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Versions: 00 01 02 03 04 05 06 07 08 09 RFC 6595

Network Working Group                                        K. Wierenga
Internet-Draft                                       Cisco Systems, Inc.
Intended status: Standards Track                                 E. Lear
Expires: August 23, 2012                              Cisco Systems GmbH
                                                            S. Josefsson
                                                                  SJD AB
                                                       February 20, 2012


                 A SASL and GSS-API Mechanism for SAML
                   draft-ietf-kitten-sasl-saml-09.txt

Abstract

   Security Assertion Markup Language (SAML) has found its usage on the
   Internet for Web Single Sign-On.  Simple Authentication and Security
   Layer (SASL) and the Generic Security Service Application Program
   Interface (GSS-API) are application frameworks to generalize
   authentication.  This memo specifies a SASL mechanism and a GSS-API
   mechanism for SAML 2.0 that allows the integration of existing SAML
   Identity Providers with applications using SASL and GSS-API.

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 http://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 August 23, 2012.

Copyright Notice

   Copyright (c) 2012 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



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   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.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Applicability  . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Authentication flow  . . . . . . . . . . . . . . . . . . . . .  6
   3.  SAML SASL Mechanism Specification  . . . . . . . . . . . . . .  9
     3.1.  Initial Response . . . . . . . . . . . . . . . . . . . . .  9
     3.2.  Authentication Request . . . . . . . . . . . . . . . . . . 10
     3.3.  Outcome and parameters . . . . . . . . . . . . . . . . . . 11
   4.  SAML GSS-API Mechanism Specification . . . . . . . . . . . . . 12
     4.1.  GSS-API Principal Name Types for SAML  . . . . . . . . . . 13
   5.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     5.1.  XMPP . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     5.2.  IMAP . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 22
     6.1.  Man in the middle and Tunneling Attacks  . . . . . . . . . 22
     6.2.  Binding SAML subject identifiers to Authorization
           Identities . . . . . . . . . . . . . . . . . . . . . . . . 22
     6.3.  User Privacy . . . . . . . . . . . . . . . . . . . . . . . 22
     6.4.  Collusion between RPs  . . . . . . . . . . . . . . . . . . 22
     6.5.  GSS-API specific security considerations . . . . . . . . . 22
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 24
     7.1.  IANA mech-profile  . . . . . . . . . . . . . . . . . . . . 24
     7.2.  IANA OID . . . . . . . . . . . . . . . . . . . . . . . . . 24
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 25
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 26
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 28
   Appendix B.  Changes . . . . . . . . . . . . . . . . . . . . . . . 29
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30













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1.  Introduction

   Security Assertion Markup Language (SAML) 2.0
   [OASIS.saml-core-2.0-os] is a set of specifications that provide
   various means for a user to be identified to a relying party (RP)
   through the exchange of (typically signed) assertions issued by an
   identity provider (IdP).  It includes a number of protocols, protocol
   bindings [OASIS.saml-bindings-2.0-os], and interoperability profiles
   [OASIS.saml-profiles-2.0-os] designed for different use cases.

   Simple Authentication and Security Layer (SASL) [RFC4422] is a
   generalized mechanism for identifying and authenticating a user and
   for optionally negotiating a security layer for subsequent protocol
   interactions.  SASL is used by application protocols like IMAP
   [RFC3501], POP [RFC1939] and XMPP [RFC6120].  The effect is to make
   modular authentication, so that newer authentication mechanisms can
   be added as needed.  This memo specifies just such a mechanism.

   The Generic Security Service Application Program Interface (GSS-API)
   [RFC2743] provides a framework for applications to support multiple
   authentication mechanisms through a unified programming interface.
   This document defines a pure SASL mechanism for SAML, but it conforms
   to the new bridge between SASL and the GSS-API called GS2 [RFC5801].
   This means that this document defines both a SASL mechanism and a
   GSS-API mechanism.  The GSS-API interface is OPTIONAL for SASL
   implementers, and the GSS-API considerations can be avoided in
   environments that use SASL directly without GSS-API.

   As currently envisioned, this mechanism enables interworking between
   SASL and SAML in order to assert the identity of the user and other
   attributes to relying parties.  As such, while servers (as relying
   parties) will advertise SASL mechanisms (including SAML), clients
   will select the SAML SASL mechanism as their SASL mechanism of
   choice.

   The SAML mechanism described in this memo aims to re-use the Web
   Browser SSO profile defined in section 4.1 of the  SAML profiles 2.0
   specification [OASIS.saml-profiles-2.0-os] to the maximum extent and
   therefore does not establish a separate authentication, integrity and
   confidentiality mechanism.  The mechanism assumes a security layer,
   such as Transport Layer Security (TLS [RFC5246]), will continue to be
   used.  This specification is appropriate for use when a browser
   instance is available.  In the absence of a browser instance, SAML
   profiles that don't require a browser such as the Enhanced Client or
   Proxy profile (as defined in section 4.2 of the  SAML profiles 2.0
   specification [OASIS.saml-profiles-2.0-os] may be used, but that is
   outside the scope of this specification.




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   Figure 1 describes the interworking between SAML and SASL: this
   document requires enhancements to the Relying Party (the SASL server)
   and to the Client, as the two SASL communication end points, but no
   changes to the SAML Identity Provider are necessary.  To accomplish
   this goal some indirect messaging is tunneled within SASL, and some
   use of external methods is made.




                                       +-----------+
                                       |           |
                                      >|  Relying  |
                                     / |  Party    |
                                   //  |           |
                                 //    +-----------+
                      SAML/    //            ^
                      HTTPS  //           +--|--+
                           //             | S|  |
                          /             S | A|  |
                        //              A | M|  |
                      //                S | L|  |
                    //                  L |  |  |
                  //                      |  |  |
                </                        +--|--+
         +------------+                      v
         |            |                 +----------+
         |  SAML      |     HTTPS       |          |
         |  Identity  |<--------------->|  Client  |
         |  Provider  |                 |          |
         +------------+                 +----------+


                    Figure 1: Interworking Architecture

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 RFC 2119 [RFC2119].

   The reader is assumed to be familiar with the terms used in the SAML
   2.0 specification [OASIS.saml-core-2.0-os].

