draft-ietf-radext-dynamic-discovery-01.txt   draft-ietf-radext-dynamic-discovery-02.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: January 14, 2010 OSC Expires: September 6, 2010 OSC
July 13, 2009 March 05, 2010
NAI-based Dynamic Peer Discovery for RADIUS over TLS and DTLS NAI-based Dynamic Peer Discovery for RADIUS over TLS and DTLS
draft-ietf-radext-dynamic-discovery-01 draft-ietf-radext-dynamic-discovery-02
Abstract
This document specifies a means to find authoritative AAA servers for
a given NAI realm. It can be used in conjunction with RADIUS over
TLS and RADIUS over DTLS.
Status of This Memo Status of This Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 1, line 33 skipping to change at page 1, line 39
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."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on January 14, 2010. This Internet-Draft will expire on September 6, 2010.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2010 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 in effect on the date of Provisions Relating to IETF Documents
publication of this document (http://trustee.ietf.org/license-info). (http://trustee.ietf.org/license-info) in effect on the date of
Please review these documents carefully, as they describe your rights publication of this document. Please review these documents
and restrictions with respect to this document. carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
Abstract include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
This document specifies a means to find authoritative AAA servers for described in the Simplified BSD License.
a given NAI realm as defined in [RFC4282]. It can be used in
conjunction with RADIUS over TLS and RADIUS over DTLS.
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 AAA server resolution algorithm . . . . . . . . . 5
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 3. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
5. Normative References . . . . . . . . . . . . . . . . . . . . . 8 5. Normative References . . . . . . . . . . . . . . . . . . . . . 8
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]
1.2. Terminology 1.2. Terminology
RadSec node: a RadSec client or server RADIUS/TLS Client: a RADIUS/TLS [I-D.ietf-radext-radsec] instance
which initiates a new connection.
RadSec Client: a RadSec instance which initiates a new connection. RADIUS/TLS Server: a RADIUS/TLS [I-D.ietf-radext-radsec] instance
which listens on a RADIUS/TLS port and accepts new connections
RadSec Server: a RadSec instance which listens on a RadSec port and RADIUS/TLS node: a RADIUS/TLS client or server
accepts new connections
2. DNS-based NAPTR/SRV Peer Discovery 2. DNS-based NAPTR/SRV Peer Discovery
2.1. Applicability 2.1. Applicability
Dynamic server discovery as defined in this document is only Dynamic server discovery as defined in this document is only
applicable for AAA transactions where a AAA server receives a request applicable for AAA transactions where a AAA server receives a request
with a NAI realm for which no home AAA server is known. I.e. where with a NAI realm for which no home AAA server is known. I.e. where
static server configuration does not contain a known home static server configuration does not contain a known home
authentication server, or where the server configuration explicitly authentication server, or where the server configuration explicitly
states that the realm destination is to be looked up dynamically. states that the realm destination is to be looked up dynamically.
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, Access-Accepts, Accounting session, for example Access-Challenges, Access-Accepts, Accounting
Messages or Change-of-Authorisation messages use the previously- Messages or Change-of-Authorisation messages use the previously-
established communication channel between client and server. established communication channel between client and server.
2.2. DNS RR definition 2.2. DNS RR definition
DNS definitions of RadSec servers can be either NAPTR records or SRV DNS definitions of RADIUS/TLS servers can be either S-NAPTR records
records. When both are defined, the resolution algorithm prefers (see [RFC3958]) or SRV records. When both are defined, the
NAPTR results (see section Section 2.3 below). The NAPTR service resolution algorithm prefers S-NAPTR results (see section Section 2.3
field used is "AAAS+RADSECT". The SRV prefix used is "_radsec._tcp". below).
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 This specification defines two S-NAPTR service tag: a general-purpose
the server is the AAA server. tag "nai-roaming" and a special-purpose tag "eduroam" for the eduroam
roaming consortium. This specification defines two S-NAPTR protocol
tags: "radius.tls" for RADIUS over TLS [I-D.ietf-radext-radsec] and
"radius.dtls" for RADIUS over DTLS [I-D.dekok-radext-dtls].
This specification defines the SRV prefix "_radiustls._tcp" for
RADIUS over TLS [I-D.ietf-radext-radsec] and "_radiustls._udp" for
RADIUS over DTLS [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.
