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Versions: 00 01 02 03 04

SIPCore                                              R. Shekh-Yusef, Ed.
Internet-Draft                                                     Avaya
Updates: 3261 (if approved)                                   V. Pascual
Intended status: Standards Track                                  Quobis
Expires: October 15, 2015                                 April 13, 2015


              The Session Initiation Protocol (SIP) OAuth
                    draft-yusef-sipcore-sip-oauth-02

Abstract

   This document defines an authorization framework for SIP that is
   based on the OAuth 2.0 framework, and adds a simple identity layer on
   top of that, based on the OpenID Connect Core 1.0, to enable Clients
   to verify the identity of the End-User based on the authentication
   performed by an Authorization Server, as well as to obtain basic
   profile information about the End-User.

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
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   This Internet-Draft will expire on October 15, 2015.

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
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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of



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   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
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   3
     1.3.  Roles . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.4.  ID Token  . . . . . . . . . . . . . . . . . . . . . . . .   5
     1.5.  Authentication  . . . . . . . . . . . . . . . . . . . . .   5
   2.  Benefits  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.1.  Challenges  . . . . . . . . . . . . . . . . . . . . . . .   6
     2.2.  Single Sign-On  . . . . . . . . . . . . . . . . . . . . .   6
     2.3.  Level of Service  . . . . . . . . . . . . . . . . . . . .   6
     2.4.  Third-Party Authorization . . . . . . . . . . . . . . . .   6
   3.  Authorization Code Grant type . . . . . . . . . . . . . . . .   6
     3.1.  Enterprise SSO Use Case . . . . . . . . . . . . . . . . .   6
     3.2.  Operations Overview . . . . . . . . . . . . . . . . . . .   6
     3.3.  Registration  . . . . . . . . . . . . . . . . . . . . . .   9
     3.4.  Authorization . . . . . . . . . . . . . . . . . . . . . .   9
     3.5.  Acquiring ID Token  . . . . . . . . . . . . . . . . . . .  10
     3.6.  Token Refresh . . . . . . . . . . . . . . . . . . . . . .  11
     3.7.  Authenticated Requests  . . . . . . . . . . . . . . . . .  11
     3.8.  Services  . . . . . . . . . . . . . . . . . . . . . . . .  12
   4.  Resource Owner Password Credentials Grant type  . . . . . . .  12
     4.1.  SIP SSO . . . . . . . . . . . . . . . . . . . . . . . . .  12
     4.2.  Operations Overview . . . . . . . . . . . . . . . . . . .  12
     4.3.  Registration and Acquiring Tokens . . . . . . . . . . . .  14
     4.4.  Discarding Credentials  . . . . . . . . . . . . . . . . .  15
     4.5.  Token Refresh . . . . . . . . . . . . . . . . . . . . . .  15
     4.6.  Authenticated Requests  . . . . . . . . . . . . . . . . .  15
     4.7.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  16
   5.  Client Credentials Grant  . . . . . . . . . . . . . . . . . .  16
     5.1.  Registration  . . . . . . . . . . . . . . . . . . . . . .  17
     5.2.  Authorization . . . . . . . . . . . . . . . . . . . . . .  17



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   6.  Outbound  . . . . . . . . . . . . . . . . . . . . . . . . . .  18
     6.1.  Authorization Code Grant type . . . . . . . . . . . . . .  18
     6.2.  Resource Owner Password Credentials Grant type  . . . . .  18
     6.3.  Client Credentials Grant type . . . . . . . . . . . . . .  19
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  19
   10. Normative References  . . . . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

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.

   The SIP protocol does not have an authorization framework to allow
   the system to control access to various services provided by the
   system.

   OAuth 2.0 [RFC6749] defines a token based authorization framework to
   allow clients to access resources on behalf of their user.  It also
   defines four types of authorization grants, which the client uses to
   request the access token.

   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 End-User based on the
   authentication performed by an Authorization Server, as well as to
   obtain basic profile information about the End-User.

   This document defines an authorization framework for SIP that is
   based on the OAuth 2.0 framework, and adds the identity layer on top
   of that, based on the OpenID Connect Core 1.0 specification

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.  Definitions

      Types of SIP services:





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      *  Basic SIP Services: make/receive call, transfer, call forward,
         etc.

      *  Advanced SIP Services: services provided by SIP application
         servers, e.g.  Voice Mail, Conference Services, Presence, IM,
         ...

