . . . . . . . . . . 8 2.3.5. Delay considerations . . . . . . . . . . . . . . . . . 9
2.3.6. Example . . . . . . . . . . . . . . . . . . . . . . . 8 2.3.6. Example . . . . . . . . . . . . . . . . . . . . . . . 9
3. Security Considerations . . . . . . . . . . . . . . . . . . . 10 3. Security Considerations . . . . . . . . . . . . . . . . . . . 11
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
5. Normative References . . . . . . . . . . . . . . . . . . . . . 10 5. Normative References . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction 1. Introduction
1.1. Requirements Language 1.1. Requirements Language
In this document, several words are used to signify the requirements In this document, several words are used to signify the requirements
of the specification. The key words "MUST", "MUST NOT", "REQUIRED", of the specification. The key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" in this document are to be interpreted as described in and "OPTIONAL" in this document are to be interpreted as described in
RFC 2119. [RFC2119] RFC 2119. [RFC2119]
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Furthermore, it is only applicable for new user sessions, i.e. for Furthermore, it is only applicable for new user sessions, i.e. for
the initial Access-Request. Subsequent messages concerning this the initial Access-Request. Subsequent messages concerning this
session, for example Access-Challenges and Access-Accepts use the session, for example Access-Challenges and Access-Accepts use the
previously-established communication channel between client and previously-established communication channel between client and
server. server.
2.2. DNS RR definition 2.2. DNS RR definition
DNS definitions of RADIUS/TLS servers can be either S-NAPTR records DNS definitions of RADIUS/TLS servers can be either S-NAPTR records
(see [RFC3958]) or SRV records. When both are defined, the (see [RFC3958]) or SRV records. When both are defined, the
resolution algorithm prefers S-NAPTR results (see section Section 2.3 resolution algorithm prefers S-NAPTR results (see Section 2.3 below).
below).
This specification defines three S-NAPTR service tags: "aaa+auth", This specification defines three S-NAPTR service tags:
"aaa+acct" and "aaa+dynauth". This specification defines two S-NAPTR
protocol tags: "radius.tls" for RADIUS/TLS [RFC6614] and +-----------------+-----------------------------------------+
"radius.dtls" for RADIUS/DTLS [I-D.dekok-radext-dtls]. | Service Tag | Use |
+-----------------+-----------------------------------------+
| aaa+auth | RADIUS Authentication, i.e. traffic as |
| | defined in [RFC2865] |
| - - - - - - - - | - - - - - - - - - - - - - - - - - - - - |
| aaa+acct | RADIUS Accounting, i.e. traffic as |
| | defined in [RFC2866] |
| - - - - - - - - | - - - - - - - - - - - - - - - - - - - - |
| aaa+dynauth | RADIUS Dynamic Authorisation, i.e. |
| | traffic as defined in [RFC5176] |
+--------------- --+-----------------------------------------+
Figure 1: List of Service Tags
This specification defines two S-NAPTR protocol tags:
+-----------------+-----------------------------------------+
| Protocol Tag | Use |
+-----------------+-----------------------------------------+
| radius.tls | RADIUS transported over TLS as defined |
| | in [RFC6614] |
| - - - - - - - - | - - - - - - - - - - - - - - - - - - - - |
| radius.dtls | RADIUS transported over DTLS as defined |
| | in [I-D.ietf-radext-dtls] |
+-----------------+-----------------------------------------+
Figure 2: List of Protocol Tags
Note well: Note well:
The S-NAPTR service and protocols are unrelated to the IANA The S-NAPTR service and protocols are unrelated to the IANA
Service Name and Transport Protocol Number registry Service Name and Transport Protocol Number registry
The delimiter '.' in the protocol tags is only a separator for The delimiter '.' in the protocol tags is only a separator for
human reading convenience - not for structure or namespacing; it human reading convenience - not for structure or namespacing; it
MUST NOT be parsed in any way by the querying application or MUST NOT be parsed in any way by the querying application or
resolver. resolver.
