SIP Core R. Shekh-Yusef, Ed. Internet-Draft Avaya Updates: 3261 (if approved) C. Holmberg Intended status: Standards Track Ericsson Expires: January 8, 2020 V. Pascual webrtchacks July 7, 2019 Third-Party Token-based Authentication and Authorization for Session Initiation Protocol (SIP) draft-ietf-sipcore-sip-token-authnz-02 Abstract This document defines a mechanism for SIP, that is based on the OAuth 2.0 and OpenID Connect Core 1.0 specifications, to enable the delegation of the user authentication and SIP registration authorization to a dedicated third-party entity that is separate from the SIP network elements that provide the SIP service. Status of This Memo 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 January 8, 2020. Copyright Notice Copyright (c) 2019 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 Shekh-Yusef, et al. Expires January 8, 2020 [Page 1]
Internet-Draft 3rd-Party Token-based AuthNZ for SIP July 2019 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. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. SIP User Agent Types . . . . . . . . . . . . . . . . . . 3 2. Authentication and Authorization flow . . . . . . . . . . . . 4 2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1.1. Configured AS . . . . . . . . . . . . . . . . . . . . 4 2.1.2. Discovered AS . . . . . . . . . . . . . . . . . . . . 6 2.2. Initial Registration . . . . . . . . . . . . . . . . . . 7 2.3. Subsequent Registrations . . . . . . . . . . . . . . . . 8 2.4. Non-Registration Requests . . . . . . . . . . . . . . . . 8 3. WWW-Authenticate Response Header Field . . . . . . . . . . . 8 4. 'sip.token' Media Feature Tag . . . . . . . . . . . . . . . . 9 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 6.1. SIP Media Feaure Tag . . . . . . . . . . . . . . . . . . 10 6.1.1. sip.token . . . . . . . . . . . . . . . . . . . . . . 10 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 8. Normative References . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 1. Introduction The SIP protocol [RFC3261] uses the framework used by the HTTP protocol for authenticating users, which is a simple challenge- response authentication mechanism that allows a server to challenge a client request and allows a client to provide authentication information in response to that challenge. Shekh-Yusef, et al. Expires January 8, 2020 [Page 2]
Internet-Draft 3rd-Party Token-based AuthNZ for SIP July 2019 OAuth 2.0 [RFC6749] defines a token based authorization framework to allow clients to access resources on behalf of their user. The OpenID Connect 1.0 [OPENID] specifications defines a simple identity layer on top of the OAuth 2.0 protocol, which enables clients to verify the identity of the user based on the authentication performed by a dedicated authorization server, as well as to obtain basic profile information about the user. This document defines an mechanism for SIP, that is based on the OAuth 2.0 and OpenID Connect Core 1.0 specifications, to enable the delegation of the user authentication and SIP registration authorization to a dedicated third-party entity that is separate from the SIP network elements that provide the SIP service. 1.1. Terminology 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]. 1.2. SIP User Agent Types [RFC6749] defines two types of clients, confidential and public, that apply to the SIP User Agents. o Confidential User Agent: is a SIP UA that is capable of maintaining the confidentiality of the user credentials and any tokens obtained using these user credentials. o Public User Agent: is a SIP UA that is incapable of maintainings the confidentiality of the user credentials and any obtained tokens. Shekh-Yusef, et al. Expires January 8, 2020 [Page 3]
Internet-Draft 3rd-Party Token-based AuthNZ for SIP July 2019 2. Authentication and Authorization flow This flow is used by a Confidential UA with rich UI to authenticate to an authorization server and to directly obtain tokens to be able to register and get service from the SIP network. 2.1. Overview The following sections provide overview of the supported flows. 2.1.1. Configured AS The following figure provides a high level view of flow of messages when the UA is aware of the AS ahead of time: UA Registrar AS --------------------------------------------------------------------- | | | [00] The UA prompts the user to provides his credentials | | | | | [01] HTTP POST /token | | |-------------------------------------------------------------->| | | | | [02] 200 OK {access_token, refresh_token, [id_token]} | |<--------------------------------------------------------------| | | | | | | | [03] REGISTER | | | Authorization: Bearer <access_token> | |------------------------------>| | | | | | | [04] HTTP POST /introspect | | | {access_token} | | |------------------------------>| | | | | | [05] 200 OK {metadata} | | |<------------------------------| | | | | [06] 200 OK | | |<------------------------------| | | | | Shekh-Yusef, et al. Expires January 8, 2020 [Page 4]