      Single Sign-On (SSO)

         SSO is a property that allows the user to be authenticated once
         and as a result have access to multiple services in the system.

      Authentication

         The process of verifying the identity of a user trying to get
         access to some network services.

      Authorization

         The process of controlling an authenticated user access to
         network services and the level of service provided to the user.

1.3.  Roles

      resource owner

         An entity capable of granting access to a protected resource.
         When the resource owner is a person, it is referred to as an
         end-user.

      resource server

         The server hosting the protected resources, capable of
         accepting and responding to protected resource requests using
         access tokens.

      OAuth 2.0 client

         An application making protected resource requests on behalf of
         the resource owner and with its authorization.  The term
         "client" does not imply any particular implementation
         characteristics (e.g., whether the application executes on a
         server, a desktop, or other devices).

      SIP client

         An application making requests to access SIP services on behalf
         of the end-user.



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      authorization server

         The server issuing access tokens to the OAuth 2.0 client after
         successfully authenticating the resource owner and obtaining
         authorization, or the server issuing ID tokens to the SIP
         client after successfully authenticating the end-user.

      proof-of-possession (pop)

         A hash used by one party to prove to another party that it is
         in possession of some shared credentials, without sending the
         credentials on the wire.

1.4.  ID Token

   RFC6749 defines two types of tokens: access token and refresh token.
   This document defines a new token: ID Token as defined in [OPEN-ID].

   ID tokens are credentials used by the SIP client to access SIP
   services on behalf of the end-user.

   An ID token is a string representing an authorization issued to the
   SIP client.  The string is usually opaque to the SIP client.  Tokens
   represent specific scopes and durations of access, granted by the SIP
   system, and enforced by the SIP proxy, SIP application servers, and
   the authorization server.

1.5.  Authentication

   There are two types of user authentications in SIP:

   o  Proxy-to-User: which allows a server that is providing a service
      to authenticate a user before providing the service.

   o  User-to-User: which allows a user recieving a request to
      authenticate the identity of the remote user before processing the
      request.

   The mechanism defined in this document addresses the proxy-to-user
   authentication only.  For user-to-user authentication, please refer
   to the mechanism defined in STIR.

2.  Benefits

   This section describes the benefit of this authorization framework:






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2.1.  Challenges

   With the existing mechanism, the proxy and application servers might
   need to challenge many of the requests sent by a client, which adds
   traffic that could be avoided with this authorization mechanism.

2.2.  Single Sign-On

   Single Sign-On is a property that allows the user to be authenticated
   once and as a result have access to multiple services in the system.

   This authorization mechanism would enable Single Sign-On, as the user
   will be authenticated once and as a result given a token and a
   refresh token to allow the user access to various services based on
   the token scope.

2.3.  Level of Service

   This authorization mechanism allows the application server to control
   the level of service provided to the user based on the token scope.

2.4.  Third-Party Authorization

   This authorization mechanism allows the user to be authenticated and
   obtain tokens using some Third-Party Authorization mechanism and
   still get services from the system.

3.  Authorization Code Grant type

3.1.  Enterprise SSO Use Case

   An enterprise is interested in providing its users with an SSO
   capability to the corporate various services.  The enterprise has an
   authorization server for controlling the user access to their network
   and would like to extend that existing authorization server to
   control the user access to the various services provided by their SIP
   network.

   The user is expected to provide his corporate credentials to login to
   the corporate network and get different types of services, regardless
   of the protocol used to provide the service, and without the need to
   create different accounts for these different types of services.

3.2.  Operations Overview

   The following figure provides a high level view of flow of messages
   for the Authorization Code Grant type:




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   User                            Proxy                   Authorization
   Agent                                                          Server
   ---------------------------------------------------------------------
     |                               |                               |
     | F1 REGISTER                   |                               |
     |------------------------------>|                               |
     |                        F2 401 |                               |
     |<------------------------------|                               |
     |                               |                               |
     | F3 GET /authorize?response_type=code&...                      |
     |-------------------------------------------------------------->|
     |                               |                        F4 401 |
     |<--------------------------------------------------------------|
     |                               |                               |
     |                               |                               |
   o master-key = HMAC-SHA256(HA1, realm + nonce)                    |
     |                               |                               |
     | F5 GET /authorize?response_type=code&... with credentials     |
     |-------------------------------------------------------------->|
     |                               |                               |
     |                               |                               |
     |                      o master-key=HMAC-SHA256(HA1, realm + nonce)
     |                               |                               |
     |                               |                 F6 200 [code] |
     |<--------------------------------------------------------------|
     |                               |                               |
     |                               |                               |
     |                               |                               |
     | F7 REGISTER code, pop         |                               |
     |------------------------------>|                               |
     |                               | F8 POST /id-token [code]      |
     |                               |------------------------------>|
     |                               | F9 200 OK [ id-token,         |
     |                               |             refresh token,    |
     |                               |             master-key]       |
     |                               |<------------------------------|
     |                    F10 200 OK |                               |
     |<------------------------------|                               |
     |                               |                               |
     |                               |                               |
     :
     :


