



OAuth Working Group                                          B. Campbell
Internet-Draft                                             Ping Identity
Intended status: Standards Track                            C. Mortimore
Expires: May 16, 2015                                         Salesforce
                                                                M. Jones
                                                               Microsoft
                                                       November 12, 2014


 SAML 2.0 Profile for OAuth 2.0 Client Authentication and Authorization
                                 Grants
                    draft-ietf-oauth-saml2-bearer-23

Abstract

   This specification defines the use of a Security Assertion Markup
   Language (SAML) 2.0 Bearer Assertion as a means for requesting an
   OAuth 2.0 access token as well as for use as a means of client
   authentication.

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 May 16, 2015.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   4
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  HTTP Parameter Bindings for Transporting Assertions . . . . .   4
     2.1.  Using SAML Assertions as Authorization Grants . . . . . .   4
     2.2.  Using SAML Assertions for Client Authentication . . . . .   5
   3.  Assertion Format and Processing Requirements  . . . . . . . .   6
     3.1.  Authorization Grant Processing  . . . . . . . . . . . . .   8
     3.2.  Client Authentication Processing  . . . . . . . . . . . .   9
   4.  Authorization Grant Example . . . . . . . . . . . . . . . . .   9
   5.  Interoperability Considerations . . . . . . . . . . . . . . .  11
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   7.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  12
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
     8.1.  Sub-Namespace Registration of urn:ietf:params:oauth
           :grant-type:saml2-bearer  . . . . . . . . . . . . . . . .  12
     8.2.  Sub-Namespace Registration of urn:ietf:params:oauth
           :client-assertion-type:saml2-bearer . . . . . . . . . . .  12
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  14
   Appendix B.  Document History . . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

1.  Introduction

   The Security Assertion Markup Language (SAML) 2.0
   [OASIS.saml-core-2.0-os] is an XML-based framework that allows
   identity and security information to be shared across security
   domains.  The SAML specification, while primarily targeted at
   providing cross domain Web browser single sign-on, was also designed
   to be modular and extensible to facilitate use in other contexts.

   The Assertion, an XML security token, is a fundamental construct of
   SAML that is often adopted for use in other protocols and
   specifications.  (Some examples include [OASIS.WSS-SAMLTokenProfile]
   and [OASIS.WS-Fed].)  An Assertion is generally issued by an identity
   provider and consumed by a service provider who relies on its content
   to identify the Assertion's subject for security related purposes.





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   The OAuth 2.0 Authorization Framework [RFC6749] provides a method for
   making authenticated HTTP requests to a resource using an access
   token.  Access tokens are issued to third-party clients by an
   authorization server (AS) with the (sometimes implicit) approval of
   the resource owner.  In OAuth, an authorization grant is an abstract
   term used to describe intermediate credentials that represent the
   resource owner authorization.  An authorization grant is used by the
   client to obtain an access token.  Several authorization grant types
   are defined to support a wide range of client types and user
   experiences.  OAuth also allows for the definition of new extension
   grant types to support additional clients or to provide a bridge
   between OAuth and other trust frameworks.  Finally, OAuth allows the
   definition of additional authentication mechanisms to be used by
   clients when interacting with the authorization server.

   The Assertion Framework for OAuth 2.0 Client Authentication and
   Authorization Grants [I-D.ietf-oauth-assertions] specification is an
   abstract extension to OAuth 2.0 that provides a general framework for
   the use of Assertions as client credentials and/or authorization
   grants with OAuth 2.0.  This specification profiles the Assertion
   Framework for OAuth 2.0 Client Authentication and Authorization
   Grants [I-D.ietf-oauth-assertions] specification to define an
   extension grant type that uses a SAML 2.0 Bearer Assertion to request
   an OAuth 2.0 access token as well as for use as client credentials.
   The format and processing rules for the SAML Assertion defined in
   this specification are intentionally similar, though not identical,
   to those in the Web Browser SSO Profile defined in the SAML Profiles
   [OASIS.saml-profiles-2.0-os] specification.  This specification is
   reusing, to the extent reasonable, concepts and patterns from that
   well-established Profile.

   This document defines how a SAML Assertion can be used to request an
   access token when a client wishes to utilize an existing trust
   relationship, expressed through the semantics of (and digital
   signature or keyed message digest calculated over) the SAML
   Assertion, without a direct user approval step at the authorization
   server.  It also defines how a SAML Assertion can be used as a client
   authentication mechanism.  The use of an Assertion for client
   authentication is orthogonal to and separable from using an Assertion
   as an authorization grant.  They can be used either in combination or
   separately.  Client assertion authentication is nothing more than an
   alternative way for a client to authenticate to the token endpoint
   and must be used in conjunction with some grant type to form a
   complete and meaningful protocol request.  Assertion authorization
   grants may be used with or without client authentication or
   identification.  Whether or not client authentication is needed in
   conjunction with an assertion authorization grant, as well as the




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   supported types of client authentication, are policy decisions at the
   discretion of the authorization server.

