Network Working Group O. Friel
Internet-Draft Cisco
Intended status: Standards Track R. Shekh-Yusef
Expires: April 25, 2020 Avaya
M. Richardson
Sandelman Software Works
October 23, 2019
BRSKI Cloud Registrar
draft-friel-anima-brski-cloud-01
Abstract
This document specifies the behaviour of a BRSKI Cloud Registrar, and
how a pledge can interact with a BRSKI Cloud Registrar when
bootstrapping.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Network Connectivity . . . . . . . . . . . . . . . . . . 4
3. Initial Voucher Request . . . . . . . . . . . . . . . . . . . 4
3.1. Cloud Registrar Discovery . . . . . . . . . . . . . . . . 4
3.2. Pledge - Cloud Registrar TLS Establishment Details . . . 4
3.3. Pledge Requests Voucher from the Cloud Registrar . . . . 5
4. Cloud Registrar Voucher Request Operation . . . . . . . . . . 5
4.1. Pledge Ownership Lookup . . . . . . . . . . . . . . . . . 5
5. Voucher Request Redirected to Local Domain Registrar . . . . 6
5.1. Pledge handling of Redirect . . . . . . . . . . . . . . . 6
6. Voucher Request Handled by Cloud Registrar . . . . . . . . . 6
7. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Voucher Request Redirected to Local Domain Registrar . . 7
7.2. Voucher Request Handled by Cloud Registrar . . . . . . . 8
7.2.1. Option 1: EST enroll completed against cloud
registrar . . . . . . . . . . . . . . . . . . . . . . 8
7.2.2. Option 2: EST redirect by cloud registrar . . . . . . 9
7.2.3. Option 3: Voucher includes EST domain . . . . . . . . 10
8. Pledge Certificate Identity Considerations . . . . . . . . . 11
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
10. Security Considerations . . . . . . . . . . . . . . . . . . . 12
11. Informative References . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
Bootstrapping Remote Secure Key Infrastructures (BRSKI)
[I-D.ietf-anima-bootstrapping-keyinfra] specifies automated
bootstrapping of an Autonomic Control Plane. BRSKI Section 2.7
describes how a pledge "MAY contact a well known URI of a cloud
registrar if a local registrar cannot be discovered or if the
pledge's target use cases do not include a local registrar".
This document further specifies use of a BRSKI cloud registrar and
clarifies operations that are not sufficiently specified in BRSKI.
Two high level deployment models are documented here:
o Local Domain Registrar Discovery: the cloud registrar is used by
the pledge to discover the local domain registrar. The cloud
registrar redirects the pledge to the local domain registrar, and
the pledge completes bootstrap against the local domain registrar.
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o Cloud Registrar Based Boostrap: there is no local domain registrar
and the pledge completes boostrap using the cloud registrar. As
part of boostrap, the cloud registrar may need to tell the client
the domain to use for accessing services.
These deployment models facilitate multiple use cases including:
o A pledge is bootstrapping in a remote location and needs to
contact a cloud registrar in order to discover its local domain.
o A pledge supports multiple deployment models and needs to discover
which deployment model is in use by the operator. For example, a
pledge may support connecting to a manufacturer cloud service or
an operator deployed service after bootstrapping is complete, and
needs to discover the deployment model in use by the pledge
operator. The discovery and bootstrap mechanism should be
consistent across both manufacturer cloud service and operator
deployed services.
2. Architecture
The high level architecture is illustrated in Figure 1. The pledge
connects to the cloud registrar during bootstrap. The cloud
registrar may redirect the pledge to a local registrar in order to
complete bootstrap against the local registrar. If the cloud
registrar handles the bootstrap process itself without redirecting
the pledge to a local registrar, the cloud registrar may need to
inform the pledge what domain to use for accessing services once
bootstrap is complete.
Finally, when bootstrapping against a local registrar, the registrar
may interact with a backend CA to assist in issuing certificates to
the pledge. The mechanisms and protocols by which the registrar
interacts with the CA are transparent to the pledge and are out-of-
scope of this document.
The architecture illustrates shows the cloud registrar and MASA as
being logically separate entities. The two functions could of course
be integrated into a single service.
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+--------+ +-----------+
| Pledge |---------------------------------------->| Cloud |
+--------+ | Registrar |
| +-----------+
|
| +-----------+ +-----------+
+---------------->| Local |--------------->| MASA |
| | Registrar | +-----------+
| +-----------+
| | +-----------+
| +--------------------->| CA |
| +-----------+
|
| +-----------+
+---------------->| Services |
+-----------+
Figure 1
2.1. Network Connectivity
The assumption is that the pledge already has network connectivity
prior to connecting to the cloud registrar. The pledge must have an
IP address, must be able to make DNBS queries, and must be able to
send HTTP requests to the cloud registrar. The pledge operator has
already connected the pledge to the network, and the mechanism by
which this has happened is out of scope of this document.
