Internet DRAFT - draft-lear-eap-teap-brski
draft-lear-eap-teap-brski
Network Working Group E. Lear
Internet-Draft O. Friel
Updates: RFC7170 (if approved) N. Cam-Winget
Intended status: Standards Track Cisco Systems
Expires: 26 February 2022 D. Harkins
HP Enterprise
25 August 2021
TEAP Update and Extensions for Bootstrapping
draft-lear-eap-teap-brski-06
Abstract
In certain environments, in order for a device to establish any layer
three communications, it is necessary for that device to be properly
credentialed. This is a relatively easy problem to solve when a
device is associated with a human being and has both input and
display functions. It is less easy when the human, input, and
display functions are not present. To address this case, this memo
specifies extensions to the Tunnel Extensible Authentication Protocol
(TEAP) method that leverages Bootstrapping Remote Secure Key
Infrastructures (BRSKI) in order to provide a credential to a device
at layer two. The basis of this work is that a manufacturer will
introduce the device and the local deployment through cryptographic
means. In this sense the same trust model as BRSKI is used.
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
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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 26 February 2022.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. TEAP BRSKI Architecture . . . . . . . . . . . . . . . . . . . 4
3. BRSKI Bootstrap and Enroll Operation . . . . . . . . . . . . 4
3.1. Discovery of Trusted MASA . . . . . . . . . . . . . . . . 5
3.2. Executing BRSKI in a TEAP Tunnel . . . . . . . . . . . . 5
4. PKI Certificate Considerations . . . . . . . . . . . . . . . 9
4.1. TEAP Tunnel Establishment . . . . . . . . . . . . . . . . 9
4.2. BRSKI Trust Establishment . . . . . . . . . . . . . . . . 11
4.3. Certificate Expiration Times . . . . . . . . . . . . . . 12
4.4. LDevID Subject and Subject Alternative Names . . . . . . 12
4.5. PKCS#10 Retry Handling . . . . . . . . . . . . . . . . . 13
5. Peer Identity . . . . . . . . . . . . . . . . . . . . . . . . 13
6. Channel and Crypto Binding . . . . . . . . . . . . . . . . . 14
7. Protocol Flows . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. TEAP Server Grants Access . . . . . . . . . . . . . . . . 14
7.2. TEAP Server Instructs Client to Perform BRSKI Flow . . . 16
7.3. TEAP Server Instructs Client to Reenroll . . . . . . . . 20
7.4. Out of Band Reenroll . . . . . . . . . . . . . . . . . . 22
8. TEAP TLV Formats . . . . . . . . . . . . . . . . . . . . . . 22
8.1. New TLVs . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1.1. BRSKI-RequestVoucher TLV . . . . . . . . . . . . . . 23
8.1.2. BRSKI-Voucher TLV . . . . . . . . . . . . . . . . . . 23
8.1.3. CSR-Attributes TLV . . . . . . . . . . . . . . . . . 24
8.1.4. Retry-After TLV . . . . . . . . . . . . . . . . . . . 25
8.1.5. NAI TLV . . . . . . . . . . . . . . . . . . . . . . . 25
8.2. Existing TEAP TLV Specifications . . . . . . . . . . . . 25
8.2.1. PKCS#10 TLV . . . . . . . . . . . . . . . . . . . . . 25
8.3. TLV Rules . . . . . . . . . . . . . . . . . . . . . . . . 26
9. Fragmentation . . . . . . . . . . . . . . . . . . . . . . . . 26
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
11. Security Considerations . . . . . . . . . . . . . . . . . . . 27
11.1. Issues with Provisionally Authenticated TEAP . . . . . . 28
11.2. Attack Against Discovery . . . . . . . . . . . . . . . . 28
11.3. TEAP Server as Registration Authority . . . . . . . . . 28
11.4. Trust of Registrar . . . . . . . . . . . . . . . . . . . 29
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 29
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13. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
13.1. Normative References . . . . . . . . . . . . . . . . . . 29
13.2. Informative References . . . . . . . . . . . . . . . . . 30
Appendix A. Changes from Earlier Versions . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 30
1. Introduction
[I-D.ietf-anima-bootstrapping-keyinfra] (BRSKI) specifies a means to
provision credentials to be used as credentials to operationally
access networks. It was designed as a standalone means where some
limited access to an IP network is already available. This is not
always the case. For example, IEEE 802.11 networks generally require
authentication prior to any form of address assignment. While it is
possible to assign an IP address to a device on some form of an open
network, or to accept some sort of default credential to establish
initial IP connectivity, the steps that would then follow might well
require that the device is placed on a new network, requiring
reseting all layer three parameters.
A more natural approach in such cases is to more tightly bind the
provisioning of credentials with the authentication mechanism. One
such way to do this is to make use of the Extensible Authentication
Protocol (EAP) [RFC3748] and the Tunnel Extensible Authentication
Protocol (TEAP) method [RFC7170]. Thus we define new TEAP Type-
Length-Value (TLV) objects that can be used to transport the BRSKI
protocol messages within the context of a TEAP TLS tunnel.
[RFC7170] discusses the notion of provisioning peers. Several
different mechanisms are available. Section 3.8 of that document
acknowledges the concept of not initially authenticating the outer
TLS session so that provisioning may occur. In addition, exchange of
multiple TLV messages between client and EAP server permits multiple
provisioning steps.
1.1. Terminology
The reader is presumed to be familiar with EAP terminology as stated
in [RFC3748]. In addition, the following terms are commonly used in
this document.
* BRSKI: Bootstrapping Remote Secure Key Infrastructures, as defined
in [I-D.ietf-anima-bootstrapping-keyinfra]. The term is also used
to refer to the flow described in that document.
* EST: Enrollment over Secure Transport, as defined in [RFC7030].
* Voucher: a signed JSON object as defined in [RFC8366].
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2. TEAP BRSKI Architecture
The TEAP BRSKI architecture is illustrated in Section 3. The device
talks to the TEAP server via the Authenticator using any compliant
transport such as [IEEE8021X]. The architecture illustrated shows an
Authenticator distinct from the TEAP server. This is a deployment
optimization and when so deployed the communication between
Authenticator and TEAP server is a AAA protocol such as RADIUS or
DIAMETER.
