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Internet Engineering Task Force (IETF)                     S. HollenbeckRequest for Comments: 7481                                 Verisign LabsCategory: Standards Track                                        N. KongISSN: 2070-1721                                                    CNNIC                                                              March 2015Security 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 inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://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 toBCP 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.Hollenbeck & Kong            Standards Track                    [Page 1]

RFC 7481                 RDAP Security Services               March 2015Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .22.  Conventions Used in This Document . . . . . . . . . . . . . .22.1.  Acronyms and Abbreviations  . . . . . . . . . . . . . . .33.  Information Security Services and RDAP  . . . . . . . . . . .33.1.  Access Control  . . . . . . . . . . . . . . . . . . . . .33.2.  Authentication  . . . . . . . . . . . . . . . . . . . . .33.2.1.  Federated Authentication  . . . . . . . . . . . . . .43.3.  Authorization . . . . . . . . . . . . . . . . . . . . . .63.4.  Availability  . . . . . . . . . . . . . . . . . . . . . .63.5.  Data Confidentiality  . . . . . . . . . . . . . . . . . .73.6.  Data Integrity  . . . . . . . . . . . . . . . . . . . . .74.  Privacy Threats Associated with Registration Data . . . . . .85.  Security Considerations . . . . . . . . . . . . . . . . . . .96.  References  . . . . . . . . . . . . . . . . . . . . . . . . .106.1.  Normative References  . . . . . . . . . . . . . . . . . .106.2.  Informative References  . . . . . . . . . . . . . . . . .11   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .13   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .131.  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].Hollenbeck & Kong            Standards Track                    [Page 2]

RFC 7481                 RDAP Security Services               March 20152.1.  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 Security3.  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 (seeSection 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.Hollenbeck & Kong            Standards Track                    [Page 3]

RFC 7481                 RDAP Security Services               March 2015   WHOIS does not provide features to identify and authenticate clients.   As noted inSection 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 (seeSection 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 clientHollenbeck & Kong            Standards Track                    [Page 4]

RFC 7481                 RDAP Security Services               March 2015   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 inSection 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.  ThisHollenbeck & Kong            Standards Track                    [Page 5]

RFC 7481                 RDAP Security Services               March 2015   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 inSection 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 (seeSection 3.2).   Server operators MAY offer varying degrees of access depending on   policy and need in conjunction with the authentication methods   described inSection 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 inSection 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 oneHollenbeck & Kong            Standards Track                    [Page 6]

RFC 7481                 RDAP Security Services               March 2015   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 inSection 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 inSection 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 theHollenbeck & Kong            Standards Track                    [Page 7]

RFC 7481                 RDAP Security Services               March 2015   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 clientsHollenbeck & Kong            Standards Track                    [Page 8]

RFC 7481                 RDAP Security Services               March 2015   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 inSection 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 theHollenbeck & Kong            Standards Track                    [Page 9]

RFC 7481                 RDAP Security Services               March 2015   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.  References6.1.  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>.Hollenbeck & Kong            Standards Track                   [Page 10]

RFC 7481                 RDAP Security Services               March 2015   [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>.Hollenbeck & Kong            Standards Track                   [Page 11]

RFC 7481                 RDAP Security Services               March 2015   [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.Hollenbeck & Kong            Standards Track                   [Page 12]

RFC 7481                 RDAP Security Services               March 2015Acknowledgements   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.cnHollenbeck & Kong            Standards Track                   [Page 13]