Internet DRAFT - draft-friel-pki-for-devices
draft-friel-pki-for-devices
Network Working Group O. Friel
Internet-Draft R. Barnes
Intended status: Standards Track Cisco
Expires: May 3, 2018 October 30, 2017
PKI Certificate Identifier Format for Devices
draft-friel-pki-for-devices-00
Abstract
This document defines a standard Subject field identifier format for
certificates issued to Internet of Things (IoT) devices. This will
allow applications to easily and uniquely identify certificates
issued to devices as opposed to certificates issue to services or
users. The certificates will adhere to standard Web PKI
specifications thus ensuring interoperability with existing
Certificate Authorities processes and workflows, and standard client
and service libraries and applications.
Status of This Memo
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This Internet-Draft will expire on May 3, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Manufacturing vs. Deploy Time Certificates . . . . . . . . . 3
3. Device Information Domain Name . . . . . . . . . . . . . . . 3
3.1. IDevID Certificates . . . . . . . . . . . . . . . . . . . 3
3.2. LDevID Certificates . . . . . . . . . . . . . . . . . . . 4
4. Certificate Fields . . . . . . . . . . . . . . . . . . . . . 5
4.1. Subject . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. Subject Alternate Name . . . . . . . . . . . . . . . . . 5
4.3. Extended Key Usage . . . . . . . . . . . . . . . . . . . 5
4.4. Certificate Lifetime . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. Informative References . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
There is an increasing need for devices to be able to uniquely
identify themselves and assert their identity, and associated
identity attributes, using standard Web PKI techniques. In order to
faclitate issuing certificates to devices, this document defines a
mechanism for uniquely identifying devices using a structured Subject
field identifier that should be supported by all major Certificate
Authorities (CAs), including those CAs that support
[I-D.ietf-acme-acme].
The use of Web PKI for the purpose of issuing device certificates has
multiple benefits including:
o Existing code, processes, and policies for managing Web PKI
certificates can be re-used
o Device certificates can be trusted by web browsers
o For small-scale device manufacturers, it is possible to use
existing CAs to issue device certificates of this kind
o For more mature manufacturers, the use of structured DNS names to
encode device information means that name-constrained intermediate
CAs can be used to allow the manufacturer to issue device
certificates independently of the root CA.
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Previous attempts to uniquely identify device certificates have not
proven to be broadly supported by common certificate management
software libraries. These include:
o [IEEE802.1AR] which defines a serialNumber field
o [RFC4108] which defines a hardwareModuleName field
2. Manufacturing vs. Deploy Time Certificates
Devices will typically have a unique certificate that is baked into
the device at manufacturing time i.e. the device will leave the
factory with a unique manufacturer installed certificate already
baked in. This certificate will typically be signed by a CA that the
manufacturer controls, or a CA that the manufacturer explicitly
authorizes. This CA does not necessarily have be a public root CA
that is trusted by web browsers. This certificate is referred to as
the Initial Device Identifier (IDevID).
A common deployment requirement is that the end customer that
purchases and deploys the device in their local domain will need to
install a certificate on the device that is signed by a CA under
their control, or signed by a CA of their choosing. This certificate
is referred to as the Locally Significant Device Identifier (LDevID).
3. Device Information Domain Name
A unique device identifier is encoded in a structured Device
Information Domain Name Identifier (DIDN-ID) of the following form:
<serial>.<model>.keyword.<domain>
where "keyword" MUST be one of:
_mDevice
_device
The fields "serial", "model" and "domain" are described in the
following sections.
3.1. IDevID Certificates
IDevID certificates have the following form:
<serial>.<model>._mDevice.<manufacturer>
Where:
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o "manufacturer" is a fully-qualified domain name identifying the
manufacturer of the device
o "_mDevice" is a mandatory keyword that indicates this is an IDevID
installed at manufacturing time
o "model" is a manufacturer-chosen string that MUST identify the
model or type of the device
o "serial" is a manufacturer-chosen string that MUST identify the
specific serial number of this model
The combination of "manufacturer", "model", and "serial" MUST
uniquely identify the device.
3.2. LDevID Certificates
If the LDevID is issued by a public trusted CA, then the LDevID
idenfitier format MUST follow the identifier format specified in this
section.
Where the LDevIDs are issued by private domain CAs that do not
necessarily need to adhere to CA/Browser forum guidelines, it is
strongly recommended that the private CA follows this identifier
format specification.
LDevID certificates have the following form:
<serial>.<type>._device.<deployment-domain>
Where:
o "deployment-domain" is a fully-qualified domain name identifying
the local domain where the device is installed. This will
typically be a domain that the purchaser or owner of the device
can assert ownership of
o "_device" is a mandatory keyword that indicates this is an LDevID
installed during live deployment
o "model" this SHOULD be copied from the IDevID of the device
o "serial" this SHOULD be copied from the IDevID of the device
The combination of "manufacturer", "model", and "serial" SHOULD
uniquely identify the device.
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If the customer who owns the device uses a public CA to issue the
LDevID, and if the device "serial" number and/or "model" is
considered sensitive or Personally Identifiable Information (PII),
then the "serial" and "model" fields MAY be replaced with suitable
alternate identifiers. However, the public CA MUST ensure that the
format and structure of the DIDN-ID adheres to this specification.
4. Certificate Fields
4.1. Subject
Following the recommendations set out in [RFC6125], the Subject field
of the certificate MAY contain the "commonName" field, set to the
DIDN-ID for the device.
The Subject field MAY also contain a "serialNumber" or
"hardwareModuleName" field.
4.2. Subject Alternate Name
The certificate MUST contain a "subjectAltName" extension
contataining a single "dnsName" entry with the DIDN-ID for the
device.
4.3. Extended Key Usage
The certificate MUST contain an "extKeyUsage" extension with the
values "id-kp-serverAuth" and "id-kp-clientAuth", and no other
values.
4.4. Certificate Lifetime
IDevID certificates with "_mDevice" identifiers in their DIDN-ID MUST
have a "notAfter" value of 99991231235959Z (i.e. Y10K).
It should be noted that at the time of writing, web browsers do not
check for Y10K and will happily establish connections with endpoints
whose identity certificate has a "notAfter" value of Y10K.
LDevID certificates are issued during live deployment and MUST follow
the standard lifetime and expiration requirements of the issuing CA.
5. IANA Considerations
[[ TODO: Register the "_device" and "_mDevice" labels ]]
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6. Security Considerations
[[ TODO ]]
7. Informative References
[I-D.ietf-acme-acme]
Barnes, R., Hoffman-Andrews, J., and J. Kasten, "Automatic
Certificate Management Environment (ACME)", draft-ietf-
acme-acme-07 (work in progress), June 2017.
[IEEE802.1AR]
IEEE, ., "Secure Device Identity", 2017.
[RFC4108] Housley, R., "Using Cryptographic Message Syntax (CMS) to
Protect Firmware Packages", RFC 4108,
DOI 10.17487/RFC4108, August 2005,
<https://www.rfc-editor.org/info/rfc4108>.
[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>.
Authors' Addresses
Owen Friel
Cisco
Email: ofriel@cisco.com
Richard Barnes
Cisco
Email: rlb@ipv.sx
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