   The process by which the client obtains the SAML Assertion, prior to
   exchanging it with the authorization server or using it for client
   authentication, is out of scope.

1.1.  Notational Conventions

   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].

   Unless otherwise noted, all the protocol parameter names and values
   are case sensitive.

1.2.  Terminology

   All terms are as defined in The OAuth 2.0 Authorization Framework
   [RFC6749], the Assertion Framework for OAuth 2.0 Client
   Authentication and Authorization Grants [I-D.ietf-oauth-assertions],
   and the Security Assertion Markup Language (SAML) 2.0
   [OASIS.saml-core-2.0-os] specifications.

2.  HTTP Parameter Bindings for Transporting Assertions

   The Assertion Framework for OAuth 2.0 Client Authentication and
   Authorization Grants [I-D.ietf-oauth-assertions] specification
   defines generic HTTP parameters for transporting Assertions during
   interactions with a token endpoint.  This section defines specific
   parameters and treatments of those parameters for use with SAML 2.0
   Bearer Assertions.

2.1.  Using SAML Assertions as Authorization Grants

   To use a SAML Bearer Assertion as an authorization grant, the client
   uses an access token request as defined in Section 4 of the Assertion
   Framework for OAuth 2.0 Client Authentication and Authorization
   Grants [I-D.ietf-oauth-assertions] specification with the following
   specific parameter values and encodings.

   The value of the "grant_type" parameter is
   "urn:ietf:params:oauth:grant-type:saml2-bearer".

   The value of the "assertion" parameter contains a single SAML 2.0
   Assertion.  It MUST NOT contain more than one SAML 2.0 assertion.
   The SAML Assertion XML data MUST be encoded using base64url, where
   the encoding adheres to the definition in Section 5 of RFC 4648



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   [RFC4648] and where the padding bits are set to zero.  To avoid the
   need for subsequent encoding steps (by "application/x-www-form-
   urlencoded" [W3C.REC-html401-19991224], for example), the base64url
   encoded data MUST NOT be line wrapped and pad characters ("=") MUST
   NOT be included.

   The "scope" parameter may be used, as defined in the Assertion
   Framework for OAuth 2.0 Client Authentication and Authorization
   Grants [I-D.ietf-oauth-assertions] specification, to indicate the
   requested scope.

   Authentication of the client is optional, as described in
   Section 3.2.1 of OAuth 2.0 [RFC6749] and consequently, the
   "client_id" is only needed when a form of client authentication that
   relies on the parameter is used.

   The following example demonstrates an Access Token Request with an
   assertion as an authorization grant (with extra line breaks for
   display purposes only):

     POST /token.oauth2 HTTP/1.1
     Host: as.example.com
     Content-Type: application/x-www-form-urlencoded

     grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Asaml2-bearer&
     assertion=PHNhbWxwOl...[omitted for brevity]...ZT4

2.2.  Using SAML Assertions for Client Authentication

   To use a SAML Bearer Assertion for client authentication, the client
   uses the following parameter values and encodings.

   The value of the "client_assertion_type" parameter is
   "urn:ietf:params:oauth:client-assertion-type:saml2-bearer".

   The value of the "client_assertion" parameter MUST contain a single
   SAML 2.0 Assertion.  The SAML Assertion XML data MUST be encoded
   using base64url, where the encoding adheres to the definition in
   Section 5 of RFC 4648 [RFC4648] and where the padding bits are set to
   zero.  To avoid the need for subsequent encoding steps (by
   "application/x-www-form-urlencoded" [W3C.REC-html401-19991224], for
   example), the base64url encoded data SHOULD NOT be line wrapped and
   pad characters ("=") SHOULD NOT be included.

   The following example demonstrates a client authenticating using an
   assertion during the presentation of an authorization code grant in
   an Access Token Request (with extra line breaks for display purposes
   only):



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     POST /token.oauth2 HTTP/1.1
     Host: as.example.com
     Content-Type: application/x-www-form-urlencoded

     grant_type=authorization_code&
     code=vAZEIHjQTHuGgaSvyW9hO0RpusLzkvTOww3trZBxZpo&
     client_assertion_type=urn%3Aietf%3Aparams%3Aoauth
     %3Aclient-assertion-type%3Asaml2-bearer&
     client_assertion=PHNhbW...[omitted for brevity]...ZT

3.  Assertion Format and Processing Requirements

   In order to issue an access token response as described in OAuth 2.0
   [RFC6749] or to rely on an Assertion for client authentication, the
   authorization server MUST validate the Assertion according to the
   criteria below.  Application of additional restrictions and policy
   are at the discretion of the authorization server.

