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draft-pala-tian-eap-creds-00.xml
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draft-pala-tian-eap-creds-00.xml
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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE rfc SYSTEM 'rfc2629.dtd' [
<!-- Normative References -->
<!ENTITY rfc2119 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml'>
<!-- <!ENTITY rfc3986 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3986.xml'> -->
<!-- <!ENTITY rfc4501 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4501.xml'> -->
<!ENTITY rfc3279 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3279.xml'>
<!ENTITY rfc3748 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.3748.xml'>
<!ENTITY rfc4055 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4055.xml'>
<!ENTITY rfc4210 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4210.xml'>
<!ENTITY rfc4491 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4491.xml'>
<!-- <!ENTITY rfc5019 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5019.xml'> -->
<!-- <!ENTITY rfc5234 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5234.xml'> -->
<!ENTITY rfc5272 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5272.xml'>
<!ENTITY rfc5280 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5280.xml'>
<!-- <!ENTITY rfc5280 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5280.xml'> -->
<!ENTITY rfc6402 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.6402.xml'>
<!ENTITY rfc7030 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.7030.xml'>
<!-- <!ENTITY rfc7170 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.7170.xml'> -->
<!ENTITY rfc8126 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.8126.xml'>
<!ENTITY rfc8520 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.8520.xml'>
<!ENTITY rfc8555 PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.8555.xml'>
<!-- Informative References -->
<!-- <!ENTITY ietf-acme-acme PUBLIC '' 'http://xml.resource.org/public/rfc/bibxml/reference.I-D.ietf-acme-acme.xml'> -->
]>
<rfc category="std" docName="draft-pala-tian-eap-creds-01" ipr="trust200902">
<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
<?rfc toc="yes" ?>
<?rfc tocdepth="5"?>
<?rfc symrefs="yes" ?>
<?rfc sortrefs="yes"?>
<?rfc iprnotified="no" ?>
<?rfc strict="yes" ?>
<?rfc compact="yes" ?>
<?rfc subcompact="no" ?>
<front>
<title abbrev="EAP-CREDS">Credentials Provisioning and Management via EAP (EAP-CREDS)</title>
<author initials="M.P." surname="Pala" fullname="Massimiliano Pala">
<organization>CableLabs</organization>
<address>
<postal>
<street>858 Coal Creek Cir</street>
<city>Louisville</city>
<region>CO</region>
<code>80027</code>
<country>US</country>
</postal>
<email>m.pala@openca.org</email>
<uri>http://www.linkedin.com/in/mpala</uri>
</address>
</author>
<author initials="Y.T." surname="Tian" fullname="Yuan Tian">
<organization>CableLabs</organization>
<address>
<postal>
<street>858 Coal Creek Cir</street>
<city>Louisville</city>
<region>CO</region>
<code>80027</code>
<country>US</country>
</postal>
<email>y.tian@cablelabs.com</email>
<uri>http://www.linkedin.com/in/ytian21</uri>
</address>
</author>
<date year="2022" month="June"/>
<area>Security</area>
<workgroup></workgroup>
<keyword>PKI</keyword>
<keyword>EAP</keyword>
<keyword>Provisioning</keyword>
<abstract>
<t>
With the increase number of devices, protocols, and applications that rely on strong credentials
(e.g., digital certificates, keys, or tokens) for network access, the need for
a standardized credentials provisioning and management framework is paramount.
The 802.1x architecture allows for entities (e.g., devices, applications, etc.) to authenticate to
the network by providing a communication channel where different methods can be used to
exchange different types of credentials.
However, the need for managing these credentials (i.e., provisioning and renewal) is still a
hard problem to solve. Usually, credentails used in an access network can be in different levels
(e.g., network-level, user-level) and sometimes tend to live unmanaged for quite a long time due
to the challenges of operation and implementation.
EAP-CREDS (RFC XXXX<!--<xref target="RFC2119"/>-->), if implemented in Managed Networks (e.g., Cable Modems), could
enable our operators to offer a registration and credentials management service
integrated in the home WiFi thus enabling visibility about registered devices.
During initialization, EAP-CREDS also allows for MUD files or URLs to
be transferred between the EAP Peer and the EAP Server, thus giving
detailed visibility about devices when they are provisioned with credentials
for accessing the networks. The possibility provided by EAP-CREDS can help to
secure home or business networks by leveraging the synergies of the security
teams from the network operators thanks to the extended knowledge of what
and how is registered/authenticated.
This specifications define how to support the provisioning and management of authentication
credentials that can be exploited in different environments (e.g., Wired, WiFi, cellular, etc.)
to users and/or devices by using EAP together with standard provisioning protocols.
