| Internet-Draft | TTL mapping for EPP | October 2024 |
| Brown | Expires 17 April 2025 | [Page] |
This document describes an extension to the Extensible Provisioning Protocol (EPP) that allows EPP clients to manage the Time-To-Live (TTL) value for domain name delegation records.¶
This note is to be removed before publishing as an RFC.¶
The source for this draft, and an issue tracker, may can be found at https://github.com/gbxyz/epp-ttl-extension.¶
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 17 April 2025.¶
Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved.¶
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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
The principal output of any domain name registry system is a DNS zone file, which contains the delegation record(s) for names registered within a zone (such as a top-level domain).
These records typically include one or more NS records, but may also include DS records for domains secured with DNSSEC ([RFC9364]), and DNAME records for IDN variants ([RFC6927]).
A and/or AAAA records may also be published for nameservers where required by DNS resolvers to avoid an infinite loop.¶
Typically, the Time-To-Live value (TTL, see Section 5 of [RFC9499]) of these records is determined by the registry operator. However, in some circumstances it may be desirable to allow the sponsoring client of a domain name to change the TTL values used for that domain's delegation: for example, to reduce the amount of time required to complete a change of DNS servers, DNSSEC deployment or key rollover, or to allow for fast rollback of such changes.¶
This document describes an EPP extension to the domain name and host object mappings (described in [RFC5731] and [RFC5732], respectively) which allows the sponsor of a domain name or host object to change the TTL values of the resource record(s) associated with that object. It also describes how EPP servers should handle TTLs specified by EPP clients and how both parties co-ordinate to manage TTL values in response to changes in operational or security requirements.¶
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.¶
In examples, "C:" represents lines sent by a protocol client and "S:" represents lines returned by a protocol server. Indentation and white space in examples are provided only to illustrate element relationships and are not required features of this protocol.¶
A protocol client that is authorized to manage an existing object is described as a "sponsoring" client throughout this document.¶
XML is case sensitive. Unless stated otherwise, XML specifications and examples provided in this document MUST be interpreted in the character case presented in order to develop a conforming implementation.¶
EPP uses XML namespaces to provide an extensible object management framework and to identify schemas required for XML instance parsing and validation. These namespaces and schema definitions are used to identify both the base protocol schema and the schemas for managed objects.¶
The XML namespace prefixes used in examples (such as the string ttl in ttl:create) are solely for illustrative purposes.
A conforming implementation MUST NOT require the use of these or any other specific namespace prefixes.¶
In accordance with Section 3.2.2.1 of XML Schema Part 2: Datatypes [XSD-DATATYPES],
the allowable lexical representations for the xs:boolean datatype are the strings "0" and "false" for the concept 'false' and the strings "1" and "true" for the concept 'true'.
Implementations MUST support both styles of lexical representation.¶
This extension adds additional elements to the EPP domain and host mappings.¶
The <ttl:ttl> element is used to define TTL values for the DNS resource records associated with domain and host objects.¶
<ttl:ttl> elements may have the following attributes, depending on whether it appears in a command or response frame:¶
for", which is REQUIRED in both commands and responses,
and which specifies the DNS record type to which the TTL value pertains.
This attribute MUST have one of the following values: "NS", "DS", "DNAME", "A", "AAAA" or "custom";¶
for" attribute is "custom",
then the <ttl:ttl> element MUST also have a "custom" attribute containing a DNS record type conforming with the regular expression in Section 3.1 of [RFC6895].
Additionally, the record type MUST be registered with IANA.¶
min", which MUST NOT be present in command frames but MAY be present in response frames (see Section 2.1.1), and which is used by the server to indicate the lowest value that may be set;¶
default", which MUST NOT be present in command frames but MAY be present in response frames (see Section 2.1.1), and which is used by the server to indicate the default value;¶
max", which MUST NOT be present in command frames but MAY be present in response frames (see Section 2.1.1), and which is used by the server to indicate the highest value that may be set;¶
When present, the value of the "min" attribute MUST be lower than the value of the "max" attribute. The "default" attribute MUST be between the "min" and "max" values, inclusively.¶
The XML schema found in Section 8 of this document restricts the content of <ttl:ttl> elements to be either:¶
To facilitate forward compatibility with future changes to the DNS protocol,
this document does not enumerate or restrict the DNS record types that can be included in the "custom" attribute of the <ttl:ttl> element.¶
The regular expression which is used to validate the values of the "custom" attribute is based on the expression found in Section 3.1 of [RFC6895],
and is intended to match both existing and future RRTYPE mnemonics.
