draft-ietf-acme-tls-alpn-01.txt   draft-ietf-acme-tls-alpn-02.txt 
ACME Working Group R. Shoemaker ACME Working Group R. Shoemaker
Internet-Draft ISRG Internet-Draft ISRG
Intended status: Standards Track May 30, 2018 Intended status: Standards Track August 13, 2018
Expires: December 1, 2018 Expires: February 14, 2019
ACME TLS ALPN Challenge Extension ACME TLS ALPN Challenge Extension
draft-ietf-acme-tls-alpn-01 draft-ietf-acme-tls-alpn-02
Abstract Abstract
This document specifies a new challenge for the Automated Certificate This document specifies a new challenge for the Automated Certificate
Management Environment (ACME) protocol which allows for domain Management Environment (ACME) protocol which allows for domain
control validation using TLS. control validation using TLS.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
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 December 1, 2018. This Internet-Draft will expire on February 14, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 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. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. TLS with Application Level Protocol Negotiation (TLS ALPN) 3. TLS with Application Level Protocol Negotiation (TLS ALPN)
Challenge . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Challenge . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. acme-tls/1 Protocol Definition . . . . . . . . . . . . . 5 3.1. acme-tls/1 Protocol Definition . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5.1. SMI Security for PKIX Certificate Extension OID . . . . . 6 5.1. SMI Security for PKIX Certificate Extension OID . . . . . 6
5.2. ALPN Protocol ID . . . . . . . . . . . . . . . . . . . . 6 5.2. ALPN Protocol ID . . . . . . . . . . . . . . . . . . . . 6
5.3. ACME Validation Method . . . . . . . . . . . . . . . . . 6 5.3. ACME Validation Method . . . . . . . . . . . . . . . . . 6
6. Appendix: Design Rationale . . . . . . . . . . . . . . . . . 6 6. Appendix: Design Rationale . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
8. Normative References . . . . . . . . . . . . . . . . . . . . 7 8. Normative References . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
The Automatic Certificate Management Environment (ACME) The Automatic Certificate Management Environment (ACME)
[I-D.ietf-acme-acme] standard specifies methods for validating [I-D.ietf-acme-acme] standard specifies methods for validating
control of domain names via HTTP and DNS. Deployment experience has control of domain names via HTTP and DNS. Deployment experience has
shown it is also useful to be able to validate domain control using shown it is also useful to be able to validate domain control using
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This challenge requires negotiating a new application-layer protocol This challenge requires negotiating a new application-layer protocol
using the TLS Application-Layer Protocol Negotiation (ALPN) Extension using the TLS Application-Layer Protocol Negotiation (ALPN) Extension
[RFC7301]. Because no existing software implements this protocol, [RFC7301]. Because no existing software implements this protocol,
the ability to fulfill TLS-ALPN-01 challenges is effectively opt-in. the ability to fulfill TLS-ALPN-01 challenges is effectively opt-in.
A service provider must proactively deploy new code in order to A service provider must proactively deploy new code in order to
implement TLS-ALPN-01, so we can specify stronger controls in that implement TLS-ALPN-01, so we can specify stronger controls in that
code, resulting in a stronger validation method. code, resulting in a stronger validation method.
2. Terminology 2. Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119 "OPTIONAL" in this document are to be interpreted as described in BCP
[RFC2119]. 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. TLS with Application Level Protocol Negotiation (TLS ALPN) Challenge 3. TLS with Application Level Protocol Negotiation (TLS ALPN) Challenge
The TLS with Application Level Protocol Negotiation (TLS ALPN) The TLS with Application Level Protocol Negotiation (TLS ALPN)
validation method proves control over a domain name by requiring the validation method proves control over a domain name by requiring the
client to configure a TLS server to respond to specific connection client to configure a TLS server to respond to specific connection
attempts utilizing the ALPN extension with identifying information. attempts utilizing the ALPN extension with identifying information.