The use of the separator '.' is common also in other protocols' The use of the separator '.' is common also in other protocols'
protocol tags. This is coincidence and does not imply a shared protocol tags. This is coincidence and does not imply a shared
semantics with such protocols. semantics with such protocols.
This specification defines the SRV prefix "_radiustls._tcp" for This specification defines two SRV prefixes (i.e. two values for the
RADIUS over TLS [RFC6614] and "_radiustls._udp" for RADIUS over DTLS "_service._proto" part of an SRV RR):
[I-D.dekok-radext-dtls]. It is expected that in most cases, the
label used for the records is the DNS representation (punycode) of +-----------------+-----------------------------------------+
the literal realm name for which the server is the AAA server. | SRV Label | Use |
+-----------------+-----------------------------------------+
| _radiustls._tcp | RADIUS transported over TLS as defined |
| | in [RFC6614] |
| - - - - - - - - | - - - - - - - - - - - - - - - - - - - - |
| _radiustls._udp | RADIUS transported over DTLS as defined |
| | in [I-D.ietf-radext-dtls] |
+-----------------+-----------------------------------------+
Figure 3: List of SRV Labels
It is expected that in most cases, the label used for the records is
the DNS representation (punycode) of the literal realm name for which
the server is the RADIUS server.
However, arbitrary other labels may be used if, for example, a However, arbitrary other labels may be used if, for example, a
roaming consortium uses realm names which are not associated to DNS roaming consortium uses realm names which are not associated to DNS
names or special-purpose consortia where a globally valid discovery names or special-purpose consortia where a globally valid discovery
is not a use case. Such other labels require a consortium-wide is not a use case. Such other labels require a consortium-wide
agreement about the transformation from realm name to lookup label. agreement about the transformation from realm name to lookup label.
Examples: Examples:
a. A general-purpose AAA server for realm example.com might have DNS a. A general-purpose RADIUS server for realm example.com might have
entries as follows: DNS entries as follows:
example.com. IN NAPTR 50 50 "s" "aaa+auth:radius.tls" "" example.com. IN NAPTR 50 50 "s" "aaa+auth:radius.tls" ""
_radiustls._tcp.foobar.example.com. _radiustls._tcp.foobar.example.com.
_radiustls._tcp.foobar.example.com. IN SRV 0 10 2083 _radiustls._tcp.foobar.example.com. IN SRV 0 10 2083
radsec.example.com. radsec.example.com.
b. The consortium "foo" provides roaming services for its members b. The consortium "foo" provides roaming services for its members
only. The realms used are of the form enterprise-name.example. only. The realms used are of the form enterprise-name.example.
The consortium operates a special purpose DNS server for the The consortium operates a special purpose DNS server for the
(private) TLD "example" which all AAA servers use to resolve (private) TLD "example" which all RADIUS servers use to resolve
realm names. "Bad, Inc." is part of the consortium. On the realm names. "Bad, Inc." is part of the consortium. On the
consortium's DNS server, realm bad.example might have the consortium's DNS server, realm bad.example might have the
following DNS entries: following DNS entries:
bad.example IN NAPTR 50 50 "a" "aaa+auth:radius.dtls" "" bad.example IN NAPTR 50 50 "a" "aaa+auth:radius.dtls" ""
"very.bad.example" "very.bad.example"
c. The eduroam consortium uses realms based on DNS, but provides its c. The eduroam consortium uses realms based on DNS, but provides its
services to a closed community only. However, a AAA domain services to a closed community only. However, a AAA domain
participating in eduroam may also want to expose AAA services to participating in eduroam may also want to expose AAA services to
other, general-purpose, applications (on the same or other AAA other, general-purpose, applications (on the same or other RADIUS
servers). Due to that, the eduroam consortium uses the service servers). Due to that, the eduroam consortium uses the service
tag "x-eduroam" for authentication purposes and eduroam AAA tag "x-eduroam" for authentication purposes and eduroam RADIUS
servers use this tag to look up other eduroam servers. An servers use this tag to look up other eduroam servers. An
eduroam participant example.org which also provides general- eduroam participant example.org which also provides general-
purpose AAA on a different server uses the general "aaa+auth" purpose AAA on a different server uses the general "aaa+auth"
tag: tag:
example.org. IN NAPTR 50 50 "s" "x-eduroam:radius.tls" "" example.org. IN NAPTR 50 50 "s" "x-eduroam:radius.tls" ""
_radiustls._tcp.eduroam.example.org. _radiustls._tcp.eduroam.example.org.