This eliminates the need to update this document in the event that new DNS records that exist above a zone cut (Section 7 of [RFC9499]) are specified.¶
Nevertheless, EPP servers which implement this extension MUST restrict the DNS record types that are accepted in <create> and <update> commands,
and included in <info> responses,
allowing only those types that are actually published in the DNS for domain and host objects.¶
A server that receives a <create> or <update> command that attempts to set TTL values for inapplicable DNS record types MUST respond with a 2306 "Parameter value policy" error.¶
As an illustrative example, a server MAY allow clients to specify TTL values for the following record types for domain objects:¶
NS;¶
DS (if the server also implements [RFC5910]);¶
DNAME (if the server implements IDN variants using DNAME records).¶
Glue records are described in Section 7 of [RFC9499].¶
Servers which implement host objects ([RFC5732]) MAY allow clients to specify TTL values for A and AAAA records for host objects.¶
A server supporting host objects which receives a command that attempts to set TTL values for A and AAAA records on a domain object MUST respond with a 2306 "Parameter value policy" error.¶
EPP servers which use the "host attribute" model
(described in Section 1.1 of [RFC5731])
MAY allow clients to specify TTL values for A and AAAA records for domain objects.¶
The <ttl:info> element is used by clients to request that the server include additional information in <info> responses for domain and host objects.¶
It has a single OPTIONAL policy attribute, which takes a boolean value with a default value of false.¶
The semantics of this element are described in Section 2.1.1.¶
<ttl:info policy="true"/>¶
<ttl:ttl for="NS">3600<ttl:ttl>¶
<ttl:ttl for="NS" min="60" default="86400" max="172800">3600<ttl:ttl>¶
<ttl:ttl for="NS"/>¶
<ttl:ttl for="custom" custom="NEWRRTYPE">3600<ttl:ttl>¶
This extension defines an additional element for EPP <info> commands and responses for domain and host objects.¶
The EPP <info> command is extended to support two different modes:¶
If a server receives an <info> command for a domain or host object which includes a <ttl:info> element
with a "policy" attribute that is "0" or "false",
then the EPP response MUST contain <ttl:ttl> records for all DNS record types that have non-default TTL values.
These elements MUST NOT have the "min", "default" and "max" attributes.¶
Example domain <info> command with a <ttl:info> element with a policy attribute that is false:¶
C:<?xml version="1.0" encoding="UTF-8" standalone="no"?> C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> C: <command> C: <info> C: <domain:info C: xmlns:domain="urn:ietf:params:xml:ns:domain-1.0"> C: <domain:name>example.com</domain:name> C: </domain:info> C: </info> C: <extension> C: <ttl:info C: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0" C: policy="false"/> C: </extension> C: </command> C:</epp>¶
Example domain <info> response to a command with a <ttl:info> element with a policy attribute that is false:¶