</t>
</abstract>
</front>
<middle>
<section title="Requirements notation">
<t>
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 <xref target="RFC2119"/>.
</t>
</section>
<section anchor="intro" title="Introduction">
<t>
Many environments are, today, moving towards requiring strong authentication when
it comes to gain access to networks. The 802.1x architecture provides network
administrators with the possibility to check credentials presented by a device
even before providing any connectivity or IP services to it.
However, the provisioning and management of these credentials is a hard problem
to solve and many vendors opt for long-lived credentials that can not be easily
revoked, replaced, or simply renewed.
This specification addresses the problem of providing a simple-to-use and
simple-to-deploy conduit for credentials management by extending the EAP
protocol to support credentials provisioning and management functionality.
In particular, the EAP-CREDS method defined here provides a generic framework
that can carry the messages for provisioning different types of credentials.
EAP-CREDS cannot be used as a stand-alone method, it is required that EAP-CREDS is used
as an inner method of EAP-TLS, EAP-TEAP, or any other tunneling method that can provide
the required secrecy and (at minimum) server-side authentication to make sure
that the communication is protected and with the right server.
</t>
<section anchor="existing_solutions" title="Overview of existing solutions">
<t>
Currently there are many protocols that address credentials lifecycle management. In particular,
when it comes to digital certificates, some of the most deployed management protocols are:
Certificate Management Protocol (CMP) <xref target="RFC4210" />, Certificate Management over CMS (CMC)
<xref target="RFC5272"/><xref target="RFC6402"/>, Enrollment over Secure Transport (EST)
<xref target="RFC7030"/>, and Automated Certificate Management Environment (ACME)
<xref target="RFC8555"/>.
However, none of these protocols provide native support for client that do not have IP connectivity
yet (e.g., because they do not have network-access credentials, yet). EAP-CREDS
provides the possibility to use such protocols (i.e., message-based) by defining a series of
messages that can be used to encapsulate the provisioning messages for the selected
provisioning protocol.
</t>
</section>
<section anchor="scope" title="Scope Statement">
<t>
This document focuses on the definition of the EAP-CREDS method to convey
credentials provisioning and managing messages between the client and the
AAA server. Moreover, the document defines how to encode messages for the
main IETF provisioning protocols.
This document, however, does not provide specifications for how and where
the credentials are generated. In particular, the credentials could be
generated directly within the AAA server or at a different location (i.e., the
Certificate Service Provider or CSP) site. Different authentication
mechanisms (e.g., TLS, etc.) can be used to secure the communication
between the server's endpoint and the CSP.
Examples and details of how to use EAP-CREDS encapsulation mechanism with specific protocol are out of scope
of this document. For more details of using EAP-CREDS method with Simple Provisioning Protocol (SPP),
please refer to EAP-CREDS with Simple Provisioning Protocol (SPP) <!--<xref target="RFCXXXX"/>-->.
For more details of using EAP-CREDS method with Certificate Management Protocol (CMP),
please refer to EAP-CREDS withwith Certificate Management Protocol (CMP) <!--<xref target="RFCXXXX"/>-->.
These two documents can be used as the template for other protocols' encapulation with EAP-CREDS.
</t>
</section>
<section anchor="tunnel" title="EAP-CREDS as tunneled mechanism only">
<t>
EAP-CREDS requires that an outer mechanism is in place between the Peer and
the Server in order to provide authentication and confidentiality of the
messages exchanged via EAP-CREDS. In other words, EAP-CREDS assumes that an
appropriately encrypted and authenticated channel has been established to
prevent the possibility to leak information or to allow man-in-the-middle attacks.
</t>
<t>
This choice was taken to simplify the message flow between Peer and Server, and
to abstract EAP-CREDS from the secure-channel establishment mechanism. EAP-TLS,
or EAP-TEAP are examples of such mechanisms.
</t>
</section>
<section anchor="frag" title="Fragmentation Support">
<t>
EAP does not directly support handling fragmented packets and it requires
the outer method to provide fragmentation support.
</t>
<t>
Because of the outer method requirements in particular, removing any
support for fragmented messages in EAP-CREDS removes the duplication
of packets (e.g., Acknowledgment Packets) sent across the Peer and
the Server, thus resulting in a smaller number of exchanged messages.
</t>
</section>
<section anchor="teap_creds" title="Encapsulating Provisioning Protocols in EAP-CREDS">
<t>
In order to use EAP-CREDS together with your favorite provisioning protocol, the messages
from the provisioning protocol need to be sent to the other party. In EAP-CREDS, this is
done by encoding the provisioning protocol messages inside the ('ProtoData') TLV.
