draft-ietf-acme-star-08.txt   draft-ietf-acme-star-09.txt 
ACME Working Group Y. Sheffer ACME Working Group Y. Sheffer
Internet-Draft Intuit Internet-Draft Intuit
Intended status: Standards Track D. Lopez Intended status: Standards Track D. Lopez
Expires: February 29, 2020 O. Gonzalez de Dios Expires: March 20, 2020 O. Gonzalez de Dios
A. Pastor Perales A. Pastor Perales
Telefonica I+D Telefonica I+D
T. Fossati T. Fossati
ARM ARM
August 28, 2019 September 17, 2019
Support for Short-Term, Automatically-Renewed (STAR) Certificates in Support for Short-Term, Automatically-Renewed (STAR) Certificates in
Automated Certificate Management Environment (ACME) Automated Certificate Management Environment (ACME)
draft-ietf-acme-star-08 draft-ietf-acme-star-09
Abstract Abstract
Public-key certificates need to be revoked when they are compromised, Public-key certificates need to be revoked when they are compromised,
that is, when the associated private key is exposed to an that is, when the associated private key is exposed to an
unauthorized entity. However the revocation process is often unauthorized entity. However the revocation process is often
unreliable. An alternative to revocation is issuing a sequence of unreliable. An alternative to revocation is issuing a sequence of
certificates, each with a short validity period, and terminating this certificates, each with a short validity period, and terminating this
sequence upon compromise. This memo proposes an ACME extension to sequence upon compromise. This memo proposes an ACME extension to
enable the issuance of short-term and automatically renewed (STAR) enable the issuance of short-term and automatically renewed (STAR)
skipping to change at page 1, line 48 skipping to change at page 1, line 48
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 29, 2020. This Internet-Draft will expire on March 20, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1.1. Name Delegation Use Case . . . . . . . . . . . . . . . . 4 1.1. Name Delegation Use Case . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Conventions used in this document . . . . . . . . . . . . 4 1.3. Conventions used in this document . . . . . . . . . . . . 4
2. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Bootstrap . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Bootstrap . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Refresh . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Refresh . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Termination . . . . . . . . . . . . . . . . . . . . . . . 6 2.3. Termination . . . . . . . . . . . . . . . . . . . . . . . 6
3. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 7 3. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 7
3.1. ACME Extensions . . . . . . . . . . . . . . . . . . . . . 7 3.1. ACME Extensions . . . . . . . . . . . . . . . . . . . . . 7
3.1.1. Extending the Order Resource . . . . . . . . . . . . 7 3.1.1. Extending the Order Resource . . . . . . . . . . . . 7
3.1.2. Canceling a Recurrent Order . . . . . . . . . . . . . 8 3.1.2. Canceling an Auto-renewal Order . . . . . . . . . . . 8
3.2. Capability Discovery . . . . . . . . . . . . . . . . . . 9 3.2. Capability Discovery . . . . . . . . . . . . . . . . . . 9
3.3. Fetching the Certificates . . . . . . . . . . . . . . . . 10 3.3. Fetching the Certificates . . . . . . . . . . . . . . . . 10
3.4. Negotiating an unauthenticated GET . . . . . . . . . . . 12 3.4. Negotiating an unauthenticated GET . . . . . . . . . . . 12
3.5. Computing notBefore and notAfter of STAR Certificates . . 13 3.5. Computing notBefore and notAfter of STAR Certificates . . 13
3.5.1. Example . . . . . . . . . . . . . . . . . . . . . . . 13 3.5.1. Example . . . . . . . . . . . . . . . . . . . . . . . 14
4. Operational Considerations . . . . . . . . . . . . . . . . . 14 4. Operational Considerations . . . . . . . . . . . . . . . . . 14
4.1. The Meaning of "Short Term" and the Impact of Skewed 4.1. The Meaning of "Short Term" and the Impact of Skewed
Clocks . . . . . . . . . . . . . . . . . . . . . . . . . 14 Clocks . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.2. Impact on Certificate Transparency (CT) Logs . . . . . . 15 4.2. Impact on Certificate Transparency (CT) Logs . . . . . . 15
4.3. Dependability . . . . . . . . . . . . . . . . . . . . . . 15 4.3. HTTP Caching and Dependability . . . . . . . . . . . . . 15
5. Implementation Status . . . . . . . . . . . . . . . . . . . . 16 5. Implementation Status . . . . . . . . . . . . . . . . . . . . 16
5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 16 5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 16
5.1.1. ACME Server with STAR extension . . . . . . . . . . . 16 5.1.1. ACME Server with STAR extension . . . . . . . . . . . 17
5.1.2. STAR Proxy . . . . . . . . . . . . . . . . . . . . . 17 5.1.2. STAR Proxy . . . . . . . . . . . . . . . . . . . . . 17
5.2. Level of Maturity . . . . . . . . . . . . . . . . . . . . 17 5.2. Level of Maturity . . . . . . . . . . . . . . . . . . . . 17
5.3. Coverage . . . . . . . . . . . . . . . . . . . . . . . . 17 5.3. Coverage . . . . . . . . . . . . . . . . . . . . . . . . 17
5.4. Version Compatibility . . . . . . . . . . . . . . . . . . 17 5.4. Version Compatibility . . . . . . . . . . . . . . . . . . 18
5.5. Licensing . . . . . . . . . . . . . . . . . . . . . . . . 17 5.5. Licensing . . . . . . . . . . . . . . . . . . . . . . . . 18
5.6. Implementation experience . . . . . . . . . . . . . . . . 18 5.6. Implementation experience . . . . . . . . . . . . . . . . 18
5.7. Contact Information . . . . . . . . . . . . . . . . . . . 18 5.7. Contact Information . . . . . . . . . . . . . . . . . . . 18
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
6.1. New Error Types . . . . . . . . . . . . . . . . . . . . . 18 6.1. New Registries . . . . . . . . . . . . . . . . . . . . . 18
6.2. New fields in Order Objects . . . . . . . . . . . . . . . 19 6.2. New Error Types . . . . . . . . . . . . . . . . . . . . . 19
6.3. New fields in the "meta" Object within a Directory Object 20 6.3. New fields in Order Objects . . . . . . . . . . . . . . . 19
6.4. Cert-Not-Before and Cert-Not-After HTTP Headers . . . . . 20 6.4. Fields in the "auto-renewal" Object within an Order
7. Security Considerations . . . . . . . . . . . . . . . . . . . 20 Object . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.1. No revocation . . . . . . . . . . . . . . . . . . . . . . 20 6.5. New fields in the "meta" Object within a Directory Object 20
7.2. Denial of Service Considerations . . . . . . . . . . . . 21 6.6. Fields in the "auto-renewal" Object within a Directory
7.3. Privacy Considerations . . . . . . . . . . . . . . . . . 21 Metadata Object . . . . . . . . . . . . . . . . . . . . . 20
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21 6.7. Cert-Not-Before and Cert-Not-After HTTP Headers . . . . . 21
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 7. Security Considerations . . . . . . . . . . . . . . . . . . . 21
9.1. Normative References . . . . . . . . . . . . . . . . . . 22 7.1. No revocation . . . . . . . . . . . . . . . . . . . . . . 21
9.2. Informative References . . . . . . . . . . . . . . . . . 22 7.2. Denial of Service Considerations . . . . . . . . . . . . 22
Appendix A. Document History . . . . . . . . . . . . . . . . . . 24 7.3. Privacy Considerations . . . . . . . . . . . . . . . . . 22
A.1. draft-ietf-acme-star-08 . . . . . . . . . . . . . . . . . 24 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22
A.2. draft-ietf-acme-star-07 . . . . . . . . . . . . . . . . . 24 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
A.3. draft-ietf-acme-star-06 . . . . . . . . . . . . . . . . . 24 9.1. Normative References . . . . . . . . . . . . . . . . . . 23
A.4. draft-ietf-acme-star-05 . . . . . . . . . . . . . . . . . 24 9.2. Informative References . . . . . . . . . . . . . . . . . 23
A.5. draft-ietf-acme-star-04 . . . . . . . . . . . . . . . . . 24 Appendix A. Document History . . . . . . . . . . . . . . . . . . 25
