Internet DRAFT - draft-dekok-radext-nai
draft-dekok-radext-nai
Network Working Group DeKok, Alan
INTERNET-DRAFT FreeRADIUS
Obsoletes: 4282
Category: Standards Track
<draft-dekok-radext-nai-02.txt>
28 August 2012
The Network Access Identifier
draft-dekok-radext-nai-02
Abstract
In order to provide roaming services, it is necessary to have a
standardized method for identifying users. This document defines the
syntax for the Network Access Identifier (NAI), the user identity
submitted by the client during network authentication. "Roaming" may
be loosely defined as the ability to use any one of multiple Internet
Service Providers (ISPs), while maintaining a formal, customer-vendor
relationship with only one. Examples of where roaming capabilities
might be required include ISP "confederations" and ISP-provided
corporate network access support. This document is a revised version
of RFC 4282 [RFC4282], which addresses issues with international
character sets, as well as a number of other corrections to the
previous document.
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.
Internet-Drafts are draft documents valid for a maximum of six months
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 February 28, 2013.
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Copyright Notice
Copyright (c) 2012 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
(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.
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Table of Contents
Appendix A - Changes from RFC4282 ............................ 3
1. Introduction ............................................. 4
1.1. Terminology ......................................... 4
1.2. Requirements Language ............................... 5
1.3. Purpose ............................................. 6
1.4. Motivation .......................................... 6
2. NAI Definition ........................................... 7
2.1. UTF-8 Syntax and Normalization ...................... 7
2.2. Formal Syntax ....................................... 7
2.3. NAI Length Considerations ........................... 8
2.4. Support for Username Privacy ........................ 8
2.5. International Character Sets ........................ 9
2.6. The Normalization Process ........................... 10
2.7. Routing inside of AAA Systems ....................... 10
2.8. Compatibility with Email Usernames .................. 11
2.9. Compatibility with DNS .............................. 11
2.10. Realm Construction ................................. 12
2.10.1. Historical Practices .......................... 13
2.11. Examples ........................................... 13
3. Security Considerations .................................. 14
4. IANA Considerations ...................................... 15
5. References ............................................... 15
5.1. Normative References ................................ 15
5.2. Informative References .............................. 16
Appendix A - Changes from RFC4282 ............................ 18
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1. Introduction
Considerable interest exists for a set of features that fit within
the general category of "roaming capability" for network access,
including dialup Internet users, Virtual Private Network (VPN) usage,
wireless LAN authentication, and other applications. Interested
parties have included the following:
o Regional Internet Service Providers (ISPs) operating within a
particular state or province, looking to combine their efforts
with those of other regional providers to offer dialup service
over a wider area.
o National ISPs wishing to combine their operations with those of
one or more ISPs in another nation to offer more comprehensive
dialup service in a group of countries or on a continent.
o Wireless LAN hotspots providing service to one or more ISPs.
o Businesses desiring to offer their employees a comprehensive
package of dialup services on a global basis. Those services may
include Internet access as well as secure access to corporate
intranets via a VPN, enabled by tunneling protocols such as the
Point-to-Point Tunneling Protocol (PPTP) [RFC2637], the Layer 2
Forwarding (L2F) protocol [RFC2341], the Layer 2 Tunneling
Protocol (L2TP) [RFC2661], and the IPsec tunnel mode [RFC4301].
In order to enhance the interoperability of roaming services, it is
necessary to have a standardized method for identifying users. This
document defines syntax for the Network Access Identifier (NAI).
Examples of implementations that use the NAI, and descriptions of its
semantics, can be found in [RFC2194].
This document is a revised version of [RFC4282], which originally
defined internationalized NAIs. Differences and enhancements
compared to that document are listed in Appendix A.
1.1. Terminology
This document frequently uses the following terms:
Network Access Identifier
The Network Access Identifier (NAI) is the user identity submitted
by the client during network access authentication. In roaming,
the purpose of the NAI is to identify the user as well as to
assist in the routing of the authentication request. Please note
that the NAI may not necessarily be the same as the user's email
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address or the user identity submitted in an application layer
authentication.
Network Access Server
The Network Access Server (NAS) is the device that clients connect
to in order to get access to the network. In PPTP terminology,
this is referred to as the PPTP Access Concentrator (PAC), and in
L2TP terminology, it is referred to as the L2TP Access
Concentrator (LAC). In IEEE 802.11, it is referred to as an
Access Point.