Internet-Draft 3rd-Party Token-based AuthNZ for SIP July 2019 In step [00], the UA collects the user's credentials with the AS. In steps [01] and [02], the UA first contacts the Authorization Server to authenticate the user and obtain tokens to be used to get access to the SIP network. The tokens returned to the UA depend on the type of server: with an OAuth Authorization Server, the tokens provided are the access token and refresh token. With an OpenID Connect server, an additional ID- Token is returned, which contains the SIP URI of the user. The method used to authenticate the user and obtain these tokens is out of scope for this document. In step [03], the UA starts the registration process with the SIP registrar by sending a REGISTER request with the access token it obtained previously. The registrar validates the access token, and if the access token provided by the UA is an opaque token, then the registrar MAY perform an introspection, steps [04] and [05], to obtain more information about the token and its scope, as per [RFC7662]. Otherwise, after the registrar validates the token to make sure it was signed by a trusted entity, it inspects its claims and act upon it. When the registrar is satisfied with the token, it then replies with the 200 OK to complete the registration process. Shekh-Yusef, et al. Expires January 8, 2020 [Page 5]
Internet-Draft 3rd-Party Token-based AuthNZ for SIP July 2019 2.1.2. Discovered AS The following figure provides a high level view of flow of messages when the UA discovers the AS to conatc from the registrar: UA Registrar AS --------------------------------------------------------------------- | | | | [07] REGISTER | | |------------------------------>| | | | | | [08] 401 Unauthorized | | | WWW-Authenticate: Bearer "authz_server"="<authz_server>" | |<------------------------------| | | | | [09] The UA prompts the user to provides his credentials | | | | | [10] HTTP POST /token | | |-------------------------------------------------------------->| | | | | [11] 200 OK {access_token, refresh_token, [id_token]} | |<--------------------------------------------------------------| | | | | [12] REGISTER | | | Authorization: Bearer <access_token> | |------------------------------>| | | | [13] HTTP POST /introspect | | | {access_token} | | |------------------------------>| | | | | | [14] 200 OK {metadata} | | |<------------------------------| | | | | [15] 200 OK | | |<------------------------------| | | | | In step [07] the UA starts the registration process by sending a SIP REGISTER request to the registrar without any credentials. The REGISTER request includes an indication that the UA supports token- based autentication in the form of sip.token media feature tag. The registrar then challenges the UA, in step [08], by responding with 401 Unauthorized and includes the authorization server to contact to obtain a token. In step [09], the UA collects the user's credentials with the AS. Shekh-Yusef, et al. Expires January 8, 2020 [Page 6]
Internet-Draft 3rd-Party Token-based AuthNZ for SIP July 2019 In steps [10] and [11], the UA contacts the Authorization Server to authenticate the user and obtain tokens to be used to get access to the SIP network. The tokens returned to the UA depend on the type of server: with an OAuth Authorization Server, the tokens provided are the access token and refresh token. With an OpenID Connect server, an additional ID- Token is returned, which contains the SIP URI of the user. The method used to authenticate the user and obtain these tokens is out of scope for this document. In step [12], the UA retries the registration process with the SIP registrar by sending a REGISTER request with the access token it obtained previously. The registrar validates the access token, and if the access token provided by the UA is an opaque token, then then registrar MAY perform an introspection, steps [13] and [14], to obtain more information about the token and its scope, as