In case the provisioning protocol uses additional data for its operations (e.g., uses
HTTP Headers), this data can be encoded in a separate ('ProtoHeaders') TLV.
</t>
<t>
Since the implementation of the provisioning endpoint could happen in a (logically or
physically) different component, a method is needed to identify when a provisioning
protocol has actually ended. In EAP-CREDS, the 'D' (Done) bit in the message headers
is used for this purpose.
</t>
<t>
In the first message of Phase Two, the Server provides the client with all the selected
parameters for one specific credential that needs attention (or for a new credential)
to be managed by the network. In particular, the server provides, at minimum, the
('Protocol') TLV, the ('Action') TLV, and the ('Params') or the
('Creds-Info') TLV.
</t>
<t>
After checking the parameters sent by the Server, if the Peer does not support any of
the proposed ones, it MUST send a message with one single ('Error') TLV with the appropriate error
code(s). The server, can then decide if to manage a different set of credentials (if
more where reported by the Peer in its Phase One message) or if to terminate the EAP
session with an error.
</t>
<t>
The Peer and the Server exchange Provisioning messages until an error is detected (and the
appropriate error message is sent to the other party) or until Phase Two is successfully
completed.
</t>
</section>
<section anchor="eap_creds_hashing" title="Algorithm Requirements">
<t>
EAP-CREDS uses the SHA-256 hashing algorithm to verify credentials in phase three
of the protocol. Peers and Servers MUST support SHA-256 for this purpose.
</t>
</section>
<section anchor="notation" title="Notation" >
<t>
In this document we use the following notation in the diagrams to
provide information about the cardinality of the data structures (TLVs)
within EAP-CREDS messages:
</t>
<texttable anchor="eap_creds_notation" title="EAP-CREDS Notation">
<ttcol align="center">Symbol</ttcol>
<ttcol align="center">Example</ttcol>
<ttcol align="left">Usage</ttcol>
<c>{ }</c>
<c>{TLV1}</c>
<c>Curly Brackets are used to indicate a set</c>
<c>[ ]</c>
<c>{[TLV2]}</c>
<c>Square Brackets are used to indicate that a field is optional</c>
<c>( )</c>
<c>{TLV1(=V)}</c>
<c>Round Squares are used to specify a value</c>
<c> + </c>
<c>{TLV_2+}</c>
<c>The Plus character indicates that one or more instances are allowed</c>
</texttable>
</section>
</section>
<!-- -->
<!-- End of Introduction -->
<!-- -->
<section title="EAP-CREDS Protocol">
<t>
In a nutshell, EAP-CREDS provides the abstraction layer on top of which credentials
provisioning/managing protocols can be deployed thus enabling their use even before
provisioning IP services.
</t>
<t>
This section outlines the operation of the protocol and message flows.
The format of the CREDS messages is given in <xref target="creds_msg" />.
</t>
<section title="Message Flow">
<t>
EAP-CREDS message flow is logically subdivided into three different
phases: Initialization, Provisioning, and Validation. EAP-CREDS
enforces the order of phases, i.e. it is not possible to move to an
earlier phase.
</t>
<t>
Phase transitioning is controlled by the Server. In particular, the
server, after the last message of a phase, it can decide to either
(a) start the next phase by sending the first message of the next
phase, or (b) continue the same phase by sending another "first"
message of the phase (e.g., managing a second set of credentials) -
this is allowed only in Phase Two and Phase Three but NOT in Phase One,
or (c) terminate the EAP session.
</t>
<t>
<list style="hanging">
<t hangText="Phase One (Required).">
Initialization. During this phase the Peer and the Server
exchange the information needed to select the appropriate
credentials management protocol.
Phase One flow is composed by only messages.
In particular, the Sever sends
its initial message of type ('EAP-CREDS-Init'). The Peer replies with
the details about which provisioning protocols are supported, and additional
information such as the list of installed credentials and, optionally,
authorization data (for new credentials registration).
</t>
<t hangText="Phase Two (Optional).">
Provisioning Protocol Flow. In this phase, the Peer and the Server
exchange the provisioning protocol's messages encapsulated in a
EAP-CREDS message of type Provisioning. The messages use two main TLVs.
The first one is the ('ProtoHeaders') TLV which is optional
and carries information that might be normally conveyed via the transport
protocol (e.g., HTTP headers). The second one is the ('ProtoData'),
which is required and carries the provisioning protocol's
messages. The server can decide to repeat
phase two again to register new credentials or to renew a separate
set of credentials by issuing a new ('Provisioning') message for the
new target. When no more credentials have to be managed,
the Server can start phase three or simply terminate the EAP session.