The architecture illustrated shows a co-located TEAP server and BRSKI
registrar. Not only are these two functions co-located, they MUST be
the same entity. This ensures that the entity identified in the
device's voucher request (the TEAP server) is the same entity that
signs the voucher request (the registrar).
The registrar communicates with the BRSKI MASA service for the
purposes of getting signed vouchers.
The registrar also communicates with a Certificate Authority in order
to issue LDevIDs. The architecture shows the registrar and CA as
being two logically separate entities, however the CA may be
integrated into the registrar. The device is not explicitly aware of
whether the CA and registrar functions are integrated.
+--------+ +---------+ +---------+ +------+
| | | | | TEAP |<--->| MASA |
| | | Authen- | | server | +------+
| Device |<--->| ticator |<--->| |
| | | | | BRSKI | +------+
| | | | |Registrar|<--->| CA |
+--------+ +---------+ +---------+ +------+
3. BRSKI Bootstrap and Enroll Operation
This section summarises the current BRSKI operation. The BRSKI flow
assumes the device has an IDevID and has a manufacturer installed
trust anchor that can be used to validate the BRSKI voucher. The
BRSKI flow compromises serveral main steps from the perspective of
the device:
* Step 1: Device discovers the registrar
* Step 2: Device establishes provisional TLS connection to registrar
* Step 3: Device sends voucher request message and receives signed
voucher response
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* Step 4: Device validates voucher and validates provisional TLS
connection to registrar
* Step 5: Device downloads additional local domain CA information
* Step 6: Device downloads Certificate Signing Request (CSR)
attributes
* Step 7: Device does a certificate enroll to obtain an LDevID
* Step 8: Device periodically reenrolls via EST to refresh its
LDevID
Most of the operational steps require the device, and thus its
internal state machine, to automatically complete the next step
without being explicitly instructed to do so by the registrar. For
example, the registrar does not explicitly tell the device to
download additional local domain CA information, or to do an EST
enroll to obtain an LDevID.
3.1. Discovery of Trusted MASA
BRSKI section 2.8 outlines how the Registrar discovers the correct
MASA to connect with. BRSKI section 5.3 outlines how the Registrar
can make policy decisions about which devices to trust.
Similar approaches are applicable for TEAP servers executing BRSKI.
For example, the TEAP server may be configured with a list of trusted
manufacturing CAs. During device bootstrap, only devices with an
IDevID signed by a trusted manufacturing CA may be allowed to
etablishes a TLS connection with the TEAP server, and the TEAP server
could then extract the MASA URI from the device's IDevID.
3.2. Executing BRSKI in a TEAP Tunnel
This section outlines how the main BRSKI steps outlined above map to
TEAP, and how BRSKI and enrollment can be accomplished inside a TEAP
TLS tunnel. The following new TEAP TLVs are introduced:
* BRSKI-VoucherRequest
* BRSKI-Voucher
* CSR-Attributes
The following steps outline how the above BRSKI flow maps to TEAP.
* Step 1: Device discovers the registrar
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When BRSKI is executed in a TEAP tunnel, the device exchanges BRSKI
TLVs with the TEAP server. The discovery process for devices is
therefore the standard wired or wireless LAN EAP server discovery
process. The discovery processes outlined in section 4 of
[I-D.ietf-anima-bootstrapping-keyinfra] are not required for initial
discovery of the registrar.
* Step 2: Device establishes provisional TLS connection to registrar
The device establishes an outer TEAP tunnel with the TEAP server and
does not validate the server certificate. The device presents its
LDevID as its identity certificate if it has a valid LDevID,
otherwise it presents its IDevID. The TEAP server validates the
device's certificate using its implicit or explicit trust anchor
database. If the device presents an IDevID it is verified against a
database of trusted manufacturer certificates. Server policy may
also be used to control which certificate the device is allowed
present, as described in section {pki-certificate-authority-
considerations}.
If the presented credential is sufficient to grant access, the TEAP
server can return a TEAP Result TLV indicating success immediately.
The device may still send a Request-Action TLV including a BRSKI-
VoucherRequest TLV in response to the TEAP Result TLV if it does not
have, but requires, provisioning of trust anchors for validating the
TEAP server certificate. Note that no inner EAP method is required
for this, only an exchange of TEAP TLVs.
[todo] Question: as the device wants the server to reply with a
BRSKI-Voucher TLV, does it really send a Request-Action TLV
containing a BRSKI-VoucherRequest TLV, or does it send a Request-
Action TLV containing a BRSKI-Voucher TLV?? The TEAP draft is a bit
ambiguous here. Normally, if one end sends a Request-Action
including XXX-TLV, it means it wants the far end ot send an XXX-
TLV...
[todo] Question: general TEAP protocol question: does the device have
to send a Request-Action w/BRSKI-VoucherRequest or can it send a
BRSKI-VoucherRequest on its own? I'm not clear on this.
If the TEAP server requires that the device execute a BRSKI flow, the
server sends a Request-Action TLV that includes a BRSKI-
VoucherRequest TLV. For example, if the device presented its IDevID
but the TEAP server requires an LDevID.
[todo] Question: to nit pick, the server should send a Request-Action
TLV including a PKCS#10 TLV to tell the client to enroll. How does
the server really know that the client has the correct trust
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established (as previously received by a BRSKI-Voucher)? If the
client sends an IDevID, does server always send a Request-Action
including both BRSKI-VoucherRequest and PKCS#10 TLVs? Whats the
client behaviour? I assume client can spontaneously send BRSKI-
VoucherRequest and/or PCSK#10 without being explicitly instructed to.
Just need to get the language correct here.
The TEAP server may also require the device to reenroll, for example,
if the device presented a valid LDevID that is very closed to
expiration. The server may instruct a device to reenroll by sending
a Request-Action TLV that includes a zero byte length PKCS#10 TLV.
* Step 3: Device sends voucher request message and receives signed
voucher response
The device sends a BRSKI-RequestVoucher TLV to the TEAP server. The
TEAP server forwards the RequestVoucher message to the MASA server,
and the MASA server replies with a signed voucher. The TEAP server
sends a BRSKI-Voucher TLV to the device.