per [RFC7662]. Otherwise, after the registrar validates the token to make sure it was signed by a trusted entity, it inspects its claims and act upon it. 2.2. Initial Registration If the UA has already obtained a token, then the UA starts the registration process, step [03], by sending a REGISTER request, with the access token in the Authorization header, to the registrar. If the UA does not have a token, then the UA starts the registration process, step [07], by sending a REGISTER request without an Authorization header. The registrar MUST then challenge the UA by responding with 401 Unauthorized and include the WWW-Authenticate Response Header Field which includes the server to contact to obtain a token, as specified in Section 3 The REGISTER request SHOULD include a sip.token media feature tag in the Contact header field of the request, unless it knows (e.g., by means of configuration) that the registrar supports the token authentication mechanism. The UA MUST include an Authorization header field with the Bearer scheme in the request to carry the access token, as specified in [RFC6750]. When the registrar is satisfied with the token, it then replies with the 200 OK to complete the registration process. Shekh-Yusef, et al. Expires January 8, 2020 [Page 7]
Internet-Draft 3rd-Party Token-based AuthNZ for SIP July 2019 2.3. Subsequent Registrations All subsequent REGISTER requests from the UA MUST include a valid access token. The UA MUST obtain a new access token before the access token expiry period to continue to get service from the system. The method used to obtain a new fresh access tokens is out of scope for this document. The REGISTER request SHOULD include a sip.token media feature tag in the Contact header field of the request, unless it knows (e.g., by means of configuration) that the registrar supports the token authentication mechanism. 2.4. Non-Registration Requests The UA MUST NOT insert a token in a non-REGISTER request, unless the non-REGISTER request has been challenged, or the peer is considered a trusted entity. If a non-REGISTER request from the UA is challenged with a WWW- Authenticate header field to provide credentials for the same realm specified in the challenge to the registration request, then the UA MUST include a valid access token in the request retry. The UA MUST include an Authorization header field with the Bearer scheme in the request to carry the access token, as specified in [RFC6750]. Challenges with WWW-Authenticate with different realm specified in the challenge to the registration request are out of scope for this document. Challenges with Proxy-Authenticate are out of scope for this document. 3. WWW-Authenticate Response Header Field This section describes the syntax of the WWW-Authenticate Response Header Field when used with the Bearer scheme to challenge the UA for credentials. challenge =/ ("Bearer" LWS bearer-cln *(COMMA bearer-cln)) bearer-cln = realm / scope / authz-server / error / auth-param authz-server = "authz_server" EQUAL authz-server-value authz-server-value = quoted-string The realm and auth-param parameters are defined in [RFC3261]. Shekh-Yusef, et al. Expires January 8, 2020 [Page 8]
Internet-Draft 3rd-Party Token-based AuthNZ for SIP July 2019 As per [RFC3261], the realm string alone defines the protection domain. [RFC3261] states that the realm string must be globally unique and recommends that the realm string contains a hostname or domain name. It also states that the realm string should be human- readable identifier that can be rendered to the user. The scope and error parameters are defined in [RFC6749]. The scope parameter could be used by the registrar/proxy to indicate to the UAC the minimum scope that must be associated with the access token to be able to get service. As defined in [RFC6749], the value of the scope parameter is expressed as a list of space-delimited, case-sensitive strings. The strings are defined by the authorization server. The values of the scope parameter is out of scope for this document. The error parameter could be used by the registrar/proxy to indicate to the UAC the reason for the error, with possible values of "invalid_token" or "invalid_scope". 4. 'sip.token' Media Feature Tag The sip.token media feature tag, when inserted in the Contact header field of a SIP REGISTER request, conveys that the SIP UA associated with the tag supports a token based authentication mechanism, where the user authentication and SIP registration authorization is performed by a third party. The media feature tag has no values. token-mt = "+sip.token" 5. Security Considerations The UAC MUST always make sure that it is communicating with the right registrar/proxy using TLS and proper validation of the server certificate and the identifier in that certificate to protect the access token in transit. If the token being used is a bearer token as specified in [RFC6750], then the security considration of that document apply. If the token being used is a JWT as specified in [RFC7519], then the security considration of that document apply. Shekh-Yusef, et al. Expires January 8, 2020 [Page 9]
