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<rfc xmlns:xi="http://www.w3.org/2001/XInclude" category="std"
     docName="draft-ietf-secevent-http-push-14" ipr="trust200902"> ipr="trust200902" obsoletes=""
     updates="" submissionType="IETF" xml:lang="en" tocInclude="true"
     tocDepth="3" symRefs="true" sortRefs="true" version="3" consensus="yes"
     number="8935">

  <front>
    <title abbrev="draft-ietf-secevent-http-push">Push-Based abbrev="Push-Based SET Using HTTP">Push-Based Security Event Token (SET) Delivery Using HTTP</title>
    <seriesInfo name="RFC" value="8935"/>
    <author fullname="Annabelle Backman" initials="A." surname="Backman" role="editor">
            <organization abbrev="Amazon">Amazon</organization>
      <organization>Amazon</organization>
      <address>
        <email>richanna@amazon.com</email>
      </address>
    </author>
    <author fullname="Michael B. Jones" initials="M." surname="Jones" role="editor">
            <organization abbrev="Microsoft">Microsoft</organization>
      <organization>Microsoft</organization>
      <address>
        <email>mbj@microsoft.com</email>
        <uri>https://self-issued.info/</uri>
      </address>
    </author>
    <author fullname="Marius Scurtescu" initials="M.S." initials="M." surname="Scurtescu">
            <organization abbrev="Coinbase">Coinbase</organization>
      <organization>Coinbase</organization>
      <address>
        <email>marius.scurtescu@coinbase.com</email>
      </address>
    </author>
    <author fullname="Morteza Ansari" initials="M." surname="Ansari">
            <organization abbrev="Cisco">Cisco</organization>
      <organization>Independent</organization>
      <address>
                <email>morteza.ansari@cisco.com</email>
        <email>morteza@sharppics.com</email>
      </address>
    </author>
    <author fullname="Anthony Nadalin" initials="A." surname="Nadalin">
            <organization abbrev="Microsoft">Microsoft</organization>
      <organization>Independent</organization>
      <address>
                <email>tonynad@microsoft.com</email>
        <email>nadalin@prodigy.net</email>
      </address>
    </author>
    <date year="2020" month="June" day="26" /> month="November"/>
    <area>Security</area>
    <workgroup>Security Events Working Group</workgroup>
        <keyword>Internet-Draft</keyword>

<keyword>JSON Web Token</keyword>
<keyword>JWT</keyword>
<keyword>Security Event Token</keyword>
<keyword>SET</keyword>
<keyword>Delivery</keyword>
<keyword>JavaScript Object Notation</keyword>
<keyword>JSON</keyword>

    <abstract>
      <t>
        This specification defines how a Security Event Token (SET) can be
        delivered to an intended recipient using HTTP POST over TLS.  The SET
        is transmitted in the body of an HTTP POST request to an endpoint
        operated by the recipient, and the recipient indicates successful or
        failed transmission via the HTTP response.
      </t>
    </abstract>
  </front>
  <middle>

    <section anchor="intro" title="Introduction toc="default" numbered="true">
      <name>Introduction and Overview" toc="default"> Overview</name>
      <t>
                This specification defines a mechanism by which a transmitter of a
                <xref target="RFC8417">Security target="RFC8417" format="default">Security Event Token (SET)</xref> can deliver
                the SET to an intended SET Recipient via <xref target="RFC7231">HTTP target="RFC7231" format="default">HTTP POST</xref>
		over TLS.
		This is an alternative SET delivery method to the one defined in
		<xref target="I-D.ietf-secevent-http-poll"/>. target="RFC8936" format="default"/>.
      </t>
      <t>
                Push-based SET delivery over HTTP POST is intended for scenarios where all of
                the following apply:
                <list style="symbols">
                    <t>The
      </t>
      <ul spacing="normal">
        <li>The transmitter of the SET is capable of making outbound HTTP requests.</t>
                    <t> requests.</li>
        <li>
                        The recipient is capable of hosting a TLS-enabled HTTP endpoint that is accessible
                        to the transmitter.
                    </t>
                    <t>
                    </li>
        <li>
		      The transmitter and recipient are willing to exchange data with one another.
		    </t>
                </list>
		    </li>
      </ul>
      <t>
		In some scenarios, either push-based or poll-based delivery could be used,
		and in others, only one of them would be applicable.
      </t>
      <t>
                A mechanism for exchanging configuration metadata such as endpoint URLs,
                cryptographic keys,
		and possible implementation constraints such as buffer size limitations
		between the transmitter and recipient is
                out of scope for this specification. How SETs are defined and the process
                by which security events are identified for SET Recipients are specified
                in <xref target="RFC8417"/>. target="RFC8417" format="default"/>.
      </t>
      <section anchor="notat" title="Notational Conventions" toc="default">
                <t>The toc="default" numbered="true">
        <name>Notational Conventions</name>
        <t>
    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
                    NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
                    "MAY", "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
    "<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
    NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
    "<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
    "<bcp14>MAY</bcp14>", and "OPTIONAL" "<bcp14>OPTIONAL</bcp14>" in this document are
    to be interpreted as described in BCP 14 BCP&nbsp;14 <xref target="RFC2119"/>
    <xref target="RFC8174"/> when, and only when, they appear in all capitals,
    as shown here.
        </t>
        <t>
	 Throughout this document, all figures may contain spaces and extra
	 line wrapping for readability and due to space limitations.
        </t>
      </section>
      <section anchor="defs" title="Definitions" toc="default"> toc="default" numbered="true">
        <name>Definitions</name>
        <t>
                    This specification utilizes the following terms defined in <xref target="RFC8417"/>: target="RFC8417" format="default"/>:
                    "Security Event Token (SET)", "SET Issuer", "SET Recipient", and "Event Payload",
                    as well as the term defined below:
        </t>
                <t>
                    <list style="hanging">
                        <t hangText="SET Transmitter">

        <dl newline="false" spacing="normal">
          <dt>SET Transmitter:</dt>
          <dd>
          An entity that delivers SETs in its possession to one or more SET
          Recipients.
                        </t>
                    </list>
                </t>
          </dd>
        </dl>

      </section>

    </section>
    <section anchor="Delivery" title="SET Delivery"> numbered="true" toc="default">
      <name>SET Delivery</name>
      <t>
                To deliver a SET to a given SET Recipient, the SET Transmitter
                makes a SET transmission request Transmission Request to the SET Recipient, with the SET
                itself contained within the request. The SET Recipient replies to
                this request with a response either acknowledging successful
                transmission of the SET or indicating that an error occurred
                while receiving, parsing, and/or validating the SET.