Roaming Capability
Roaming capability can be loosely defined as the ability to use
any one of multiple Internet Service Providers (ISPs), while
maintaining a formal, customer-vendor relationship with only one.
Examples of cases where roaming capability might be required
include ISP "confederations" and ISP-provided corporate network
access support.
Tunneling Service
A tunneling service is any network service enabled by tunneling
protocols such as PPTP, L2F, L2TP, and IPsec tunnel mode. One
example of a tunneling service is secure access to corporate
intranets via a Virtual Private Network (VPN).
1.2. Requirements Language
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 [RFC2119].
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1.3. Purpose
As described in [RFC2194], there are a number of providers offering
network access services, and the number of Internet Service Providers
involved in roaming consortia is increasing rapidly.
In order to be able to offer roaming capability, one of the
requirements is to be able to identify the user's home authentication
server. For use in roaming, this function is accomplished via the
Network Access Identifier (NAI) submitted by the user to the NAS in
the initial network authentication. It is also expected that NASes
will use the NAI as part of the process of opening a new tunnel, in
order to determine the tunnel endpoint.
1.4. Motivation
The changes from [RFC4282] are listed in detail in Appendix A.
However, some additional discussion is appropriate to motivate those
changes.
The motivation to revise [RFC4282] began with internationalization
concerns raised in the context of [EDUROAM]. Section 2.1 of
[RFC4282] defines ABNF for realms which limits the realm grammar to
English letters, digits, and the hyphen "-" character. The intent
appears to have been to encode, compare, and transport realms with
the ToASCII operation defined in [RFC5890]. There are a number of
problems with this approach:
o The requirement in Section 2.1 that realms are ASCII conflicts
with the Extensible Authentication Protocol (EAP) and RADIUS,
which are both 8-bit clean, and which both recommend the use of
UTF-8 for identities.
o Section 2.4 required mappings that are language-specific,
and which are nearly impossible for intermediate nodes to perform
correctly without information about that language.
o Section 2.4 requires normalization of user names, which
may conflict with local system or administrative requirements.
o The recommendations in Section 2.4 for treatment of
bidirectional characters have proven to be unworkable.
o The prohibition against use of unassigned code points in
Section 2.4 effectively prohibits support for new scripts.
o No Authentication, Authorization, and Accounting (AAA)
client, proxy, or server has implemented any of the requirements
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in [RFC4282] Section 2.4, among other sections.
With international roaming growing in popularity, it is important for
these issues to be corrected in order to provide robust and inter-
operable network services.
2. NAI Definition
2.1. UTF-8 Syntax and Normalization
UTF-8 characters can be defined in terms of octets using the
following ABNF [RFC5234], taken from [RFC3629]:
UTF8-xtra-char = UTF8-2 / UTF8-3 / UTF8-4
UTF8-2 = %xC2-DF UTF8-tail
UTF8-3 = %xE0 %xA0-BF UTF8-tail /
%xE1-EC 2(UTF8-tail) /
%xED %x80-9F UTF8-tail /
%xEE-EF 2(UTF8-tail)
UTF8-4 = %xF0 %x90-BF 2( UTF8-tail ) /
%xF1-F3 3( UTF8-tail ) /
%xF4 %x80-8F 2( UTF8-tail )
UTF8-tail = %x80-BF
These are normatively defined in [RFC3629], but are repeated in this
document for reasons of convenience.
See [RFC5198] for a discussion of normalization; implementations of
this specification MUST use the Normal Form Composed (NFC) for NAIs.
2.2. Formal Syntax
The grammar for the NAI is given below, described in Augmented
Backus-Naur Form (ABNF) as documented in [RFC5234].
nai = utf8-username
nai =/ "@" utf8-realm
nai =/ utf8-username "@" utf8-realm
utf8-username = dot-string
dot-string = string
dot-string =/ dot-string "." string
string = utf8-atext
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string =/ string utf8-atext
utf8-atext = ALPHA / DIGIT /
"!" / "#" /
"$" / "%" /
"&" / "'" /
"*" / "+" /
"-" / "/" /
"=" / "?" /
"^" / "_" /
"`" / "{" /
"|" / "}" /
"~" /
UTF8-xtra-char
utf8-realm = 1*( label "." ) label
label = utf8-rtext *(ldh-str)
ldh-str = *( utf8-rtext / "-" ) utf8-rtext
utf8-rtext = ALPHA / DIGIT / UTF8-xtra-char
2.3. NAI Length Considerations
Devices handling NAIs MUST support an NAI length of at least 72
octets. Devices SHOULD support an NAI length of 253 octets.