   1.   The Assertion's <Issuer> element MUST contain a unique
        identifier for the entity that issued the Assertion.  In the
        absence of an application profile specifying otherwise,
        compliant applications MUST compare Issuer values using the
        Simple String Comparison method defined in Section 6.2.1 of RFC
        3986 [RFC3986].

   2.   The Assertion MUST contain a <Conditions> element with an
        <AudienceRestriction> element with an <Audience> element that
        identifies the authorization server as an intended audience.
        Section 2.5.1.4 of Assertions and Protocols for the OASIS
        Security Assertion Markup Language [OASIS.saml-core-2.0-os]
        defines the <AudienceRestriction> and <Audience> elements and,
        in addition to the URI references discussed there, the token
        endpoint URL of the authorization server MAY be used as a URI
        that identifies the authorization server as an intended
        audience.  The Authorization Server MUST reject any assertion
        that does not contain its own identity as the intended audience.
        In the absence of an application profile specifying otherwise,
        compliant applications MUST compare the audience values using
        the Simple String Comparison method defined in Section 6.2.1 of
        RFC 3986 [RFC3986].  As noted in Section 5, the precise strings
        to be used as the audience for a given Authorization Server must
        be configured out-of-band by the Authorization Server and the
        Issuer of the assertion.

   3.   The Assertion MUST contain a <Subject> element identifying the
        principal that is the subject of the Assertion.  Additional
        information identifying the subject/principal MAY be included in
        an <AttributeStatement>.



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        A.  For the authorization grant, the Subject typically
            identifies an authorized accessor for which the access token
            is being requested (i.e., the resource owner or an
            authorized delegate), but in some cases, may be a
            pseudonymous identifier or other value denoting an anonymous
            user.

        B.  For client authentication, the Subject MUST be the
            "client_id" of the OAuth client.

   4.   The Assertion MUST have an expiry that limits the time window
        during which it can be used.  The expiry can be expressed either
        as the NotOnOrAfter attribute of the <Conditions> element or as
        the NotOnOrAfter attribute of a suitable
        <SubjectConfirmationData> element.

   5.   The <Subject> element MUST contain at least one
        <SubjectConfirmation> element that has a Method attribute with a
        value of "urn:oasis:names:tc:SAML:2.0:cm:bearer".  If the
        Assertion does not have a suitable NonOnOrAfter attribute on the
        <Conditions> element, the <SubjectConfirmation> element MUST
        contain a <SubjectConfirmationData> element.  When present, the
        <SubjectConfirmationData> element MUST have a Recipient
        attribute with a value indicating the token endpoint URL of the
        authorization server (or an acceptable alias).  The
        authorization server MUST verify that the value of the Recipient
        attribute matches the token endpoint URL (or an acceptable
        alias) to which the Assertion was delivered.  The
        <SubjectConfirmationData> element MUST have a NotOnOrAfter
        attribute that limits the window during which the Assertion can
        be confirmed.  The <SubjectConfirmationData> element MAY also
        contain an Address attribute limiting the client address from
        which the Assertion can be delivered.  Verification of the
        Address is at the discretion of the authorization server.

   6.   The authorization server MUST reject the entire Assertion if the
        NotOnOrAfter instant on the <Conditions> element has passed
        (subject to allowable clock skew between systems).  The
        authorization server MUST reject the <SubjectConfirmation> (but
        MAY still use the rest of the Assertion) if the NotOnOrAfter
        instant on the <SubjectConfirmationData> has passed (subject to
        allowable clock skew).  Note that the authorization server may
        reject Assertions with a NotOnOrAfter instant that is
        unreasonably far in the future.  The authorization server MAY
        ensure that Bearer Assertions are not replayed, by maintaining
        the set of used ID values for the length of time for which the
        Assertion would be considered valid based on the applicable
        NotOnOrAfter instant.



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   7.   If the Assertion issuer directly authenticated the subject, the
        Assertion SHOULD contain a single <AuthnStatement> representing
        that authentication event.  If the Assertion was issued with the
        intention that the client act autonomously on behalf of the
        subject, an <AuthnStatement> SHOULD NOT be included and the
        client presenting the assertion SHOULD be identified in the
        <NameID> or similar element in the <SubjectConfirmation>
        element, or by other available means like SAML V2.0 Condition
        for Delegation Restriction [OASIS.saml-deleg-cs].

