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KITTEN                                                          W. Mills
Internet-Draft                                               Yahoo! Inc.
Intended status: Standards Track                            T. Showalter
Expires: December 1, 2012
                                                           H. Tschofenig
                                                  Nokia Siemens Networks
                                                            May 30, 2012


                 A SASL and GSS-API Mechanism for OAuth
                    draft-ietf-kitten-sasl-oauth-01

Abstract

   OAuth enables a third-party application to obtain limited access to a
   protected resource, either on behalf of a resource owner by
   orchestrating an approval interaction, or by allowing the third-party
   application to obtain access on its own behalf.

   This document defines how an application client uses OAuth over the
   Simple Authentication and Security Layer (SASL) or the Generic
   Security Service Application Program Interface (GSS-API) to access a
   protected resource at a resource serve.  Thereby, it enables schemes
   defined within the OAuth framework for non-HTTP-based application
   protocols.

   Clients typically store the user's long term credential.  This does,
   however, lead to significant security vulnerabilities, for example,
   when such a credential leaks.  A significant benefit of OAuth for
   usage in those clients is that the password is replaced by a token.
   Tokens typically provided limited access rights and can be managed
   and revoked separately from the user's long-term credential
   (password).

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."



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   This Internet-Draft will expire on December 1, 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
   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.



































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  7
   3.  OAuth SASL Mechanism Specification . . . . . . . . . . . . . .  8
     3.1.  Initial Client Response  . . . . . . . . . . . . . . . . .  8
       3.1.1.  Reserved Key/Values in OAUTH . . . . . . . . . . . . .  8
     3.2.  Server's Response  . . . . . . . . . . . . . . . . . . . .  9
       3.2.1.  Mapping to SASL Identities . . . . . . . . . . . . . .  9
       3.2.2.  Server response to failed authentication.  . . . . . . 10
     3.3.  Use of Signature Type Authorization  . . . . . . . . . . . 10
     3.4.  Channel Binding  . . . . . . . . . . . . . . . . . . . . . 11
   4.  GSS-API OAuth Mechanism Specification  . . . . . . . . . . . . 12
   5.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     5.1.  Successful Bearer Token Exchange . . . . . . . . . . . . . 13
     5.2.  MAC Authentication with Channel Binding  . . . . . . . . . 13
     5.3.  Failed Exchange  . . . . . . . . . . . . . . . . . . . . . 14
     5.4.  Failed Channel Binding . . . . . . . . . . . . . . . . . . 15
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
     7.1.  SASL Registration  . . . . . . . . . . . . . . . . . . . . 17
     7.2.  GSS-API Registration . . . . . . . . . . . . . . . . . . . 17
   8.  Appendix A -- Document History . . . . . . . . . . . . . . . . 18
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 19
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 20
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
























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1.  Introduction

   OAuth [I-D.ietf-oauth-v2] enables a third-party application to obtain
   limited access to a protected resource, either on behalf of a
   resource owner by orchestrating an approval interaction, or by
   allowing the third-party application to obtain access on its own
   behalf.  The core OAuth specification [I-D.ietf-oauth-v2] does not
   define the interaction between the client and the resource server
   with the access to a protected resource using an Access Token.  This
   functionality is described in two separate specifications, namely
   [I-D.ietf-oauth-v2-bearer], and [I-D.ietf-oauth-v2-http-mac], whereby
   the focus is on an HTTP-based environment only.

   Figure 1 shows the abstract message flow as shown in Figure 1 of
   [I-D.ietf-oauth-v2].