However, the following implementation issues should be considered:
o NAIs are often transported in the User-Name attribute of the
Remote Authentication Dial-In User Service (RADIUS) protocol.
Unfortunately, RFC 2865 [RFC2865], Section 5.1, states that "the
ability to handle at least 63 octets is recommended." As a
result, it may not be possible to transfer NAIs beyond 63 octets
through all devices. In addition, since only a single User-Name
attribute may be included in a RADIUS message and the maximum
attribute length is 253 octets; RADIUS is unable to support NAI
lengths beyond 253 octets.
o NAIs can also be transported in the User-Name attribute of
Diameter [RFC3588], which supports content lengths up to 2^24 - 9
octets. As a result, NAIs processed only by Diameter nodes can be
very long. However, an NAI transported over Diameter may
eventually be translated to RADIUS, in which case the above
limitations will apply.
2.4. Support for Username Privacy
Interpretation of the username part of the NAI depends on the realm
in question. Therefore, the utf8-username portion SHOULD be treated
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as opaque data when processed by nodes that are not a part of the
authoritative domain (in the sense of Section 4) for that realm.
In some situations, NAIs are used together with a separate
authentication method that can transfer the username part in a more
secure manner to increase privacy. In this case, NAIs MAY be
provided in an abbreviated form by omitting the username part.
Omitting the username part is RECOMMENDED over using a fixed username
part, such as "anonymous", since it provides an unambiguous way to
determine whether the username is intended to uniquely identify a
single user.
For roaming purposes, it is typically necessary to locate the
appropriate backend authentication server for the given NAI before
the authentication conversation can proceed. As a result, the realm
portion is typically required in order for the authentication
exchange to be routed to the appropriate server.
2.5. International Character Sets
This specification allows both international usernames and realms.
International usernames are based on the use of Unicode characters,
encoded as UTF-8. Internationalization of the realm portion of the
NAI is based on "Internationalized Email Headers" [RFC5335].
In order to ensure a canonical representation, characters of the
username portion in an NAI MUST match the ABNF in this specification
as well as the requirements specified in [RFC5891]. In practice,
these requirements consist of the following item:
o Realms MUST be of the form that can be registered as a
Fully Qualified Domain Name (FQDN) within the DNS name system.
This list is significantly shorter and simpler than the list in
Section 2.4 of [RFC4282]. The form suggested in [RFC4282] depended
on intermediate nodes performing canonicalizations based on
insufficient information, which meant that the form was not
canonical. This document instead suggests (Section 2.10) that the
realm owner provide a canonical form of the realm, and that all
intermediate nodes use that form without modification.
Specifying the realm requirement as above means that the requirements
depend on specifications that are referenced here, rather than copied
here. This allows the realm definition to be updated when the
referenced documents change, without requiring a revision of this
specification.
In general, the above requirement means following the requirements as
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specified in [RFC5891]. However, that document is in flux at the
time of this writing, and the issues with [RFC4282] mandate a timely
update to it.
2.6. The Normalization Process
All normalization MUST be performed by end systems that take "local"
text as input. That is, text that is in an encoding other than
UTF-8, or that has locale-specific variations. In a network access
setting, such systems are typically the client (e.g. EAP supplicant)
and the Authentication, Authorization, and Accounting (AAA) server.
All other AAA systems (proxies, etc.) MUST NOT perform
normalization. These other systems do not have access to locale and
character set information that is available to end systems.
That is, all processing of NAIs from "local" character sets and
locales to UTF-8 is performed by edge systems, prior to the NAIs
entering the AAA system. Inside of an AAA system, NAIs are sent over
the wire in their canonical form, and this canonical form is used for
all NAI and/or realm comparisons.
In contrast to the comments in [RFC4282] Section 2.4, we expect AAA
systems to perform NAI comparisons, matching, and AAA routing based
on the NAI as it is received. This specification provides a
canonical representation, ensures that intermediate systems such as
AAA proxies do not need to perform translations, and can be expected
to work through systems that are unaware of international character
sets.
For example, much of the common realm routing can be done on the
"utf8-realm" portion of NAI, through simple checks for equality.
This routing can be done even if the AAA proxy is unaware of
internalized domain names. All that is required is for the AAA proxy
to be able to enter, store, and compare 8-bit data.
EAP supplicants MUST normalize user names that get placed in the EAP-
Response/Identity field. They MUST NOT copy localized text into that
field. This normalization SHOULD be performed once, and then cached
for subsequent use.