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 AAA server for realm example.com might have DNS
entries as follows: entries as follows:
example.com. IN NAPTR 50 50 "s" "AAAS+RADSECT" "" example.com. IN NAPTR 50 50 "s" "nai-roaming:radius.tls" ""
_radsec._tcp.foobar.example.com. _radiustls._tcp.foobar.example.com.
_radsec._tcp.example.com. IN SRV 0 10 2083 _radiustls._tcp.example.com. IN SRV 0 10 2083
radsec.example.com. radsec.example.com.
b. Consortium "foo" provides roaming services for banks. The realms b. The consortium "foo" provides roaming services for its members
used are of the form enterprise-name.foobankroam. The consortium only. The realms used are of the form enterprise-name.example.
operates a special purpose DNS server for the (private) TLD The consortium operates a special purpose DNS server for the
"foobankroam" which all AAA servers use to resolve realm names. (private) TLD "example" which all AAA servers use to resolve
"Rupt, Inc." is part of the consortium. On the consortium's DNS realm names. "Bad, Inc." is part of the consortium. On the
server, realm bank-rupt.foobankroam might have the following DNS consortium's DNS server, realm bad.example might have the
entries: following DNS entries:
bank-rupt.foobankroam IN NAPTR 50 50 "a" "AAAS+RADSECT" ""
"triple-a.bank-rupt.com"
_radsec._tcp.bank-rupt.foobankroam IN SRV 0 10 2083 triple-a- bad.example IN NAPTR 50 50 "a" "nai-roaming:radius.dtls" ""
backup.bank-rupt.com" "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 AAA
servers). Due to that, the eduroam consortium uses labels servers). Due to that, the eduroam consortium uses the service
prefixed with "eduroam." and eduroam AAA servers use these labels tag "eduroam" and eduroam AAA servers use this tag to look up
to look up servers. An eduroam participant which also provides other eduroam servers. An eduroam participant example.org which
general-purpose AAA on a different server might have the also provides general-purpose AAA on a different server uses the
following DNS entries: general "nai-roaming" tag:
eduroam.restena.lu. IN NAPTR 50 50 "a" "AAAS+RADSECT" "" aaa- example.org. IN NAPTR 50 50 "s" "eduroam:radius.tls" ""
eduroam.restena.lu _radiustls._tcp.eduroam.example.org.
restena.lu. IN NAPTR 50 50 "a" "AAAS+RADSECT" "" aaa- example.org. IN NAPTR 50 50 "s" "nai-roaming:radius.tls" ""
default.restena.lu _radiustls._tcp.aaa.example.org
_radsec._tcp.eduroam.restena.lu. IN SRV 0 10 2083 aaa- _radiustls._tcp.eduroam.example.org. IN SRV 0 10 2083 aaa-
eduroam.restena.lu. eduroam.example.org.
_radsec._tcp.restena.lu. IN SRV 0 10 2083 aaa- _radiustls._tcp.aaa.example.org. IN SRV 0 10 2083 aaa-
default.restena.lu. default.example.org.
2.3. Realm to AAA server resolution algorithm 2.3. Realm to AAA server resolution algorithm
Input I to the algorithm is a User-Name in the form of a NAI as Input I to the algorithm is a User-Name in the form of a NAI as
defined in [RFC4282] as extracted from the User-Name attribute in an defined in [RFC4282] as extracted from the User-Name attribute in an
Access-Request. Output O of the algorithm is a set of hostname:port Access-Request. Output O of the algorithm is a set of hostname:port
and an assoiciated order/preference; the set can be empty. and an associated order/preference; the set can be empty.
Note well: The attribute User-Name does not necessarily contain well- Note well: The attribute User-Name does not necessarily contain well-
formed NAIs and may not even contain well-formed UTF-8 strings. This formed NAIs and may not even contain well-formed UTF-8 strings. This
document describes server discovery only for well-formed NAIs in document describes server discovery only for well-formed NAIs in
UTF-8 encoding. The result of all other possible contents of User- UTF-8 encoding. The result of all other possible contents of User-
Name is unspecified; this includes, but is not limited to: Name is unspecified; this includes, but is not limited to:
Usage of separators other than @ Usage of separators other than @
Usage of multiple @ separators Usage of multiple @ separators
skipping to change at page 5, line 36 skipping to change at page 5, line 42
The algorithm to determine the AAA server to contact is as follows: The algorithm to determine the AAA server to contact is as follows:
1. Determine P = (position of first "@" character) in I. 1. Determine P = (position of first "@" character) in I.
2. generate R = (substring from P+1 to end of I) 2. generate R = (substring from P+1 to end of I)
3. Optional: modify R according to agreed consortium procedures 3. Optional: modify R according to agreed consortium procedures
4. Using the host's name resolution library, perform a NAPTR query 4. Using the host's name resolution library, perform a NAPTR query
for service "AAAS+RADSECT" for R for R. If no result, continue at step 9. If name resolution
returns with error, O = { }. Terminate.
