draft-ietf-radext-dynamic-discovery-03.txt   draft-ietf-radext-dynamic-discovery-04.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 10, 2012 OSC Expires: December 30, 2012 OSC
July 09, 2011 June 28, 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-03 draft-ietf-radext-dynamic-discovery-04
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
skipping to change at page 1, line 33 skipping to change at page 1, line 33
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 January 10, 2012. This Internet-Draft will expire on December 30, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 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
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publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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 AAA server resolution algorithm . . . . . . . . . 5
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 8 2.3.1. Input . . . . . . . . . . . . . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8 2.3.2. Output . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Normative References . . . . . . . . . . . . . . . . . . . . . 8 2.3.3. Algorithm . . . . . . . . . . . . . . . . . . . . . . 6
2.3.4. Validity of results . . . . . . . . . . . . . . . . . 7
2.3.5. Delay considerations . . . . . . . . . . . . . . . . . 8
2.3.6. Example . . . . . . . . . . . . . . . . . . . . . . . 8
3. Security Considerations . . . . . . . . . . . . . . . . . . . 10
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5. Normative References . . . . . . . . . . . . . . . . . . . . . 10
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
RADIUS/TLS Client: a RADIUS/TLS [I-D.ietf-radext-radsec] instance RADIUS/TLS Client: a RADIUS/TLS [RFC6614] instance which initiates a
which initiates a new connection. new connection.
RADIUS/TLS Server: a RADIUS/TLS [I-D.ietf-radext-radsec] instance RADIUS/TLS Server: a RADIUS/TLS [RFC6614] instance which listens on a
which listens on a RADIUS/TLS port and accepts new connections RADIUS/TLS port and accepts new connections
RADIUS/TLS node: a RADIUS/TLS client or server RADIUS/TLS node: a RADIUS/TLS client or server
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 RADIUS server receives a applicable for AAA transactions where a RADIUS server receives a
request with a realm for which no home RADIUS server is known. I.e. request with a realm for which no home RADIUS server is known. I.e.
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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 Section 2.3
below). below).
This specification defines three S-NAPTR service tags: "aaa+auth", This specification defines three S-NAPTR service tags: "aaa+auth",
"aaa+acct" and "aaa+dynauth". This specification defines two S-NAPTR "aaa+acct" and "aaa+dynauth". This specification defines two S-NAPTR
protocol tags: "radius.tls" for RADIUS/TLS [I-D.ietf-radext-radsec] protocol tags: "radius.tls" for RADIUS/TLS [RFC6614] and
and "radius.dtls" for RADIUS/DTLS [I-D.dekok-radext-dtls]. "radius.dtls" for RADIUS/DTLS [I-D.dekok-radext-dtls].
Note well:
The S-NAPTR service and protocols are unrelated to the IANA
Service Name and Transport Protocol Number registry
The delimiter '.' in the protocol tags is only a separator for
human reading convenience - not for structure or namespacing; it
MUST NOT be parsed in any way by the querying application or
resolver.
The use of the separator '.' is common also in other protocols'
protocol tags. This is coincidence and does not imply a shared
semantics with such protocols.
This specification defines the SRV prefix "_radiustls._tcp" for This specification defines the SRV prefix "_radiustls._tcp" for
RADIUS over TLS [I-D.ietf-radext-radsec] and "_radiustls._udp" for RADIUS over TLS [RFC6614] and "_radiustls._udp" for RADIUS over DTLS
RADIUS over DTLS [I-D.dekok-radext-dtls]. It is expected that in [I-D.dekok-radext-dtls]. It is expected that in most cases, the
most cases, the label used for the records is the DNS representation label used for the records is the DNS representation (punycode) of
(punycode) of the literal realm name for which the server is the AAA the literal realm name for which the server is the AAA server.
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
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_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 AAA server resolution algorithm
Input I to the algorithm is the RADIUS User-Name attribute with This algorithm can be used to discover RADIUS servers (for RADIUS
Authentication and RADIUS Accounting) or to discover RADIUS DynAuth
servers.
2.3.1. Input
For RADIUS Authentication and RADIUS Accounting server discovery,
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
separator between a local user identifier within a realm and its separator between a local user identifier within a realm and its
realm. The use of multiple literal @ signs in a User-Name is realm. The use of multiple literal @ signs in a User-Name is
strongly discouraged; but if present, the last @ sign is to be strongly discouraged; but if present, the last @ sign is to be
considered the separator. All previous instances of the @ sign are considered the separator. All previous instances of the @ sign are
to be considered part of the local user identifier. Output O of the to be considered part of the local user identifier.
algorithm is a set of hostname:port and an associated order/
preference; the set can be empty. For RADIUS DynAuth Server discovery, input I to the algorithm is the
domain name of the operator of a RADIUS realm as was communicated
during user authentication using the Operator-Name attribute
([RFC5580], section 4.1). Only Operator-Name values with the
namespace "1" are supported by this algorithm - the input to the
algorithm is the actual domain name, preceeded with an "@" (but
without the "1" namespace identifier byte of that attribute).
