Internet DRAFT - draft-davids-forsalereg
draft-davids-forsalereg
Network Working Group M. Davids
Internet-Draft SIDN Labs
Intended status: Best Current Practice 26 January 2023
Expires: 30 July 2023
Registration of Underscored and Globally Scoped 'for sale' DNS Node Name
draft-davids-forsalereg-02
Abstract
This document defines a simple operational convention of using a
reserved underscored node name ("_for-sale") to indicate that the
parent domain name above, is for sale. It has the advantage that it
can be easily deployed, without affecting any running operations. As
such, the method can be applied to a domain name that is still in
full use.
Status of This Memo
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This Internet-Draft will expire on 30 July 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Content limitations . . . . . . . . . . . . . . . . . . . 3
3.2. RRset limitations . . . . . . . . . . . . . . . . . . . . 4
3.3. RR Type limitation . . . . . . . . . . . . . . . . . . . 4
3.4. TTL limitation . . . . . . . . . . . . . . . . . . . . . 4
3.5. Wildcard limitation . . . . . . . . . . . . . . . . . . . 4
3.6. CNAME limitation . . . . . . . . . . . . . . . . . . . . 4
3.7. Placement of node name . . . . . . . . . . . . . . . . . 4
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Example 1: a URI . . . . . . . . . . . . . . . . . . . . 5
4.2. Example 2: Various other approaches . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. Implementation Status . . . . . . . . . . . . . . . . . . . . 6
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
10. Normative References . . . . . . . . . . . . . . . . . . . . 7
11. Informative References . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Well-established services [RFC3912][RFC9083] exist to find out
whether a domain name is registered or not. However, the fact that a
domain name exists does mean that it cannot be obtained, because it
may be up for sale.
Some registrars and various other parties offer (chargeable)
mediation services between domain name holders and interested
parties, but for domain names that are not for sale, such services
would be a waste of money and time.
This specification defines a simple and universal way to find out if
a domain name, even though it is taken, might be purchased
nevertheless. It enables a domain name holder to add a reserved
underscored node name [RFC8552] in the zone, indicating that the
domain name is actually for sale.
The TXT record RRtype [RFC1035] that is created for that purpose MAY
contain a pointer, such as a URI [RFC8820], to allow an interested
party to find information or to get in touch with the domain owner
and engage in further negotiations.
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With due caution, such information can also be incorporated in the
automated availability services, so that when a domain name is
checked for availability, the service can also indicate whether or
not it is for sale, including a pointer to the selling party's
information.
1.1. Terminology
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. Rationale
There are undoubtedly more ways to address this problem space. The
reasons for the approach defined in this document are primarily
accessibility and simplicity. The indicator can be easily turned on
and off at will and moreover, it is available right away and does not
require major changes in existing services. This allows for a smooth
introduction of the concept.
3. Conventions
3.1. Content limitations
The TXT [RFC8553] (Section 2.1) record MUST contain any valid
content, ranging from an empty string to meaningful text or URIs.
However, it SHALL NOT contain any text that suggests that the domain
is not for sale. If a domain name is not for sale, the "_for-sale"
indicator MUST NOT be used. Any existence of a "_for-sale" TXT
record MUST therefore be regarded as an indication that the domain
name is for sale.
This specification does not dictate the exact use of any content in
the "_for-sale" TXT record, or the lack of any such content. Parties
- such as Registries and Registrars - may use it in their tools,
perhaps even by defining additional requirements that the content
must meet. Alternatively, an individual can use it in combination
with existing tools to make contact with the seller.
The content of the TXT record is "as is" and characters such as ";"
between two URIs for example, have no defined meaning. It is up to
the processor of the content to decide how to handle it.
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3.2. RRset limitations
This specification does not define any restrictions on the number of
TXT records in the RRset, although it is recommended to limit it to
one. It is also recommended that the length of the RDATA [RFC8499]
does not exceed 255 bytes. When the RRset contains multiple records,
or exceeds 255 bytes, it is at the discretion of the processor to
make a selection. For example, a registry might pick a mandatory URI
from the RRset to display on a website as part of its service, while
an individual might just pick a phone number (if present) and dial it
to make contact with a potential seller.
3.3. RR Type limitation
Adding any other RR types under the "_for-sale" leaf but TXT is NOT
RECOMMENDED and they MUST be ignored for the purpose of this
document.
3.4. TTL limitation
A TTL longer than 86400 is NOT RECOMMENDED. Long TTLs increase the
chance of outdated information, which can give potential buyers the
idea that the domain name is still for sale when it is not.
3.5. Wildcard limitation
The "_for-sale" leaf MUST NOT be a wildcard.
3.6. CNAME limitation
The "_for-sale" leaf MAY be a CNAME pointing to a TXT RRtype.
3.7. Placement of node name
The "_for-sale" leaf node name MAY be placed on the top level domain,
or any domain directly below. It MAY also be placed at a lower
level, but only when that level is mentioned in the Public Suffix
List [PSL].
