Automated Certificate Management Environment J. Crawford Internet-Draft A. Chen Intended status: Informational H. Shafagh Expires: 20 July 2025 Netflix 16 January 2025 Delegated http-01 Validation in ACME Protocol draft-crawford-acme-delegated-http-latest Abstract This document proposes an extension to the Automated Certificate Management Environment (ACME) !RFC8555 protocol to enhance the http-01 challenge type (see Section 8.3 of [RFC8555]) by allowing for delegation, enabling validation requests to be directed to a designated server. This approach mirrors the functionality available with dns-01 (see Section 8.4 of [RFC8555]) challenges via DNS CNAME records, aiming to improve the flexibility and scalability of the http-01 validation method. About This Document This note is to be removed before publishing as an RFC. The latest revision of this draft can be found at https://jmcrawford45.github.io/draft-crawford-acme-delegated-http/ draft-crawford-acme-delegated-http.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft- crawford-acme-delegated-http/. Discussion of this document takes place on the Automated Certificate Management Environment mailing list (mailto:acme@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/acme/. Subscribe at https://www.ietf.org/mailman/listinfo/acme/. Source for this draft and an issue tracker can be found at https://github.com/jmcrawford45/draft-crawford-acme-delegated-http. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 20 July 2025. Copyright Notice Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction 2. Conventions and Definitions 3. Delegated HTTP Validation 4. Security Considerations 5. IANA Considerations 6. Normative References Acknowledgments Authors' Addresses 1. Introduction The ACME protocol provides mechanisms for validating domain control using several challenge types, including http-01 and dns-01. While dns-01 challenges allow for delegation using DNS CNAME records, http-01 challenges require direct hosting of challenge responses on the domain being validated. This document introduces a mechanism to delegate http-01 validation requests to a designated server. By leveraging DNS records to redirect HTTP validation, this proposal enables http-01 validation while addressing challenges associated with validating domains hosted on corporate networks, on load balancers, or behind firewalls. Delegated HTTP validation combines the following benefits from the existing dns-01 and http-01 validation methods. * *Centralized Management*: Enables centralized management of challenge responses, reducing the complexity of managing multiple domains. * *Reduced Exposure*: Eliminates the need for direct access to the primary web server for validation. * *Performance*: Reduces latency compared to dns-01 challenges by allowing synchronous validation. * *Security*: Avoids risks associated with exposing DNS API credentials. * *Scalability*: Enables parallelized validation of domains on distributed load balancers. 2. Conventions and Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 3. Delegated HTTP Validation This proposal extends the http-01 challenge type to support delegation using a DNS record, similar to the approach used for dns-01 challenges. The process for validating example.com is as follows: 1. *DNS Configuration*: The domain owner creates a DNS record for _acme-challenge.example.com pointing to a server capable of serving HTTP validation requests. For example: _acme-challenge.example.com. CNAME validation-server- example.net. 2. *Challenge File Provisioning*: The designated server hosts the challenge file at the path /.well-known/acme-challenge/{token}, containing the domain authorization string. 3. *Validation Request*: The ACME server attempts validation in the following order: * http://_acme-challenge.example.com/.well-known/acme- challenge/{token} * http://example.com/.well-known/acme-challenge/{token} An ACME server MUST try the undelegated URL if the delegated URL fails. 4. *Validation Response*: The designated server responds with the authorization string, which the ACME server verifies against the expected value. 5. *Challenge Completion*: If the validation succeeds, the challenge status is updated to “valid.” If it fails, the status is updated to “invalid,” with diagnostic information provided. 4. Security Considerations * Relies on the security of both DNS and the delegated server. 5. IANA Considerations TODO: https://github.com/jmcrawford45/draft-crawford-acme-delegated- http/issues/1 6. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8555] Barnes, R., Hoffman-Andrews, J., McCarney, D., and J. Kasten, "Automatic Certificate Management Environment (ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019, . Acknowledgments TODO acknowledge. Authors' Addresses Jared Crawford Netflix Email: jmcrawford45@gmail.com Andrew Chen Netflix Email: achen.code@gmail.com Hoss Shafagh Netflix Email: hoss.sha@gmail.com