The eap.arpa domain and EAP provisioning
draft-ietf-emu-eap-arpa-08

EMU Working Group                                               A. DeKok
Internet-Draft                                        InkBridge Networks
Updates: 5216, 9140, 9190 (if approved)                      6 July 2025
Intended status: Standards Track                                        
Expires: 7 January 2026

                The eap.arpa domain and EAP provisioning
                       draft-ietf-emu-eap-arpa-08

Abstract

   This document defines the eap.arpa domain for use only in Network
   Access Identifiers (NAIs) as a way for Extensible Authentication
   Protocol (EAP) peers to signal to EAP servers that they wish to
   obtain limited, and unauthenticated, network access.  EAP peers
   signal which kind of access is required via certain predefined
   identifiers which use the Network Access Identifier (NAI) format of
   RFC 7542.  A table of identifiers and meanings is defined, which
   includes entries for RFC 9140.

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-ietf-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/.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  The eap.arpa realm  . . . . . . . . . . . . . . . . . . .   5
     3.2.  The realm field . . . . . . . . . . . . . . . . . . . . .   5
     3.3.  The username field  . . . . . . . . . . . . . . . . . . .   6
     3.4.  Operation . . . . . . . . . . . . . . . . . . . . . . . .   6
       3.4.1.  EAP Peer  . . . . . . . . . . . . . . . . . . . . . .   6
       3.4.2.  EAP Servers . . . . . . . . . . . . . . . . . . . . .   8
     3.5.  Other Considerations  . . . . . . . . . . . . . . . . . .   9
     3.6.  Considerations for Provisioning Specifications  . . . . .  10
       3.6.1.  Negotiation . . . . . . . . . . . . . . . . . . . . .  10
       3.6.2.  Renewal of Credentials  . . . . . . . . . . . . . . .  10
     3.7.  Notes on AAA Routability  . . . . . . . . . . . . . . . .  10
   4.  Background and Rationale  . . . . . . . . . . . . . . . . . .  11
     4.1.  Review of Existing Functionality  . . . . . . . . . . . .  11
     4.2.  Taxonomy of Provisioning Types  . . . . . . . . . . . . .  12
       4.2.1.  Rationale for Provisioning over EAP . . . . . . . . .  12
   5.  Interaction with EAP Methods  . . . . . . . . . . . . . . . .  12
     5.1.  High Level Requirements . . . . . . . . . . . . . . . . .  13
     5.2.  EAP-TLS . . . . . . . . . . . . . . . . . . . . . . . . .  13
     5.3.  EAP-NOOB  . . . . . . . . . . . . . . . . . . . . . . . .  14
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
     6.1.  .arpa updates . . . . . . . . . . . . . . . . . . . . . .  14
       6.1.1.  Deprecating eap-noob.arpa . . . . . . . . . . . . . .  14

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       6.1.2.  Defining eap.arpa . . . . . . . . . . . . . . . . . .  15
     6.2.  EAP Provisioning Identifiers Registry . . . . . . . . . .  16
       6.2.1.  Initial Values  . . . . . . . . . . . . . . . . . . .  17
     6.3.  Guidelines for Designated Experts . . . . . . . . . . . .  17
       6.3.1.  NAIs  . . . . . . . . . . . . . . . . . . . . . . . .  18
     6.4.  Method Type . . . . . . . . . . . . . . . . . . . . . . .  18
     6.5.  Designated Experts  . . . . . . . . . . . . . . . . . . .  19
     6.6.  Organization Self Assignment  . . . . . . . . . . . . . .  19
   7.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  20
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  20
     8.1.  On-Path Attackers and Impersonation . . . . . . . . . . .  21
     8.2.  Provisioning is Unauthenticated . . . . . . . . . . . . .  21
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  22
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  22
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  22
     10.2.  Informative References . . . . . . . . . . . . . . . . .  23
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  24

1.  Introduction

   In most uses, EAP [RFC3748] requires that the EAP peer have pre-
   provisioned credentials.  Without credentials, the device cannot
   obtain network access in order to be provisioned with credentials.
   This limitation creates a bootstrapping problem.

   This specification addresses that bootstrapping problem.  It creates
   a framework for predefined "well-known" provisioning credentials, and
   instantiates that framework for two mechanisms.

   Clients can submit these predefined provisioning credentials to a
   server in order to obtain limited network access.  At the same time,
   servers can know in advance that these credentials are to be used
   only for provisioning, and avoid granting unrestricted network access
   to peers which submit these credentials.