   8.   Other statements, in particular <AttributeStatement> elements,
        MAY be included in the Assertion.

   9.   The Assertion MUST be digitally signed or have a Message
        Authentication Code applied by the issuer.  The authorization
        server MUST reject assertions with an invalid signature or
        Message Authentication Code.

   10.  Encrypted elements MAY appear in place of their plain text
        counterparts as defined in [OASIS.saml-core-2.0-os].

   11.  The authorization server MUST reject an Assertion that is not
        valid in all other respects per [OASIS.saml-core-2.0-os], such
        as (but not limited to) all content within the Conditions
        element including the NotOnOrAfter and NotBefore attributes,
        unknown condition types, etc.

3.1.  Authorization Grant Processing

   Assertion authorization grants may be used with or without client
   authentication or identification.  Whether or not client
   authentication is needed in conjunction with an assertion
   authorization grant, as well as the supported types of client
   authentication, are policy decisions at the discretion of the
   authorization server.  However, if client credentials are present in
   the request, the authorization server MUST validate them.

   If the Assertion is not valid (including if its subject confirmation
   requirements cannot be met), the authorization server constructs an
   error response as defined in OAuth 2.0 [RFC6749].  The value of the
   "error" parameter MUST be the "invalid_grant" error code.  The
   authorization server MAY include additional information regarding the
   reasons the Assertion was considered invalid using the
   "error_description" or "error_uri" parameters.







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   For example:

     HTTP/1.1 400 Bad Request
     Content-Type: application/json
     Cache-Control: no-store

     {
       "error":"invalid_grant",
       "error_description":"Audience validation failed"
     }

3.2.  Client Authentication Processing

   If the client Assertion is not valid (including if its subject
   confirmation requirements cannot be met), the authorization server
   constructs an error response as defined in OAuth 2.0 [RFC6749].  The
   value of the "error" parameter MUST be the "invalid_client" error
   code.  The authorization server MAY include additional information
   regarding the reasons the Assertion was considered invalid using the
   "error_description" or "error_uri" parameters.

4.  Authorization Grant Example

   The following examples illustrate what a conforming Assertion and an
   access token request would look like.

   The example shows an assertion issued and signed by the SAML Identity
   Provider identified as "https://saml-idp.example.com".  The subject
   of the assertion is identified by email address as
   "brian@example.com", who authenticated to the Identity Provider by
   means of a digital signature where the key was validated as part of
   an X.509 Public Key Infrastructure.  The intended audience of the
   assertion is "https://saml-sp.example.net", which is an identifier
   for a SAML Service Provider with which the authorization server
   identifies itself.  The assertion is sent as part of an access token
   request to the authorization server's token endpoint at
   "https://authz.example.net/token.oauth2".














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   Below is an example SAML 2.0 Assertion (whitespace formatting is for
   display purposes only):

     <Assertion IssueInstant="2010-10-01T20:07:34.619Z"
       ID="ef1xsbZxPV2oqjd7HTLRLIBlBb7"
       Version="2.0"
       xmlns="urn:oasis:names:tc:SAML:2.0:assertion">
      <Issuer>https://saml-idp.example.com</Issuer>
      <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
       [...omitted for brevity...]
      </ds:Signature>
      <Subject>
       <NameID
        Format="urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress">
        brian@example.com
       </NameID>
       <SubjectConfirmation
         Method="urn:oasis:names:tc:SAML:2.0:cm:bearer">
        <SubjectConfirmationData
          NotOnOrAfter="2010-10-01T20:12:34.619Z"
          Recipient="https://authz.example.net/token.oauth2"/>
        </SubjectConfirmation>
       </Subject>
       <Conditions>
         <AudienceRestriction>
           <Audience>https://saml-sp.example.net</Audience>
         </AudienceRestriction>
       </Conditions>
       <AuthnStatement AuthnInstant="2010-10-01T20:07:34.371Z">
         <AuthnContext>
           <AuthnContextClassRef>
             urn:oasis:names:tc:SAML:2.0:ac:classes:X509
           </AuthnContextClassRef>
         </AuthnContext>
       </AuthnStatement>
     </Assertion>

                   Figure 1: Example SAML 2.0 Assertion













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   To present the Assertion shown in the previous example as part of an
   access token request, for example, the client might make the
   following HTTPS request (with extra line breaks for display purposes
   only):