1.2.  Applicability

   Because this mechanism transports information that should not be
   controlled by an attacker, the SAML mechanism MUST only be used over



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   channels protected by TLS, or over similar integrity protected and
   authenticated channels.  In addition, when TLS is used the client
   MUST successfully validate the server certificate ([RFC5280],
   [RFC6125])

   Note: An Intranet does not constitute such an integrity protected and
   authenticated channel!












































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2.  Authentication flow

   While SAML itself is merely a markup language, its common use case
   these days is with HTTP [RFC2616] or HTTPS [RFC2818] and HTML
   [W3C.REC-html401-19991224].  What follows is a typical flow:

   1.  The browser requests a resource of a Relying Party (RP) (via an
       HTTP request).

   2.  The Relying Party redirects the browser via an HTTP redirect (as
       described in Section 10.3 of [RFC2616]) to the Identity Provider
       (IdP) or an IdP discovery service.  When it does so, it includes
       the following parameters: (1) an authentication request that
       contains the name of resource being requested, (2) a browser
       cookie, and (3) a return URL as specified in Section 3.1 of the
       SAML profiles 2.0 specification [OASIS.saml-profiles-2.0-os].

   3.  The user authenticates to the IdP and perhaps authorizes the
       release of user attributes to the Relying Party.

   4.  In its authentication response, the IdP redirects (via an HTTP
       redirect) the browser back to the RP with an authentication
       assertion (stating that the IdP vouches that the subject has
       successfully authenticated), optionally along with some
       additional attributes.

   5.  The Relying Party now has sufficient identity information to
       approve access to the resource or not, and acts accordingly.  The
       authentication is concluded.

   When considering this flow in the context of SASL, we note that while
   the Relying Party and the client both must change their code to
   implement this SASL mechanism, the IdP can remain untouched.  The
   Relying Party already has some sort of session (probably a TCP
   connection) established with the client.  However, it may be
   necessary to redirect a SASL client to another application or
   handler.  The steps are as follows:

   1.  The SASL server (Relying Party) advertises support for the SASL
       SAML20 mechanism to the client

   2.  The client initiates a SASL authentication with SAML20 and sends
       a domain name that allows the SASL server to determine the
       appropriate IdP

   3.  The SASL server transmits an authentication request encoded using
       a Uniform Resource Identifier (URI) as described in RFC 3986
       [RFC3986] and an HTTP redirect to the IdP corresponding to the



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       domain

   4.  The SASL client now sends an empty response, as authentication
       continues via the normal SAML flow and the SASL server will
       receive the answer to the challenge out-of-band from the SASL
       conversation.

   5.  At this point the SASL client MUST construct a URL containing the
       content received in the previous message from the SASL server.
       This URL is transmitted to the IdP either by the SASL client
       application or an appropriate handler, such as a browser.

   6.  Next the user authenticates to the IdP.  The manner in which the
       end user is authenticated to the IdP and any policies surrounding
       such authentication is out of scope for SAML and hence for this
       draft.  This step happens out of band from SASL.

   7.  The IdP will convey information about the success or failure of
       the authentication back to the the SASL server (Relying Party) in
       the form of an Authentication Statement or failure, using a
       indirect response via the client browser or the handler (and with
       an external browser client control should be passed back to the
       SASL client).  This step happens out of band from SASL.

   8.  The SASL Server sends an appropriate SASL response to the client,
       along with an optional list of attributes

   Please note: What is described here is the case in which the client
   has not previously authenticated.  It is possible that the client
   already holds a valid SAML authentication token so that the user does
   not need to be involved in the process anymore, but that would still
   be external to SASL.  This is classic Web Single Sign-On, in which
   the Web Browser client presents the authentication token (cookie) to
   the RP without renewed user authentication at the IdP.

   With all of this in mind, the flow appears as follows in Figure 2:















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            SASL Serv.       Client          IdP
               |>-----(1)----->|              | Advertisement
               |               |              |
               |<-----(2)-----<|              | Initiation
               |               |              |
               |>-----(3)----->|              | Authentication Request
               |               |              |
               |<-----(4)-----<|              | Empty Response
               |               |              |
               |               |< - -(5,6) - ->| Client<>IDP
               |               |              | Authentication
               |               |              |
               |<- - - - - - - - - - -(7)- - -| Authentication Statement
               |               |              |
               |>-----(8)----->|              | SASL completion with
               |               |              | status
               |               |              |

          ----- = SASL
          - - - = HTTP or HTTPS (external to SASL)




                       Figure 2: Authentication flow


























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3.  SAML SASL Mechanism Specification

   This section specifies the details of the SAML SASL mechanism.  See
   section 5 of [RFC4422] for what is described here.

   The name of this mechanism is "SAML20".  The mechanism is capable of
   transferring an authorization identity (via the "gs2-header").  The
   mechanism does not offer a security layer.

   The mechanism is client-first.  The first mechanism message from the
   client to the server is the "initial-response".  As described in
   [RFC4422], if the application protocol does not support sending a
   client-response together with the authentication request, the server
   will send an empty server-challenge to let the client begin.  The
   second mechanism message is from the server to the client, containing
   the SAML "authentication-request".  The third mechanism message is
   from client to the server, and is the fixed message consisting of "="
   (i.e., an empty response).  The fourth mechanism message is from the
   server to the client, indicating the SASL mechanism outcome.

3.1.  Initial Response

   A client initiates a "SAML20" authentication with SASL by sending the
   GS2 header followed by the authentication identifier (message 2 in
   Figure 2) and is defined as follows:


        initial-response = gs2-header Idp-Identifier
        IdP-Identifier = domain ; domain name with corresponding IdP


   The "gs2-header" is used as follows:

      - The "gs2-nonstd-flag" MUST NOT be present.

      - The "gs2-cb-flag" MUST be set to "n" because channel binding
      [RFC5056] data cannot be integrity protected by the SAML
      negotiation.  (Note: In theory channel binding data could be
      inserted in the SAML flow by the client and verified by the
      server, but that is currently not supported in SAML.)

      - The "gs2-authzid" carries the optional authorization identity as
      specified in [RFC5801] (not to be confused with the IdP-
      Identifier).