        +--------+                               +---------------+
        |        |--(A)- Authorization Request ->|   Resource    |
        |        |                               |     Owner     |
        |        |<-(B)-- Authorization Grant ---|               |
        |        |                               +---------------+
        |        |
        |        |                               +---------------+
        |        |--(C)-- Authorization Grant -->| Authorization |
        | Client |                               |     Server    |
        |        |<-(D)----- Access Token -------|               |
        |        |                               +---------------+
        |        |
        |        |                               +---------------+
        |        |--(E)----- Access Token ------>|    Resource   |
        |        |                               |     Server    |
        |        |<-(F)--- Protected Resource ---|               |
        +--------+                               +---------------+

                Figure 1: Abstract OAuth 2.0 Protocol Flow

   This document takes advantage of the OAuth protocol and its
   deployment base to provide a way to use SASL [RFC4422] as well as the
   GSS-API [RFC2743] to gain access to resources when using non-HTTP-
   based protocols, such as the Internet Message Access Protocol (IMAP)
   [RFC3501], which is what this memo uses in the examples.

   The Simple Authentication and Security Layer (SASL) is a framework
   for providing authentication and data security services in
   connection-oriented protocols via replaceable mechanisms.  It
   provides a structured interface between protocols and mechanisms.
   The resulting framework allows new protocols to reuse existing



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   mechanisms and allows old protocols to make use of new mechanisms.
   The framework also provides a protocol for securing subsequent
   protocol exchanges within a data security layer.

   The Generic Security Service Application Program Interface (GSS-API)
   [RFC2743] provides a framework for applications to support multiple
   authentication mechanisms through a unified interface.

   This document defines a SASL mechanism for OAuth, 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.  Implementers may be interested in either the
   SASL, the GSS-API, or even both mechanisms.  To faciliate these two
   variants, the description has been split into two parts, one part
   that provides normative references for those interested in the SASL
   OAuth mechanism (see Section 3), and a second part for those
   implementers that wish to implement the GSS-API portion (see
   Section 4).

   When OAuth is integrated into SASL and the GSS-API the high-level
   steps are as follows:

      (A) The client requests authorization from the resource owner.
      The authorization request can be made directly to the resource
      owner (as shown), or preferably indirectly via the authorization
      server as an intermediary.

      (B) The client receives an authorization grant which is a
      credential representing the resource owner's authorization,
      expressed using one of four grant types defined in this
      specification or using an extension grant type.  The authorization
      grant type depends on the method used by the client to request
      authorization and the types supported by the authorization server.

      (C) The client requests an access token by authenticating with the
      authorization server and presenting the authorization grant.

      (D) The authorization server authenticates the client and
      validates the authorization grant, and if valid issues an access
      token.

      (E) The client requests the protected resource from the resource
      server and authenticates by presenting the access token.

      (F) The resource server validates the access token, and if valid,
      serves the request.

   Steps (E) and (F) are not defined in [I-D.ietf-oauth-v2] and are the



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   main functionality specified within this document.  Consequently, the
   message exchange shown in Figure 2 is the result of this
   specification.  The client will genrally need to determine the
   authentication endpoints (and perhaps the service endpoints) before
   the OAuth 2.0 protocol exchange messages in steps (A)-(D) are
   executed.  The discovery of the resource owner and authorization
   server endpoints is outside the scope of this specification.  The
   client must discover those endpoints using a discovery mechanisms
   such as Webfinger using host-meta [I-D.jones-appsawg-webfinger].  In
   band discovery is not tenable if clients support the OAuth 2.0
   password grant.  Once credentials are obtained the client proceeds to
   steps (E) and (F) defined in this specification.


                                                              ----+
   +--------+                                  +---------------+  |
   |        |--(A)-- Authorization Request --->|   Resource    |  |
   |        |                                  |     Owner     |  |Plain
   |        |<-(B)------ Access Grant ---------|               |  |OAuth
   |        |                                  +---------------+  |2.0
   |        |                                                     |
   |        |         Client Credentials &     +---------------+  |
   |        |--(C)------ Access Grant -------->| Authorization |  |
   | Client |                                  |     Server    |  |
   |        |<-(D)------ Access Token ---------|               |  |
   |        |      (w/ Optional Refresh Token) +---------------+  |
   |        |                                                 ----+
   |        |                                                 ----+
   |        |                                  +---------------+  |
   |        |                                  |               |  |OAuth
   |        |--(E)------ Access Token -------->|    Resource   |  |over
   |        |                                  |     Server    |  |SASL/
   |        |<-(F)---- Protected Resource -----|               |  |GSS-
   |        |                                  |               |  |API
   +--------+                                  +---------------+  |
                                                              ----+

                     Figure 2: OAuth SASL Architecture

   It is worthwhile to note that this specification is also compatible
   with OAuth 1.0a [RFC5849].










