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Versions: (draft-shoemaker-acme-ip) 00

ACME Working Group                                          R. Shoemaker
Internet-Draft                                                      ISRG
Intended status: Standards Track                           July 16, 2017
Expires: January 17, 2018


                ACME IP Identifier Validation Extension
                         draft-ietf-acme-ip-00

Abstract

   This document specifies identifiers and challenges required to enable
   the Automated Certificate Management Environment (ACME) to issue
   certificates for IP addresses.

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
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   This Internet-Draft will expire on January 17, 2018.

Copyright Notice

   Copyright (c) 2017 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
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   described in the Simplified BSD License.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  IP Identifier . . . . . . . . . . . . . . . . . . . . . . . .   2
   4.  Identifier Validation Challenges  . . . . . . . . . . . . . .   3
     4.1.  Reverse DNS . . . . . . . . . . . . . . . . . . . . . . .   3
     4.2.  Existing Challenges . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Identifier Types  . . . . . . . . . . . . . . . . . . . .   5
     5.2.  Challenge Types . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
     6.1.  Certificate Lifetime  . . . . . . . . . . . . . . . . . .   5
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   The Automatic Certificate Management Environment (ACME)
   [I-D.ietf-acme-acme] only defines challenges for validating control
   of DNS host name identifiers which limits its use to being used for
   issuing certificates for these identifiers.  In order to allow
   validation of IPv4 and IPv6 identifiers for inclusion in X.509
   certificates this document defines a new challenge type and specifies
   how challenges defined in the original ACME specification can be used
   to validate IP identifiers.

2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
   and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119
   [RFC2119] and indicate requirement levels for compliant ACME-Wildcard
   implementations.

3.  IP Identifier

   ACME only defines the identifier type "dns" which is used to refer to
   fully qualified domain names.  If a ACME server wishes to request
   proof that a user controls a IPv4 or IPv6 address it MUST create an
   authorization with the identifier type "ip".  The value field of the
   identifier MUST contain the textual form of the address as defined in
   RFC 1123 [RFC1123] Section 2.1 for IPv4 and in RFC 4291 [RFC4291]
   Section 2.2 for IPv6.

   An identifier for the IPv6 address 2001:db8::1 would be formatted
   like so:




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   {"type": "ip", "value": "2001:db8::1"}

4.  Identifier Validation Challenges

   When creating an authorization for a identifier with the type "ip"
   the following challenge types MAY be used to perform validation.

4.1.  Reverse DNS

   With Reverse DNS validation the client proves control of an IP
   address by provisioning a TXT resource record containing a designated
   value for a specific validation domain name constructed using the
   value of the PTR record for the reverse mapping of the address.

   type (required, string):  The string "reverse-dns-01".

   token (required, string):  A random value that uniquely identifies
      the challenge.  This value MUST have at least 128 bits of entropy,
      in order to prevent an attacker from guessing it.  It MUST NOT
      contain any characters outside the base64url [RFC4648] alphabet,
      including padding characters ("=").

   GET /acme/authz/1234/2 HTTP/1.1
   Host: example.com

   HTTP/1.1 200 OK
   {
     "type": "reverse-dns-01",
     "url": "https://example.com/acme/authz/1234/2",
     "status": "pending",
     "token": "evaGxfADs6pSRb2LAv9IZf17Dt3juxGJ-PCt92wr-oA"
   }

   A client responds to this challenge by constructing a key
   authorization from the "token" value provided in the challenge and
   the client's ACME account key.  The client then computes the SHA-256
   digest [FIPS180-4] of the key authorization.  The record provisioned
   to the authoritative DNS server is the base64url encoding of this
   digest.

   The client constructs the validation domain name by prepending the
   label "_acme-challenge" to the domain name referenced in the PTR
   resource record for the IN-ADDR.ARPA [RFC1034] or IP6.ARPA [RFC3596]
   reverse mapping of the IP address.  The client then provisions a TXT
   record with the digest for this name.

   For example, if the IP address being validated is 2001:db8::1 and its
   IP6.ARPA mapping had the following PTR record:



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1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa. 300 IN PTR example.com

   then the client would provision the following DNS record:

   _acme-challenge.example.com. 300 IN TXT "gfj9Xq...Rg85nM"

   The response to the Reverse DNS challenge provides the computed key
   authorization to acknowledge that the client is ready to fulfill this
   challenge.

   keyAuthorization (required, string):  The key authorization for this
      challenge.

