Security Services for the Registration Data Access Protocol (RDAP)
RFC 7481

Internet Engineering Task Force (IETF)                     S. Hollenbeck
Request for Comments: 7481                                 Verisign Labs
Category: Standards Track                                        N. Kong
ISSN: 2070-1721                                                    CNNIC
                                                              March 2015

   Security Services for the Registration Data Access Protocol (RDAP)

Abstract

   The Registration Data Access Protocol (RDAP) provides "RESTful" web
   services to retrieve registration metadata from Domain Name and
   Regional Internet Registries.  This document describes information
   security services, including access control, authentication,
   authorization, availability, data confidentiality, and data integrity
   for RDAP.

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 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7481.

Copyright Notice

   Copyright (c) 2015 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
   (http://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.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   2
     2.1.  Acronyms and Abbreviations  . . . . . . . . . . . . . . .   3
   3.  Information Security Services and RDAP  . . . . . . . . . . .   3
     3.1.  Access Control  . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Authentication  . . . . . . . . . . . . . . . . . . . . .   3
       3.2.1.  Federated Authentication  . . . . . . . . . . . . . .   4
     3.3.  Authorization . . . . . . . . . . . . . . . . . . . . . .   6
     3.4.  Availability  . . . . . . . . . . . . . . . . . . . . . .   6
     3.5.  Data Confidentiality  . . . . . . . . . . . . . . . . . .   7
     3.6.  Data Integrity  . . . . . . . . . . . . . . . . . . . . .   7
   4.  Privacy Threats Associated with Registration Data . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   The Registration Data Access Protocol (RDAP) is specified in multiple
   documents, including "Registration Data Access Protocol (RDAP) Query
   Format" [RFC7482], "JSON Responses for the Registration Data Access
   Protocol (RDAP)" [RFC7483], and "HTTP Usage in the Registration Data
   Access Protocol (RDAP)" [RFC7480].

   One goal of RDAP is to provide security services that do not exist in
   the WHOIS [RFC3912] protocol, including access control,
   authentication, authorization, availability, data confidentiality,
   and data integrity.  This document describes how each of these
   services is achieved by RDAP using features that are available in
   other protocol layers.  Additional or alternative mechanisms can be
   added in the future.  Where applicable, informative references to
   requirements for a WHOIS replacement service [RFC3707] are noted.

2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

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2.1.  Acronyms and Abbreviations

      DNR: Domain Name Registry

      HTTP: Hypertext Transfer Protocol

      JSON: JavaScript Object Notation

      RDAP: Registration Data Access Protocol

      RIR: Regional Internet Registry

      TLS: Transport Layer Security

3.  Information Security Services and RDAP

   RDAP itself does not include native security services.  Instead, RDAP
   relies on features that are available in other protocol layers to
   provide needed security services, including access control,
   authentication, authorization, availability, data confidentiality,
   and data integrity.  A description of each of these security services
   can be found in "Internet Security Glossary, Version 2" [RFC4949].
   No requirements have been identified for other security services.

3.1.  Access Control

   WHOIS does not include specific features to control access to
   registration information.  As described in the following sections,
   RDAP includes features to identify, authenticate, and authorize
   clients, allowing server operators to control access to information
   based on a client's identity and associated authorizations.
   Information returned to a client can be clearly marked with a status
   value (see Section 10.2.2 of [RFC7483]) that identifies the access
   granted to the client.

3.2.  Authentication

   This section describes security authentication mechanisms and the
   need for authorization policies to include them.  It describes
   requirements for the implementations of clients and servers but does
   not dictate the policies of server operators.  For example, a server
   operator with no policy regarding differentiated or tiered access to
   data will have no authorization mechanisms and will have no need for
   any type of authentication.  A server operator with policies on
   differentiated access will have to construct an authorization scheme
   and will need to follow the specified authentication requirements.

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   WHOIS does not provide features to identify and authenticate clients.
   As noted in Section 3.1.4.2 of "Cross Registry Internet Service
   Protocol (CRISP) Requirements" [RFC3707], there is utility in
   allowing server operators to offer "varying degrees of access
   depending on policy and need."  Clients have to be identified and
   authenticated to provide that utility.

