Internet DRAFT - draft-hunt-secevent-sstp

draft-hunt-secevent-sstp







Network Working Group                                       P. Hunt, Ed.
Internet-Draft                                                    Oracle
Intended status: Standards Track                              A. Nadalin
Expires: September 23, 2018                                    Microsoft
                                                          March 22, 2018


                    Symmetric SET Transfer Protocol
                      draft-hunt-secevent-sstp-00

Abstract

   This specification defines how security event tokens (SETs) may be
   exchanged between a client and service provider using HTTP POST over
   TLS using a symmetric format.  The specification supports three modes
   of operation: "push", "pull", and "push-pull" bi-directional SET
   exchange.  The specification also defines a simple acknowledge
   mechanism allowing parties to confirm delivery.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 September 23, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   4
     1.2.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Simple SET Transfer Protocol  . . . . . . . . . . . . . . . .   5
     2.1.  SSTP Message Format (Content-Type: application/sstp+json)   5
     2.2.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .   7
       2.2.1.  Example Push Transfer . . . . . . . . . . . . . . . .   8
       2.2.2.  Example Pull Transfer . . . . . . . . . . . . . . . .   9
       2.2.3.  Example Push-Pull Bi-directional Transfer . . . . . .  13
     2.3.  Error Response Handling . . . . . . . . . . . . . . . . .  15
   3.  Authentication and Authorization  . . . . . . . . . . . . . .  16
     3.1.  Use of Tokens as Authorizations . . . . . . . . . . . . .  17
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  18
     4.1.  Authentication Using Signed SETs  . . . . . . . . . . . .  18
     4.2.  HTTP Considerations . . . . . . . . . . . . . . . . . . .  18
     4.3.  TLS Support Considerations  . . . . . . . . . . . . . . .  18
     4.4.  Authorization Token Considerations  . . . . . . . . . . .  19
       4.4.1.  Bearer Token Considerations . . . . . . . . . . . . .  19
   5.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  19
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  20
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  20
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  21
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  22
   Appendix B.  Change Log . . . . . . . . . . . . . . . . . . . . .  23
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23

1.  Introduction

   [EDITORS NOTE: This specification is based upon draft-ietf-secevent-
   delivery and attempts to provide a unified single MTI protocol
   solution satisfying all use cases for SECEVENTS.]

   This specification defines how SETs (see [I-D.ietf-secevent-token])
   can be exchanged using HTTP [RFC7231] over TLS using a symmetric
   request/response format.  The specification supports three modes of
   operation: "push", "pull", and "push-pull" bi-directional SET
   exchange.  The specification also defines a simple acknowledge
   mechanism allowing parties to confirm delivery or attempt re-
   delivery.

   This specification makes several simplifying assumptions:




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   o  SSTP is a symmetric protocol meaning it uses the same HTTP
      content-type and JSON structure to send requests and process
      responses

   o  Recovery is provided for unacknowledged SETs for short term or
      missed deliveries.  Issuers are able to re-transmit SETs in
      situations where a SET has been unacknowledged (e.g. over more
      than one request/response cycles).

   o  The protocol can be used for unidirectional, or bi-directional
      communication avoiding the need to implement multiple delivery
      methods.

   o  The use of HTTP Long Polling MAY be used in cases where pull or
      bi-directional communication is needed in real time.

   o  Only one party in an exchange needs to have an addressable fixed
      URI endpoint and can act as an SSTP protocol service provider to a
      mobile or otherwise unrechable client.

   o  SET message exchanges are secured through the use of TLS and some
      form of HTTP authorization (e.g.  RFC6750, RFC7519), and MAY in
      turn be signed and encrypted.

   This specification supports the following use-cases:

   Broadcaster
      Where a large entity (e.g. an Identity Provider) needs to issue
      SETs to a large number of relying parties.

   Protected Client
      Where a client party is behind a firewall or otherwise network
      restricted location and cannot act as a SSTP service provider.
      Examples include Enterprise on-premise security systems, IoT
      devices which may be shielded in restricted network environments.

   Mobile
      Where a client is mobile and thus would be unable to maintain a
      permanent HTTP endpoint.

   This specification does not define how endpoints are configured, nor
   does it define the specifics of which SET event types are exchanged
   over any particular delivery relationship.








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1.1.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   For purposes of readability examples are not URL encoded.
   Implementers MUST percent encode URLs as described in Section 2.1 of
   [RFC3986] .

   Throughout this documents all figures MAY contain spaces and extra
   line-wrapping for readability and space limitations.  Similarly, some
   URI's contained within examples, have been shortened for space and
   readability reasons.  All examples are non-normative.