If the MASA server does not issue a signed voucher, the TEAP server
sends an EAP-Error TLV with a suitable error code to the device.
For wireless devices in particular, it is important that the MASA
server only return a voucher for devices known to be associated with
a particular registrar. In this sense, success indicates that the
device is on the correct network, while failure indicates the device
should try to provision itself within wireless networks (e.g, go to
the next SSID).
* Step 4: Device validates voucher and validates provisional TLS
connection to registrar
The device validates the signed voucher using its manufacturer
installed trust anchor, and uses the CA information in the voucher to
validate the TLS connection to the TEAP server.
If the device fails to validate the voucher, then it sends a TEAP-
Error TLV indicating failiure to the TEAP server.
Similarly, if the device validates the voucher, but fails to validate
the provisional TLS connection, then it sends a TEAP-Error TLV
indicating failure to the TEAP server. Note that the outer TLS
tunnel has already been established, thus allowing the client to send
a TEAP-Error TLV to the server inside that tunnel to indicate that it
failed to verify the provisionally accepted outer TLS tunnel server
identity.
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* Step 5: Device downloads additional local domain CA information
On completion of the BRSKI flow, the device SHOULD send a Trusted-
Server-Root TLV to the TEAP server in order to discover additional
local domain CAs. This is equivalent to section [todo] from
[I-D.ietf-anima-bootstrapping-keyinfra].
* Step 6: Device downloads CSR attributes
No later than the completion of step 5, server MUST send a CSR-
Attributes TLV to peer server in order to discover the correct fields
to include when it enrolls to get an LDevID.
* Step 7: Device does a certificate enroll to obtain an LDevID
When executing the BRSKI flow inside a TEAP tunnel, the device does
not directly leverage EST when doing its initial enroll. Instead,
the device uses the existing TEAP PKCS#10 and PCKS#7 TEAP mechanisms.
Once the BRSKI flow is complete, the device can now send a PKCS#10
TLV to enroll and request an LDevID. If the TEAP server instructed
the device to start the BRSKI flow via a Request-Action TLV that
includes a BRSKI-RequestVoucher TLV, then the device MUST send a
PKCS#10 in order to start the enroll process. The TEAP server will
handle the PKCS#10 and ultimately return a PKCS#7 including an LDevID
to the device.
If the TEAP server granted the device access on completion of the
outer TEAP TLS tunnel in step 2 without sending a Request-Action TLV,
the device does not have to send a PKCS#10 to enroll.
At this point, the device is said to be provisioned for local network
access, and may authenticate in the future via 802.1X with its newly
acquired credentials.
* Step 8: Device periodically reenrolls to refresh its LDevID
When a device's LDevID is close to expiration, there are two options
for re-enrollment in order to obtain a fresh LDevID. As outlined in
Step 2 above, the TEAP server may instruct the device to reenroll by
sending a Request-Action TLV including a PKCS#10 TLV. If the TEAP
server explicilty instructs the device to reenroll via these TLV
exchange, then the device MUST send a PKCS#10 to reenroll and request
a fresh LDevID.
However, the device SHOULD reenroll if it determines that its LDevID
is close to expiration without waiting for explicit instruction from
the TEAP server. There are two options to do this.
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Option 1: The device reenrolls for a new LDevID directly with the EST
CA outside the context of the 802.1X TEAP flow. The device uses the
registrar discovery mechanisms oulined in
[I-D.ietf-anima-bootstrapping-keyinfra] to discover the registrar and
the device sends the EST reenroll messages to the discovered
registrar endpoint. No new TEAP TLVs are defined to facilitate
discover of the registrar or EST endpoints inside the context of the
TEAP tunnel.
Option 2: When the device is performing a periodic 802.1X
authentication using its current LDevID, it reenrolls for a new
LDevID by sending a PKCS#10 TLV inside the TEAP TLS tunnel.
4. PKI Certificate Considerations
There are multiple noteworthy PKI certificate handling
considerations. These include:
* PKI CA handling when establishing the TEAP tunnel
* PKI CA handling establishing trust using BRSKI
* IDevID and LDevID expiration times
* Specifying LDevID Subject and Subject Alternative Names
* PKCS#10 retry handling
These are described in more detail here.
4.1. TEAP Tunnel Establishment
Because this method establishes a client identity, if the peer has
not been previously bootstrapped, or otherwise cannot successfully
authenticate, it will use a generic identity string of teap-
bootstrap@TBD1 as its network access identifier (NAI).
BRSKI section 5.3 outlines the policy decisions a Registrar may make
when deciding whether to accept connections from clients. Similarly,
the TEAP server operator may configure a set of trusted CAs for
validating incoming TLS connections from clients. The operator may
want to 'allow any device from a specific vendor', or from a set of
vendors, to access the network. Network operators may do this by
restricting network access to clients that have a certificate signed
by one of a small set of trusted manufacturer/supplier CAs.
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When the client sends its ClientHello to initiate TLS tunnel
establishment, it is possible for the TEAP server to restrict the
certificates that the client can use for tunnel establishment by
including a list of CA distinguished names in the
certificate_authorities field in the CertificateRequest message. The
client should only continue with the handshake if it has a
certificate signed by one of the indicated CAs.
In practice, network operators will likely want to onboard devices
from a large number of device manufacturers, with each manufacturer
using a different root CA when issuing IDevIDs. If the number of
different manufacturer root CAs is large, this could result in very
large TLS handshake messages. Therefore, the TEAP server may send a
CertificateRequest message and not specify any
certificate_authorities, thus allowing the client present a
certificate signed by any authority in its Certificate message.
If the client has both an IDevID and an LDevID, the client should
present the LDevID in preference to its IDevID, if allowed by server
policy.
Once the client has sent its TLS Finished message, the TEAP server
can make a policy decision, based on the CA used to sign the client's
certificate, on whether to establish the outer TLS tunnel or not.