   Domain name is specified in [RFC1035].  A domain name is either a
   "traditional domain name" as described in [RFC1035] or an
   "internationalized domain name" as described in [RFC5890].  Clients



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   and servers MUST treat the IdP-Identifier as a domain name slot
   [RFC5890].  They also SHOULD support internationalized domain names
   (IDNs) in the Idp-Identifier field; if they do so, all of the domain
   name's labels MUST be A-labels or NR-LDH labels [RFC5890], if
   necessary internationalized labels MUST be converted from U-labels to
   A-labels by using the Punycode encoding [RFC3492] for A-labels prior
   to sending them to the SASL-server as described in the protocol
   specification for Internationalized Domain Names in Applications
   [RFC5891].

3.2.  Authentication Request

   The SASL Server transmits to the SASL client a URI that redirects the
   SAML client to the IdP (corresponding to the domain that the user
   provided), with a SAML authentication request as one of the
   parameters (message 3 in Figure 2) in the following way:


        authentication-request = URI


   URI is specified in [RFC3986] and is encoded according to Section 3.4
   (HTTP Redirect) of the SAML bindings 2.0 specification
   [OASIS.saml-bindings-2.0-os].  The SAML authentication request is
   encoded according to Section 3.4 (Authentication Request) of the SAML
   core 2.0 specification [OASIS.saml-core-2.0-os].  Should the client
   support Internationalized Resource Identifiers (IRIs) [RFC3987] it
   MUST first convert the IRI to a URI before transmitting it to the
   server [RFC5890].

   Note: The SASL server may have a static mapping of domain to
   corresponding IdP or alternatively a DNS-lookup mechanism could be
   envisioned, but that is out-of-scope for this document.

   Note: While the SASL client MAY sanity check the URI it received,
   ultimately it is the SAML IdP that will be validated by the SAML
   client which is out-of-scope for this document.

   The client then sends the authentication request via an HTTP GET
   (sent over a server-authenticated TLS channel) to the IdP, as if
   redirected to do so from an HTTP server and in accordance with the
   Web Browser SSO profile, as described in section 3.1 of SAML profiles
   2.0 specification [OASIS.saml-profiles-2.0-os] (message 5 and 6 in
   Figure 2).

   The client handles both user authentication to the IdP and
   confirmation or rejection of the authentiation of the RP (out-of-
   scope for this document).



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   After all authentication has been completed by the IdP, the IdP will
   send a redirect message to the client in the form of a URI
   corresponding to the Relying Party as specified in the authentication
   request ("AssertionConsumerServiceURL") and with the SAML response as
   one of the parameters (message 7 in Figure 2).

   Please note: this means that the SASL server needs to implement a
   SAML Relying Party.  Also, the SASL server needs to correlate the
   session it has with the SASL client with the appropriate SAML
   authentication result.  It can do so by comparing the ID of the SAML
   authentication request it has issued with the one it receives in the
   SAML authentication statement.

3.3.  Outcome and parameters

   The SASL server (in its capacity as a SAML Relying Party) now
   validates the SAML authentication response it received from the SAML
   client via HTTP or HTTPS.

   The outcome of that validation by the SASL server constitutes a SASL
   mechanism outcome, and therefore (as stated in [RFC4422]) SHALL be
   used to set state in the server accordingly, and it SHALL be used by
   the server to report that state to the SASL client as described in
   [RFC4422] Section 3.6 (message 8 in Figure 2).



























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4.  SAML GSS-API Mechanism Specification

   This section and its sub-sections are not required for SASL
   implementors, but this section MUST be observed to implement the GSS-
   API mechanism discussed below.

   This section specify a GSS-API mechanism that when used via the GS2
   bridge to SASL behaves like the SASL mechanism defined in this
   document.  Thus, it can loosely be said that the SAML SASL mechanism
   is also a GSS-API mechanism.  The SAML user takes the role of the
   GSS-API Initiator and the SAML Relying Party takes the role of the
   GSS-API Acceptor.  The SAML Identity Provider does not have a role in
   GSS-API, and is considered an internal matter for the SAML mechanism.
   The messages are the same, but

   a) the GS2 header on the client's first message and channel binding
   data is excluded when SAML is used as a GSS-API mechanism, and

   b) the RFC2743 section 3.1 initial context token header is prefixed
   to the client's first authentication message (context token).

   The GSS-API mechanism OID for SAML is OID-TBD (IANA to assign: see
   IANA considerations).

   SAML20 security contexts MUST have the mutual_state flag
   (GSS_C_MUTUAL_FLAG) set to TRUE.  SAML does not support credential
   delegation, therefore SAML security contexts MUST have the
   deleg_state flag (GSS_C_DELEG_FLAG) set to FALSE.

   The mutual authentication property of this mechanism relies on
   successfully comparing the TLS server identity with the negotiated
   target name.  Since the TLS channel is managed by the application
   outside of the GSS-API mechanism, the mechanism itself is unable to
   confirm the name while the application is able to perform this
   comparison for the mechanism.  For this reason, applications MUST
   match the TLS server identity with the target name, as discussed in
   [RFC6125].  More precisely, to pass identity validation the client
   uses the securely negotiated targ_name as the reference identifier
   and match it to the DNS-ID of the server certificate, and MUST reject
   the connection if there is a mismatch.  For compatibility with
   deployed certificate hierarchies, the client MAY also perform a
   comparison with the CN-ID when there is no DNS-ID present.  Wildcard
   matching is permitted.  The targ_name reference identifier is a
   "traditional domain names" thus the comparison is made using case-
   insensitive ASCII comparison.

   The SAML mechanism does not support per-message tokens or
   GSS_Pseudo_random.