1.2.  Definitions

   This specification assumes terminology defined in the Security Event
   Token specification[I-D.ietf-secevent-token] .

   This specification defines the following terms:

   Client  An entity which acts as an HTTP client as defined by
      [RFC7231] which is communicating with an SSTP server.

   Server  An entity which has a permanent endpoint reachable by a
      client which acts as an HTTP server as defined by [RFC7231] and
      supports this specification.

   Event
      An Event is defined to be an event as represented by a security
      event token (SET).  See [I-D.ietf-secevent-token].

   NumericDate
      A JSON numeric value representing the number of seconds from
      1970-01-01T00:00:00Z UTC until the specified UTC date/time,
      ignoring leap seconds.  This is equivalent to the IEEE Std 1003.1,
      2013 Edition [POSIX.1] definition "Seconds Since the Epoch", in
      which each day is accounted for by exactly 86400 seconds, other
      than that non-integer values can be represented.  See [RFC3339]
      for details regarding date/times in general and UTC in particular.








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2.  Simple SET Transfer Protocol

   SSTP is a symmetric protocol.  As such an SSTP client uses HTTP POST
   (Section 4.3.3 [RFC7231]) with a body with "Content-Type" of
   "application/sstp+json" to deliver 0 or more SETs and/or to
   acknowledge previously received SETs from an SSTP server.  In
   response, the SSTP server returns an HTTP body with the same
   document-type which may also return 0 or more SETs, acknowledgments,
   and errors.

   Requests MAY be spontaneous (in the case of push mode), scheduled
   over a a periodic interval (in the case of pull), or requests to pull
   MAY await new SETS using HTTP long polling (see Section 2 [RFC6202]).
   An SSTP server choosing NOT to support HTTP long polling MAY do so by
   returning HTTP Status of 403 "Forbidden" (see Section 6.5.3
   [RFC7231]) if a particular client is not authorized, or HTTP status
   501 "Not implemented" (see Section 6.6.2 [RFC7231]) if the server
   does not support long polling.

   SSTP provides an acknowledgement capability for the purpose of
   informing communications partners about which SETs have been
   successfully delivered.  Upon receipt of a SET and before
   acknowledgement, receivers SHOULD ensure received SETs are valid and
   have been retained in a manner appropriate to the receiver's
   retention needs.  The level and method of retention of SETs by
   receivers is out-of-scope of this specification.

   If after a period of time, negotiated between the client and server,
   unacknowledged SETs MAY be re-transmitted.  The receiver SHOULD
   accept repeat SETs and acknowledge the SETs regardless of whether the
   receiver believes it has already acknowledged the SETs previously.  A
   SET issuer MAY limit the number of attempts to deliver a SET.

   A receiving party (client or server) of SETs SHOULD parse and
   validate each SET to meet its own requirements and SHOULD acknowledge
   receipt in a timely (e.g. minutes) fashion so that the issuer may
   mark the SETs as received.  Receivers SHOULD acknowledge receipt
   before taking any local actions based on the SETs to avoid
   unnecessary delay in acknowledgement to avoid unnecessary re-
   transmission.

2.1.  SSTP Message Format (Content-Type: application/sstp+json)

   The body (or message) of an SSTP request or response is a "Content-
   Type" of "application/sstp+json" which is a JSON document consisting
   of the following optional JSON attributes:

   Request Handling:



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   returnEvents
      A JSON boolean parameter which indicates whether the receiver
      SHOULD return SETs in its upcoming response.  When part of an HTTP
      Request, it indicates the SSTP server SHOULD return with SETs in
      its response (and optionally wait).  When asserted as "false" by
      an SSTP server in its response, it indicates that the SSTP server
      is not requesting SETs in the next client request.  If omitted,
      this attribute SHALL have a default value of "true".

   returnImmediately
      An OPTIONAL JSON boolean value which when "true" has the effect of
      declining HTTP long polling.  A value of "false" indicates the
      request is to be treated as an HTTP Long Poll (see Section 2
      [RFC6202]).  When asserted in an HTTP response, the value
      indicates the SSTP has more information and the client SHOULD NOT
      wait before initiating its next request.  When omitted, the
      default value of "false" SHALL be assumed.

   Delivery:

   sets
      A JSON object that contains one or more nested JSON attributes.
      Each nested attribute corresponds to the "jti" of a SET to be
      delivered and whose value is a JSON String containing the value of
      the encoded corresponding SET.  If there are no SETs to be
      transmitted, the attribute MAY be omitted.