A.6. draft-ietf-acme-star-03 . . . . . . . . . . . . . . . . . 24 A.1. draft-ietf-acme-star-09 . . . . . . . . . . . . . . . . . 25
A.7. draft-ietf-acme-star-02 . . . . . . . . . . . . . . . . . 24 A.2. draft-ietf-acme-star-08 . . . . . . . . . . . . . . . . . 25
A.8. draft-ietf-acme-star-01 . . . . . . . . . . . . . . . . . 25 A.3. draft-ietf-acme-star-07 . . . . . . . . . . . . . . . . . 25
A.9. draft-ietf-acme-star-00 . . . . . . . . . . . . . . . . . 25 A.4. draft-ietf-acme-star-06 . . . . . . . . . . . . . . . . . 25
A.10. draft-sheffer-acme-star-02 . . . . . . . . . . . . . . . 25 A.5. draft-ietf-acme-star-05 . . . . . . . . . . . . . . . . . 25
A.11. draft-sheffer-acme-star-01 . . . . . . . . . . . . . . . 25 A.6. draft-ietf-acme-star-04 . . . . . . . . . . . . . . . . . 25
A.12. draft-sheffer-acme-star-00 . . . . . . . . . . . . . . . 25 A.7. draft-ietf-acme-star-03 . . . . . . . . . . . . . . . . . 26
A.13. draft-sheffer-acme-star-lurk-00 . . . . . . . . . . . . . 25 A.8. draft-ietf-acme-star-02 . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 A.9. draft-ietf-acme-star-01 . . . . . . . . . . . . . . . . . 26
A.10. draft-ietf-acme-star-00 . . . . . . . . . . . . . . . . . 26
A.11. draft-sheffer-acme-star-02 . . . . . . . . . . . . . . . 26
A.12. draft-sheffer-acme-star-01 . . . . . . . . . . . . . . . 26
A.13. draft-sheffer-acme-star-00 . . . . . . . . . . . . . . . 26
A.14. draft-sheffer-acme-star-lurk-00 . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction 1. Introduction
The ACME protocol [RFC8555] automates the process of issuing a The ACME protocol [RFC8555] automates the process of issuing a
certificate to a named entity (an Identifier Owner or IdO). certificate to a named entity (an Identifier Owner or IdO).
Typically, but not always, the identifier is a domain name. Typically, but not always, the identifier is a domain name.
If the IdO wishes to obtain a string of short-term certificates If the IdO wishes to obtain a string of short-term certificates
originating from the same private key (see [Topalovic] about why originating from the same private key (see [Topalovic] about why
using short-lived certificates might be preferable to explicit using short-lived certificates might be preferable to explicit
revocation), she must go through the whole ACME protocol each time a revocation), she must go through the whole ACME protocol each time a
new short-term certificate is needed - e.g., every 2-3 days. If done new short-term certificate is needed - e.g., every 2-3 days. If done
this way, the process would involve frequent interactions between the this way, the process would involve frequent interactions between the
registration function of the ACME Certification Authority (CA) and registration function of the ACME Certification Authority (CA) and
the identity provider infrastructure (e.g.: DNS, web servers), the identity provider infrastructure (e.g.: DNS, web servers),
therefore making the issuance of short-term certificates exceedingly therefore making the issuance of short-term certificates exceedingly
dependent on the reliability of both. dependent on the reliability of both.
This document presents an extension of the ACME protocol that This document presents an extension of the ACME protocol that
optimizes this process by making short-term certificates first class optimizes this process by making short-term certificates first class
objects in the ACME ecosystem. Once the order for a string of short- objects in the ACME ecosystem. Once the Order for a string of short-
term certificates is accepted, the CA is responsible for publishing term certificates is accepted, the CA is responsible for publishing
the next certificate at an agreed upon URL before the previous one the next certificate at an agreed upon URL before the previous one
expires. The IdO can terminate the automatic renewal before the expires. The IdO can terminate the automatic renewal before the
negotiated deadline, if needed - e.g., on key compromise. negotiated deadline, if needed - e.g., on key compromise.
For a more generic treatment of STAR certificates, readers are For a more generic treatment of STAR certificates, readers are
referred to [I-D.nir-saag-star]. referred to [I-D.nir-saag-star].
1.1. Name Delegation Use Case 1.1. Name Delegation Use Case
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| | | End auto renewal | | | End auto renewal
| | | Remove cert link | | | Remove cert link
| | | etc. | | | etc.
| | | | | | | |
| | Done |<------' | | Done |<------'
| |<----------------------+ | |<----------------------+
| | | | | |
| | | |
| Retrieve cert | | Retrieve cert |
+---------------------------------------------->| +---------------------------------------------->|
| Error: recurrentOrderCanceled | | Error: autoRenewalCanceled |
|<----------------------------------------------+ |<----------------------------------------------+
| | | |
Figure 2: Termination Figure 2: Termination
3. Protocol Details 3. Protocol Details
This section describes the protocol details, namely the extensions to This section describes the protocol details, namely the extensions to
the ACME protocol required to issue STAR certificates. the ACME protocol required to issue STAR certificates.
3.1. ACME Extensions 3.1. ACME Extensions
This protocol extends the ACME protocol, to allow for recurrent This protocol extends the ACME protocol, to allow for automatically
Orders. renewed Orders.
3.1.1. Extending the Order Resource 3.1.1. Extending the Order Resource
The Order resource is extended with the following attributes: The Order resource is extended with a new "auto-renewal" object that
MUST be present for STAR certificates. The "auto-renewal" object has
the following structure:
o recurrent (required, boolean): MUST be true for STAR certificates. o start-date (optional, string): the earliest date of validity of
o recurrent-start-date (optional, string): the earliest date of the first certificate issued, in [RFC3339] format. When omitted,
validity of the first certificate issued, in [RFC3339] format. the start date is as soon as authorization is complete.
When omitted, the start date is as soon as authorization is o end-date (required, string): the latest date of validity of the
complete. last certificate issued, in [RFC3339] format.
o recurrent-end-date (required, string): the latest date of validity o lifetime (required, integer): the maximum validity period of each
of the last certificate issued, in [RFC3339] format. STAR certificate, an integer that denotes a number of seconds.
o recurrent-certificate-validity (required, integer): the maximum This is a nominal value which does not include any extra validity
validity period of each STAR certificate, an integer that denotes time due to server or client adjustment (see below).
a number of seconds. This is a nominal value which does not
include any extra validity time which is due to pre-dating. The o lifetime-adjust (optional, integer): amount of "left pad" added to
client can use the value reflected by the server (which may be each STAR certificate, an integer that denotes a number of
different from the one sent by the client) as a hint to configure seconds. The default is 0. If present, the value of the
its polling timer. notBefore field that would otherwise appear in the STAR
o recurrent-certificate-predate (optional, integer): amount of pre-
dating added to each STAR certificate, an integer that denotes a
number of seconds. The default is 0. If present, the value of
the notBefore field that would otherwise appear in the STAR
certificates is pre-dated by the specified number of seconds. See certificates is pre-dated by the specified number of seconds. See
also Section 4.1. also Section 4.1 for why a client might want to use this control
o recurrent-certificate-get (optional, boolean): see Section 3.4. and Section 3.5 for how the effective certificate lifetime is
computed. The value reflected by the server, together with the
value of the lifetime attribute, can be used by the client as a
hint to configure its polling timer.
o allow-certificate-get (optional, boolean): see Section 3.4.