The TEAP server may delegate policy decisions to the MASA or CA
function. For example, the TEAP server may declare EAP success and
grant network access if the client presents a valid LDevID signed by
a trusted domain CA. However, if the client presents an IDevID
signed by a trusted manufacturer CA, the TEAP server may establish
the TLS tunnel but not declare EAP success and grant network access
until the client successfully completes a BRSKI Voucher exchange and
PKCS#10/PKCS#7 exchange inside that tunnel.
It is recommended that the client validate the certificate presented
by the server in the server's Certificate message, but this may not
be possible for clients that have not yet provisioned appropriate
trust anchors. If the client is in the provisioning phase and has
not yet completed a BRSKI flow, it will not have trust anchors
installed yet, and thus will not be able to validate the server's
certificate. The client must however note the certificate presented
by the server for (i) inclusion in the BRSKI-RequestVoucher TLV and
for (ii) validation once the client has discovered the local domain
trust anchors.
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If the client does not present a suitable certificate to the server,
the server MUST terminate the connection and fail the EAP request.
If the TEAP server is unable to validate the client's certificate
using its implicit or explicit trust anchor database it MUST fail the
EAP request.
On establishment of the outer TLS tunnel, the TEAP server will make a
policy decision on next steps. Possible policy decisions include:
* Option 1: Server grants client full network access and returns
EAP-Success. This will typically happen when the client presents
a valid LDevID. Network policy may grant client network access
based on IDevID without requiring the device to enroll to obtain
an LDevID.
* Option 2: Server requires that client perform a full BRSKI flow,
and then enroll to get an LDevID. This will typically happen when
the client presents a valid IDevID and network policy requires all
clients to have LDevIDs. The server sends a Request-Action TLV
that includes a BRSKI-RequestVoucher TLV to the client to instruct
it to start the BRSKI flow.
* Option 3: Server requires that the client reenroll to obtain a new
LDevID. This could happen when the client presents a valid LDevID
that is very close to expiration time, or the server's policy
requires an LDevID update. The server sends an Action-Request TLV
including a PKCS#10 TLV to the client to instruct it to reenroll.
4.2. BRSKI Trust Establishment
If the server requires that client perform a full BRSKI flow, it
sends a Request-Action TLV that includes a zero byte length BRSKI-
RequestVoucher TLV to the client. The client sends a new BRSKI-
RequestVoucher TLV to the server, which contains all data specified
in [I-D.ietf-anima-bootstrapping-keyinfra] section 5.2. The client
includes the server certificate it received in the server's
Certificate message during outer TLS tunnel establishment in the
proximity-registrar-cert field. The client signs the request using
its IDevID.
The server includes all additional information as required by
[I-D.ietf-anima-bootstrapping-keyinfra] section 5.4 and signs the
request prior to forwarding to the MASA.
The MASA responds as per [I-D.ietf-anima-bootstrapping-keyinfra]
section 5.5. The response may indicate failure and the server should
react accordingly to failures by sending a failure response to the
client, and failing the TEAP method.
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If the MASA replies with a signed voucher and a successful result,
the server then forwards this response to the client in a BRSKI-
Voucher TLV.
When the client receives the signed voucher, it validates the
signature using its built in trust anchor list, and extracts the
pinned-domain-cert field. The client must use the CA included in the
pinned-domain-cert to validate the certificate that was presented by
the server when establishing the outer TLS tunnel. If this
certificate validation fails, the client must fail the TEAP request
and not connect to the network.
[TBD- based on client responses, the registrar sends a status update
to the MASA]
4.3. Certificate Expiration Times
[IEEE8021AR] section 7.2.7.2 states:
notAfter: The latest time a DevID is expected to be used. Devices
possessing an IDevID are expected to operate indefinitely into the
future and should use the value 99991231235959Z. Solutions
verifying an IDevID are expected to accept this value
indefinitely.
TEAP servers SHOULD follow the 802.1AR standard when validating
IDevIDs.
TEAP servers SHOULD reject LDevIDs with expired certificates and
SHOULD NOT allow clients to connect with recently expired LDevIDs.
If a client presents a recently expired LDevID it SHOULD be forced to
authenticate using its IDevID and then reenroll to obtain a valid
LDevID.
4.4. LDevID Subject and Subject Alternative Names
BRSKI section 5.9.2 specifies that the pledge MUST send a CSR
Attributes request to the registrar. The registrar MAY use this
mechanism to instruct the pledge about the identities it should
include in the CSR request it sends as part of enrollment. The
registrar may use this mechanism to tell the pledge what Subject or
Subject Alternative Name identity information to include in its CSR
request. This can be useful if the Subject must have a specific
value in order to complete enrollment with the CA.
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4.5. PKCS#10 Retry Handling
They will be scenarios where the TEAP server is willing to handle a
PKCS#10 request from a client and issue a certificate via a PKCS#7
response, however, the TEAP server is unable to immediately
completely the request and needs to instruct the client to retry
later after a specified time interval.
A new Retry-After TLV is defined that the TEAP server uses to specify
a retry interval in seconds. New error codes are defined to handle
these two alternate retry scenarios.
* The TEAP tunnel remains up: The client is instructed to resend the
PKCS#10 request after a retry interval but inside the same TEAP
tunnel. The TEAP server returns a Retry-After TLV to the client,
and returns an Error TLV with a new code in the 1000-1999 range.
* The TEAP tunnel is torn down: The client is instructed to
establish a new TEAP connection and TEAP tunnel after a retry
interval, and resend the PKCS#10 request indside the new tunnel.
The TEAP server returns a Retry-After TLV to the client, and
returns an Error TLV with a new code in the 2000-2999 range.
5. Peer Identity
EAP [RFC3748] recommends that "the Identity Response be used
primarily for routing purposes and selecting which EAP method to
use". NAI [RFC7542] recommends ommitting the username part of an NAI
in order to support username privacy, where appropriate.
A device that has not been bootstrapped at all SHOULD send an
identity of teap-bootstrap@TBD1. Otherwise, a device SHOULD send its
configured NAI.
The TEAP server may specify an NAI that it wishes the device to use.
For example, the server may want a bootstrapped device to use an NAI
of "abc123@example.com", or simply an NAI of "@example.com". This
could be desirable in order to facilitate roaming scenarios. The
server can do this by sending the device an NAI TLV inside the TEAP
tunnel.