Note well: The attribute User-Name is defined to contain UTF-8 text. Note well: The attribute User-Name is defined to contain UTF-8 text.
In practice, the content may or may not be UTF-8. Even if UTF-8, it In practice, the content may or may not be UTF-8. Even if UTF-8, it
may or may not map to a domain name in the realm part. Implementors may or may not map to a domain name in the realm part. Implementors
MUST take possible conversion error paths into consideration when MUST take possible conversion error paths into consideration when
parsing incoming User-Name attributes. This document describes parsing incoming User-Name attributes. This document describes
server discovery only for well-formed realms mapping to DNS domain server discovery only for well-formed realms mapping to DNS domain
names in UTF-8 encoding. The result of all other possible contents names in UTF-8 encoding. The result of all other possible contents
of User-Name is unspecified; this includes, but is not limited to: of User-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
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.
For the last bullet point, "trailing dot", special precautions should
be taken to avoid problems when resolving servers with the algorithm
below: they may resolve to a AAA server even if the peer RADIUS
server only is configured to handle the realm without the trailing
dot. If that RADIUS server again uses NAI discovery to determine the
authoritative server, the server will forward the request to
localhost, resulting in a tight endless loop.
2.3.2. Output
Output O of the algorithm is a set of the tuple {hostname; port;
order/preference; TTL} - the set can be empty.
2.3.3. Algorithm
The algorithm to determine the RADIUS server to contact is as The algorithm to determine the RADIUS server to contact is as
follows: follows:
1. Determine P = (position of last "@" character) in I. 1. Determine P = (position of last "@" 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 R. The name resolution library may need to convert R to a for R (see "Delay considerations" below). The name resolution
different respresentation, depending on the resolution backend library may need to convert R to a different respresentation,
used. If no result, continue at step 9. If name resolution depending on the resolution backend used. If no result,
returns with error, O = { }. Terminate. continue at step 9. If name resolution returns with error, O =
{ } and terminate.
5. Extract NAPTR records with service tag "aaa+auth", "aaa+acct", 5. Extract NAPTR records with service tag "aaa+auth", "aaa+acct",
"aaa+dynauth" as appropriate. "aaa+dynauth" as appropriate. Keep note of the remaining TTL of
each of the discovered NAPTR records.
6. If no result, continue at step 9. 6. If no result, continue at step 9.
7. Evaluate NAPTR result(s) for desired protocol tag, perform 7. Evaluate NAPTR result(s) for desired protocol tag, perform
subsequent lookup steps until lookup yields one or more subsequent lookup steps until lookup yields one or more
hostnames. O = (set of {Order/Preference, hostname:port} for hostnames. O = (set of {hostname; port; order/preference;
all lookup results). min{all TTLs that led to this result} } for all lookup results).
Keep note of the remaining TTL of each of the discovered records
(e.g. SRV and AAAA).
8. Terminate. 8. Terminate.
9. Generate R' = (prefix R with "_radiustls._tcp." or 9. Generate R' = (prefix R with "_radiustls._tcp." or
"_radiustls._udp") "_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 (see "Delay considerations" below). Keep note
of the TTL of each of the discovered SRV records.
11. If name resolution returns with error, O = { }. Terminate. 11. If name resolution returns with error, O = { } and terminate.
12. If no result, O = {}; terminate. 12. If no result, O = {} and 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 (see "Delay considerations" below). Keep note of the
hostnames). Terminate. TTL of each of the discovered records.
14. O = (set of {hostname; port; order/preference; min{all TTLs that
led to this result} } for all hostnames). Terminate.
2.3.4. Validity of results
After executing the above algorithm, the RADIUS server establishes a
connection to a home server from the result set. This connection can
potentially remain open for an indefinite amount of time. This
conflicts with the possibility of changing device and network
configurations on the receiving end. Typically, TTL values for
records in the name resolution system are used to indicate how long
it is safe to rely on the results of the name resolution. To allow
for a change of configuration, a RADIUS server SHOULD re-execute the
algorithm above after the lowest of the TTL values that are
associated with this connection have expired. The server MAY keep
the session open during this re-assessment to avoid closure and
immediate re-opening of the connection should the result not have
changed.
Should the algorithm above terminate with an empty set (but no
error), the RADIUS server SHOULD NOT attempt another execution of
this algorithm for the same target realm before the negative TTL has
expired.
Should the algorithm above terminate due to an error with no TTL
value known (e.g. DNS SERVFAIL), the RADIUS server SHOULD NOT
attempt another execution of this algorithm for the same target realm
before a configurable timeout interval has passed.
