draft-ietf-acme-star-09.txt   draft-ietf-acme-star-10.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: March 20, 2020 O. Gonzalez de Dios Expires: April 15, 2020 O. Gonzalez de Dios
A. Pastor Perales A. Pastor Perales
Telefonica I+D Telefonica I+D
T. Fossati T. Fossati
ARM ARM
September 17, 2019 October 13, 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-09 draft-ietf-acme-star-10
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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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 March 20, 2020. This Internet-Draft will expire on April 15, 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
skipping to change at page 2, line 26 skipping to change at page 2, line 26
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
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 . . . . . . . . . . . . . . . . . . . . . . . . 5
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 an Auto-renewal Order . . . . . . . . . . . 8 3.1.2. Canceling an Auto-renewal Order . . . . . . . . . . . 8
3.2. Capability Discovery . . . . . . . . . . . . . . . . . . 9 3.2. Capability Discovery . . . . . . . . . . . . . . . . . . 10
3.3. Fetching the Certificates . . . . . . . . . . . . . . . . 10 3.3. Fetching the Certificates . . . . . . . . . . . . . . . . 11
3.4. Negotiating an unauthenticated GET . . . . . . . . . . . 12 3.4. Negotiating an unauthenticated GET . . . . . . . . . . . 13
3.5. Computing notBefore and notAfter of STAR Certificates . . 13 3.5. Computing notBefore and notAfter of STAR Certificates . . 14
3.5.1. Example . . . . . . . . . . . . . . . . . . . . . . . 14 3.5.1. Example . . . . . . . . . . . . . . . . . . . . . . . 15
4. Operational Considerations . . . . . . . . . . . . . . . . . 14 4. Operational Considerations . . . . . . . . . . . . . . . . . 15
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 . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2. Impact on Certificate Transparency (CT) Logs . . . . . . 15 4.2. Impact on Certificate Transparency (CT) Logs . . . . . . 16
4.3. HTTP Caching and Dependability . . . . . . . . . . . . . 15 4.3. HTTP Caching and Dependability . . . . . . . . . . . . . 16
5. Implementation Status . . . . . . . . . . . . . . . . . . . . 16 5. Implementation Status . . . . . . . . . . . . . . . . . . . . 17
5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 16 5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 17
5.1.1. ACME Server with STAR extension . . . . . . . . . . . 17 5.1.1. ACME Server with STAR extension . . . . . . . . . . . 18
5.1.2. STAR Proxy . . . . . . . . . . . . . . . . . . . . . 17 5.1.2. STAR Proxy . . . . . . . . . . . . . . . . . . . . . 18
5.2. Level of Maturity . . . . . . . . . . . . . . . . . . . . 17 5.2. Level of Maturity . . . . . . . . . . . . . . . . . . . . 18
5.3. Coverage . . . . . . . . . . . . . . . . . . . . . . . . 17 5.3. Coverage . . . . . . . . . . . . . . . . . . . . . . . . 18
5.4. Version Compatibility . . . . . . . . . . . . . . . . . . 18 5.4. Version Compatibility . . . . . . . . . . . . . . . . . . 19
5.5. Licensing . . . . . . . . . . . . . . . . . . . . . . . . 18 5.5. Licensing . . . . . . . . . . . . . . . . . . . . . . . . 19
5.6. Implementation experience . . . . . . . . . . . . . . . . 18 5.6. Implementation experience . . . . . . . . . . . . . . . . 19
5.7. Contact Information . . . . . . . . . . . . . . . . . . . 18 5.7. Contact Information . . . . . . . . . . . . . . . . . . . 19
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
6.1. New Registries . . . . . . . . . . . . . . . . . . . . . 18 6.1. New Registries . . . . . . . . . . . . . . . . . . . . . 19
6.2. New Error Types . . . . . . . . . . . . . . . . . . . . . 19 6.2. New Error Types . . . . . . . . . . . . . . . . . . . . . 20
6.3. New fields in Order Objects . . . . . . . . . . . . . . . 19 6.3. New fields in Order Objects . . . . . . . . . . . . . . . 20
6.4. Fields in the "auto-renewal" Object within an Order 6.4. Fields in the "auto-renewal" Object within an Order
Object . . . . . . . . . . . . . . . . . . . . . . . . . 20 Object . . . . . . . . . . . . . . . . . . . . . . . . . 21
6.5. New fields in the "meta" Object within a Directory Object 20 6.5. New fields in the "meta" Object within a Directory Object 21
6.6. Fields in the "auto-renewal" Object within a Directory 6.6. Fields in the "auto-renewal" Object within a Directory
Metadata Object . . . . . . . . . . . . . . . . . . . . . 20 Metadata Object . . . . . . . . . . . . . . . . . . . . . 22