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2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   The reader is assumed to be familiar with the terms used in the OAuth
   2.0 specification [I-D.ietf-oauth-v2].

   In examples, "C:" and "S:" indicate lines sent by the client and
   server respectively.  Line breaks have been inserted for readability.

   Note that the IMAP SASL specification requires base64 encoding
   message, not this memo.





































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3.  OAuth SASL Mechanism Specification

   SASL is used as a generalized authentication method in a variety of
   application layer protocols.  This document defines two SASL
   mechanisms for usage with OAuth: "OAUTH" and "OAUTH-PLUS".  The
   "OAUTH" SASL mechanism enables OAuth authorizattion schemes for SASL,
   "OAUTH-PLUS" adds channel binding [RFC5056] capability for additional
   security guarantees.

3.1.  Initial Client Response

   Client responses are a key/value pair sequence.  These key/value
   pairs carry the equivalent values form an HTTP context in order to be
   able to complete an OAuth style HTTP authorization.  The ABNF
   [RFC2234] syntax is:



     kvsep          = %x01
     key            = 1*ALPHA
     value          = *(VCHAR | SP | HTAB | CR | LF )
     kvpair         = key "=" value kvsep
     client_resp    = 1*kvpair kvsep

   The following key/value pairs are defined in the client response:



      auth (REQUIRED):  The payload of the HTTP Authorization header for
         an equivalent HTTP OAuth authroization.

      host:  Contains the host name to which the client connected.

      port:  Contains the port number represented as a decimal positive
         integer string without leading zeros to which the client
         connected.

   In authorization schemes that use signatures, the client MUST send
   host and port number key/values, and the server MUST fail
   authorization request requiring signatures that do not have host and
   port values.

3.1.1.  Reserved Key/Values in OAUTH

   In the OAUTH mechanism values for path, query string and post body
   are assigned default values.  OAuth authorization schemes MAY define
   usage of these in the SASL context and extend this specification.
   For OAuth schemes that use request signatures the default values MUST



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   be used unless explict values are provided in the client response.
   The following key values are reserved for future use:



      path (RESERVED):  HTTP path data, the default value is "/".

      qs (RESERVED):  HTTP query string, the default value is "".

      post (RESERVED):  HTTP post data, the default value is "".

3.2.  Server's Response

   The server validates the response per the specification for the
   authorization scheme used.  If the authorization scheme used includes
   signing of the request parameters the client must provide a client
   response that satisfies the data requirements for the scheme in use.

   In the OAUTH-PLUS mechanism the server examines the channel binding
   data, extracts the channel binding unique prefix, and extracts the
   raw channel biding data based on the channel binding type used.  It
   then computes it's own copy of the channel binding payload and
   compares that to the payload sent by the client in the cbdata key/
   value.  Those two must be equal for channel binding to succeed.

   The server responds to a successfully verified client message by
   completing the SASL negotiation.  The authentication scheme MUST
   carry the user ID to be used as the authorization identity (identity
   to act as).  The server MUST use the ID obtained from the credential
   as the user being authorized.

3.2.1.  Mapping to SASL Identities

   Some OAuth mechanisms can provide both an authorization identity and
   an authentication identity.  An example of this is OAuth 1.0a
   [RFC5849] where the consumer key (oauth_consumer_key) identifies the
   entity using to token which equates to the SASL authentication
   identity, and is authenticated using the shared secret.  The
   authorization identity in the OAuth 1.0a case is carried in the token
   (per the requirement above), which SHOULD validated independently.
   The server MAY use a consumer key, a value derived from it, or other
   comparable identity in the OAuth authorization scheme as the SASL
   authentication identity.  If an appropriate authentication identity
   is not available the server MUST use the authorization identity as
   the wuthentication identity.