If the server specifies an NAI TLV, and the device handles the TLV,
the device MAY use the specified NAI in all subsequent EAP
authentication flows. If the device is not willing to handle the NAI
TLV, it MUST reply with an Error TLV.
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Authentication servers implementing this specification MAY reply with
an Error TLV to any unrecognized NAI, or MAY attempt to bootstrap the
device, regardless of the NAI. A device receving an Error from the
server MAY attempt a new session without the NAI in order to
bootstrap.
6. Channel and Crypto Binding
As the TEAP BRSKI flow does not define or require an inner EAP
method, there is no explicit need for exchange of Channel-Binding
TLVs between the device and the TEAP server.
The TEAP BRSKI TLVs are expected to occur at the beginning of the
TEAP Phase 2 and MUST occur before the final Crypto-Binding TLV.
This draft does not exclude the possibility of having other EAP
methods occur following the TEAP BRSKI TLVs and as such, the Crypto-
Binding TLV process rules as defined in [RFC7170] apply.
7. Protocol Flows
This section outlines protocol flows that map to the three server
policy options described in section Section 4.1. The protocol flows
illustrate a TLS1.2 exchange. Pertinent notes are outlined in the
protocol flows.
7.1. TEAP Server Grants Access
In this flow, the server grants access as server policy allows the
client to access the network based on the identity certificate that
the client presented. This means that either (i) the client has
previously completed BRSKI and has presented a valid LDevID or (ii)
the client presents an IDevID and network policy allows access based
purely on IDevID.
,------. ,----------.
|Client| |TEAPServer|
`--+---' `----+-----'
| EAP-Request/ |
| Identity |
| <---------------------
| |
| EAP-Response/ |
| Type=Identity |
| --------------------->
| |
| EAP-Request/ |
| Type=TEAP, |
| TEAP Start, |
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| Authority-ID TLV |
| <---------------------
| |
| EAP-Response/ |
| Type=TEAP, |
| TLS(ClientHello) |
| --------------------->
| |
| EAP-Request/ |
,---!. | Type=TEAP, |
|(1)|_\| TLS(ServerHello, |
|(2) || ServerKeyExchange, |
`-----'| ServerHelloDone) |
| <---------------------
| |
| EAP-Response/ |
| Type=TEAP, |
,---!. | ClientKeyExchange, |
|(3)|_\| CertificateVerify, |
`-----'| ChangeCipherSpec, |
| Finished) |
| --------------------->
| |
| EAP-Request/ |
| Type=TEAP, |
| TLS(ChangeCipherSpec,|
| Finished), |
| {Crypto-Binding TLV, |
| Result TLV=Success} |
| <---------------------
| |
| EAP-Response/ |
| Type=TEAP, |
| {Crypto-Binding TLV, |
| Result TLV=Success} |
| --------------------->
| |
| EAP-Success |
| <---------------------
,--+---. ,----+-----.
|Client| |TEAPServer|
`------' `----------'
Figure 1: TEAP Server Grants Access
Notes:
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(1) If the client has completed the BRSKI flow and has locally
significant trust anchors, it must validate the Certificate received
from the server. If the client has not yet completed the BRSKI flow,
then it provisionally accepts the server Certificate and must
validate it later once BRSKI is complete.
(2) The server may include certificate_authorities field in the
CertificateRequest message in order to restrict the identity
certificates that the device is allowed present.
(3) The device will present its LDevID, if it has one, in preference
to its IDevID, if allowed by server policy.
7.2. TEAP Server Instructs Client to Perform BRSKI Flow
In this two part flow, the server instructs the client to perform a
BRSKI flow by exchanging TLVs once the outer TLS tunnel is
established. After that, enrollment takes place.
In the first part of the flow, the MASA is depicted on the right.
,------. ,----------. ,----.
|Client| |TEAPServer| |MASA|
`--+---' `----+-----' `-+--'
| EAP-Request/ | |
| Type=Identity | |
| <----------------------------------- |
| | |
| EAP-Response/ | |
| Type=Identity | |
| -----------------------------------> |
| | |
| EAP-Request/ | |
,---!. | Type=TEAP, | |
|(1)|_\| TEAP Start, | |
`-----'| Authority-ID TLV | |
| <----------------------------------- |
| | |
| EAP-Response/ | |
| Type=TEAP, | |
| TLS(ClientHello) | |
| -----------------------------------> |
| | |
| EAP-Request/ | |
| Type=TEAP, | |
| TLS(ServerHello, | |
| Certificate, | |
| ServerKeyExchange, | |
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| CertificateRequest, | |
| ServerHelloDone) | |
| <----------------------------------- |
| | |
| EAP-Response/ | |
| Type=TEAP, | |
| TLS(Certificate | |
| ClientKeyExchange, | |
| CertificateVerify, | |
| ChangeCipherSpec, | |
| Finished) | |
| -----------------------------------> |
| | |
| EAP-Request/ | |
| Type=TEAP, | |
| TLS(ChangeCipherSpec, | |
| Finished), | |
| {Crypto-Binding TLV, | |
| Result TLV=Success} | |
| <----------------------------------- |
| | |
| EAP-Response/ | |
| ,Type=TEAP, | |
| {Crypto-Binding TLV, | |
| Result TLV=Success} | |
| -----------------------------------> |
| | |
,-------------------------------------------------!. |
|At this stage the outer TLS tunnel is established|_\ |
|The following message exchanges are for BRSKI | |
`---------------------------------------------------' |
| EAP-Request/ | |
| Type=TEAP, | |
| {Request-Action TLV: | |
| Status=Failure, | |
,---!. | Action=Process-TLV, | |
|(2)|_\| TLV=Request-Voucher, | |
`-----'| TLV=Trusted-Server-Root, | |
| TLV=CSR-Attributes, | |
| TLV=PKCS#10} | |
| <----------------------------------- |
| | |
| EAP-Response/ | |
,---!. | Type=TEAP, | |
|(3)|_\| {Request-Voucher TLV} | |
`-----'| -----------------------------------> |
| | |
| | RequestVoucher |
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| | ----------------->
| | |
| | Voucher |
| | <-----------------
| | |
| EAP-Request/ | |
,---!. | Type=TEAP, | |
|(4)|_\| {Voucher TLV} | |
`-----'| <----------------------------------- |
| | |
| EAP-Response/ | |
| Type=TEAP,{Trusted-Server-Root TLV}| |
| -----------------------------------> |
| | |
| EAP-Request/ | |
,---!. | Type=TEAP, | |
|(5)|_\| {Trusted-Server-Root TLV} | |
`-----'| <----------------------------------- |
| | |
| EAP-Response/ | |
| Type=TEAP,{CSR-Attributes TLV} | |
| -----------------------------------> |
| | |
| EAP-Request/ | |
| Type=TEAP, | |
| {CSR-Attributes TLV} | |
| <----------------------------------- |
,--+---. ,----+-----. ,-+--.
