draft-ietf-secevent-http-poll.txt

Network Working Group                                    A. Backman, Ed.
Internet-Draft                                                    Amazon
Intended status: Standards Track                           M. Jones, Ed.
Expires: October 11, 2018                                      Microsoft
                                                            P. Hunt, Ed.
                                                                  Oracle
                                                            M. Scurtescu
                                                                  Google
                                                               M. Ansari
                                                                   Cisco
                                                              A. Nadalin
                                                               Microsoft
                                                           April 9, 2018


                Poll-Based SET Token Delivery Using HTTP
                    draft-ietf-secevent-http-poll-00

Abstract

   This specification defines how a series of security event tokens
   (SETs) may be delivered to a previously registered receiver using
   HTTP POST over TLS initiated as a poll by the receiver.  The
   specification also defines how delivery can be assured subject to the
   SET Token Receiver's need for assurance.

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 October 11, 2018.

Copyright Notice

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




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   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.

Table of Contents

   1.  Introduction and Overview . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
     1.2.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  SET Event Stream Protocol . . . . . . . . . . . . . . . . . .   4
     2.1.  Event Delivery Process  . . . . . . . . . . . . . . . . .   4
     2.2.  Polling Delivery using HTTP . . . . . . . . . . . . . . .   5
       2.2.1.  Polling HTTP Request Attributes . . . . . . . . . . .   6
       2.2.2.  Polling HTTP Response Attributes  . . . . . . . . . .   7
       2.2.3.  Poll Request  . . . . . . . . . . . . . . . . . . . .   7
       2.2.4.  Poll Response . . . . . . . . . . . . . . . . . . . .  11
     2.3.  Error Response Handling . . . . . . . . . . . . . . . . .  13
   3.  Authentication and Authorization  . . . . . . . . . . . . . .  14
     3.1.  Use of Tokens as Authorizations . . . . . . . . . . . . .  15
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
     4.1.  Authentication Using Signed SETs  . . . . . . . . . . . .  15
     4.2.  HTTP Considerations . . . . . . . . . . . . . . . . . . .  15
     4.3.  TLS Support Considerations  . . . . . . . . . . . . . . .  16
     4.4.  Authorization Token Considerations  . . . . . . . . . . .  16
       4.4.1.  Bearer Token Considerations . . . . . . . . . . . . .  16
   5.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  17
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  18
   Appendix A.  Other Streaming Specifications . . . . . . . . . . .  20
   Appendix B.  Acknowledgments  . . . . . . . . . . . . . . . . . .  21
   Appendix C.  Change Log . . . . . . . . . . . . . . . . . . . . .  21
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22

1.  Introduction and Overview

   This specification defines how a stream of SETs (see
   [I-D.ietf-secevent-token]) can be transmitted to a previously
   registered Event Receiver using HTTP [RFC7231] over TLS.  The
   specification defines a method to poll for SETs using HTTP POST.




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   This specification defines a method of SET delivery in what is known
   as Event Streams.

   This specification does not define the method by which Event Streams
   are defined, provisioned, managed, monitored, and configured and is
   out of scope of this specification.
   [[This work is TBD by the SECEVENTS WG]]

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.

1.2.  Definitions

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

   The following definitions are defined for Security Event
   distribution:

   Event Transmitter
      A service provider that delivers SETs to other providers known as
      Event Receivers.  An Event Transmitter is responsible for offering
      a service that allows the Event Receiver to check the Event Stream
      configuration and status known as the "Control Plane".

   Event Receiver
      A service provider that registers to receive SETs from an Event
      Transmitter and provides an endpoint to receive SETs via HTTP
      POST.  Event Receivers can check current Event Stream
      configuration and status by accessing the Event Transmitters
      "Control Plane".

   Event Stream




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      An Event Stream is a defined location, distribution method and
      whereby an Event Transmitter and Event Receiver exchange a pre-
      defined family of SETs.  A Stream is assumed to have configuration
      data such as HTTP endpoints, timeouts, public key sets for signing
      and encryption, and Event Families.

   Subject
      The security subject around which a security event has occurred.
      For example, a security subject might per a user, a person, an
      email address, a service provider entity, an IP address, an OAuth
      Client, a mobile device, or any identifiable thing referenced in
      security and authorization systems.

   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.

2.  SET Event Stream Protocol

   An Event Stream represents the communication channel over which a
   series of SETs are delivered to a configured Event Receiver.

