Survey of Domain Verification Techniques using DNS

Document Type Active Internet-Draft (individual)
Authors Shivan Sahib  , Shumon Huque 
Last updated 2021-03-10
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Network Working Group                                           S. Sahib
Internet-Draft                                                  S. Huque
Intended status: Informational                                Salesforce
Expires: 11 September 2021                                 10 March 2021

           Survey of Domain Verification Techniques using DNS


   Verification of ownership of domains in the Domain Name System (DNS)
   [RFC1034] [RFC1035] often relies on adding or editing DNS records
   within the domain.  This document lays out the various techniques and
   the pros and cons of each.

Discussion Venues

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

   Source for this draft and an issue tracker can be found at

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Table of Contents

   1.  Introduction
   2.  Conventions and Definitions
   3.  Verification Techniques
     3.1.  TXT based
       3.1.1.  Examples
     3.2.  CNAME based
       3.2.1.  Examples
   4.  Recommendations
     4.1.  TXT vs CNAME
     4.2.  TXT recommendations
     4.3.  CNAME recommendations
   5.  Security Considerations
   6.  IANA Considerations
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Authors' Addresses

1.  Introduction

   Many providers on the internet need users to prove that they control
   a particular domain before granting them some sort of privilege
   associated with that domain.  For instance, certificate authorities
   like Let's Encrypt [LETSENCRYPT] ask requesters of TLS certificates
   to prove that they operate the domain they're requesting the
   certificate for.  Providers generally allow for several different
   ways of proving domain control, some of which include manipulating
   DNS records.  This document focuses on DNS techniques for domain
   verification; other techniques (such as email or HTML verification)
   are out-of-scope.

   In practice, DNS-based verification often looks like the provider
   generating a random value and asking the requester to create a DNS
   record containing this random value and placing it at a location that
   the provider can query for.  Generally only one temporary DNS record
   is sufficient for proving domain ownership.

2.  Conventions and Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "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.

3.  Verification Techniques

3.1.  TXT based

   Although the original DNS protocol specifications did not associate
   any semantics with the DNS TXT record, [RFC1464] describes how to use
   them to store attributes in the form of ASCII text key-value pairs
   for a particular domain.   IN   TXT   "printer=lpr5"

   In practice, there is wide variation in the content of DNS TXT
   records used for domain verification, and they often do not follow
   the key-value pair model.

   The same domain name can have multiple distinct TXT records (a TXT
   Record Set).

   TXT record-based DNS domain verification is usually the default
   option for DNS verification.  The service provider asks the user to
   add a DNS TXT record (perhaps through their domain host or DNS
   provider) at the domain with a certain value.  Then, the service
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