</t>
<t hangText="Phase Three (Optional).">
Credentials Validation. This optional phase can be initiated by
the server and it is used to validate that the Peer has properly
installed the credentials and can use them to authenticate
itself. Depending on the credentials' type, the messages can
carry a challenge/nonce, the value of the secret/token, or other
information. The format of the credentials is supposed to be
known by the provider and the device.
</t>
</list>
</t>
</section>
<section anchor="phase_transitioning" title="Phase Transitioning Rules">
<t>
In order to keep track of starting and ending a phase, EAP-CREDS defines
several bits and fields in the EAP-CREDS message headers. In particular,
as described in <xref target="creds_header" />, the 'S' (Start) bit is
used to indicate the beginning (or Start) of a phase, while the 'Phase'
field (4 bits) is used to indicate the phase for this message.
</t>
<t>
In EAP-CREDS, phase transitioning is under the sole control of the Server,
therefore the value of the 'S' (Start) bit is meaningful only in messages sent by the Server.
The value of the 'S' (Start) bit in Peer's messages SHALL be set to '0x0' and SHALL be
ignored by the server.
</t>
<t>
When starting a new phase, the Server MUST set the 'S' (Start) bit
to '1' and the 'Phase' field to the current phase number (e.g., 0x01 for phase one, 0x02 for phase two, or 0x03 for phase three).
</t>
<t>
In case the first message of a phase is to be repeated (e.g., because of
processing multiple credentials), the
'S' (Start) bit SHALL be set to '0' (i.e., it should be set to '1' only on the first
occurrence and set to '0' in subsequent messages).
</t>
</section>
<section anchor="creds_phase_one" title="Phase One: Initialization">
<t>
The following figure provides the message flow for Phase One:
</t>
<figure title="EAP-CREDS Phase One Message Flow"><artwork><![CDATA[
,--------. ,----------.
|EAP Peer| |EAP Server|
`---+----' `----+-----'
| Outer Tunnel Established |
| <--------------------------------------->
| |
| [1] EAP-Request/EAP-CREDS(Type=Init) | ,---------!.
| { [ Version+ ], [ Challenge-Data ] }| |Phase One|_\
| <---------------------------------------- |Begins |
| | `-----------'
| [2] EAP-Response/EAP-CREDS(Type=Init) |
| { [ Version+ ], [ Protocols+ ], |
| [ Creds-Info+ ], [ Encoding+ ], | ,---------!.
| [ Format+ ], [ Token ], | |Phase One|_\
| [ Profile+ ], [ Challenge-Rsp ], | |Ends |
| [ Storage-Info ],[ Net-Usage] } | `-----------'
| ---------------------------------------->
| |
| |
]]></artwork></figure>
<t>[1] Server sends EAP-Request/EAP-CREDS(Type=Init):
<list>
<t>
After the establishment of the outer
mechanism (e.g., EAP-TLS, EAP-TEAP, EAP-TTLS, etc.), the server MAY
decide to start a credentials management session. In order to do that,
the Server sends an EAP-Request/EAP-CREDS(Type=Init) message to the Peer with
the 'S' (Start) bit set to '1' and the Phase field value set to '0x01'
(thus indicating the beginning of Phase One) as described in
<xref target="creds_header" />. Also, the Server
MAY use one or more ('Version') TLVs to indicate the supported versions.
</t>
<t>
The Server MAY also specify which versions of EAP-CREDS are supported
by adding zero, one or more ('Version') TLVs. If no ('Version') TLV is added
to the message, the Peer SHOULD assume the supported version is 1 ('0x01').
</t>
<t>
Optionally, the Server MAY also send a ('Challenge-Data') TLV
which includes chanllenge data value (usually some random value)
and a specified challenge type. The Peer MUST
use the specified type and use chanllenge data value for calculating
the ('Challenge-Response') TLV.
</t>
</list>
</t>
<t>[2] The Peer sends EAP-Response/EAP-CREDS(Type=Init)
<list>
<t>
The Peer, sends back a message that carries one
('Version') TLV to indicate the selected version of EAP-CREDS (i.e.
from the list provided by the server) (optional). If the client does
not include the ('Version') TLV, the Server MUST use the most recent
supported version of EAP-CREDS. Moreover, the Server includes one or
more ('Protocol') TLVs to indicate the list of supported provisioning
protocols, followed by one ('Creds-Info') TLVs for each installed
credentials to provide their status to the server (i.e., if multiple
credentials are configured on the Peer for this Network, then the Peer
MUST include one ('Creds-Info') TLV for each of them).