   RDAP's authentication framework needs to accommodate anonymous access
   as well as verification of identities using a range of authentication
   methods and credential services.  To that end, RDAP clients and
   servers MUST implement the authentication framework specified in
   "Hypertext Transfer Protocol (HTTP/1.1): Authentication" [RFC7235].
   The "basic" scheme can be used to send a client's user name and
   password to a server in plaintext, base64-encoded form.  The "digest"
   scheme can be used to authenticate a client without exposing the
   client's plaintext password.  If the "basic" scheme is used, HTTP
   over TLS [RFC2818] MUST be used to protect the client's credentials
   from disclosure while in transit (see Section 3.5).

   Servers MUST support either Basic or Digest authentication; they are
   not required to support both.  Clients MUST support both to
   interoperate with servers that support one or the other.  Servers may
   provide a login page that triggers HTTP authentication.  Clients
   should continue sending the HTTP authentication header once they
   receive an initial 401 (Unauthorized) response from the HTTP server
   as long as the scheme portion of the URL doesn't change.

   The Transport Layer Security protocol [RFC5246] includes an optional
   feature to identify and authenticate clients who possess and present
   a valid X.509 digital certificate [RFC5280].  Support for this
   feature is OPTIONAL.

   RDAP does not impose any unique server authentication requirements.
   The server authentication provided by TLS fully addresses the needs
   of RDAP.  In general, transports for RDAP must either provide a
   TLS-protected transport (e.g., HTTPS) or a mechanism that provides an
   equivalent level of server authentication.

   Work on HTTP authentication methods continues.  RDAP is designed to
   be agile enough to support additional methods as they are defined.

3.2.1.  Federated Authentication

   The traditional client-server authentication model requires clients
   to maintain distinct credentials for every RDAP server.  This
   situation can become unwieldy as the number of RDAP servers
   increases.  Federated authentication mechanisms allow clients to use
   one credential to access multiple RDAP servers and reduce client

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   credential management complexity.  RDAP MAY include a federated
   authentication mechanism that permits a client to access multiple
   RDAP servers in the same federation with one credential.

   Federated authentication mechanisms used by RDAP MUST be fully
   supported by HTTP.  OAuth, OpenID, Security Assertion Markup Language
   (SAML), and mechanisms based on Certification Authority (CA) are all
   possible approaches to provide federated authentication.  At the time
   of this document's publication, negotiation or advertisement of
   federated authentication services is still an undefined mechanism by
   the noted federated authentication protocols.  Developing this
   mechanism is beyond the scope of this document.

   The OAuth authorization framework [RFC6749] describes a method for
   users to access protected web resources without having to hand out
   their credentials.  Instead, clients are issued access tokens by
   authorization servers with the permission of the resource owners.
   Using OAuth, multiple RDAP servers can form a federation, and the
   clients can access any server in the same federation by providing one
   credential registered in any server in that federation.  The OAuth
   authorization framework is designed for use with HTTP and thus can be
   used with RDAP.

   OpenID [OpenID] is a decentralized single sign-on authentication
   system that allows users to log in at multiple web sites with one ID
   instead of having to create multiple unique accounts.  An end user
   can freely choose which OpenID provider to use and can preserve their
   Identifier if they switch OpenID providers.

   Note that OAuth and OpenID do not consistently require data
   confidentiality services to protect interactions between providers
   and consumers.  HTTP over TLS [RFC2818] can be used as needed to
   provide protection against man-in-the-middle attacks.

   SAML 2.0 [SAML] is an XML-based protocol that can be used to
   implement web-based authentication and authorization services,
   including single sign on.  It uses security tokens containing
   assertions to exchange information about an end user between an
   identity provider and a service provider.

   The Transport Layer Security protocol describes the specification of
   a client certificate in Section 7.4.6 of [RFC5246].  Clients who
   possess and present a valid X.509 digital certificate, issued by a
   CA, could be identified and authenticated by a server who trusts the
   corresponding CA.  A certificate authentication method can be used to
   achieve federated authentication in which multiple RDAP servers all
   trust the same CAs, and then any client with a certificate issued by
   a trusted CA can access any RDAP server in the federation.  This

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   certificate-based mechanism is supported by HTTPS and can be used
   with RDAP.