   POST /acme/authz/1234/2
   Host: example.com
   Content-Type: application/jose+json

   {
     "protected": base64url({
       "alg": "ES256",
       "kid": "https://example.com/acme/acct/1",
       "nonce": "JHb54aT_KTXBWQOzGYkt9A",
       "url": "https://example.com/acme/authz/1234/2"
     }),
     "payload": base64url({
       "keyAuthorization": "evaGxfADs...62jcerQ"
     }),
     "signature": "Q1bURgJoEslbD1c5...3pYdSMLio57mQNN4"
   }

   On receiving a response, the server MUST verify that the key
   authorization in the response matches the "token" value in the
   challenge and the client's ACME account key.  If they do not match,
   then the server MUST return an HTTP error in response to the POST
   request in which the client sent the challenge.

   To validate a DNS challenge, the server performs the following steps:

   1.  Compute the SHA-256 digest of the key authorization

   2.  Query for a PTR record for the IP identifiers relevant reverse
       mapping based on its version

   3.  Query for TXT records for the computed validation domain name

   4.  Verify that the contents of one of the TXT records matches the
       digest value




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   If all of the above verifications succeed, then the validation is
   successful.  If no PTR or TXT DNS records are found, or the returned
   TXT records do not contain the expected key authorization digest,
   then the validation fails.

4.2.  Existing Challenges

   IP identifiers MAY be used with the existing "http-01" and "tls-sni-
   02" challenges from RFC XXXX Sections XXX and XXX respectively.  To
   use IP identifiers with these challenges their initial DNS resolution
   step MUST be skipped and the address used for validation MUST be the
   value of the identifier.  For the "http-01" challenge the Host header
   should be set to the IP address being used for validation per RFC
   7230.

   The existing "dns-01" challenge MUST NOT be used to validate IP
   identifiers.

5.  IANA Considerations

5.1.  Identifier Types

   Adds a new type to the Identifier list defined in Section XXX of RFC
   XXXX with the label "ip" and reference RFC XXXX.

5.2.  Challenge Types

   Adds a new type to the Challenge list defined in Section XXX of RFC
   XXXX with the label "reverse-dns-01", identifier type "ip", and
   reference RFC XXXX.

   Add the value "ip" to the identifier type column for the "http-01"
   and "tls-sni-02" challenges.

6.  Security Considerations

6.1.  Certificate Lifetime

   Given the often short delegation periods for IP addresses provided by
   various service providers CAs MAY want to impose shorter lifetimes
   for certificates which contain IP identifiers.  They MAY also impose
   restrictions on IP identifiers which are in CIDRs known to be
   assigned to service providers who dynamically assign addresses to
   users for indeterminate periods of time.







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7.  Normative References

   [FIPS180-4]
              Department of Commerce, National., "NIST FIPS 180-4,
              Secure Hash Standard", March 2012,
              <http://csrc.nist.gov/publications/fips/fips180-4/
              fips-180-4.pdf>.

   [I-D.ietf-acme-acme]
              Barnes, R., Hoffman-Andrews, J., and J. Kasten, "Automatic
              Certificate Management Environment (ACME)", draft-ietf-
              acme-acme-07 (work in progress), June 2017.

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <http://www.rfc-editor.org/info/rfc1034>.

   [RFC1123]  Braden, R., Ed., "Requirements for Internet Hosts -
              Application and Support", STD 3, RFC 1123,
              DOI 10.17487/RFC1123, October 1989,
              <http://www.rfc-editor.org/info/rfc1123>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC3596]  Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,
              "DNS Extensions to Support IP Version 6", STD 88,
              RFC 3596, DOI 10.17487/RFC3596, October 2003,
              <http://www.rfc-editor.org/info/rfc3596>.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, DOI 10.17487/RFC4291, February
              2006, <http://www.rfc-editor.org/info/rfc4291>.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
              <http://www.rfc-editor.org/info/rfc4648>.

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <http://www.rfc-editor.org/info/rfc7230>.







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Author's Address

   Roland Bracewell Shoemaker
   Internet Security Research Group

   Email: roland@letsencrypt.org













































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