      </t>
      <t>
                Upon receipt of a SET, the SET Recipient SHALL <bcp14>SHALL</bcp14> validate that all of
                the following are true:
                <list style="symbols">
                    <t>The
      </t>
      <ul spacing="normal">
        <li>The SET Recipient can parse the SET.</t>
                    <t> SET.</li>
        <li>
                        The SET is authentic (i.e., it was issued by the issuer
                        specified within the SET,
			and if signed, was signed by a key belonging to the issuer).
                    </t>
                    <t>
                    </li>
        <li>
                        The SET Recipient is identified as an intended audience of
                        the SET.
                    </t>
                    <t>
                    </li>
        <li>
                        The SET Issuer is recognized as an issuer that the SET Recipient
                        is willing to receive SETs from (e.g., the issuer is listed as allowed
                        by the SET Recipient).
                    </t>
                    <t>
                    </li>
        <li>
		      The SET Recipient is willing to accept this SET from this SET Transmitter
		      (e.g., the SET Transmitter is expected to send SETs
		      with the issuer and subject of the SET in question).
                    </t>
                </list>
            </t>
                    </li>
      </ul>

      <t>
                The mechanisms by which the SET Recipient performs this validation
                are out of scope for this document. SET parsing, issuer identification,
		and audience identification are defined in <xref target="RFC8417"/>. target="RFC8417" format="default"/>.
                The mechanism for validating the authenticity of a SET is deployment
                specific,
                specific and may vary depending on the authentication mechanisms in
                use,
                use and whether the SET is signed and/or encrypted (See <xref target="aa"/>). target="aa" format="default"/>).
      </t>
      <t>
                SET Transmitters MAY <bcp14>MAY</bcp14> transmit SETs issued by another entity. The SET
                Recipient may accept or reject (i.e., return an error response such as
                <spanx style="verb">access_denied</spanx>)
                <tt>access_denied</tt>) a SET at its own discretion.
      </t>
      <t>
                The SET Recipient persists the SET in a way that
                is sufficient to meet the SET Recipient's own reliability requirements.
		The level and method of retention of SETs
		by SET Recipients is out of scope of this specification.
                Once the SET has been validated and persisted, the SET Recipient SHOULD <bcp14>SHOULD</bcp14>
                immediately return a response indicating that the SET was successfully
                delivered. The SET Recipient SHOULD NOT <bcp14>SHOULD NOT</bcp14> perform further processing of the SET
		beyond the required validation steps prior to sending this response.
                Any additional steps SHOULD <bcp14>SHOULD</bcp14> be executed asynchronously from delivery
		to minimize the time the SET Transmitter is waiting for a response.
      </t>
      <t>
                The SET Transmitter MAY <bcp14>MAY</bcp14> transmit the same SET to the SET Recipient multiple
                times, regardless of the response from the SET Recipient. The SET Recipient
                MUST
                <bcp14>MUST</bcp14> respond as it would if the SET had not been previously received by the
                SET Recipient. The SET Recipient MUST NOT <bcp14>MUST NOT</bcp14> expect or depend on a SET Transmitter
                to re-transmit retransmit a SET or otherwise make a SET available to the SET Recipient
                once the SET Recipient acknowledges that it was received successfully.
      </t>
      <t>
                The SET Transmitter should not re-transmit retransmit a SET unless the SET Transmitter
                suspects that previous transmissions may have failed due to potentially
                recoverable errors (such as network outage or temporary service interruption at
                either the SET Transmitter or SET Recipient). In all other cases, the SET
                Transmitter SHOULD NOT re-transmit <bcp14>SHOULD NOT</bcp14> retransmit a SET. The SET
                Transmitter SHOULD <bcp14>SHOULD</bcp14> delay retransmission for an appropriate amount of time
                to avoid overwhelming the SET Recipient (see <xref target="reliability"/>). target="reliability" format="default"/>).
      </t>
      <section anchor="httpPost" title="Transmitting numbered="true" toc="default">
        <name>Transmitting a SET"> SET</name>
        <t>
                    To transmit a SET to a SET Recipient, the SET Transmitter makes
                    an HTTP POST request to a TLS-enabled HTTP endpoint provided by the SET Recipient.  The
                    <spanx style="verb">Content-Type</spanx>
                    <tt>Content-Type</tt> header field of this request MUST <bcp14>MUST</bcp14>
                    be <spanx style="verb">application/secevent+jwt</spanx> <tt>application/secevent+jwt</tt> as defined in
                    Sections 2.3 <xref target="RFC8417"
		    sectionFormat="bare" section="2.3"/> and 7.2 <xref target="RFC8417"
		    sectionFormat="bare" section="7.2"/> of <xref target="RFC8417"/>, target="RFC8417"
		    sectionFormat="bare"/>, and the
                    <spanx style="verb">Accept</spanx>
                    <tt>Accept</tt> header field MUST <bcp14>MUST</bcp14> be <spanx style="verb">application/json</spanx>. <tt>application/json</tt>.  The
                    request body MUST <bcp14>MUST</bcp14> consist of the SET itself, represented as a
                    <xref target="RFC7519">JWT</xref>. target="RFC7519" format="default">JSON Web Token (JWT)</xref>.
        </t>
        <t>
                    The SET Transmitter MAY <bcp14>MAY</bcp14> include in the request an <spanx style="verb">Accept-Language</spanx> <tt>Accept-Language</tt>
                    header field to indicate to the SET Recipient the preferred language(s) in which to
                    receive error messages.
        </t>
        <t>
                    The mechanisms by which the SET Transmitter determines the HTTP endpoint to
                    use when transmitting a SET to a given SET Recipient are not defined by this
                    specification and are deployment specific.
        </t>
                <figure align="left" anchor="postSet" title="Example SET Transmission Request">
                    <preamble>
        <t keepWithNext="true">
                        The following is a non-normative example of a SET transmission request:
                    </preamble>
                    <artwork><![CDATA[ Transmission Request:
        </t>
        <figure anchor="postSet">
          <name>Example SET Transmission Request</name>

          <sourcecode name="" type="http-message"><![CDATA[
  POST /Events HTTP/1.1
  Host: notify.rp.example.com
  Accept: application/json
  Accept-Language: en-US, en;q=0.5
  Content-Type: application/secevent+jwt

  eyJ0eXAiOiJzZWNldmVudCtqd3QiLCJhbGciOiJIUzI1NiJ9Cg
  .
  eyJpc3MiOiJodHRwczovL2lkcC5leGFtcGxlLmNvbS8iLCJqdGkiOiI3NTZFNjk
  3MTc1NjUyMDY5NjQ2NTZFNzQ2OTY2Njk2NTcyIiwiaWF0IjoxNTA4MTg0ODQ1LC
  JhdWQiOiI2MzZDNjk2NTZFNzQ1RjY5NjQiLCJldmVudHMiOnsiaHR0cHM6Ly9zY
  2hlbWFzLm9wZW5pZC5uZXQvc2VjZXZlbnQvcmlzYy9ldmVudC10eXBlL2FjY291
  bnQtZGlzYWJsZWQiOnsic3ViamVjdCI6eyJzdWJqZWN0X3R5cGUiOiJpc3Mtc3V
  iIiwiaXNzIjoiaHR0cHM6Ly9pZHAuZXhhbXBsZS5jb20vIiwic3ViIjoiNzM3NT
  YyNkE2NTYzNzQifSwicmVhc29uIjoiaGlqYWNraW5nIn19fQ
  .
  Y4rXxMD406P2edv00cr9Wf3_XwNtLjB9n-jTqN1_lLc
]]></artwork>
]]></sourcecode>
        </figure>
      </section>
      <section anchor="successResponse" title="Success Response"> numbered="true" toc="default">
        <name>Success Response</name>
        <t>If the SET is determined to be valid, the SET Recipient SHALL <bcp14>SHALL</bcp14>
                    acknowledge successful transmission by responding with HTTP
                    Response Status Code 202 (Accepted) (see Section 6.3.3 of <xref target="RFC7231"/>). target="RFC7231" sectionFormat="of" section="6.3.3"/>).
		    The body of the response MUST <bcp14>MUST</bcp14> be empty.
        </t>