   Acknowledgment:

   ack
      An array of Strings that each correspond to the "jti" of a
      successfully received SET by the client.  If there are no
      outstanding SETs to acknowledge, the attribute MAY be omitted.
      When acknowledging a SET, the issuer is released from any
      obligation to retain the SET (e.g. for a future re-try).

   setErrs
      A JSON Object that contains one or more nested JSON attributes
      that correspond to the "jti" of each invalid SET received.  The
      value of each is a JSON object whose contents is an "err"
      attribute and "description" attribute whose value correspond to
      the errors described in Section 2.3.  If there are no errors to
      acknowledge, the attribute MAY be omitted.








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   The following is an example SSTP message that could be exchanged
   either in a HTPP POST request or response between a client and an
   SSTP server.

  {
  "returnImmediately":true,
  "returnEvents":true,
  "sets":{
    "4d3559ec67504aaba65d40b0363faad8":
     "eyJhbGciOiJub25lIn0.
     eyJqdGkiOiI0ZDM1NTllYzY3NTA0YWFiYTY1ZDQwYjAzNjNmYWFkOCIsImlhdCI6MTQ
     1ODQ5NjQwNCwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbIm
     h0dHBzOi8vc2NpbS5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M
     2I3NzU0IiwiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIx
     ZDA4NjQxZDc2NzZlZTciXSwiZXZlbnRzIjp7InVybjppZXRmOnBhcmFtczpzY2ltOmV
     2ZW50OmNyZWF0ZSI6eyJyZWYiOiJodHRwczovL3NjaW0uZXhhbXBsZS5jb20vVXNlcn
     MvNDRmNjE0MmRmOTZiZDZhYjYxZTc1MjFkOSIsImF0dHJpYnV0ZXMiOlsiaWQiLCJuY
     W1lIiwidXNlck5hbWUiLCJwYXNzd29yZCIsImVtYWlscyJdfX19.",
    "3d0c3cf797584bd193bd0fb1bd4e7d30":
     "eyJhbGciOiJub25lIn0.
     eyJqdGkiOiIzZDBjM2NmNzk3NTg0YmQxOTNiZDBmYjFiZDRlN2QzMCIsImlhdCI6MTQ
     1ODQ5NjAyNSwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbIm
     h0dHBzOi8vamh1Yi5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M
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     Y6cGFyYW1zOnNjaW06ZXZlbnQ6cGFzc3dvcmRSZXNldCI6eyJpZCI6IjQ0ZjYxNDJkZ
     jk2YmQ2YWI2MWU3NTIxZDkifSwiaHR0cHM6Ly9leGFtcGxlLmNvbS9zY2ltL2V2ZW50
     L3Bhc3N3b3JkUmVzZXRFeHQiOnsicmVzZXRBdHRlbXB0cyI6NX19fQ."
   }
  }

              Figure 1: Example Request or Response Document

2.2.  Examples

   Three examples are provided where:

   o  A client pushes SETs to a server using the "sets" JSON attribute
      in its request and receives "ack" values in response from the SSTP
      server.

   o  A polling client that requests SETs from a a server and uses the
      "ack" parameter in its request to acknowledge SETs from a previous
      HTTP request, and receives new SETs in the response.






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   o  A client and SSTP server bi-directionally exchange SETs using both
      the "sets" and "ack" JSON attributes in both the request and
      response messages.

2.2.1.  Example Push Transfer

   In this example, a client posts SETs to an SSTP server which in turn
   acknowledges the transferred SETs in its response.

   In the figure, two SETs are transferred to the SSTP server.  The
   parameter "returnEvents" indicates the client is not interested in
   receiving SETs.

  POST /Events  HTTP/1.1

  Host: notify.exampleidp.com
  Authorization: Bearer h480djs93hd8
  Content-Type: application/sstp+json
  Accept: application/sstp+json
  {
  "returnImmediately":true,
  "returnEvents":false,
  "sets":{
    "4d3559ec67504aaba65d40b0363faad8":
     "eyJhbGciOiJub25lIn0.
     eyJqdGkiOiI0ZDM1NTllYzY3NTA0YWFiYTY1ZDQwYjAzNjNmYWFkOCIsImlhdCI6MTQ
     1ODQ5NjQwNCwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbIm
     h0dHBzOi8vc2NpbS5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M
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     W1lIiwidXNlck5hbWUiLCJwYXNzd29yZCIsImVtYWlscyJdfX19.",
    "3d0c3cf797584bd193bd0fb1bd4e7d30":
     "eyJhbGciOiJub25lIn0.
     eyJqdGkiOiIzZDBjM2NmNzk3NTg0YmQxOTNiZDBmYjFiZDRlN2QzMCIsImlhdCI6MTQ
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     zZXJzLzQ0ZjYxNDJkZjk2YmQ2YWI2MWU3NTIxZDkiLCJldmVudHMiOnsidXJuOmlldG
     Y6cGFyYW1zOnNjaW06ZXZlbnQ6cGFzc3dvcmRSZXNldCI6eyJpZCI6IjQ0ZjYxNDJkZ
     jk2YmQ2YWI2MWU3NTIxZDkifSwiaHR0cHM6Ly9leGFtcGxlLmNvbS9zY2ltL2V2ZW50
     L3Bhc3N3b3JkUmVzZXRFeHQiOnsicmVzZXRBdHRlbXB0cyI6NX19fQ."
   }
  }

