Internet-Draft eap.arpa February 2024
DeKok Expires 28 August 2024 [Page]
Workgroup:
EMY Working Group
Internet-Draft:
draft-dekok-emu-eap-arpa-01
Updates:
9140 (if approved)
Published:
Intended Status:
Standards Track
Expires:
Author:
A. DeKok
FreeRADIUS

The eap.arpa domain and EAP provisioning

Abstract

This document defines the eap.arpa domain as a way for EAP peers to signal to EAP servers that they wish to obtain limited, and unauthenticated, network access. EAP peers leverage user identifier portion of the Network Access Identifier (NAI) format of RFC7542 in order to describe what kind of provisioning they need. A table of identifiers and meanings is defined.

About This Document

This note is to be removed before publishing as an RFC.

Status information for this document may be found at https://datatracker.ietf.org/doc/draft-dekok-emu-eap-arpa/.

Discussion of this document takes place on the EMU Working Group mailing list (mailto:emut@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/emut/. Subscribe at https://www.ietf.org/mailman/listinfo/emut/.

Source for this draft and an issue tracker can be found at https://github.com/freeradius/eap-arpa.git.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

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."

This Internet-Draft will expire on 28 August 2024.

1. Introduction

In most uses, EAP [RFC3748] requires that the EAP peer have a known identity. However, when the peer does not already have an identity, this requirement creates a bootstrapping problem. It may not be possible for the device to obtain network access without credentials. However, credentials are usually required in order to obtain network access. As a result, the device is unprovisioned, and unable to be provisioned.

This specification addresses that problem. It creates a framework by which clients can submit predefined credentials to a server in order to obtain limited network access. At the same time, servers can know in advance that these credentials are only to be used for provisioning, and that unrestricted network access should not be granted.

The device can either use the EAP channel itself for provisioning, as with TEAP [RFC7170], or the EAP server can give the device access to a limited captive portal such as with [RFC8952]. Once the device is provisioned, it can use those provisioned credentials to obtain full network access.

The identifiers used here are generically referred to as "EAP Provisioning Identifiers" (EPI). The choice of "Provisioning Identifiers for EAP" (PIE) was considered and rejected.

2. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

3. Concepts

A device which has no device-specific credentials can use a predefined identifier in Network Access Identifier (NAI) format [RFC7542]. The NAI is composed of two portions, the utf8-username, and the utf8-realm domain. For simplicity here, we refer to these as the "username" and "realm" fields.

The realm is chosen to be non-routable, so that the EAP packet exchange is not sent across an Authentication, Authorization, and Accounting (AAA) proxy framework as defined in [RFC7542] Section 3. Instead, the packets remains local to the EAP server. If the EAP server implements this standard, then it can proceed with the full EAP conversation. If the EAP server does not implement this standard, then it MUST reply with an EAP Failure, as per [RFC3748] Section 4.2.

We note that this specification is fully compatible with all existing EAP implementations, so its is fail-safe. When presented with a peer wishing to use this specification, existing implementations will return EAP Failure, and will not otherwise misbehave.

We now discuss the NAI format in more detail. We first discuss the eap.arpa realm, and second the use and purpose of the username field.

3.1. The eap.arpa realm

This document defines the "eap.arpa" domain as being used for provisioning within EAP. A similar domain has previously been used for EAP-NOOB [RFC9140], as "eap-noob.arpa". This document extends that concept, and standardizes the practices surrounding it,

NOTE: the "arpa" domain is controlled by the IAB. Allocation of "eap.arpa" requires agreement from the IAB.

3.2. The username field

The username field is assigned via the EAP Provisioning Identifier Registry which is defined below. The registry can either hold a fixed string such as "noob", or a prefix such as "V-". Prefixes give vendors and Service delivery organizations (SDOs) the ability to self-assign a delegated range of identifiers which cannot conflict with other identifiers.

The username field MUST NOT omitted. That is, "@eap.arpa" is not a valid identifier for the purposes of this specification. [RFC7542] recommends omitting the username portion for user privacy. As user privacy is not needed here, the username field can be publicly visible.

4. Overview

For EAP-TLS, both [RFC5216] Section 2.1.1 and [RFC9190] provide for "peer unauthenticated access". However, those documents define no way for a peer to signal that it is requesting such access. The presumption is that the peer connects with some value for the EAP Identity, but without using a client certificate. The EAP server is then supposed to determine that the peer is requesting unauthenticated access, and take the approprate steps to limit authorization.

There appears to be no EAP peer or server implementations which support such access, since there is no defined way to perform any of the steps required. i.e. to signal that this access is desired, and then limit access.