                <figure anchor="goodPostResponse" title="Example Successful Delivery Response">
                    <preamble>The
        <t keepWithNext="true">The following is a non-normative example of a successful
                        receipt of a SET.</preamble>
                    <artwork><![CDATA[ SET.</t>
        <figure anchor="goodPostResponse">
          <name>Example Successful Delivery Response</name>
          <sourcecode name="" type="http-message"><![CDATA[
  HTTP/1.1 202 Accepted
]]></artwork>
]]></sourcecode>
        </figure>
      </section>
      <section anchor="failureResponse" title="Failure Response"> numbered="true" toc="default">
        <name>Failure Response</name>
        <t>In the event of a general HTTP error condition, the SET Recipient
                    responds with the applicable HTTP Status Code, as defined in
                    Section 6 of
                    <xref target="RFC7231"/>.</t> target="RFC7231" sectionFormat="of" section="6"/>.</t>
        <t>
                    When the SET Recipient detects an error parsing,
                    validating, or authenticating a SET transmitted in a SET
                    Transmission Request, the SET Recipient SHALL
                    <bcp14>SHALL</bcp14> respond with an HTTP Response Status
                    Code of 400 (Bad Request).  The
                    <spanx style="verb">Content-Type</spanx> <tt>Content-Type</tt>
                    header field of this response MUST <bcp14>MUST</bcp14> be
                    "application/json",
                    <tt>application/json</tt>, and the body MUST <bcp14>MUST</bcp14> be a
                    UTF-8 encoded <xref target="RFC8259">JSON</xref> target="RFC8259"
                    format="default">JSON</xref> object containing the
                    following name/value pairs:
                    <list style="hanging">
                        <t hangText="err">
        </t>
        <dl newline="false" spacing="normal">
          <dt>err:</dt>
          <dd>
                            A Security Event Token Error Code (see <xref target="error_codes"/>).
                        </t>
                        <t hangText="description"> target="error_codes" format="default"/>).
                        </dd>
          <dt>description:</dt>
          <dd>
                            A UTF-8 string containing a human-readable description of the error
                            that may provide additional diagnostic information. The exact content
                            of this field is implementation specific.
                        </t>
                    </list>
                </t>
                        </dd>
        </dl>
        <t>
                    The response MUST <bcp14>MUST</bcp14> include a <spanx style="verb">Content-Language</spanx>
                    <tt>Content-Language</tt> header field, field whose value
                    indicates the language of the error descriptions included
                    in the response body. If the SET Recipient can provide
                    error descriptions in multiple languages, they SHOULD
                    <bcp14>SHOULD</bcp14> choose the language to use according
                    to the value of the <spanx style="verb">Accept-Language</spanx> <tt>Accept-Language</tt> header field
                    sent by the SET Transmitter in the transmission request,
                    as described in Section 5.3.5
                    of <xref target="RFC7231"/>. target="RFC7231" sectionFormat="of"
                    section="5.3.5"/>. If the SET Transmitter did not send an
                    <spanx style="verb">Accept-Language</spanx>
                    <tt>Accept-Language</tt> header field, or if the SET
                    Recipient does not support any of the languages included
                    in the header field, the SET Recipient MUST <bcp14>MUST</bcp14>
                    respond with messages that are understandable by an
                    English-speaking person, as described in Section 4.5 of <xref target="RFC2277"/>.
                    target="RFC2277" sectionFormat="of" section="4.5"/>.
        </t>

                <figure anchor="errorResponseInvalidKey" title="Example Error Response (invalid_key)">
                    <preamble>The
        <t keepWithNext="true">The following is a non-normative example error response indicating
                        that the key used to encrypt the SET has been revoked.</preamble>
                    <artwork><![CDATA[ revoked.</t>
        <figure anchor="errorResponseInvalidKey">
          <name>Example Error Response (invalid_key)</name>
          <sourcecode name="http-message" type=""><![CDATA[
  HTTP/1.1 400 Bad Request
  Content-Language: en-US
  Content-Type: application/json

  {
    "err": "invalid_key",
    "description": "Key ID 12345 has been revoked."
  }
]]></artwork>
]]></sourcecode>
        </figure>

                <figure anchor="errorResponseExpiredToken" title="Example Error Response (authentication_failed)">
                    <preamble>The
        <t keepWithNext="true">The following is a non-normative example error response indicating
                        that the access token included in the request is expired.</preamble>
                    <artwork><![CDATA[ expired.</t>
        <figure anchor="errorResponseExpiredToken">
          <name>Example Error Response (authentication_failed)</name>
          <sourcecode name="" type="http-message"><![CDATA[
  HTTP/1.1 400 Bad Request
  Content-Language: en-US
  Content-Type: application/json

  {
    "err": "authentication_failed",
    "description": "Access token has expired."
  }
]]></artwork>
]]></sourcecode>
        </figure>

                <figure anchor="errorResponseBadIssuer" title="Example Error Response (access_denied)">
                    <preamble>The
        <t keepWithNext="true">The following is a non-normative example error response indicating
                        that the SET Receiver is not willing to accept SETs issued by the specified
                        issuer from this particular SET Transmitter.</preamble>
                    <artwork><![CDATA[ Transmitter.</t>
        <figure anchor="errorResponseBadIssuer">
          <name>Example Error Response (access_denied)</name>

          <sourcecode name="" type="http-message"><![CDATA[
HTTP/1.1 400 Bad Request
Content-Language: en-US
Content-Type: application/json

{
  "err": "invalid_issuer",
  "description": "Not authorized for issuer https://iss.example.com/." https://iss.example.com/"
}
]]></artwork>
]]></sourcecode>
        </figure>
      </section>
      <section anchor="error_codes" title="Security numbered="true" toc="default">
        <name>Security Event Token Delivery Error Codes"> Codes</name>
        <t>Security Event Token Delivery Error Codes are strings that identify a
                    specific category of error that may occur when parsing or validating a SET.

                    Every Security Event Token Delivery Error Code MUST <bcp14>MUST</bcp14> have a unique name
                    registered in the IANA "Security Event Token Delivery Error Codes"
                    registry established by <xref target="iana_set_errors"/>.</t> target="iana_set_errors" format="default"/>.</t>