3.3.  Authorization

   WHOIS does not provide services to grant different levels of access
   to clients based on a client's authenticated identity.  As noted in
   Section 3.1.4.2 of "Cross Registry Internet Service Protocol (CRISP)
   Requirements" [RFC3707], there is utility in allowing server
   operators to offer "varying degrees of access depending on policy and
   need."  Access control decisions can be made once a client's identity
   has been established and authenticated (see Section 3.2).

   Server operators MAY offer varying degrees of access depending on
   policy and need in conjunction with the authentication methods
   described in Section 3.2.  If such varying degrees of access are
   supported, an RDAP server MUST provide granular access controls (that
   is, per registration data object) in order to implement authorization
   policies.  Some examples:

   -  Clients will be allowed access only to data for which they have a
      relationship.

   -  Unauthenticated or anonymous access status may not yield any
      contact information.

   -  Full access may be granted to a special group of authenticated
      clients.

   The type of access allowed by a server will most likely vary from one
   operator to the next.  A description of the response privacy
   considerations associated with different levels of authorization can
   be found in Section 13 of [RFC7483].

3.4.  Availability

   An RDAP service has to be available to be useful.  There are no RDAP-
   unique requirements to provide availability, but as a general
   security consideration, a service operator needs to be aware of the
   issues associated with denial of service.  A thorough reading of
   "Internet Denial-of-Service Considerations" [RFC4732] is advised.

   An RDAP service MAY use an HTTP throttling mechanism to limit the
   number of queries that a single client can send in a given period of
   time.  If used, the server SHOULD return an HTTP 429 (Too Many
   Requests) response code as described in "Additional HTTP Status
   Codes" [RFC6585].  A client that receives a 429 response SHOULD
   decrease its query rate and honor the Retry-After header field if one

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   is present.  Note that this is not a defense against
   denial-of-service attacks, since a malicious client could ignore the
   code and continue to send queries at a high rate.  A server might use
   another response code if it did not wish to reveal to a client that
   rate limiting is the reason for the denial of a reply.

3.5.  Data Confidentiality

   WHOIS does not provide the ability to protect data from inadvertent
   disclosure while in transit.  RDAP uses HTTP over TLS [RFC2818] to
   provide that protection by encrypting all traffic sent on the
   connection between client and server.  HTTP over TLS MUST be used to
   protect all client-server exchanges unless operational constraints
   make it impossible to meet this requirement.  It is also possible to
   encrypt discrete objects (such as command path segments and JSON-
   encoded response objects) at one endpoint, send them to the other
   endpoint via an unprotected transport protocol, and decrypt the
   object on receipt.  Encryption algorithms as described in "Internet
   Security Glossary, Version 2" [RFC4949] are commonly used to provide
   data confidentiality at the object level.

   There are no current requirements for object-level data
   confidentiality using encryption.  Support for this feature could be
   added to RDAP in the future.

   As noted in Section 3.2, the HTTP "basic" authentication scheme can
   be used to authenticate a client.  When this scheme is used, HTTP
   over TLS MUST be used to protect the client's credentials from
   disclosure while in transit.  If the policy of the server operator
   requires encryption to protect client-server data exchanges (such as
   to protect non-public data that cannot be accessed without client
   identification and authentication), HTTP over TLS MUST be used to
   protect those exchanges.

   A description of privacy threats that can be addressed with
   confidentiality services can be found in Section 4.  Section 10.2.2
   of [RFC7483] describes status values that can be used to describe
   operator actions used to protect response data from disclosure to
   unauthorized clients.

3.6.  Data Integrity

   WHOIS does not provide the ability to protect data from modification
   while in transit.  Web services such as RDAP commonly use HTTP over
   TLS [RFC2818] to provide that protection by using a keyed Message
   Authentication Code (MAC) to detect modifications.  It is also
   possible to sign discrete objects (such as command path segments and
   JSON-encoded response objects) at one endpoint, send them to the

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   other endpoint via a transport protocol, and validate the signature
   of the object on receipt.  Digital signature algorithms as described
   in "Internet Security Glossary, Version 2" [RFC4949] are commonly
   used to provide data integrity at the object level.

   There are no current requirements for object-level data integrity
   using digital signatures.  Support for this feature could be added to
   RDAP in the future.