2.1.  Event Delivery Process

   When an Event occurs, the Event Transmitter constructs a SET token
   [I-D.ietf-secevent-token] that describes the Event.  The Event
   Transmitter determines the Event Streams over which the SET should be
   distributed to.

   How SETs are defined and the process by which Events are identified
   for Event Receivers is out-of-scope of this specification.

   When a SET is available for an Event Receiver, the Event Transmitter
   attempts to deliver the SET based on the Event Receiver's registered
   delivery mechanism:

   o  The Event Transmitter queues up the SET in a buffer so that an
      Event Receiver MAY poll for SETs using HTTP/1.1 POST.




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   o  Or, the Event Transmitter delivers the Event through a different
      method not defined by this specification.

   In Poll-Based SET Token Delivery Using HTTP, multiple SETs are
   delivered in a JSON document [RFC7159] to an Event Receiver in
   response to an HTTP POST request to the Event Transmitter.  Then in a
   following request, the Event Receiver acknowledges received SETs and
   MAY poll for more.  All requests and responses are JSON documents and
   use a "Content-Type" of "application/json" as described in
   Section 2.2.

   After successful (acknowledged) SET delivery, Event Transmitters
   SHOULD NOT be required to maintain or record SETs for recovery.  Once
   a SET is acknowledged, the Event Receiver SHALL be responsible for
   retention and recovery.

   Transmitted SETs SHOULD be self-validating (e.g. signed) if there is
   a requirement to verify they were issued by the Event Transmitter at
   a later date when de-coupled from the original delivery where
   authenticity could be checked via the HTTP or TLS mutual
   authentication.

   Upon receiving a SET, the Event Receiver reads the SET and validates
   it.  The Event Receiver MUST acknowledge receipt to the Event
   Transmitter, using the defined acknowledgement or error method
   depending on the method of transfer.

   The Event Receiver SHALL NOT use the Event acknowledgement mechanism
   to report Event errors other than relating to the parsing and
   validation of the SET.

2.2.  Polling Delivery using HTTP

   This method allows an Event Receiver to use HTTP POST (Section 4.3.3
   [RFC7231]) to acknowledge SETs and to check for and receive zero or
   more SETs.  Requests MAY be made at a periodic interval (short
   polling) or requests MAY wait pending availability of new SETs using
   long polling (see Section 2 [RFC6202]).

   The delivery of SETs in this method is facilitated by HTTP POST
   requests initiated by the Event Receiver in which:

   o  The Event Receiver makes a request for available SETs using an
      HTTP POST to a pre-arranged endpoint provided by the Event
      Transmitter.  Or,

   o  After validating previously received SETs, the Event Receiver
      initiates another poll request using HTTP POST that includes



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      acknowledgement of previous SETs, and waits for the next batch of
      SETs.

   The purpose of the "acknowledgement" is to inform the Event
   Transmitter that has successfully been delivered and attempts to re-
   deliver are no longer required.  Before acknowledgement, Event
   Receivers SHOULD ensure received SETs have been validated and
   retained in a manner appropriate to the receiver's retention
   requirements.  The level and method of retention of SETs by Event
   Receivers is out-of-scope of this specification.

2.2.1.  Polling HTTP Request Attributes

   When initiating a poll request, the Event Receiver constructs a JSON
   document that consists of polling request parameters and SET
   acknowledgement parameters in the form of JSON attributes.

   The request payloads are delivered in one of two forms as described
   in Section 2.2.3 and Section 2.2.4

   When making a request, the HTTP header "Content-Type" is set to
   "application/json".

   The following JSON Attributes are used in a polling request:

   Request Processing Parameters

      maxEvents
         an OPTIONAL JSON integer value indicating the maximum number of
         unacknowledged SETs that SHOULD be returned.  If more than the
         maximum number of SETs are available, the oldest SETs available
         SHOULD be returned first.  A value of "0" MAY be used by Event
         Receivers that would like to perform an acknowledge only
         request.  This enables the Receiver to use separate HTTP
         requests for acknowledgement and reception of SETs.  When zero
         returned events is requested, the value of the attribute
         "returnImmediately" SHALL be ignored as an immediate response
         is expected.

      returnImmediately
         An OPTIONAL JSON boolean value that indicates the Event
         Transmitter SHOULD return an immediate response even if no
         results are available (short polling).  The default value is
         "false" indicates the request is to be treated as an HTTP Long
         Poll (see Section 2 [RFC6202]).  The time out for the request
         is part of the Stream configuration which is out of scope of
         this specification.




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   SET Acknowledgment Parameters

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

      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.