Any other placement of the record MUST NOT be regarded as a signal
that the domain above it is for sale.
See Table 1 for further explanation.
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+===========================+====================+==========+
| Name | Situation | Verdict |
+===========================+====================+==========+
| _for-sale.example | root zone | For sale |
+---------------------------+--------------------+----------+
| _for-sale.aaa.example | Second level | For sale |
+---------------------------+--------------------+----------+
| _for-sale.co.bbb.example | bbb.example in PSL | For sale |
+---------------------------+--------------------+----------+
| _for-sale.www.ccc.example | Other | Invalid |
+---------------------------+--------------------+----------+
Table 1: Allowed placements of TXT record
4. Examples
4.1. Example 1: a URI
The owner of 'example.com' wishes to signal that the domain is for
sale and adds this record to the 'example.com' zone:
_for-sale.example.com. IN TXT "https://example.com/forsale.html"
An interested party notices this signal and can visit the URI
mentioned for further information. The TXT record can also be
processed by automated tools, but see the Security Considerations
section for possible risks.
As an alternative, a mailto: URI could also be used:
_for-sale.example.com. IN TXT "mailto:owner@example.com"
Or a telephone URI:
_for-sale.example.com. IN TXT "tel:+1-201-555-0123"
There can be a use case for a telephone URI, especially since WHOIS
(or RDAP) often has privacy restrictions.
4.2. Example 2: Various other approaches
Free format text:
_for-sale.example.com. IN TXT "I'm for sale: info [at] example.com"
The content in the next example could be malicious, but it is not in
violation of this specification (see Section 7):
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_for-sale.example.com. IN TXT "<script>alert('H4x0r')</script>"
5. IANA Considerations
IANA has established the "Underscored and Globally Scoped DNS Node
Names" registry [RFC8552][IANA]. The underscored node name defined
in this specification should be added as follows:
+-----------+--------------+-------------+
| RR Type | _NODE NAME | Reference |
+-----------+--------------+-------------+
| TXT | _for-sale | TBD |
+-----------+--------------+-------------+
Figure 1: Entry for the "Underscored and Globally Scoped DNS Node
Names" Registry
6. Privacy Considerations
There is a risk of data scraping, such as email addresses and phone
numbers.
7. Security Considerations
One use of the TXT record type defined in this document is to parse
the content it contains and to automatically publish certain
information from it on a website or elsewhere. However, there is a
risk involved in this if the domain owner publishes a malicious URI
or one that points to improper content. This may result in
reputational damage for the party parsing the record.
Even worse is a scenario in which the content of the TXT record is
not validated and sanitized sufficiently, opening doors to - for
example - XSS attacks among other things.
Therefore, it is RECOMMENDED that any parsing and publishing is
conducted with the utmost care.
There is also a risk that this method will be abused as a marketing
tool, or to otherwise lure individuals into visiting certain sites or
attempting other forms of contact, without there being any intention
to actually sell the particular domain name. Therefore, it is
recommended that this method is primarily used by professionals.
8. Implementation Status
The concept described in this document is in use with the .nl ccTLD
registry.
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[note to editor: please remove this section before publication]
9. Acknowledgements
The author would like to thank Thijs van den Hout, Caspar Schutijser,
Melvin Elderman and Paul Bakker for their valuable feedback.
10. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8552] Crocker, D., "Scoped Interpretation of DNS Resource
Records through "Underscored" Naming of Attribute Leaves",
BCP 222, RFC 8552, DOI 10.17487/RFC8552, March 2019,
<https://www.rfc-editor.org/info/rfc8552>.
11. Informative References
[IANA] IANA, "Underscored and Globally Scoped DNS Node Names",
<https://www.iana.org/assignments/dns-parameters/dns-
parameters.xml#underscored-globally-scoped-dns-node-
names>.
[PSL] Mozilla Foundation, "Public Suffix List",
<https://publicsuffix.org/>.
[RFC3912] Daigle, L., "WHOIS Protocol Specification", RFC 3912,
DOI 10.17487/RFC3912, September 2004,
<https://www.rfc-editor.org/info/rfc3912>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>.
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[RFC8553] Crocker, D., "DNS Attrleaf Changes: Fixing Specifications
That Use Underscored Node Names", BCP 222, RFC 8553,
DOI 10.17487/RFC8553, March 2019,
<https://www.rfc-editor.org/info/rfc8553>.
[RFC8820] Nottingham, M., "URI Design and Ownership", BCP 190,
RFC 8820, DOI 10.17487/RFC8820, June 2020,
<https://www.rfc-editor.org/info/rfc8820>.
[RFC9083] Hollenbeck, S. and A. Newton, "JSON Responses for the
Registration Data Access Protocol (RDAP)", STD 95,
RFC 9083, DOI 10.17487/RFC9083, June 2021,
<https://www.rfc-editor.org/info/rfc9083>.
Author's Address
Marco Davids
SIDN Labs
Meander 501
6825 MD Arnhem
Netherlands
Phone: +31 26 352 5500
Email: marco.davids@sidn.nl
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