Registration Data Access Protocol (RDAP) Reverse search capabilities

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Table of Contents

2. RDAP Path Segment Specification

The new search paths are OPTIONAL extensions of those defined in [RFC9082]. A generic reverse search path is described by the syntax:¶

{resource-type}/reverse/{role}?{property}=<search pattern>¶

The path segments are defined as in the following:¶

• resource-type: it MUST be one of resource type path segments defined in Section 3.2 of [RFC9082]: "domains", "nameservers" or "entities";¶

• role: it MUST be one of the roles described in Section 10.2.4 of [RFC9083]. For role independent reverse searches, the value "entity" MUST be used;¶

• property: it identifies the entity property to be used in matching the search pattern. A pre-defined list of properties includes: fn, handle, email, city, country, cc. The mapping between such properties and the RDAP properties is shown in Table 1. Some of the properties are related to jCard elements [RFC7095] but, being jCard the JSON format for vCard [RFC6350], the corresponding definitions are included in vCard specification. Servers MAY implement additional properties to those defined in this document.¶

Partial string matching is allowed as defined in section 4.1 of [RFC9082].¶

      https://example.com/rdap/domains/reverse/technical?handle=CID-40*

      https://example.com/rdap/domains/reverse/registrant?fn=Bobby*

      https://example.com/rdap/domains/reverse/registrant?cc=US

      https://example.com/rdap/entites/reverse/registrar?handle=RegistrarX

The "country" property can be used as an alternative to "cc" when RDAP servers don't include the jCard "cc" parameter [RFC8605] in their response.¶

3. RDAP Conformance

Servers complying with this specification MUST include the value "reverse_search" in the rdapConformance property of the help response [RFC9083]. The information needed to register this value in the "RDAP Extensions" registry is described in Section 6.¶

4. Implementation Considerations

The implementation of the proposed extension is technically feasible. Both handle and fn are used as standard path segments to search for entities [RFC9082]. With regards to the other reverse search properties, namely email, city and country code, the impact of their usage on server processing is evaluated to be the same as other existing query capabilities (e.g. wildcard prefixed search pattern) so the risks to degrade the performance or to generate huge result sets can be mitigated by adopting the same policies (e.g. restricting the search functionality, limiting the rate of search requests according to the user profile, truncating and paging the results, returning partial responses).¶

5. Implementation Status

NOTE: Please remove this section and the reference to RFC 7942 prior to publication as an RFC.¶

This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in [RFC7942]. The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not intended as, and must not be construed to be, a catalog of available implementations or their features. Readers are advised to note that other implementations may exist.¶

According to RFC 7942, "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit".¶

6. IANA Considerations

IANA is requested to register the following value in the RDAP Extensions Registry:¶

• Extension identifier: reverse_search¶
• Registry operator: Any¶
• Published specification: This document.¶
• Contact: IETF <iesg@ietf.org>¶
• Intended usage: This extension describes reverse search query patterns for RDAP.¶

7. Privacy Considerations

The use of the capability described in this document MUST be compliant with the rules about privacy protection each RDAP provider is subject to. Sensitive registration data MUST be protected and accessible for permissible purposes only. This functionality SHOULD be only accessible to authorized users and only for a specified use case.¶

Already the request for this functionality could contain Personal Identifiable Information and SHOULD therefore only be available over HTTPS.¶

Providing reverse search in RDAP carries the following threats as described in [RFC6973]:¶

• Correlation¶
• Disclosure¶
• Misuse of information¶

Therefore, RDAP providers are REQUIRED to mitigate the risk of those threats by implementing appropriate measures supported by security services (see Section 8).¶

8. Security Considerations

Security services required to provide controlled access to the operations specified in this document are described in [RFC7481]. A non exhaustive list of access control paradigms an RDAP provider can implement is presented in Appendix A.¶

The specification of the entity role within the reverse search path allows the RDAP servers to implement different authorization policies on a per-role basis.¶

Appendix A. Paradigms to Enforce Access Control on Reverse Search in RDAP

Access control can be implemented according to different paradigms introducing increasingly stringent rules. The paradigms reported here in the following leverage the capabilities either supported natively or provided as extensions by the OpenID Connect [OIDCC]:¶

• Role-Based Access Control: access rights are granted depending on roles. Generally, this is done by grouping users into fixed categories and assigning each category with static grants. A more dynamic approach can be implemented by using the OpenID Connect "scope" claim;¶

• Purpose-Based Access Control: access rules are based on the notion of purpose which means the intended usage of some data by a user. It can be implemented by tagging a request with the usage purpose and making the RDAP server check the compliance between the given purpose and the control rules applied to data to be returned. The purpose can be stated within an out-of-band process by setting the OpenID Connect RDAP specific "purpose" claim as defined in [draft-ietf-regext-rdap-openid];¶

• Attribute-Based Access Control: rules to manage access rights are evaluated and applied according to specific attributes describing the context within which data are requested. It can be implemented by setting within an out-of-band process additional OpenID Connect claims describing the request context and making the RDAP server check the compliance between the given context and the control rules applied to data to be returned;¶

• Time-Based Access Control: data access is allowed for limited time only. It can be implemented by assigning the users with temporary credentials linked to access grants whose scope is limited.¶

Authors' Addresses