   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 predefined provisioning credentials use a generic identity
   format.  Identifiers in this space are generically referred to as
   "EAP Provisioning Identifiers" (EPI).

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   Since the identity is predefined and used only for unauthenticated
   network access, there is little benefit to specifying predefined
   passwords.  Where supported by the underlying EAP method, this
   specification provides for password-less access.  Where passwords are
   required, the password is defined to be the same as the identity.

2.  Terminology

   EAP Provisioning Identifier (EPI)

      The EAP Provisioning Identifier (EPI) is defined to be a strict
      subset of the Network Access Identifier [RFC7542].  The EPI is an
      NAI which ends with "eap.arpa".  The domain or "realm" portion of
      the NAI is defined in [RFC7542], Section 2.2, which is a more
      restrictive subset of the domain name conventions specified in
      RFC1034.

   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.  Overview

   A device which has no device-specific credentials can use a
   predefined provisioning 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 independent of, and unused by, any existing
   organization, and thus to be usable by all organizations.  The realm
   needs to be one which is not automatically proxied by any existing
   Authentication, Authorization, and Accounting (AAA) proxy framework
   as defined in [RFC7542], Section 3.  The realm also needs to be one
   which does not return results for [RFC7585] dynamic discovery.

   This specification does not, however, forbid routing of packets for
   realms in the "eap.arpa" domain.  Instead, it leaves such routing up
   to individual organizations.

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

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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.

   RFC-EDITOR: This text can be updated on publication to indicate that
   the IAB has approved it.

3.2.  The realm field

   The NAIs defined by this specification use the [RFC7542] "realm"
   field to signal the behavior being requested; in particular, the
   subdomain under eap.arpa allows for different requested methods to be
   distinguished.  The subdomain in the realm field is assigned via the
   EAP Provisioning Identifier Registry, which is defined in
   Section 6.2.  The subdomain MUST follow the syntax defined in
   [RFC7542], Section 2.2, which is a more restrictive subset of the
   domain name conventions specified in RFC1034.

   It is RECOMMENDED that the first subdomain of "eap.arpa" use the EAP
   method name, as defined in the IANA Extensible Authentication
   Protocol (EAP) Registry, sub-registry "Method Types".  However, that
   registry does not follow the domain name conventions specified in
   RFC1034, so it is not possible to make a "one-to-one" mapping between
   the Method Type name and the subdomain.

   Where it is not possible to make a direct mapping between the EAP
   Method Type name due to the EAP Method Type name not matching the
   [RFC7542], Section 2.2 format, the name used in the realm registry
   SHOULD be similar enough to allow the average reader to understand
   which EAP Method Type is being used.

   Additional subdomains are permitted in the realm, which permit
   vendors and Standards Development organizations (SDOs) the ability to
   self-assign a delegated range of identifiers which do not conflict
   with other identifiers.

   Any realm defined in this registry (e.g. "tls.eap.arpa") also
   implicitly defines a subdomain "v." (e.g. "v.tls.eap.arpa").  Vendors
   or SDOs can self-allocate within the "v." subdomain, using domains
   which they own.  For example, An "example.com" company could self-
   allocate and use the realm "example.com.v.tls.eap.arpa".  See
   Section 6.6 for more discussion of this topic.

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3.3.  The username field

   The username field is dependent on the EAP method being used for
   provisioning.  For example, [RFC9140] uses the username "noob".
   Other EAP methods MAY omit the username as RECOMMENDED in [RFC7542].
   The username of "anonymous" is NOT RECOMMENDED for specifications
   using this format, even though it is permitted by [RFC7542].  The
   name "anonymous" is widely used in NAIs today, and we wish to avoid
   confusion.

   The username field is assigned via the EAP Provisioning Identifier
   Registry which is defined in Section 6.2.  The username field MAY be
   empty, or else hold a fixed value.  While [RFC7542] recommends
   omitting the username portion for user privacy, the names here are
   defined in public specifications.  User privacy is therefore not
   needed for provisioning identifiers, and the username field can be
   publicly visible.

3.4.  Operation

   Having described the format and contents of NAIs in the eap.arpa
   realm to define the EAP Provisioning Identifier (EPI), we now
   describe how those EPIs are used by EAP peers and EAP peers to signal
   provisioning information

3.4.1.  EAP Peer

   An EAP peer signals that it wishes a certain kind of provisioning by
   using an EPI, along with an associated EAP method.  The meaning of
   the EPI, and behavior of the peer, are defined by a separate
   specification.  That specification will typically define both the
   EPI, and the EAP method or methods which are used for provisioning.