6.7. Cert-Not-Before and Cert-Not-After HTTP Headers . . . . . 21 6.7. Cert-Not-Before and Cert-Not-After HTTP Headers . . . . . 22
7. Security Considerations . . . . . . . . . . . . . . . . . . . 21 7. Security Considerations . . . . . . . . . . . . . . . . . . . 22
7.1. No revocation . . . . . . . . . . . . . . . . . . . . . . 21 7.1. No revocation . . . . . . . . . . . . . . . . . . . . . . 22
7.2. Denial of Service Considerations . . . . . . . . . . . . 22 7.2. Denial of Service Considerations . . . . . . . . . . . . 23
7.3. Privacy Considerations . . . . . . . . . . . . . . . . . 22 7.3. Privacy Considerations . . . . . . . . . . . . . . . . . 24
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
9.1. Normative References . . . . . . . . . . . . . . . . . . 23 9.1. Normative References . . . . . . . . . . . . . . . . . . 24
9.2. Informative References . . . . . . . . . . . . . . . . . 23 9.2. Informative References . . . . . . . . . . . . . . . . . 25
Appendix A. Document History . . . . . . . . . . . . . . . . . . 25 Appendix A. Document History . . . . . . . . . . . . . . . . . . 27
A.1. draft-ietf-acme-star-09 . . . . . . . . . . . . . . . . . 25 A.1. draft-ietf-acme-star-10 . . . . . . . . . . . . . . . . . 27
A.2. draft-ietf-acme-star-08 . . . . . . . . . . . . . . . . . 25 A.2. draft-ietf-acme-star-09 . . . . . . . . . . . . . . . . . 27
A.3. draft-ietf-acme-star-07 . . . . . . . . . . . . . . . . . 25 A.3. draft-ietf-acme-star-08 . . . . . . . . . . . . . . . . . 27
A.4. draft-ietf-acme-star-06 . . . . . . . . . . . . . . . . . 25 A.4. draft-ietf-acme-star-07 . . . . . . . . . . . . . . . . . 27
A.5. draft-ietf-acme-star-05 . . . . . . . . . . . . . . . . . 25 A.5. draft-ietf-acme-star-06 . . . . . . . . . . . . . . . . . 27
A.6. draft-ietf-acme-star-04 . . . . . . . . . . . . . . . . . 25 A.6. draft-ietf-acme-star-05 . . . . . . . . . . . . . . . . . 27
A.7. draft-ietf-acme-star-03 . . . . . . . . . . . . . . . . . 26 A.7. draft-ietf-acme-star-04 . . . . . . . . . . . . . . . . . 28
A.8. draft-ietf-acme-star-02 . . . . . . . . . . . . . . . . . 26 A.8. draft-ietf-acme-star-03 . . . . . . . . . . . . . . . . . 28
A.9. draft-ietf-acme-star-01 . . . . . . . . . . . . . . . . . 26 A.9. draft-ietf-acme-star-02 . . . . . . . . . . . . . . . . . 28
A.10. draft-ietf-acme-star-00 . . . . . . . . . . . . . . . . . 26 A.10. draft-ietf-acme-star-01 . . . . . . . . . . . . . . . . . 28
A.11. draft-sheffer-acme-star-02 . . . . . . . . . . . . . . . 26 A.11. draft-ietf-acme-star-00 . . . . . . . . . . . . . . . . . 28
A.12. draft-sheffer-acme-star-01 . . . . . . . . . . . . . . . 26 A.12. draft-sheffer-acme-star-02 . . . . . . . . . . . . . . . 28
A.13. draft-sheffer-acme-star-00 . . . . . . . . . . . . . . . 26 A.13. draft-sheffer-acme-star-01 . . . . . . . . . . . . . . . 29
A.14. draft-sheffer-acme-star-lurk-00 . . . . . . . . . . . . . 27 A.14. draft-sheffer-acme-star-00 . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 A.15. draft-sheffer-acme-star-lurk-00 . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
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
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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
The proposed mechanism can be used as a building block of an The proposed mechanism can be used as a building block of an
efficient name-delegation protocol, for example one that exists efficient name-delegation protocol, for example one that exists
between a CDN or a cloud provider and its customers between a CDN or a cloud provider and its customers
[I-D.ietf-acme-star-delegation]. At any time, the service customer [I-D.ietf-acme-star-delegation]. At any time, the service customer
(i.e., the IdO) can terminate the delegation by simply instructing (i.e., the IdO) can terminate the delegation by simply instructing
the CA to stop the automatic renewal and letting the currently active the CA to stop the automatic renewal and letting the currently active
certificate expire shortly thereafter. Note that in this case the certificate expire shortly thereafter.
delegated entity needs to access the auto-renewed certificate without
being in possession of the ACME account key that was used for Note that in the name delegation use case the delegated entity needs
initiating the STAR issuance. to access the auto-renewed certificate without being in possession of
the ACME account key that was used for initiating the STAR issuance.
