DNSSEC Strict Mode
draft-schwartz-dnsop-dnssec-strict-mode-00

Document Type Active Internet-Draft (individual)
Author Benjamin Schwartz 
Last updated 2021-02-22
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dnsop                                                        B. Schwartz
Internet-Draft                                                Google LLC
Intended status: Standards Track                        22 February 2021
Expires: 26 August 2021

                           DNSSEC Strict Mode
               draft-schwartz-dnsop-dnssec-strict-mode-00

Abstract

   Currently, the DNSSEC security of a zone is limited by the strength
   of its weakest signature algorithm.  DNSSEC Strict Mode makes zones
   as secure as their strongest algorithm instead.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Discussion of this document takes place on the mailing list
   (dnsop@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/dnsop/.

   Source for this draft and an issue tracker can be found at
   https://github.com/bemasc/dnssec-strict-mode.

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 26 August 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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 Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Conventions and Definitions . . . . . . . . . . . . . . . . .   2
   2.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  DNSSEC validation behavior  . . . . . . . . . . . . . . .   2
     2.2.  Algorithm trust levels  . . . . . . . . . . . . . . . . .   3
   3.  The DNSSEC Strict Mode flag . . . . . . . . . . . . . . . . .   4
   4.  Operational Considerations  . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  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.

2.  Background

2.1.  DNSSEC validation behavior

   According to [RFC6840] Section 5.4, when validators (i.e. resolvers)
   are checking DNSSEC signatures:

      a resolver SHOULD accept any valid RRSIG as sufficient, and only
      determine that an RRset is Bogus if all RRSIGs fail validation.

   [RFC6840] Section 5.11 clarifies further:

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      Validators SHOULD accept any single valid path.  They SHOULD NOT
      insist that all algorithms signaled in the DS RRset work, and they
      MUST NOT insist that all algorithms signaled in the DNSKEY RRset
      work.  A validator MAY have a configuration option to perform a
      signature completeness test to support troubleshooting.

   Thus, validators are required to walk through the set of RRSIGs,
   checking each one that they are able until they find one that matches
   or run out.

   Some implementations do offer an option to enforce signature
   completeness, e.g.  Unbound's "harden-algo-downgrade" option
   [Unbound], but most validating resolvers appear to follow the
   standards guidance on this point.  Validators' tolerance for invalid
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