RFC 9038: Extensible Provisioning Protocol (EPP) Unhandled Namespaces | RFC Editor

Abstract

The Extensible Provisioning Protocol (EPP), as defined in RFC 5730, includes a method for the client and server to determine the objects to be managed during a session and the object extensions to be used during a session. The services are identified using namespace URIs, and an "unhandled namespace" is one that is associated with a service not supported by the client. This document defines an operational practice that enables the server to return information associated with unhandled namespace URIs and that maintains compliance with the negotiated services defined in RFC 5730.¶

Status of This Memo

This is an Internet Standards Track document.¶

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.¶

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc9038.¶

Copyright Notice

Copyright (c) 2021 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 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.¶

1. Introduction

The Extensible Provisioning Protocol (EPP), as defined in [RFC5730], includes a method for the client and server to determine the objects to be managed during a session and the object extensions to be used during a session. The services are identified using namespace URIs. How should the server handle service data that needs to be returned in the response when the client does not support the required service namespace URI, which is referred to as an "unhandled namespace"? An unhandled namespace is a significant issue for the processing of the poll messages described in [RFC5730], since poll messages are inserted by the server prior to knowing the supported client services, and the client needs to be capable of processing all poll messages. Returning an unhandled namespace poll message is not compliant with the negotiated services defined in [RFC5730], and returning an error makes the unhandled namespace poll message a poison message by halting the processing of the poll queue. An unhandled namespace is also an issue for general EPP responses when the server has information that it cannot return to the client due to the client's supported services. The server should be able to return unhandled namespace information that the client can process later. This document defines an operational practice that enables the server to return information associated with unhandled namespace URIs and that maintains compliance with the negotiated services defined in [RFC5730].¶

2. Unhandled Namespaces

An unhandled namespace is an XML namespace that is associated with a response extension that is not included in the client-specified EPP login services of [RFC5730]. The EPP login services consist of the set of XML namespace URIs included in the <objURI> or <extURI> elements of the EPP <login> command [RFC5730]. The services supported by the server are included in the <objURI> and <extURI> elements of the EPP <greeting> [RFC5730], which should be a superset of the login services included in the EPP <login> command. A server may have information associated with a specific namespace that it needs to return in the response to a client. The unhandled namespaces problem exists when the server has information that it needs to return to the client, but the namespace of the information is not supported by the client based on the negotiated EPP <login> command services.¶

3. Use of EPP <extValue> for Unhandled Namespace Data

In [RFC5730], the <extValue> element is used to provide additional error diagnostic information, including the <value> element that identifies the client-provided element that caused a server error condition and the <reason> element containing the human-readable message that describes the reason for the error. This operational practice extends the use of the <extValue> element for the purpose of returning unhandled namespace information in a successful response.¶

When a server has data to return to the client that the client does not support based on the login services, the server MAY return a successful response with the data for each unsupported namespace moved into an <extValue> element [RFC5730]. The unhandled namespace will not cause an error response, but the unhandled namespace data will instead be moved to an <extValue> element, along with a reason why the unhandled namespace data could not be included in the appropriate location of the response. The <extValue> element will not be processed by the XML processor. The <extValue> element contains the following child elements:¶

<value>:

Contains a child element with the unhandled namespace XML. The unhandled namespace MUST be declared in the child element or any containing element, including the root element. XML processing of the <value> element is disabled by the XML schema in [RFC5730], so the information can safely be returned in the <value> element.¶

<reason>:

A formatted, human-readable message that indicates the reason the unhandled namespace data was not returned in the appropriate location of the response. The formatted reason SHOULD follow the Augmented Backus-Naur Form (ABNF) grammar [RFC5234] format: NAMESPACE-URI " not in login services", where NAMESPACE-URI is the unhandled XML namespace like "urn:ietf:params:xml:ns:domain-1.0" in [RFC5731].¶

This document applies to the handling of unsupported namespaces for object-level extensions and command-response extensions [RFC3735]. This document does not apply to the handling of unsupported namespaces for protocol-level extensions or authentication-information extensions [RFC3735]. Refer to the following sections on how to handle an unsupported object-level extension namespace or an unsupported command-response extension namespace.¶