S:<?xml version="1.0" encoding="utf-8" standalone="no"?> S:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> S: <response> S: <result code="1000"> S: <msg>Command completed successfully</msg> S: </result> S: <resData> S: <domain:infData S: xmlns:domain="urn:ietf:params:xml:ns:domain-1.0"> S: <domain:name>example.com</domain:name> S: <domain:roid>EXAMPLE1-REP</domain:roid> S: <domain:status s="ok"/> S: <domain:ns> S: <domain:hostObj>ns1.example.com</domain:hostObj> S: <domain:hostObj>ns1.example.net</domain:hostObj> S: </domain:ns> S: <domain:clID>ClientX</domain:clID> S: <domain:crID>ClientX</domain:crID> S: <domain:crDate>2023-11-08T10:14:55.0Z</domain:crDate> S: <domain:exDate>2024-11-08T10:14:55.0Z</domain:exDate> S: </domain:infData> S: </resData> S: <extension> S: <ttl:infData S: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"> S: <ttl:ttl for="NS">172800</ttl:ttl> S: <ttl:ttl for="DS">300</ttl:ttl> S: </ttl:infData> S: <secDNS:infData S: xmlns:secDNS="urn:ietf:params:xml:ns:secDNS-1.1"> S: <secDNS:dsData> S: <secDNS:keyTag>12345</secDNS:keyTag> S: <secDNS:alg>13</secDNS:alg> S: <secDNS:digestType>2</secDNS:digestType> S: <secDNS:digest>49FD46E6C4B45C55D4AC</secDNS:digest> S: </secDNS:dsData> S: </secDNS:infData> S: </extension> S: <trID> S: <clTRID>ABC-12345</clTRID> S: <svTRID>54322-XYZ</svTRID> S: </trID> S: </response> S:</epp>¶
Example host <info> command with a <ttl:info> element with a policy attribute that is false:¶
C:<?xml version="1.0" encoding="UTF-8" standalone="no"?> C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> C: <command> C: <info> C: <host:info C: xmlns:host="urn:ietf:params:xml:ns:host-1.0"> C: <host:name>ns1.example.com</host:name> C: </host:info> C: </info> C: <extension> C: <ttl:info C: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0" C: policy="false"/> C: </extension> C: </command> C:</epp>¶
Example host <info> response to a command with a <ttl:info> element with a policy attribute that is false:¶
S:<?xml version="1.0" encoding="UTF-8" standalone="no"?> S:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> S: <response> S: <result code="1000"> S: <msg>Command completed successfully</msg> S: </result> S: <resData> S: <host:infData S: xmlns:host="urn:ietf:params:xml:ns:host-1.0"> S: <host:name>ns1.example.com</host:name> S: <host:roid>NS1_EXAMPLE1-REP</host:roid> S: <host:status s="ok"/> S: <host:addr ip="v4">192.0.2.2</host:addr> S: <host:addr ip="v6">2001:DB8::8:800:200C:417A</host:addr> S: <host:clID>ClientX</host:clID> S: <host:crID>ClientX</host:crID> S: <host:crDate>2023-11-08T10:14:55.0Z</host:crDate> S: </host:infData> S: </resData> S: <extension> S: <ttl:infData S: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"> S: <ttl:ttl for="A">172800</ttl:ttl> S: <ttl:ttl for="AAAA">86400</ttl:ttl> S: </ttl:infData> S: </extension> S: <trID> S: <clTRID>ABC-12345</clTRID> S: <svTRID>54322-XYZ</svTRID> S: </trID> S: </response> S:</epp>¶
If a server receives an <info> command for a domain or host object which includes a <ttl:info> element
with a "policy" attribute is "1" or "true",
then the EPP response MUST contain <ttl:ttl> records for all supported DNS record types,
irrespective of whether those record types are actually in use by the object in question.
These elements MUST have the "min", "default" and "max" attributes.¶
Example domain <info> command requesting the server policies:¶
C:<?xml version="1.0" encoding="UTF-8" standalone="no"?> C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> C: <command> C: <info> C: <domain:info C: xmlns:domain="urn:ietf:params:xml:ns:domain-1.0"> C: <domain:name>example.com</domain:name> C: </domain:info> C: </info> C: <extension> C: <ttl:info C: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0" C: policy="true"/> C: </extension> C: </command> C:</epp>¶