     POST /token.oauth2 HTTP/1.1
     Host: authz.example.net
     Content-Type: application/x-www-form-urlencoded

     grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Asaml2-
     bearer&assertion=PEFzc2VydGlvbiBJc3N1ZUluc3RhbnQ9IjIwMTEtMDU
     [...omitted for brevity...]aG5TdGF0ZW1lbnQ-PC9Bc3NlcnRpb24-

                         Figure 2: Example Request

5.  Interoperability Considerations

   Agreement between system entities regarding identifiers, keys, and
   endpoints is required in order to achieve interoperable deployments
   of this profile.  Specific items that require agreement are as
   follows: values for the issuer and audience identifiers, the location
   of the token endpoint, the key used to apply and verify the digital
   signature over the assertion, one-time use restrictions on
   assertions, maximum assertion lifetime allowed, and the specific
   subject and attribute requirements of the assertion.  The exchange of
   such information is explicitly out of scope for this specification
   and typical deployment of it will be done alongside existing SAML Web
   SSO deployments that have already established a means of exchanging
   such information.  Metadata for the OASIS Security Assertion Markup
   Language (SAML) V2.0 [OASIS.saml-metadata-2.0-os] is one common
   method of exchanging SAML related information about system entities.

   The RSA-SHA256 algorithm, from [RFC6931], is a mandatory to implement
   XML signature algorithm for this profile.

6.  Security Considerations

   The security considerations described within the Assertion Framework
   for OAuth 2.0 Client Authentication and Authorization Grants
   [I-D.ietf-oauth-assertions], The OAuth 2.0 Authorization Framework
   [RFC6749], and the Security and Privacy Considerations for the OASIS
   Security Assertion Markup Language (SAML) V2.0
   [OASIS.saml-sec-consider-2.0-os] specifications are all applicable to
   this document.

   The specification does not mandate replay protection for the SAML
   assertion usage for either the authorization grant or for client




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   authentication.  It is an optional feature, which implementations may
   employ at their own discretion.

7.  Privacy Considerations

   A SAML Assertion may contain privacy-sensitive information and, to
   prevent disclosure of such information to unintended parties, should
   only be transmitted over encrypted channels, such as TLS.  In cases
   where it is desirable to prevent disclosure of certain information to
   the client, the Subject and/or individual attributes of a SAML
   Assertion should be encrypted to the authorization server.

   Deployments should determine the minimum amount of information
   necessary to complete the exchange and include only that information
   in an Assertion (typically by limiting what information is included
   in an <AttributeStatement> or omitting it altogether).  In some
   cases, the Subject can be a value representing an anonymous or
   pseudonymous user, as described in Section 6.3.1 of the Assertion
   Framework for OAuth 2.0 Client Authentication and Authorization
   Grants [I-D.ietf-oauth-assertions].

8.  IANA Considerations

8.1.  Sub-Namespace Registration of urn:ietf:params:oauth:grant-
      type:saml2-bearer

   This is a request to IANA to please register the value "grant-
   type:saml2-bearer" in the registry urn:ietf:params:oauth established
   in An IETF URN Sub-Namespace for OAuth [RFC6755].

   o  URN: urn:ietf:params:oauth:grant-type:saml2-bearer

   o  Common Name: SAML 2.0 Bearer Assertion Grant Type Profile for
      OAuth 2.0

   o  Change controller: IESG

   o  Specification Document: [[this document]]

8.2.  Sub-Namespace Registration of urn:ietf:params:oauth:client-
      assertion-type:saml2-bearer

   This is a request to IANA to please register the value "client-
   assertion-type:saml2-bearer" in the registry urn:ietf:params:oauth
   established in An IETF URN Sub-Namespace for OAuth [RFC6755].

   o  URN: urn:ietf:params:oauth:client-assertion-type:saml2-bearer




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   o  Common Name: SAML 2.0 Bearer Assertion Profile for OAuth 2.0
      Client Authentication

   o  Change controller: IESG

   o  Specification Document: [[this document]]

9.  References

9.1.  Normative References

   [I-D.ietf-oauth-assertions]
              Campbell, B., Mortimore, C., Jones, M., and Y. Goland,
              "Assertion Framework for OAuth 2.0 Client Authentication
              and Authorization Grants", draft-ietf-oauth-assertions
              (work in progress), October 2014.

   [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, <http://docs.oasis-
              open.org/security/saml/v2.0/saml-core-2.0-os.pdf>.

   [OASIS.saml-deleg-cs]
              Cantor, S., Ed., "SAML V2.0 Condition for Delegation
              Restriction", Nov 2009.