                      Figure 2: Example Push Request



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   The figure below shows the response returned from the SSTP server in
   response to the request in Figure 2

   HTTP/1.1 200 OK
   Content-Type: application/sstp+json
   Location: https://notify.exampleidp.com/Events

   {
     "ack":[
       "4d3559ec67504aaba65d40b0363faad8",
       "3d0c3cf797584bd193bd0fb1bd4e7d30"
     ]
   }

                      Figure 3: Example Push Response

2.2.2.  Example Pull Transfer

   The figure below is an example pull request to the SSTP server whose
   location is: "https://nofity.exampleidp.com/Events".  In this
   example, the client is requesting an immediate response whether or
   not new SETs are available.

   POST /Events  HTTP/1.1

   Host: notify.exampleidp.com
   Authorization: Bearer h480djs93hd8
   Content-Type: application/sstp+json
   Accept: application/sstp+json

   {
    "returnImmediately":true
   }

                  Figure 4: Example Initial Pull Request

   The following is an example default pull request to the SSTP server
   whose location is: "https://nofity.exampleidp.com/Events".  The
   default mode to return events and to wait if necessary is assumed.

   POST /Events  HTTP/1.1
   Host: notify.exampleidp.com
   Authorization: Bearer h480djs93hd8
   Accept: application/sstp+json

   {}

                  Figure 5: Example Default Pull Request



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   In response to the above two requests, the SSTP server responds
   immediately if "respondImmediately" is true or SETs are available.
   If no SETs are available at the time of the request and
   "respondImmediately" is false, the SSTP server delays response until
   a SET is available.

   As described in Section 2.1 a JSON document is returned containing
   the JSON attribute "sets".

   The following is an example response to the requests shown Figure 4
   and Figure 5.  This example shows two SETs are returned.

  HTTP/1.1 200 OK
  Content-Type: application/sstp+json
  Location: https://notify.exampleidp/Events

  {
  "sets":{
    "4d3559ec67504aaba65d40b0363faad8":
     "eyJhbGciOiJub25lIn0.
     eyJqdGkiOiI0ZDM1NTllYzY3NTA0YWFiYTY1ZDQwYjAzNjNmYWFkOCIsImlhdCI6MTQ
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     W1lIiwidXNlck5hbWUiLCJwYXNzd29yZCIsImVtYWlscyJdfX19.",
    "3d0c3cf797584bd193bd0fb1bd4e7d30":
     "eyJhbGciOiJub25lIn0.
     eyJqdGkiOiIzZDBjM2NmNzk3NTg0YmQxOTNiZDBmYjFiZDRlN2QzMCIsImlhdCI6MTQ
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     Y6cGFyYW1zOnNjaW06ZXZlbnQ6cGFzc3dvcmRSZXNldCI6eyJpZCI6IjQ0ZjYxNDJkZ
     jk2YmQ2YWI2MWU3NTIxZDkifSwiaHR0cHM6Ly9leGFtcGxlLmNvbS9zY2ltL2V2ZW50
     L3Bhc3N3b3JkUmVzZXRFeHQiOnsicmVzZXRBdHRlbXB0cyI6NX19fQ."
   }
  }

                      Figure 6: Example Pull Response

   In the above example, two SETs whose "jti" are
   "4d3559ec67504aaba65d40b0363faad8" and
   "3d0c3cf797584bd193bd0fb1bd4e7d30" are delivered.




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   The following is an example response to the request shown Figure 4
   where "returnImmediately" was set showing no new SETs are available.

   HTTP/1.1 200 OK
   Content-Type: application/sstp+json
   Location: https://notify.exampleidp/Events

   {
    "sets":{ }
   }

                  Figure 7: Example No SETs Pull Response

2.2.2.1.  Acknowledge Only Request

   This variation is typically used when a client needs to acknowledge
   received SETs on a separate thread from one receiving SETs.

   An SSTP client acknowledges previously received SETs but indicates it
   does not want to receive SETs in the current request/response by
   setting the "returnEvents" attribute to "false".

   The following example is an acknowledgement of SETs previously
   received (e.g. from the response shown in Figure 6).

