Network Working Group J. Peterson
Internet-Draft Neustar
Intended status: Informational October 30, 2017
Expires: May 3, 2018
ACME Challenges Using an Authority Token
draft-peterson-acme-authority-token-00.txt
Abstract
A number of proposed challenges for the Automated Certificate
Management Environment (ACME) effectively rely on an external
authority issuing a token according to a particular policy. This
document specifies a generic Authority Token challenge for ACME which
admits of subtypes for different identifiers or namespaces.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Challenges for an Authority Token . . . . . . . . . . . . . . 3
3.1. Token Type Requirements . . . . . . . . . . . . . . . . . 4
4. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. Informative References . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
ACME [I-D.ietf-acme-acme] is a mechanism for automating certificate
management on the Internet. It enables administrative entities to
prove effective control over resources like domain names, and
automtes the process of generating and issuing certificates.
In some cases, proving effective control over an identifier requires
an attestation from a third policy who has authority over the
resource, for example, an external policy administrator for a
namespace other than the DNS. In order to automate the process of
issuing certificates for those resources, this specification defines
a generic Authority Token challenge that ACME servers can issue in
order to acquire such a token. The challenge contains a type
indication that tells the client what sort of token it needs to
acquire. It is expected that the Authority Token challenge will be
usable for a variety of identifer types.
For example, the system of [I-D.ietf-acme-service-provider] provides
a mechanism that allows service providers to acquire certificates
corresponding to a Service Provider Code (SPC) as defined in
[I-D.ietf-stir-certificates] by consulting an external authority
responsible for those codes. Furthermore, Communications Service
Providers (CSPs) can delegate authority over numbers to their
customers, and those CSPs who support ACME can then help customers to
acquire certificates for those numbering resources with ACME. This
can permit number acquisition flows compatible with those shown in
[I-D.ietf-modern-problem-framework]. Another, similar example would
a mechanism that permits CSPs to delegate authority for particular
telephone numbers to customers, as described in
[I-D.ietf-acme-telephone].
This draft is a stub intended for discussing different approaches to
genericizing the token challenge methods under consideration.
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2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
described in [RFC2119].
3. Challenges for an Authority Token
Proving that a device on the Internet has effective control over a
non-Internet resource is not as straightforward as proving control
over an Internet resources like a DNS zone or a web page. Provided
that the issuer of identifiers, or someone acting on their behalf,
can implement a service that grants tokens to the people to whom it
has issued identifiers, however, a token could be used as a response
to an ACME challenge.
This challenge type requires a new "token-type" element, and may
optionally supply a "token-authority" designating a location where
tokens can be acquired. The set of "token-types" and the semantic
requirements for those tokens tracked by an IANA registry. Taking
the example of [I-D.ietf-acme-service-provider], a challenge might
look as follows:
HTTP/1.1 200 OK
Content-Type: application/json
Link: <https://example.com/acme/some-directory>;rel="directory"
{
"status": "pending",
"identifier": {
"type": "TNAuthList",
"value": ["1234-0111"]
},
"challenges": [
{
"type": "token-01",
"token-type": "TNAuthList-JWT",
"token-authority": "https://authority.example.org/authz",
"url": "https://boulder.example.com/authz/asdf/0"
"token": "IlirfxKKXAsHtmzK29Pj8A" }
],
}
Entities receiving this challenge know that they can as a proof
acquire a JWT token from the designated token authority. Once the
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JWT has been acquired, it can be posted back to the URL given by the
ACME challenge.
POST /acme/authz/asdf/0 HTTP/1.1
Host: boulder.example.com
Content-Type: application/jose+json
{
"protected": base64url({
"alg": "ES256",
"kid": "https://boulder.example.com/acme/reg/asdf",
"nonce": "Q_s3MWoqT05TrdkM2MTDcw",
"url": "https://boulder.example.com/acme/authz/asdf/0"
}),
"payload": base64url({
"TNAuthList-JWT": "evaGxfADs...62jcerQ"
}),
"signature": "5wUrDI3eAaV4wl2Rfj3aC0Pp--XB3t4YYuNgacv_D3U"
}
Because the assignment of resources can change over time,
demonstrations of effective control must be regularly refreshed --
though again, because of the diverse capabilities of the devices
involved, different schemes for refreshing the challenge, ones that
require less direct user supervision, may be available to some
devices and not others.
3.1. Token Type Requirements
[TBD.]
4. Acknowledgments
We would like to thank you for your contributions to this problem
statement and framework.
5. IANA Considerations
Future versions of this specification will include registrations for
the ACME Challenge type registries here. It will also create a
registry for "token types" as used in these challenges.
6. Security Considerations
TBD.
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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.
[I-D.ietf-acme-service-provider]
Barnes, M. and C. Wendt, "ACME Identifiers and Challenges
for VoIP Service Providers", draft-ietf-acme-service-
provider-01 (work in progress), July 2017.
[I-D.ietf-acme-star]
Sheffer, Y., Lopez, D., Dios, O., Pastor, A., and T.
Fossati, "Use of Short-Term, Automatically-Renewed (STAR)
Certificates to Delegate Authority over Web Sites", draft-
ietf-acme-star-00 (work in progress), June 2017.
[I-D.ietf-acme-telephone]
Peterson, J. and R. Barnes, "ACME Identifiers and
Challenges for Telephone Numbers", draft-ietf-acme-
telephone-00 (work in progress), July 2017.
[I-D.ietf-modern-problem-framework]
Peterson, J. and T. McGarry, "Modern Problem Statement,
Use Cases, and Framework", draft-ietf-modern-problem-
framework-03 (work in progress), July 2017.
[I-D.ietf-stir-certificates]
Peterson, J. and S. Turner, "Secure Telephone Identity
Credentials: Certificates", draft-ietf-stir-
certificates-14 (work in progress), May 2017.
[I-D.ietf-stir-passport]
Wendt, C. and J. Peterson, "Personal Assertion Token
(PASSporT)", draft-ietf-stir-passport-11 (work in
progress), February 2017.
[I-D.ietf-stir-rfc4474bis]
Peterson, J., Jennings, C., Rescorla, E., and C. Wendt,
"Authenticated Identity Management in the Session
Initiation Protocol (SIP)", draft-ietf-stir-rfc4474bis-16
(work in progress), February 2017.
[I-D.rescorla-stir-fallback]
Rescorla, E. and J. Peterson, "STIR Out of Band
Architecture and Use Cases", draft-rescorla-stir-
fallback-02 (work in progress), June 2017.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7340] Peterson, J., Schulzrinne, H., and H. Tschofenig, "Secure
Telephone Identity Problem Statement and Requirements",
RFC 7340, DOI 10.17487/RFC7340, September 2014,
<https://www.rfc-editor.org/info/rfc7340>.
Author's Address
Jon Peterson
Neustar, Inc.
1800 Sutter St Suite 570
Concord, CA 94520
US
Email: jon.peterson@neustar.biz
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