   [OASIS.saml-sec-consider-2.0-os]
              Hirsch, F., Philpott, R., and E. Maler, "Security and
              Privacy Considerations for the OASIS Security Markup
              Language (SAML) V2.0", OASIS Standard saml-sec-consider-
              2.0-os, March 2005, <http://docs.oasis-
              open.org/security/saml/v2.0/saml-sec-consider-2.0-os.pdf>.

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

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

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

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




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   [RFC6931]  Eastlake, D., "Additional XML Security Uniform Resource
              Identifiers (URIs)", RFC 6931, April 2013.

9.2.  Informative References

   [OASIS.WS-Fed]
              Goodner, M. and T. Nadalin, "Web Services Federation
              Language (WS-Federation) Version 1.2", May 2009,
              <http://docs.oasis-open.org/wsfed/federation/v1.2/os/
              ws-federation-1.2-spec-os.html>.

   [OASIS.WSS-SAMLTokenProfile]
              Monzillo, R., Kaler, C., Nadalin, T., Hallam-Baker, P.,
              and C. Milono, "Web Services Security SAML Token Profile
              Version 1.1.1", May 2012, <http://docs.oasis-open.org/wss-
              m/wss/v1.1.1/wss-SAMLTokenProfile-v1.1.1.html>.

   [OASIS.saml-metadata-2.0-os]
              Cantor, S., Moreh, J., Philpott, R., and E. Maler,
              "Metadata for the Security Assertion Markup Language
              (SAML) V2.0", OASIS Standard saml-metadata-2.0-os, March
              2005, <http://docs.oasis-open.org/security/saml/v2.0/
              saml-metadata-2.0-os.pdf>.

   [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,
              <http://docs.oasis-open.org/security/saml/v2.0/
              saml-profiles-2.0-os.pdf>.

   [RFC6755]  Campbell, B. and H. Tschofenig, "An IETF URN Sub-Namespace
              for OAuth", RFC 6755, October 2012.

   [W3C.REC-html401-19991224]
              Raggett, D., Hors, A., 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>.

Appendix A.  Acknowledgements

   The following people contributed wording and concepts to this
   document: Paul Madsen, Patrick Harding, Peter Motykowski, Eran
   Hammer, Peter Saint-Andre, Ian Barnett, Eric Fazendin, Torsten
   Lodderstedt, Susan Harper, Scott Tomilson, Scott Cantor, Hannes
   Tschofenig, David Waite, Phil Hunt, and Mukesh Bhatnagar.



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Appendix B.  Document History

   [[ to be removed by RFC editor before publication as an RFC ]]

   draft-ietf-oauth-saml2-bearer-23

   o  Fix typo per http://www.ietf.org/mail-archive/web/oauth/current/
      msg13790.html

   draft-ietf-oauth-saml2-bearer-22

   o  Changes/suggestions from IESG reviews.

   draft-ietf-oauth-saml2-bearer-21

   o  Added Privacy Considerations section per AD review discussion
      http://www.ietf.org/mail-archive/web/oauth/current/msg13148.html
      and http://www.ietf.org/mail-archive/web/oauth/current/
      msg13144.html

   draft-ietf-oauth-saml2-bearer-20

   o  Clarified some text around the treatment of subject based on the
      rough rough consensus from the thread staring at
      http://www.ietf.org/mail-archive/web/oauth/current/msg12630.html

   draft-ietf-oauth-saml2-bearer-19

   o  Updated references.

   draft-ietf-oauth-saml2-bearer-18

   o  Clean up language around subject per http://www.ietf.org/mail-
      archive/web/oauth/current/msg12254.html.

   o  As suggested in http://www.ietf.org/mail-
      archive/web/oauth/current/msg12253.html stated that "In the
      absence of an application profile specifying otherwise, compliant
      applications MUST compare the audience/issuer values using the
      Simple String Comparison method defined in Section 6.2.1 of RFC
      3986."

   o  Clarify the potentially confusing language about the AS confirming
      the assertion http://www.ietf.org/mail-archive/web/oauth/current/
      msg12255.html.