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3.2.2.  Server response to failed authentication.

   For a failed authentication the server returns a JSON [RFC4627]
   formatted error result, and fails the authentication.  The error
   result consists of the following values:



      status (REQUIRED):  The authorization error code.  Valid error
         codes are defined in the IANA [[need registry name]] registry
         specified in the OAuth 2 core specification.

      scope (OPTIONAL):  The OAuth scope required to access the service.

   If the resource server provides a scope the client SHOULD always
   request scoped tokens from the token endpoint.  The client MAY use a
   scope other than the one provided by the resource server.  Scopes
   other than those advertised by the resource server are be defined by
   the resource owner and provided in service documentation or discovery
   information (which is beyond the scope of this memo).  If not present
   then the client SHOULD presume an empty scope (unscoped token) is
   needed.

   If channel binding is in use and the channel binding fails the server
   responds with a status code set to 412 to indicate that the channel
   binding precondition failed.  If the authentication scheme in use
   does not include signing the server SHOULD revoke the presented
   credential and the client SHOULD discard that credential.

3.3.  Use of Signature Type Authorization

   This mechanism supports authorization using signatures, which
   requires that both client and server construct the string to be
   signed.  OAuth 2 is designed for authentication/authorization to
   access specific URIs.  SASL is designed for user authentication, and
   has no facility for being more specific.  In this mechanism we
   require or define default values for the data elements from an HTTP
   request which allow the signature base string to be constructed
   properly.  The default HTTP path is "/" and the default post body is
   empty.  These atoms are defined as extension points so that no
   changes are needed if there is a revision of SASL which supports more
   specific resource authorization, e.g.  IMAP access to a specific
   folder or FTP access limited to a specific directory.

   Using the example in the MAC specification
   [I-D.ietf-oauth-v2-http-mac] as a starting point, on an IMAP server
   running on port 143 and given the MAC style authorization request
   (with %x01 shown as ^A and long lines wrapped for readability) below:



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   host=server.example.com^A
   port=143^A
   auth=MAC token="h480djs93hd8",timestamp="137131200",nonce="dj83hs9s",
            signature="YTVjyNSujYs1WsDurFnvFi4JK6o="^A^A

   The normalized request string would be constructed per the MAC
   specification [I-D.ietf-oauth-v2-http-mac].  In this example the
   normalized request string with the new line separator character is
   represented by "\n" for display purposes only would be:


   h480djs93hi8\n
   137131200\n
   dj83hs9s\n
   \n
   GET\n
   server.example.com\n
   143\n
   /\n
   \n

3.4.  Channel Binding

   If the specification for the underlying authorization scheme requires
   a security layer, such as TLS [RFC5246], the server SHOULD only offer
   a mechanism where channel binding can be enabled.

   The channel binding data is computed by the client based on it's
   choice of preferred channel binding type.  As specified in [RFC5056],
   the channel binding information MUST start with the channel binding
   unique prefix, followed by a colon (ASCII 0x3A), followed by a base64
   encoded channel binding payload.  The channel binding payload is the
   raw data from the channel binding type if the raw channel binding
   data is less than 500 bytes.  If the raw channel binding data is 500
   bytes or larger then a SHA-1 [RFC3174] hash of the raw channel
   binding data is computed.

   If the client is using tls-unique for a channel binding then the raw
   channel binding data equals the first TLS finished message.  This is
   under the 500 byte limit, so the channel binding payload sent to the
   server would be the base64 encoded first TLS finished message.

   In the case where the client has chosen tls-endpoint, the raw channel
   binding data is the certificate of the server the client connected
   to, which will frequently be 500 bytes or more.  If it is then the
   channel binding payload is the base64 encoded SHA-1 hash of the
   server certificate.




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4.  GSS-API OAuth Mechanism Specification

   Note: The normative references in this section are informational for
   SASL implementers, but they are normative for GSS-API implementers.