   POST /Events  HTTP/1.1
   Host: notify.exampleidp.com
   Authorization: Bearer h480djs93hd8
   Content-Type: application/sstp+json
   Authorization: Bearer h480djs93hd8

   {
     "ack":[
       "4d3559ec67504aaba65d40b0363faad8",
       "3d0c3cf797584bd193bd0fb1bd4e7d30"
     ],
     "returnEvents":false
   }

                Figure 8: Example Acknowledge Only Request

2.2.2.2.  Poll with Acknowledgement

   This variation allows a client to simultaneously acknowledge
   previously received SETs and wait for the next group of SETs in a
   single HTTP request.





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   The following SSTP request contains an acknowledgement of SETs
   received from Figure 6.

   POST /Events  HTTP/1.1

   Host: notify.exampleidp.com
   Authorization: Bearer h480djs93hd8
   Content-Type: application/sstp+json
   Accept: application/sstp+json
   Authorization: Bearer h480djs93hd8

   {
     "ack":[
       "4d3559ec67504aaba65d40b0363faad8",
       "3d0c3cf797584bd193bd0fb1bd4e7d30"
     ],
     "returnImmediately":false
   }

         Figure 9: Example Pull With Acknowledgement and No Errors

2.2.2.3.  Pull with Acknowledgement and Errors

   In the case where errors are detected in previously received SETs,
   the client (or server) uses the "setErrs" attribute to indicate
   errors in its request.

























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   The following is an example of an SSTP response acknowledges 1 error
   and 1 receipt of two SETs received in Figure 6.

   POST /Events  HTTP/1.1

   Host: notify.exampleidp.com
   Authorization: Bearer h480djs93hd8
   Content-Type: application/sstp+json
   Accept: application/sstp+json
   Authorization: Bearer h480djs93hd8

   {
     "ack":["3d0c3cf797584bd193bd0fb1bd4e7d30"],
     "setErrs":{
       "4d3559ec67504aaba65d40b0363faad8":{
         "err":"jwtAud",
         "description":"The audience value was incorrect."
       }
     }
   }

            Figure 10: Example Pull Acknowledgement With Error

2.2.3.  Example Push-Pull Bi-directional Transfer

   In push-pull mode, JSON attributes "sets", "ack" and "setErrs" are
   used in both HTTP request and response messages between client and
   SSTP server.























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   In the following example, two SETs are transferred to the SSTP server
   and events are requested in return.

  POST /Events  HTTP/1.1
  Host: notify.exampleidp.com
  Authorization: Bearer h480djs93hd8
  Content-Type: application/sstp+json
  Accept: application/sstp+json
  {
  "returnEvents":true,
  "ack":["b453bf9972b84e0492d5c7f55f68fb6a"],
  "sets":{
    "4d3559ec67504aaba65d40b0363faad8":
     "eyJhbGciOiJub25lIn0.
     eyJqdGkiOiI0ZDM1NTllYzY3NTA0YWFiYTY1ZDQwYjAzNjNmYWFkOCIsImlhdCI6MTQ
     1ODQ5NjQwNCwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbIm
     h0dHBzOi8vc2NpbS5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M
     2I3NzU0IiwiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIx
     ZDA4NjQxZDc2NzZlZTciXSwiZXZlbnRzIjp7InVybjppZXRmOnBhcmFtczpzY2ltOmV
     2ZW50OmNyZWF0ZSI6eyJyZWYiOiJodHRwczovL3NjaW0uZXhhbXBsZS5jb20vVXNlcn
     MvNDRmNjE0MmRmOTZiZDZhYjYxZTc1MjFkOSIsImF0dHJpYnV0ZXMiOlsiaWQiLCJuY
     W1lIiwidXNlck5hbWUiLCJwYXNzd29yZCIsImVtYWlscyJdfX19.",
    "3d0c3cf797584bd193bd0fb1bd4e7d30":
     "eyJhbGciOiJub25lIn0.
     eyJqdGkiOiIzZDBjM2NmNzk3NTg0YmQxOTNiZDBmYjFiZDRlN2QzMCIsImlhdCI6MTQ
     1ODQ5NjAyNSwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbIm
     h0dHBzOi8vamh1Yi5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M
     2I3NzU0IiwiaHR0cHM6Ly9qaHViLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIx
     ZDA4NjQxZDc2NzZlZTciXSwic3ViIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL1V
     zZXJzLzQ0ZjYxNDJkZjk2YmQ2YWI2MWU3NTIxZDkiLCJldmVudHMiOnsidXJuOmlldG
     Y6cGFyYW1zOnNjaW06ZXZlbnQ6cGFzc3dvcmRSZXNldCI6eyJpZCI6IjQ0ZjYxNDJkZ
     jk2YmQ2YWI2MWU3NTIxZDkifSwiaHR0cHM6Ly9leGFtcGxlLmNvbS9zY2ltL2V2ZW50
     L3Bhc3N3b3JkUmVzZXRFeHQiOnsicmVzZXRBdHRlbXB0cyI6NX19fQ."
   }
  }

                   Figure 11: Example Push-Pull Request














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   The following is an example response to the request shown Figure 11.