        <t>The following table presents the initial set of Error Codes that are registered
                    in the IANA "Security Event Token Delivery Error Codes" registry:</t>
                <texttable
        <table anchor="reqErrors" title="SET Delivery align="center">
          <name>SET Error Codes">
                    <ttcol>Error Code</ttcol><ttcol>Description</ttcol>
                    <c>invalid_request</c><c>The Codes</name>
          <thead>
            <tr>
              <th align="left">Error Code</th>
              <th align="left">Description</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td align="left">invalid_request</td>
              <td align="left">The request body cannot be parsed as a SET, or the
                        Event Payload within the SET does not conform to the event's definition.</c>
                    <c>invalid_key</c><c>One definition.</td>
            </tr>
            <tr>
              <td align="left">invalid_key</td>
              <td align="left">One or more keys used to encrypt or sign the SET is
                        invalid or otherwise unacceptable to the SET Recipient (expired,
                        revoked, failed certificate validation, etc.).</c>
                    <c>invalid_issuer</c><c>The etc.).</td>
            </tr>
            <tr>
              <td align="left">invalid_issuer</td>
              <td align="left">The SET issuer Issuer is invalid for the SET Recipient.</c>
                    <c>invalid_audience</c><c>The Recipient.</td>
            </tr>
            <tr>
              <td align="left">invalid_audience</td>
              <td align="left">The SET audience Audience does not correspond to the SET Recipient.</c>
                    <c>authentication_failed</c><c>The Recipient.</td>
            </tr>
            <tr>
              <td align="left">authentication_failed</td>
              <td align="left">The SET Recipient could not authenticate the
                        SET Transmitter.</c>
                    <c>access_denied</c><c>The Transmitter.</td>
            </tr>
            <tr>
              <td align="left">access_denied</td>
              <td align="left">The SET Transmitter is not authorized to transmit the
                        SET to the SET Recipient.</c>
                </texttable> Recipient.</td>
            </tr>
          </tbody>
        </table>
        <t>
		  Other Error Codes may also be received,
		  as the set of Error Codes is extensible
		  via the IANA "Security Event Token Delivery Error Codes" registry
		  established in <xref target="iana_set_errors"/>. target="iana_set_errors" format="default"/>.
        </t>
      </section>
    </section>

    <section anchor="aa" title="Authentication toc="default" numbered="true">
      <name>Authentication and Authorization" toc="default"> Authorization</name>
      <t>The SET delivery method described in this specification is based upon
      HTTP over TLS <xref target="RFC2818"/> target="RFC2818" format="default"/> and standard
      HTTP authentication and authorization schemes, as per <xref
      target="RFC7235" />. format="default"/>.  The TLS server certificate MUST
      <bcp14>MUST</bcp14> be validated using DNS-ID <xref target="RFC6125"/> target="RFC6125"
      format="default"/> and/or DANE DNS-Based Authentication of Named Entities
      (DANE) <xref target="RFC6698"/>. target="RFC6698" format="default"/>.
      </t>
      <t>
	      Authorization for the eligibility to provide actionable SETs can be determined by
	      using the identity of the SET Issuer,
	      the identity of the SET Transmitter, perhaps using mutual TLS,
	      or via other employed authentication methods.
	      Because SETs are
	      not commands, SET Recipients are free to ignore SETs that
	      are not of interest.
      </t>
    </section>
    <section anchor="reliability" title="Delivery Reliability" toc="default"> toc="default" numbered="true">
      <name>Delivery Reliability</name>
      <t>
                Delivery reliability requirements may vary depending upon the use cases.
		This specification defines the response from the SET
                Recipient in such a way as to provide the SET Transmitter with the
                information necessary to determine what further action is required,
                if any, in order to meet their requirements.  SET Transmitters with
                high reliability requirements may be tempted to always retry failed
                transmissions. However, it should be noted that for many types of SET
                delivery errors, a retry is extremely unlikely to be successful.  For
                example, <spanx style="verb">invalid_request</spanx> <tt>invalid_request</tt> indicates a structural
                error in the content of the request body that is likely to remain when
                re-transmitting
                retransmitting the same SET.  Others such as <spanx style="verb">access_denied</spanx> <tt>access_denied</tt>
                may be transient, for example example, if the SET Transmitter refreshes expired
                credentials prior to re-transmission. retransmission.
      </t>
      <t>
                The SET Transmitter may be unaware of whether or not a SET has been delivered
                to a SET Recipient. For example, a network interruption could prevent the
                SET Transmitter from receiving the success response, or a service outage could
                prevent the SET Transmitter from recording the fact that the SET was delivered.
                It is left to the implementer to decide how to handle such cases, based on
                their requirements. For example, it may be appropriate for the SET Transmitter to
                re-transmit
                retransmit the SET to the SET Recipient, erring on the side of guaranteeing delivery,
                or it may be appropriate to assume delivery was successful, erring on the side of
                not spending resources re-transmitting retransmitting previously delivered SETs. Other options,
                such as sending the SET to a "dead letter queue" for manual examination may also
                be appropriate.
      </t>
      <t>
                Implementers SHOULD <bcp14>SHOULD</bcp14> evaluate the reliability requirements of their use cases and the
                impact of various retry mechanisms and re-transmission retransmission policies on the performance
                of their systems to determine an appropriate strategy for handling various error
                conditions.
      </t>
    </section>
    <section anchor="Security" title="Security Considerations" toc="default"> toc="default" numbered="true">
      <name>Security Considerations</name>
      <section anchor="payloadAuthentication" title="Authentication numbered="true" toc="default">
        <name>Authentication Using Signed SETs"> SETs</name>
        <t>
		  JWS signed SETs can be
		  used (see <xref target="RFC7515"/> target="RFC7515" format="default"/> and Section 5 of
		  <xref target="RFC8417"/>) target="RFC8417" sectionFormat="of" section="5"/>)
		  to enable the SET Recipient
		  to validate that the SET Issuer is authorized to provide actionable SETs.
        </t>
      </section>
      <section anchor="HTTP" title="HTTP Considerations"> numbered="true" toc="default">
        <name>HTTP Considerations</name>
        <t>SET delivery depends on the use of Hypertext Transfer Protocol and
        is thus subject to the security considerations of HTTP Section 9 of <xref
	      target="RFC7230"/> (<xref
        target="RFC7230" sectionFormat="of" section="9"/>) and its related
        specifications.</t>
      </section>
      <section anchor="Confidentiality" title="Confidentiality numbered="true" toc="default">
        <name>Confidentiality of SETs"> SETs</name>
        <t>
		  SETs may contain sensitive information, including Personally
		  Identifiable Information (PII), or be distributed through
		  third parties.  In such cases, SET Transmitters and SET
		  Recipients MUST <bcp14>MUST</bcp14> protect the confidentiality
		  of the SET contents.  TLS MUST <bcp14>MUST</bcp14> be used to
		  secure the transmitted SETs.  In some use cases, encrypting
		  the SET as described in <xref target="RFC7516">JWE</xref> target="RFC7516"
		  format="default">JWE</xref> will also be required.  The
		  Event delivery endpoint MUST <bcp14>MUST</bcp14> support at least
		  TLS version 1.2 <xref target="RFC5246"/> target="RFC5246" format="default"/>
		  and SHOULD <bcp14>SHOULD</bcp14> support the newest version of TLS
		  that meets its security requirements, which as of the time
		  of this publication is TLS 1.3 <xref target="RFC8446"/>. target="RFC8446"
		  format="default"/>.  The client MUST <bcp14>MUST</bcp14> perform
		  a TLS/SSL server certificate check using DNS-ID <xref target="RFC6125"/>
		  target="RFC6125" format="default"/> and/or DANE <xref target="RFC6698"/>.
		  target="RFC6698" format="default"/>.  How a SET Transmitter
		  determines the expected service identity to match the SET
		  Recipient's server certificate against is out of scope for
		  this document.  The implementation security considerations
		  for TLS in "Recommendations for Secure Use of TLS Transport
		  Layer Security (TLS) and DTLS" Datagram Transport Layer Security
		  (DTLS)" <xref target="RFC7525"/>
		    MUST target="RFC7525" format="default"/>
		  <bcp14>MUST</bcp14> be followed.
        </t>
      </section>
      <section anchor="DoS" title="Denial numbered="true" toc="default">
        <name>Denial of Service"> Service</name>
        <t>
                    The SET Recipient may be vulnerable to a denial-of-service attack where a
                    malicious party makes a high volume of requests containing invalid SETs,
                    causing the endpoint to expend significant resources on cryptographic
                    operations that are bound to fail. This may be mitigated by authenticating
                    SET Transmitters with a mechanism such as mutual TLS.
		    Rate-limiting problematic transmitters is also a possible means of mitigation.
        </t>
      </section>
      <section anchor="Persisted" title="Authenticating numbered="true" toc="default">
        <name>Authenticating Persisted SETs"> SETs</name>
        <t>
                    At the time of receipt, the SET Recipient can rely upon TLS
                    mechanisms, HTTP authentication methods, and/or other context from the
                    transmission request to authenticate the SET Transmitter and validate the
                    authenticity of the SET.  However, this context is typically unavailable to
                    systems to which the SET Recipient forwards the SET, or to systems that
                    retrieve the SET from storage.  If the SET Recipient requires the ability to
                    validate SET authenticity outside of the context of the transmission request,
                    then the SET Recipient SHOULD <bcp14>SHOULD</bcp14> ensure that such SETs have been signed in
                    accordance with <xref target="RFC7515"/>. target="RFC7515" format="default"/>.
		    Needed context could also be stored with the SET and retrieved with it.
        </t>
      </section>
    </section>
    <section anchor="Privacy" title="Privacy Considerations"> numbered="true" toc="default">
      <name>Privacy Considerations</name>
      <t>
                SET Transmitters should attempt to deliver SETs that are targeted to the specific
                business and protocol needs of subscribers.
      </t>
      <t>When sharing personally identifiable information or information
                that is otherwise considered confidential to affected users, SET
                Transmitters and Recipients MUST <bcp14>MUST</bcp14> have the appropriate legal agreements
                and user consent or terms of service in place.
		Furthermore, data that needs confidentiality protection MUST <bcp14>MUST</bcp14> be encrypted,
		at least with TLS
		and sometimes also using JSON Web Encryption (JWE) <xref target="RFC7516"/>. target="RFC7516" format="default"/>.
      </t>
      <t>
	      In some cases, subject identifiers themselves may be considered sensitive
	      information, such that their inclusion within a SET may be considered a violation
	      of privacy.  SET Issuers and SET Transmitters should consider the ramifications of sharing a
	      particular subject identifier with a SET Recipient (e.g., whether doing so could
	      enable correlation and/or de-anonymization of data) and choose appropriate
	      subject identifiers for their use cases.
      </t>
    </section>
    <section anchor="IANA" title="IANA Considerations"> numbered="true" toc="default">
      <name>IANA Considerations</name>
      <section anchor="iana_set_errors" title="Security numbered="true" toc="default">
        <name>Security Event Token Delivery Error Codes"> Codes</name>
        <t>
                    This document defines Security Event Token Delivery Error
                    Codes, for which IANA
                    is asked to create has created and maintain now maintains a
                    new registry titled "Security Event Token
                    Delivery Error
                    Codes".  Initial values for the Security "Security Event Token Delivery
                    Error Codes Codes" registry are defined in <xref target="reqErrors"/>
                    target="reqErrors" format="default"/> and registered
                    below.  Future assignments are to be made through the
                    Specification Required registration policy (<xref target="RFC8126"/>) <xref
                    target="RFC8126" format="default"/> and shall follow the
                    template below.
        </t>
        <t>
                    Error Codes are intended to be interpreted by automated systems, and therefore SHOULD
                    systems; therefore, they <bcp14>SHOULD</bcp14> identify
                    classes of errors to which an automated system could
                    respond in a meaningfully distinct way (e.g., by
                    refreshing authentication credentials and retrying the
                    request).
        </t>
        <t>
		  Error Code names are case sensitive.
		  Names may not match other registered names in a case-insensitive manner
		  unless the Designated Experts state that there is a compelling reason
		  to allow an exception.
        </t>
        <t>
		  Criteria that should be applied by the Designated Experts includes
		  determining whether the proposed registration duplicates existing functionality,
		  whether it is likely to be of general applicability
		  or whether it is useful only for a single application,
		  and whether the registration description is clear.
        </t>