Example domain <info> response providing the server policies:¶
<?xml version="1.0" encoding="utf-8" standalone="no"?>
<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
<response>
<result code="1000">
<msg>Command completed successfully</msg>
</result>
<resData>
<domain:infData
xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
<domain:name>example.com</domain:name>
<domain:roid>EXAMPLE1-REP</domain:roid>
<domain:status s="ok"/>
<domain:ns>
<domain:hostObj>ns1.example.com</domain:hostObj>
<domain:hostObj>ns1.example.net</domain:hostObj>
</domain:ns>
<domain:clID>ClientX</domain:clID>
<domain:crID>ClientX</domain:crID>
<domain:crDate>2023-11-08T10:14:55.0Z</domain:crDate>
<domain:exDate>2024-11-08T10:14:55.0Z</domain:exDate>
</domain:infData>
</resData>
<extension>
<ttl:infData
xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0">
<ttl:ttl for="NS"
min="3600"
default="86400"
max="172800">172800</ttl:ttl>
<ttl:ttl for="DS"
min="60"
default="86400"
max="172800">300</ttl:ttl>
</ttl:infData>
<secDNS:infData
xmlns:secDNS="urn:ietf:params:xml:ns:secDNS-1.1">
<secDNS:dsData>
<secDNS:keyTag>12345</secDNS:keyTag>
<secDNS:alg>13</secDNS:alg>
<secDNS:digestType>2</secDNS:digestType>
<secDNS:digest>49FD46E6C4B45C55D4AC</secDNS:digest>
</secDNS:dsData>
</secDNS:infData>
</extension>
<trID>
<clTRID>ABC-12345</clTRID>
<svTRID>54322-XYZ</svTRID>
</trID>
</response>
</epp>
¶
Example host <info> command requesting the server policies:¶
C:<?xml version="1.0" encoding="UTF-8" standalone="no"?> C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> C: <command> C: <info> C: <host:info C: xmlns:host="urn:ietf:params:xml:ns:host-1.0"> C: <host:name>ns1.example.com</host:name> C: </host:info> C: </info> C: <extension> C: <ttl:info C: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0" C: policy="true"/> C: </extension> C: </command> C:</epp>¶
Example host <info> response providing the server policies:¶
S:<?xml version="1.0" encoding="UTF-8" standalone="no"?> S:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> S: <response> S: <result code="1000"> S: <msg>Command completed successfully</msg> S: </result> S: <resData> S: <host:infData S: xmlns:host="urn:ietf:params:xml:ns:host-1.0"> S: <host:name>ns1.example.com</host:name> S: <host:roid>NS1_EXAMPLE1-REP</host:roid> S: <host:status s="ok"/> S: <host:addr ip="v4">192.0.2.2</host:addr> S: <host:addr ip="v6">2001:DB8::8:800:200C:417A</host:addr> S: <host:clID>ClientX</host:clID> S: <host:crID>ClientX</host:crID> S: <host:crDate>2023-11-08T10:14:55.0Z</host:crDate> S: </host:infData> S: </resData> S: <extension> S: <ttl:infData S: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"> S: <ttl:ttl for="A" S: min="3600" S: default="86400" S: max="172800">172800</ttl:ttl> S: <ttl:ttl for="AAAA" S: min="3600" S: default="86400" S: max="172800">86400</ttl:ttl> S: </ttl:infData> S: </extension> S: <trID> S: <clTRID>ABC-12345</clTRID> S: <svTRID>54322-XYZ</svTRID> S: </trID> S: </response> S:</epp>¶
This extension defines an additional element for EPP <create> commands for domain and host objects.¶
The <command> element of the <create> command frame MAY contain an <extension> element which MAY contain a <ttl:create> element.