3. Initial Voucher Request
3.1. Cloud Registrar Discovery
BRSKI defines how a pledge MAY contact a well known URI of a cloud
registrar if a local registrar cannot be discovered. Additionally,
certain pledge types may never attempt to discover a local registrar
and may automatically bootstrap against a cloud registrar. The
details of the URI are manufacturer specific, with BRSKI giving the
example "brski-registrar.manufacturer.example.com".
3.2. Pledge - Cloud Registrar TLS Establishment Details
The pledge MUST use an Implicit Trust Anchor database (see [RFC7030])
to authenticate the cloud registrar service as described in
[RFC6125]. The pledge MUST NOT establish a provisional TLS
connection (see BRSKI section 5.1) with the cloud registrar.
The cloud registrar MUST validate the identity of the pledge by
sending a TLS CertificateRequest message to the pledge during TLS
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session establishment. The cloud registrar MAY include a
certificate_authorities field in the message to specify the set of
allowed IDevID issuing CAs that pledges may use when establishing
connections with the cloud registrar.
The cloud registrar MAY only allow connections from pledges that have
an IDevID that is signed by one of a specific set of CAs, e.g.
IDevIDs issued by certain manufacturers.
The cloud registrar MAY allow pledges to connect using self-signed
identity certificates or using Raw Public Key [RFC7250] certificates.
3.3. Pledge Requests Voucher from the Cloud Registrar
After the pledge has established a full TLS connection with the cloud
registrar and has verified the cloud registrar PKI identity, the
pledge generates a voucher request message as outlined in BRSKI
section 5.2, and sends the voucher request message to the cloud
registrar.
4. Cloud Registrar Voucher Request Operation
When the cloud registrar has verified the identity of the pledge,
determined the pledge ownership and has received the voucher request,
there are two main options for handling the request.
o the cloud registrar can redirect the voucher request to a local
domain registrar
o the cloud registrar can handle the voucher request directly by
either issuing a voucher or declining the request
4.1. Pledge Ownership Lookup
The cloud registrar needs some suitable mechanism for knowing the
correct owner of a connecting pledge based on the presented identity
certificate. For example, if the pledge establishes TLS using an
IDevID that is signed by a known manufacturing CA, the registrar
could extract the serial number from the IDevID and use this to
lookup a database of pledge IDevID serial numbers to owners.
Alternatively, if the cloud registrar allows pledges to connect using
self-signed certificates, the registrar could use the thumbprint of
the self-signed certificate to lookup a database of pledge self-
signed certificate thumbprints to owners.
The mechanism by which the cloud registrar determines pledge
ownership is out-of-scope of this document.
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5. Voucher Request Redirected to Local Domain Registrar
Once the cloud registar has determined pledge ownership, the cloud
registrar may redirect the pledge to the owner's local domain
registrar in order to complete bootstrap. Ownership registration
will require the owner to register their local domain. The mechanism
by which pledge owners register their domain with the cloud registrar
is out-of-scope of this document.
The cloud registrar replies to the voucher request with a suitable
HTTP 3xx response code as per [I-D.ietf-httpbis-bcp56bis], including
the owner's local domain in the HTTP Location header.
5.1. Pledge handling of Redirect
The pledge should complete BRSKI bootstrap as per standard BRSKI
operation after following the HTTP redirect. The pledge should
establish a provisional TLS connection with specified local domain
registrar. The pledge should not use its Implicit Trust Anchor
database for validating the local domain registrar identity. The
pledge should send a voucher request message via the local domain
registrar. When the pledge downloads a voucher, it can validate the
TLS connection to the local domain registrar and continue with
enrollment and bootstrap as per standard BRSKI operation.
6. Voucher Request Handled by Cloud Registrar
If the cloud registrar issues a voucher, it returns the voucher in a
HTTP response with a suitable 2xx response code as per
[I-D.ietf-httpbis-bcp56bis].
[[ TODO: it is TBD which of the following three options should be
used. Possibly 1 or 2 of them, maybe all 3. It is possible that
some options will be explicitly NOT recommended. There are standards
implications too as two of the options require including a DNS-ID in
a Voucher. ]]
There are a few options here:
o Option 1: the pledge completes EST enroll against the cloud
registrar. Once EST enrol is complete, we need a mechanism to
tell the pledge what its service domain is. This could be by
including a service domain in the voucher.
o Option 2: the pledge attempts EST enrol against the cloud
registrar and the cloud registrar responds with a 3xx redirecting
the pledge to the local domain RA in order to complete cert
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enrollment. The pledge assumes that services are off the local
domain. This does not require adding an FQDN to the voucher.
o Option 3: we enhance the voucher definition to include local RA
domain info, and the pledge implicitly knows that it if received a
voucher from the cloud registrar, and that voucher included a
local domain FQDN, the pledge knows to do EST enroll against the
local domain. i.e. it got a 200OK from the cloud registrar, and
knows to send the next HTTP request to the EST domain specified in
the voucher. The pledge assumes that services are off the local
domain specified in the voucher.
7. Protocol Details
[[ TODO ]] Missing detailed BRSKI steps e.g. CSR attributes,
logging, etc.