        <t>
		  It is suggested that multiple Designated Experts be
		  appointed who are able to represent the perspectives of
		  different applications using this specification, specification in order to
		  enable broadly informed review of registration decisions.
		  In cases where a registration decision could be perceived as
		  creating a conflict of interest for a particular Expert, expert,
		  that Expert expert should defer to the judgment of the other Experts.
		  experts.
        </t>
        <section anchor="iana_set_errors_template" title="Registration Template">
                    <t>
                        <list style="hanging">
                            <t hangText="Error Code">
                                <vspace/> numbered="true" toc="default">
          <name>Registration Template</name>
          <dl newline="true" spacing="normal">
            <dt>Error Code</dt>
            <dd>
                                The name of the Security Event Token Delivery
                                Error Code, as described in <xref target="error_codes"/>.
                                target="error_codes" format="default"/>. The
                                name MUST <bcp14>MUST</bcp14> be a case-sensitive
                                ASCII string consisting only of letters,
                                digits, and underscore; these are the
                                characters whose codes fall within the
                                inclusive ranges 0x30-39, 0x41-5A,
                                0x5F 0x5F, and
                                0x61-7A.
                            </t>
                            <t hangText="Description">
                                <vspace/>
                            </dd>
            <dt>Description</dt>
            <dd>
                                A brief human-readable description of the Security Event Token Delivery
                                Error Code.
                            </t>
                            <t hangText="Change Controller">
                                <vspace/>
                            </dd>
            <dt>Change Controller</dt>
            <dd>
                                For error codes registered by the IETF or its working groups, list "IETF".
				For all other error codes, list the name of the
                                party responsible for the registration.  Contact information such as
                                mailing address, email address, or phone number may also be provided.
                            </t>
                            <t hangText="Defining Document(s)">
                                <vspace/>
                            </dd>
            <dt>Reference</dt>
            <dd>
                                A reference to the document or documents that define the Security Event
                                Token Delivery Error Code. The definition MUST <bcp14>MUST</bcp14> specify the name and
                                description of the error code and explain under what circumstances the
                                error code may be used. URIs that can be used to retrieve copies of each
                                document at no cost SHOULD <bcp14>SHOULD</bcp14> be included.
                            </t>
                        </list>
                    </t>
                            </dd>
          </dl>
        </section>
        <section anchor="InitialContents" title="Initial numbered="true" toc="default">
          <name>Initial Registry Contents">
		  <t>
		    <?rfc subcompact="yes"?>
		    <list style="hanging">
		      <t>Error Code: invalid_request</t>
                      <t>Description: The Contents</name>
          <dl newline="false" spacing="compact">
            <dt>Error Code:</dt><dd>invalid_request</dd>

            <dt>Description:</dt><dd>The request body cannot be parsed as a SET or the event
                          payload Event
                          Payload within the SET does not conform to the event's definition.</t>
		      <t>Change Controller: IETF</t>
		      <t>Defining Document(s): definition.</dd>