   The most specific need for this service is to provide assurance that
   HTTP 30x redirection hints [RFC7231] and response elements returned
   from the server are not modified while in transit.  If the policy of
   the server operator requires message integrity for client-server data
   exchanges, HTTP over TLS MUST be used to protect those exchanges.

4.  Privacy Threats Associated with Registration Data

   Registration data has historically included personal data about
   registrants.  WHOIS services have historically made this information
   available to the public, creating a privacy risk by revealing the
   personal details of registrants.  WHOIS services have not had the
   benefit of authentication or access control mechanisms to gate access
   to registration data.  As a result of this, proxy and privacy
   services have arisen to shield the identities of registrants.

   The standardization of RDAP does not change or impact the data that
   operators may require to be collected from registrants, but it
   provides support for a number of mechanisms that may be used to
   mitigate privacy threats to registrants should operators choose to
   use them.

   RDAP includes mechanisms that can be used to authenticate clients,
   allowing servers to support tiered access based on local policy.
   This means that all registration data need no longer be public, and
   personal data or data that may be considered more sensitive can have
   its access restricted to specifically privileged clients.

   RDAP data structures allow servers to indicate via status values when
   data returned to clients has been made private, redacted, obscured,
   or registered by a proxy.  "Private" means that the data is not
   designated for public consumption.  "Redacted" means that some
   registration data fields are not being made available.  "Obscured"
   means that data has been altered for the purposes of not readily
   revealing the actual registration information.  One option that
   operators have available to them to reduce privacy risks to
   registrants is to adopt policies that make use of these status values
   to restrict the registrant data shared with any or all clients

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   according to the sensitivity of the data, the privileges of the
   clients, or some other heuristics.

   RDAP uses the jCard [RFC7095] standard format for entity
   representation.  Operators may find that many of the jCard fields are
   irrelevant for registry operation purposes or that they have no
   reason to collect information from registrants that would correspond
   to certain fields.  Operators wishing to reduce privacy risks for
   registrants may restrict which information they collect and/or which
   fields they populate in responses.

   In addition to privacy risks to registrants, there are also potential
   privacy risks for those who query registration data.  For example,
   the fact that a registry employee performs a particular query may
   reveal information about the employee's activities that he or she
   would have preferred to keep private.  RDAP supports the use of HTTP
   over TLS to provide privacy protection for those querying registrant
   data as well as registrants, unless operational constraints make it
   impossible to meet this requirement.

5.  Security Considerations

   One of the goals of RDAP is to provide security services that do not
   exist in the WHOIS protocol.  This document describes the security
   services provided by RDAP and associated protocol layers, including
   authentication, authorization, availability, data confidentiality,
   and data integrity.  Non-repudiation services were also considered
   and ultimately rejected due to a lack of requirements.  There are,
   however, currently deployed WHOIS servers that can return signed
   responses that provide non-repudiation with proof of origin.  RDAP
   might need to be extended to provide this service in the future.

   As an HTTP-based protocol, RDAP is susceptible to code injection
   attacks.  Code injection refers to adding code into a computer system
   or program to alter the course of execution.  There are many types of
   code injection, including SQL injection, dynamic variable or function
   injection, include-file injection, shell injection, and HTML-script
   injection, among others.  Data confidentiality and integrity services
   provide a measure of defense against man-in-the-middle injection
   attacks, but vulnerabilities in both client- and server-side software
   make it possible for injection attacks to succeed.  Consistently
   checking and validating server credentials can help detect
   man-in-the-middle attacks.

   As noted in Section 3.2.1, digital certificates can be used to
   implement federated authentication.  There is a risk of too
   promiscuous, or even rogue, CAs being included in the list of
   acceptable CAs that the TLS server sends the client as part of the

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   TLS client-authentication handshake and lending the appearance of
   trust to certificates signed by those CAs.  Periodic monitoring of
   the list of CAs that RDAP servers trust for client authentication can
   help reduce this risk.

   The Transport Layer Security protocol [RFC5246] includes a null
   cipher suite that does not encrypt data and thus does not provide
   data confidentiality.  This option MUST NOT be used when data
   confidentiality services are needed.  Additional considerations for
   secure use of TLS are described in [SECURE-TLS-DTLS].