   The EPI used by the peer MUST be taken from an entry in the "EAP
   Provisioning Identifiers" registry, and the EAP method used with that
   NAI MUST match the corresponding EAP method from that same entry.

   Where an EAP peer allows local selection of a provisioning method,
   the choice of EPI is defined by the provisioning method.  As a
   result, the EAP peer MUST NOT have a field which lets the user
   identifier field be configured directly.  Instead the user (or some
   other process) chooses a provisioning method, and the peer then
   chooses an EPI which matches that provisioning method.

   While EAP peers allow users to enter user identifiers directly for
   existing EAP methods, they SHOULD NOT check whether those identfiers
   match any EPI.  Any user who enters an identifier which matches an
   EPI will either get rejected because the server does not support

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   provisioning, or the user will be placed into a captive portal.
   There is no security or privacy issues with a user manually entering
   an EPI as the user identifier.

   When all goes well, running EAP with the EPI results in new
   authentication credentials being provisioned.  The peer then drops
   its network connection, and re-authenticates using the newly
   provisioned credentials.  The user MAY be involved in this process,
   but in general provisioning results in the EAP peer automatically
   gaining network access using the provisioned credentials.

   There are a number of ways in which provisioning can fail.  One way
   is when the server does not implement the provisioning method.  EAP
   peers therefore MUST track which provisioning methods have been
   tried, and not repeat the same method to the same EAP server when
   receiving an EAP Nak.  EAP peers MUST rate limit attempts at
   provisioning, in order to avoid overloading the server.  This rate
   limiting SHOULD include jitter and exponential backoff.

   Since there is no way to signal whether the failed provisioning is
   due to a transient failure on the EAP server, or whether it is due to
   the EAP server not supporting that provisioning method, EAP peers
   SHOULD err on the side of long delays between retrying the same
   provisioning method to an EAP server.  EAP peers MAY retry a given
   provisioning method after a sufficiently long interval that the EAP
   server might have implemented the provisioning method, e.g., at least
   a day, and perhaps no more than a month.

   Another way for the provisioning method to fail is when the new
   credentials do not result in network access.  It is RECOMMENDED that
   when peers are provisioned with credentials, that they immediately
   try to gain network access using those credentials.  That process
   allows errors to be quickly discovered and addressed.

   An EAP peer may have been provisioned with temporary credentials or
   credentials that expire after some period of time (e.g., an X.509
   certificate with notAfter date set).  It SHOULD therefore attempt to
   provision new credentials before the current set expires.
   Unfortunately, any re-provisioning process with EAP will involve the
   device dropping off from the "full" network, in order to connect to
   the provisioning network.  It is therefore RECOMMENDED that re-
   provisioning methods be provided which can be used when the device
   has full network access.  See Section 3.6 for additional discussion
   on this topic.

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3.4.2.  EAP Servers

   An EAP session begins with the server receiving an initial EAP-
   Request/Identity message.  An EAP server supporting this
   specification MUST examine the identity to see if it uses a realm
   located under eap.arpa.  If so, the identity is an EPI.  Processing
   of all other identities is unchanged by this specification.

   If the server receives a malformed EPI, it MUST reply with an EAP
   Failure, as per [RFC3748], Section 4.2.  Otherwise, the EPI is
   examined to determine which provisioning method is being requested by
   the peer.

   If the server does not recognize the EPI requested by the peer, it
   MUST reply with an EAP Nak of type zero (0).  This reply indicates
   that the requested provisioning method is not available.  The server
   also MUST reply with a Nak of type zero (0) as per [RFC3748],
   Section 5.3.1, if the peer proposes an EAP method which is not
   supported by the server, or is not recognized as being valid for that
   provisioning method.  The peer can then take any remedial action
   which it determines to be appropriate.

   Once the server accepts the provisioning method, it then replies with
   an EAP method which MUST match the one associated with the EPI.  The
   EAP process then proceeds as per the EAP state machine outlined in
   [RFC3748].

   Implementations MUST treat peers using an EPI as untrusted, and
   untrustworthy.  Once such a peer is authenticated, it MUST be placed
   into a limited network, such as a captive portal.  The limited
   network MUST NOT permit general network access.  Implementations
   should be aware of methods which bypass simple blocking, such as
   tunneling data over DNS.

   A secure provisioning network is one where only the expected traffic
   is allowed, and all other traffic is blocked.  The alternative of
   blocking only selected "bad" traffic results in substantial security
   failures.  As most provisioning methods permit unauthenticated
   devices to gain network access, these methods have a substantial
   potential for abuse by malicious actors.  As a result, the limited
   network needs to be designed assuming that it will be abused by
   malicious actoer.