  HTTP/1.1 200 OK
  Content-Type: application/sstp+json
  Location: https://notify.exampleidp/Events

  {
  "ack":[
    "4d3559ec67504aaba65d40b0363faad8",
    "3d0c3cf797584bd193bd0fb1bd4e7d30"
  ],
  "sets":{
    "6f332aefc730400a9f645d36a12ba4ab":
     "eyJhbGciOiJub25lIn0.
     eyJqdGkiOiI0ZDM1NTllYzY3NTA0YWFiYTY1ZDQwYjAzNjNmYWFkOCIsImlhdCI6MTQ
     1ODQ5NjQwNCwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbIm
     h0dHBzOi8vc2NpbS5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M
     2I3NzU0IiwiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIx
     ZDA4NjQxZDc2NzZlZTciXSwiZXZlbnRzIjp7InVybjppZXRmOnBhcmFtczpzY2ltOmV
     2ZW50OmNyZWF0ZSI6eyJyZWYiOiJodHRwczovL3NjaW0uZXhhbXBsZS5jb20vVXNlcn
     MvNDRmNjE0MmRmOTZiZDZhYjYxZTc1MjFkOSIsImF0dHJpYnV0ZXMiOlsiaWQiLCJuY
     W1lIiwidXNlck5hbWUiLCJwYXNzd29yZCIsImVtYWlscyJdfX19."
   }
  }

                   Figure 12: Example Push-Pull Response

   Following the response from the SSTP server, the client would
   subsequently repeats the request-response cycle by acknowledging the
   SET identified by a "jti" value of
   "6f332aefc730400a9f645d36a12ba4ab".

2.3.  Error Response Handling

   If a SET is invalid, the following error codes are defined:
















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   +-------------+-----------------------------------------------------+
   | Err Value   | Description                                         |
   +-------------+-----------------------------------------------------+
   | json        | Invalid JSON object.                                |
   | jwtParse    | Invalid or unparsable JWT or JSON structure.        |
   | jwtHdr      | In invalid JWT header was detected.                 |
   | jwtCrypto   | Unable to parse due to unsupported algorithm.       |
   | jws         | Signature was not validated.                        |
   | jwe         | Unable to decrypt JWE encoded data.                 |
   | jwtAud      | Invalid audience value.                             |
   | jwtIss      | Issuer not recognized.                              |
   | setType     | An unexpected Event type was received.              |
   | setParse    | Invalid structure was encountered such as an        |
   |             | inability to parse or an incomplete set of event    |
   |             | claims.                                             |
   | setData     | SET event claims incomplete or invalid.             |
   | directional | The SSTP does not support transfer of SETs in the   |
   |             | requested direction.                                |
   +-------------+-----------------------------------------------------+

                            Table 1: SET Errors

   An error response has a "Content-Type" of "application/sstp+json"
   which is a JSON document that provides details about the error.  The
   JSON document includes the JSON attributes:

   err
      A value which is a keyword that describes the error (see Table 1).

   description
      A human-readable text that provides additional diagnostic
      information.

   When included as part of an HTTP Status 400 response, the above JSON
   is the HTTP response body in the JSON attribute "setErrs" (see
   Section 2.1).

3.  Authentication and Authorization

   The SET delivery methods described in this specification are based
   upon HTTP and depend on the use of TLS and/or standard HTTP
   authentication and authorization schemes as per [RFC7235].  For
   example, the following methodologies could be used among others:

   TLS Client Authentication
      SSTP server MAY negotiate TLS mutual client authentication.  See
      Section 7.3 [RFC5246].




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   Bearer Tokens
      Bearer tokens [RFC6750] MAY be used when combined with TLS and a
      token framework such as OAuth 2.0 [RFC6749].  For security
      considerations regarding the use of bearer tokens in SET delivery
      see Section 4.4.1.

   Basic Authentication
      Usage of basic authentication should be avoided due to its use of
      a single factor that is based upon a relatively static, symmetric
      secret.  Implementers SHOULD combine the use of basic
      authentication with other factors.  The security considerations of
      HTTP BASIC, are well documented in [RFC7617] and SHOULD be
      considered along with using signed SETs (see SET Payload
      Authentication below).