   Data integrity services are sometimes mistakenly associated with
   directory service operational policy requirements focused on data
   accuracy.  "Accuracy" refers to the truthful association of data
   elements (such as names, addresses, and telephone numbers) in the
   context of a particular directory object (such as a domain name).
   Accuracy requirements are out of scope for this protocol.

   Additional security considerations are described in the
   specifications for HTTP [RFC7231], HTTP Basic and Digest access
   authentication [RFC7235], HTTP over TLS [RFC2818], and additional
   HTTP status codes [RFC6585].  Security considerations for federated
   authentication systems can be found in the OAuth [RFC6749] and OpenID
   [OpenID] specifications.

6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000,
              <http://www.rfc-editor.org/info/rfc2818>.

   [RFC6585]  Nottingham, M. and R. Fielding, "Additional HTTP Status
              Codes", RFC 6585, April 2012,
              <http://www.rfc-editor.org/info/rfc6585>.

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              June 2014, <http://www.rfc-editor.org/info/rfc7231>.

   [RFC7235]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Authentication", RFC 7235, June 2014,
              <http://www.rfc-editor.org/info/rfc7235>.

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   [RFC7480]  Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the
              Registration Data Access Protocol (RDAP)", RFC 7480, March
              2015, <http://www.rfc-editor.org/info/rfc7480>.

   [RFC7482]  Newton, A. and S. Hollenbeck, "Registration Data Access
              Protocol (RDAP) Query Format", RFC 7482, March 2015,
              <http://www.rfc-editor.org/info/rfc7482>.

   [RFC7483]  Newton, A. and S. Hollenbeck, "JSON Responses for the
              Registration Data Access Protocol (RDAP)", RFC 7483, March
              2015, <http://www.rfc-editor.org/info/rfc7483>.

6.2.  Informative References

   [OpenID]   OpenID Foundation, "OpenID Authentication 2.0 - Final",
              December 2007, <http://specs.openid.net/auth/2.0>.

   [RFC3707]  Newton, A., "Cross Registry Internet Service Protocol
              (CRISP) Requirements", RFC 3707, February 2004,
              <http://www.rfc-editor.org/info/rfc3707>.

   [RFC3912]  Daigle, L., "WHOIS Protocol Specification", RFC 3912,
              September 2004, <http://www.rfc-editor.org/info/rfc3912>.

   [RFC4732]  Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
              Denial-of-Service Considerations", RFC 4732, December
              2006, <http://www.rfc-editor.org/info/rfc4732>.

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2", FYI
              36, RFC 4949, August 2007,
              <http://www.rfc-editor.org/info/rfc4949>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008,
              <http://www.rfc-editor.org/info/rfc5246>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, May 2008,
              <http://www.rfc-editor.org/info/rfc5280>.

   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, October 2012,
              <http://www.rfc-editor.org/info/rfc6749>.

   [RFC7095]  Kewisch, P., "jCard: The JSON Format for vCard", RFC 7095,
              January 2014, <http://www.rfc-editor.org/info/rfc7095>.

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   [SAML]     OASIS, "Security Assertion Markup Language (SAML) v2.0",
              March 2005, <https://www.oasis-open.org/
              standards#samlv2.0>.

   [SECURE-TLS-DTLS]
              Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of TLS and DTLS", Work in
              Progress, draft-ietf-uta-tls-bcp-09, February 2015.

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Acknowledgements

   The authors would like to acknowledge the following individuals for
   their contributions to this document: Richard Barnes, Marc Blanchet,
   Alissa Cooper, Ernie Dainow, Spencer Dawkins, Jean-Philippe Dionne,
   Byron Ellacott, Stephen Farrell, Tony Hansen, Peter Koch, Murray
   Kucherawy, Barry Leiba, Andrew Newton, and Linlin Zhou.

Authors' Addresses

   Scott Hollenbeck
   Verisign Labs
   12061 Bluemont Way
   Reston, VA  20190
   United States

   EMail: shollenbeck@verisign.com
   URI:   http://www.verisignlabs.com/

   Ning Kong
   China Internet Network Information Center
   4 South 4th Street, Zhongguancun, Haidian District
   Beijing  100190
   China

   Phone: +86 10 5881 3147
   EMail: nkong@cnnic.cn

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