These attributes are included in a POST message when creating the These attributes are included in a POST message when creating the
Order, as part of the "payload" encoded object. They are returned Order, as part of the "payload" encoded object. They are returned
when the Order has been created, and the ACME server MAY adjust them when the Order has been created, and the ACME server MAY adjust them
at will, according to its local policy (see also Section 3.2). at will, according to its local policy (see also Section 3.2).
The optional notBefore and notAfter fields defined in Section 7.1.3 The optional notBefore and notAfter fields defined in Section 7.1.3
of [RFC8555] MUST NOT be present in a STAR Order. If they are of [RFC8555] MUST NOT be present in a STAR Order. If they are
included, the server MUST return an error with status code 400 "Bad included, the server MUST return an error with status code 400 "Bad
Request" and type "malformedRequest". Request" and type "malformedRequest".
Section 7.1.6 of [RFC8555] defines the following values for the Order Section 7.1.6 of [RFC8555] defines the following values for the Order
resource's status: "pending", "ready", "processing", "valid", and resource's status: "pending", "ready", "processing", "valid", and
"invalid". In the case of recurrent Orders, the status MUST be "invalid". In the case of auto-renewal Orders, the status MUST be
"valid" as long as STAR certificates are being issued. We add a new "valid" as long as STAR certificates are being issued. We add a new
status value: "canceled", see Section 3.1.2. status value: "canceled", see Section 3.1.2.
A STAR certificate is by definition a mutable resource. Instead of A STAR certificate is by definition a mutable resource. Instead of
overloading the semantics of the "certificate" attribute, this overloading the semantics of the "certificate" attribute, this
document defines a new attribute "star-certificate" to be used document defines a new attribute "star-certificate" to be used
instead of "certificate". instead of "certificate".
o star-certificate (optional, string): A URL for the (rolling) STAR o star-certificate (optional, string): A URL for the (rolling) STAR
certificate that has been issued in response to this Order. certificate that has been issued in response to this Order.
3.1.2. Canceling a Recurrent Order 3.1.2. Canceling an Auto-renewal Order
An important property of the recurrent Order is that it can be An important property of the auto-renewal Order is that it can be
canceled by the IdO, with no need for certificate revocation. To canceled by the IdO, with no need for certificate revocation. To
cancel the Order, the ACME client sends a POST to the Order URL as cancel the Order, the ACME client sends a POST to the Order URL as
shown in Figure 3. shown in Figure 3.
POST /acme/order/TOlocE8rfgo HTTP/1.1 POST /acme/order/TOlocE8rfgo HTTP/1.1
Host: example.org Host: example.org
Content-Type: application/jose+json Content-Type: application/jose+json
{ {
"protected": base64url({ "protected": base64url({
skipping to change at page 9, line 22 skipping to change at page 9, line 22
"kid": "https://example.com/acme/acct/evOfKhNU60wg", "kid": "https://example.com/acme/acct/evOfKhNU60wg",
"nonce": "5XJ1L3lEkMG7tR6pA00clA", "nonce": "5XJ1L3lEkMG7tR6pA00clA",
"url": "https://example.com/acme/order/TOlocE8rfgo" "url": "https://example.com/acme/order/TOlocE8rfgo"
}), }),
"payload": base64url({ "payload": base64url({
"status": "canceled" "status": "canceled"
}), }),
"signature": "H6ZXtGjTZyUnPeKn...wEA4TklBdh3e454g" "signature": "H6ZXtGjTZyUnPeKn...wEA4TklBdh3e454g"
} }
Figure 3: Canceling a Recurrent Order Figure 3: Canceling an Auto-renewal Order
After a successful cancellation, the server MUST NOT issue any After a successful cancellation, the server MUST NOT issue any
additional certificates for this order. additional certificates for this Order.
Immediately after the order is canceled, the server: Immediately after the Order is canceled, the server:
o MUST update the status of the order resource to "canceled" and o MUST update the status of the Order resource to "canceled" and
MUST set an appropriate "expires" date; MUST set an appropriate "expires" date;
o MUST respond with 403 (Forbidden) to any requests to the star- o MUST respond with 403 (Forbidden) to any requests to the star-
certificate endpoint. The response SHOULD provide additional certificate endpoint. The response SHOULD provide additional
information using a problem document [RFC7807] with type information using a problem document [RFC7807] with type
"urn:ietf:params:acme:error:recurrentOrderCanceled". "urn:ietf:params:acme:error:autoRenewalCanceled".
Issuing a cancellation for an order that is not in "valid" state is Issuing a cancellation for an Order that is not in "valid" state is
not allowed. A client MUST NOT send such a request, and a server not allowed. A client MUST NOT send such a request, and a server
MUST return an error response with status code 400 (Bad Request) and MUST return an error response with status code 400 (Bad Request) and
type "urn:ietf:params:acme:error:recurrentCancellationInvalid". type "urn:ietf:params:acme:error:autoRenewalCancellationInvalid".
Explicit certificate revocation using the revokeCert interface Explicit certificate revocation using the revokeCert interface
(Section 7.6 of [RFC8555]) is not supported for STAR certificates. A (Section 7.6 of [RFC8555]) is not supported for STAR certificates. A
server receiving a revocation request for a STAR certificate MUST server receiving a revocation request for a STAR certificate MUST
return an error response with status code 403 (Forbidden) and type return an error response with status code 403 (Forbidden) and type
"urn:ietf:params:acme:error:recurrentRevocationNotSupported". "urn:ietf:params:acme:error:autoRenewalRevocationNotSupported".
3.2. Capability Discovery 3.2. Capability Discovery
In order to support the discovery of STAR capabilities, the directory In order to support the discovery of STAR capabilities, the "meta"
object defined in Section 9.7.6 of [RFC8555] is extended with the field inside the directory object defined in Section 9.7.6 of
following attributes inside the "meta" field: [RFC8555] is extended with a new "auto-renewal" object. The "auto-
renewal" object MUST be present if the server supports STAR. Its
structure is as follows:
o star-enabled (required, boolean): indicates STAR support. An ACME o min-lifetime (required, integer): minimum acceptable value for
STAR server MUST include this attribute, and MUST set it to true auto-renewal lifetime, in seconds.
if the feature is enabled. o max-duration (required, integer): maximum delta between the auto-
o star-min-cert-validity (required, integer): minimum acceptable renewal end-date and start-date, in seconds.
value for recurrent-certificate-validity, in seconds. o allow-certificate-get (optional, boolean): see Section 3.4.
o star-max-renewal (required, integer): maximum delta between
recurrent-end-date and recurrent-start-date, in seconds.
o star-allow-certificate-get (optional, boolean): see Section 3.4.
An example directory object advertising STAR support with one day An example directory object advertising STAR support with one day
star-min-cert-validity and one year star-max-renewal, and supporting min-lifetime and one year max-duration, and supporting certificate
certificate fetching with an HTTP GET is shown in Figure 4. fetching with an HTTP GET is shown in Figure 4.