   Subsequent Requests

     |                               |                               |
   o pop = HMAC-SHA256(master-key, digest-string)                    |



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     |                               |                               |
     | F11 INVITE pop                |                               |
     |------------------------------>|                               |
     |                               |                               |
     |                               |                               |
     |               o The proxy verifies the pop.                   |
     |                               |                               |
     |              F12 180 Ringing  |                               |
     |<------------------------------|                               |
     |                               |                               |
     :
     :


   Token Refresh

     |                               |                               |
     |                               | F13 POST /id-token            |
     |                               |   [ grant_type=refresh_token& |
     |                               |     refresh_token=<ref_token> |
     |                               |------------------------------>|
     |                               |  F14 200 OK [ id-token,       |
     |                               |               refresh_token ] |
     |                               |<------------------------------|
     |                               |                               |



   During registration, if the UA is in possession of a valid ID Token,
   the UA could use the token to register with the proxy; otherwise, the
   UA initially sends a REGISTER request (F1) without providing any
   credentials.

   The proxy challenges the UA by responding with 401 (F2) that includes
   the address of the Authorization Server.

   [[OPEN ISSUE]] How should the UA be redirected to the Authorization
   Server: 1.  New SIP parameter? 2.  Extend the Bearer scheme? 3.
   Define a new Scheme?

   The UA will then contact the Authorization Server without providing
   any credentials in the first request (F3).  The Authorization Server
   challenges the request using the Digest scheme (F4), and the client
   retries the request (F5) and provide the user's credentials.

   The Authorization Server verifies the request from the client; if the
   verification is successful, the Authorization Server responds with
   200 OK (F6) includes a code in the body part.



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   The UA then retries the request (F7) and include the code in the body
   of the request.  The proxy then contacts the Authorization Server and
   exchanges the code for a token (F8 and F9).

3.3.  Registration

   The UA initiates the process by sending a REGISTER request (F1) to
   the proxy.  The proxy will redirect the UA to the Authorization
   Server by responding with 401 (F2) that include the address of the
   Authorization Server in the form of an HTTP URI.

   The UA will then follow the authorization steps defined in section
   3.4.  At the end of the authorization process the UA will have a code
   that it will use to complete the registration process.

   The UA will send a new REGISTER request (F7) and include the code in
   the body of the request with the following parameters:

   grant_type (REQUIRED)

      Value MUST be set to "authorization_code".

   code (REQUIRED)

      The authorization code received from the authorization server.

   The proxy will then use the code to get a token from the
   Authorization Server as defined in section 3.5.  If the proxy is able
   to obtain the token, the proxy will respond with 200 OK (F10) to the
   UA to complete the registration process.

3.4.  Authorization

   The UA constructs the initial request (F3) without providing any user
   credentials, but with the following URI parameters in the query
   component:

   response_type (REQUIRED)

      Value MUST be set to "code".

   user_id (REQUIRED)

      The user's address-of-record (AOR).

   scope (OPTIONAL)

      The scope of the access request as described by Section x.x.



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   state (RECOMMENDED)

      The value of this parameter is a nonce created by the client to
      prevent replay attack.  The nonce is a uniquely generated value
      for each request.  This parameter might not be included with the
      initial request that does not include credentials (F3).

   The Authorization Server uses the user's AOR specified in the user_id
   parameter to verify that the user has an account in the system, and
   then challenges the request by responding with 401 (F4) with Digest
   scheme.

   The UA will generate a master-key that is based on an HMAC-Hash
   algorithm, e.g.  HMAC-SHA256, that takes an input the user's HA1 and
   the concatenation of realm and nonce received in the challenge from
   the server.

   The UA will then send a new authorization request (F5), but this time
   include the credentials requested by the server.  The UA will use the
   same parameters values used in the initial authorization request with
   the exception of the state parameter which will get a new nonce
   value.