2.2.2.  Polling HTTP Response Attributes

   In response to a poll request, the Event Transmitter checks for
   available SET events and responds with a JSON document containing the
   following JSON attributes:

   sets
      A JSON object that contains zero 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 outstanding SETs
      to be transmitted, the JSON object SHALL be empty.

   moreAvailable
      A JSON boolean value that indicates if more unacknowledged SETs
      are available to be returned.

   When making a response, the HTTP header "Content-Type" is set to
   "application/json".

2.2.3.  Poll Request

   The Event Receiver performs an HTTP POST (see Section 4.3.4
   [RFC7231]) to a pre-arranged polling endpoint URI to check for SETs
   that are available.  Because the Event Receiver has no prior SETs to
   acknowledge, the "ack" and "errs" request parameters are omitted.

   If after a period of time, negotiated between the Event Transmitter
   and Receiver, an Event Transmitter MAY re-issue SETs it has
   previously delivered.  The Event Receiver SHOULD accept repeat SETs
   and acknowledge the SETs regardless of whether the Receiver believes



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   it has already acknowledged the SETs previously.  An Event
   Transmitter MAY limit the number of times it attempts to deliver a
   SET.  Upon abandoning delivery of a SET, the Event Transmitter SHOULD
   have a method to notify the Event Receiver of the loss such as
   through a status service (not defined by this specification).

   If the Event Receiver has received SETs from the Event Transmitter,
   the Event Receiver SHOULD parse and validate received SETs to meet
   its own requirements and SHOULD acknowledge receipt in a timely (e.g.
   minutes) fashion so that the Event Transmitter may mark the SETs as
   received.  Event Receivers SHOULD acknowledge receipt before taking
   any local actions based on the SETs to avoid unnecessary delay in
   acknowledgement where possible.

   Poll requests have three variations:

   Poll Only
      In which an Event Receiver asks for the next set of Events where
      no previous SET deliveries are acknowledged (such as in the
      initial poll request).

   Acknowledge Only
      In which an Event Receiver sets the "maxEvents" attribute to "0"
      along with "ack" and "err" attributes indicating the Event
      Receiver is acknowledging previously received SETs and does not
      want to receive any new SETs in response to the request.

   Combined Acknowledge and Poll
      In which an Event Receiver is both acknowledging previously
      received SETs using the "ack" and "err" attributes and will wait
      for the next group of SETs in the Event Transmitters response.

2.2.3.1.  Poll Only Request

   In the case where no SETs were received in a previous poll (see
   Figure 7), the Event Receiver simply polls without acknowledgement
   parameters ("sets" and "setErrs").

   The following is an example request made by an Event Receiver that
   has no outstanding SETs to acknowledge and is polling for available
   SETs.










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   The following is a non-normative example poll request to the
   endpoint: "https://nofity.exampleidp.com/Events".

   POST /Events  HTTP/1.1

   Host: notify.exampleidp.com
   Authorization: Bearer h480djs93hd8
   Accept: application/json

   {
    "returnImmediately":true
   }

                  Figure 1: Example Initial Poll Request

   An Event Receiver MAY poll with no parameters at all by passing an
   empty JSON object.

   The following is a non-normative example default poll request to the
   endpoint: "https://nofity.exampleidp.com/Events".

   POST /Events  HTTP/1.1

   Host: notify.exampleidp.com
   Authorization: Bearer h480djs93hd8
   Accept: application/json

   {}

                  Figure 2: Example Default Poll Request

2.2.3.2.  Acknowledge Only Request

   In this variation, the Event Receiver acknowledges previously
   received SETs and indicates it does not want to receive SETs in
   response by setting the "maxEvents" attribute to "0".

   This variation is typically used when an Event Receiver needs to
   acknowledge received SETs independently (e.g. on separate threads)
   from the process of receiving SETs.











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   The following is a non-normative example poll with acknowledgement of
   SETs received (for example as shown in Figure 6).

   POST /Events  HTTP/1.1

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

   {
     "ack":[
       "4d3559ec67504aaba65d40b0363faad8",
       "3d0c3cf797584bd193bd0fb1bd4e7d30"
     ],
     "maxEvents":0
   }

                 Figure 3: Example Acknowledge Only equest

2.2.3.3.  Poll with Acknowledgement

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

   The following is a non-normative example poll with acknowledgement of
   SETs received in Figure 6.

   POST /Events  HTTP/1.1

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

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

         Figure 4: Example Poll With Acknowledgement and No Errors






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   In the above acknowledgement, the Event Receiver has acknowledged
   receipt of two SETs and has indicated it wants to wait until the next
   SET is available.