5. If name resolution returns with error, O = { }. Terminate. 5. Extract NAPTR records with service tag "nai-roaming" (replace
with other service tags where applicable).
6. If no result, continue at step 9. 6. If no result, continue at step 9.
7. Evaluate NAPTR result, perform subsequent lookup steps until 7. Evaluate NAPTR result(s) for desired protocol tag, perform
lookup yields one or more hostnames. O = (set of {Order/ subsequent lookup steps until lookup yields one or more
Preference, hostname:port} for all lookup results). hostnames. O = (set of {Order/Preference, hostname:port} for
all lookup results).
8. Terminate. 8. Terminate.
9. Generate R' = (prefix R with "_radsec._tcp.") 9. Generate R' = (prefix R with "_radiustls._tcp." or
"_radiustls._udp")
10. Using the host's name resolution library, perform SRV lookup 10. Using the host's name resolution library, perform SRV lookup
with R' as label. with R' as label.
11. If name resolution returns with error, O = { }. Terminate. 11. If name resolution returns with error, O = { }. Terminate.
12. If no result, O = {}; terminate. 12. If no result, O = {}; terminate.
13. Perform subsequent lookup steps until lookup yields one or more 13. Perform subsequent lookup steps until lookup yields one or more
hostnames. O = (set of {Order/Preference, hostname} for all hostnames. O = (set of {Order/Preference, hostname} for all
hostnames). Terminate. hostnames). Terminate.
Example: Assume a user from the Technical University of Munich, Example: Assume a user from the Technical University of Munich,
Germany, has a RADIUS User-Name of Germany, has a RADIUS User-Name of
"foobar@tu-m[U+00FC]nchen.example". If DNS contains the following "foobar@tu-m[U+00FC]nchen.example". If DNS contains the following
records: records:
xn--tu-mnchen-t9a.example. IN NAPTR 50 50 "s" "AAAS+RADSECT" "" xn--tu-mnchen-t9a.example. IN NAPTR 50 50 "s" "nai-
_radsec._tcp.xn--tu-mnchen-t9a.example. roaming:radius.tls" "" _radiustls._tcp.xn--tu-mnchen-t9a.example.
_radsec._tcp.xn--tu-mnchen-t9a.example. IN SRV 0 10 2083 xn--tu-mnchen-t9a.example. IN NAPTR 50 50 "s" "fooservice:
bar.dccp" "" _abc._def.xn--tu-mnchen-t9a.example.
_radiustls._tcp.xn--tu-mnchen-t9a.example. IN SRV 0 10 2083
radsec.xn--tu-mnchen-t9a.example. radsec.xn--tu-mnchen-t9a.example.
_radsec._tcp.xn--tu-mnchen-t9a.example. IN SRV 0 20 2083 _radiustls._tcp.xn--tu-mnchen-t9a.example. IN SRV 0 20 2083
backup.xn--tu-mnchen-t9a.example. backup.xn--tu-mnchen-t9a.example.