|Client| |TEAPServer| |MASA|
`------' `----------' `----'
Figure 2: TEAP Server Instructs Client to Perform BRSKI Flow
The second part of the flow depicts the CA on the right.
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,------. ,----------. ,--.
|Client| |TEAPServer| |CA|
`--+---' `----+-----' `+-'
| EAP-Response/ | |
| Type=TEAP | |
| {PKCS#10 TLV} | |
| --------------------> |
| | |
| | PKCS#10 |
| | ---------------->
| | |
| | PKCS#7 |
| | <----------------
| | |
| EAP-Request/ | |
| Type=TEAP, | |
| {PKCS#7 TLV, | |
| Result TLV=Success} | |
| <-------------------- |
| | |
| Eap-Response/ | |
| Type=TEAP | |
| {Result TLV=Success}| |
| --------------------> |
| | |
| EAP-Success | |
| <-------------------- |
,--+---. ,----+-----. ,+-.
|Client| |TEAPServer| |CA|
`------' `----------' `--'
Figure 3: Enrollment after BRSKI Flow
Notes:
(1) If the client has not yet completed the BRSKI flow, then it
provisionally accepts the server certificate and must validate it
later once BRSKI is complete. The server validates the client
certificate using its trust anchor database.
(2) The server instructs the client to start the BRSKI flow by
sending a Request-Action TLV that includes a BRSKI-RequestVoucher
TLV. The server also instructs the client to request trust anchors,
to request CSR Attrites, and to initiate a PKCS certificate
enrolment. As outlined in [RFC7170], the Request-Action TLV is sent
after the Crypto-Binding TLV and Result TLV exchange.
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(3) The client includes the certificate it received from the server
in the RequestVoucher message.
(4) Once the client receives and validates the voucher signed by the
MASA, it must verify the certificate it previously received from the
server.
(5) As outlined in [RFC7170], the Trusted-Server-Root TLV is
exchanged after the Crypto-Binding TLV exchange, and after the client
has used the Voucher to authenticate the TEAP server identity. This
is equivalent to section [todo] from
[I-D.ietf-anima-bootstrapping-keyinfra].
(6) There is no need for an additional Crypto-Binding TLV exchange as
there is no inner EAP method. All BRSKI exchanges are simply TLVs
exchanged inside the outer TLS tunnel.
7.3. TEAP Server Instructs Client to Reenroll
In this flow, the server instructs the client to reenroll and get a
new LDevID by exchanging TLVs once the outer TLS tunnel is
established.
,------. ,----------. ,--.
|Client| |TEAPServer| |CA|
`--+---' `----+-----' `+-'
| EAP-Request/ | |
| Identity | |
| <------------------------------ |
| | |
| EAP-Response/ | |
| Type=Identity | |
| ------------------------------> |
| | |
| EAP-Request/ | |
| Type=TEAP, | |
| TEAP Start, | |
| Authority-ID TLV | |
| <------------------------------ |
| | |
| EAP-Response/ | |
| Type=TEAP, | |
| TLS(ClientHello) | |
| ------------------------------> |
| | |
| EAP-Request/ | |
| Type=TEAP, | |
| TLS(ServerHello, | |
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| ServerKeyExchange, | |
| ServerHelloDone) | |
| <------------------------------ |
| | |
| EAP-Response/ | |
| Type=TEAP, | |
| ClientKeyExchange, | |
| CertificateVerify, | |
| ChangeCipherSpec, | |
| Finished) | |
| ------------------------------> |
| | |
| EAP-Request/ | |
| Type=TEAP, | |
| TLS(ChangeCipherSpec, | |
| Finished), | |
| {Crypto-Binding TLV, | |
| Result TLV=Success} | |
| <------------------------------ |
| | |
| EAP-Response/ | |
| Type=TEAP, | |
| {Crypto-Binding TLV, | |
| Result TLV=Success} | |
| ------------------------------> |
| | |
| EAP-Request/ | |
| Type=TEAP,{Request-Action TLV:| |
,---!. | Status=Failure, | |
|(1)|_\| Action=Process-TLV, | |
`-----'| TLV=PKCS#10} | |
| <------------------------------ |
| | |
| EAP-Response/ | |
| Type=TEAP | |
| {PKCS#10 TLV} | |
| ------------------------------> |
| | |
| | PKCS#10 |
| | ---------------->
| | |
| | PKCS#7 |
| | <----------------
| | |
| EAP-Request/ | |
| Type=TEAP, | |
| {PKCS#7 TLV, | |
| Result TLV=Success} | |
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| <------------------------------ |
| | |
| Eap-Response/ | |
| Type=TEAP | |
| {Result TLV=Success} | |
| ------------------------------> |
| | |
| EAP-Success | |
| <------------------------------ |
| | |
| EAP-Success | |
| <------------------------------ |
,--+---. ,----+-----. ,+-.
|Client| |TEAPServer| |CA|
`------' `----------' `--'
Figure 4: TEAP Server Instructs Client to Reenroll
(1) The server instructs the client to reenroll by sending a Request-
Action TLV that includes a PKCS#10 TLV.
7.4. Out of Band Reenroll
This section shows how the device does a reenroll to refresh its
LDEvID directly against the registrar outside the context of the TEAP
tunnel.