   A limited network SHOULD also limit the duration of network access by
   devices being provisioned.  The provisioning process should be fairly
   quick, and in the order of seconds to tens of seconds in duration.
   Provisioning times longer than this likely indicate an issue, and it
   may be useful to block the problematic device from the network.

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   A limited network SHOULD also limit the amount of data being
   transferred by devices being provisioned, and SHOULD limit the
   network services which are available to those devices.  The
   provisioning process generally does not need to download large
   amounts of data, and similarly does not need access to a large number
   of services.

   Servers SHOULD rate-limit provisioning attempts.  A misbehaving peer
   can be blocked temporarily, or even permanently.  Implementations
   SHOULD limit the total number of peers being provisioned at the same
   time.  We note that there is no requirement to allow all peers to
   connect without limit.  Instead, peers are provisioned at the
   discretion of the network being accessed, which may permit or deny
   those devices based on reasons which are not explained to those
   devices.

   Peers MUST rate-limit their provisioning attempts.  If provisioning
   fails, it is likely because provisioning is not available.  Retrying
   provisioning repeatedly in quick succession is not likely to change
   the server behavior.  Instead, it is likely to result in the peer
   being blocked.  The peer SHOULD retry provisioning no more than once
   every few minutes, and SHOULD perform exponential back-off on its
   provisioning attempts.

   Implementations SHOULD use functionality such as the RADIUS Filter-Id
   attribute ([RFC2865], Section 5.11) to set packet filters for the
   peer being provisioned.  For ease of administration, the Filter-Id
   name could simply be the EPI, or a similar name.  Such consistency
   aids with operational considerations when managing complex networks.

3.5.  Other Considerations

   Implementations MUST NOT permit EAP method negotiation with
   provisioning credentials.  That is, when an EPI is used, any EAP Nak
   sent by a server MUST contain only EAP method zero (0).  When an EAP
   peer uses an EPI and receives an EAP Nak, any EAP methods given in
   that Nak MUST be ignored.

   While a server may support multiple provisioning methods, there is no
   way in EAP to negotiate which provisioning method can be used.  It is
   also expected that the provisioning methods will be specific to a
   particular type of peer device.  That is, a given peer is likely to
   support only one provisioning method.

   As a result, there is no need to require a method for negotiating
   provisioning methods.

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3.6.  Considerations for Provisioning Specifications

   The operational considerations discussed above have a number of
   impacts on specifications which define provisioning methods.

3.6.1.  Negotiation

   Specifications which define provisioning for an EAP method SHOULD
   provide a method-specific process by which implementations can
   negotiate a mutually acceptable provisioning method.

   For the reasons noted above, however, we cannot make this suggestion
   mandatory.  If it is not possible for a provisioning method to define
   any negotiation, then that limitation should not be a barrier to
   publishing the specification.

3.6.2.  Renewal of Credentials

   Where a provisioning method is expected to create credentials which
   do not expire, the specification SHOULD state this explicitly.

   Where credentials expire, it is RECOMMENDED that specifications
   provide guidance on how the credentials are to be updated.  For
   example, an EAP method could permit re-provisioning to be done as
   part of a normal EAP authentication, using the currently provisioned
   credentials.

   It is RECOMMENDED that the provisioning methods provide for a method
   which can be used without affecting network access.  A specification
   could define provisioning endpoints such as Enrollment over Secure
   Transport (EST) [RFC7030], or Internet X.509 Public Key
   Infrastructure Certificate Management Protocol (CMP) [RFC4210].  The
   provisioning endpoints could be available both on the provisioning
   network, and on the provisioned (i.e., normal) network.  Such an
   architecture means that devices can be re-provisioned without losing
   network access.

3.7.  Notes on AAA Routability

   When we say that the eap.arpa domain is not routable in an AAA proxy
   framework, we mean that the domain does not exist, and will never
   resolve to anything for dynamic discovery as defined in [RFC7585].
   In addition, administrators will not have statically configured AAA
   proxy routes for this domain.  Where routes are added for this
   domain, they will generally be used to implement this specification.

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   In order to avoid spurious DNS lookups, RADIUS servers supporting
   [RFC7585] SHOULD perform filtering in the domains which are sent to
   DNS.  Specifically, names in the "eap.arpa" domain SHOULD NOT be
   looked up in DNS.

