--- 1/draft-ietf-radext-dynamic-discovery-01.txt 2010-03-05 16:10:58.000000000 +0100 +++ 2/draft-ietf-radext-dynamic-discovery-02.txt 2010-03-05 16:10:58.000000000 +0100 @@ -1,19 +1,25 @@ RADIUS Extensions Working Group S. Winter Internet-Draft RESTENA Intended status: Experimental M. McCauley -Expires: January 14, 2010 OSC - July 13, 2009 +Expires: September 6, 2010 OSC + March 05, 2010 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 This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. @@ -22,156 +28,162 @@ 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at 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 (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. This document is subject to BCP 78 and the IETF Trust's Legal - Provisions Relating to IETF Documents in effect on the date of - publication of this document (http://trustee.ietf.org/license-info). - Please review these documents carefully, as they describe your rights - and restrictions with respect to this document. - -Abstract - - This document specifies a means to find authoritative AAA servers for - a given NAI realm as defined in [RFC4282]. It can be used in - conjunction with RADIUS over TLS and RADIUS over DTLS. + 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 + described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 2. DNS-based NAPTR/SRV Peer Discovery . . . . . . . . . . . . . . 3 2.1. Applicability . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. DNS RR definition . . . . . . . . . . . . . . . . . . . . . 3 2.3. Realm to AAA server resolution algorithm . . . . . . . . . 5 3. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 - 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 + 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8 5. Normative References . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction 1.1. Requirements Language In this document, several words are used to signify the requirements of the specification. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. [RFC2119] 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 - accepts new connections + RADIUS/TLS node: a RADIUS/TLS client or server 2. DNS-based NAPTR/SRV Peer Discovery 2.1. Applicability Dynamic server discovery as defined in this document is only 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 static server configuration does not contain a known home authentication server, or where the server configuration explicitly states that the realm destination is to be looked up dynamically. Furthermore, it is only applicable for new user sessions, i.e. for the initial Access-Request. Subsequent messages concerning this session, for example Access-Challenges, Access-Accepts, Accounting Messages or Change-of-Authorisation messages use the previously- established communication channel between client and server. 2.2. DNS RR definition - DNS definitions of RadSec servers can be either NAPTR records or SRV - records. When both are defined, the resolution algorithm prefers - NAPTR results (see section Section 2.3 below). The NAPTR service - field used is "AAAS+RADSECT". The SRV prefix used is "_radsec._tcp". - 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. + DNS definitions of RADIUS/TLS servers can be either S-NAPTR records + (see [RFC3958]) or SRV records. When both are defined, the + resolution algorithm prefers S-NAPTR results (see section Section 2.3 + below). + + This specification defines two S-NAPTR service tag: a general-purpose + 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 roaming consortium uses realm names which are not associated to DNS names or special-purpose consortia where a globally valid discovery is not a use case. Such other labels require a consortium-wide agreement about the transformation from realm name to lookup label. Examples: a. A general-purpose AAA server for realm example.com might have DNS entries as follows: - example.com. IN NAPTR 50 50 "s" "AAAS+RADSECT" "" - _radsec._tcp.foobar.example.com. + example.com. IN NAPTR 50 50 "s" "nai-roaming:radius.tls" "" + _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. - b. Consortium "foo" provides roaming services for banks. The realms - used are of the form enterprise-name.foobankroam. The consortium - operates a special purpose DNS server for the (private) TLD - "foobankroam" which all AAA servers use to resolve realm names. - "Rupt, Inc." is part of the consortium. On the consortium's DNS - server, realm bank-rupt.foobankroam might have the following DNS - entries: - - bank-rupt.foobankroam IN NAPTR 50 50 "a" "AAAS+RADSECT" "" - "triple-a.bank-rupt.com" + b. The consortium "foo" provides roaming services for its members + only. The realms used are of the form enterprise-name.example. + The consortium operates a special purpose DNS server for the + (private) TLD "example" which all AAA servers use to resolve + realm names. "Bad, Inc." is part of the consortium. On the + consortium's DNS server, realm bad.example might have the + following DNS entries: - _radsec._tcp.bank-rupt.foobankroam IN SRV 0 10 2083 triple-a- - backup.bank-rupt.com" + bad.example IN NAPTR 50 50 "a" "nai-roaming:radius.dtls" "" + "very.bad.example" c. the eduroam consortium uses realms based on DNS, but provides its services to a closed community only. However, a AAA domain participating in eduroam may also want to expose AAA services to other, general-purpose, applications (on the same or other