            <dt>Change Controller:</dt><dd>IETF</dd>

            <dt>Reference:</dt><dd>
		      <xref target="error_codes"/> target="error_codes" format="default"/> of [[ this specification ]]
		      </t>
		    </list>
		  </t>
		  <t>
		    <list style="hanging">
                      <t>Error Code: invalid_key</t>
                      <t>Description: One RFC 8935
		      </dd>
          </dl>

          <dl newline="false" spacing="compact">
            <dt>Error Code:</dt><dd>invalid_key</dd>
            <dt>Description:</dt><dd>One or more keys used to encrypt or sign the SET is invalid
                          or otherwise unacceptable to the SET Recipient (expired, revoked,
                          failed certificate validation, etc.).</t>
		      <t>Change Controller: IETF</t>
		      <t>Defining Document(s): etc.).</dd>
            <dt>Change Controller:</dt><dd>IETF</dd>
            <dt>Reference:</dt><dd>
		      <xref target="error_codes"/> target="error_codes" format="default"/> of [[ this specification ]]
		      </t>
		    </list>
		  </t>
		  <t>
		    <list style="hanging">
                      <t>Error Code: invalid_issuer</t>
                      <t>Description: The RFC 8935
		      </dd>
          </dl>

          <dl newline="false" spacing="compact">
            <dt>Error Code:</dt><dd>invalid_issuer</dd>
            <dt>Description:</dt><dd>The SET issuer Issuer is invalid for the SET Recipient.</t>
		      <t>Change Controller: IETF</t>
		      <t>Defining Document(s): Recipient.</dd>
            <dt>Change Controller:</dt><dd>IETF</dd>
            <dt>Reference:</dt><dd>
		      <xref target="error_codes"/> target="error_codes" format="default"/> of [[ this specification ]]
		      </t>
		    </list>
		  </t>
		  <t>
		    <list style="hanging">
                      <t>Error Code: invalid_audience</t>
                      <t>Description: The RFC 8935
		      </dd>
          </dl>

          <dl newline="false" spacing="compact">
            <dt>Error Code:</dt><dd>invalid_audience</dd>
            <dt>Description:</dt><dd>The SET audience Audience does not correspond to the SET Recipient.</t>
		      <t>Change Controller: IETF</t>
		      <t>Defining Document(s): Recipient.</dd>
            <dt>Change Controller:</dt><dd>IETF</dd>
            <dt>Reference:</dt><dd>
		      <xref target="error_codes"/> target="error_codes" format="default"/> of [[ this specification ]]
		      </t>
		    </list>
		  </t>
		  <t>
		    <list style="hanging">
                      <t>Error Code: authentication_failed</t>
                      <t>Description: The RFC 8935
		      </dd>
          </dl>

          <dl newline="false" spacing="compact">
            <dt>Error Code:</dt><dd>authentication_failed</dd>
            <dt>Description:</dt><dd>The SET Recipient could not authenticate the SET Transmitter.</t>
		      <t>Change Controller: IETF</t>
		      <t>Defining Document(s): Transmitter.</dd>
            <dt>Change Controller:</dt><dd>IETF</dd>
            <dt>Reference:</dt><dd>
		      <xref target="error_codes"/> target="error_codes" format="default"/> of [[ this specification ]]
		      </t>
		    </list>
		  </t>
		  <t>
		    <list style="hanging">
                      <t>Error Code: access_denied</t>
                      <t>Description: The RFC 8935
		      </dd>
          </dl>
          <dl newline="false" spacing="compact">
            <dt>Error Code:</dt><dd>access_denied</dd>
            <dt>Description:</dt><dd>The SET Transmitter is not authorized to transmit the
                          SET to the SET Recipient.</t>
		      <t>Change Controller: IETF</t>
		      <t>Defining Document(s): Recipient.</dd>
            <dt>Change Controller:</dt><dd>IETF</dd>
            <dt>Reference:</dt><dd>
		      <xref target="error_codes"/> target="error_codes" format="default"/> of [[ this specification ]]
		      </t>
		    </list>
		  </t> RFC 8935
		      </dd>
          </dl>
        </section>
		<?rfc subcompact="no"?>
      </section>
    </section>
  </middle>
  <back>
        <references title="Normative References">
            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml' ?>
            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2277.xml'?><!-- IETF Language Policy -->
            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2818.xml' ?><!-- HTTP over TLS -->
            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.5246.xml' ?><!-- TLS 1.2 -->

            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.6125.xml' ?><!-- TLS Certs -->
            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.6698.xml' ?><!-- DANE -->

	    <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7230.xml' ?><!-- HTTP Msg -->
            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7231.xml' ?><!-- HTTP Semantics -->
            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7515.xml' ?><!-- JWS -->
            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7516.xml' ?><!-- JWE -->
            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7519.xml' ?><!-- JWT -->
            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7525.xml' ?><!-- TLS Recos -->

            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8126.xml' ?>
            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml' ?>
            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8259.xml' ?><!-- JSON -->
            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8417.xml'?><!-- SET -->
	    <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8446.xml' ?><!-- TLS 1.3 -->
        </references>

        <references title="Informative References">
	  <?rfc include="http://xml2rfc.tools.ietf.org/public/rfc/bibxml3/reference.I-D.draft-ietf-secevent-http-poll-12.xml" ?>

            <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7235.xml' ?><!-- HTTP Auth -->

    <references>
      <name>References</name>
      <references>
        <name>Normative References</name>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/>
        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2277.xml"/>

            <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2818.xml"/>

            <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5246.xml"/>

            <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6125.xml"/>

            <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6698.xml"/>

	    <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7230.xml"/>

            <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7231.xml"/>

            <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7515.xml"/>

            <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7516.xml"/>

            <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7519.xml"/>

            <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7525.xml"/>

            <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8126.xml"/>
            <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/>
            <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8259.xml"/>

            <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8417.xml"/>

	    <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8446.xml"/>

        </references>

	<section anchor="Unencrypted" title="Unencrypted Transport Considerations">
	  <t>
	    Earlier versions of this specification made the use of TLS optional
	    and described
      <references>
        <name>Informative References</name>

<reference anchor="RFC8936" target="https://www.rfc-editor.org/info/rfc8936">

<front>
<title>Poll-Based Security Event Token (SET) Delivery Using HTTP</title>

<author initials='A' surname='Backman' fullname='Annabelle Backman' role='editor'>
    <organization />
</author>

<author initials='M' surname='Jones' fullname='Michael Jones'>
    <organization />
</author>

<author initials='M' surname='Scurtescu' fullname='Marius Scurtescu'>
    <organization />
</author>

<author initials='M' surname='Ansari' fullname='Morteza Ansari'>
    <organization />
</author>

<author initials='A' surname='Nadalin' fullname='Anthony Nadalin'>
    <organization />
</author>

<date month='October' year='2020' />

</front>

<seriesInfo name="RFC" value="8936"/>
<seriesInfo name="DOI" value="10.17487/RFC8936"/>
</reference>