2.7. Routing inside of AAA Systems
Many systems require that the "utf8-realm" portion of the NAI be used
to route requests within a AAA proxy network. The semantics of this
operation involves a logical AAA routing table, where the
"utf8-realm" portion acts as a key, and the values stored in the
table are one or more "next hop" AAA servers.
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Intermediate nodes MUST use the "utf8-realm" portion of the NAI
without modification to perform this lookup. Comparisons between the
NAI as given in a AAA packet, and as provisioned in a logical AAA
routing table SHOULD be done as a byte-for-byte equality test. The
"utf8-realm" provisioned in the logical AAA routing table SHOULD be
provisioned prior to the proxy receiving any AAA traffic, and SHOULD
be supplied by the "next hop" system that also supplies the other
information about the next hop.
This "next hop" information may be IP address, port, RADIUS shared
secret, TLS certificates, or a DNS host name.
2.8. Compatibility with Email Usernames
As proposed in this document, the Network Access Identifier is of the
form user@realm. Please note that while the user portion of the NAI
is based on the BNF described in [RFC5198], it has been modified for
the purposes of Section 2.2. It does not permit quoted text along
with "folding" or "non-folding" whitespace that is commonly used in
email addresses. As such, the NAI is not necessarily equivalent to
usernames used in e-mail.
However, it is a common practice to use email addresses as user
identifiers in AAA systems. The ABNF in Section 2.2 is defined to be
close to the "utf8-addr-spec" portion of [RFC5335], while still being
compatible with [RFC4282].
In contrast to the comments in [RFC4282] Section 2.5, we state that
the internationalization requirements for NAIs and email addresses
are substantially similar. The NAI and email identifiers may be the
same, and both need to be entered by the user and/or the operator
supplying network access to that user. There is therefore good
reason for the internationalization requirements to be similar.
2.9. Compatibility with DNS
The "realm" portion of the NAI is intended to be compatible with
domain names used in DNS systems. However, the "realm" portion
within AAA systems is intended to be a UTF-8 string, not an ASCII
string as with the DNS protocol. Therefore, AAA systems transporting
NAIs in an AAA protocol MUST NOT encode the "utf8-realm" portion
using the ToAscii function. That function creates strings that may
be transported over DNS, and it is not appropriate for use within an
AAA protocol.
When the realm portion of the NAI is used as the basis for name
lookups within the DNS system, the ToASCII operation defined in
[RFC5890] MAY be used to convert internationalized realm names to
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ASCII. This function is normally handled by a DNS resolver library
on the local system. When this function is not handled by a DNS
resolver library, the AAA system MAY perform the ToAscii conversion
itself, before passing the modified realm name to the DNS resolver
library.
There is, however, a problem with this approach. A AAA proxy may not
have sufficient information in order to perform the ToAscii
conversion properly. We therefore RECOMMEND that only the owner of
the realm perform the ToAscii conversion. We RECOMMEND that the
owner of the realm pre-provision all proxies with the "utf8-realm"
portion of the NAI, along with the value returned from passing the
"utf8-realm" to the ToAscii function. This key-value pair can then
be placed into logical AAA routing table discussed above. Having
only one entity run the ToAscii function ensures that the result
returned by that function are considered as canonical form by all
other participants in a AAA network.
The paragraph above does not negate all of the benefits of using DNS
to automatically discover the location of a "next hop" AAA server.
Many AAA proxies require a business or legal relationship prior to
routing any traffic. This relationship can be leveraged to bootstrap
the DNS information located in the logical AAA routing table.
2.10. Realm Construction
The home realm usually appears in the realm portion of the NAI, but
in some cases a different realm can be used. This may be useful, for
instance, when the home realm is reachable only via intermediate
proxies.
Such usage may prevent interoperability unless the parties involved
have a mutual agreement that the usage is allowed. In particular,
NAIs MUST NOT use a different realm than the home realm unless the
sender has explicit knowledge that (a) the specified other realm is
available and (b) the other realm supports such usage. The sender
may determine the fulfillment of these conditions through a database,
dynamic discovery, or other means not specified here. Note that the
first condition is affected by roaming, as the availability of the
other realm may depend on the user's location or the desired
application.
The use of the home realm MUST be the default unless otherwise
configured.