example.org. IN NAPTR 50 50 "s" "aaa+auth:radius.tls" "" example.org. IN NAPTR 50 50 "s" "aaa+auth:radius.tls" ""
_radiustls._tcp.aaa.example.org _radiustls._tcp.aaa.example.org
_radiustls._tcp.eduroam.example.org. IN SRV 0 10 2083 aaa- _radiustls._tcp.eduroam.example.org. IN SRV 0 10 2083 aaa-
eduroam.example.org. eduroam.example.org.
_radiustls._tcp.aaa.example.org. IN SRV 0 10 2083 aaa- _radiustls._tcp.aaa.example.org. IN SRV 0 10 2083 aaa-
default.example.org. default.example.org.
2.3. Realm to AAA server resolution algorithm 2.3. Realm to RADIUS server resolution algorithm
This algorithm can be used to discover RADIUS servers (for RADIUS This algorithm can be used to discover RADIUS servers (for RADIUS
Authentication and RADIUS Accounting) or to discover RADIUS DynAuth Authentication and RADIUS Accounting) or to discover RADIUS DynAuth
servers. servers.
2.3.1. Input 2.3.1. Input
For RADIUS Authentication and RADIUS Accounting server discovery, For RADIUS Authentication and RADIUS Accounting server discovery,
input I to the algorithm is the RADIUS User-Name attribute with input I to the algorithm is the RADIUS User-Name attribute with
content of the form "user@realm"; the literal @ sign being the content of the form "user@realm"; the literal @ sign being the
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Usage of multiple @ separators Usage of multiple @ separators
Encoding of User-Name in local encodings Encoding of User-Name in local encodings
UTF-8 realms which fail the conversion rules as per [RFC5891] UTF-8 realms which fail the conversion rules as per [RFC5891]
UTF-8 realms which end with a . ("dot") character. UTF-8 realms which end with a . ("dot") character.
For the last bullet point, "trailing dot", special precautions should For the last bullet point, "trailing dot", special precautions should
be taken to avoid problems when resolving servers with the algorithm be taken to avoid problems when resolving servers with the algorithm
below: they may resolve to a AAA server even if the peer RADIUS below: they may resolve to a RADIUS server even if the peer RADIUS
server only is configured to handle the realm without the trailing server only is configured to handle the realm without the trailing
dot. If that RADIUS server again uses NAI discovery to determine the dot. If that RADIUS server again uses NAI discovery to determine the
authoritative server, the server will forward the request to authoritative server, the server will forward the request to
localhost, resulting in a tight endless loop. localhost, resulting in a tight endless loop.
2.3.2. Output 2.3.2. Output
Output O of the algorithm is a set of the tuple {hostname; port; Output O of the algorithm is a set of the tuple {hostname; port;
order/preference; TTL} - the set can be empty. order/preference; TTL} - the set can be empty.
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3. Security Considerations 3. Security Considerations
When using DNS without DNSSEC security extensions, the replies to When using DNS without DNSSEC security extensions, the replies to
NAPTR, SRV and A/AAAA requests as described in section Section 2 can NAPTR, SRV and A/AAAA requests as described in section Section 2 can
not be trusted. RADIUS transports have an out-of-DNS-band means to not be trusted. RADIUS transports have an out-of-DNS-band means to
verify that the discovery attempt led to the intended target: verify that the discovery attempt led to the intended target:
certificate verification or TLS-PSK keys. certificate verification or TLS-PSK keys.