This leads to the optional use of unauthenticated GET in this
protocol (Section 3.4).
1.2. Terminology 1.2. Terminology
IdO Identifier Owner, the owner of an identifier, e.g.: a domain IdO Identifier Owner, the owner of an identifier, e.g.: a domain
name, a telephone number. name, a telephone number.
STAR Short-Term and Automatically Renewed X.509 certificates. STAR Short-Term and Automatically Renewed X.509 certificates.
1.3. Conventions used in this document 1.3. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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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 auto-renewal 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 dynamic resource, i.e., it
overloading the semantics of the "certificate" attribute, this refers to an entity that varies over time. Instead of overloading
document defines a new attribute "star-certificate" to be used the semantics of the "certificate" attribute, this document defines a
instead of "certificate". new attribute "star-certificate" to be used 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 an Auto-renewal Order 3.1.2. Canceling an Auto-renewal Order
An important property of the auto-renewal 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/ogfr8EcolOT HTTP/1.1
Host: example.org Host: example.org
Content-Type: application/jose+json Content-Type: application/jose+json
{ {
"protected": base64url({ "protected": base64url({
"alg": "ES256", "alg": "ES256",
"kid": "https://example.com/acme/acct/evOfKhNU60wg", "kid": "https://example.com/acme/acct/gw06UNhKfOve",
"nonce": "5XJ1L3lEkMG7tR6pA00clA", "nonce": "Alc00Ap6Rt7GMkEl3L1JX5",
"url": "https://example.com/acme/order/TOlocE8rfgo" "url": "https://example.com/acme/order/ogfr8EcolOT"
}), }),
"payload": base64url({ "payload": base64url({
"status": "canceled" "status": "canceled"
}), }),
"signature": "H6ZXtGjTZyUnPeKn...wEA4TklBdh3e454g" "signature": "g454e3hdBlkT4AEw...nKePnUyZTjGtXZ6H"
} }
Figure 3: Canceling an Auto-renewal 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: When 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:autoRenewalCanceled". "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:autoRenewalCancellationInvalid". type "urn:ietf:params:acme:error:autoRenewalCancellationInvalid".
The state machine described in Section 7.1.6 of [RFC8555] is extended
as illustrated in Figure 4 (State Transitions for Order Objects).
pending --------------+
| |
| All authz |
| "valid" |
V |
ready ---------------+
| |
| Receive |
| finalize |
| request |
V |
processing ------------+
| |
| First |
| certificate | Error or
| issued | Authorization failure
V V
valid invalid
|
| STAR
| Certificate
| canceled
V
canceled
Figure 4
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:autoRenewalRevocationNotSupported". "urn:ietf:params:acme:error:autoRenewalRevocationNotSupported".
3.2. Capability Discovery 3.2. Capability Discovery
In order to support the discovery of STAR capabilities, the "meta" In order to support the discovery of STAR capabilities, the "meta"
field inside the directory object defined in Section 9.7.6 of field inside the directory object defined in Section 9.7.6 of
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structure is as follows: structure is as follows:
o min-lifetime (required, integer): minimum acceptable value for o min-lifetime (required, integer): minimum acceptable value for
auto-renewal lifetime, in seconds. auto-renewal lifetime, in seconds.
o max-duration (required, integer): maximum delta between the auto- o max-duration (required, integer): maximum delta between the auto-
renewal end-date and start-date, in seconds. renewal end-date and start-date, in seconds.
o allow-certificate-get (optional, boolean): see Section 3.4. o 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
min-lifetime and one year max-duration, and supporting certificate min-lifetime and one year max-duration, and supporting certificate
fetching with an HTTP GET is shown in Figure 4. fetching with an HTTP GET is shown in Figure 5.
