Network Working Group                                            E. Lear
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                        January 19, 2016
Expires: July 22, 2016


                 Using DNS Names in the IETF ACL Model
                 draft-lear-ietf-netmod-acl-dnsname-00

Abstract

   End points are commonly referenced by higher level functions through
   the DNS.  This is especially the case in cloud-based functions, which
   might have hundreds of IP addresses for the same name.  This brief
   memo extends the IETF-ACL model to allow access-control via domain
   names.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on July 22, 2016.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Element Definitions . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  source-dnsname  . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  destination-dnsname . . . . . . . . . . . . . . . . . . .   3
   3.  The ietf-acl-dnsname Model  . . . . . . . . . . . . . . . . .   3
   4.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The IETF-ACL model [I-D.ietf-netmod-acl-model] specifies a schema for
   access lists.  That model is intentionally kept constrained to the
   small number of packet-passing functions that are considered
   ubiquitous.  While that is a necessary step, there are a number of
   circumstances in which it will not be sufficient.  In a world where
   load balancing and shifting commonly takes place, it may not be
   practical to maintain the complete list of IP addresses in all
   instances.  Furthermore, even in more static environments,
   occasionally the name to address mapping needs to change.  Lastly,
   there are resources that may not be tied to packet processing at all
   that may yet be well described by this augmentation.  Allowing domain
   names in ACLs reduces the number of points within a network that need
   to be reconfigured when such changes take place.

   This memo specifies an extension to IETF-ACL model such that domain
   names may be referenced by augmenting the "matches" element.
   Different implementations may deploy differing methods to maintain
   the mapping between IP address and domain name, if indeed any are
   needed.  However, the intent is that resources that are referred to
   using a name should be authorized (or not) within an access list.

   The structure of the change is as follows:

      augment
      /acl:access-lists/acl:acl/acl:access-list-entries
         /acl:ace/acl:matches/acl:ace-type/acl:ace-ip:
         +--rw source-dnsname?        inet:host
         +--rw destination-dnsname?   inet:host

   The choice of this particular point in the access-list model is based
   on the assumption that we are in some way referring to IP-related




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   resources, as that is what the DNS returns.  A domain name in our
   context is defined in [RFC6991].

2.  Element Definitions

   The following elements are defined.

2.1.  source-dnsname

   The argument corresponds to a domain name of a source as specified by
   inet:host.  Depending on how the model is used, it may or may not be
   resolved, as required by the implementation and circumstances.

2.2.  destination-dnsname

   The argument corresponds to a domain name of a destination as
   specified by inet:host.  Depending on how the model is used, it may
   or may not be resolved, as required by the implementation and
   circumstances.

3.  The ietf-acl-dnsname Model

   <CODE BEGINS>file "ietf-acl-dnsname.yang";

   module ietf-acl-dnsname {
     yang-version 1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-acl-dnsname";
     prefix "ietf-acl-dnsname";


     import ietf-access-control-list {
       prefix "acl";
     }

     import ietf-inet-types
     {
       prefix "inet";
     }

     organization
       "Cisco Systems, Inc.";

     contact
       "Eliot Lear
        lear@cisco.com
       ";

     description



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       "This YANG module defines a component that augments the
        IETF description of an access list to allow dns names
        as matching criteria.";

     revision "2016-01-14"  {
       description "Initial revision";
       reference "This document?";
     }

     augment "/acl:access-lists/acl:acl/" +
        "acl:access-list-entries/acl:ace/" +
        "acl:matches/acl:ace-type/acl:ace-ip" {
       description "adding domain names to matching";

       leaf source-dnsname {
         type inet:host;
         description "domain name to be matched against";
       }
       leaf destination-dnsname {
         type inet:host;
         description "domain name to be matched against";
       }
     }

   }

   <CODE ENDS>

4.  Example

   The following example is taken from [I-D.ietf-netmod-acl-model] (the
   optional and irrelevant components have been removed).  It allows
   traffic from www.cloud.example.com.


















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<?xml version='1.0' encoding='UTF-8'?>
  <data xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
  <access-lists
   xmlns="urn:ietf:params:xml:ns:yang:ietf-access-control-list"
  xmlns:ietf-acl-dnsname="urn:ietf:params:xml:ns:yang:ietf-acl-dnsname">
       <acl>
        <acl-oper-data />
        <access-list-entries>
          <ace>
            <matches>
          <source-dnsname>
             www.cloud.example.com
          </destination-dnsname>
            </matches>
            <actions>
              <permit />
            </actions>
            <rule-name>rule1<rule-name/>
          </ace>
        </access-list-entries>
        <acl-name>sample-dns-acl<acl-name/>
        <acl-type>ipv4-acl<acl-type/>
      </acl>
    </access-lists>
  </data>

5.  Security Considerations

   If the mapping between a domain name and the underlying resource to
   which it refers becomes stale, the access list will be incorrect.  It
   is therefore important that implementations employ some means for
   maintaining the mapping, if it is required.  In those circumstances,
   when other systems are in play, those other systems would be required
   to indicate what domains they are attempting to connect to.  Under
   the current circumstances, this is readily observable.  However, in
   future such information sharing may raise privacy concerns, and the
   name and mapping may not be available to the system employing the ACL
   model.

6.  IANA Considerations

   The IANA is not requested to make any changes.  The RFC Editor is
   requested to remove this section prior to publication.








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7.  Acknowledgments

   The author wishes to acknowledge Kiran Koushik and Einar Nilsen-
   Nygaard for their review and contributions to this work.

8.  Normative References

   [I-D.ietf-netmod-acl-model]
              Bogdanovic, D., Koushik, K., Huang, L., and D. Blair,
              "Network Access Control List (ACL) YANG Data Model",
              draft-ietf-netmod-acl-model-06 (work in progress),
              December 2015.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types", RFC
              6991, DOI 10.17487/RFC6991, July 2013,
              <http://www.rfc-editor.org/info/rfc6991>.

Author's Address

   Eliot Lear
   Cisco Systems
   Richtistrasse 7
   Wallisellen  CH-8304
   Switzerland

   Phone: +41 44 878 9200
   Email: lear@cisco.com
























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