</t>
<t>
The Peer MAY also provide the list of supported Encodings and Formats
by adding one or more ('Encoding') and ('Formats')
TLVs. The Peer MAY also provide the Server with information about the
Peer's credentials storage by using the ('Storage-Info') TLV.
</t>
<t>
When there are no available credentials, the Peer MAY include an authorization
token that can be consumed by the Server for registering new credentials.
In particular, the Peer can include the ('Token') TLV to convey the
value of the token. The ('Challenge-Data') and ('Challenge-Response') TLVs,
instead, can be used to convey a challenge and its response
based on the authorization information. For example, suppose a public key hash
is present in the Token, the peer can generate some random data - or use the
one from the Server - and generate a signature on that value: the
signature SHALL be encoded in the ('Challenge-Response') TLV and it should
be calculated over the concatenation of values inside the ('Challenge-Data')
TLV and the ('Token') TLV.
</t>
<t>
Also, the Peer MAY add one or more ('Profile') TLVs to indicate to the Server
which profiles are requested/supported (e.g., a pre-configuration MAY exist
on the Peer with these ecosystem-specific identifiers).
</t>
<t>
Ultimately, the Peer MAY include additional metadata regarding the status of
the Peer. To this end, the Peer can use a ('Storage-Info') TLV to provide the server
with additional data about the Peer's capabilities and resources. Also, the
('Net-Usage') TLV can be used to provide the Server with the indication of
which network resources are needed by the Peer and what is its intended
utilization pattern(s).
</t>
<t>
The server checks that the Peer's selected protocol, version, and
parameters are supported and, if not (or if the server detects an
error), it can (a) send a non-recoverable error message to the peer,
notify the outer (tunneling) layer, and terminate the EAP-CREDS session, or
(b) start phase one again by sending a new ('EAP-CREDS-Init') message
that will also carry an ('ERROR') TLV that provides the Peer with the
reason the initial response was not acceptable. In this case, the
('Phase') field MUST be omitted since it is not the first message of
phase one. The server and the peer can repeat phase one until they reach
an agreement or the session is terminated by the Server.
</t>
</list>
</t>
<t>
<list>
<t>
NOTE WELL: The determination of the need to start phase two or not is based on the
contents of the ('Creds-Info') TLV sent by the Peer (e.g., a credential
is about to expire or a credential is simply missing).
</t>
</list>
</t>
</section>
<section anchor="creds_phase_two" title="Phase Two: Provisioning">
<t>
The following figure provides the message flow for Phase 2:
</t>
<figure title="EAP-CREDS Phase Two Message Flow"><artwork><![CDATA[
,--------. ,----------.
|EAP Peer| |EAP Server|
`---+----' `----+-----'
| [1] EAP-Request/EAP-CREDS(Type=Provisioning) |
| { Protocol, Action, | ,---------!.
| [ Creds-Info ], [ Params ], | |Phase Two|_\
| [ ProtoData ], [ ProtoHeaders ] } | |Begins |
| <---------------------------------------------- `-----------'
| |
| [2] EAP-Response/EAP-CREDS(Type=Provisioning) |
| { ProtoData, [ ProtoHeaders ] } |
| ---------------------------------------------->
| |
. .
. .
. .
. .
| [N] EAP-Response/EAP-CREDS(Type=Provisioning) |
| { [ Creds-Info ], [ ProtoData ], |
| [ ProtoHeaders ] } |
| <----------------------------------------------
| |
| [N+1] EAP-Request/EAP-CREDS(Type=Provisioning)| ,---------!.
| { [ ProtoData ], [ ProtoHeaders ] } | |Phase Two|_\
| ----------------------------------------------> |Ends |
| | `-----------'
| |
]]></artwork></figure>
<t>[1] The Server sends EAP-Request/EAP-CREDS(Type=Provisioning)
<list>
<t>
The first message of Phase Two indicates that the Server is
ready to initiate the selected provisioning protocol.This message contains
the parameters of the selected provisioning protocol in the ('Params')
(e.g., algorithm for generating credentials),
the description of installed credentials in the ('Creds-Info'),
the selected provisioning protocol's message data and some extra fields
(e.g., transport-protocol headers) in the ('ProtoData') and its content in
('ProtoHeaders') TLVs respectively.
</t>
</list>
</t>
<t>[2] The Peer sends EAP-Response/EAP-CREDS(Type=Provisioning)
<list>
<t>
After that, the Peer sends its first message to the Server by sending the
EAP-Response/EAP-CREDS(Type=Provisioning) message. This message contains
the selected provisioning protocol's message data and some extra fields
(e.g., transport-protocol headers) in the ('ProtoData') and its content in
('ProtoHeaders') TLVs respectively.