4. IANA Considerations 4. IANA Considerations
This document requests IANA registration of the following S-NAPTR This document requests IANA registration of the following entries in
parameter: existing registries:
o Application Service Tags o S-NAPTR Application Service Tags registry
* aaa+auth * aaa+auth
* aaa+acct * aaa+acct
* aaa+dynauth * aaa+dynauth
o Application Protocol Tags o S-NAPTR Application Protocol Tags registry
* radius.tls * radius.tls
* radius.dtls * radius.dtls
This document reserves the use of the "_radiustls" Service label.
This document requests the creation of a new IANA registry named
"RADIUS/TLS SRV Protocol Registry" with the following initial
entries:
o _tcp
o _udp
5. Normative References 5. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to [RFC2119] Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels", BCP 14, Indicate Requirement Levels", BCP 14,
RFC 2119, March 1997. RFC 2119, March 1997.
[RFC3958] Daigle, L. and A. Newton, "Domain-Based [RFC2865] Rigney, C., Willens, S., Rubens, A., and W.
Application Service Location Using SRV RRs
and the Dynamic Delegation Discovery Service
(DDDS)", RFC 3958, January 2005.
[RFC5580] Tschofenig, H., Adrangi, F., Jones, M., Simpson, "Remote Authentication Dial In User
Lior, A., and B. Aboba, "Carrying Location Service (RADIUS)", RFC 2865, June 2000.
Objects in RADIUS and Diameter", RFC 5580,
August 2009.
[RFC5891] Klensin, J., "Internationalized Domain Names [RFC2866] Rigney, C., "RADIUS Accounting", RFC 2866,
in Applications (IDNA): Protocol", RFC 5891, June 2000.
August 2010.
[I-D.dekok-radext-dtls] DeKok, A., "DTLS as a Transport Layer for [RFC3958] Daigle, L. and A. Newton, "Domain-Based
RADIUS", draft-dekok-radext-dtls-03 (work in Application Service Location Using SRV RRs
progress), July 2010. and the Dynamic Delegation Discovery Service
(DDDS)", RFC 3958, January 2005.
[RFC6614] Winter, S., McCauley, M., Venaas, S., and K. [RFC5176] Chiba, M., Dommety, G., Eklund, M., Mitton,
Wierenga, "Transport Layer Security (TLS) D., and B. Aboba, "Dynamic Authorization
Encryption for RADIUS", RFC 6614, May 2012. Extensions to Remote Authentication Dial In
User Service (RADIUS)", RFC 5176,
January 2008.
[RFC5580] Tschofenig, H., Adrangi, F., Jones, M., Lior,
A., and B. Aboba, "Carrying Location Objects
in RADIUS and Diameter", RFC 5580,
August 2009.
[RFC5891] Klensin, J., "Internationalized Domain Names
in Applications (IDNA): Protocol", RFC 5891,
August 2010.
[I-D.ietf-radext-dtls] DeKok, A., "DTLS as a Transport Layer for
RADIUS", draft-ietf-radext-dtls-02 (work in
progress), July 2012.
[RFC6614] Winter, S., McCauley, M., Venaas, S., and K.
Wierenga, "Transport Layer Security (TLS)
Encryption for RADIUS", RFC 6614, May 2012.
Authors' Addresses Authors' Addresses
Stefan Winter Stefan Winter
Fondation RESTENA Fondation RESTENA
6, rue Richard Coudenhove-Kalergi 6, rue Richard Coudenhove-Kalergi
Luxembourg 1359 Luxembourg 1359
LUXEMBOURG LUXEMBOURG
Phone: +352 424409 1 Phone: +352 424409 1
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