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2.10.1. Historical Practices
Some systems have historically used NAI modifications with multiple
"prefix" and "suffix" decorations to perform explicit routing through
multiple proxies inside of a AAA network. This practice is NOT
RECOMMENDED for the following reasons:
o Using explicit routing paths is fragile, and is unresponsive to
changes in the network due to servers going up or down, or to
changing business relationships.
o There is no RADIUS routing protocol, meaning that routing paths
have to be communicated "out of band" to all intermediate AAA
nodes, and also to all end-user systems (supplicants) expecting to
obtain network access.
o Using explicit routing paths requires thousands, if not
millions of end-user systems to be updated with new path
information when a AAA routing path changes. This adds huge
expense for updates that would be better done at only a few AAA
systems in the network.
o Manual updates to RADIUS paths are expensive, time-consuming,
and prone to error.
o Re-writing of the User-Name in AAA servers means that it may not
match the EAP-Response/Identity fields. This mismatch may cause
the home AAA server to reject the request as being malformed.
o Creating compatible formats for the NAI is difficult
when locally-defined "prefixes" and "suffixes" conflict with
similar practices elsewhere in the network. These conflicts mean
that connecting two networks may be impossible in some cases, as
there is no way for packets to be routed properly in a way that
meets all requirements at all intermediate proxies.
o Leveraging the DNS name system for realm names establishes
a globally unique name space for realms.
In summary, network practices and capabilities have changed
significantly since NAIs were first overloaded to define AAA routes
through a network. While explicit path routing was once useful, the
time has come for better methods to be used.
2.11. Examples
Examples of valid Network Access Identifiers include the following:
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bob
joe@example.com
fred@foo-9.example.com
jack@3rd.depts.example.com
fred.smith@example.com
fred_smith@example.com
fred$@example.com
fred=?#$&*+-/^smith@example.com
nancy@eng.example.net
eng.example.net!nancy@example.net
eng%nancy@example.net
@privatecorp.example.net
\(user\)@example.net
Examples of invalid Network Access Identifiers include the following:
fred@example
fred@example_9.com
fred@example.net@example.net
fred.@example.net
eng:nancy@example.net
eng;nancy@example.net
(user)@example.net
<nancy>@example.net
One example given in [RFC4282] is still permitted by the ABNF, but it
is NOT RECOMMMENDED because of the use of the ToAscii function to
create an ASCII encoding from what is now a valid UTF-8 string.
alice@xn--tmonesimerkki-bfbb.example.net
3. Security Considerations
Since an NAI reveals the home affiliation of a user, it may assist an
attacker in further probing the username space. Typically, this
problem is of most concern in protocols that transmit the username in
clear-text across the Internet, such as in RADIUS, described in
[RFC2865] and [RFC2866]. In order to prevent snooping of the
username, protocols may use confidentiality services provided by
protocols transporting them, such as RADIUS protected by IPsec
[RFC3579] or Diameter protected by TLS [RFC3588].
This specification adds the possibility of hiding the username part
in the NAI, by omitting it. As discussed in Section 2.4, this is
possible only when NAIs are used together with a separate
authentication method that can transfer the username in a secure
manner. In some cases, application-specific privacy mechanism have
also been used with NAIs. For instance, some EAP methods apply
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method-specific pseudonyms in the username part of the NAI [RFC3748].
While neither of these approaches can protect the realm part, their
advantage over transport protection is that privacy of the username
is protected, even through intermediate nodes such as NASes.
4. IANA Considerations
In order to avoid creating any new administrative procedures,
administration of the NAI realm namespace piggybacks on the
administration of the DNS namespace.
NAI realm names are required to be unique, and the rights to use a
given NAI realm for roaming purposes are obtained coincident with
acquiring the rights to use a particular Fully Qualified Domain Name
(FQDN). Those wishing to use an NAI realm name should first acquire
the rights to use the corresponding FQDN. Using an NAI realm without
ownership of the corresponding FQDN creates the possibility of
conflict and is therefore discouraged.
Note that the use of an FQDN as the realm name does not require use
of the DNS for location of the authentication server. While Diameter
[RFC3588] supports the use of DNS for location of authentication
servers, existing RADIUS implementations typically use proxy
configuration files in order to locate authentication servers within
a domain and perform authentication routing. The implementations
described in [RFC2194] did not use DNS for location of the
authentication server within a domain. Similarly, existing
implementations have not found a need for dynamic routing protocols
or propagation of global routing information. Note also that there
is no requirement that the NAI represent a valid email address.
5. References
5.1. Normative References
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March, 1997.
[RFC3629]
Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD 63,
RFC 3629, November 2003.
[RFC5198]
Klensin J., and Padlipsky M., "Unicode Format for Network
Interchange", RFC 5198, March 2008
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[RFC5234]
Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 5234, January 2008.