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4.1.  GSS-API Principal Name Types for SAML

   SAML supports standard generic name syntaxes for acceptors such as
   GSS_C_NT_HOSTBASED_SERVICE (see [RFC2743], Section 4.1).  SAML
   supports only a single name type for initiators: GSS_C_NT_USER_NAME.
   GSS_C_NT_USER_NAME is the default name type for SAML.  The query,
   display, and exported name syntaxes for SAML principal names are all
   the same.  There are no SAML-specific name syntaxes -- applications
   should use generic GSS-API name types such as GSS_C_NT_USER_NAME and
   GSS_C_NT_HOSTBASED_SERVICE (see [RFC2743], Section 4).  The exported
   name token does, of course, conforms to [RFC2743], Section 3.2.








































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5.  Examples

5.1.  XMPP

   Suppose the user has an identity at the SAML IdP saml.example.org and
   a Jabber Identifier (JID) "somenode@example.com", and wishes to
   authenticate his XMPP connection to xmpp.example.com.  The
   authentication on the wire would then look something like the
   following:

   Step 1: Client initiates stream to server:


   <stream:stream xmlns='jabber:client'
   xmlns:stream='http://etherx.jabber.org/streams'
   to='example.com' version='1.0'>


   Step 2: Server responds with a stream tag sent to client:


   <stream:stream
   xmlns='jabber:client' xmlns:stream='http://etherx.jabber.org/streams'
   id='some_id' from='example.com' version='1.0'>


   Step 3: Server informs client of available authentication mechanisms:


   <stream:features>
    <mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
     <mechanism>DIGEST-MD5</mechanism>
     <mechanism>PLAIN</mechanism>
     <mechanism>SAML20</mechanism>
    </mechanisms>
   </stream:features>


   Step 4: Client selects an authentication mechanism and provides the
   initial client response containing the according to the definition in
   Section 4 ofBASE64 [RFC4648] encoded gs2-header and domain:


   <auth xmlns='urn:ietf:params:xml:ns:xmpp-sasl' mechanism='SAML20'>
   biwsZXhhbXBsZS5vcmc</auth>


   The decoded string is: n,,example.org



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   Step 5: Server sends a BASE64 encoded challenge to client in the form
   of an HTTP Redirect to the SAML IdP corresponding to example.org
   (https://saml.example.org) with the SAML Authentication Request as
   specified in the redirection url:


   aHR0cHM6Ly9zYW1sLmV4YW1wbGUub3JnL1NBTUwvQnJvd3Nlcj9TQU1MUmVx
   dWVzdD1QSE5oYld4d09rRjFkR2h1VW1WeGRXVnpkQ0I0Yld4dWN6cHpZVzFz
   Y0QwaWRYSnVPbTloYzJsek9tNWhiV1Z6T25Sak9sTkJUVXc2TWk0d09uQnli
   M1J2WTI5c0lnMEtJQ0FnSUVsRVBTSmZZbVZqTkRJMFptRTFNVEF6TkRJNE9U
   QTVZVE13Wm1ZeFpUTXhNVFk0TXpJM1pqYzVORGMwT1RnMElpQldaWEp6YVc5
   dVBTSXlMakFpRFFvZ0lDQWdTWE56ZFdWSmJuTjBZVzUwUFNJeU1EQTNMVEV5
   TFRFd1ZERXhPak01T2pNMFdpSWdSbTl5WTJWQmRYUm9iajBpWm1Gc2MyVWlE
   UW9nSUNBZ1NYTlFZWE56YVhabFBTSm1ZV3h6WlNJTkNpQWdJQ0JRY205MGIy
   TnZiRUpwYm1ScGJtYzlJblZ5YmpwdllYTnBjenB1WVcxbGN6cDBZenBUUVUx
   TU9qSXVNRHBpYVc1a2FXNW5jenBJVkZSUUxWQlBVMVFpRFFvZ0lDQWdRWE56
   WlhKMGFXOXVRMjl1YzNWdFpYSlRaWEoyYVdObFZWSk1QUTBLSUNBZ0lDQWdJ
   Q0FpYUhSMGNITTZMeTk0YlhCd0xtVjRZVzF3YkdVdVkyOXRMMU5CVFV3dlFY
   TnpaWEowYVc5dVEyOXVjM1Z0WlhKVFpYSjJhV05sSWo0TkNpQThjMkZ0YkRw
   SmMzTjFaWElnZUcxc2JuTTZjMkZ0YkQwaWRYSnVPbTloYzJsek9tNWhiV1Z6
   T25Sak9sTkJUVXc2TWk0d09tRnpjMlZ5ZEdsdmJpSStEUW9nSUNBZ0lHaDBk
   SEJ6T2k4dmVHMXdjQzVsZUdGdGNHeGxMbU52YlEwS0lEd3ZjMkZ0YkRwSmMz
   TjFaWEkrRFFvZ1BITmhiV3h3T2s1aGJXVkpSRkJ2YkdsamVTQjRiV3h1Y3pw
   ellXMXNjRDBpZFhKdU9tOWhjMmx6T201aGJXVnpPblJqT2xOQlRVdzZNaTR3
   T25CeWIzUnZZMjlzSWcwS0lDQWdJQ0JHYjNKdFlYUTlJblZ5YmpwdllYTnBj
   enB1WVcxbGN6cDBZenBUUVUxTU9qSXVNRHB1WVcxbGFXUXRabTl5YldGME9u
   Qmxjbk5wYzNSbGJuUWlEUW9nSUNBZ0lGTlFUbUZ0WlZGMVlXeHBabWxsY2ow
   aWVHMXdjQzVsZUdGdGNHeGxMbU52YlNJZ1FXeHNiM2REY21WaGRHVTlJblJ5
   ZFdVaUlDOCtEUW9nUEhOaGJXeHdPbEpsY1hWbGMzUmxaRUYxZEdodVEyOXVk
   R1Y0ZEEwS0lDQWdJQ0I0Yld4dWN6cHpZVzFzY0QwaWRYSnVPbTloYzJsek9t
   NWhiV1Z6T25Sak9sTkJUVXc2TWk0d09uQnliM1J2WTI5c0lpQU5DaUFnSUNB
   Z0lDQWdRMjl0Y0dGeWFYTnZiajBpWlhoaFkzUWlQZzBLSUNBOGMyRnRiRHBC
   ZFhSb2JrTnZiblJsZUhSRGJHRnpjMUpsWmcwS0lDQWdJQ0FnZUcxc2JuTTZj
   MkZ0YkQwaWRYSnVPbTloYzJsek9tNWhiV1Z6T25Sak9sTkJUVXc2TWk0d09t
   RnpjMlZ5ZEdsdmJpSStEUW9nb0NBZ0lDQjFjbTQ2YjJGemFYTTZibUZ0WlhN
   NmRHTTZVMEZOVERveUxqQTZZV002WTJ4aGMzTmxjenBRWVhOemQyOXlaRkJ5
   YjNSbFkzUmxaRlJ5WVc1emNHOXlkQTBLSUNBOEwzTmhiV3c2UVhWMGFHNURi
   MjUwWlhoMFEyeGhjM05TWldZK0RRb2dQQzl6WVcxc2NEcFNaWEYxWlhOMFpX
   UkJkWFJvYmtOdmJuUmxlSFErSUEwS1BDOXpZVzFzY0RwQmRYUm9ibEpsY1hW
   bGMzUSs=