   When the server receives the request with the credentials (F5), the
   server will verify the digest provided by the UA; if that is
   successful, the server will respond with 302 (F6) and include a code
   in the body of the response with the following parameters:

   grant_type (REQUIRED)

      Value MUST be set to "authorization_code".

   code (REQUIRED)

      The authorization code received from the authorization server.

   The server then generates a master-key that is based on an HMAC-Hash
   algorithm, e.g.  HMAC-SHA256, that takes an input the user's HA1, and
   the concatenation of realm and nonce sent in the challenge (F4) to
   the client.

3.5.  Acquiring ID Token

   The proxy receives the REGISTER request (F7) that includes a body
   with a code obtained during authorization (section 3.4).  The proxy
   will then contact the Authorization Server to exchange the code with
   an ID Token.




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   The proxy sends a POST request (F8) to the Authorization Server and
   include the following parameters in the body:

   grant_type (REQUIRED)

      Value MUST be set to "authorization_code".

   code (REQUIRED)

      The authorization code received from the authorization server.

   If the request is valid and authorized, the authorization server
   responds with a 200 OK (F9) to complete the registration process,
   with id_token, token_refresh, and the master-key in the body.

3.6.  Token Refresh

   The proxy makes a refresh request to the token by sending a refresh
   POST request (F13) that includes a body with the grant_type and the
   refresh_token.

   For example:

      grant_type=refresh_token&refresh_token=<refresh_token>

   If the proxy fails to refresh the token, then it MUST challenge the
   next request from the UA, and as a result the UA MUST go through the
   authorization process defined in section 3.4 to obtain new tokens.

3.7.  Authenticated Requests

   When the UA wants to send any request to the proxy, it MUST include
   the Authorization header and use the Bearer scheme to carry the
   proof-of-possession of the master-key.

   The pop is calculated using the master-key as follows:

      pop = HMAC-SHA256(master-key, digest-string)

   The following is an example of an Authorization header with Bearer
   scheme:

      Authorization: Bearer pop=<pop>

   See rfc4474, section 9, for the SIP headers to hash to create digest-
   string.





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   [[OPEN ISSUE]] The Bearer scheme is used to deliver tokens without
   providing any proof of possession.  We probably need to use different
   scheme later on.

3.8.  Services

   When the UA tries to access a service on behalf of a user, e.g.
   Voice Mail Service, the proxy forwards the request to the server
   providing the service and MUST include an Authorization header with
   the Bearer scheme that carries the token needed to get service, as
   follows:

      Authorization: Bearer token=<token>

4.  Resource Owner Password Credentials Grant type

4.1.  SIP SSO

   An enterprise is interested in providing its users with an SSO
   capability to the corporate various SIP services.

   The enterprise wants to control the services provided to their SIP
   users and the level of service provided to the user by their SIP
   application servers without the need to create different accounts for
   these services.

   The enterprise wants to utilize an existing authentication mechanism
   provided by SIP, but would like to be able to control who gets access
   to what service and when.

   The user is expected to use his SIP credentials to login to the SIP
   network and get access to the basic services, and to get access to
   the services provided by the various SIP application servers without
   being challenged to provide credentials for each type of service.

4.2.  Operations Overview

   The following figure provides a high level view of flow of messages
   for the Resource Owner Password Credentials Grant type:












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     UA                                                           Proxy
   --------------------------------------------------------------------
     |                                                              |
     | F1 REGISTER                                                  |
     |------------------------------------------------------------->|
     |                                                              |
     |                              F2 401 WWW-Authenticate: Digest |
     |<-------------------------------------------------------------|
     |                                                              |
     |                                                              |
   o master-key = HMAC-SHA256(HA1, realm + nonce)                   |
     |                                                              |
     | F3 REGISTER with Authorization                               |
     |------------------------------------------------------------->|
     |                                                              |
     |                                                              |
     |                    o master-key = HMAC-SHA256(HA1, realm + nonce)
     |                                                              |
     |                              F4 200 OK [token, expires, ...] |
     |<-------------------------------------------------------------|
     |                                                              |
     |                                                              |
   o pop = HMAC-SHA256(master-key, token + digest-string)           |
     |                                                              |
     | F5 INVITE token, pop                                         |
     |------------------------------------------------------------->|
     |                                                              |
     |                                    o The server verifies the pop.
     |                                                              |
     |                                               F6 180 Ringing |
     |<-------------------------------------------------------------|
     |                                                              |



   During registration the UA initially sends a REGISTER request (F1)
   without providing any credentials.