[RFC5890]
Faltstrom, P., Hoffman, P., and A. Costello, "Internationalizing
Domain Names in Applications (IDNA)", RFC 5890
5.2. Informative References
[RFC2194]
Aboba, B., Lu, J., Alsop, J., Ding, J., and W. Wang, "Review of
Roaming Implementations", RFC 2194, September 1997.
[RFC2341]
Valencia, A., Littlewood, M., and T. Kolar, "Cisco Layer Two
Forwarding (Protocol) "L2F"", RFC 2341, May 1998.
[RFC2637]
Hamzeh, K., Pall, G., Verthein, W., Taarud, J., Little, W., and G.
Zorn, "Point-to-Point Tunneling Protocol", RFC 2637, July 1999.
[RFC2661]
Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn, G., and B.
Palter, "Layer Two Tunneling Protocol "L2TP"", RFC 2661, August
1999.
[RFC2865]
Rigney, C., Willens, S., Rubens, A. and W. Simpson, "Remote
Authentication Dial In User Service (RADIUS)", RFC 2865, June 2000.
[RFC2866]
Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.
[RFC3579]
Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication Dial In
User Service) Support For Extensible Authentication Protocol
(EAP)", RFC 3579, September 2003.
[RFC3588]
Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. Arkko,
"Diameter Base Protocol", RFC 3588, September 2003.
[RFC3748]
Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, "Extensible Authentication Protocol (EAP)", RFC 3748,
June 2004.
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[RFC4282]
Aboba, B. et al., "The Network Access Identifier", RFC 4282,
December 2005.
[RFC4301]
Kent, S. and S. Keo, "Security Architecture for the Internet
Protocol", RFC 4301, December 2005.
[RFC5335]
Y. Abel, Ed., "Internationalized Email Headers", RFC 5335,
September 2008.
[EDUROAM]
http://eduroam.org, "eduroam (EDUcational ROAMing)"
[RFC5891]
Klensin, J., "Internationalized Domain Names in Applications
(IDNA): Protocol", RFC 5891
Acknowledgments
The initial text for this document was [RFC4282], which was then
heavily edited. The original authors of [RFC4282] were Bernard
Aboba, Mark A. Beadles, Jari Arkko, and Pasi Eronen.
The ABNF validator at http://www.apps.ietf.org/abnf.html was used to
verify the syntactic correctness of the ABNF in Section 2.
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Appendix A - Changes from RFC4282
This document contains the following updates with respect to the
previous NAI definition in RFC 4282 [RFC4282]:
o The formal syntax in Section 2.1 has been updated to forbid
non-UTF8 characters. e.g. characters with the "high bit" set.
o The formal syntax in Section 2.1 has been updated to allow
UTF-8 in the "realm" portion of the NAI.
o The formal syntax in [RFC4282] Section 2.1 applied to the
NAI after it was "internationalized" via the ToAscii function.
The contents of the NAI before it was "internationalized" were
left indeterminate. This document updates the formal syntax to
define an internationalized form of the NAI, and forbids the use
of the ToAscii function for NAI "internationalization".
o The grammar for the user and realm portion is based on a
combination
of the "nai" defined in [RFC4282] Section 2.1, and the "utf8-addr-
spec" defined in [RFC5335] Section 4.4.
o All use of the ToAscii function has been moved to normal
requirements on DNS implementations when realms are used as the
basis for DNS lookups. This involves no changes to the existing
DNS infrastructure.
o The discussions on internationalized character sets in Section 2.4
have been updated. The suggestion to use the ToAscii function for
realm comparisons has been removed. No AAA system implemented the
suggestion, so this change should have no operational impact.
o The section "Routing inside of AAA Systems" section is new in this
document. The concept of a "local AAA routing table" is also new,
although it accurately describes the functionality of wide-spread
implementations.
o The "Compatibility with EMail Usernames" and "Compatibility
with DNS" sections have been revised and updated. We now note
that the ToAscii function is required to be used only when a realm
name is used for DNS lookups, and even then the function is only
used by a DNS resolving library on the local system, and even then
we recommend that only the home network perform this conversion.
o The "Realm Construction" section has been updated to note
that editing of the NAI is NOT RECOMMENDED.
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o The "Examples" section has been updated to remove the instance
of the IDN being converted to ASCII. This behavior is now
forbidden.
Authors' Addresses
Alan DeKok
The FreeRADIUS Server Project
Email: aland@freeradius.org
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