7.1. Voucher Request Redirected to Local Domain Registrar
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+--------+ +-----------+ +----------+
| Pledge | | Local | | Cloud RA |
| | | Registrar | | / MASA |
+--------+ +-----------+ +----------+
| |
| 1. Full TLS |
|<----------------------------------------------->|
| |
| 2. Voucher Request |
|------------------------------------------------>|
| |
| 3. 3xx Location: localra.example.com |
|<------------------------------------------------|
| |
| 4. Provisional TLS | |
|<-------------------->| |
| | |
| 5. Voucher Request | |
|--------------------->| 6. Voucher Request |
| |------------------------->|
| | |
| | 7. Voucher Response |
| |<-------------------------|
| 8. Voucher Response | |
|<---------------------| |
| | |
| 9. Validate TLS | |
|<-------------------->| |
| | |
| 10. etc. | |
|--------------------->| |
7.2. Voucher Request Handled by Cloud Registrar
[[ TODO: it is TBD which of the following three options should be
used. Possibly 1 or 2 of them, maybe all 3. It is possible that
some options will be explicitly NOT recommended. There are standards
implications too as two of the options require including a DNS-ID in
a Voucher. ]]
7.2.1. Option 1: EST enroll completed against cloud registrar
The Voucher includes the service domain to use after EST enroll is
complete.
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+--------+ +-----------+ +----------+
| Pledge | | Local | | Cloud RA |
| | | Service | | / MASA |
+--------+ +-----------+ +----------+
| |
| 1. Full TLS |
|<----------------------------------------------->|
| |
| 2. Voucher Request |
|------------------------------------------------>|
| |
| 3. Voucher Response {service:fqdn} |
|<------------------------------------------------|
| |
| 4. EST enroll |
|------------------------------------------------>|
| |
| 5. Certificate |
|<------------------------------------------------|
| |
| 6. Full TLS | |
|<-------------------->| |
| | |
| 7. Service Access | |
|--------------------->| |
7.2.2. Option 2: EST redirect by cloud registrar
As trust is already established via the Voucher, the pledge does a
full TLS handshake against the local RA.
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+--------+ +-----------+ +----------+
| Pledge | | Local | | Cloud RA |
| | | Registrar | | / MASA |
+--------+ +-----------+ +----------+
| |
| 1. Full TLS |
|<----------------------------------------------->|
| |
| 2. Voucher Request |
|------------------------------------------------>|
| |
| 3. Voucher Response |
|<------------------------------------------------|
| |
| 4. EST enroll |
|------------------------------------------------>|
| |
| 5. 3xx Location: localra.example.com |
|<------------------------------------------------|
| |
| 6. Full TLS | |
|<-------------------->| |
| | |
| 7. EST Enrol | |
|--------------------->| |
| | |
| 8. Certificate | |
|<---------------------| |
| | |
| 9. etc. | |
|--------------------->| |
7.2.3. Option 3: Voucher includes EST domain
The Voucher includes the EST domain to use for EST enroll. It is
assumed services are accessed at that domain too. As trust is
already established via the Voucher, the pledge does a full TLS
handshake against the local RA.
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+--------+ +-----------+ +----------+
| Pledge | | Local | | Cloud RA |
| | | Registrar | | / MASA |
+--------+ +-----------+ +----------+
| |
| 1. Full TLS |
|<----------------------------------------------->|
| |
| 2. Voucher Request |
|------------------------------------------------>|
| |
| 3. Voucher Response {localra:fqdn} |
|<------------------------------------------------|
| |
| 4. Full TLS | |
|<-------------------->| |
| | |
| 5. EST Enrol | |
|--------------------->| |
| | |
| 6. Certificate | |
|<---------------------| |
| | |
| 7. etc. | |
|--------------------->| |
8. Pledge Certificate Identity Considerations
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.
For example, the pledge may only be aware of its IDevID Subject which
includes a manufacturer serial number, but must include a specific
fully qualified domain name in the CSR in order to complete domain
ownership proofs required by the CA. As another example, the
registrar may deem the manufacturer serial number in an IDevID as
personally identifiable information, and may want to specify a new
random opaque identifier that the pledge should use in its CSR.
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9. IANA Considerations
[[ TODO ]]
10. Security Considerations
[[ TODO ]]
11. Informative References
[I-D.ietf-anima-bootstrapping-keyinfra]
Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
keyinfra-28 (work in progress), September 2019.
[I-D.ietf-httpbis-bcp56bis]
Nottingham, M., "Building Protocols with HTTP", draft-
ietf-httpbis-bcp56bis-08 (work in progress), November
2018.
[IEEE802.1AR]
IEEE, ., "Secure Device Identity", 2017.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <https://www.rfc-editor.org/info/rfc6125>.
[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>.
[RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
Weiler, S., and T. Kivinen, "Using Raw Public Keys in
Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
June 2014, <https://www.rfc-editor.org/info/rfc7250>.
Authors' Addresses
Owen Friel
Cisco
Email: ofriel@cisco.com
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Rifaat Shekh-Yusef
Avaya
Email: rifaat.ietf@gmail.com
Michael Richardson
Sandelman Software Works
Email: mcr+ietf@sandelman.ca
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