4.  Background and Rationale

   In this section, we provide background on the existing functionality,
   and describe why it was necessary to define provisioning methods for
   EAP.

4.1.  Review of Existing Functionality

   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 appropriate 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.

   Wi-Fi Alliance has defined an unauthenticated EAP-TLS method, using a
   vendor-specific EAP method as part of HotSpot 2.0r2 [HOTSPOT].
   However, there appears to be few deployments of this specification.

   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.

   Tunnel Extensible Authentication Protocol (TEAP) [RFC7170] provides
   for provisioning via an unauthenticated TLS tunnel.  That document
   provides for a server unauthenticated provisioning mode, but the
   inner TLS exchange requires that both ends authenticate each other.
   There are ways to provision a certificate, but the peer must still
   authenticate itself to the server with pre-existing credentials.  As
   a result, any provisioning method which uses TEAP will have to
   address this limitation.

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4.2.  Taxonomy of Provisioning Types

   There are two scenarios where provisioning can be done.  The first is
   where provisioning is done within the EAP method, 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 IP based provisioning over more complex
   protocols.

4.2.1.  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 EAP Methods

   As the provisioning identifier is used within EAP, it necessarily has
   interactions with, and effects on, the various EAP methods.  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 password-based methods are used, the
   password SHOULD be the same as the provisioning identifier, as there
   are few reasons to define a method-specific password.

   This requirement also applies to TLS-based EAP methods such as EAP
   Tunneled Transport Layer Security (EAP-TTLS) and Protected Extensible
   Authentication Protocol (PEAP).  Where the TLS-based EAP method
   provides for an inner identity and inner authentication method, the
   credentials used there SHOULD be the provisioning identifier for both
   the inner identity, and any inner password.

   It is RECOMMENDED that provisioning be done via a TLS-based EAP
   methods.  TLS provides for authentication of the EAP server, along
   with integrity and confidentiality protection for 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 certificate authorities (CAs) locally configured.

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5.1.  High Level Requirements

   All provisioning methods which are specified within the eap.arpa
   domain MUST define a way to authenticate the server.  This
   authentication can happen either at the EAP layer (as with TLS-based
   EAP methods), or after network access has been granted (if
   credentials are provisioned over HTTPS).

   Where TLS-based EAP methods are used, implementations MUST still
   validate EAP server certificates in all situations other than
   provisioning.  Where the provisioning method under the "eap.arpa"
   domain defines that provisioning happen via another protocol such as
   with HTTPS, the EAP peer MAY skip validating the EAP server
   certificate.

   Whether or not the server certificate is ignored, the peer MUST treat
   the local network as untrusted.  [RFC8952], Section 6.2 has more
   discussion on this topic.

   The ability to not validate the EAP server certificates relaxes the
   requirements of [RFC5216], Section 5.3 which requires that the server
   certificate is always validated. .  For the provisioning case, it is
   acceptable in some cases to not validate the EAP server certificate,
   but only so long as there are other means to authenticate the data
   which is being provisioned.

   However, since the device likely is configured with web CAs
   (otherwise, the captive portal would also be unauthenticated),
   provisioning methods could use those CAs within an EAP method in
   order to allow the peer to authenticate the EAP server.  Further
   discussion of this topic is better suited for the specification(s)
   which define a particular provisioning method.  We do not discuss it
   here further, other than to say that it is technically possible.

5.2.  EAP-TLS

   This document defines an identifier "portal@tls.eap.arpa", which
   allows EAP peers to use unauthenticated 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].  Note that peer unauthenticated access MUST provide for
   authentication of the EAP server, such as with a server certificate.
   Using TLS-PSK with a well-known PSK value is generally not
   appropriate, as it would not provide server authentication.

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   An EAP server which agrees to authenticate this request MUST ensure
   that the device is placed into a captive portal with limited network
   access.  Implementations SHOULD limit both the total amount of data
   transferred by devices in the captive portal, and SHOULD also limit
   the total amount of time a device spends within the captive portal.

   This method is an improvement over existing captive portals, which
   are typically completely unsecured and unauthenticated.  Using peer
   unauthenticated TLS for network access ensures that the EAP server is
   proven to be authentic.  The use of 802.1X ensures that the link
   between the EAP peer and EAP authenticator (e.g. access point) is
   also secured.

   Further details of the captive portal architecture can be found in
   [RFC8952].  The captive portal can advertise support for the
   "eap.arpa" domain via an 802.11u NAI realm.

5.3.  EAP-NOOB

   It is RECOMMENDED that server implementations of Nimble out-of-band
   authentication for EAP (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".