radsec.xn--tu-mnchen-t9a.example. IN AAAA 2001:0DB8::202:44ff: radsec.xn--tu-mnchen-t9a.example. IN AAAA 2001:0DB8::202:44ff:
fe0a:f704 fe0a:f704
radsec.xn--tu-mnchen-t9a.example. IN A 192.0.2.3 radsec.xn--tu-mnchen-t9a.example. IN A 192.0.2.3
backup.xn--tu-mnchen-t9a.example. IN A 192.0.2.7 backup.xn--tu-mnchen-t9a.example. IN A 192.0.2.7
Then the algorithm executes as follows, with I = Then the algorithm executes as follows, with I =
skipping to change at page 6, line 39 skipping to change at page 7, line 4
radsec.xn--tu-mnchen-t9a.example. IN A 192.0.2.3 radsec.xn--tu-mnchen-t9a.example. IN A 192.0.2.3
backup.xn--tu-mnchen-t9a.example. IN A 192.0.2.7 backup.xn--tu-mnchen-t9a.example. IN A 192.0.2.7
Then the algorithm executes as follows, with I = Then the algorithm executes as follows, with I =
"foobar@tu-m[U+00FC]nchen.example", and no consortium name mangling "foobar@tu-m[U+00FC]nchen.example", and no consortium name mangling
in use: in use:
1. P = 7 1. P = 7
2. R = "tu-m[U+00FC]nchen.example" 2. R = "tu-m[U+00FC]nchen.example"
3. NOOP 3. NOOP
4. Query result: ( 0 10 2083 radsec.xn--tu-mnchen-t9a.example. ; 0 4. Query result: ( 50 50 "s" "nai-roaming:radius.tls" ""
20 2083 backup.xn--tu-mnchen-t9a.example. ) _radiustls._tcp.xn--tu-mnchen-t9a.example. ; 50 50 "s"
"fooservice:bar.dccp" "" _abc._def.xn--tu-mnchen-t9a.example. )
5. NOOP 5. Result: 50 50 "s" "nai-roaming:radius.tls" ""
_radiustls._tcp.xn--tu-mnchen-t9a.example.
6. NOOP 6. NOOP
7. O = {(10,radsec.xn--tu-mnchen-t9a.example.:2083),(20,backup.xn-- 7. O = {(10,radsec.xn--tu-mnchen-t9a.example.:2083),(20,backup.xn--
tu-mnchen-t9a.example.:2083)} tu-mnchen-t9a. example.:2083)}
8. Terminate. 8. Terminate.
9. (not executed) 9. (not executed)
10. (not executed) 10. (not executed)
11. (not executed) 11. (not executed)
12. (not executed) 12. (not executed)
skipping to change at page 7, line 48 skipping to change at page 8, line 15
trick the initiating peer into using the weakly protected UDP or TCP trick the initiating peer into using the weakly protected UDP or TCP
transports. The use of DNSSEC can not fully mitigate this attack, transports. The use of DNSSEC can not fully mitigate this attack,
since it does not provide a means to detect packet suppression. The since it does not provide a means to detect packet suppression. The
only way to disable such bidding down attacks is by intiating only way to disable such bidding down attacks is by intiating
connections only to the peer(s) which match or exceed a configured connections only to the peer(s) which match or exceed a configured
minimum security level. All implementations SHOULD provide a means minimum security level. All implementations SHOULD provide a means
to configure the administratively desired minimum security level. to configure the administratively desired minimum security level.
4. IANA Considerations 4. IANA Considerations
This document contains no actions for IANA. Maybe. Not sure about This document requests IANA registration of the following S-NAPTR
the labels "AAAS+RADSECT" and "_radsec._tcp.". parameters:
o Application Service Tags
* nai-roaming
* eduroam
o Application Protocol Tags
* radius.tls
* radius.dtls
5. Normative References 5. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to
Requirement Levels", BCP 14, RFC 2119, March 1997. Indicate Requirement Levels", BCP 14,
RFC 2119, March 1997.
[RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The [RFC3958] Daigle, L. and A. Newton, "Domain-Based
Network Access Identifier", RFC 4282, December 2005. Application Service Location Using SRV RRs
and the Dynamic Delegation Discovery
Service (DDDS)", RFC 3958, January 2005.
[RFC4282] Aboba, B., Beadles, M., Arkko, J., and P.
Eronen, "The Network Access Identifier",
RFC 4282, December 2005.
[I-D.dekok-radext-dtls] DeKok, A., "DTLS as a Transport Layer for
RADIUS", draft-dekok-radext-dtls-01 (work
in progress), June 2009.
[I-D.ietf-radext-radsec] Winter, S., McCauley, M., Venaas, S., and
K. Wierenga, "TLS encryption for RADIUS
over TCP", draft-ietf-radext-radsec-06
(work in progress), March 2010.
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
 End of changes. 34 change blocks. 
77 lines changed or deleted 125 lines changed or added

This html diff was produced by rfcdiff 1.38. The latest version is available from http://tools.ietf.org/tools/rfcdiff/