   The decoded challenge is:








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   https://saml.example.org/SAML/Browser?SAMLRequest=PHNhbWxwOk
   F1dGhuUmVxdWVzdCB4bWxuczpzYW1scD0idXJuOm9hc2lzOm5hbWVzOnRjOl
   NBTUw6Mi4wOnByb3RvY29sIg0KICAgIElEPSJfYmVjNDI0ZmE1MTAzNDI4OT
   A5YTMwZmYxZTMxMTY4MzI3Zjc5NDc0OTg0IiBWZXJzaW9uPSIyLjAiDQogIC
   AgSXNzdWVJbnN0YW50PSIyMDA3LTEyLTEwVDExOjM5OjM0WiIgRm9yY2VBdX
   Robj0iZmFsc2UiDQogICAgSXNQYXNzaXZlPSJmYWxzZSINCiAgICBQcm90b2
   NvbEJpbmRpbmc9InVybjpvYXNpczpuYW1lczp0YzpTQU1MOjIuMDpiaW5kaW
   5nczpIVFRQLVBPU1QiDQogICAgQXNzZXJ0aW9uQ29uc3VtZXJTZXJ2aWNlVV
   JMPQ0KICAgICAgICAiaHR0cHM6Ly94bXBwLmV4YW1wbGUuY29tL1NBTUwvQX
   NzZXJ0aW9uQ29uc3VtZXJTZXJ2aWNlIj4NCiA8c2FtbDpJc3N1ZXIgeG1sbn
   M6c2FtbD0idXJuOm9hc2lzOm5hbWVzOnRjOlNBTUw6Mi4wOmFzc2VydGlvbi
   I+DQogICAgIGh0dHBzOi8veG1wcC5leGFtcGxlLmNvbQ0KIDwvc2FtbDpJc3
   N1ZXI+DQogPHNhbWxwOk5hbWVJRFBvbGljeSB4bWxuczpzYW1scD0idXJuOm
   9hc2lzOm5hbWVzOnRjOlNBTUw6Mi4wOnByb3RvY29sIg0KICAgICBGb3JtYX
   Q9InVybjpvYXNpczpuYW1lczp0YzpTQU1MOjIuMDpuYW1laWQtZm9ybWF0On
   BlcnNpc3RlbnQiDQogICAgIFNQTmFtZVF1YWxpZmllcj0ieG1wcC5leGFtcG
   xlLmNvbSIgQWxsb3dDcmVhdGU9InRydWUiIC8+DQogPHNhbWxwOlJlcXVlc3
   RlZEF1dGhuQ29udGV4dA0KICAgICB4bWxuczpzYW1scD0idXJuOm9hc2lzOm
   5hbWVzOnRjOlNBTUw6Mi4wOnByb3RvY29sIiANCiAgICAgICAgQ29tcGFyaX
   Nvbj0iZXhhY3QiPg0KICA8c2FtbDpBdXRobkNvbnRleHRDbGFzc1JlZg0KIC
   AgICAgeG1sbnM6c2FtbD0idXJuOm9hc2lzOm5hbWVzOnRjOlNBTUw6Mi4wOm
   Fzc2VydGlvbiI+DQogICAgICAgICAgIHVybjpvYXNpczpuYW1lczp0YzpTQU
   1MOjIuMDphYzpjbGFzc2VzOlBhc3N3b3JkUHJvdGVjdGVkVHJhbnNwb3J0DQ
   ogIDwvc2FtbDpBdXRobkNvbnRleHRDbGFzc1JlZj4NCiA8L3NhbWxwOlJlcX
   Vlc3RlZEF1dGhuQ29udGV4dD4gDQo8L3NhbWxwOkF1dGhuUmVxdWVzdD4=


   Where the decoded SAMLRequest looks like:























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 <samlp:AuthnRequest xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"
     ID="_bec424fa5103428909a30ff1e31168327f79474984" Version="2.0"
     IssueInstant="2007-12-10T11:39:34Z" ForceAuthn="false"
     IsPassive="false"
     ProtocolBinding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
     AssertionConsumerServiceURL=
         "https://xmpp.example.com/SAML/AssertionConsumerService">
  <saml:Issuer xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">
      https://xmpp.example.com
  </saml:Issuer>
  <samlp:NameIDPolicy xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"
      Format="urn:oasis:names:tc:SAML:2.0:nameid-format:persistent"
      SPNameQualifier="xmpp.example.com" AllowCreate="true" />
  <samlp:RequestedAuthnContext
      xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"
         Comparison="exact">
   <saml:AuthnContextClassRef
       xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">
       urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport
   </saml:AuthnContextClassRef>
  </samlp:RequestedAuthnContext>
 </samlp:AuthnRequest>


   Note: the server can use the request ID
   (_bec424fa5103428909a30ff1e31168327f79474984) to correlate the SASL
   session with the SAML authentication.

   Step 5 (alternative): Server returns error to client if no SAML
   Authentication Request can be constructed:


   <failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
    <temporary-auth-failure/>
   </failure>
   </stream:stream>


   Step 6: Client sends the empty response to the challenge encoded as a
   single =:


   <response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
    =
   </response>


   The following steps between brackets are out of scope for this



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   document but included to better illustrate the entire flow.