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   o  Combine the two items about AuthnStatement and drop the word
      presenter as discussed in http://www.ietf.org/mail-
      archive/web/oauth/current/msg12257.html.

   o  Added one-time use, maximum lifetime, and specific subject and
      attribute requirements to Interoperability Considerations based on
      http://www.ietf.org/mail-archive/web/oauth/current/msg12252.html.

   o  Reword security considerations and mention that replay protection
      is not mandated based on http://www.ietf.org/mail-
      archive/web/oauth/current/msg12259.html.

   draft-ietf-oauth-saml2-bearer-17

   o  Stated that issuer and audience values SHOULD be compared using
      the Simple String Comparison method defined in Section 6.2.1 of
      RFC 3986 unless otherwise specified by the application.

   draft-ietf-oauth-saml2-bearer-16

   o  Changed title from "SAML 2.0 Bearer Assertion Profiles for OAuth
      2.0" to "SAML 2.0 Profile for OAuth 2.0 Client Authentication and
      Authorization Grants" to be more explicit about the scope of the
      document per http://www.ietf.org/mail-archive/web/oauth/current/
      msg11063.html.

   o  Fixed typo in text identifying the presenter from "or similar
      element, the" to "or similar element in the".

   o  Numbered the list of processing rules.

   o  Smallish editorial cleanups to try and improve readability and
      comprehensibility.

   o  Cleaner split out of the processing rules in cases where they
      differ for client authentication and authorization grants.

   o  Clarified the parameters that are used/available for authorization
      grants.

   o  Added Interoperability Considerations section and info reference
      to SAML Metadata.

   o  Added more explanatory context to the example in Section 4.

   draft-ietf-oauth-saml2-bearer-15

   o  Reference RFC 6749 and RFC 6755.



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   o  Update draft-ietf-oauth-assertions reference to -06.

   o  Remove extraneous word per http://www.ietf.org/mail-
      archive/web/oauth/current/msg10055.html

   draft-ietf-oauth-saml2-bearer-14

   o  Add more text to intro explaining that an assertion grant type can
      be used with or without client authentication/identification and
      that client assertion authentication is nothing more than an
      alternative way for a client to authenticate to the token endpoint

   o  Add examples to Sections 2.1 and 2.2

   o  Update references

   draft-ietf-oauth-saml2-bearer-13

   o  Update references: oauth-assertions-04, oauth-urn-sub-ns-05, oauth
      -28

   o  Changed "Description" to "Specification Document" in both
      registration requests in IANA Considerations per changes to the
      template in ietf-oauth-urn-sub-ns(-03)

   o  Added "(or an acceptable alias)" so that it's in both sentences
      about Recipient and the token endpoint URL so there's no ambiguity

   o  Update area and workgroup (now Security and OAuth was Internet and
      nothing)

   draft-ietf-oauth-saml2-bearer-12

   o  updated reference to draft-ietf-oauth-v2 from -25 to -26 and
      draft-ietf-oauth-assertions from -02 to -03

   draft-ietf-oauth-saml2-bearer-11

   o  Removed text about limited lifetime access tokens and the SHOULD
      NOT on issuing refresh tokens.  The text was moved to draft-ietf-
      oauth-assertions-02 and somewhat modified per http://www.ietf.org/
      mail-archive/web/oauth/current/msg08298.html.

   o  Fixed typo/missing word per http://www.ietf.org/mail-
      archive/web/oauth/current/msg08733.html.

   o  Added Terminology section.




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   draft-ietf-oauth-saml2-bearer-10

   o  fix a spelling mistake

   draft-ietf-oauth-saml2-bearer-09

   o  Attempt to address an ambiguity around validation requirements
      when the Conditions element contain a NotOnOrAfter and
      SubjectConfirmation/SubjectConfirmationData does too.  Basically
      it needs to have at least one bearer SubjectConfirmation element
      but that element can omit SubjectConfirmationData, if Conditions
      has an expiry on it.  Otherwise, a valid SubjectConfirmation must
      have a SubjectConfirmationData with Recipient and NotOnOrAfter.
      And any SubjectConfirmationData that has those elements needs to
      have them checked.

   o  clarified that AudienceRestriction is under Conditions (even
      though it's implied by schema)

   o  fix a typo

   draft-ietf-oauth-saml2-bearer-08

   o  fix some typos

   draft-ietf-oauth-saml2-bearer-07

   o  update reference from draft-campbell-oauth-urn-sub-ns to draft-
      ietf-oauth-urn-sub-ns

   o  Updated to reference draft-ietf-oauth-v2-20

   draft-ietf-oauth-saml2-bearer-06

   o  Fix three typos NamseID->NameID and (2x) Namspace->Namespace

   draft-ietf-oauth-saml2-bearer-05

   o  Allow for subject confirmation data to be optional when Conditions
      contain audience and NotOnOrAfter

   o  Rework most of the spec to profile draft-ietf-oauth-assertions for
      both authn and authz including (but not limited to):

      *  remove requirement for issuer to be
         urn:oasis:names:tc:SAML:2.0:nameid-format:entity