This element MUST contain one or more <ttl:ttl> records as described in Section 1.2.¶
Example domain <create> command:¶
C:<?xml version="1.0" encoding="UTF-8" standalone="no"?> C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> C: <command> C: <create> C: <domain:create C: xmlns:domain="urn:ietf:params:xml:ns:domain-1.0"> C: <domain:name>example.com</domain:name> C: <domain:period unit="y">1</domain:period> C: <domain:ns> C: <domain:hostObj>ns1.example.com</domain:hostObj> C: <domain:hostObj>ns1.example.net</domain:hostObj> C: </domain:ns> C: <domain:authInfo> C: <domain:pw/> C: </domain:authInfo> C: </domain:create> C: </create> C: <extension> C: <ttl:create C: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"> C: <ttl:ttl for="NS">172800</ttl:ttl> C: <ttl:ttl for="DS">300</ttl:ttl> C: </ttl:create> C: <secDNS:create C: xmlns:secDNS="urn:ietf:params:xml:ns:secDNS-1.1"> C: <secDNS:dsData> C: <secDNS:keyTag>12345</secDNS:keyTag> C: <secDNS:alg>13</secDNS:alg> C: <secDNS:digestType>2</secDNS:digestType> C: <secDNS:digest>49FD46E6C4B45C55D4AC</secDNS:digest> C: </secDNS:dsData> C: </secDNS:create> C: </extension> C: <clTRID>ABC-12345</clTRID> C: </command> C:</epp>¶
Example host <create> command:¶
C:<?xml version="1.0" encoding="UTF-8" standalone="no"?> C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> C: <command> C: <create> C: <host:create C: xmlns:host="urn:ietf:params:xml:ns:host-1.0"> C: <host:name>ns1.example.com</host:name> C: <host:addr ip="v4">192.0.2.2</host:addr> C: <host:addr ip="v6">2001:DB8::8:800:200C:417A</host:addr> C: </host:create> C: </create> C: <extension> C: <ttl:create C: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"> C: <ttl:ttl for="A"/> C: <ttl:ttl for="AAAA">86400</ttl:ttl> C: </ttl:create> C: </extension> C: <clTRID>ABC-12345</clTRID> C: </command> C:</epp>¶
If an EPP server receives a <create> command containing a TTL value that is outside the server's permitted range, it MUST reject the command with a 2004 "Parameter value range error" response.¶
This extension defines an additional element for EPP <update> commands for domain and host objects.¶
The <command> element of the <update> command frame MAY contain an <extension> element which MAY contain a <ttl:update> element.
This element MUST contain one or more <ttl:ttl> records as described in Section 1.2.¶
Example domain <update> command:¶
C:<?xml version="1.0" encoding="UTF-8" standalone="no"?> C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> C: <command> C: <update> C: <domain:update C: xmlns:domain="urn:ietf:params:xml:ns:domain-1.0"> C: <domain:name>example.com</domain:name> C: </domain:update> C: </update> C: <extension> C: <ttl:update C: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"> C: <ttl:ttl for="NS"/> C: <ttl:ttl for="custom" C: custom="DELEG"/> C: <ttl:ttl for="DS">86400</ttl:ttl> C: </ttl:update> C: </extension> C: <clTRID>ABC-12345</clTRID> C: </command> C:</epp>¶
Example host <update> command:¶
C:<?xml version="1.0" encoding="UTF-8" standalone="no"?> C:<epp xmlns="urn:ietf:params:xml:ns:epp-1.0"> C: <command> C: <update> C: <host:update C: xmlns:host="urn:ietf:params:xml:ns:host-1.0"> C: <host:name>ns1.example.com</host:name> C: </host:update> C: </update> C: <extension> C: <ttl:update C: xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"> C: <ttl:ttl for="A">86400</ttl:ttl> C: <ttl:ttl for="AAAA">3600</ttl:ttl> C: </ttl:update> C: </extension> C: <clTRID>ABC-12345</clTRID> C: </command> C:</epp>¶
If an EPP server receives an <update> command containing a TTL value that is outside the server's permitted range, it MUST reject the command with a 2004 "Parameter value range error" response.¶
Servers SHOULD restrict the supported DNS record types in accordance with their own policy.
For example, a server MAY allow clients to specify TTL values for DS records only.¶
A server which receives a <create> or <update> command which includes a restricted record type MUST respond with a 2306 "Parameter value policy" error.¶
Clients can discover the DNS record types for which an EPP server permits TTL values to be changed by performing a "Policy Mode" <info> command,
as outlined in Section 2.1.1.2.¶
EPP servers which implement this extension SHOULD use the values provided by EPP clients for the TTL values of records published in the DNS for domain and (if supported) host objects.¶
EPP servers that use the "host attribute" model SHOULD use any NS, A and/or AAAA TTL values specified for the domain object when publishing NS, A and/or AAAA records derived from host attributes.¶
EPP server operators MAY, in order to address operational or security issues, make changes to TTL values out-of-band (that is, not in response to an <update> command received from the sponsoring client).¶
Server operators MAY also implement automatic reset of TTL values, so that they revert to the default value a certain amount of time after an update has been made.¶
If a TTL value is changed out-of-band, EPP server operators MAY notify the sponsoring client using the EPP Change Poll extension ([RFC8590]), which provides a generalised method for EPP servers to notify clients of changes to objects under their sponsorship.¶
Registry operators must consider the balance between registrants' desire for changes to domains to be visible in the DNS quickly, and the increased DNS query traffic that short TTLs can bring.¶
Registry operators SHOULD implement limits on the maximum and minimum accepted TTL values that are narrower than the values permitted in the XML schema in the Formal syntax (which were chosen to allow any TTL permitted in DNS records), in order to prevent scenarios where an excessively high or low TTL causes operational issues on either side of the zone cut.¶
Section 4 describes how server operators MAY unilaterally change TTL values in order to address operational or security issues, or only permit changes for limited time periods (after which TTLs revert to the default).¶
A common operational mistake is changing of DNS record TTLs during or after the planned change to the records themselves. This arises due to a misunderstanding about how TTLs work.¶
It is RECOMMENDED that guidance be provided to users so they are aware that changes to a TTL are only effective in shortening transition periods if implemented a period of time — at least equal to the current TTL — before the planned change.