</t>
</list>
</t>
<t> [N=3] The Server sends EAP-Request/EAP-CREDS(Type=Provisioning)
<list>
<t>
The Server replies to the Peer's message with EAP-Request/EAP-CREDS(Type=Provisioning)
messages until the provisioning protocol reaches an end or an error condition
arise (non-recoverable).
</t>
</list>
</t>
<t>[N] The Server sends EAP-Request/EAP-CREDS(Type=Provisioning)
<list>
<t>
When the provisioning protocol has been executed for the specific set of
credentials, the server sends a last message that MUST include the description
of the provisioned credentials in a ('Creds-Info') TLV and MUST set the 'D' (Done)
bit in the EAP-CREDS message header to '1' to indicates that the server does not
have any more ('Type=Provisioning') messages for this credenital.
The final message does not need to be an empty one, i.e. other TLVs are still
allowed in the same message (e.g., the 'ProtoData' and the
'ProtoHeaders' ones).
</t>
</list>
</t>
<t>[N+1] The Peer sends EAP-Request/EAP-CREDS(Type=Provisioning)
<list>
<t>
The Peer MUST reply to the server with a ('Type=Provisioning') message that MUST
have the 'D' (Done) bit in the EAP-CREDS message header set to '1', thus indicating
that the credentials have been installed correctly. In case of errors, the Peer
MUST include the appropriate ('Error') TLV.
Also in this case, the final message does not need to be an empty one,
i.e. other TLVs are still allowed in the same message (e.g., tthe 'ProtoData' and the
'ProtoHeaders' ones).
</t>
</list>
</t>
<t>
At this point, the Server can decide to provision (or manage) another set of credentials
by issuing a new ('Type=Provisioning') message, or it can decide to start Phase Three by
sending its first ('Type=Validate') message, or it can terminate the EAP session.
</t>
</section>
<section anchor="creds_phase_three" title="Phase Three: Validation">
<t>
The following figure provides the message flow for Phase 3:
</t>
<figure title="EAP-CREDS Phase Three Message Flow"><artwork><![CDATA[
,--------. ,----------.
|EAP Peer| |EAP Server|
`---+----' `----+-----'
| [1] EAP-Request/EAP-CREDS(Type=Validate) | ,-----------!.
| { Creds-Info, Challenge-Data } | |Phase Three|_\
| <----------------------------------------- |Begins |
| | `-------------'
| [2] EAP-Response/EAP-CREDS(Type=Validate)| ,-----------!.
| { Challenge-Response } | |Phase Three|_\
| -----------------------------------------> |Ends |
| | `-------------'
| |
]]></artwork></figure>
<t>
Phase three is optional and it is used by the server to request the client to
validate (with proof) that the new credentials have been installed correctly
before issuing the final EAP-CREDS Success message.
</t>
<t>
<list>
<t>
NOTE WELL:
Phase Three introduces a dependency on the selected hashing algorithm
to provide common and easy way to check the integrity and functionality
of a newly installed set of credentials.
</t>
</list>
</t>
<t>[1] The Server sends EAP-Request/EAP-CREDS(Type=Validate)
<list>
<t>
In order to start Phase Three, the Server sends an
EAP-Request/EAP-CREDS(Type=Validate) message to the Peer.
The Server MUST include the ('Creds-Info') TLV to provide the indication about
which set of credentials the Server intends to validate. The Server MUST also include a randomly generated challenge in the message to the client. The type of challenge
determines in ('Challenge-Data') for the peer to calculate ('Challenge-Response').
EAP-CREDS defines the asymmetric and symmetric challenges in
<xref target="eap_creds_challenge_types" />
and others can be defined according to the specified rules.
</t>
<t>
As usual, the Server MUST set, in the headers, the 'S' (Start) bit to '1' in its first
message of Phase Three and the 'Phase' value shall be set to '3'
(beginning of Phase Three).
</t>
</list>
</t>
<t>
[2] The Peer sends EAP-Response/EAP-CREDS(Type=Validate)
<list>
<t>
When the client receives the Validate message from the server, it calculates the
response to the challenge and sends the response back to the server in a
EAP-Response/EAP-CREDS(Type=Validate) message.
When the 'EAP-CREDS-ASYMMETRIC-CHALLENGE' and 'EAP-CREDS-SYMMETRIC-CHALLENGE' values
are used in the 'Challenge types', the Peer MUST calculate the response as follows:
<list>
<t>
Public-Key
<list>
<t>
For any public-key based credentials (e.g., certificates or
raw key pairs), the response to the challenge is calculated by generating a
signature over the hashed value of the challenge. The hashing algorithm
to be used for this purpose is specified in <xref target="eap_creds_hashing" />.