      *  change wording on Subject requirements



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   o  using a MAY, explicitly say that the Audience can be token
      endpoint URL of the authorization server

   o  Change title to be more generic (allowing for client authn too)

   o  added client authentication to the abstract

   o  register and use urn:ietf:params:oauth:grant-type:saml2-bearer for
      grant type rather than http://oauth.net/grant_type/saml/2.0/bearer

   o  register urn:ietf:params:oauth:client-assertion-type:saml2-bearer

   o  remove scope parameter as it is defined in
      http://tools.ietf.org/html/draft-ietf-oauth-assertions

   o  remove assertion param registration because it [should] be in
      http://tools.ietf.org/html/draft-ietf-oauth-assertions

   o  fix typo(s) and update/add references

   draft-ietf-oauth-saml2-bearer-04

   o  Changed the grant_type URI from
      "http://oauth.net/grant_type/assertion/saml/2.0/bearer" to
      "http://oauth.net/grant_type/saml/2.0/bearer" - dropping the word
      assertion from the path.  Recent versions of draft-ietf-oauth-v2
      no longer refer to extension grants using the word assertion so
      this URI is more reflective of that.  It also more closely aligns
      with the grant type URI in draft-jones-oauth-jwt-bearer-00 which
      is "http://oauth.net/grant_type/jwt/1.0/bearer".

   o  Added "case sensitive" to scope definition to align with draft-
      ietf-oauth-v2-15/16.

   o  Updated to reference draft-ietf-oauth-v2-16

   draft-ietf-oauth-saml2-bearer-03

   o  Cleanup of some editorial issues.

   draft-ietf-oauth-saml2-bearer-02

   o  Added scope parameter with text copied from draft-ietf-oauth-v2-12
      (the reorg of draft-ietf-oauth-v2-12 made it so scope wasn't
      really inherited by this spec anymore)






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   o  Change definition of the assertion parameter to be more generally
      applicable per the suggestion near the end of http://www.ietf.org/
      mail-archive/web/oauth/current/msg05253.html

   o  Editorial changes based on feedback

   draft-ietf-oauth-saml2-bearer-01

   o  Update spec name when referencing draft-ietf-oauth-v2 (The OAuth
      2.0 Protocol Framework -> The OAuth 2.0 Authorization Protocol)

   o  Update wording in Introduction to talk about extension grant types
      rather than the assertion grant type which is a term no longer
      used in OAuth 2.0

   o  Updated to reference draft-ietf-oauth-v2-12 and denote as work in
      progress

   o  Update Parameter Registration Request to use similar terms as
      draft-ietf-oauth-v2-12 and remove Related information part

   o  Add some text giving discretion to AS on rejecting assertions with
      unreasonably long validity window.

   draft-ietf-oauth-saml2-bearer-00

   o  Added Parameter Registration Request for "assertion" to IANA
      Considerations.

   o  Changed document name to draft-ietf-oauth-saml2-bearer in
      anticipation of becoming an OAUTH WG item.

   o  Attempt to move the entire definition of the 'assertion' parameter
      into this draft (it will no longer be defined in OAuth 2 Protocol
      Framework).

   draft-campbell-oauth-saml-01

   o  Updated to reference draft-ietf-oauth-v2-11 and reflect changes
      from -10 to -11.

   o  Updated examples.

   o  Relaxed processing rules to allow for more than one
      SubjectConfirmation element.

   o  Removed the 'MUST NOT contain a NotBefore attribute' on
      SubjectConfirmationData.



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   o  Relaxed wording that ties the subject of the Assertion to the
      resource owner.

   o  Added some wording about identifying the client when the subject
      hasn't directly authenticated including an informative reference
      to SAML V2.0 Condition for Delegation Restriction.

   o  Added a few examples to the language about verifying that the
      Assertion is valid in all other respects.

   o  Added some wording to the introduction about the similarities to
      Web SSO in the format and processing rules

   o  Changed the grant_type (was assertion_type) URI from
      http://oauth.net/assertion_type/saml/2.0/bearer to
      http://oauth.net/grant_type/assertion/saml/2.0/bearer

   o  Changed title to include "Grant Type" in it.

   o  Editorial updates based on feedback from the WG and others
      (including capitalization of Assertion when referring to SAML).

   draft-campbell-oauth-saml-00

   o  Initial I-D

Authors' Addresses

   Brian Campbell
   Ping Identity

   Email: brian.d.campbell@gmail.com


   Chuck Mortimore
   Salesforce.com

   Email: cmortimore@salesforce.com


   Michael B. Jones
   Microsoft

   Email: mbj@microsoft.com
   URI:   http://self-issued.info/






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