The latency between receipt of the <update> command and the actual publication of the changes in the DNS should also be taken into consideration in this calculation.¶
Registry operators may change their policies relating to TTL values from time to time. Previously configured TTL values may consequently fall outside a newly-applied policy. This document places no obligation on EPP server operators in respect of these values, and server operators may, as part of a policy change, change the TTL values specified by clients for domain and host objects. Section 4 describes how such out-of-band changes should be carried out.¶
Some malicious actors use a technique called "fast flux DNS" ([SAC-025]) to rapidly change the DNS configuration for a zone in order to evade takedown and law enforcement activity. Server operators should take this into consideration when setting the lower limit on TTL values, since a short TTL on delegations may enhance the effectiveness of fast flux techniques on evasion.¶
Client implementations which provide an interface for customers to configure TTL values for domain names should consider implementing controls to deter and mitigate abusive behaviour, such as those outlined in the "Current and Possible Mitigation Alternatives" section of [SAC-025].¶
An attacker who obtains access to a customer account at a domain registrar which supports this extension could make unauthorised changes to the NS and/or glue records for a domain,
and then increase the associated TTLs so that the changes persist in caches for a long time after the attack has been detected.¶
Client implementations which provide an interface for customers to configure TTL values for domain names should consider implementing upper limits in order to reduce the impact of account compromise, in addition to best practices relating to credential management, multi-factor authentication, risk-based access control, and so on.¶
This document uses URNs to describe XML namespaces and XML schemas conforming to a registry mechanism described in [RFC3688]. The following URI assignment is requested of IANA:¶
Registration for the TTL namespace:¶
URI:
urn:ietf:params:xml:ns:epp:ttl-1.0¶
Registrant Contact: IESG¶
XML: None. Namespace URIs do not represent an XML specification¶
Registration for the TTL XML schema:¶
URI:
urn:ietf:params:xml:schema:epp:ttl-1.0¶
Registrant Contact: IESG¶
XML: See the "Formal syntax" section of this document¶
The EPP extension described in this document is to be registered by IANA in the Extensions for the "Extensible Provisioning Protocol (EPP)" registry described in [RFC7451]. The details of the registration are as follows:¶
The formal syntax presented here is a complete schema representation of the extension suitable for automated validation of EPP XML instances.¶
<?xml version="1.0" encoding="UTF-8"?>
<schema
xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="urn:ietf:params:xml:ns:epp:ttl-1.0"
xmlns:ttl="urn:ietf:params:xml:ns:epp:ttl-1.0"
elementFormDefault="qualified">
<annotation>
<documentation>
Extensible Provisioning Protocol v1.0 extension
schema for Time-To-Live (TTL) values for domain
and host objects.