8. TEAP TLV Formats
8.1. New TLVs
This document defines 5 new TEAP TLVs. The following table indicates
whether the TLVs can be included in Request messages from TEAP server
to device, or Response messages from device to TEAP server.
+------------------------+----------+
| TLV | Message |
+------------------------+----------+
| BRSKI-VoucherRequest | Response |
| BRSKI-Voucher | Request |
| CSR-Attributes | Response |
| Retry-After | Response |
| NAI-Identity | Request |
+------------------------+----------+
These new TLVs are detailed in this section.
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8.1.1. BRSKI-RequestVoucher TLV
This TLV is used by the server as part of a Request-Action TLV to
request from the peer that it initiate a voucher request. When used
in this fashion, the length of this TLV will be set to zero. The
Status field of the Request-Action TLV MUST be set to Failure.
It is also used by the peer to initiate the voucher request. When
used in this fashion, the length of the TLV will be set to that of
the voucher request, as encoded and described in Section 3.3 in
[I-D.ietf-anima-bootstrapping-keyinfra].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV=TBD1-VoucherRequest | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The M and R bits are always expected to be set to 0.
The server is expected to forward the voucher request to the MASA,
and then return a voucher in a BRSKI-Voucher TLV as described below.
If it is unable to do so, it returns an TEAP Error TLV with one of
the defined errors or the following:
TBD2-MASA-Notavailable MASA unavailable
TBD3-MASA-Refused MASA refuses to sign the voucher
The peer terminates the TEAP connection, but may retry at some later
point. The backoff mechanism for such retries should be appropriate
for the device. Retries MUST occur no more frequently than once
every two (TBD) minutes.
8.1.2. BRSKI-Voucher TLV
This TLV is transmitted from the server to the peer. It contains a
signed voucher, as describe in [RFC8366].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV=TBD4-Voucher | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Upon receiving this TLV the peer will validate the signature of the
voucher, using its pre-installed manufacturer trust anchor (LDevID).
It MUST also validate the certificate used by the server to establish
the TLS connection.
If successful, it installs the new trust anchor contained in the
voucher.
Otherwise, the peer transmits an TEAP error TLV with one of the
following error messages:
TBD5-Invalid-Signature The signature on the voucher is invalid
TBD6-Invalid-Voucher The form or content of the voucher is invalid
TBD7-Invalid-TLS-Signer The certificate used for the TLS connection
could not be validated.
8.1.3. CSR-Attributes TLV
The server SHALL transmit this TLV to the peer, either along with the
BRSKI-Voucher TLV or at any time earlier in a communication. The
peer shall include attributes required by the server in any following
CSR. The value of this TLV is the base64 encoding described in
Section 4.5.2 of [RFC7030].
The TEAP server MAY use this TLV to specify the subject identity
information to include in Subject or Subjecet Alternate Name fields
in any following CSR.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV=TBD8-CSR-Attributes | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Again, the M and R values are set to 0. In the case where the client
is unable to provide the requested attributes, an TEAP-Error is
returned as follows:
TBD9-CSR-Attribute-Fail Unable to supply the requested attributes.
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8.1.4. Retry-After TLV
The server MUST transmit this TLV to the peer when repling to a
PKCS#10 TLV request from the peer where the server is willing to
fulfill the request and issue a certificate via a PKCS#7 response,
but is unable to fulfill the request immediately. This TLV is used
to tell the peer the mimimum lenght of time it MUST wait before
resending the PKCS#10 request. The value of this TLV is the time in
seconds that the peer MUST wait before resending the PKCS#10 request.
The peer MUST resend the exact same PKCS#10 request.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV=TBD10-Retry-After | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Again, the M and R values are set to 0.
8.1.5. NAI TLV
The server may use this TLV to provision a realm-specific NAI on the
device.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV=TBD10-NAI | length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Again, the M and R values are set to 0.
8.2. Existing TEAP TLV Specifications
This section documents allowed usage of existing TEAP TLVs. The
definition of the TLV is not changed, however clarifications on
allowed values for the TLV fields is documented.
8.2.1. PKCS#10 TLV
[RFC7170] defines the PKCS#10 TLV as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|R| TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PKCS#10 Data...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
[RFC7170] does not explicitly allow a Length value of zero.
A Length value of zero is allowed for this TLV when the TEAP server
sends a Request-Action TLV with a child PKCS#10 TLV to the client.
In this scenario, there is no PKCS#10 Data included in the TLV.
Clients MUST NOT send a zero length PKCS#10 TLV to the server.
8.3. TLV Rules
BRSKI TLVs can only be transported inside the TLS tunnel. The
following table provides a guide to which TLVs may be encapsulated in
which kind of packets, and in what quantity. The messages are as
follows: Request is a TEAP Request, Response is a TEAP Response,
Success is a message containing a successful Result TLV, and Failure
is a message containing a failed Result TLV.
The following define the meaning of the table entries in the sections
below:
0 This TLV MUST NOT be present in the message.
0+ Zero or more instances of this TLV MAY be present in the message.
0-1 Zero or one instance of this TLV MAY be present in the message.
1 Exactly one instance of this TLV MUST be present in the message.
Request Response Success Failure TLVs 0 0-1 0 0 BRSKI-VoucherRequest
0-1 0 0 0 BRSKI-Voucher 0 0-1 0 0 CSR-Attributes
9. Fragmentation
TEAP is expected to provide fragmentation support. Thus EAP-TEAP-
BRSKI does not specifically provide any, as it is only expected to be
used as an inner method to TEAP.
10. IANA Considerations
The IANA is requested to add entries into the following tables:
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The following new TEAP TLVs are defined:
TBD1-VoucherRequest Described in this document.
TBD4-Voucher Described in this document.
TBD8-CSR-Attributes Described in this document.
TBD10-Retry-After Described in this document.
The following TEAP Error Codes are defined, with their meanings
listed here and in previous sections:
TBD2-MASA-Notavailable MASA unavailable
TBD3-MASA-Refused MASA refuses to sign the voucher
TBD5-Invalid-Signature The signature on the voucher is invalid
TBD6-Invalid-Voucher The form or content of the voucher is invalid
TBD7-Invalid-TLS-Signer The certificate used for the TLS connection
could not be validated.