2.3.5. Delay considerations
The host's name resolution library may need to contact outside
entities to perform the name resolution (e.g. authoritative name
servers for a domain), and since the NAI discovery algorithm is based
on uncontrollable user input, the destination of the lookups is out
of control of the server that performs NAI discovery. If such
outside entities are misconfigured or unreachable, the algorithm
above may need an unacceptably long time to terminate. Many RADIUS
implementations time out after five seconds of delay between Request
and Response. It is not useful to wait until the host name
resolution library signals a time-out of its name resolution
algorithms; instead, implementations of NAI discovery SHOULD
terminate the algorithm after the fixed upper bound of time of three
seconds. If no final output of the algorithm is available after this
timeout, the RADIUS server MUST assume the empty set as a result and
treat the pending request according to its static configuration
(e.g., fallback to a default route to a home server). Execution of
the NAI discovery algorithm SHOULD be non-blocking (i.e. allow other
requests to be processed in parallel to the execution of the
algorithm).
2.3.6. Example
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". The name resolution library on "foobar@tu-m[U+00FC]nchen.example". The name resolution library on
the RADIUS client uses DNS for name resolution. If DNS contains the the RADIUS client uses DNS for name resolution. If DNS contains the
following records: following records:
xn--tu-mnchen-t9a.example. IN NAPTR 50 50 "s" "aaa+ xn--tu-mnchen-t9a.example. IN NAPTR 50 50 "s" "aaa+
auth:radius.tls" "" _radiustls._tcp.xn--tu-mnchen-t9a.example. auth:radius.tls" "" _radiustls._tcp.xn--tu-mnchen-t9a.example.
skipping to change at page 7, line 35 skipping to change at page 9, line 38
4. [name resolution library converts R to xn--tu-mnchen- 4. [name resolution library converts R to xn--tu-mnchen-
t9a.example] Query result: ( 50 50 "s" "aaa+auth:radius.tls" "" t9a.example] Query result: ( 50 50 "s" "aaa+auth:radius.tls" ""
_radiustls._tcp.xn--tu-mnchen-t9a.example. ; 50 50 "s" _radiustls._tcp.xn--tu-mnchen-t9a.example. ; 50 50 "s"
"fooservice:bar.dccp" "" _abc._def.xn--tu-mnchen-t9a.example. ) "fooservice:bar.dccp" "" _abc._def.xn--tu-mnchen-t9a.example. )
5. Result: 50 50 "s" "aaa+auth:radius.tls" "" _radiustls._tcp.xn-- 5. Result: 50 50 "s" "aaa+auth:radius.tls" "" _radiustls._tcp.xn--
tu-mnchen-t9a.example. tu-mnchen-t9a.example.
6. NOOP 6. NOOP
7. O = {(10,radsec.xn--tu-mnchen-t9a.example.:2083),(20,backup.xn-- 7. O = {(radsec.xn--tu-mnchen-t9a.example.; 2083; 10; TTL
tu-mnchen-t9a. example.:2083)} A),(backup.xn--tu-mnchen-t9a. example.;2083; 20; TTL B)}
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)
13. (not executed) 13. (not executed)
14. (not executed)
The implementation will then attempt to connect to two servers, with The implementation will then attempt to connect to two servers, with
preference to radsec.xn--tu-mnchen-t9a.example.:2083, using either preference to radsec.xn--tu-mnchen-t9a.example.:2083, using either
the AAAA or A addresses depending on the host configuration and its the AAAA or A addresses depending on the host configuration and its
IP stack's capabilities. IP stack's capabilities.
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
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* aaa+dynauth * aaa+dynauth
o Application Protocol Tags o Application Protocol Tags
* radius.tls * radius.tls
* radius.dtls * radius.dtls
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 [RFC3958] Daigle, L. and A. Newton, "Domain-Based
Application Service Location Using SRV RRs Application Service Location Using SRV RRs
and the Dynamic Delegation Discovery and the Dynamic Delegation Discovery Service
Service (DDDS)", RFC 3958, January 2005. (DDDS)", RFC 3958, January 2005.
[RFC5891] Klensin, J., "Internationalized Domain [RFC5580] Tschofenig, H., Adrangi, F., Jones, M.,
Names in Applications (IDNA): Protocol", Lior, A., and B. Aboba, "Carrying Location
RFC 5891, August 2010. Objects in RADIUS and Diameter", RFC 5580,
August 2009.
[I-D.dekok-radext-dtls] DeKok, A., "DTLS as a Transport Layer for [RFC5891] Klensin, J., "Internationalized Domain Names
RADIUS", draft-dekok-radext-dtls-03 (work in Applications (IDNA): Protocol", RFC 5891,
in progress), July 2010. August 2010.
[I-D.ietf-radext-radsec] Winter, S., McCauley, M., Venaas, S., and [I-D.dekok-radext-dtls] DeKok, A., "DTLS as a Transport Layer for
K. Wierenga, "TLS encryption for RADIUS", RADIUS", draft-dekok-radext-dtls-03 (work in
draft-ietf-radext-radsec-09 (work in progress), July 2010.
progress), July 2011.
[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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