</documentation>
</annotation>
<element name="info">
<complexType>
<attribute name="policy" type="boolean" default="false"/>
</complexType>
</element>
<!--
<ttl> elements can appear in <create> and
<update> commands, and <info> responses
-->
<element name="create" type="ttl:commandContainer">
<unique name="uniqueRRTypeForCreate">
<selector xpath="ttl:ttl"/>
<field xpath="@for"/>
</unique>
</element>
<element name="update" type="ttl:commandContainer">
<unique name="uniqueRRTypeForUpdate">
<selector xpath="ttl:ttl"/>
<field xpath="@for"/>
</unique>
</element>
<element name="infData" type="ttl:responseContainer">
<unique name="uniqueRRTypeForInfo">
<selector xpath="ttl:ttl"/>
<field xpath="@for"/>
</unique>
</element>
<complexType name="commandContainer">
<sequence>
<element
name="ttl"
type="ttl:commandTTLType"
minOccurs="1"
maxOccurs="unbounded"/>
</sequence>
</complexType>
<complexType name="responseContainer">
<sequence>
<element
name="ttl"
type="ttl:responseTTLType"
minOccurs="1"
maxOccurs="unbounded"/>
</sequence>
</complexType>
<complexType name="commandTTLType">
<simpleContent>
<extension base="ttl:ttlOrNull">
<attribute
name="for"
type="ttl:rrType"
use="required"/>
<attribute
name="custom"
type="ttl:customRRType"/>
</extension>
</simpleContent>
</complexType>
<complexType name="responseTTLType">
<simpleContent>
<extension base="ttl:ttlOrNull">
<attribute
name="for"
type="ttl:rrType"
use="required"/>
<attribute
name="custom"
type="ttl:customRRType"/>
<attribute
name="min"
type="ttl:ttlValue"/>
<attribute
name="default"
type="ttl:ttlValue"/>
<attribute
name="max"
type="ttl:ttlValue"/>
</extension>
</simpleContent>
</complexType>
<!--
union type allowing the element to either contain
nothing or a TTL value
-->
<simpleType name="ttlOrNull">
<union
memberTypes="ttl:emptyValue ttl:ttlValue"/>
</simpleType>
<!-- empty value type -->
<simpleType name="emptyValue">
<restriction base="token">
<length value="0"/>
</restriction>
</simpleType>
<!-- TTL value type -->
<simpleType name="ttlValue">
<restriction base="nonNegativeInteger">
<minInclusive value="0"/>
<maxInclusive value="2147483647"/>
</restriction>
</simpleType>
<!-- resource record mnemonic type -->
<simpleType name="rrType">
<restriction base="token">
<enumeration value="NS" />
<enumeration value="DS" />
<enumeration value="DNAME" />
<enumeration value="A" />
<enumeration value="AAAA" />
<enumeration value="custom" />
</restriction>
</simpleType>
<!-- custom resource record type -->
<simpleType name="customRRType">
<restriction base="token">
<pattern value="A|[A-Z][A-Z0-9\-]*[A-Z0-9]"/>
</restriction>
</simpleType>
</schema>
¶
This section is to be removed before publishing as an RFC.¶
Organization: Verisign Inc.¶
Name: Verisign EPP SDK¶
Description: The Verisign EPP SDK includes both a full client implementation and a full server stub implementation of this specification.¶
Level of maturity: Development¶
Coverage: All aspects of the protocol are implemented.¶
Licensing: GNU Lesser General Public License¶
Contact: jgould@verisign.com¶
URL: https://www.verisign.com/en_US/channel-resources/domain-registry-products/epp-sdks¶
Name: Pepper EPP Client¶
Description: The Pepper EPP client fully implements this specification.
The underlying Net::EPP:: Perl module also implements this specification.¶
Level of maturity: Development¶
Coverage: All aspects of the protocol will be implemented.¶
Licensing: Perl Artistic License¶
Contact: The author of this document.¶
URL: https://github.com/gbxyz/pepper¶
This section is to be removed before publishing as an RFC.¶
Changes resulting from the Dnsdir review:¶
<info> command (Section 2.1.1.2) to discover the DNS record types supported by the server.¶
<info> commands work so that a <ttl:info> element is required in order for <ttl:ttl> elements to be included in the response.
Thanks to JG for this feedback.¶
ttl:ttl now has a for attribute which can be any DNS record type.
Section 1.2.1.2 describes how the set of supported record types may be limited.¶
urn:ietf:params:xml:ns:ttl-1.0 to urn:ietf:params:xml:ns:epp:ttl-1.0.¶
The author wishes to thank the following people for their advice and feedback during the development of this document:¶