{ {
"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"],
"auto-renewal": { "auto-renewal": {
"min-lifetime": 86400, "min-lifetime": 86400,
"max-duration": 31536000, "max-duration": 31536000,
"allow-certificate-get": true "allow-certificate-get": true
} }
} }
} }
Figure 4: Directory object with STAR support Figure 5: 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
described in Section 3.4. In such case, the client can simply issue described in Section 3.4. In such case, the client can simply issue
a GET to the star-certificate resource without authenticating itself a GET to the star-certificate resource without authenticating itself
to the server as illustrated in Figure 5. to the server as illustrated in Figure 6.
GET /acme/cert/mAt3xBGaobw HTTP/1.1 GET /acme/cert/mAt3xBGaobw HTTP/1.1
Host: example.org Host: example.org
Accept: application/pem-certificate-chain Accept: application/pem-certificate-chain
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/pem-certificate-chain Content-Type: application/pem-certificate-chain
Link: <https://example.com/acme/some-directory>;rel="index" Link: <https://example.com/acme/some-directory>;rel="index"
Cert-Not-Before: Mon, 1 Feb 2016 00:00:00 GMT Cert-Not-Before: Thu, 3 Oct 2019 00:00:00 GMT
Cert-Not-After: Mon, 8 Feb 2016 00:00:00 GMT Cert-Not-After: Thu, 10 Oct 2019 00:00:00 GMT
-----BEGIN CERTIFICATE----- -----BEGIN CERTIFICATE-----
[End-entity certificate contents] [End-entity certificate contents]
-----END CERTIFICATE----- -----END CERTIFICATE-----
-----BEGIN CERTIFICATE----- -----BEGIN CERTIFICATE-----
[Issuer certificate contents] [Issuer certificate contents]
-----END CERTIFICATE----- -----END CERTIFICATE-----
-----BEGIN CERTIFICATE----- -----BEGIN CERTIFICATE-----
[Other certificate contents] [Other certificate contents]
-----END CERTIFICATE----- -----END CERTIFICATE-----
Figure 5: Fetching a STAR certificate with unauthenticated GET Figure 6: Fetching a STAR certificate with unauthenticated GET
The Server SHOULD include the "Cert-Not-Before" and "Cert-Not-After" The Server SHOULD include the "Cert-Not-Before" and "Cert-Not-After"
HTTP headers in the response. When they exist, they MUST be equal to HTTP header fields in the response. When they exist, they MUST be
the respective fields inside the end-entity certificate. Their equal to the respective fields inside the end-entity certificate.
format is "HTTP-date" as defined in Section 7.1.1.2 of [RFC7231]. Their format is "HTTP-date" as defined in Section 7.1.1.2 of
Their purpose is to enable client implementations that do not parse [RFC7231]. Their purpose is to enable client implementations that do
the certificate. not parse the certificate.
Following are further clarifications regarding usage of these Following are further clarifications regarding usage of these header
headers, as per [RFC7231] Sec. 8.3.1. All apply to both headers. fields, as per [RFC7231] Sec. 8.3.1. All apply to both headers.
o This header is a single value, not a list. o This header field is a single value, not a list.
o The header is used only in responses to GET, HEAD and POST-as-GET o The header field is used only in responses to GET, HEAD and POST-
requests, and only for MIME types that denote public key as-GET requests, and only for MIME types that denote public key
certificates. certificates.
o Header semantics are independent of context. o Header field semantics are independent of context.
o The header is not hop-by-hop. o The header field is not hop-by-hop.
o Intermediaries MAY insert or delete the value, but MUST ensure o Intermediaries MAY insert or delete the value;
that if present, the header value equals the corresponding value o If an intermediary inserts the value, it MUST ensure that the
within the credential. newly added value matches the corresponding value in the
o The header is not appropriate for a Vary field. certificate.
o The header is allowed within message trailers. o The header field is not appropriate for a Vary field.
o The header is not appropriate within redirects. o The header field is allowed within message trailers.
o The header does not introduce additional security considerations. o The header field is not appropriate within redirects.
It discloses in a simpler form information that is already o The header field does not introduce additional security
available inside the credential. considerations. It discloses in a simpler form information that
is already available inside the certificate.
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 "next" certificate
expires. To avoid the client accidentally entering a broken state, also expires. To avoid the client accidentally entering a broken
the notBefore of the "next" certificate MUST be set so that the state, the notBefore of the "next" certificate MUST be set so that
certificate is already valid when it is published at the "star- the certificate is already valid when it is published at the "star-
certificate" URL. Note that the server might need to increase the certificate" URL. Note that the server might need to increase the
auto-renewal lifetime-adjust value to satisfy the latter requirement. auto-renewal lifetime-adjust value to satisfy the latter requirement.