2.2.3.4.  Poll with Acknowledgement and Errors

   In the case where errors were detected in previously delivered SETs,
   the Event Receiver MAY use the "setErrs" attribute to indicate errors
   in the following poll request.

   The following is a non-normative example of a response acknowledging
   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/json
   Authorization: Bearer h480djs93hd8

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

             Figure 5: Example Poll Acknowledgement With Error

2.2.4.  Poll Response

   In response to a poll request, the service provider MAY respond
   immediately if SETs are available to be delivered.  If no SETs are
   available at the time of the request, the Event Transmitter SHALL
   delay responding until a SET is available unless the poll request
   parameter "returnImmediately" is "true".

   As described in Section 2.2.2 a JSON document is returned containing
   a number of attributes including "sets" which SHALL contain zero or
   more SETs.







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   The following is a non-normative example response to the request
   shown Section 2.2.3.  This example shows two SETs are returned.

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

  {
  "sets":{
    "4d3559ec67504aaba65d40b0363faad8":
     "eyJhbGciOiJub25lIn0.
     eyJqdGkiOiI0ZDM1NTllYzY3NTA0YWFiYTY1ZDQwYjAzNjNmYWFkOCIsImlhdCI6MTQ
     1ODQ5NjQwNCwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbIm
     h0dHBzOi8vc2NpbS5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M
     2I3NzU0IiwiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIx
     ZDA4NjQxZDc2NzZlZTciXSwiZXZlbnRzIjp7InVybjppZXRmOnBhcmFtczpzY2ltOmV
     2ZW50OmNyZWF0ZSI6eyJyZWYiOiJodHRwczovL3NjaW0uZXhhbXBsZS5jb20vVXNlcn
     MvNDRmNjE0MmRmOTZiZDZhYjYxZTc1MjFkOSIsImF0dHJpYnV0ZXMiOlsiaWQiLCJuY
     W1lIiwidXNlck5hbWUiLCJwYXNzd29yZCIsImVtYWlscyJdfX19.",
    "3d0c3cf797584bd193bd0fb1bd4e7d30":
     "eyJhbGciOiJub25lIn0.
     eyJqdGkiOiIzZDBjM2NmNzk3NTg0YmQxOTNiZDBmYjFiZDRlN2QzMCIsImlhdCI6MTQ
     1ODQ5NjAyNSwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbIm
     h0dHBzOi8vamh1Yi5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M
     2I3NzU0IiwiaHR0cHM6Ly9qaHViLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIx
     ZDA4NjQxZDc2NzZlZTciXSwic3ViIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL1V
     zZXJzLzQ0ZjYxNDJkZjk2YmQ2YWI2MWU3NTIxZDkiLCJldmVudHMiOnsidXJuOmlldG
     Y6cGFyYW1zOnNjaW06ZXZlbnQ6cGFzc3dvcmRSZXNldCI6eyJpZCI6IjQ0ZjYxNDJkZ
     jk2YmQ2YWI2MWU3NTIxZDkifSwiaHR0cHM6Ly9leGFtcGxlLmNvbS9zY2ltL2V2ZW50
     L3Bhc3N3b3JkUmVzZXRFeHQiOnsicmVzZXRBdHRlbXB0cyI6NX19fQ."
   }
  }

                      Figure 6: Example Poll Response

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













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   The following is a non-normative example response to the request
   shown Section 2.2.3 showing no new SETs or unacknowledged SETs are
   available.

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

   {
    "sets":{ }
   }

                  Figure 7: Example No SETs Poll Response

   Upon receiving the JSON document (e.g. as shown in Figure 6), the
   Event Receiver parses and verifies the received SETs and notifies the
   Event Transmitter via the next poll request to the Event Transmitter
   as described in Section 2.2.3.3 or Section 2.2.3.4.

2.3.  Error Response Handling

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

   +-----------+-------------------------------------------------------+
   | 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.               |
   | dup       | A duplicate SET was received and has been ignored.    |
   +-----------+-------------------------------------------------------+

                            Table 1: SET Errors

   An error response SHALL include a JSON object which provides details
   about the error.  The JSON object includes the JSON attributes:

   err



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      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 a batch of SETs, the above JSON is included
   as part of the "setErrs" attribute as defined in Section 2.2.2 and
   Section 2.2.3.4

3.  Authentication and Authorization

   The SET delivery method described in this specification is based upon
   HTTP and depends 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
      Event delivery endpoints MAY request TLS mutual client
      authentication.  See Section 7.3 [RFC5246].