   The SASL OAuth mechanism is also a GSS-API mechanism and the messages
   described in Section 3 are the same, but

   1.  the GS2 header on the client's first message is excluded when
       OAUTH is used as a GSS-API mechanism, and

   2.  initial context token header is prefixed to the client's first
       authentication message (context token), as described in Section
       3.1 of RFC 2743,

   The GSS-API mechanism OID for OAuth is [[TBD: IANA]].

   OAuth security contexts always have the mutual_state flag
   (GSS_C_MUTUAL_FLAG) set to TRUE.  OAuth supports credential
   delegation, therefore security contexts may have the deleg_state flag
   (GSS_C_DELEG_FLAG) set to either TRUE or 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].

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

   OAuth supports a standard generic name syntax for acceptors, such as
   GSS_C_NT_HOSTBASED_SERVICE (see [RFC2743], Section 4.1).  These
   service names MUST be associated with the "entityID" claimed by the
   RP.  OAuth supports only a single name type for initiators:
   GSS_C_NT_USER_NAME.  GSS_C_NT_USER_NAME is the default name type.
   The query, display, and exported name syntaxes for OAuth principal
   names are all the same.  There is no OAuth-specific name syntax;
   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, conform to
   [RFC2743], Section 3.2, but the "NAME" part of the token should be
   treated as a potential input string to the OAuth name normalization
   rules.




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5.  Examples

   These example illustrate exchanges between an IMAP client and an IMAP
   server.

5.1.  Successful Bearer Token Exchange

   This example shows a successful OAuth 2.0 bearer token exchange with
   an initial client response.  Note that line breaks are inserted for
   readability.


   S: * IMAP4rev1 Server Ready
   C: t0 CAPABILITY
   S: * CAPABILITY IMAP4rev1 AUTH=OAUTH
   S: t0 OK Completed
   C: t1 AUTHENTICATE OAUTH aG9zdD1zZXJ2ZXIuZXhhbXBsZS5jb20BcG9ydD0xNDMB
         YXV0aD1CRUFSRVIgdkY5ZGZ0NHFtVGMyTnZiM1JsY2tCaGJIUmhkbWx6ZEdFdVk
         yOXRDZz09AQE=
   S: +
   S: t1 OK SASL authentication succeeded

   As required by IMAP [RFC3501], the payloads are base64-encoded.  The
   decoded initial client response (with %x01 represented as ^A and long
   lines wrapped for readability) is:


   host=server.example.com^Aport=143^A
   auth=BEARER "vF9dft4qmTc2Nvb3RlckBhbHRhdmlzdGEuY29tCg=="^A^A

   The line containing just a "+" and a space is an empty response from
   the server.  This response contains error information, and in the
   success case the error response is empty.  Like other messages, and
   in accordance with the IMAP SASL binding, the empty response is
   base64-encoded.

5.2.  MAC Authentication with Channel Binding

   This example shows a channel binding failure.  The example sends the
   same request as above, but in the context of an OAUTH-PLUS exchange
   the channel binding information is missing.  Note that line breaks
   are inserted for readability.









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S: * CAPABILITY IMAP4rev1 AUTH=OAUTH SASL-IR IMAP4rev1 Server Ready
S: t0 OK Completed
C: t1 AUTHENTICATE MAC aG9zdD1zZXJ2ZXIuZXhhbXBsZS5jb20BcG9ydD0xNDMBYXV0a
   D1NQUMgdG9rZW49Img0ODBkanM5M2hkOCIsdGltZXN0YW1wPSIxMzcxMzEyMDAiLG5vbm
   NlPSJkajgzaHM5cyIsc2lnbmF0dXJlPSJZVFZqeU5TdWpZczFXc0R1ckZudkZpNEpLNm8
   9IgFjYmRhdGE9U0c5M0lHSnBaeUJwY3lCaElGUk1VeUJtYVc1aGJDQnRaWE56WVdkbFB3
   bz0BAQ==
S: +
S: t1 OK SASL authentication succeeded

