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 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 http://datatracker.ietf.org/drafts/current/. 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Lear Expires July 22, 2016 [Page 1] Internet-Draft DNS in ACLs January 2016 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 Lear Expires July 22, 2016 [Page 2] Internet-Draft DNS in ACLs January 2016 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 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 Lear Expires July 22, 2016 [Page 3] Internet-Draft DNS in ACLs January 2016 "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"; } } } 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. Lear Expires July 22, 2016 [Page 4] Internet-Draft DNS in ACLs January 2016 www.cloud.example.com rule1 sample-dns-acl ipv4-acl 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. Lear Expires July 22, 2016 [Page 5] Internet-Draft DNS in ACLs January 2016 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, . Author's Address Eliot Lear Cisco Systems Richtistrasse 7 Wallisellen CH-8304 Switzerland Phone: +41 44 878 9200 Email: lear@cisco.com Lear Expires July 22, 2016 [Page 6]