TBD: The Wireless Broadband Alliance (WBA) has defined an unauthenticated EAP-TLS method, using a vendor-specific EAP type. Get link.

EAP-NOOB [RFC9140] takes this process a step further. It defines both a way to signal that provisioning is desired, and also a way to exchange provisioning information within EAP-NOOB. That is, there is no need for the device to obtain limited network access, as all of the provisioning is done inside of the EAP-NOOB protocol.

TEAP [RFC7170] provides for provisioning via an unauthenticated TLS tunnel. There is a server unauthenticated provisioning mode (TBD), but the inner TLS exchange requires that both end authenticate each other. There are ways to provision a certificate, but the peer must still authenticate itself to the server.

4.1. Taxonomy of Provisioning Types

There are two scenarios where provisioning can be done. The first is where provisioning is done within the EAP type, as with EAP-NOOB [RFC9140]. The second is where EAP is used to obtain limited network access (e.g. as with a captive portal). That limited network access is then used to run Internet Protocol (IP) based provisioning over more complex protocols.

4.1.1. Rationale for Provisioning over EAP

It is often useful to do all provisioning inside of EAP, because the EAP / AAA admin does not have control over the network. It is not always possible to define a captive portal where provisioning can be done. As a result, we need to be able to perform provisioning via EAP, and not via some IP protocol.

5. Interaction with existing EAP types

As the provisioning identifer is used within EAP, it necessarily has interactions with, and effects on, the various EAP types. This section discusses those effects in more detail.

Some EAP methods require shared credentials such as passwords in order to succeed. For example, both EAP-MSCHAPv2 (PEAP) and EAP-PWD [RFC5931] perform cryptographic exchanges where both parties knowing a shared password. Where those methods are used, the password MUST be the same as the provisioning identifier.

This requirement also applies to TLS-based EAP methods such as TTLS and PEAP. Where the TLS-based EAP method provides for an inner identity and inner authentication method, the credentials used there MUST be the provisioning identifier for both the inner identity, and any inner password.

This process ensures that most EAP methods will work for provisioning, at the expense of potential security attacks. TBD - discuss.

It is RECOMMENDED that provisioning be done via a TLS-based EAP methods. TLS provides for authentication of the EAP server, along with security and confidentiality of any provisioning data exchanged in the tunnel. Similarly if provisioning is done in a captive portal outside of EAP, EAP-TLS permits the EAP peer to run a full EAP authentication session while having nothing more than a few certification authorities (CAs) locally configured.

5.1. EAP-TLS

This document defines an identifier "portal@eap.arpa", which is the first step towards permitted unauthenticated client provisioning in EAP-TLS. The purpose of the identifier is to allow EAP peers to signal EAP servers that they wish to obtain a "captive portal" style network access.

This identifier signals the EAP server that the peer wishes to obtain "peer unauthenticated access" as per [RFC5216] Section 2.1.1 and [RFC9190].

An EAP server which agrees to authenticate this request MUST ensure that the device is placed into a captive portal with limited network access. Further details of the captive portal architecture can be found in [RFC8952].

The remaining question is how the EAP peer verifies the identity of the EAP server. The device SHOULD ignore the EAP server certificate entirely, as the servers identity does not matter. Any verification of servers can be done at the HTTPS layer when the device access the captive portal. Where possible the device SHOULD warn the end user that the provided certificate is unchecked, and untrusted.

However, since the device likely is configured with web CAs (otherwise the captive portal would also be unauthenticated), EAP peers MAY use the CAs available for the web in order to validate the EAP server certificate. If the presented certificate passes validation, the device does not need to warn the end user that the provided certificate is untrusted.

5.2. TLS-based EAP methods

Other TLS-based EAP methods such as TTLS and PEAP can use the same method as defined for EAP-TLS above. The only difference is that the inner identity and password is also the provisioning identifier.

Is is RECOMMENDED that provisioning methods use EAP-TLS in preference to any other TLS-based EAP methods. As the credentials for other methods are predefined and known in advanc, those methods offer little benefit over EAP-TLS.

5.3. EAP-NOOB

It is RECOMMENDED that server implementations of EAP-NOOB accept both identities "noob@eap-noob.arpa" and "noob@eap.arpa" as synonyms.

It is RECOMMENDED that EAP-NOOB peers use "noob@eap.arpa" first, and if that does not succeed, use "noob@eap-noob.arpa"

@todo - what is the deployment of EAP-NOOB? Can we even make this recommendation?

6. IANA Considerations

Three IANA actions are required. The first two are registry updates for "eap.arpa". The second is the creation of a new registry.

6.1. .arpa updates

IANA is instructed to update the ".ARPA Zone Management" registry with the following entry:

DOMAIN

  • eap.arpa

USAGE

  • For provisioning within the Extensible Authentication Protocol framework.