Internet-Draft 3rd-Party Token-based AuthNZ for SIP July 2019 6. IANA Considerations 6.1. SIP Media Feaure Tag 6.1.1. sip.token This section defines a new media feature tag that extends the "SIP Media Feature Tag Registration Tree" subregistry [RFC3840] under the "Media Feature Tags" registry (https://www.iana.org/assignments/ media-feature-tags). Media feature tag name: sip.token Summary of the media feature indicated by this feature tag: This media feature tag, when inserted in the Contact header field of a SIP REGISTER request, conveys that the SIP UA associated with the tag supports a token based authentication mechanism, where the user authentication and SIP registration authorization is performed by a third party. Values appropriate for use with this feature tag: none Related standards or documents: RFC XXXX Security considerations: This media feature tag does not introduce new security considerations, as it simply indicates support for a basic SIP feature. However, if an attacker manages to remove the media feature tag from a SIP REGISTER request, the SIP UA that inserted it might not be able to authenticate itself with the SIP registrar to which the SIP request is addressed, as the SIP registrar might not be aware that the SIP UA supports the feature associated with the media feature tag. Contact: IESG (iesg@ietf.org) 7. Acknowledgments The authors would also like to thank Paul Kyzivat for his reviews and feedback on this document. The authors would also like to thank the following for their review and feedback of the original document that was replaced with this document: Shekh-Yusef, et al. Expires January 8, 2020 [Page 10]
Internet-Draft 3rd-Party Token-based AuthNZ for SIP July 2019 Andrew Allen, Martin Dolly, Keith Drage, Paul Kyzivat, Jon Peterson, Michael Procter, Roy Radhika, Matt Ryan, Ivo Sedlacek, Roman Shpount, Robert Sparks, Asveren Tolga, and Dale Worley. 8. Normative References [OPENID] Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and C. Mortimore, "OpenID Connect Core 1.0", February 2014. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>. [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, DOI 10.17487/RFC3261, June 2002, <https://www.rfc-editor.org/info/rfc3261>. [RFC3840] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Indicating User Agent Capabilities in the Session Initiation Protocol (SIP)", RFC 3840, DOI 10.17487/RFC3840, August 2004, <https://www.rfc-editor.org/info/rfc3840>. [RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012, <https://www.rfc-editor.org/info/rfc6749>. [RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization Framework: Bearer Token Usage", RFC 6750, DOI 10.17487/RFC6750, October 2012, <https://www.rfc-editor.org/info/rfc6750>. [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, DOI 10.17487/RFC7231, June 2014, <https://www.rfc-editor.org/info/rfc7231>. [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, <https://www.rfc-editor.org/info/rfc7519>. Shekh-Yusef, et al. Expires January 8, 2020 [Page 11]
Internet-Draft 3rd-Party Token-based AuthNZ for SIP July 2019 [RFC7523] Jones, M., Campbell, B., and C. Mortimore, "JSON Web Token (JWT) Profile for OAuth 2.0 Client Authentication and Authorization Grants", RFC 7523, DOI 10.17487/RFC7523, May 2015, <https://www.rfc-editor.org/info/rfc7523>. [RFC7662] Richer, J., Ed., "OAuth 2.0 Token Introspection", RFC 7662, DOI 10.17487/RFC7662, October 2015, <https://www.rfc-editor.org/info/rfc7662>. Authors' Addresses Rifaat Shekh-Yusef (editor) Avaya 425 Legget Drive Ottawa, Ontario Canada Phone: +1-613-595-9106 EMail: rifaat.ietf@gmail.com Christer Holmberg Ericsson Hirsalantie 11 Jorvas 02420 Finland EMail: christer.holmberg@ericsson.com Victor Pascual webrtchacks Spain EMail: victor.pascual.avila@gmail.com Shekh-Yusef, et al. Expires January 8, 2020 [Page 12]