   [The client now sends the URL to a browser instance for processing.
   The browser engages in a normal SAML authentication flow (external to
   SASL), like redirection to the Identity Provider
   (https://saml.example.org), the user logs into
   https://saml.example.org, and agrees to authenticate to
   xmpp.example.com.  A redirect is passed back to the client browser
   who sends the AuthN response to the server, containing the subject-
   identifier as an attribute.  If the AuthN response doesn't contain
   the JID, the server maps the subject-identifier received from the IdP
   to a JID]

   Step 7: Server informs client of successful authentication:


   <success xmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>


   Step 7 (alt): Server informs client of failed authentication:


   <failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
    <not-authorized/>
   </failure>
   </stream:stream>


   Please note: line breaks were added to the base64 for clarity.

5.2.  IMAP

   The following describes an IMAP exchange.  Lines beginning with 'S:'
   indicate data sent by the server, and lines starting with 'C:'
   indicate data sent by the client.  Long lines are wrapped for
   readability.















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   S: * OK IMAP4rev1
   C: . CAPABILITY
   S: * CAPABILITY IMAP4rev1 STARTTLS
   S: . OK CAPABILITY Completed
   C: . STARTTLS
   S: . OK Begin TLS negotiation now
   C: . CAPABILITY
   S: * CAPABILITY IMAP4rev1 AUTH=SAML20
   S: . OK CAPABILITY Completed
   C: . AUTHENTICATE SAML20
   S: +
   C: biwsZXhhbXBsZS5vcmc
   S: + aHR0cHM6Ly9zYW1sLmV4YW1wbGUub3JnL1NBTUwvQnJvd3Nlcj9TQU1M
   UmVxdWVzdD1QSE5oYld4d09rRg0KMWRHaHVVbVZ4ZFdWemRDQjRiV3h1Y3pwe
   llXMXNjRDBpZFhKdU9tOWhjMmx6T201aGJXVnpPblJqT2xOQg0KVFV3Nk1pNH
   dPbkJ5YjNSdlkyOXNJZzBLSUNBZ0lFbEVQU0pmWW1Wak5ESTBabUUxTVRBek5
   ESTRPVEE1WQ0KVE13Wm1ZeFpUTXhNVFk0TXpJM1pqYzVORGMwT1RnMElpQlda
   WEp6YVc5dVBTSXlMakFpRFFvZ0lDQWdTWA0KTnpkV1ZKYm5OMFlXNTBQU0l5T
   URBM0xURXlMVEV3VkRFeE9qTTVPak0wV2lJZ1JtOXlZMlZCZFhSb2JqMA0KaV
   ptRnNjMlVpRFFvZ0lDQWdTWE5RWVhOemFYWmxQU0ptWVd4elpTSU5DaUFnSUN
   CUWNtOTBiMk52YkVKcA0KYm1ScGJtYzlJblZ5YmpwdllYTnBjenB1WVcxbGN6
   cDBZenBUUVUxTU9qSXVNRHBpYVc1a2FXNW5jenBJVg0KRlJRTFZCUFUxUWlEU
   W9nSUNBZ1FYTnpaWEowYVc5dVEyOXVjM1Z0WlhKVFpYSjJhV05sVlZKTVBRME
   tJQw0KQWdJQ0FnSUNBaWFIUjBjSE02THk5dFlXbHNMbVY0WVcxd2JHVXVZMjl
   0TDFOQlRVd3ZRWE56WlhKMGFXOQ0KdVEyOXVjM1Z0WlhKVFpYSjJhV05sSWo0
   TkNpQThjMkZ0YkRwSmMzTjFaWElnZUcxc2JuTTZjMkZ0YkQwaQ0KZFhKdU9tO
   WhjMmx6T201aGJXVnpPblJqT2xOQlRVdzZNaTR3T21GemMyVnlkR2x2YmlJK0
   RRb2dJQ0FnSQ0KR2gwZEhCek9pOHZlRzF3Y0M1bGVHRnRjR3hsTG1OdmJRMEt
   JRHd2YzJGdGJEcEpjM04xWlhJK0RRb2dQSA0KTmhiV3h3T2s1aGJXVkpSRkJ2
   YkdsamVTQjRiV3h1Y3pwellXMXNjRDBpZFhKdU9tOWhjMmx6T201aGJXVg0Ke
   k9uUmpPbE5CVFV3Nk1pNHdPbkJ5YjNSdlkyOXNJZzBLSUNBZ0lDQkdiM0p0WV
   hROUluVnlianB2WVhOcA0KY3pwdVlXMWxjenAwWXpwVFFVMU1Pakl1TURwdVl
   XMWxhV1F0Wm05eWJXRjBPbkJsY25OcGMzUmxiblFpRA0KUW9nSUNBZ0lGTlFU
   bUZ0WlZGMVlXeHBabWxsY2owaWVHMXdjQzVsZUdGdGNHeGxMbU52YlNJZ1FXe
   HNiMw0KZERjbVZoZEdVOUluUnlkV1VpSUM4K0RRb2dQSE5oYld4d09sSmxjWF
   ZsYzNSbFpFRjFkR2h1UTI5dWRHVg0KNGRBMEtJQ0FnSUNCNGJXeHVjenB6WVc
   xc2NEMGlkWEp1T205aGMybHpPbTVoYldWek9uUmpPbE5CVFV3Ng0KTWk0d09u
   QnliM1J2WTI5c0lpQU5DaUFnSUNBZ0lDQWdRMjl0Y0dGeWFYTnZiajBpWlhoa
   FkzUWlQZzBLSQ0KQ0E4YzJGdGJEcEJkWFJvYmtOdmJuUmxlSFJEYkdGemMxSm
   xaZzBLSUNBZ0lDQWdlRzFzYm5NNmMyRnRiRA0KMGlkWEp1T205aGMybHpPbTV
   oYldWek9uUmpPbE5CVFV3Nk1pNHdPbUZ6YzJWeWRHbHZiaUkrRFFvZ0lDQQ0K
   Z0lDQjFjbTQ2YjJGemFYTTZibUZ0WlhNNmRHTTZVMEZOVERveUxqQTZZV002W
   TJ4aGMzTmxjenBRWVhOeg0KZDI5eVpGQnliM1JsWTNSbFpGUnlZVzV6Y0c5eW
   RBMEtJQ0E4TDNOaGJXdzZRWFYwYUc1RGIyNTBaWGgwUQ0KMnhoYzNOU1pXWSt
   EUW9nUEM5ellXMXNjRHBTWlhGMVpYTjBaV1JCZFhSb2JrTnZiblJsZUhRK0lB
   MEtQQw0KOXpZVzFzY0RwQmRYUm9ibEpsY1hWbGMzUSs=
   C:
   S: . OK Success (tls protection)