REFERENCE

  • THIS-DOCUMENT

IANA is instructed to update the "Special-Use Domain Names" registry as follows:

NAME

  • eap.arpa

REFERENCE

  • THIS-DOCUMENT

6.1.1. Domain Name Reservation Considerations

This section answers the questions which are required by Section 5 of [RFC6761]. At a high level, these new domain names are used in certain situations in EAP. The domain names are never seen by users, and they do not appear in any networking protocol other than EAP.

  1. Users:

  • User are not expected to recognise these names as special or use them differently from other domain names. The use of these names in EAP is invisible to end users.

  1. Application Software:

  • EAP servers and clients are expected to make their software recognize these names as special and treat them differently. This document discusses that behavor.

    EAP supplicants should recognize these names as special, and should refuse to allow users to enter them in any interface.

  1. Name Resolution APIs and Libraries:

  • Writers of these APIs and libraries are not expected to recognize these names or treat them differently.

  1. Caching DNS Servers:

  • Writers of caching DNS servers are not expected to recognize these names or treat them differently.

  1. Authoritative DNS Servers:

  • Writers of authoritative DNS servers are not expected to recognize these names or treat them differently.

  1. DNS Server Operators:

  • These domain names have no impact on DNS server operators. They should never be used in DNS, or in any networking protocol outside of EAP.

    If they try to configure their authoritative DNS as authoritative for this reserved name, compliant name servers do not need to do anything special. They can accept the domain or reject it. Either behavior will have no impact on this specification.

  1. DNS Registries/Registrars:

  • DNS Registries/Registrars should deny requests to register this reserved domain name.

6.2. EAP Provisioning Identifier Registry

IANA is instructed to add the following new registry to the "Extensible Authentication Protocol (EAP) Registry" group.

Assignments in this registry are done via "Expert Review" as described in [RFC8126] Section 4.5.

The contents of the registry are as follows.

Title

  • EAP Provisioning Identifiers

Registration Procedure(s)

  • Expert review

Reference

  • THIS-DOCUMENT

Registry

  • Name

    • The name of the identifier. Names are listed in sorted order, case insensitive.

    Prefix

    • A boolean true/false flag indicating if this name is a prefix.

    Description

    • Description of the use-cases for this identifier.

    Reference

    • Reference where this identifier was defined.

6.2.1. Initial Values

The following table gives the initial values for this table.

Value,Prefix,Description,Reference

noob,false,EAP-NOOB,RFC9140 and THIS-DOCUMENT portal,false,generic captive portal,THIS-DOCUMENT V-,true,reserved for vendor self-assignment,THIS-DOCUMENT

6.3. Guidelines for Designated Experts

Identifiers and prefixes in the "Name" field of this registry MUST satisfy the "utf8-username" format defined in [RFC7542] Section 2.2.

Identifiers should be unique when compared in a case-insensitive fashion. While [RFC7542] notes that similar identifiers of different case can be considered to be different, this registry is made simpler by requiring case-insensitivity.

Identifiers and prefixes should be short. The NAIs created from these prefixes will generally be sent in a RADIUS packet in the User-Name attribute ([RFC2865] Section 5.1). That specification recommends that implementations should support User-Names of at least 63 octets. NAI length considerations are further discussed in [RFC7542] Section 2.3, and any allocations need to take those limitations into consideration.

Implementations are likely to support a total NAI length of 63 octets. Lengths between 63 and 253 octets may work. Lengths of 254 octets or more will not work with RADIUS [RFC2865].

For registration requests where a Designated Expert should be consulted, the responsible IESG area director should appoint the Designated Expert. The intention is that any non-prefix allocation will be accompanied by a published RFC. But in order to allow for the allocation of values prior to the RFC being approved for publication, the Designated Expert can approve allocations once it seems clear that an RFC will be published.

For allocation of a prefix, the Designated Expert should verify that the requested prefix clearly identifies the organization requesting the prefix, that there is a publicly available document from the organization which describes the prefix, and that the prefix ends with the "-" character.

Once a prefix has been assigned, it is not possible to perform further allocations in this registry which use that prefix. All such allocations have instead been delegated to the external organization.

The Designated expert will post a request to the EMU WG mailing list (or a successor designated by the Area Director) for comment and review, including an Internet-Draft or reference to external specification. Before a period of 30 days has passed, the Designated Expert will either approve or deny the registration request and publish a notice of the decision to the EAP WG mailing list or its successor, as well as informing IANA. A denial notice must be justified by an explanation, and in the cases where it is possible, concrete suggestions on how the request can be modified so as to become acceptable should be provided.

