Automated Certificate Management Environment (ACME) Renewal Information (ARI) Extension
draft-aaron-acme-ari-00
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
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|
|---|---|---|---|
| Author | Aaron Gable | ||
| Last updated | 2021-09-22 | ||
| Replaced by | draft-ietf-acme-ari | ||
| RFC stream | (None) | ||
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| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
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draft-aaron-acme-ari-00
ACME Working Group A. Gable
Internet-Draft Internet Security Research Group
Intended status: Standards Track 22 September 2021
Expires: 26 March 2022
Automated Certificate Management Environment (ACME) Renewal Information
(ARI) Extension
draft-aaron-acme-ari-00
Abstract
This document specifies how an ACME server may provide hints to ACME
clients as to when they should attempt to renew their certificates.
This allows servers to mitigate load spikes, and ensures clients do
not make false assumptions about appropriate certificate renewal
periods.
Discussion Venues
This note is to be removed before publishing as an RFC.
Discussion of this document takes place on the Automated Certificate
Management Environment Working Group mailing list (acme@ietf.org),
which is archived at https://mailarchive.ietf.org/arch/browse/acme/.
Source for this draft and an issue tracker can be found at
https://github.com/aarongable/draft-acme-ari.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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 March 2022.
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Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3
3. Extensions to the ACME Protocol: The "order" Resource . . . . 3
4. Extensions to the ACME Protocol: The "renewalInfo"
Resource . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6.1. New Registries . . . . . . . . . . . . . . . . . . . . . 5
6.2. ACME Resource Type . . . . . . . . . . . . . . . . . . . 5
6.3. ACME Order Object Fields . . . . . . . . . . . . . . . . 5
6.4. ACME Renewal Info Object Fields . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . 6
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Most ACME clients today choose when to attempt to renew a certificate
in one of three ways. They may be configured to renew at a specific
interval (e.g. via "cron"); they may parse the issued certificate to
determine its expiration date and renew a specific amount of time
before then; or they may parse the issued certificate and renew when
some percentage of its validity period has passed. The first two
techniques create significant barriers against the issuing CA
changing certificate lifetimes. All three techniques lead to load
clustering for the issuing CA.
Being able to indicate to the client a period in which the issuing CA
suggests renewal would allow both dynamic changes to the certificate
validity period and proactive smearing of load. This document
specifies a mechanism by which ACME servers may provide suggested
renewal windows to ACME clients.
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2. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Extensions to the ACME Protocol: The "order" Resource
An ACME server which wishes to provide renewal information MUST
include a new field, "renewalInfo", in finalized Order objects.
renewalInfo (optional, string): A URL for renewal information for the
certificate that has been issued in response to this order.
HTTP/1.1 200 OK
Content-Type: application/json
{
"status": "valid",
"expires": "2021-01-20T14:09:07.99Z",
"identifiers": [
{ "type": "dns", "value": "www.example.org" },
{ "type": "dns", "value": "example.org" }
],
"notBefore": "2021-01-01T00:00:00Z",
"notAfter": "2021-01-08T00:00:00Z",
"authorizations": [
"https://example.com/acme/authz/PAniVnsZcis",
"https://example.com/acme/authz/r4HqLzrSrpI"
],
"finalize": "https://example.com/acme/order/TOlocE8rfgo/finalize",
"certificate": "https://example.com/acme/cert/mAt3xBGaobw",
"renewalInfo": "https://example.com/acme/renewal/eXoM9UwLgbL"
}
Conforming clients SHOULD store the "renewalInfo" URL locally so that
they can poll it at any time during the lifetime of the certificate.
4. Extensions to the ACME Protocol: The "renewalInfo" Resource
We define a new resource type, the "renewalInfo" resource, as part of
the ACME protocol.
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The structure of an ACME renewalInfo resource is as follows:
suggestedWindow (object, required): A JSON object with two keys,
"start" and "end", whose values are timestamps, encoded in the format
specified in [RFC3339], which bound the window of time in which the
CA recommends renewing the certificate.
HTTP/1.1 200 OK
Content-Type: application/json
{
"suggestedWindow": {
"start": "2021-01-03T00:00:00Z",
"end": "2021-01-07T00:00:00Z"
}
}
Conforming servers MUST provide the renewalInfo resource via POST-as-
GET; they SHOULD provide it via unauthenticated GET as well.
Conforming clients SHOULD use unauthenticated GET to request
renewalInfo resources.
The server SHOULD include a Retry-After header indicating the polling
interval that the ACME server recommends. Conforming clients SHOULD
query the "renewalInfo" URL again after the Retry-After period has
passed, as the server may provide a different suggestedWindow.
Conforming clients SHOULD select a random time within the suggested
window to attempt to renew the certificate. If the selected time is
in the past, the client SHOULD attempt renewal immediately.
5. Security Considerations
The extensions to the ACME protocol described in this document build
upon the Security Considerations and threat model defined in
Section 10.1 of [RFC8555].
This document specifies that renewalInfo resources should be exposed
via unauthenticated GET requests, a departure from RFC8555's
requirement that clients must send POST-as-GET requests to fetch
resources from the server. This is because the information contained
in renewalInfo resources is not considered confidential, and because
allowing renewalInfo to be easily cached is advantageous to shed load
from clients which do not respect the Retry-After header.
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6. IANA Considerations
Draft note: The following changes to IANA registries have not yet
been made.
6.1. New Registries
Within the "Automated Certificate Management Environment (ACME)
Protocol" registry, IANA has created the new "ACME Renewal Info
Object Fields" registry (Section 6.4).
6.2. ACME Resource Type
Within the "Automated Certificate Management Environment (ACME)
Protocol" registry, the following entry has been added to the "ACME
Resource Types" registry.
+=============+=====================+============+
| Field Name | Resource Type | Reference |
+=============+=====================+============+
| renewalInfo | Renewal Info object | This draft |
+-------------+---------------------+------------+
Table 1
6.3. ACME Order Object Fields
Within the "Automated Certificate Management Environment (ACME)
Protocol" registry, the following entry has been added to the "ACME
Order Object Fields" registry.
+=============+============+==============+============+
| Field Name | Field Type | Configurable | Reference |
+=============+============+==============+============+
| renewalInfo | string | false | This draft |
+-------------+------------+--------------+------------+
Table 2
6.4. ACME Renewal Info Object Fields
The "ACME Renewal Info Object Fields" registry lists field names that
are defined for use in ACME renewal info objects.
Template:
* Field name: The string to be used as a field name in the JSON
object
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* Field type: The type of value to be provided, e.g., string,
boolean, array of string
* Reference: Where this field is defined
Initial contents:
+=================+============+============+
| Field Name | Field type | Reference |
+=================+============+============+
| suggestedWindow | object | This draft |
+-----------------+------------+------------+
Table 3
7. Normative References
[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>.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<https://www.rfc-editor.org/info/rfc3339>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8555] Barnes, R., Hoffman-Andrews, J., McCarney, D., and J.
Kasten, "Automatic Certificate Management Environment
(ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019,
<https://www.rfc-editor.org/info/rfc8555>.
Acknowledgments
TODO acknowledge.
Author's Address
A. Gable
Internet Security Research Group
Email: aaron@letsencrypt.org
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