For further rationale on the need for adjusting the certificate For a detailed description of the renewal scheduling logic, see
validity, see Section 4.1. Section 3.5. 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 certificates for this Order with
beyond its auto-renewal end-date. notAfter after the auto-renewal end-date.
Immediately after the Order expires, the server MUST respond with 403 For expired Orders, the server MUST respond with 403 (Forbidden) to
(Forbidden) to any requests to the star-certificate endpoint. The any requests to the star-certificate endpoint. The response SHOULD
response SHOULD provide additional information using a problem provide additional information using a problem document [RFC7807]
document [RFC7807] with type with type "urn:ietf:params:acme:error:autoRenewalExpired". Note that
"urn:ietf:params:acme:error:autoRenewalExpired". Note that the Order the 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 (in addition to POST-as-GET), and a client to enable this service
enable this service with per-Order granularity. 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 allow-certificate-get attribute to true in the auto- setting the allow-certificate-get attribute to true in the auto-
renewal object of the meta field inside the Directory object: renewal object of the meta field inside the Directory object:
o 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 (and HEAD) requests
certificate URLs. to star-certificate URLs.
A client states its will to access the issued star-certificate via A client states its desire to access the issued star-certificate via
unauthenticated GET by adding an allow-certificate-get attribute to unauthenticated GET by adding an allow-certificate-get attribute to
the auto-renewal object of its Order and setting it to true. the auto-renewal object of the payload of its newOrder request and
setting it to true.
o 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 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 (and HEAD) to the star-certificate associated
Order. with this 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.
Note that even when the use of unauthenticated GET has been agreed,
the server MUST also allow POST-as-GET requests to the star-
certificate resource.
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" as the point in time when a new
term certificate for a given STAR Order is due. It is a multiple of short-term certificate for a given STAR Order is due. Its cadence is
the Order's auto-renewal lifetime that starts with the issuance of a multiple of the Order's auto-renewal lifetime that starts with the
the first short-term certificate and is upper-bounded by the Order's issuance of the first short-term certificate and is upper-bounded by
auto-renewal end-date (Figure 6). the Order's auto-renewal end-date (Figure 7).
T - STAR Order's auto-renewal lifetime T - STAR Order's auto-renewal lifetime
end - STAR Order's auto-renewal 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
.- T -. .- T -. .- T -. .__. .- T -. .- T -. .- T -. .__.
/ \ / \ / \ / end / \ / \ / \ / 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 7: 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:
notAfter = min(nrd[i] + T, end) notAfter = min(nrd[i] + T, end)
notBefore = nrd[i] - max(adjust_client, adjust_server) notBefore = nrd[i] - max(adjust_client, adjust_server)
Where "adjust_client" is the min between the auto-renewal lifetime- Where "adjust_client" is the min between the auto-renewal lifetime-
adjust value ("la"), optionally supplied by the client, and the auto- adjust value ("la"), optionally supplied by the client, and the auto-
renewal lifetime of each short-term certificate ("T"); renewal lifetime of each short-term certificate ("T");
skipping to change at page 14, line 12 skipping to change at page 15, line 15
Note that the ACME server MUST NOT set the notBefore of the first 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. 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": { "auto-renewal": {
"start-date": "2016-01-10T00:00:00Z", "start-date": "2019-01-10T00:00:00Z",
"end-date": "2016-01-20T00:00:00Z", "end-date": "2019-01-20T00:00:00Z",
"lifetime": 345600, // 4 days "lifetime": 345600, // 4 days
"lifetime-adjust": 259200 // 3 days "lifetime-adjust": 259200 // 3 days
} }
The amount of time that needs to be subtracted from each nominal The amount of time that needs to be subtracted from each nominal
renewal date is 3 days - i.e., max(min(345600, 259200), 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 |
+----------------------+----------------------+ +----------------------+----------------------+
| 2016-01-10T00:00:00Z | 2016-01-14T00:00:00Z | | 2019-01-10T00:00:00Z | 2019-01-14T00:00:00Z |
| 2016-01-11T00:00:00Z | 2016-01-18T00:00:00Z | | 2019-01-11T00:00:00Z | 2019-01-18T00:00:00Z |
| 2016-01-15T00:00:00Z | 2016-01-20T00:00:00Z | | 2019-01-15T00:00:00Z | 2019-01-20T00:00:00Z |
+----------------------+----------------------+ +----------------------+----------------------+
The value of the notBefore is also the time at which the client The value of the notBefore is also the time at which the client
should expect the new certificate to be available from the star- should expect the new certificate to be available from the star-
certificate endpoint. certificate endpoint.