The format of the signature in the ('Challenge-Response') TLV is the
concatenation of:
<list style="symbols">
<t>
The signatureAlgorithm (DER encoded) which contains the identifier for the
cryptographic algorithm used by the Peer to generate the signature using
<xref target="RFC3279" />, <xref target="RFC4055" />,
and <xref target="RFC4491" /> list supported signature
algorithms. Other signature algorithms MAY also be supported.
The definition of the signatureAlgorithm is provided in Section 4.1.1.2
of <xref target="RFC5280" />.
</t>
<t>
The signatureValue (DER encoded) which contains the digital signature
itself. The signature value is encoded as a BIT STRING and the details
of how to generate the signatures' structures can be found in
Section 4.1.1.3 of <xref target="RFC5280" /> and referenced material.
</t>
</list>
</t>
</list>
</t>
<t>
Symmetric Secret
<list>
<t>
For any symmetric based credentials (e.g., password or
Key), the response to the challenge is calculated by using the selected
hash function (see <xref target="eap_creds_hashing" />) on the concatenation of
(a) the value carried in the server-provided ('Challenge-Data') TLV, and
(b) the secret value itself (salted hash).
</t>
</list>
</t>
</list>
</t>
<t>
The initial values for the type of challenges are described in the
<xref target="eap_creds_challenge_types" />.
Other types of challenges MAY be defined according to the specified procedures.
</t>
<t>
In case of issues with the validation of newly deployed credentials, both
the Server and the Peer should consider those credentials invalid (or
unusable) and should issue the required failure message(s).
</t>
</list>
</t>
</section>
</section>
<!-- -->
<!-- End Of EAP Protocol Section -->
<!-- -->
<section anchor="creds_msg" title="EAP-CREDS Message Format">
<t>
The EAP-CREDS defines the following message types:
<list style="numbers">
<t>EAP-CREDS-Init</t>
<t>EAP-CREDS-Provisioning</t>
<t>EAP-CREDS-Validate</t>
</list>
</t>
<t>
Each of these message types have the basic structure as identified in
<xref target="creds_header" />.
EAP-CREDS messages contain zero, one, or more TLVs.
The internal structure of the different types of TLVs is described in
<xref target="creds_msg_payload" />,
while a detailed description of the EAP-CREDS message types is provided in
<xref target="creds_msg_types" />.
</t>
<section anchor="creds_header" title="Message Header">
<t>
The EAP-CREDS messages consist of the standard EAP header (see Section 4
of <xref target="RFC3748" />), followed by the message payload of the EAP-CREDS.
The header has the following structure:
</t>
<figure><artwork><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Identifier | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type |J|S|F|D| Phase | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Length | Data ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-.
]]></artwork></figure>
<t>
Where the Code, Identifier, Length, and Type fields are all part of the EAP
header as defined in <xref target="RFC3748" />. Since EAP-CREDS can only be
used as a tunneled mechanism, the presence of these fields is only for
backward compatibility with existing parsers. In particular, the 'Length'
field is used for fragmentation instead of the message length:
the message length is carried in the
'Message Length' field if Jumbo Message is indicated in the header.
</t>
<t>
The Type field in the EAP header is <TBD> for EAP-CREDS.
</t>
<t>
The Flags bitfield is used to convey status information (e.g., extra long
message, phase number, phase transitioning state). The transition-control
bit (i.e., the 'S' (Start) bit) are set in Server's messages and are ignored in
Peer's messages (the Server is the entity that unilaterally controls the
phase transition process).
The meanings of the bits in the 'Flags' field are as follows:
<list>
<t>
Bit 'J' (Jumbo Message) - If set, it indicates the presence of the 'Message Length' field.
This bit SHALL be used only when the size of the message exceeds the maximum
value allowed
in the 'Length' field. In this case, the 'Message Length' field is
added to the message and set to the whole message size and the 'Length'
field is used for the current fragment length.
If not set, the 'Message Length' field is not
present in the Message and the 'Length' field is used for the message size
(and the 'F' (Fragment) bit MUST be set to '0').
</t>
<t>
Bit 'S' (Start) - If set, this message is the first one of a new EAP-CREDS phase.
The value of the new phase is encoded in the 'Phase' field.
</t>
<t>
Bit 'F' (Fragment) - If set, this message is a fragment of a message. In this case, the
'Data' field is to be concatenated with all messages with the 'F' (Fragment) bit
set to '1' until the message with the 'F' (Fragment) bit set to '0' that indicates
the end of the message. If the message is not fragmented, the 'F' (Fragment) bit
MUST be set to '0'. The use of this bit is required when the tunneling
method does not provide support for messages up to 2^32 bits in size.