{ {
"new-nonce": "https://example.com/acme/new-nonce", "new-nonce": "https://example.com/acme/new-nonce",
"new-account": "https://example.com/acme/new-account", "new-account": "https://example.com/acme/new-account",
"new-order": "https://example.com/acme/new-order", "new-order": "https://example.com/acme/new-order",
"new-authz": "https://example.com/acme/new-authz", "new-authz": "https://example.com/acme/new-authz",
"revoke-cert": "https://example.com/acme/revoke-cert", "revoke-cert": "https://example.com/acme/revoke-cert",
"key-change": "https://example.com/acme/key-change", "key-change": "https://example.com/acme/key-change",
"meta": { "meta": {
"terms-of-service": "https://example.com/acme/terms/2017-5-30", "terms-of-service": "https://example.com/acme/terms/2017-5-30",
"website": "https://www.example.com/", "website": "https://www.example.com/",
"caa-identities": ["example.com"], "caa-identities": ["example.com"],
"star-enabled": true, "auto-renewal": {
"star-min-cert-validity": 86400, "min-lifetime": 86400,
"star-max-renewal": 31536000, "max-duration": 31536000,
"star-allow-certificate-get": true "allow-certificate-get": true
}
} }
} }
Figure 4: Directory object with STAR support Figure 4: Directory object with STAR support
3.3. Fetching the Certificates 3.3. Fetching the Certificates
The certificate is fetched from the star-certificate endpoint with The certificate is fetched from the star-certificate endpoint with
POST-as-GET as per [RFC8555] Section 7.4.2, unless client and server POST-as-GET as per [RFC8555] Section 7.4.2, unless client and server
have successfully negotiated the "unauthenticated GET" option have successfully negotiated the "unauthenticated GET" option
skipping to change at page 12, line 12 skipping to change at page 12, line 12
It discloses in a simpler form information that is already It discloses in a simpler form information that is already
available inside the credential. available inside the credential.
To improve robustness, the next certificate MUST be made available by To improve robustness, the next certificate MUST be made available by
the ACME CA at the URL pointed by "star-certificate" at the latest the ACME CA at the URL pointed by "star-certificate" at the latest
halfway through the lifetime of the currently active certificate. It halfway through the lifetime of the currently active certificate. It
is worth noting that this has an implication in case of cancellation: is worth noting that this has an implication in case of cancellation:
in fact, from the time the next certificate is made available, the in fact, from the time the next certificate is made available, the
cancellation is not completely effective until the latter also cancellation is not completely effective until the latter also
expires. To avoid the client accidentally entering a broken state, expires. To avoid the client accidentally entering a broken state,
the "next" certificate MUST be pre-dated so that it is already valid the notBefore of the "next" certificate MUST be set so that the
when it is published at the "star-certificate" URL. Note that the certificate is already valid when it is published at the "star-
server might need to increase the recurrent-certificate-predate value certificate" URL. Note that the server might need to increase the
to satisfy the latter requirement. For further discussion on pre- auto-renewal lifetime-adjust value to satisfy the latter requirement.
dating, see Section 4.1. For further rationale on the need for adjusting the certificate
validity, see Section 4.1.
The server MUST NOT issue any additional certificates for this order The server MUST NOT issue any additional certificates for this Order
beyond its recurrent-end-date. beyond its auto-renewal end-date.
Immediately after the order expires, the server MUST respond with 403 Immediately after the Order expires, the server MUST respond with 403
(Forbidden) to any requests to the star-certificate endpoint. The (Forbidden) to any requests to the star-certificate endpoint. The
response SHOULD provide additional information using a problem response SHOULD provide additional information using a problem
document [RFC7807] with type document [RFC7807] with type
"urn:ietf:params:acme:error:recurrentOrderExpired". Note that the "urn:ietf:params:acme:error:autoRenewalExpired". Note that the Order
Order resource's state remains "valid", as per the base protocol. resource's state remains "valid", as per the base protocol.
3.4. Negotiating an unauthenticated GET 3.4. Negotiating an unauthenticated GET
In order to enable the name delegation workflow defined in In order to enable the name delegation workflow defined in
[I-D.ietf-acme-star-delegation] as well as to increase the [I-D.ietf-acme-star-delegation] as well as to increase the
reliability of the STAR ecosystem (see Section 4.3 for details), this reliability of the STAR ecosystem (see Section 4.3 for details), this
document defines a mechanism that allows a server to advertise document defines a mechanism that allows a server to advertise
support for accessing star-certificate resources via unauthenticated support for accessing star-certificate resources via unauthenticated
GET (instead of, or in addition to, POST-as-GET), and a client to GET (instead of, or in addition to, POST-as-GET), and a client to
enable this service with per-Order granularity. enable this service with per-Order granularity.
Specifically, a server states its availability to grant Specifically, a server states its availability to grant
unauthenticated access to a client's Order star-certificate by unauthenticated access to a client's Order star-certificate by
setting the star-allow-certificate-get attribute to true in the meta setting the allow-certificate-get attribute to true in the auto-
field of the Directory object: renewal object of the meta field inside the Directory object:
o star-allow-certificate-get (optional, boolean): If this field is o allow-certificate-get (optional, boolean): If this field is
present and set to true, the server allows GET requests to star- present and set to true, the server allows GET requests to star-
certificate URLs. certificate URLs.
A client states its will to access the issued star-certificate via A client states its will to access the issued star-certificate via
unauthenticated GET by adding a recurrent-certificate-get attribute unauthenticated GET by adding an allow-certificate-get attribute to
to its Order and setting it to true. the auto-renewal object of its Order and setting it to true.
o recurrent-certificate-get (optional, boolean): If this field is o allow-certificate-get (optional, boolean): If this field is
present and set to true, the client requests the server to allow present and set to true, the client requests the server to allow
unauthenticated GET to the star-certificate associated with this unauthenticated GET to the star-certificate associated with this
Order. Order.
If the server accepts the request, it MUST reflect the attribute If the server accepts the request, it MUST reflect the attribute
setting in the resulting Order object. setting in the resulting Order object.
3.5. Computing notBefore and notAfter of STAR Certificates 3.5. Computing notBefore and notAfter of STAR Certificates
We define "nominal renewal date" the point in time when a new short- We define "nominal renewal date" the point in time when a new short-
term certificate for a given STAR Order is due. It is a multiple of term certificate for a given STAR Order is due. It is a multiple of
the Order's recurrent-certificate-validity that starts with the the Order's auto-renewal lifetime that starts with the issuance of
issuance of the first short-term certificate and is upper-bounded by the first short-term certificate and is upper-bounded by the Order's
the Order's recurrent-end-date (Figure 6). auto-renewal end-date (Figure 6).
rcv - STAR Order's recurrent-certificate-validity T - STAR Order's auto-renewal lifetime
red - STAR Order's recurrent-end-date end - STAR Order's auto-renewal end-date
nrd[i] - nominal renewal date of the i-th STAR certificate nrd[i] - nominal renewal date of the i-th STAR certificate
.-rcv-. .-rcv-. .-rcv-. .__. .- T -. .- T -. .- T -. .__.