The ACME server validates control of the domain name by connecting to The ACME server validates control of the domain name by connecting to
a TLS server at one of the addresses resolved for the domain name and a TLS server at one of the addresses resolved for the domain name and
verifying that a certificate with specific content is presented. verifying that a certificate with specific content is presented.
type (required, string): The string "tls-alpn-01" type (required, string): The string "tls-alpn-01"
token (required, string): A random value that uniquely identifies token (required, string): A random value that uniquely identifies
the challenge. This value MUST have at least 128 bits of entropy. the challenge. This value MUST have at least 128 bits of entropy.
It MUST NOT contain any characters outside the base64url alphabet, It MUST NOT contain any characters outside the base64url alphabet,
including padding characters ("="). including padding characters ("="). See [RFC4086] for additional
information on randomness requirements.
GET /acme/authz/1234/1 HTTP/1.1 GET /acme/authz/1234/1 HTTP/1.1
Host: example.com Host: example.com
HTTP/1.1 200 OK HTTP/1.1 200 OK
{ {
"type": "tls-alpn-01", "type": "tls-alpn-01",
"url": "https://example.com/acme/authz/1234/1", "url": "https://example.com/acme/authz/1234/1",
"status": "pending", "status": "pending",
"token": "evaGxfADs6pSRb2LAv9IZf17Dt3juxGJ-PCt92wr-oA" "token": "evaGxfADs6pSRb2LAv9IZf17Dt3juxGJ-PCt92wr-oA"
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The client prepares for validation by constructing a self-signed The client prepares for validation by constructing a self-signed
certificate which MUST contain a acmeValidation-v1 extension and a certificate which MUST contain a acmeValidation-v1 extension and a
subjectAlternativeName extension [RFC5280]. The subjectAlternativeName extension [RFC5280]. The
subjectAlternativeName extension MUST contain a single dNSName entry subjectAlternativeName extension MUST contain a single dNSName entry
where the value is the domain name being validated. The where the value is the domain name being validated. The
acmeValidation-v1 extension MUST contain the SHA-256 digest acmeValidation-v1 extension MUST contain the SHA-256 digest
[FIPS180-4] of the key authorization [I-D.ietf-acme-acme] for the [FIPS180-4] of the key authorization [I-D.ietf-acme-acme] for the
challenge. The acmeValidation extension MUST be critical so that the challenge. The acmeValidation extension MUST be critical so that the
certificate isn't inadvertently used by non-ACME software. certificate isn't inadvertently used by non-ACME software.
id-pe-acmeIdentifier OBJECT IDENTIFIER ::= { id-pe 30 } id-pe-acmeIdentifier OBJECT IDENTIFIER ::= { id-pe 31 }
id-pe-acmeIdentifier-v1 OBJECT IDENTIFIER ::= { id-pe-acmeIdentifier 1 } id-pe-acmeIdentifier-v1 OBJECT IDENTIFIER ::= { id-pe-acmeIdentifier 1 }
acmeValidation-v1 ::= OCTET STRING (SIZE (32)) acmeValidation-v1 ::= OCTET STRING (SIZE (32))
Once this certificate has been created it MUST be provisioned such Once this certificate has been created it MUST be provisioned such
that it is returned during a TLS handshake that contains a ALPN that it is returned during a TLS handshake that contains a ALPN
extension containing the value "acme-tls/1" and a SNI extension extension containing the value "acme-tls/1" and a SNI extension
containing the domain name being validated. containing the domain name being validated.
A client responds with an empty object ({}) to acknowledge that the A client responds with an empty object ({}) to acknowledge that the
challenge is ready to be validated by the server. challenge is ready to be validated by the server. The base64url
encoding of the protected headers and payload is described in
[I-D.ietf-acme-acme] Section 6.1.
POST /acme/authz/1234/1 POST /acme/authz/1234/1
Host: example.com Host: example.com
Content-Type: application/jose+json Content-Type: application/jose+json
{ {
"protected": base64url({ "protected": base64url({
"alg": "ES256", "alg": "ES256",
"kid": "https://example.com/acme/acct/1", "kid": "https://example.com/acme/acct/1",
"nonce": "JHb54aT_KTXBWQOzGYkt9A", "nonce": "JHb54aT_KTXBWQOzGYkt9A",
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To further mitigate the risk of users claiming domain names used by To further mitigate the risk of users claiming domain names used by
other users on the same infrastructure hosting providers, CDNs, and other users on the same infrastructure hosting providers, CDNs, and
other service providers should not allow users to provide their own other service providers should not allow users to provide their own
certificates for the TLS ALPN validation process. If providers wish certificates for the TLS ALPN validation process. If providers wish
to implement TLS ALPN validation they SHOULD only generate to implement TLS ALPN validation they SHOULD only generate
certificates used for validation themselves and not expose this certificates used for validation themselves and not expose this
functionality to users. functionality to users.