AAA - servers). Due to that, the eduroam consortium uses labels - prefixed with "eduroam." and eduroam AAA servers use these labels - to look up servers. An eduroam participant which also provides - general-purpose AAA on a different server might have the - following DNS entries: + servers). Due to that, the eduroam consortium uses the service + tag "eduroam" and eduroam AAA servers use this tag to look up + other eduroam servers. An eduroam participant example.org which + also provides general-purpose AAA on a different server uses the + general "nai-roaming" tag: - eduroam.restena.lu. IN NAPTR 50 50 "a" "AAAS+RADSECT" "" aaa- - eduroam.restena.lu + example.org. IN NAPTR 50 50 "s" "eduroam:radius.tls" "" + _radiustls._tcp.eduroam.example.org. - restena.lu. IN NAPTR 50 50 "a" "AAAS+RADSECT" "" aaa- - default.restena.lu + example.org. IN NAPTR 50 50 "s" "nai-roaming:radius.tls" "" + _radiustls._tcp.aaa.example.org - _radsec._tcp.eduroam.restena.lu. IN SRV 0 10 2083 aaa- - eduroam.restena.lu. + _radiustls._tcp.eduroam.example.org. IN SRV 0 10 2083 aaa- + eduroam.example.org. - _radsec._tcp.restena.lu. IN SRV 0 10 2083 aaa- - default.restena.lu. + _radiustls._tcp.aaa.example.org. IN SRV 0 10 2083 aaa- + default.example.org. 2.3. Realm to AAA server resolution algorithm 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 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- formed NAIs and may not even contain well-formed UTF-8 strings. This document describes server discovery only for well-formed NAIs in UTF-8 encoding. The result of all other possible contents of User- Name is unspecified; this includes, but is not limited to: Usage of separators other than @ Usage of multiple @ separators @@ -180,57 +192,64 @@ The algorithm to determine the AAA server to contact is as follows: 1. Determine P = (position of first "@" character) in I. 2. generate R = (substring from P+1 to end of I) 3. Optional: modify R according to agreed consortium procedures 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. - 7. Evaluate NAPTR result, perform subsequent lookup steps until - lookup yields one or more hostnames. O = (set of {Order/ - Preference, hostname:port} for all lookup results). + 7. Evaluate NAPTR result(s) for desired protocol tag, perform + subsequent lookup steps until lookup yields one or more + hostnames. O = (set of {Order/Preference, hostname:port} for + all lookup results). 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 with R' as label. 11. If name resolution returns with error, O = { }. Terminate. 12. If no result, O = {}; terminate. 13. Perform subsequent lookup steps until lookup yields one or more hostnames. O = (set of {Order/Preference, hostname} for all hostnames). Terminate. Example: Assume a user from the Technical University of Munich, Germany, has a RADIUS User-Name of "foobar@tu-m[U+00FC]nchen.example". If DNS contains the following records: - xn--tu-mnchen-t9a.example. IN NAPTR 50 50 "s" "AAAS+RADSECT" "" - _radsec._tcp.xn--tu-mnchen-t9a.example. + xn--tu-mnchen-t9a.example. IN NAPTR 50 50 "s" "nai- + 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._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. radsec.xn--tu-mnchen-t9a.example. IN AAAA 2001:0DB8::202:44ff: fe0a:f704 radsec.xn--tu-mnchen-t9a.example. IN A 192.0.2.3 backup.xn--tu-mnchen-t9a.example. IN A 192.0.2.7 Then the algorithm executes as follows, with I = @@ -231,29 +250,30 @@ radsec.xn--tu-mnchen-t9a.example. IN A 192.0.2.3 backup.xn--tu-mnchen-t9a.example. IN A 192.0.2.7 Then the algorithm executes as follows, with I = "foobar@tu-m[U+00FC]nchen.example", and no consortium name mangling in use: 1. P = 7 - 2. R = "tu-m[U+00FC]nchen.example" 3. NOOP - 4. Query result: ( 0 10 2083 radsec.xn--tu-mnchen-t9a.example. ; 0 - 20 2083 backup.xn--tu-mnchen-t9a.example. ) + 4. Query result: ( 50 50 "s" "nai-roaming:radius.tls" "" + _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 7. O = {(10,radsec.xn--tu-mnchen-t9a.example.:2083),(20,backup.xn-- tu-mnchen-t9a.example.:2083)} 8. Terminate. 9. (not executed) @@ -289,30 +309,58 @@ trick the initiating peer into using the weakly protected UDP or TCP transports. The use of DNSSEC can not fully mitigate this attack, since it does not provide a means to detect packet suppression. The only way to disable such bidding down attacks is by intiating connections only to the peer(s) which match or exceed a configured minimum security level. All implementations SHOULD provide a means to configure the administratively desired minimum security level. 4. IANA Considerations - This document contains no actions for IANA. Maybe. Not sure about - the labels "AAAS+RADSECT" and "_radsec._tcp.". + This document requests IANA registration of the following S-NAPTR + parameters: + + o Application Service Tags + + * nai-roaming + + * eduroam + + o Application Protocol Tags + + * radius.tls + + * radius.dtls 5. Normative References - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, March 1997. + [RFC2119] Bradner, S., "Key words for use in RFCs to + Indicate Requirement Levels", BCP 14, + RFC 2119, March 1997. - [RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The - Network Access Identifier", RFC 4282, December 2005. + [RFC3958] Daigle, L. and A. Newton, "Domain-Based + 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 Stefan Winter Fondation RESTENA 6, rue Richard Coudenhove-Kalergi Luxembourg 1359 LUXEMBOURG Phone: +352 424409 1