        <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7235.xml"/>

        </references>
    </references>
    <section anchor="Unencrypted" numbered="true" toc="default">
      <name>Unencrypted Transport Considerations</name>
      <t>
	    Earlier versions of this specification made the use of TLS optional
	    and described security and privacy considerations resulting from use
	    of unencrypted HTTP as the underlying transport.
	    When the working group decided to mandate usage of HTTP over TLS,
	    it also decided to preserve the description of these considerations
	    in this non-normative appendix.
      </t>
      <t>
	    SETs may contain sensitive information that is considered
	    Personally Identifiable Information (PII).
	    In such cases, SET Transmitters and
	    SET Recipients MUST <bcp14>MUST</bcp14> protect the confidentiality of the SET contents.
	    When TLS is not used, this means that the SET MUST <bcp14>MUST</bcp14> be encrypted
	    as described in <xref target="RFC7516">JWE</xref>. target="RFC7516" format="default">JWE</xref>.
      </t>
      <t>
	    If SETs were allowed to be transmitted over unencrypted channels, some privacy-sensitive
	    information about them might leak, even though the SETs themselves are encrypted.
	    For instance, an attacker may be able to determine whether or not a SET was accepted and the reason for its rejection
	    or may be able to derive information from being able to observe the size of the encrypted SET.
	    (Note that even when TLS is utilized, some information leakage is still possible;
	    message padding algorithms to prevent side channels remain an open research topic.)
      </t>
    </section>

    <section anchor="Others" title="Other Streaming Specifications">
            <t>[[ NOTE TO THE RFC EDITOR: This section to be removed prior to publication ]]</t>

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

            <t>Poll-Based Security Event Token (SET) Delivery Using HTTP</t>
            <t>In addition anchor="Acknowledgments" numbered="false" toc="default">
      <name>Acknowledgments</name>
      <t>
	    The editors would like to this specification, thank the WG is defining a polling-based
                SET delivery protocol. That protocol <xref target="I-D.ietf-secevent-http-poll"/>
                describes it as:</t>
            <figure><artwork>This specification defines how a series members of Security Event Tokens
(SETs) can be delivered to an intended recipient using HTTP POST over
TLS initiated as a poll by the recipient.  The specification also
defines how delivery can be assured, subject to the SET Recipient's
need for assurance.</artwork>
            </figure>

            <t>XMPP Events</t>
            <t>The WG considered XMPP Events and their ability SCIM Working Group, which
	    began discussions of provisioning events starting with draft-hunt-scim-notify-00 in 2015.
	    We would like to provide a single
                messaging solution without the need for both polling and push modes.
                The feeling was the size thank <contact fullname="Phil Hunt"/> and methodology of XMPP was too far apart from the current capabilities other authors of the SECEVENTs community, draft-ietf-secevent-delivery-02,
	    upon which focuses in
                on HTTP based service delivery and authorization.</t>

            <t>Amazon Simple Notification Service</t>
            <t>Simple Notification Service this specification 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 does not directly
                support pull, but subscribers can get the pull model by creating an
                SQS queue and subscribing it based.
	    We would like to thank the topic. Note that this puts the
                cost of pull support back onto the subscriber, just as it is participants 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 SecEvents
	    Working Group for their own internal delivery guarantees.
                The long tail of OIDC clients may not care about that or may fail contributions 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 am
                not suggesting that we need all of these things in the spec, but
                they give an idea of what features people have found useful.</t>
            <t>Other information:<list style="symbols">
                <t>API Reference: http://docs.aws.amazon.com/AWSSimpleQueueService/latest/APIReference/Welcome.html</t>
                <t>Visibility Timeouts: http://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-visibility-timeout.html</t>
                </list></t>

            <t>Apache Kafka</t>
            <t>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 that 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</t>

            <t>Google Pub/Sub</t>
            <t>The Google Pub Sub system favors a model whereby polling and acknowledgement
                of events is done with separate endpoints and as separate functions.</t>
            <t>Information:<list style="symbols">
                <t>Cloud Overview - https://cloud.google.com/pubsub/</t>
                <t>Subscriber Overview - https://cloud.google.com/pubsub/docs/subscriber</t>
                <t>Subscriber Pull(poll) - https://cloud.google.com/pubsub/docs/pull</t>
            </list></t>
        </section>

        <section anchor="Acknowledgments" title="Acknowledgments">
	  <t>
	    The editors would like to thank the members of the SCIM working group, which
	    began discussions of provisioning events starting with draft-hunt-scim-notify-00 in 2015.
	    We would like to thank Phil Hunt and the other authors of draft-ietf-secevent-delivery-02,
	    upon which this specification is based.
	    We would like to thank the participants in the SecEvents
	    working group for their contributions to this specification.
	  </t>
	  <t>
	    Additionally, this specification.
      </t>
      <t>
	    Additionally, we would like to thank the following individuals for their reviews of the specification:
	    Joe Clarke,
	    Roman Danyliw,
	    Vijay Gurbani,
	    Benjamin Kaduk,
	    Erik Kline,
	    Murray Kucherawy,
	    Barry Leiba,
	    Yaron Sheffer,
	    Robert Sparks,
	    Valery Smyslov,
	    Éric Vyncke,
	    and
	    Robert Wilton.
	  </t>
        </section>

        <section anchor="History" title="Change Log">
            <t>[[ NOTE TO THE RFC EDITOR: This section to be removed prior to publication ]]</t>