   The proxy then challenges the UA by responding with 401 (F2) that
   includes the Digest scheme in the www-authenticate header.

   The UA will generate a master-key that is based on an HMAC-Hash
   algorithm, e.g.  HMAC-SHA256, that takes an input the user's HA1 and
   the concatenation of realm and nonce received in the challenge from
   the server.  The UA will continue to use the existing operation of
   handling the Digest challenge and then sends a new REGISTER request
   (F3) with the credentials to the server.




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   When the server receives the request with the credentials (F3), the
   server will verify the digest provided by the UA; if that is
   successful, the server will accept the registration (F4) and include
   the details of the token in the response.

   The server then generates a master-key that is based on an HMAC-Hash
   algorithm, e.g.  HMAC-SHA256, that takes an input the user's HA1, and
   the concatenation of realm and nonce sent in the challenge to the
   client.

   At the end of the above process the UA would have registered with the
   proxy and both the UA and the proxy would have created the same
   master-key without sending the master-key on the wire.

   Later when the UA wants to send a request to the proxy it MUST always
   include the token and SHOULD include the pop as defined in section
   4.6.

4.3.  Registration and Acquiring Tokens

   The UA MUST request the access token during the registration process
   with the proxy, by including a body with the grant_type as
   "password".  Initially, the UA sends a REGISTER request without
   providing any credentials.

   The proxy MUST then challenge the UA by responding with 401 with the
   Digest scheme in the WWW-Authenticate header.

   When the UA gets challenged by the proxy to provide its credentials,
   the UA MUST include its credentials in the new REGISTER request in
   the authorization header as it is done with the existing mechanism,
   and MUST include a body with the grant_type as "password".

   In addition, the UA MUST generate a master-key as follows:

      master-key = HMAC-SHA256(HA1, realm + nonce)

   Where

   o  HA1 - this is the user's H(A1) as defined in [DIGEST].

   o  realm - this is the realm that is returned by the server in the
      response to the initial request from the UA.

   o  nonce - this is the nonce that is returned by the server in the
      response to the initial request from the UA.





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   When the server receives the request with the credentials, the server
   will verify the digest provided by the UA; if that is successful, the
   server will accept the registration and include the details of the
   token in the response.

   [[OPEN ISSUE]] How should the tokens be transported to the UA? in the
   body of the 200 OK? or a SIP header?

   The server then generates a master-key following the same procedure
   followed by the client.

   As a result of this procedure both the UA and the server would have
   created the same master-key without sending the master-key on the
   wire.

4.4.  Discarding Credentials

   After successfully receiving the access and refresh tokens from the
   proxy, the UA SHOULD discard the user credentials.

4.5.  Token Refresh

   The UA makes a refresh request to the token by sending a refresh
   REGISTER request that includes the authorization header and a body
   with the grant_type, the refresh_token, and the proof-of-possession
   of the master-key.

   For example:

      grant_type=refresh_token&refresh_token=<refresh_token>&pop=<pop>

4.6.  Authenticated Requests

   When the UA wants to send any request to the proxy, it MUST include
   the Authorization header and use the Bearer scheme to carry the
   access token, and the proof-of-possession of the master-key.

   For example:

      Authorization: Bearer token=<token>, pop=<pop>

   See rfc4474, section 9, for the SIP headers to hash to create the
   value for the proof.

   [[OPEN ISSUE]] The Bearer scheme is used to deliver tokens without
   providing any proof of possession.  We probably need to use different
   scheme later on.




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4.7.  Examples


      REGISTER sip:registrar.biloxi.com SIP/2.0
      Via: SIP/2.0/TCP bobspc.biloxi.com:5060;branch=z9hG4bKnashds7
      Max-Forwards: 70
      To: Bob <sip:bob@biloxi.com>
      From: Bob <sip:bob@biloxi.com>;tag=456248
      Call-ID: 843817637684230@998sdasdh09
      CSeq: 1826 REGISTER
      Contact: <sip:bob@192.0.2.4>
      Expires: 7200
      Content-Length: 19

      grant_type=password&pop=<pop>


      SIP/2.0 200 OK
      Via: SIP/2.0/TCP bobspc.biloxi.com:5060;branch=z9hG4bKnashds7
           ;received=192.0.2.4
      To: Bob <sip:bob@biloxi.com>;tag=2493k59kd
      From: Bob <sip:bob@biloxi.com>;tag=456248
      Call-ID: 843817637684230@998sdasdh09
      CSeq: 1826 REGISTER
      Contact: <sip:bob@192.0.2.4>
      Expires: 7200
      Content-Length: 0