5. IANA Considerations 5. IANA Considerations
[[RFC Editor: please replace XXXX below by the RFC number.]]
5.1. SMI Security for PKIX Certificate Extension OID 5.1. SMI Security for PKIX Certificate Extension OID
Within the SMI-numbers registry, the "SMI Security for PKIX Within the SMI-numbers registry, the "SMI Security for PKIX
Certificate Extension (1.3.6.1.5.5.7.1)" table is to be updated to Certificate Extension (1.3.6.1.5.5.7.1)" table is to be updated to
add the following entry: add the following entry:
+---------+----------------------+------------+ +---------+----------------------+------------+
| Decimal | Description | References | | Decimal | Description | References |
+---------+----------------------+------------+ +---------+----------------------+------------+
| 30 | id-pe-acmeIdentifier | RFC XXXX | | 30 | id-pe-acmeIdentifier | RFC XXXX |
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[FIPS180-4] [FIPS180-4]
Department of Commerce, National., "NIST FIPS 180-4, Department of Commerce, National., "NIST FIPS 180-4,
Secure Hash Standard", March 2012, Secure Hash Standard", March 2012,
<http://csrc.nist.gov/publications/fips/fips180-4/ <http://csrc.nist.gov/publications/fips/fips180-4/
fips-180-4.pdf>. fips-180-4.pdf>.
[I-D.ietf-acme-acme] [I-D.ietf-acme-acme]
Barnes, R., Hoffman-Andrews, J., McCarney, D., and J. Barnes, R., Hoffman-Andrews, J., McCarney, D., and J.
Kasten, "Automatic Certificate Management Environment Kasten, "Automatic Certificate Management Environment
(ACME)", draft-ietf-acme-acme-12 (work in progress), April (ACME)", draft-ietf-acme-acme-14 (work in progress),
2018. August 2018.
[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>.
[RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode [RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode
for Internationalized Domain Names in Applications for Internationalized Domain Names in Applications
(IDNA)", RFC 3492, DOI 10.17487/RFC3492, March 2003, (IDNA)", RFC 3492, DOI 10.17487/RFC3492, March 2003,
<https://www.rfc-editor.org/info/rfc3492>. <https://www.rfc-editor.org/info/rfc3492>.
[RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker,
"Randomness Requirements for Security", BCP 106, RFC 4086,
DOI 10.17487/RFC4086, June 2005,
<https://www.rfc-editor.org/info/rfc4086>.
[RFC4343] Eastlake 3rd, D., "Domain Name System (DNS) Case [RFC4343] Eastlake 3rd, D., "Domain Name System (DNS) Case
Insensitivity Clarification", RFC 4343, Insensitivity Clarification", RFC 4343,
DOI 10.17487/RFC4343, January 2006, DOI 10.17487/RFC4343, January 2006,
<https://www.rfc-editor.org/info/rfc4343>. <https://www.rfc-editor.org/info/rfc4343>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>. <https://www.rfc-editor.org/info/rfc5280>.
skipping to change at page 8, line 31 skipping to change at page 8, line 41
[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS) [RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
Extensions: Extension Definitions", RFC 6066, Extensions: Extension Definitions", RFC 6066,
DOI 10.17487/RFC6066, January 2011, DOI 10.17487/RFC6066, January 2011,
<https://www.rfc-editor.org/info/rfc6066>. <https://www.rfc-editor.org/info/rfc6066>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan, [RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol "Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301, Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/info/rfc7301>. July 2014, <https://www.rfc-editor.org/info/rfc7301>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
Author's Address Author's Address
Roland Bracewell Shoemaker Roland Bracewell Shoemaker
Internet Security Research Group Internet Security Research Group
Email: roland@letsencrypt.org Email: roland@letsencrypt.org
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