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
skipping to change at page 15, line 13 skipping to change at page 16, line 16
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, site owners could use the auto-renewal lifetime- server certificate, site owners could use the auto-renewal lifetime-
adjust attribute to control the effective lifetime of their Web adjust attribute to control the effective lifetime of their Web
facing certificates. The exact number depends on the percentage of facing certificates. The exact number depends on the percentage of
the "clock-skewed" population that the site owner expects to protect the "clock-skewed" population that the site owner expects to protect
- 5 days cover 97.3%, 7 days cover 99.6% as well as the nominal auto- - 5 days cover 97.3%, 7 days cover 99.6% - as well as the nominal
renewal lifetime of the STAR Order. Note that exact choice is also auto-renewal lifetime of the STAR Order. Note that exact choice is
likely to depend on the kind of clients that is prevalent for a given also likely to depend on the kinds of client that is prevalent for a
site or app - for example, Android and Mac OS clients are known to given site or app - for example, Android and Mac OS clients are known
behave better than Windows clients. These considerations are clearly to behave better than Windows clients. These considerations are
out of scope of the present document. 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 adjustment 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
skipping to change at page 15, line 51 skipping to change at page 17, line 5
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. HTTP Caching and 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 and especially
servers should consider using the mechanism described in Section 3.4 when multiple endpoints (e.g., a high number of CDN edge nodes) end
to mitigate the risk. up requesting the same certificate. Clients and servers should
consider using the mechanism described in Section 3.4 to mitigate the
risk.
When using unauthenticated GET to fetch the STAR certificate, the When using unauthenticated GET to fetch the STAR certificate, the
server SHALL use the appropriate cache directives to set the server SHALL use the appropriate cache directives to set the
freshness lifetime of the response (Section 5.2 of [RFC7234]) such 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 that on-path caches will consider it stale before or at the time its
effective lifetime is due to expire. 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] and
[I-D.sheffer-acme-star-request].
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
RFCs. Please note that the listing of any individual implementation RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not supplied by IETF contributors. This is not intended as, and must not
skipping to change at page 19, line 5 skipping to change at page 20, line 6
[[RFC Editor: please replace XXXX below by the RFC number.]] [[RFC Editor: please replace XXXX below by the RFC number.]]
6.1. New Registries 6.1. New Registries
This document requests that IANA create the following new registries: This document requests that IANA create the following new registries:
o ACME Order Auto Renewal Fields (Section 6.4) o ACME Order Auto Renewal Fields (Section 6.4)
o ACME Directory Metadata Auto Renewal Fields (Section 6.6) o ACME Directory Metadata Auto Renewal Fields (Section 6.6)
All of these registries are administered under a Specification
Required policy [RFC8126].
6.2. New Error Types 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 |
+-----------------------------------+-------------------+-----------+ +-----------------------------------+-------------------+-----------+
| autoRenewalCanceled | The short-term | RFC XXXX | | autoRenewalCanceled | The short-term | RFC XXXX |
| | certificate is no | | | | certificate is no | |
skipping to change at page 20, line 21 skipping to change at page 21, line 28
Template: Template:
o Field name: The string to be used as a field name in the JSON o Field name: The string to be used as a field name in the JSON
object object
o Field type: The type of value to be provided, e.g., string, o Field type: The type of value to be provided, e.g., string,
boolean, array of string boolean, array of string
o Configurable: Boolean indicating whether the server should accept o Configurable: Boolean indicating whether the server should accept
values provided by the client values provided by the client
o Reference: Where this field is defined o Reference: Where this field is defined
Initial contents: The fields and descriptions defined in
Section 3.1.1.
+-----------------------+------------+--------------+-----------+ +-----------------------+------------+--------------+-----------+
| Field Name | Field Type | Configurable | Reference | | Field Name | Field Type | Configurable | Reference |
+-----------------------+------------+--------------+-----------+ +-----------------------+------------+--------------+-----------+
| start-date | string | true | RFC XXXX | | start-date | string | true | RFC XXXX |
| end-date | string | true | RFC XXXX | | end-date | string | true | RFC XXXX |
| lifetime | integer | true | RFC XXXX | | lifetime | integer | true | RFC XXXX |
| lifetime-adjust | integer | true | RFC XXXX | | lifetime-adjust | integer | true | RFC XXXX |
| allow-certificate-get | boolean | true | RFC XXXX | | allow-certificate-get | boolean | true | RFC XXXX |
+-----------------------+------------+--------------+-----------+ +-----------------------+------------+--------------+-----------+
skipping to change at page 21, line 4 skipping to change at page 22, line 16
Object Object
The "ACME Directory Metadata Auto Renewal Fields" registry lists The "ACME Directory Metadata Auto Renewal Fields" registry lists
field names that are defined for use in the JSON object included in field names that are defined for use in the JSON object included in
the "auto-renewal" field of an ACME directory "meta" object. the "auto-renewal" field of an ACME directory "meta" object.