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   The decoded challenge is:


   https://saml.example.org/SAML/Browser?SAMLRequest=PHNhbWxwOkF
   1dGhuUmVxdWVzdCB4bWxuczpzYW1scD0idXJuOm9hc2lzOm5hbWVzOnRjOlNB
   TUw6Mi4wOnByb3RvY29sIg0KICAgIElEPSJfYmVjNDI0ZmE1MTAzNDI4OTA5Y
   TMwZmYxZTMxMTY4MzI3Zjc5NDc0OTg0IiBWZXJzaW9uPSIyLjAiDQogICAgSX
   NzdWVJbnN0YW50PSIyMDA3LTEyLTEwVDExOjM5OjM0WiIgRm9yY2VBdXRobj0
   iZmFsc2UiDQogICAgSXNQYXNzaXZlPSJmYWxzZSINCiAgICBQcm90b2NvbEJp
   bmRpbmc9InVybjpvYXNpczpuYW1lczp0YzpTQU1MOjIuMDpiaW5kaW5nczpIV
   FRQLVBPU1QiDQogICAgQXNzZXJ0aW9uQ29uc3VtZXJTZXJ2aWNlVVJMPQ0KIC
   AgICAgICAiaHR0cHM6Ly9tYWlsLmV4YW1wbGUuY29tL1NBTUwvQXNzZXJ0aW9
   uQ29uc3VtZXJTZXJ2aWNlIj4NCiA8c2FtbDpJc3N1ZXIgeG1sbnM6c2FtbD0i
   dXJuOm9hc2lzOm5hbWVzOnRjOlNBTUw6Mi4wOmFzc2VydGlvbiI+DQogICAgI
   Gh0dHBzOi8veG1wcC5leGFtcGxlLmNvbQ0KIDwvc2FtbDpJc3N1ZXI+DQogPH
   NhbWxwOk5hbWVJRFBvbGljeSB4bWxuczpzYW1scD0idXJuOm9hc2lzOm5hbWV
   zOnRjOlNBTUw6Mi4wOnByb3RvY29sIg0KICAgICBGb3JtYXQ9InVybjpvYXNp
   czpuYW1lczp0YzpTQU1MOjIuMDpuYW1laWQtZm9ybWF0OnBlcnNpc3RlbnQiD
   QogICAgIFNQTmFtZVF1YWxpZmllcj0ieG1wcC5leGFtcGxlLmNvbSIgQWxsb3
   dDcmVhdGU9InRydWUiIC8+DQogPHNhbWxwOlJlcXVlc3RlZEF1dGhuQ29udGV
   4dA0KICAgICB4bWxuczpzYW1scD0idXJuOm9hc2lzOm5hbWVzOnRjOlNBTUw6
   Mi4wOnByb3RvY29sIiANCiAgICAgICAgQ29tcGFyaXNvbj0iZXhhY3QiPg0KI
   CA8c2FtbDpBdXRobkNvbnRleHRDbGFzc1JlZg0KICAgICAgeG1sbnM6c2FtbD
   0idXJuOm9hc2lzOm5hbWVzOnRjOlNBTUw6Mi4wOmFzc2VydGlvbiI+DQogICA
   gICB1cm46b2FzaXM6bmFtZXM6dGM6U0FNTDoyLjA6YWM6Y2xhc3NlczpQYXNz
   d29yZFByb3RlY3RlZFRyYW5zcG9ydA0KICA8L3NhbWw6QXV0aG5Db250ZXh0Q
   2xhc3NSZWY+DQogPC9zYW1scDpSZXF1ZXN0ZWRBdXRobkNvbnRleHQ+IA0KPC
   9zYW1scDpBdXRoblJlcXVlc3Q+


   Where the decoded SAMLRequest looks like:




















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 <samlp:AuthnRequest xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"
     ID="_bec424fa5103428909a30ff1e31168327f79474984" Version="2.0"
     IssueInstant="2007-12-10T11:39:34Z" ForceAuthn="false"
     IsPassive="false"
     ProtocolBinding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
     AssertionConsumerServiceURL=
         "https://mail.example.com/SAML/AssertionConsumerService">
  <saml:Issuer xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">
      https://xmpp.example.com
  </saml:Issuer>
  <samlp:NameIDPolicy xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"
      Format="urn:oasis:names:tc:SAML:2.0:nameid-format:persistent"
      SPNameQualifier="xmpp.example.com" AllowCreate="true" />
  <samlp:RequestedAuthnContext
      xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"
         Comparison="exact">
   <saml:AuthnContextClassRef
       xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion">
       urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport
   </saml:AuthnContextClassRef>
  </samlp:RequestedAuthnContext>
 </samlp:AuthnRequest>





























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6.  Security Considerations

   This section addresses only security considerations associated with
   the use of SAML with SASL applications.  For considerations relating
   to SAML in general, the reader is referred to the SAML specification
   and to other literature.  Similarly, for general SASL Security
   Considerations, the reader is referred to that specification.

6.1.  Man in the middle and Tunneling Attacks

   This mechanism is vulnerable to man-in-the-middle and tunneling
   attacks unless a client always verifies the server identity before
   proceeding with authentication (see [RFC6125]).  Typically TLS is
   used to provide a secure channel with server authentication.

6.2.  Binding SAML subject identifiers to Authorization Identities

   As specified in [RFC4422], the server is responsible for binding
   credentials to a specific authorization identity.  It is therefore
   necessary that only specific trusted IdPs be allowed.  This is
   typical part of SAML trust establishment between Relying Parties and
   IdP.

6.3.  User Privacy

   The IdP is aware of each Relying Party that a user logs into.  There
   is nothing in the protocol to hide this information from the IdP.  It
   is not a requirement to track the visits, but there is nothing that
   prohibits the collection of information.  SASL server implementers
   should be aware that SAML IdPs will be able to track - to some extent
   - user access to their services.