   SET Payload Authentication
      In scenarios where SETs are signed and the delivery method is HTTP
      POST, SSTP clients MAY elect to use Basic Authentication or not to
      use HTTP or TLS based authentication at all.  See Section 4.1 for
      considerations.

   As per Section 4.1 of [RFC7235], a SET delivery endpoint SHALL
   indicate supported HTTP authentication schemes via the "WWW-
   Authenticate" header.

   Because SET Delivery describes a simple function, authorization for
   the ability to pick-up or deliver SETs can be derived by considering
   the identity of the SET issuer, or via an authentication method
   above.  This specification considers authentication as a feature to
   prevent denial-of-service attacks.  Because SETs are not commands
   (see ), event receivers are free to ignore SETs that are not of
   interest.

   For illustrative purposes only, SET delivery examples show an OAuth2
   bearer token value [RFC6750] in the authorization header.  This is
   not intended to imply that bearer tokens are preferred.  However, the
   use of bearer tokens in the specification does reflect common
   practice.

3.1.  Use of Tokens as Authorizations

   When using bearer tokens or proof-of-possession tokens that represent
   an authorization grant such as issued by OAuth (see [RFC6749]),
   implementers SHOULD consider the type of authorization granted, any
   authorized scopes (see Section 3.3 of [RFC6749]), and the security
   subject(s) that SHOULD be mapped from the authorization when
   considering local access control rules.  Section 6 of the OAuth




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   Assertions draft [RFC7521], documents common scenarios for
   authorization including:

   o  Clients using an assertion to authenticate and/or act on behalf of
      itself;

   o  Clients acting on behalf of a user; and,

   o  A Client acting on behalf of an anonymous user (e.g., see next
      section).

   When using OAuth authorization tokens, implementers MUST take into
   account the threats and countermeasures documented in the security
   considerations for the use of client authorizations (see Section 8 of
   [RFC7521]).  When using other token formats or frameworks,
   implementers MUST take into account similar threats and
   countermeasures, especially those documented by the relevant
   specifications.

4.  Security Considerations

4.1.  Authentication Using Signed SETs

   In scenarios where HTTP authorization or TLS mutual authentication
   are not used or are considered weak, JWS signed SETs SHOULD be used
   (see [RFC7515] and Security Considerations
   [I-D.ietf-secevent-token]).  This enables event receivers to validate
   that the SET issuer is authorized to deliver SETs.

4.2.  HTTP Considerations

   SET delivery depends on the use of Hypertext Transfer Protocol and
   thus subject to the security considerations of HTTP Section 9
   [RFC7230] and its related specifications.

   As stated in Section 2.7.1 [RFC7230], an HTTP requestor MUST NOT
   generate the "userinfo" (i.e., username and password) component (and
   its "@" delimiter) when an "http" URI reference is generated with a
   message as they are now disallowed in HTTP.

4.3.  TLS Support Considerations

   SETs contain sensitive information that is considered PII (e.g.
   subject claims).  Therefore, event issuers and receivers MUST require
   the use of a transport-layer security mechanism.  Event delivery
   endpoints MUST support TLS 1.2 [RFC5246] and MAY support additional
   transport-layer mechanisms meeting its security requirements.  When
   using TLS, the client MUST perform a TLS/SSL server certificate



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   check, per [RFC6125].  Implementation security considerations for TLS
   can be found in "Recommendations for Secure Use of TLS and DTLS"
   [RFC7525].

4.4.  Authorization Token Considerations

   When using authorization tokens such as those issued by OAuth 2.0
   [RFC6749], implementers MUST take into account threats and
   countermeasures documented in Section 8 of [RFC7521].

4.4.1.  Bearer Token Considerations

   Due to the possibility of interception, Bearer tokens MUST be
   exchanged using TLS.

   Bearer tokens MUST have a limited lifetime that can be determined
   directly or indirectly (e.g., by checking with a validation service)
   by the service provider.  By expiring tokens, clients are forced to
   obtain a new token (which usually involves re-authentication) for
   continued authorized access.  For example, in OAuth2, a client MAY
   use OAuth token refresh to obtain a new bearer token after
   authenticating to an authorization server.  See Section 6 of
   [RFC6749].

   Implementations supporting OAuth bearer tokens need to factor in
   security considerations of this authorization method [RFC7521].
   Since security is only as good as the weakest link, implementers also
   need to consider authentication choices coupled with OAuth bearer
   tokens.  The security considerations of the default authentication
   method for OAuth bearer tokens, HTTP BASIC, are well documented in
   [RFC7617], therefore implementers are encouraged to prefer stronger
   authentication methods.  Designating the specific methods of
   authentication and authorization are out-of-scope for the delivery of
   SET tokens, however this information is provided as a resource to
   implementers.