/ \ / \ / \ / red / \ / \ / \ / end
-----------o---------o---------o---------o----X-------> t -----------o---------o---------o---------o----X-------> t
nrd[0] nrd[1] nrd[2] nrd[3] nrd[0] nrd[1] nrd[2] nrd[3]
Figure 6: Nominal Renewal Date Figure 6: Nominal Renewal Date
The rules to determine the notBefore and notAfter values of the i-th The rules to determine the notBefore and notAfter values of the i-th
STAR certificate are as follows: STAR certificate are as follows:
notBefore = nrd[i] - predating notAfter = min(nrd[i] + T, end)
notAfter = min(nrd[i] + rcv, red) notBefore = nrd[i] - max(adjust_client, adjust_server)
where "predating" is the max between the (optional) recurrent- Where "adjust_client" is the min between the auto-renewal lifetime-
certificate-predate (rcp) and the amount of pre-dating that the adjust value ("la"), optionally supplied by the client, and the auto-
server needs to add to make sure that all certificates being renewal lifetime of each short-term certificate ("T");
published are valid at the time of publication (Section 3.3). The "adjust_server" is the amount of padding added by the ACME server to
server pre-dating is a fraction f of rcv (i.e., f * rcv with .5 <= f make sure that all certificates being published are valid at the time
< 1). of publication. The server padding is a fraction f of T (i.e., f * T
with .5 <= f < 1, see Section 3.3):
predating = max(rcp, f * rcv) adjust_client = min(T, la)
adjust_server = f * T
Note that the ACME server MUST NOT set the notBefore of the first
STAR certificate to a date prior to the auto-renewal start-date.
3.5.1. Example 3.5.1. Example
Given a server that intends to publish the next STAR certificate Given a server that intends to publish the next STAR certificate
halfway through the lifetime of the previous one, and a STAR Order halfway through the lifetime of the previous one, and a STAR Order
with the following attributes: with the following attributes:
{ "auto-renewal": {
"recurrent-start-date": "2016-01-10T00:00:00Z", "start-date": "2016-01-10T00:00:00Z",
"recurrent-end-date": "2016-01-20T00:00:00Z", "end-date": "2016-01-20T00:00:00Z",
"recurrent-certificate-validity": 345600, // 4 days "lifetime": 345600, // 4 days
"recurrent-certificate-predate": 518400 // 6 days "lifetime-adjust": 259200 // 3 days
} }
The amount of pre-dating that needs to be subtracted from each The amount of time that needs to be subtracted from each nominal
nominal renewal date is 6 days - i.e., max(518400, 345600 * .5). renewal date is 3 days - i.e., max(min(345600, 259200), 345600 * .5).
The notBefore and notAfter of each short-term certificate are: The notBefore and notAfter of each short-term certificate are:
+----------------------+----------------------+ +----------------------+----------------------+
| notBefore | notAfter | | notBefore | notAfter |
+----------------------+----------------------+ +----------------------+----------------------+
| 2016-01-04T00:00:00Z | 2016-01-14T00:00:00Z | | 2016-01-10T00:00:00Z | 2016-01-14T00:00:00Z |
| 2016-01-08T00:00:00Z | 2016-01-18T00:00:00Z | | 2016-01-11T00:00:00Z | 2016-01-18T00:00:00Z |
| 2016-01-12T00:00:00Z | 2016-01-20T00:00:00Z | | 2016-01-15T00:00:00Z | 2016-01-20T00:00:00Z |
+----------------------+----------------------+ +----------------------+----------------------+
A client should expect each certificate to be available from the The value of the notBefore is also the time at which the client
star-certificate endpoint at the following times: should expect the new certificate to be available from the star-
certificate endpoint.
+------------------------------------+
| 2016-01-10T00:00:00Z (or earlier) |
| 2016-01-12T00:00:00Z |
| 2016-01-16T00:00:00Z |
+------------------------------------+
4. Operational Considerations 4. Operational Considerations
4.1. The Meaning of "Short Term" and the Impact of Skewed Clocks 4.1. The Meaning of "Short Term" and the Impact of Skewed Clocks
"Short Term" is a relative concept, therefore trying to define a cut- "Short Term" is a relative concept, therefore trying to define a cut-
off point that works in all cases would be a useless exercise. In off point that works in all cases would be a useless exercise. In
practice, the expected lifetime of a STAR certificate will be counted practice, the expected lifetime of a STAR certificate will be counted
in minutes, hours or days, depending on different factors: the in minutes, hours or days, depending on different factors: the
underlying requirements for revocation, how much clock underlying requirements for revocation, how much clock
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for the Web use case, informed by current operational and research for the Web use case, informed by current operational and research
experience. experience.
Acer et al. [Acer] find that one of the main causes of "HTTPS error" Acer et al. [Acer] find that one of the main causes of "HTTPS error"
warnings in browsers is misconfigured client clocks. In particular, warnings in browsers is misconfigured client clocks. In particular,
they observe that roughly 95% of the "severe" clock skews - the 6.7% they observe that roughly 95% of the "severe" clock skews - the 6.7%
of clock-related breakage reports which account for clients that are of clock-related breakage reports which account for clients that are
more than 24 hours behind - happen to be within 6-7 days. more than 24 hours behind - happen to be within 6-7 days.
In order to avoid these spurious warnings about a not (yet) valid In order to avoid these spurious warnings about a not (yet) valid
server certificate, it is RECOMMENDED that site owners pre-date their server certificate, site owners could use the auto-renewal lifetime-
Web facing certificates by 5 to 7 days. The exact number depends on adjust attribute to control the effective lifetime of their Web
the percentage of the "clock-skewed" population that the site owner facing certificates. The exact number depends on the percentage of
expects to protect - 5 days cover 97.3%, 7 days cover 99.6%. Note the "clock-skewed" population that the site owner expects to protect
that exact choice is also likely to depend on the kind of clients - 5 days cover 97.3%, 7 days cover 99.6% as well as the nominal auto-
that is prevalent for a given site or app - for example, Android and renewal lifetime of the STAR Order. Note that exact choice is also
Mac OS clients are known to behave better than Windows clients. likely to depend on the kind of clients that is prevalent for a given
These considerations are clearly out of scope of the present site or app - for example, Android and Mac OS clients are known to
document. behave better than Windows clients. These considerations are clearly
out of scope of the present document.
In terms of security, STAR certificates and certificates with OCSP In terms of security, STAR certificates and certificates with OCSP
must-staple [RFC7633] can be considered roughly equivalent if the must-staple [RFC7633] can be considered roughly equivalent if the
STAR certificate's and the OCSP response's lifetimes are the same. STAR certificate's and the OCSP response's lifetimes are the same.
Given OCSP responses can be cached on average for 4 days [Stark], it Given OCSP responses can be cached on average for 4 days [Stark], it
is RECOMMENDED that a STAR certificate that is used on the Web has an is RECOMMENDED that a STAR certificate that is used on the Web has an
"effective" lifetime (excluding any pre-dating to account for clock "effective" lifetime (excluding any adjustment to account for clock
skews) no longer than 4 days. skews) no longer than 4 days.
4.2. Impact on Certificate Transparency (CT) Logs 4.2. Impact on Certificate Transparency (CT) Logs
Even in the highly unlikely case STAR becomes the only certificate Even in the highly unlikely case STAR becomes the only certificate
issuance model, discussion with the IETF TRANS Working Group and issuance model, discussion with the IETF TRANS Working Group and
Certificate Transparency (CT) logs implementers suggests that Certificate Transparency (CT) logs implementers suggests that
existing CT Log Server implementations are capable of sustaining the existing CT Log Server implementations are capable of sustaining the
resulting 100-fold increase in ingestion rate. Additionally, such a resulting 100-fold increase in ingestion rate. Additionally, such a
future, higher load could be managed with a variety of techniques future, higher load could be managed with a variety of techniques
(e.g., sharding by modulo of certificate hash, using "smart" load- (e.g., sharding by modulo of certificate hash, using "smart" load-
balancing CT proxies, etc.). With regards to the increase in the log balancing CT proxies, etc.). With regards to the increase in the log
size, current CT log growth is already being managed with schemes size, current CT log growth is already being managed with schemes
like Chrome's Log Policy [OBrien] which allow Operators to define like Chrome's Log Policy [OBrien] which allow Operators to define
their log life-cycle; and allowing the CAs, User Agents, Monitors, their log life-cycle; and allowing the CAs, User Agents, Monitors,
and any other interested entities to build-in support for that life- and any other interested entities to build-in support for that life-
cycle ahead of time. cycle ahead of time.