6.  IANA Considerations

   A number IANA actions are required.  There are two registry updates
   in order to define "eap.arpa".  A new registry is created.  The
   "noob@eap-noob.arpa" registry entry is deprecated.

6.1.  .arpa updates

   There are two updates to the ".arpa" registry.

   IANA is also instructed to refuse further allocation requests which
   are directly within the ".arpa" registry for any functionality
   related to the EAP protocol.  Instead, new allocations related to EAP
   are to be made within the new "EAP Provisioning Identifiers"
   registry.

6.1.1.  Deprecating eap-noob.arpa

   IANA is instructed to update the "eap-noob.arpa" entry as follows.

   The USAGE field is updated to add the word DEPRECATED.

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   The REFERENCE field is updated to add a reference to THIS-DOCUMENT.

6.1.2.  Defining eap.arpa

   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

6.1.2.1.  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 recognize these names as special or use
       them differently from other domain names.  The use of these names
       in EAP is invisible to end users.

   2.  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 behavior.
       EAP peers should recognize these names as special, and should

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       refuse to allow users to enter them in any interface.
       EAP servers and RADIUS servers should recognize the "eap.arpa"
       domain as special, and refuse to do dynamic discovery ([RFC7585])
       for it.

   3.  Name Resolution APIs and Libraries:
       Writers of these APIs and libraries are not expected to recognize
       these names or treat them differently.

   4.  Caching DNS Servers:
       Writers of caching DNS servers are not expected to recognize
       these names or treat them differently.

   5.  Authoritative DNS Servers:
       Writers of authoritative DNS servers are not expected to
       recognize these names or treat them differently.

   6.  DNS Server Operators:
       These domain names have minimal impact on DNS server operators.
       They should never be used in DNS, or in any networking protocol
       outside of EAP.
       Some DNS servers may receive lookups for this domain, if EAP or
       RADIUS servers are configured to do dynamic discovery for realms
       as defined in [RFC7585], and where those servers are not updated
       to ignore the ".arpa" domain.  When queried for the "eap.arpa"
       domain, DNS servers SHOULD return an NXDOMAIN error.
       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.

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

6.2.  EAP Provisioning Identifiers 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.  Guidelines for experts is
   provided in Section 6.3.

   The contents of the registry are as follows.

   Title

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      EAP Provisioning Identifiers

   Registration Procedure(s)

      Expert review

   Reference

      THIS-DOCUMENT

   Registry

      NAI

         The Network Access Identifier in [RFC7542] format.  Names are
         stored as DNS A-Labels [RFC5890], Section 2.3.2.1, and are
         compared via the domain name comparison rules defined in
         [STD13].

      Method Type

         The EAP method name, taken from the "Description" field of the
         EAP "Method Types" registry.

      Reference

         Reference where this identifier was defined.

6.2.1.  Initial Values

   The following table gives the initial values for this table.

    +=====================+=============+=============================+
    | NAI                 | Method-Type | Reference                   |
    +=====================+=============+=============================+
    | @noob.eap.arpa      | EAP-NOOB    | [RFC9140] and THIS-DOCUMENT |
    +---------------------+-------------+-----------------------------+
    | portal@tls.eap.arpa | EAP-TLS     | [RFC9190] and THIS-DOCUMENT |
    +---------------------+-------------+-----------------------------+

                                  Table 1

6.3.  Guidelines for Designated Experts

   The following text gives guidelines for Designated Experts who review
   allocation requests for this registry.

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6.3.1.  NAIs

   The intent is for the NAI to contain both a reference to the EAP
   Method Type, and a description of the purpose of the NAI.  For
   example, with an EAP Method Type "name", and a purpose "action", the
   NAI SHOULD be of the form "action@foo.eap.arpa".

   The NAI MUST satisfy the requirements of the [RFC7542], Section 2.2
   format.  The utf8-username portion MAY be empty.  The utf8-username
   portion MUST NOT be "anonymous".  The NAI MUST end with "eap.arpa".
   NAIs with any "v." subdomain MUST NOT be registered, in order to
   preserve the functionality of that subdomain.

   NAIs in the registry SHOULD NOT contain more than one subdomain.
   NAIs with a leading "v." subdomain MUST NOT be registered.  That
   subdomain is reserved for vendor and SDO extensions.

   The subdomain of the NAI field should correspond to the EAP Method
   Type name.  Care should be taken so that the domain name conventions
   specified in RFC1034 are followed.