Template: Template:
o Field name: The string to be used as a field name in the JSON o Field name: The string to be used as a field name in the JSON
object object
o Field type: The type of value to be provided, e.g., string, o Field type: The type of value to be provided, e.g., string,
boolean, array of string boolean, array of string
o Reference: Where this field is defined o Reference: Where this field is defined
Initial contents: The fields and descriptions defined in Section 3.2.
+-----------------------+------------+-----------+ +-----------------------+------------+-----------+
| Field Name | Field Type | Reference | | Field Name | Field Type | Reference |
+-----------------------+------------+-----------+ +-----------------------+------------+-----------+
| min-lifetime | integer | RFC XXXX | | min-lifetime | integer | RFC XXXX |
| max-duration | integer | RFC XXXX | | max-duration | integer | RFC XXXX |
| allow-certificate-get | boolean | RFC XXXX | | allow-certificate-get | boolean | RFC XXXX |
+-----------------------+------------+-----------+ +-----------------------+------------+-----------+
6.7. Cert-Not-Before and Cert-Not-After HTTP Headers 6.7. Cert-Not-Before and Cert-Not-After HTTP Headers
skipping to change at page 21, line 37 skipping to change at page 22, line 50
+-------------------+----------+----------+-----------------------+ +-------------------+----------+----------+-----------------------+
7. Security Considerations 7. Security Considerations
7.1. No revocation 7.1. No revocation
STAR certificates eliminate an important security feature of PKI STAR certificates eliminate an important security feature of PKI
which is the ability to revoke certificates. Revocation allows the which is the ability to revoke certificates. Revocation allows the
administrator to limit the damage done by a rogue node or an administrator to limit the damage done by a rogue node or an
adversary who has control of the private key. With STAR adversary who has control of the private key. With STAR
certificates, expiration replaces revocation so there is a timeliness certificates, expiration replaces revocation so there is potential
issue. To that end, see also the discussion on clock skew in for lack of timeliness in the revocation taking effect. To that end,
Section 4.1. see also the discussion on clock skew in Section 4.1.
It should be noted that revocation also has timeliness issues, It should be noted that revocation also has timeliness issues,
because both CRLs and OCSP responses have nextUpdate fields that tell because both CRLs and OCSP responses have nextUpdate fields that tell
relying parties (RPs) how long they should trust this revocation relying parties (RPs) how long they should trust this revocation
data. These fields are typically set to hours, days, or even weeks data. These fields are typically set to hours, days, or even weeks
in the future. Any revocation that happens before the time in in the future. Any revocation that happens before the time in
nextUpdate goes unnoticed by the RP. nextUpdate goes unnoticed by the RP.
One situation where the lack of explicit revocation could create a
security risk to the IdO is when the Order is created with start-date
some appreciable amount of time in the future. Recall that when
authorizations have been fulfilled, the Order moves to the "valid"
state and the star-certificate endpoint is populated with the first
cert (Figure 4). So, if an attacker manages to get hold of the
private key as well as of the first (post-dated) certificate, there
is a time window in the future when they will be able to successfully
impersonate the IdO. Note that cancellation is pointless in this
case. In order to mitigate the described threat, it is RECOMMENDED
that IdO place their Orders at a time that is close to the Order's
start-date.
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 auto-renewal "lifetime" parameter. An certificates, depending on the auto-renewal "lifetime" parameter. An
skipping to change at page 22, line 26 skipping to change at page 23, line 49
retrieve the certificates periodically. If this resource is external retrieve the certificates periodically. If this resource is external
to the CA (e.g. a hosted web server), the previous attack will be to the CA (e.g. a hosted web server), the 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 auto-renewal behavior cannot initial request, by the nature of the auto-renewal behavior cannot
solve the above problem. The CA server needs complementary solve the above problem. The CA server needs complementary
mitigation and specifically, it SHOULD enforce a minimum value on mitigation and specifically, it SHOULD enforce a minimum value on
auto-renewal "lifetime". 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. Note that this limit
has to take account of already-scheduled renewal issuances as well as
new incoming requests.