5.  Privacy Considerations

   If a SET needs to be retained for audit purposes, JWS MAY be used to
   provide verification of its authenticity.

   Event transmitters SHOULD attempt to filter SETs issued so that the
   content is targeted to the specific business and protocol needs of
   receivers.

   When sharing personally identifiable information or information that
   is otherwise considered confidential to affected users, event




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   transmitters and receivers MUST have the appropriate legal agreements
   and user consent or terms of service in place.

   The propagation of subject identifiers can be perceived as personally
   identifiable information.  Where possible, event transmitters and
   receivers SHOULD devise approaches that prevent propagation -- for
   example, the passing of a hash value that requires the subscriber to
   already know the subject.

6.  IANA Considerations

   There are no IANA considerations.

7.  References

7.1.  Normative References

   [I-D.ietf-secevent-token]
              Hunt, P., Jones, M., Denniss, W., and M. Ansari, "Security
              Event Token (SET)", draft-ietf-secevent-token-07 (work in
              progress), March 2018.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <https://www.rfc-editor.org/info/rfc3986>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [RFC5988]  Nottingham, M., "Web Linking", RFC 5988,
              DOI 10.17487/RFC5988, October 2010,
              <https://www.rfc-editor.org/info/rfc5988>.

   [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, DOI 10.17487/RFC6125, March
              2011, <https://www.rfc-editor.org/info/rfc6125>.




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   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <https://www.rfc-editor.org/info/rfc7159>.

   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
              DOI 10.17487/RFC7231, June 2014,
              <https://www.rfc-editor.org/info/rfc7231>.

   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
              <https://www.rfc-editor.org/info/rfc7519>.

   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <https://www.rfc-editor.org/info/rfc7525>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

7.2.  Informative References

   [openid-connect-core]
              NRI, "OpenID Connect Core 1.0", Nov 2014.

   [POSIX.1]  Institute of Electrical and Electronics Engineers, "The
              Open Group Base Specifications Issue 7", IEEE Std 1003.1,
              2013 Edition, 2013.

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
              <https://www.rfc-editor.org/info/rfc3339>.

   [RFC6202]  Loreto, S., Saint-Andre, P., Salsano, S., and G. Wilkins,
              "Known Issues and Best Practices for the Use of Long
              Polling and Streaming in Bidirectional HTTP", RFC 6202,
              DOI 10.17487/RFC6202, April 2011,
              <https://www.rfc-editor.org/info/rfc6202>.

   [RFC6749]  Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
              RFC 6749, DOI 10.17487/RFC6749, October 2012,
              <https://www.rfc-editor.org/info/rfc6749>.






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   [RFC6750]  Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
              Framework: Bearer Token Usage", RFC 6750,
              DOI 10.17487/RFC6750, October 2012,
              <https://www.rfc-editor.org/info/rfc6750>.

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <https://www.rfc-editor.org/info/rfc7230>.

   [RFC7235]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Authentication", RFC 7235,
              DOI 10.17487/RFC7235, June 2014,
              <https://www.rfc-editor.org/info/rfc7235>.

   [RFC7515]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
              2015, <https://www.rfc-editor.org/info/rfc7515>.

   [RFC7516]  Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
              RFC 7516, DOI 10.17487/RFC7516, May 2015,
              <https://www.rfc-editor.org/info/rfc7516>.

   [RFC7521]  Campbell, B., Mortimore, C., Jones, M., and Y. Goland,
              "Assertion Framework for OAuth 2.0 Client Authentication
              and Authorization Grants", RFC 7521, DOI 10.17487/RFC7521,
              May 2015, <https://www.rfc-editor.org/info/rfc7521>.

   [RFC7617]  Reschke, J., "The 'Basic' HTTP Authentication Scheme",
              RFC 7617, DOI 10.17487/RFC7617, September 2015,
              <https://www.rfc-editor.org/info/rfc7617>.

   [saml-core-2.0]
              Internet2, "Assertions and Protocols for the OASIS
              Security Assertion Markup Language (SAML) V2.0", March
              2005.

Appendix A.  Acknowledgments

   The editor would like to thank the participants in the the SECEVENTS
   working group for their support of this specification.

   This specification is based on and ideally replaces draft-ietf-
   secevent-delivery, and we thank its contributors Annabelle Backman,
   Marius Scurtescu, and Morteza Ansari.






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Appendix B.  Change Log

   Draft 00 - PH - Original

Authors' Addresses

   Phil Hunt (editor)
   Oracle Corporation

   Email: phil.hunt@yahoo.com


   Anthony Nadalin
   Microsoft

   Email: tonynad@microsoft.com



































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