4.3. Dependability 4.3. HTTP Caching and Dependability
When using authenticated POST-as-GET, the HTTPS endpoint from where When using authenticated POST-as-GET, the HTTPS endpoint from where
the STAR certificate is fetched can't be easily replicated by an on- the STAR certificate is fetched can't be easily replicated by an on-
path HTTP cache. Reducing the caching properties of the protocol path HTTP cache. Reducing the caching properties of the protocol
makes STAR clients increasingly dependent on the ACME server makes STAR clients increasingly dependent on the ACME server
availability. This might be problematic given the relatively high availability. This might be problematic given the relatively high
rate of client-server interactions in a STAR ecosystem. Clients and rate of client-server interactions in a STAR ecosystem. Clients and
servers should consider using the mechanism described in Section 3.4 servers should consider using the mechanism described in Section 3.4
to mitigate the risk. to mitigate the risk.
When using unauthenticated GET to fetch the STAR certificate, the
server SHALL use the appropriate cache directives to set the
freshness lifetime of the response (Section 5.2 of [RFC7234]) such
that on-path caches will consider it stale before or at the time its
effective lifetime is due to expire.
5. Implementation Status 5. Implementation Status
Note to RFC Editor: please remove this section before publication, Note to RFC Editor: please remove this section before publication,
including the reference to [RFC7942]. including the reference to [RFC7942].
This section records the status of known implementations of the This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942]. Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to assist the IETF in its decision processes in progressing drafts to
skipping to change at page 16, line 49 skipping to change at page 17, line 10
The following subsections offer a basic description, detailed The following subsections offer a basic description, detailed
information is available in https://github.com/mami- information is available in https://github.com/mami-
project/lurk/blob/master/proxySTAR_v2/README.md project/lurk/blob/master/proxySTAR_v2/README.md
5.1.1. ACME Server with STAR extension 5.1.1. ACME Server with STAR extension
This is a fork of the Let's Encrypt Boulder project that implements This is a fork of the Let's Encrypt Boulder project that implements
an ACME compliant CA. It includes modifications to extend the ACME an ACME compliant CA. It includes modifications to extend the ACME
protocol as it is specified in this draft, to support recurrent protocol as it is specified in this draft, to support recurrent
orders and cancelling orders. Orders and cancelling Orders.
The implementation understands the new "recurrent" attributes as part The implementation understands the new "recurrent" attributes as part
of the Certificate issuance in the POST request for a new resource. of the Certificate issuance in the POST request for a new resource.
An additional process "renewalManager.go" has been included in An additional process "renewalManager.go" has been included in
parallel that reads the details of each recurrent request, parallel that reads the details of each recurrent request,
automatically produces a "cron" Linux based task that issues the automatically produces a "cron" Linux based task that issues the
recurrent certificates, until the lifetime ends or the order is recurrent certificates, until the lifetime ends or the Order is
canceled. This process is also in charge of maintaining a fixed URI canceled. This process is also in charge of maintaining a fixed URI
to enable the NDC to download certificates, unlike Boulder's regular to enable the NDC to download certificates, unlike Boulder's regular
process of producing a unique URI per certificate. process of producing a unique URI per certificate.
5.1.2. STAR Proxy 5.1.2. STAR Proxy
The STAR Proxy has a double role as ACME client and STAR Server. The The STAR Proxy has a double role as ACME client and STAR Server. The
former is a fork of the EFF Certbot project that implements an ACME former is a fork of the EFF Certbot project that implements an ACME
compliant client with the STAR extension. The latter is a basic HTTP compliant client with the STAR extension. The latter is a basic HTTP
REST API server. REST API server.
The STAR Proxy understands the basic API request with a server. The The STAR Proxy understands the basic API request with a server. The
current implementation of the API is defined in draft-ietf-acme-star- current implementation of the API is defined in draft-ietf-acme-star-
01. Registration or order cancellation triggers the modified Certbot 01. Registration or Order cancellation triggers the modified Certbot
client that requests, or cancels, the recurrent generation of client that requests, or cancels, the recurrent generation of
certificates using the STAR extension over ACME protocol. The URI certificates using the STAR extension over ACME protocol. The URI
with the location of the recurrent certificate is delivered to the with the location of the recurrent certificate is delivered to the
STAR client as a response. STAR client as a response.
5.2. Level of Maturity 5.2. Level of Maturity
This is a prototype. This is a prototype.
5.3. Coverage 5.3. Coverage
skipping to change at page 18, line 34 skipping to change at page 18, line 45
and test the protocol. and test the protocol.
5.7. Contact Information 5.7. Contact Information
See author details below. See author details below.
6. IANA Considerations 6. IANA Considerations
[[RFC Editor: please replace XXXX below by the RFC number.]] [[RFC Editor: please replace XXXX below by the RFC number.]]
6.1. New Error Types 6.1. New Registries
This document requests that IANA create the following new registries:
o ACME Order Auto Renewal Fields (Section 6.4)
o ACME Directory Metadata Auto Renewal Fields (Section 6.6)
6.2. New Error Types
This document adds the following entries to the ACME Error Type This document adds the following entries to the ACME Error Type
registry: registry:
+---------------------------------+---------------------+-----------+ +-----------------------------------+-------------------+-----------+
| Type | Description | Reference | | Type | Description | Reference |
+---------------------------------+---------------------+-----------+ +-----------------------------------+-------------------+-----------+
| recurrentOrderCanceled | The short-term | RFC XXXX | | autoRenewalCanceled | The short-term | RFC XXXX |
| | certificate is no | | | | certificate is no | |
| | longer available | | | | longer available | |
| | because the | | | | because the auto- | |
| | recurrent order has | | | | renewal Order has | |
| | been explicitly | | | | been explicitly | |
| | canceled by the IdO | | | | canceled by the | |
| recurrentOrderExpired | The short-term | RFC XXXX | | | IdO | |
| | certificate is no | | | autoRenewalExpired | The short-term | RFC XXXX |
| | longer available | | | | certificate is no | |
| | because the | | | | longer available | |
| | recurrent order has | | | | because the auto- | |
| | expired | | | | renewal Order has | |
| recurrentCancellationInvalid | A request to cancel | RFC XXXX | | | expired | |
| | a recurrent order | | | autoRenewalCancellationInvalid | A request to | RFC XXXX |
| | that is not in | | | | cancel a auto- | |
| | state "valid" has | | | | renewal Order | |
| | been received | | | | that is not in | |
| recurrentRevocationNotSupported | A request to revoke | RFC XXXX | | | state "valid" has | |
| | a recurrent order | | | | been received | |
| | has been received | | | autoRenewalRevocationNotSupported | A request to | RFC XXXX |
+---------------------------------+---------------------+-----------+ | | revoke a auto- | |
| | renewal Order has | |
| | been received | |
+-----------------------------------+-------------------+-----------+
6.2. New fields in Order Objects 6.3. New fields in Order Objects
This document adds the following entries to the ACME Order Object This document adds the following entries to the ACME Order Object
Fields registry: Fields registry:
+------------------------------+---------+--------------+-----------+ +------------------+------------+--------------+-----------+
| Field Name | Field | Configurable | Reference | | Field Name | Field Type | Configurable | Reference |
| | Type | | | +------------------+------------+--------------+-----------+
+------------------------------+---------+--------------+-----------+ | auto-renewal | object | true | RFC XXXX |
| recurrent | string | true | RFC XXXX | | star-certificate | string | false | RFC XXXX |
| recurrent-start-date | string | true | RFC XXXX | +------------------+------------+--------------+-----------+
| recurrent-end-date | string | true | RFC XXXX |
| recurrent-certificate- | integer | true | RFC XXXX |
| validity | | | |
| recurrent-certificate- | integer | true | RFC XXXX |
| predate | | | |
| recurrent-certificate-get | boolean | true | RFC XXXX |
| star-certificate | string | false | RFC XXXX |
+------------------------------+---------+--------------+-----------+
6.3. New fields in the "meta" Object within a Directory Object 6.4. Fields in the "auto-renewal" Object within an Order Object
This document adds the following entries to the ACME Directory The "ACME Order Auto Renewal Fields" registry lists field names that
Metadata Fields: are defined for use in the JSON object included in the "auto-renewal"
field of an ACME order object.