   The NAIs in this registry are case-insensitive.  While [RFC7542]
   notes that similar identifiers of different case can be considered to
   be different, for simplicity this registry requires that all entries
   MUST be lowercase.

   Identifiers MUST 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.

   Entries in the registry should be short.  NAIs defined here 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 in this registry needs 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].

6.4.  Method Type

   Values in "Method Type" field of this registry MUST be taken from the
   IANA EAP Method Types registry or else it MUST be an Expanded Type
   which usually indicates a vendor specific EAP method.

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   The EAP Method Type MUST provide an MSK and EMSK as defined in
   [RFC3748].  Failure to provide these keys means that the method will
   not be usable within an authentication framework which requires those
   methods, such as with IEEE 802.1X.

6.5.  Designated Experts

   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 Method Update (EMU) 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.

6.6.  Organization Self Assignment

   This registry allows organizations to request allocations from this
   registry, but explicit allocations are not always required.  Any NAI
   defined in this registry also implicitly defines a subdomain "v.".
   Organizations can self-allocate in this space, under the "v."
   subdomain, e.g. "local@example.com.v.tls.eap.arpa".

   The purpose of self-assigned realms is for testing, and for future
   expansion.  There are currently no use-cases being envisioned for
   these realms, but we do not wish to forbid future expansion.

   An organization which has registered a Fully Qualified Domain Name
   (FQDN) within the DNS can use that name within the "v." subdomain.

   As DNS registrations can change over time, an organization may stop
   using a domain at some point.  This change is reflected in the DNS,
   but is unlikely to be reflected in shipped products which use a self-
   assigned realm.  There is no solution to this problem, other than
   suggesting that organizations using self-assigned realms do not allow
   their DNS registrations to expire.

   It is therefore RECOMMENDED that organizations avoid the use of self-
   assigned realms.  Organizations MAY use self-assigned realms only
   when no other alternative exists, and when the organization expects
   to maintain operation for at least the lifetime of the devices which
   use these realms.

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7.  Privacy Considerations

   The EAP Identity field is generally publicly visible to parties who
   can observe the EAP traffic.  As the names given here are in a public
   specification, there is no privacy implication to exposing those
   names within EAP.  The entire goal of this specification is in fact
   to make those names public, so that unknown (and private) parties can
   publicly (and anonymously) declare what kind of network access they
   desire.

   However, there are many additional privacy concerns around this
   specification.  Most EAP traffic is sent over RADIUS [RFC2865].  The
   RADIUS Access-Request packets typically contain large amounts of
   information such as MAC addresses, device location, etc.

   This specification does not change RADIUS or EAP, and as such does
   not change which information is publicly available, or is kept
   private.  Those issues are dealt with in other specifications, such
   as [I-D.ietf-radext-deprecating-radius].

   However, this specification can increase privacy by allowing devices
   to anonymously obtain network access, and then securely obtain
   credentials.

   The NAIs used here are contained in a public registry, and therefore
   do not have to follow the username privacy recommendations of
   [RFC7542], Section 2.4.  However, there may be other personally
   identifying information contained in EAP or AAA packets.  This
   situation is no different from normal EAP authentication, and thus
   has no additional positive or negative implications for privacy.

8.  Security Considerations

   This specification defines a framework which permits unknown,
   anonymous, and unauthenticated devices to request and to obtain
   network access.  As such, it is critical that network operators
   provide limited access to those devices.

   Future specifications which define an NAI within this registry,
   should give detailed descriptions of what kind of network access is
   to be provided.

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8.1.  On-Path Attackers and Impersonation

   In most EAP use-cases, the server identity is validated (usually
   through a certificate), or the EAP method allows the TLS tunnel to be
   cryptographically bound to the inner application data.  For the
   methods outlined here, the use of public credentials, and/or skipping
   server validation allows "on-path" attacks to succeed where they
   would normally fail

   EAP peers and servers MUST assume that all data sent over an EAP
   session is visible to attackers, and can be modified by them.

   The methods defined here MUST only be used to bootstrap initial
   network access.  Once a device has been provisioned, it gains network
   access via the provisioned credentials, and any network access
   policies can be applied.

8.2.  Provisioning is Unauthenticated

   We note that this specification allows for unauthenticated EAP peers
   to obtain network access, however limited.  As with any
   unauthenticated process, it can be abused.  Implementations should
   take care to limit the use of the provisioning network.

   Section 3.4.2 describes a number of methods which can be used to
   secure the provisioning network.  In summary:

   *  allow only traffic which is needed for the current provisioning
      method.  All other traffic should be blocked.  Most notable, DNS
      has been used to exfiltrate network traffic, so DNS recursive
      resolvers SHOULD NOT be made available on the provisioning
      network.