TBD9-CSR-Attribute-Fail Unable to supply the requested attributes.
TBD11-Retry-PKCS#10 Retry PKCS#10 Request (1000 range code)
TBD12-Retry-PKCS#10 Retry PKCS#10 Request (2000 range code)
TBD13-NAI-Rejected The device will not use the indicated
NAI (1000 range code)
[[ TODO: is there a registry of NAIs that map to TEAP methods? e.g.
@eap-teap.net is reserved to indicate the peer wants to use TEAP
method ]]
11. Security Considerations
BRSKI [I-D.ietf-anima-bootstrapping-keyinfra] provides a zero touch
way for devices to enroll in a certification authority (CA). It
assumes the device has IP connectivity. For networks that will not
grant IP connectivitiy before authenticating (with a local
credential) this poses a Catch-22- can't get on the network without a
credential and can't get a credential without getting on the network.
This protocol provides a way for BRSKI to be in an EAP method which
allows the BRSKI conversation to happen as part of EAP authentication
and prior to obtaining IP connectivity.
The security considerations of
[I-D.ietf-anima-bootstrapping-keyinfra] apply to this protocol.
Running BRSKI through EAP introduces some additional areas of concern
though.
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11.1. Issues with Provisionally Authenticated TEAP
This protocol establishes an unauthenticated TLS connection and
passes data through it. Provided that the only messages passed in
this state are self-protected BRSKI messages this does not present a
problem. Passing any other messages or TLVs prior to authentication
of the provisional TLS connection could potentially introduce
security issues.
While the TLS connection is unauthenticated, it must still be
validated to the fullest extent possible. It is critical that the
device and the TEAP server perform all steps in TLS- checking the
validity of the presented certificate, validating the signature using
the public key of the certificate, etc- except ensuring the trust of
the presented certificate.
11.2. Attack Against Discovery
The device discovery technique specified in this protocol is the
standard EAP server discovery process. Since it is trivial to set up
an 802.11 wireless access point and advertise any network, an
attacker can impersonate a legitimate wireless network and attract
unprovisioned pledges. Given that an unprovisioned device will not
know the legitimate network to connect to, it will probably attempt
the first network it finds, making the attack that much easier. This
allows for a "rogue registrar" to provision and take control of the
device.
If the MASA verifies ownership prior to issuance of a voucher, this
attack can be thwarted. But if the MASA is in reduced security mode
and does not verify ownership this attack cannot be prevented.
Registrars SHOULD use the audit log of a MASA when deploying newly
purchased equipment in order to mitigate this attack.
Another way to mitigate this attack is through normal "rogue AP"
detection and prevention.
11.3. TEAP Server as Registration Authority
If the TEAP server is logically separate from the Certification
Authority (CA) (see Section 2) it will be acting as a Registration
Authority (RA) when it obtains the PKCS#10 TLV and replies with a
PKCS#7 TLV (see [RFC7170], Sections 4.2.16 and 4.2.17, respectively).
The assurance a RA makes to a CA is that the public key in the
presented CSR is bound to an authenticated identity in way that will
assure non-repudiation.
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To make such an assurance, the TEAP server MUST authenticate the
provisional TLS connection with the device by validating the voucher
response received from the MASA. In addition, it is RECOMMENDED that
the TEAP server indicate that proof-of-possession (see [RFC7170],
Section 3.8.2) is required by including the challengePassword OID in
the CSR Attributes TLV.
11.4. Trust of Registrar
The device accepts a trusted server (CA) certificate and installs it
in its trust anchor database during step 5 (see Section 3.2). This
can happen only after the provisional TLS connection has been
authenticated using the voucher and the Crypto-Binding TLV has been
validated.
12. Acknowledgments
The authors would like to thank Brian Weis for his assistance, and
Alan Dakok for improving language consistency. In addition, with
ruthlessly "borrowed" the concept around NAI handling from Tuomas
Aura and Mohit Sethi.
13. References
13.1. Normative References
[I-D.ietf-anima-bootstrapping-keyinfra]
Pritikin, M., Richardson, M. C., Eckert, T., Behringer, M.
H., and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructure (BRSKI)", Work in Progress, Internet-Draft,
draft-ietf-anima-bootstrapping-keyinfra-45, 11 November
2020, <https://www.ietf.org/archive/id/draft-ietf-anima-
bootstrapping-keyinfra-45.txt>.
[IEEE8021AR]
Institute for Electrical and Electronics Engineers,
"Secure Device Identity", 1998.
[IEEE8021X]
Institute for Electrical and Electronics Engineers, "IEEE
Standard for Local and metropolitan area networks--Port-
Based Network Access Control", 2010.
[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/info/rfc3748>.
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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/info/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/info/rfc7170>.
[RFC8366] Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
"A Voucher Artifact for Bootstrapping Protocols",
RFC 8366, DOI 10.17487/RFC8366, May 2018,
<https://www.rfc-editor.org/info/rfc8366>.
13.2. Informative References
[RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542,
DOI 10.17487/RFC7542, May 2015,
<https://www.rfc-editor.org/info/rfc7542>.
Appendix A. Changes from Earlier Versions
Draft -06: * nothing more than version bump
Draft -03: * Merge EAP server and Registrar * Security considerations
* References improvements * Add Dan Harkins as co-author
Draft -02: * Flow corrections
Draft -01: * Add packet descriptions, IANA considerations, smooth out
language.
Draft -00:
* Initial revision
Authors' Addresses
Eliot Lear
Cisco Systems
Richtistrasse 7
CH-8304 Wallisellen
Switzerland
Phone: +41 44 878 9200
Email: lear@cisco.com
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Owen Friel
Cisco Systems
170 W. Tasman Dr.
San Jose, CA, 95134
United States
Email: ofriel@cisco.com
Nancy Cam-Winget
Cisco Systems
170 W. Tasman Dr.
San Jose, CA, 95134
United States
Email: ncamwing@cisco.com
Dan Harkins
HP Enterprise
3333 Scott Boulevard
Santa Clara, CA, 95054
United States
Email: dharkins@arubanetworks.com
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