6.4.  Collusion between RPs

   It is possible for Relying Parties to link data that they have
   collected on the users.  By using the same identifier to log into
   every Relying Party, collusion between Relying Parties is possible.
   In SAML, targeted identity was introduced.  Targeted identity allows
   the IdP to transform the identifier the user typed in to a Relying
   Party specific opaque identifier.  This way the Relying Party would
   never see the actual user identifier, but a randomly generated
   identifier.

6.5.  GSS-API specific security considerations

   Security issues inherent in GSS-API (RFC 2743) and GS2 (RFC 5801)
   apply to the SAML GSS-API mechanism defined in this document.
   Further, and as discussed in section 4, proper TLS server identity



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   verification is critical to the security of the mechanism.


















































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7.  IANA Considerations

7.1.  IANA mech-profile

   The IANA is requested to register the following SASL profile:

   SASL mechanism profile: SAML20

   Security Considerations: See this document

   Published Specification: See this document

   For further information: Contact the authors of this document.

   Owner/Change controller: the IETF

   Intended usage: COMMON

   Note: None

7.2.  IANA OID

   The IANA is further requested to assign a new entry for this GSS
   mechanism in the sub-registry for SMI Security for Mechanism Codes,
   whose prefix is iso.org.dod.internet.security.mechanisms
   (1.3.6.1.5.5) and to reference this specification in the registry.

























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8.  References

8.1.  Normative References

   [OASIS.saml-bindings-2.0-os]
              Cantor, S., Hirsch, F., Kemp, J., Philpott, R., and E.
              Maler, "Bindings for the OASIS Security Assertion Markup
              Language (SAML) V2.0", OASIS
              Standard saml-bindings-2.0-os, March 2005.

   [OASIS.saml-core-2.0-os]
              Cantor, S., Kemp, J., Philpott, R., and E. Maler,
              "Assertions and Protocol for the OASIS Security Assertion
              Markup Language (SAML) V2.0", OASIS Standard saml-core-
              2.0-os, March 2005.

   [OASIS.saml-profiles-2.0-os]
              Hughes, J., Cantor, S., Hodges, J., Hirsch, F., Mishra,
              P., Philpott, R., and E. Maler, "Profiles for the OASIS
              Security Assertion Markup Language (SAML) V2.0", OASIS
              Standard OASIS.saml-profiles-2.0-os, March 2005.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC2743]  Linn, J., "Generic Security Service Application Program
              Interface Version 2, Update 1", RFC 2743, January 2000.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

   [RFC3492]  Costello, A., "Punycode: A Bootstring encoding of Unicode
              for Internationalized Domain Names in Applications
              (IDNA)", RFC 3492, March 2003.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC3987]  Duerst, M. and M. Suignard, "Internationalized Resource
              Identifiers (IRIs)", RFC 3987, January 2005.




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   [RFC4422]  Melnikov, A. and K. Zeilenga, "Simple Authentication and
              Security Layer (SASL)", RFC 4422, June 2006.

   [RFC5056]  Williams, N., "On the Use of Channel Bindings to Secure
              Channels", RFC 5056, November 2007.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [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.

   [RFC5801]  Josefsson, S. and N. Williams, "Using Generic Security
              Service Application Program Interface (GSS-API) Mechanisms
              in Simple Authentication and Security Layer (SASL): The
              GS2 Mechanism Family", RFC 5801, July 2010.

   [RFC5890]  Klensin, J., "Internationalized Domain Names for
              Applications (IDNA): Definitions and Document Framework",
              RFC 5890, August 2010.

   [RFC5891]  Klensin, J., "Internationalized Domain Names in
              Applications (IDNA): Protocol", RFC 5891, August 2010.

   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and
              Verification of Domain-Based Application Service Identity
              within Internet Public Key Infrastructure Using X.509
              (PKIX) Certificates in the Context of Transport Layer
              Security (TLS)", RFC 6125, March 2011.

   [W3C.REC-html401-19991224]
              Hors, A., Raggett, D., and I. Jacobs, "HTML 4.01
              Specification", World Wide Web Consortium
              Recommendation REC-html401-19991224, December 1999,
              <http://www.w3.org/TR/1999/REC-html401-19991224>.

8.2.  Informative References

   [RFC1939]  Myers, J. and M. Rose, "Post Office Protocol - Version 3",
              STD 53, RFC 1939, May 1996.

   [RFC3501]  Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
              4rev1", RFC 3501, March 2003.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, October 2006.



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   [RFC6120]  Saint-Andre, P., "Extensible Messaging and Presence
              Protocol (XMPP): Core", RFC 6120, March 2011.

















































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Appendix A.  Acknowledgments

   The authors would like to thank Scott Cantor, Joe Hildebrand, Josh
   Howlett, Leif Johansson, Thomas Lenggenhager, Diego Lopez, Hank
   Mauldin, RL 'Bob' Morgan, Stefan Plug and Hannes Tschofenig for their
   review and contributions.













































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Appendix B.  Changes

   This section to be removed prior to publication.

   o  09 Fixed text per IESG review

   o  08 Fixed text per Gen-Art review

   o  07 Fixed text per comments Alexey Melnikov

   o  06 Fixed text per AD comments

   o  05 Fixed references per ID-nits

   o  04 Added request for IANA assignment, few text clarifications

   o  03 Number of cosmetic changes, fixes per comments Alexey Melnikov

   o  02 Changed IdP URI to domain per Joe Hildebrand, fixed some typos

   o  00 WG -00 draft.  Updates GSS-API section, some fixes per Scott
      Cantor

   o  01 Added authorization identity, added GSS-API specifics, added
      client supplied IdP

   o  00 Initial Revision.
























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Authors' Addresses

   Klaas Wierenga
   Cisco Systems, Inc.
   Haarlerbergweg 13-19
   Amsterdam, Noord-Holland  1101 CH
   Netherlands

   Phone: +31 20 357 1752
   Email: klaas@cisco.com


   Eliot Lear
   Cisco Systems GmbH
   Richtistrasse 7
   Wallisellen, ZH  CH-8304
   Switzerland

   Phone: +41 44 878 9200
   Email: lear@cisco.com


   Simon Josefsson
   SJD AB
   Hagagatan 24
   Stockholm  113 47
   SE

   Email: simon@josefsson.org
   URI:   http://josefsson.org/





















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