   *  limit the services available on the provisioning network to only
      those services which are needed for provisioning.

   *  limit the number of devices which can access the provisioning
      network at the same time.

   *  for any one device, rate limit its access the provisioning
      network.

   *  for a device which has accessed the provisioning network, limit
      the total amount of time which it is allowed to remain on the
      network

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   *  for a device which has accessed the provisioning network, limit
      the total amount of data which it is allowed to transfer through
      the network.

9.  Acknowledgements

   Mohit Sethi provided valuable insight that using subdomains was
   better and more informative than the original method, which used only
   the utf8-username portion of the NAI.

   The document was further improved with reviews from Ignes Robles and
   Ben Kaduk.

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <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, June 2004,
              <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,
              March 2008, <https://www.rfc-editor.org/rfc/rfc5216>.

   [RFC7542]  DeKok, A., "The Network Access Identifier", RFC 7542,
              DOI 10.17487/RFC7542, May 2015,
              <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, June 2017,
              <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,
              May 2017, <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, December 2021,
              <https://www.rfc-editor.org/rfc/rfc9140>.

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   [STD13]    Internet Standard 13,
              <https://www.rfc-editor.org/info/std13>.
              At the time of writing, this STD comprises the following:

              Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <https://www.rfc-editor.org/info/rfc1034>.

              Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <https://www.rfc-editor.org/info/rfc1035>.

10.2.  Informative References

   [HOTSPOT]  Alliance, W.-F., "Passpoint", n.d.,
              <https://www.wi-fi.org/discover-wi-fi/passpoint>.

   [I-D.ietf-radext-deprecating-radius]
              DeKok, A., "Deprecating Insecure Practices in RADIUS",
              Work in Progress, Internet-Draft, draft-ietf-radext-
              deprecating-radius-06, 25 May 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-radext-
              deprecating-radius-06>.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, DOI 10.17487/RFC2865, June 2000,
              <https://www.rfc-editor.org/rfc/rfc2865>.

   [RFC4210]  Adams, C., Farrell, S., Kause, T., and T. Mononen,
              "Internet X.509 Public Key Infrastructure Certificate
              Management Protocol (CMP)", RFC 4210,
              DOI 10.17487/RFC4210, September 2005,
              <https://www.rfc-editor.org/rfc/rfc4210>.

   [RFC5890]  Klensin, J., "Internationalized Domain Names for
              Applications (IDNA): Definitions and Document Framework",
              RFC 5890, DOI 10.17487/RFC5890, August 2010,
              <https://www.rfc-editor.org/rfc/rfc5890>.

   [RFC5931]  Harkins, D. and G. Zorn, "Extensible Authentication
              Protocol (EAP) Authentication Using Only a Password",
              RFC 5931, DOI 10.17487/RFC5931, August 2010,
              <https://www.rfc-editor.org/rfc/rfc5931>.

   [RFC6761]  Cheshire, S. and M. Krochmal, "Special-Use Domain Names",
              RFC 6761, DOI 10.17487/RFC6761, February 2013,
              <https://www.rfc-editor.org/rfc/rfc6761>.

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   [RFC7030]  Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
              "Enrollment over Secure Transport", RFC 7030,
              DOI 10.17487/RFC7030, October 2013,
              <https://www.rfc-editor.org/rfc/rfc7030>.

   [RFC7170]  Zhou, H., Cam-Winget, N., Salowey, J., and S. Hanna,
              "Tunnel Extensible Authentication Protocol (TEAP) Version
              1", RFC 7170, DOI 10.17487/RFC7170, May 2014,
              <https://www.rfc-editor.org/rfc/rfc7170>.

   [RFC7585]  Winter, S. and M. McCauley, "Dynamic Peer Discovery for
              RADIUS/TLS and RADIUS/DTLS Based on the Network Access
              Identifier (NAI)", RFC 7585, DOI 10.17487/RFC7585, October
              2015, <https://www.rfc-editor.org/rfc/rfc7585>.

   [RFC8952]  Larose, K., Dolson, D., and H. Liu, "Captive Portal
              Architecture", RFC 8952, DOI 10.17487/RFC8952, November
              2020, <https://www.rfc-editor.org/rfc/rfc8952>.

   [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, February 2022,
              <https://www.rfc-editor.org/rfc/rfc9190>.

Author's Address

   Alan DeKok
   InkBridge Networks
   Email: aland@inkbridgenetworks.com

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