</t>
<t>
Bit 'D' (Done) - This bit is used in Phase Two and Phase Three to indicate that the
specific operation for the identified credential is over. For example,
when multiple credentials exist on the Peer and the Server needs to
manage and validate one of them. In its last message, when the provisioning
protocol is done, the server sets the 'D' (Done) bit to indicate that
it is done. The Peer, in its reply, sets the bit to indicate
the end of provisioning for this credentials is also over. After that, the
Server can continue Phase Two, transition to Phase Three, or terminate
the EAP session.
</t>
</list>
</t>
<t>
The Phase field is a 4-bits value and identifies the EAP-CREDS phase for the current message.
The version of EAP-CREDS described in this document supports three values for this
field:
<list>
<t>0x01 - Phase One</t>
<t>0x02 - Phase Two</t>
<t>0x03 - Phase Three</t>
</list>
</t>
<t>
A detailed explanation of the 'Phase' and 'Flags' fields of the message headers
is provided in <xref target="phase_transitioning" />.
</t>
<t>
The Data field is the message payload. The full description of this field
is provided in the next section.
</t>
</section>
<section anchor="creds_msg_payload" title="Message Payload">
<t>
The Data part of the message is organized as zero, one, or more TLV
objects whose structure is defined in this section.
</t>
<t>
Each TLV object has the same basic structure that is defined as follows:
</t>
<figure><artwork><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Type | TLV Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Value ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork></figure>
<t>Where:</t>
<t>TLV-Type (uint8)
<list>
<t>
This field is used to indicate the type of data that the TLV
carries. The type of TLV determines its internal structure.
The supported values for this fields are provided in the following
table:
</t>
</list>
</t>
<t>Length (uint24)
<list>
<t>
This field carries the size of the value of the TLV. In particular,
the overall size of a TLV (i.e., the header plus the value) can be
calculated by adding the size of the header (6 octets) to the value
of the Length field (i.e., the size of the TLV's value).
</t>
</list>
</t>
<texttable anchor="eap_creds_tlvs_table" title="EAP-CREDS Supported TLVs Types">
<ttcol align="center">TLV Name</ttcol>
<ttcol align="left">TLV Type</ttcol>
<ttcol align="center">Scope/Usage</ttcol>
<c><TBD></c>
<c>Action TLV</c>
<c>Phase Two</c>
<c><TBD></c>
<c>Certificate-Data TLV</c>
<c>Phase Two</c>
<c><TBD></c>
<c>Challenge-Data TLV</c>
<c>Phase Two, Phase Three</c>
<c><TBD></c>
<c>Challenge-Response TLV</c>
<c>Phase Two, Phase Three</c>
<c><TBD></c>
<c>Credentials-Data TLV</c>
<c>Phase Two</c>
<c><TBD></c>
<c>Creds-Info TLV</c>
<c>Phase Two, Phase Three</c>
<c><TBD></c>
<c>Error TLV</c>
<c>All Phases</c>
<c><TBD></c>
<c>Net-Usage TLV</c>
<c>Phase One</c>
<!--
<c><TBD></c>
<c>Phase-Control TLV</c>
<c>All Phases</c>
-->
<c><TBD></c>
<c>Profile TLV</c>
<c>Phase Two</c>
<c><TBD></c>
<c>Protocol TLV</c>
<c>Phase One, Phase Two</c>
<c><TBD></c>
<c>ProtoData TLV</c>
<c>Phase Two</c>
<c><TBD></c>
<c>ProtoHeaders TLV</c>
<c>Phase Two</c>
<c><TBD></c>
<c>Params TLV</c>
<c>Phase Two</c>
<c><TBD></c>
<c>Token TLV</c>
<c>Phase One</c>
<c><TBD></c>
<c>Version TLV</c>
<c>Phase One</c>
</texttable>
<t>TLV Value ( > 1 octet )
<list>
<t>
This field carries data for the identified TLV. The internal structure
is determined by the TLV Type field.
</t>
</list>
</t>
<t>
The rest of this section describes the structure of the different
supported TLVs and their usage in the different messages.
</t>
</section>
<section anchor="creds_tlvs_types" title="EAP-CREDS defined TLVs">
<t>
EAP-CREDS messages's payload comprises zero, one, or more TLVs that are encoded
in a single EAP-CREDS message.
The values for the TLV Type that are supported by this specifications are listed
in <xref target="eap_creds_tlvs_table" />.