   As required by IMAP [RFC3501], the payloads are base64-encoded.  The
   decoded initial client response (with %x01 represented as ^A and long
   lines wrapped for readability) is:


   -
   host=server.example.com^A
   port=143^A
   auth=MAC token="h480djs93hd8",timestamp="137131200",nonce="dj83hs9s",
            signature="YTVjyNSujYs1WsDurFnvFi4JK6o="^A
   cbdata=SG93IGJpZyBpcyBhIFRMUyBmaW5hbCBtZXNzYWdlPwo=^A^A

   The line containing just a "+" and a space is an empty response from
   the server.  This response contains discovery information, and in the
   success case no discovery information is necessary so the response is
   empty.  Like other messages, and in accordance with the IMAP SASL
   binding, the empty response is base64-encoded.

5.3.  Failed Exchange

   This example shows a failed exchange because of the empty
   Authorization header, which is how a client can query for the needed
   scope.  Note that line breaks are inserted for readability.


   S: * CAPABILITY IMAP4rev1 AUTH=OAUTH SASL-IR IMAP4rev1 Server Ready
   S: t0 OK Completed
   C: t1 AUTHENTICATE OAUTH aG9zdD1zZXJ2ZXIuZXhhbXBsZS5jb20BcG9ydD0xND
      MBYXV0aD0BAQ==
   S: + ewoic3RhdHVzIjoiNDAxIiwKInNjb3BlIjoiZXhhbXBsZV9zY29wZSIKfQo=
   S: t1 NO SASL authentication failed

   The decoded initial client response is:


   host=server.example.com^Aport=143^Aauth=^A^A

   The decoded server error response is:



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   {
   "status":"401",
   "scope":"example_scope"
   }

5.4.  Failed Channel Binding

   This example shows a channel binding failure in an empty request.
   The channel binding information is empty.  Note that line breaks are
   inserted for readability.


   S: * CAPABILITY IMAP4rev1 AUTH=OAUTH SASL-IR IMAP4rev1 Server Ready
   S: t0 OK Completed
   C: t1 AUTHENTICATE OAUTH aG9zdD1zZXJ2ZXIuZXhhbXBsZS5jb20BcG9ydD0xND
      MBYXV0aD0BY2JkYXRhPQEB
   S: + ewoic3RhdHVzIjoiNDEyIiwKInNjb3BlIjoiZXhhbXBsZV9zY29wZSIKfQ==
   S: t1 NO SASL authentication failed

   The decoded initial client response is:


   host=server.example.com^Aport=143^Aauth=^Acbdata=^A^A

   The decoded server response is:


   {
   "status":"412",
   "scope":"example_scope"
   }




















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6.  Security Considerations

   This mechanism does not provide a security layer, but does provide a
   provision for channel binding.  The OAuth 2 specification
   [I-D.ietf-oauth-v2] allows for a variety of usages, and the security
   properties of these profiles vary.  The usage of bearer tokens, for
   example, provide security features similar to cookies.  Applications
   using this mechanism SHOULD exercise the same level of care using
   this mechanism as they would in using the SASL PLAIN mechanism.  In
   particular, TLS 1.2 or an equivalent secure channel MUST be
   implemented and its usage is RECOMMENDED.

   Channel binding in this mechanism has different properties based on
   the authentication scheme used.  Channel binding to TLS with a bearer
   token provides only a binding to the TLS layer.  Authentication
   schemes like MAC tokens can implement a signature over the channel
   binding information.  These provide additional protection against a
   man in the middle attacks, and the MAC authorization header is bound
   to the channel and only valid in that context.

   It is possible that SASL will be authenticating a connection and the
   life of that connection may outlast the life of the token used to
   authenticate it.  This is a common problem in application protocols
   where connections are long-lived, and not a problem with this
   mechanism per se.  Servers MAY unilaterally disconnect clients in
   accordance with the application protocol.