   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).

   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.




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   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
   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 the Event Receiver 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.



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   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 Transmitters and Event 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 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.



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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 specialize Event Streams so that
   the content is targeted to the specific business and protocol needs
   of subscribers.

   When sharing personally identifiable information or information that
   is otherwise considered confidential to affected users, Event
   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., Denniss, W., Ansari, M., and M. Jones, "Security
              Event Token (SET)", draft-ietf-secevent-token-00 (work in
              progress), January 2017.

   [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>.




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   [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>.

   [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>.

   [RFC7517]  Jones, M., "JSON Web Key (JWK)", RFC 7517,
              DOI 10.17487/RFC7517, May 2015, <https://www.rfc-
              editor.org/info/rfc7517>.

   [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.





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   [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>.

   [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>.






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

Appendix A.  Other Streaming Specifications

   [[EDITORS NOTE: This section to be removed prior to publication]]

   The following pub/sub, queuing, streaming systems were reviewed as
   possible solutions or as input to the current draft:

   XMPP Events

   The WG considered the XMPP events ands its ability to provide a
   single messaging solution without the need for both polling and push
   modes.  The feeling was the size and methodology of XMPP was to far
   apart from the current capabilities of the SECEVENTs community which
   focuses in on HTTP based service delivery and authorization.

   Amazon Simple Notification Service

   Simple Notification Service, is a pub/sub messaging product from AWS.
   SNS supports a variety of subscriber types: HTTP/HTTPS endpoints, AWS
   Lambda functions, email addresses (as JSON or plain text), phone
   numbers (via SMS), and AWS SQS standard queues.  It doesn't directly
   support pull, but subscribers can get the pull model by creating an
   SQS queue and subscribing it to the topic.  Note that this puts the
   cost of pull support back onto the subscriber, just as it is in the
   push model.  It is not clear that one way is strictly better than the
   other; larger, sophisticated developers may be happy to own message
   persistence so they can have their own internal delivery guarantees.
   The long tail of OIDC clients may not care about that, or may fail to
   get it right.  Regardless, I think we can learn something from the
   Delivery Policies supported by SNS, as well as the delivery controls
   that SQS offers (e.g.  Visibility Timeout, Dead-Letter Queues).  I'm
   not suggesting that we need all of these things in the spec, but they
   give an idea of what features people have found useful.

   Other information:

   o  API Reference:
      http://docs.aws.amazon.com/AWSSimpleQueueService/latest/
      APIReference/Welcome.html

   o  Visibility Timeouts:
      http://docs.aws.amazon.com/AWSSimpleQueueService/latest/
      SQSDeveloperGuide/sqs-visibility-timeout.html



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   Apache Kafka

   Apache Kafka is an Apache open source project based upon TCP for
   distributed streaming.  It prescribes some interesting general
   purpose features that seem to extend far beyond the simpler streaming
   model SECEVENTs is after.  A comment from MS has been that Kafka does
   an acknowledge with poll combination event which seems to be a
   performance advantage.  See: https://kafka.apache.org/intro

   Google Pub/Sub

   Google Pub Sub system favours a model whereby polling and
   acknowledgement of events is done as separate endpoints as separate
   functions.

   Information:

   o  Cloud Overview - https://cloud.google.com/pubsub/

   o  Subscriber Overview - https://cloud.google.com/pubsub/docs/
      subscriber

   o  Subscriber Pull(poll) - https://cloud.google.com/pubsub/docs/pull

Appendix B.  Acknowledgments

   The editors would like to thanks the members of the SCIM WG which
   began discussions of provisioning events starting with: draft-hunt-
   scim-notify-00 in 2015.

   The editors would like to thank the authors of draft-ietf-secevent-
   delivery-02, on which this draft is based.

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

Appendix C.  Change Log

   Draft 00 - AB - Based on draft-ietf-secevent-delivery-02 with the
   following additions:

   o  Renamed to "Poll-Based SET Token Delivery Using HTTP"

   o  Removed references to the HTTP Push delivery method.







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Authors' Addresses

   Annabelle Backman (editor)
   Amazon

   Email: richanna@amazon.com


   Michael B. Jones (editor)
   Microsoft

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


   Phil Hunt (editor)
   Oracle Corporation

   Email: phil.hunt@yahoo.com


   Marius Scurtescu
   Google

   Email: mscurtescu@google.com


   Morteza Ansari
   Cisco

   Email: morteza.ansari@cisco.com


   Anthony Nadalin
   Microsoft

   Email: tonynad@microsoft.com














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