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 Richard Barnes, Roman Danyliw, Jon Peterson, Eric Rescorla, Thanks to Ben Kaduk, Richard Barnes, Roman Danyliw, Jon Peterson,
Ryan Sleevi, Sean Turner, Martin Thomson and Mehmet Ersue for helpful Eric Rescorla, Ryan Sleevi, Sean Turner, Alexey Melnikov, Adam Roach,
comments and discussions that have shaped this document. Martin Thomson and Mehmet Ersue for helpful 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>.
skipping to change at page 23, line 29 skipping to change at page 25, line 5
[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, [RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching", Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
RFC 7234, DOI 10.17487/RFC7234, June 2014, RFC 7234, DOI 10.17487/RFC7234, June 2014,
<https://www.rfc-editor.org/info/rfc7234>. <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>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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
(ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019, (ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019,
<https://www.rfc-editor.org/info/rfc8555>. <https://www.rfc-editor.org/info/rfc8555>.
9.2. Informative References 9.2. Informative References
skipping to change at page 24, line 32 skipping to change at page 26, line 13
October 2015, <https://www.rfc-editor.org/info/rfc7633>. October 2015, <https://www.rfc-editor.org/info/rfc7633>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205, Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016, RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>. <https://www.rfc-editor.org/info/rfc7942>.
[Stark] Stark, E., Huang, L., Israni, D., Jackson, C., and D. [Stark] Stark, E., Huang, L., Israni, D., Jackson, C., and D.
Boneh, "The case for prefetching and prevalidating TLS Boneh, "The case for prefetching and prevalidating TLS
server certificates", 2012, server certificates", 2012,
<http://crypto.stanford.edu/~dabo/pubs/abstracts/ <http://crypto.stanford.edu/~dabo/pubs/abstracts/ssl-
ssl-prefetch.html>. prefetch.html>.
[Topalovic] [Topalovic]
Topalovic, E., Saeta, B., Huang, L., Jackson, C., and D. Topalovic, E., Saeta, B., Huang, L., Jackson, C., and D.
Boneh, "Towards Short-Lived Certificates", 2012, Boneh, "Towards Short-Lived Certificates", 2012,
<http://www.ieee-security.org/TC/W2SP/2012/papers/ <http://www.ieee-security.org/TC/W2SP/2012/papers/
w2sp12-final9.pdf>. w2sp12-final9.pdf>.
[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-09 A.1. draft-ietf-acme-star-10
IESG processing:
o More clarity on IANA registration (Alexey);
o HTTP header requirements adjustments (Adam);
o Misc editorial (Ben)
A.2. draft-ietf-acme-star-09
Richard and Ryan's review resulted in the following updates: Richard and Ryan's review resulted in the following updates:
o STAR Order and Directory Meta attributes renamed slightly and o STAR Order and Directory Meta attributes renamed slightly and
grouped under two brand new "auto-renewal" objects; grouped under two brand new "auto-renewal" objects;
o IANA registration updated accordingly (note that two new o IANA registration updated accordingly (note that two new
registries have been added as a consequence); registries have been added as a consequence);
o Unbounded pre-dating of certificates removed so that STAR certs o Unbounded pre-dating of certificates removed so that STAR certs
are never issued with their notBefore in the past; are never issued with their notBefore in the past;
o Changed "recurrent" to "autoRenewal" in error codes; o Changed "recurrent" to "autoRenewal" in error codes;
o Changed "recurrent" to "auto-renewal" in reference to Orders; o Changed "recurrent" to "auto-renewal" in reference to Orders;
o Added operational considerations for HTTP caches. o Added operational considerations for HTTP caches.
A.2. draft-ietf-acme-star-08 A.3. 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.3. draft-ietf-acme-star-07 A.4. 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.4. draft-ietf-acme-star-06 A.5. draft-ietf-acme-star-06
o Roman's AD review o Roman's AD review
A.5. draft-ietf-acme-star-05 A.6. 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.6. draft-ietf-acme-star-04 A.7. 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.7. draft-ietf-acme-star-03 A.8. 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.8. draft-ietf-acme-star-02 A.9. 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.9. draft-ietf-acme-star-01 A.10. 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.10. draft-ietf-acme-star-00 A.11. 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.11. draft-sheffer-acme-star-02 A.12. 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.12. draft-sheffer-acme-star-01 A.13. draft-sheffer-acme-star-01
o A terminology section. o A terminology section.
o Some cleanup. o Some cleanup.
A.13. draft-sheffer-acme-star-00 A.14. 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.14. draft-sheffer-acme-star-lurk-00 A.15. 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
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