4. Signaling Client and Server Support

This document does not define new EPP protocol elements but rather specifies an operational practice using the existing EPP protocol, where the client and the server can signal support for the operational practice using a namespace URI in the login and greeting extension services. The namespace URI "urn:ietf:params:xml:ns:epp:unhandled-namespaces-1.0" is used to signal support for the operational practice. The client includes the namespace URI in an <svcExtension> <extURI> element of the <login> command [RFC5730]. The server includes the namespace URI in an <svcExtension> <extURI> element of the greeting [RFC5730].¶

A client that receives the namespace URI in the server's greeting extension services can expect the following supported behavior by the server:¶

A server that receives the namespace URI in the client's <login> command extension services can expect the following supported behavior by the client:¶

5. Usage with General EPP Responses

The unhandled namespace approach defined in Section 3 MAY be used for a general EPP response to an EPP command. A general EPP response includes any EPP response that is not a poll message. The use of the unhandled namespace approach for poll-message EPP responses is defined in Section 6. The server MAY exclude the unhandled namespace information in the general EPP response or MAY include it using the unhandled namespace approach.¶

The unhandled namespace approach for general EPP responses SHOULD only be applicable to command-response extensions, defined in Section 3.2, since the server SHOULD NOT accept an object-level EPP command if the client did not include the object-level namespace URI in the login services. An object-level EPP response extension is returned when the server successfully executes an object-level EPP command extension. The server MAY return an unhandled object-level extension to the client, as defined in Section 3.1.¶

Returning domain name Redemption Grace Period (RGP) data, based on [RFC3915], provides an example of applying the unhandled namespace approach for a general EPP response. If the client does not include the "urn:ietf:params:xml:ns:rgp-1.0" namespace URI in the login services and the domain <info> response of a domain name does have RGP information, the server MAY exclude the <rgp:infData> element from the EPP response or MAY include it under the <extValue> element, per Section 3.2.¶

Below is an example of a domain name <info> response [RFC5731] converted to an unhandled <rgp:infData> element (see Section 4.1.1 of [RFC3915]) included under an <extValue> element:¶

6. Usage with Poll-Message EPP Responses

The unhandled namespace approach, defined in Section 3, MUST be used if there is unhandled namespace information included in a <poll> response. The server inserts poll messages into the client's poll queue independent of knowing the supported client login services; therefore, there may be unhandled object-level extensions and command-response extensions included in a client's poll queue. In [RFC5730], the <poll> command is used by the client to retrieve and acknowledge poll messages that have been inserted by the server. The <poll> response is an EPP response that includes the <msgQ> element that provides poll queue metadata about the message. The unhandled namespace approach, defined in Section 3, is used for an unhandled object-level extension and for each of the unhandled command-response extensions attached to the <poll> response. The resulting <poll> response MAY have either or both the object-level extension or command-response extensions moved to <extValue> elements, as defined in Section 3.¶

The change poll message, as defined in Section 3.1.2 of [RFC8590], which is an extension of any EPP object, is an example of applying the unhandled namespace approach for <poll> responses. Below are examples of converting the domain name <info> response example in Section 3.1.2 of [RFC8590] to an unhandled namespace response. The object that will be used in the examples is a domain name object [RFC5731].¶

Below is a domain name <info> <poll> response [RFC5731] with the unhandled <changePoll:changeData> element [RFC8590] included under an <extValue> element.¶

Below is an unhandled domain name <info> <poll> response [RFC5731] and the unhandled <changePoll:changeData> element [RFC8590] included under an <extValue> element.¶

7. Implementation Considerations

There are implementation considerations for the client and the server to help address the risk of the client ignoring unhandled namespace information included in an EPP response that is needed to meet technical, policy, or legal requirements.¶

8. IANA Considerations

9. Security Considerations

This document does not provide any security services beyond those described by EPP [RFC5730] and protocol layers used by EPP. The security considerations described in these other specifications apply to this specification as well. Since the unhandled namespace content is XML that is not processed in the first pass by the XML parser, the client SHOULD validate the XML when the content is processed to protect against the inclusion of malicious content.¶

10. References

Acknowledgements

The authors wish to thank the following people for their feedback and suggestions: Thomas Corte, Scott Hollenbeck, Patrick Mevzek, and Marcel Parodi.¶

Authors' Addresses