      {
         "access_token":"2YotnFZFEjr1zCsicMWpAA",
         "token_type":"example",
         "expires_in":3600,
         "refresh_token":"tGzv3JOkF0XG5Qx2TlKWIA",
         "example_parameter":"example_value"
      }



5.  Client Credentials Grant

   The following flow assumes that the UA is able to get a token using
   some out-of-band mechanism, and the UA wants to use the token to
   register, subscribe, and get service.

   The flow uses a combination of the following from RFC6749:

   o  Client Credentials Grant defined in section 4.4




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   o  Extensions Grants defined in section 4.5.


   User                            Proxy                   Authorization
   Agent                                                          Server
   ---------------------------------------------------------------------
     |                               |                               |
     | REGISTER username@domain.com, token                           |
     |------------------------------>|                               |
     |                               |                               |
     |                               | POST /authorize               |
     |                               |     [ grant_type = <some-urn] |
     |                               |       token=<some-token> ]    |
     |                               |------------------------------>|
     |                               |                               |
     |                               |        200 OK                 |
     |                               |          [validity, services] |
     |                               |------------------------------>|
     |                               |                               |
     |                        200 OK |                               |
     |<------------------------------|                               |
     |                               |                               |
     |                               |                               |



5.1.  Registration

   The UA is in possession of a token that was obtained through some
   out-of-band mechanism.

   The UA sends a REGISTER request and include the token in the
   Authorization header using the Bearer scheme as defined in RFC6750.

   If the proxy is able to verify the token, the proxy accepts the
   registration request and responds with 200 OK.

5.2.  Authorization

   When the proxy receives the REGISTER request with the token, the
   proxy will try to first validate the token before responding to the
   UA request.

   The proxy sends a POST request and include the following parameters
   in the body of the request:

   grant_type (REQUIRED)




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      Some well-defined URN

   username (REQUIRED)

      The resource owner username.

   access_token (REQUIRED)

      The token received from the UA.

   scope (OPTIONAL)

      The scope of the token.

   If the authorization server is able to validate and authorize the
   request, it will respond with 200 OK with a body that contains the
   following parameters:

      access_token, token_type, expires, refresh_token, scope

6.  Outbound

   RFC5626 defines a mechanism that allows a UA to simultaneously
   connect and establish registration with multiple outbound proxies to
   get service.

   This section describes that impact of outbound on this authorization
   mechanism.

6.1.  Authorization Code Grant type

   During initial registration with the primary proxy, the UA is able to
   get an authorization code that it will use to register with the
   primary proxy.  Assuming the authorization server is shared between
   the various outbound proxies, the UA will be able to use the same
   authorization code to register with the secondary proxies and as a
   result each one of the secondary proxies will get the master-key
   associated with the user to be used for the calculation of the proof-
   of-possession.

6.2.  Resource Owner Password Credentials Grant type

   During registration the proxy challenges the UA, and both the proxy
   and the UA create a master-key based on HA1, realm, and nonce.  Since
   the nonce is not shared between the various proxies, it is not
   possible for the outbound proxies to use the same master-key; as a
   result, the UA is expected to maintain a master-key and token per
   outbound proxy.



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6.3.  Client Credentials Grant type

   Since the tokens are obtained using some out-of-band mechanism, and
   the authorization server is shared between the outbound proxies, the
   UA should be able to register and get service from any one of the
   outbound proxies.

7.  Security Considerations

      <Security considerations text>

8.  IANA Considerations

      <IANA considerations text>

9.  Acknowledgments

      <Acknowledgments text>

10.  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, March 1997.

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, H., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              June 2002.

   [RFC6749]  Hardt, D., "The OAuth 2.0 Authorization Framework", RFC
              6749, October 2012.

Authors' Addresses

   Rifaat Shekh-Yusef (editor)
   Avaya
   250 Sidney Street
   Belleville, Ontario
   Canada

   Phone: +1-613-967-5267
   EMail: rifaat.ietf@gmail.com






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   Victor Pascual
   Quobis
   Spain

   EMail: victor.pascual@quobis.com














































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