A short-hand summary of the requirements follows:

  • Identifiers and prefixes in the "Name" field of this registry MUST satisfy the "utf8-username" format defined in [RFC7542] Section 2.2.
  • Names MUST be unique, compared in a case-insensitive fashion.
  • Prefixes MUST NOT overlap with the beginning any other identifier. That is, if the prefix "foo-" has been allocated, then an identifier of "foo-bar" MUST NOT be allocated.
  • If the "prefix" flag is "false", then the Name field MUST NOT end with the "-" character.
  • If the "prefix" flag is "true", then the Name field MUST end with the "-" character.

6.3.1. Example of Vendor Self Assignment

Identifiers beginning with "V-" are for vendor self-assignment. The name MUST begin with the string "V-", following by 1 or more digits (0-9). The digits used here are taken from the vendor private enterprise number (PEN).

The name MUST then contain another "-" which delineates the vendor specific suffix namespace. The suffix is managed and allocated by the vendor, and does not need to be added to the registry.

The suffix is text which matches the "dot-string" definition of [RFC7542] Section 2.2.

For example, an identifier chosen by Cisco (PEN of 9) could be:

  • V-9-foo

Which then creates an NAI of the form:

  • V-9-foo@eap.arpa

6.3.2. Example of Service Delivery Organization

Service delivery organizations (SDOs) can request allocations of prefixes for use within their SDO. The prefix should be the name (abbreviated where possible) of the SDO, followed by a "-" character. The suffix is managed and allocated by the SDO, and does not need to be added to the registry.

The suffix is text which matches the "dot-string" definition of [RFC7542] Section 2.2.

For example, the 3rd Generation Partnership Project (3GPP) could request a prefix "3gpp-", and then self-assign a suffix "baz", to create an identifier:

  • 3gpp-baz

Which then creates an NAI of the form:

  • 3gpp-baz@eap.arpa

10. Changelog

  • 00 - initial version
  • 01 - add "Domain Name Reservation Considerations"

11. References

11.1. Normative References

[BCP14]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/rfc/rfc2119>.
[RFC3748]
Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. Levkowetz, Ed., "Extensible Authentication Protocol (EAP)", RFC 3748, DOI 10.17487/RFC3748, , <https://www.rfc-editor.org/rfc/rfc3748>.
[RFC5216]
Simon, D., Aboba, B., and R. Hurst, "The EAP-TLS Authentication Protocol", RFC 5216, DOI 10.17487/RFC5216, , <https://www.rfc-editor.org/rfc/rfc5216>.
[RFC7542]
DeKok, A., "The Network Access Identifier", RFC 7542, DOI 10.17487/RFC7542, , <https://www.rfc-editor.org/rfc/rfc7542>.
[RFC8126]
Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, , <https://www.rfc-editor.org/rfc/rfc8126>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC9140]
Aura, T., Sethi, M., and A. Peltonen, "Nimble Out-of-Band Authentication for EAP (EAP-NOOB)", RFC 9140, DOI 10.17487/RFC9140, , <https://www.rfc-editor.org/rfc/rfc9140>.
[RFC9190]
Preuß Mattsson, J. and M. Sethi, "EAP-TLS 1.3: Using the Extensible Authentication Protocol with TLS 1.3", RFC 9190, DOI 10.17487/RFC9190, , <https://www.rfc-editor.org/rfc/rfc9190>.

11.2. Informative References

[RFC2865]
Rigney, C., Willens, S., Rubens, A., and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, DOI 10.17487/RFC2865, , <https://www.rfc-editor.org/rfc/rfc2865>.
[RFC5931]
Harkins, D. and G. Zorn, "Extensible Authentication Protocol (EAP) Authentication Using Only a Password", RFC 5931, DOI 10.17487/RFC5931, , <https://www.rfc-editor.org/rfc/rfc5931>.
[RFC6761]
Cheshire, S. and M. Krochmal, "Special-Use Domain Names", RFC 6761, DOI 10.17487/RFC6761, , <https://www.rfc-editor.org/rfc/rfc6761>.
[RFC7170]
Zhou, H., Cam-Winget, N., Salowey, J., and S. Hanna, "Tunnel Extensible Authentication Protocol (TEAP) Version 1", RFC 7170, DOI 10.17487/RFC7170, , <https://www.rfc-editor.org/rfc/rfc7170>.
[RFC8952]
Larose, K., Dolson, D., and H. Liu, "Captive Portal Architecture", RFC 8952, DOI 10.17487/RFC8952, , <https://www.rfc-editor.org/rfc/rfc8952>.

Author's Address

Alan DeKok
FreeRADIUS