+----------------------------+------------+-----------+ Template:
| Field Name | Field Type | Reference |
+----------------------------+------------+-----------+
| star-enabled | boolean | RCF XXXX |
| star-min-cert-validity | integer | RCF XXXX |
| star-max-renewal | integer | RCF XXXX |
| star-allow-certificate-get | boolean | RFC XXXX |
+----------------------------+------------+-----------+
6.4. Cert-Not-Before and Cert-Not-After HTTP Headers o Field name: The string to be used as a field name in the JSON
object
o Field type: The type of value to be provided, e.g., string,
boolean, array of string
o Configurable: Boolean indicating whether the server should accept
values provided by the client
o Reference: Where this field is defined
+-----------------------+------------+--------------+-----------+
| Field Name | Field Type | Configurable | Reference |
+-----------------------+------------+--------------+-----------+
| start-date | string | true | RFC XXXX |
| end-date | string | true | RFC XXXX |
| lifetime | integer | true | RFC XXXX |
| lifetime-adjust | integer | true | RFC XXXX |
| allow-certificate-get | boolean | true | RFC XXXX |
+-----------------------+------------+--------------+-----------+
6.5. New fields in the "meta" Object within a Directory Object
This document adds the following entry to the ACME Directory Metadata
Fields:
+--------------+------------+-----------+
| Field Name | Field Type | Reference |
+--------------+------------+-----------+
| auto-renewal | object | RFC XXXX |
+--------------+------------+-----------+
6.6. Fields in the "auto-renewal" Object within a Directory Metadata
Object
The "ACME Directory Metadata Auto Renewal Fields" registry lists
field names that are defined for use in the JSON object included in
the "auto-renewal" field of an ACME directory "meta" object.
Template:
o Field name: The string to be used as a field name in the JSON
object
o Field type: The type of value to be provided, e.g., string,
boolean, array of string
o Reference: Where this field is defined
+-----------------------+------------+-----------+
| Field Name | Field Type | Reference |
+-----------------------+------------+-----------+
| min-lifetime | integer | RFC XXXX |
| max-duration | integer | RFC XXXX |
| allow-certificate-get | boolean | RFC XXXX |
+-----------------------+------------+-----------+
6.7. Cert-Not-Before and Cert-Not-After HTTP Headers
The "Message Headers" registry should be updated with the following The "Message Headers" registry should be updated with the following
additional values: additional values:
+-------------------+----------+----------+-----------------------+ +-------------------+----------+----------+-----------------------+
| Header Field Name | Protocol | Status | Reference | | Header Field Name | Protocol | Status | Reference |
+-------------------+----------+----------+-----------------------+ +-------------------+----------+----------+-----------------------+
| Cert-Not-Before | http | standard | RFC XXXX, Section 3.3 | | Cert-Not-Before | http | standard | RFC XXXX, Section 3.3 |
| Cert-Not-After | http | standard | RFC XXXX, Section 3.3 | | Cert-Not-After | http | standard | RFC XXXX, Section 3.3 |
+-------------------+----------+----------+-----------------------+ +-------------------+----------+----------+-----------------------+
skipping to change at page 21, line 10 skipping to change at page 22, line 10
nextUpdate goes unnoticed by the RP. nextUpdate goes unnoticed by the RP.
More discussion of the security of STAR certificates is available in More discussion of the security of STAR certificates is available in
[Topalovic]. [Topalovic].
7.2. Denial of Service Considerations 7.2. Denial of Service Considerations
STAR adds a new attack vector that increases the threat of denial of STAR adds a new attack vector that increases the threat of denial of
service attacks, caused by the change to the CA's behavior. Each service attacks, caused by the change to the CA's behavior. Each
STAR request amplifies the resource demands upon the CA, where one STAR request amplifies the resource demands upon the CA, where one
order produces not one, but potentially dozens or hundreds of Order produces not one, but potentially dozens or hundreds of
certificates, depending on the "recurrent-certificate-validity" certificates, depending on the auto-renewal "lifetime" parameter. An
parameter. An attacker can use this property to aggressively reduce attacker can use this property to aggressively reduce the auto-
the "recurrent-certificate-validity" (e.g. 1 sec.) jointly with other renewal "lifetime" (e.g. 1 sec.) jointly with other ACME attack
ACME attack vectors identified in Sec. 10 of [RFC8555]. Other vectors identified in Sec. 10 of [RFC8555]. Other collateral impact
collateral impact is related to the certificate endpoint resource is related to the certificate endpoint resource where the client can
where the client can retrieve the certificates periodically. If this retrieve the certificates periodically. If this resource is external
resource is external to the CA (e.g. a hosted web server), the to the CA (e.g. a hosted web server), the previous attack will be
previous attack will be reflected to that resource. reflected to that resource.
Mitigation recommendations from ACME still apply, but some of them Mitigation recommendations from ACME still apply, but some of them
need to be adjusted. For example, applying rate limiting to the need to be adjusted. For example, applying rate limiting to the
initial request, by the nature of the recurrent behavior cannot solve initial request, by the nature of the auto-renewal behavior cannot
the above problem. The CA server needs complementary mitigation and solve the above problem. The CA server needs complementary
specifically, it SHOULD enforce a minimum value on "recurrent- mitigation and specifically, it SHOULD enforce a minimum value on
certificate-validity". Alternatively, the CA can set an internal auto-renewal "lifetime". Alternatively, the CA can set an internal
certificate generation processes rate limit. certificate generation processes rate limit.
7.3. Privacy Considerations 7.3. Privacy Considerations
In order to avoid correlation of certificates by account, if In order to avoid correlation of certificates by account, if
unauthenticated GET is negotiated (Section 3.4) the recommendation in unauthenticated GET is negotiated (Section 3.4) the recommendation in
Section 10.5 of [RFC8555] regarding the choice of URL structure Section 10.5 of [RFC8555] regarding the choice of URL structure
applies, i.e. servers SHOULD choose URLs of certificate resources in applies, i.e. servers SHOULD choose URLs of certificate resources in
a non-guessable way, for example using capability URLs a non-guessable way, for example using capability URLs
[W3C.WD-capability-urls-20140218]. [W3C.WD-capability-urls-20140218].
8. Acknowledgments 8. Acknowledgments
This work is partially supported by the European Commission under This work is partially supported by the European Commission under
Horizon 2020 grant agreement no. 688421 Measurement and Architecture Horizon 2020 grant agreement no. 688421 Measurement and Architecture
for a Middleboxed Internet (MAMI). This support does not imply for a Middleboxed Internet (MAMI). This support does not imply
endorsement. endorsement.