   An OAuth credential is not equivalent to the password or primary
   account credential.  There are protocols like XMPP that allow actions
   like change password.  The server SHOULD ensure that actions taken in
   the authenticated channel are appropriate to the strength of the
   presented credential.

   Tokens have a lifetime associated with them.  Reducing the lifetime
   of a token provides security benefits in case that tokens leak.  In
   addition a previously obtained token MAY be revoked or rendered
   invalid at any time.  The client MAY request a new access token for
   each connection to a resource server, but it SHOULD cache and re-use
   access credentials that appear to be valid.












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7.  IANA Considerations

7.1.  SASL Registration

   The IANA is requested to register the following SASL profile:

      SASL mechanism profile: OAUTH

      Security Considerations: See this document

      Published Specification: See this document

      For further information: Contact the authors of this document.

      Owner/Change controller: the IETF

      Note: None

   The IANA is requested to register the following SASL profile:

      SASL mechanism profile: OAUTH-PLUS

      Security Considerations: See this document

      Published Specification: See this document

      For further information: Contact the authors of this document.

      Owner/Change controller: the IETF

      Note: None

7.2.  GSS-API Registration

   IANA is further requested to assign an OID for this GSS mechanism in
   the SMI numbers registry, with the prefix of
   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.  Appendix A -- Document History

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

   -01

   o  Ripping out discovery.  Changed to refer to I-D.jones-appsawg-
      webfinger instead of WF and SWD older drafts.

   o  Replacing HTTP as the message format and adjusted all examples.

   -00

   o  Renamed draft into proper IETF naming format now that it's
      adopted.

   o  Minor fixes.

   -00

   o  Initial revision






























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9.  References

9.1.  Normative References

   [I-D.ietf-oauth-v2]
              Hammer-Lahav, E., Recordon, D., and D. Hardt, "The OAuth
              2.0 Authorization Framework", draft-ietf-oauth-v2-26 (work
              in progress), May 2012.

   [I-D.ietf-oauth-v2-bearer]
              Jones, M., Hardt, D., and D. Recordon, "The OAuth 2.0
              Authorization Protocol: Bearer Tokens",
              draft-ietf-oauth-v2-bearer-19 (work in progress),
              April 2012.

   [I-D.ietf-oauth-v2-http-mac]
              Hammer-Lahav, E., "HTTP Authentication: MAC Access
              Authentication", draft-ietf-oauth-v2-http-mac-01 (work in
              progress), February 2012.

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

   [RFC2234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 2234, November 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.

   [RFC2617]  Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
              Leach, P., Luotonen, A., and L. Stewart, "HTTP
              Authentication: Basic and Digest Access Authentication",
              RFC 2617, June 1999.

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

   [RFC3174]  Eastlake, D. and P. Jones, "US Secure Hash Algorithm 1
              (SHA1)", RFC 3174, September 2001.

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

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

   [RFC5056]  Williams, N., "On the Use of Channel Bindings to Secure



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              Channels", RFC 5056, November 2007.

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

   [RFC5849]  Hammer-Lahav, E., "The OAuth 1.0 Protocol", RFC 5849,
              April 2010.

   [RFC5929]  Altman, J., Williams, N., and L. Zhu, "Channel Bindings
              for TLS", RFC 5929, July 2010.

   [RFC5988]  Nottingham, M., "Web Linking", RFC 5988, October 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.

9.2.  Informative References

   [I-D.jones-appsawg-webfinger]
              Jones, P., Salgueiro, G., and J. Smarr, "WebFinger",
              draft-jones-appsawg-webfinger-05 (work in progress),
              May 2012.

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


















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Authors' Addresses

   William Mills
   Yahoo! Inc.


   Phone:
   Email: wmills@yahoo-inc.com


   Tim Showalter


   Phone:
   Email: tjs@psaux.com


   Hannes Tschofenig
   Nokia Siemens Networks
   Linnoitustie 6
   Espoo  02600
   Finland

   Phone: +358 (50) 4871445
   Email: Hannes.Tschofenig@gmx.net
   URI:   http://www.tschofenig.priv.at

























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