            <t>Draft 00 - AB - Based on draft-ietf-secevent-delivery-02 with the
                following changes:<list style="symbols">
                <t>Renamed to "Push-Based SET Token Delivery Using HTTP"</t>
                <t>Removed references to the HTTP Polling delivery method.</t>
                <t>Removed informative reference to RFC6202.</t>
                </list></t>
            <t>
                Draft 01 - AB:
                <list style="symbols">
                    <t>Fixed area and workgroup to match secevent.</t>
                    <t>Removed unused definitions and definitions already covered by SET.</t>
                    <t>Renamed Event Transmitter and Event Receiver to SET Transmitter and SET Receiver, respectively.</t>
                    <t>Added IANA registry for SET Delivery Error Codes.</t>
                    <t>Removed enumeration of HTTP authentication methods.</t>
                    <t>Removed generally applicable guidance for HTTP, authorization tokens, and bearer tokens.</t>
                    <t>Moved guidance for using authentication methods as DoS protection to Security Considerations.</t>
                    <t>Removed redundant instruction to use WWW-Authenticate header.</t>
                    <t>Removed further generally applicable guidance for authorization tokens.</t>
                    <t>Removed bearer token from example delivery request, and text referencing it.</t>
                    <t>Broke delivery method description into separate request/response sections.</t>
                    <t>Added missing empty line between headers and body in example request.</t>
                    <t>Removed inapplicable notes about example formatting.</t>
                    <t>Removed text about SET creation and handling.</t>
                    <t>Removed duplication in protocol description.</t>
                    <t>Added "non-normative example" text to example transmission request.</t>
                    <t>Fixed inconsistencies in use of Error Code term.</t>
                </list>
            </t>
            <t>
                Draft 02 - AB:
                <list style="symbols">
                    <t>Rewrote abstract and introduction.</t>
                    <t>Rewrote definitions for SET Transmitter, SET Receiver.</t>
                    <t>Renamed Event Delivery section to SET Delivery.</t>
                    <t>Readability edits to Success Response and Failure Response sections.</t>
                    <t>Consolidated definition of error response under Failure Response section.</t>
                    <t>Removed Event Delivery Process section and moved its content to parent section.</t>
                    <t>Readability edits to SET Delivery section and its subsections.</t>
                    <t>Added callout that SET Receiver HTTP endpoint configuration is out-of-scope.</t>
                    <t>Added callout that SET verification mechanisms are out-of-scope.</t>
                    <t>Added retry guidance, notes regarding delivery reliability requirements.</t>
                    <t>Added guidance around using JWS and/or JWE to authenticate persisted SETs.</t>
                </list>
            </t>
            <t>
	      Draft 03 - mbj:
	      <list style="symbols">
		<t>
		  Addressed problems identified in my 18-Jul-18 review message titled
		  "Issues for both the Push and Poll Specs".
		</t>
		<t>
		  Changes to align terminology with RFC 8417, for instance,
		  by using the already defined term SET Recipient rather than SET Receiver.
		</t>
		<t>
		  Applied editorial and minor normative corrections.
		</t>
		<t>
		  Updated Marius' contact information.
		</t>
	      </list>
            </t>
            <t>
                Draft 04 - AB:
                <list style="symbols">
                    <t>Replaced Error Codes with smaller set of meaningfully differentiated codes.</t>
                    <t>Added more error response examples.</t>
                    <t>Removed un-referenced normative references.</t>
                    <t>Added normative reference to JSON in error response definition.</t>
                    <t>
                        Added text clarifying that the value of the <spanx style="verb">description</spanx>
                        attribute in error responses is implementation specific.
                    </t>
                    <t>Added requirement that error descriptions and responses are UTF-8 encoded.</t>
                    <t>
                        Added error description language preferences and specification via <spanx style="verb">Accept-Language</spanx>
                        and <spanx style="verb">Content-Language</spanx> headers.
                    </t>
                    <t>Added "recognized issuer" validation requirement in section 2.</t>
                    <t>Added timeouts as an acceptable reason to resend a SET in section 2.</t>
                    <t>Edited text in section 1 to clarify that configuration is out of scope.</t>
                    <t>Made minor editorial corrections.</t>
                </list>
            </t>
            <t>
                Draft 05 - AB:
                <list style="symbols">
                    <t>Made minor editorial corrections.</t>
                    <t>Updated example request with a correct SET header and signature.</t>
                    <t>Revised TLS guidance to allow implementers to provide confidentiality protection via JWE.</t>
                    <t>Revised TLS guidance to require *at least* TLS 1.2.</t>
                    <t>Revised TLS guidance to recommend supporting the newest version of TLS that meets security requirements.</t>
                    <t>Revised SET Delivery Error Code format to allow the same set of characters as is allowed in error codes in RFC6749.</t>
                    <t>Added mention of HTTP Poll spec to list of other streaming specs in appendix.</t>
                    <t>Added validation step requiring SET Recipient to verify that the SET is one which the SET Transmitter is expected to send to the SET Recipient.</t>
                    <t>Changed responding to errors with an appropriate HTTP status code from optional to recommended.</t>
                    <t>Changed Error Codes registry change policy from Expert Review to First Come First Served; added guidance that error codes are meant to be consumed by automated systems.</t>
                    <t>Added text making clear that it is up to SET Recipients whether or not they will accept SETs where the SET Issuer is different from the SET Transmitter.</t>
                    <t>Reworded guidance around signing and/or encrypting SETs for integrity protection.</t>
                    <t>Renamed TLS "Support Considerations" section to "Confidentiality of SETs".</t>
                    <t>Reworded guidance around subject identifier selection and privacy concerns.</t>
                </list>
            </t>
            <t>
                Draft 06 - mbj, MS:
                <list style="symbols">
                    <t>Made minor editorial corrections.</t>
                    <t>Updated to indicate that failure response should be returned if errors occur in authenticating the SET.</t>
                    <t>Updated reference for JSON from RFC 7159 to RFC 8259.</t>
                    <t>Fixed Authentication Using Signed SETs to indicate the SET Transmitter must be authorized to deliver the SET, not the SET Issuer.</t>
                    <t>Fixed Authenticating Persisted SETs to put the responsibility for ensuring the SET is signed on the SET Recipient.</t>
                    <t>Fixed error code format definition to match error codes defined in doc.</t>
                </list>
            </t>
            <t>
                Draft 07 - AB:
                <list style="symbols">
                    <t>Made minor editorial corrections.</t>
                    <t>Removed "SET Recipient" definition and added explicit list of terms used from RFC8417.</t>
                </list>
            </t>
	    <t>
	      Draft 08 - mbj
	      <list style="symbols">
		<t>
		  Addressed area director review comments by Benjamin Kaduk.
		</t>
	      </list>
	    </t>
	    <t>
	      Draft 09 - mbj + AB
	      <list style="symbols">
		<t>
		  Corrected editorial nits.
		</t>
	      </list>
	    </t>
            <t>
                Draft 10 - AB
                <list style="symbols">
                    <t>
                        Addressed area director review comments by Benjamin Kaduk:
                        <list style="symbols">
                            <t>Added reference to 8417 as definition document for SETs.</t>
                            <t>
                                Added text clarifying that determining the SET Recipient's service identity
                                is out of scope.
                            </t>
                            <t>
                                Added normative recommendation for transmitters to target SETs to specific
                                business needs of subscribers.
                            </t>
                            <t>Minor editorial corrections.</t>
                        </list>
                    </t>
                </list>
            </t>
	    <t>
	      Draft 11 - mbj
	      <list style="symbols">
		<t>
		  Addressed SecDir review comments by Valery Smyslov.
		</t>
		<t>
		  Addressed OpsDir review comments by Joe Clarke.
		</t>
		<t>
		  Addressed GenArt review comments by Vijay Gurbani.
		</t>
	      </list>
	    </t>
	    <t>
	      Draft 12 - mbj
	      <list style="symbols">
		<t>
		  Revised to unambiguously require the use of TLS,
		  while preserving descriptions of precautions needed for non-TLS use in an appendix.
		</t>
	      </list>
	    </t>
	    <t>
	      Draft 13 - mbj
	      <list style="symbols">
		<t>
		  Addressed IESG comments.
		</t>
	      </list>
	    </t>
            <t>
                Draft 14 - AB
                <list style="symbols">
                    <t>
                        Revised normative requirements for SET re-transmission to clarify "at least once"
                        delivery expectiations.
                    </t>
                    <t>
                        Added non-normative text to Section 4 - Delivery Reliability describing conditions
                        where re-transmission of successfully delivered SETs may occur.
                    </t>
                </list>
	    <contact fullname="Joe Clarke"/>,
	    <contact fullname="Roman Danyliw"/>,
	    <contact fullname="Vijay Gurbani"/>,
	    <contact fullname="Benjamin Kaduk"/>,
	    <contact fullname="Erik Kline"/>,
	    <contact fullname="Murray Kucherawy"/>,
	    <contact fullname="Barry Leiba"/>,
	    <contact fullname="Yaron Sheffer"/>,
	    <contact fullname="Robert Sparks"/>,
	    <contact fullname="Valery Smyslov"/>,
	    <contact fullname="Éric Vyncke"/>,
	    and
	    <contact fullname="Robert Wilton"/>.
      </t>
    </section>

  </back>
</rfc>