Thanks to Roman Danyliw, Jon Peterson, Eric Rescorla, Sean Turner, Thanks to Richard Barnes, Roman Danyliw, Jon Peterson, Eric Rescorla,
Martin Thomson and Mehmet Ersue for helpful comments and discussions Ryan Sleevi, Sean Turner, Martin Thomson and Mehmet Ersue for helpful
that have shaped this document. comments and discussions that have shaped this document.
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<https://www.rfc-editor.org/info/rfc3339>. <https://www.rfc-editor.org/info/rfc3339>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231, Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014, DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>. <https://www.rfc-editor.org/info/rfc7231>.
[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
RFC 7234, DOI 10.17487/RFC7234, June 2014,
<https://www.rfc-editor.org/info/rfc7234>.
[RFC7807] Nottingham, M. and E. Wilde, "Problem Details for HTTP [RFC7807] Nottingham, M. and E. Wilde, "Problem Details for HTTP
APIs", RFC 7807, DOI 10.17487/RFC7807, March 2016, APIs", RFC 7807, DOI 10.17487/RFC7807, March 2016,
<https://www.rfc-editor.org/info/rfc7807>. <https://www.rfc-editor.org/info/rfc7807>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8555] Barnes, R., Hoffman-Andrews, J., McCarney, D., and J. [RFC8555] Barnes, R., Hoffman-Andrews, J., McCarney, D., and J.
Kasten, "Automatic Certificate Management Environment Kasten, "Automatic Certificate Management Environment
skipping to change at page 24, line 9 skipping to change at page 25, line 9
[W3C.WD-capability-urls-20140218] [W3C.WD-capability-urls-20140218]
Tennison, J., "Good Practices for Capability URLs", World Tennison, J., "Good Practices for Capability URLs", World
Wide Web Consortium WD WD-capability-urls-20140218, Wide Web Consortium WD WD-capability-urls-20140218,
February 2014, February 2014,
<http://www.w3.org/TR/2014/WD-capability-urls-20140218>. <http://www.w3.org/TR/2014/WD-capability-urls-20140218>.
Appendix A. Document History Appendix A. Document History
[[Note to RFC Editor: please remove before publication.]] [[Note to RFC Editor: please remove before publication.]]
A.1. draft-ietf-acme-star-08 A.1. draft-ietf-acme-star-09
Richard and Ryan's review resulted in the following updates:
o STAR Order and Directory Meta attributes renamed slightly and
grouped under two brand new "auto-renewal" objects;
o IANA registration updated accordingly (note that two new
registries have been added as a consequence);
o Unbounded pre-dating of certificates removed so that STAR certs
are never issued with their notBefore in the past;
o Changed "recurrent" to "autoRenewal" in error codes;
o Changed "recurrent" to "auto-renewal" in reference to Orders;
o Added operational considerations for HTTP caches.
A.2. draft-ietf-acme-star-08
o Improved text on interaction with CT Logs, responding to Mehmet o Improved text on interaction with CT Logs, responding to Mehmet
Ersue's review. Ersue's review.
A.2. draft-ietf-acme-star-07 A.3. draft-ietf-acme-star-07
o Changed the HTTP headers names and clarified the IANA o Changed the HTTP headers names and clarified the IANA
registration, following feedback from the IANA expert reviewer registration, following feedback from the IANA expert reviewer
A.3. draft-ietf-acme-star-06 A.4. draft-ietf-acme-star-06
o Roman's AD review o Roman's AD review
A.4. draft-ietf-acme-star-05 A.5. draft-ietf-acme-star-05
o EKR's AD review o EKR's AD review
o A detailed example of the timing of certificate issuance and o A detailed example of the timing of certificate issuance and
predating predating
o Added an explicit client-side parameter for predating o Added an explicit client-side parameter for predating
o Security considerations around unauthenticated GET o Security considerations around unauthenticated GET
A.5. draft-ietf-acme-star-04 A.6. draft-ietf-acme-star-04
o WG last call comments by Sean Turner o WG last call comments by Sean Turner
o revokeCert interface handling o revokeCert interface handling
o Allow negotiating plain-GET for certs o Allow negotiating plain-GET for certs
o In STAR Orders, use star-certificate instead of certificate o In STAR Orders, use star-certificate instead of certificate
A.6. draft-ietf-acme-star-03 A.7. draft-ietf-acme-star-03
o Clock skew considerations o Clock skew considerations
o Recommendations for "short" in the Web use case o Recommendations for "short" in the Web use case
o CT log considerations o CT log considerations
A.7. draft-ietf-acme-star-02 A.8. draft-ietf-acme-star-02
o Discovery of STAR capabilities via the directory object o Discovery of STAR capabilities via the directory object
o Use the more generic term Identifier Owner (IdO) instead of Domain o Use the more generic term Identifier Owner (IdO) instead of Domain
Name Owner (DNO) Name Owner (DNO)
o More precision about what goes in the order o More precision about what goes in the order
o Detail server side behavior on cancellation o Detail server side behavior on cancellation
A.8. draft-ietf-acme-star-01 A.9. draft-ietf-acme-star-01
o Generalized the introduction, separating out the specifics of o Generalized the introduction, separating out the specifics of
CDNs. CDNs.
o Clean out LURK-specific text. o Clean out LURK-specific text.
o Using a POST to ensure cancellation is authenticated. o Using a POST to ensure cancellation is authenticated.
o First and last date of recurrent cert, as absolute dates. o First and last date of recurrent cert, as absolute dates.
Validity of certs in seconds. Validity of certs in seconds.
o Use RFC7807 "Problem Details" in error responses. o Use RFC7807 "Problem Details" in error responses.
o Add IANA considerations. o Add IANA considerations.
o Changed the document's title. o Changed the document's title.
A.9. draft-ietf-acme-star-00 A.10. draft-ietf-acme-star-00
o Initial working group version. o Initial working group version.
o Removed the STAR interface, the protocol between NDC and DNO. o Removed the STAR interface, the protocol between NDC and DNO.
What remains is only the extended ACME protocol. What remains is only the extended ACME protocol.
A.10. draft-sheffer-acme-star-02 A.11. draft-sheffer-acme-star-02
o Using a more generic term for the delegation client, NDC. o Using a more generic term for the delegation client, NDC.
o Added an additional use case: public cloud services. o Added an additional use case: public cloud services.
o More detail on ACME authorization. o More detail on ACME authorization.
A.11. draft-sheffer-acme-star-01 A.12. draft-sheffer-acme-star-01
o A terminology section. o A terminology section.
o Some cleanup. o Some cleanup.
A.12. draft-sheffer-acme-star-00 A.13. draft-sheffer-acme-star-00
o Renamed draft to prevent confusion with other work in this space. o Renamed draft to prevent confusion with other work in this space.
o Added an initial STAR protocol: a REST API. o Added an initial STAR protocol: a REST API.
o Discussion of CDNI use cases. o Discussion of CDNI use cases.
A.13. draft-sheffer-acme-star-lurk-00 A.14. draft-sheffer-acme-star-lurk-00
o Initial version. o Initial version.
Authors' Addresses Authors' Addresses
Yaron Sheffer Yaron Sheffer
Intuit Intuit
EMail: yaronf.ietf@gmail.com EMail: yaronf.ietf@gmail.com
Diego Lopez Diego Lopez
Telefonica I+D Telefonica I+D
EMail: diego.r.lopez@telefonica.com EMail: diego.r.lopez@telefonica.com
Oscar Gonzalez de Dios Oscar Gonzalez de Dios
Telefonica I+D Telefonica I+D
EMail: oscar.gonzalezdedios@telefonica.com EMail: oscar.gonzalezdedios@telefonica.com
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