draft-hunt-idevent-token.xml

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<rfc category="std" docName="draft-hunt-idevent-token-08" ipr="trust200902">
  <front>
    <title abbrev="draft-hunt-idevent-token">Security Event Token (SET)</title>

    <author fullname="Phil Hunt" initials="P." role="editor" surname="Hunt">
      <organization abbrev="Oracle">Oracle Corporation</organization>

      <address>
        <email>phil.hunt@yahoo.com</email>
      </address>
    </author>
    
    <author fullname="William Denniss" initials="W." surname="Denniss">
      <organization abbrev="Google">Google</organization>

      <address>
        <email>wdenniss@google.com</email>
      </address>
    </author>
    

    <author fullname="Morteza Ansari" initials="M.A." surname="Ansari">
      <organization abbrev="Cisco">Cisco</organization>

      <address>
        <email>morteza.ansari@cisco.com</email>
      </address>
    </author>

    <author fullname="Michael B. Jones" initials="M.B." surname="Jones">
      <organization abbrev="Microsoft">Microsoft</organization>
      <address>
        <email>mbj@microsoft.com</email>
	      <uri>http://self-issued.info/</uri>
      </address>
    </author>

    <date year="2017"/>

    <area>Security</area>
    <workgroup>Security Events Working Group</workgroup>

    <keyword>Identity</keyword>
    <keyword>Security</keyword>
    <keyword>Event</keyword>
    <keyword>Token</keyword>
    <keyword>Internet-Draft</keyword>

    <abstract>
      <t>This specification defines the Security Event Token, which may
      be distributed via a protocol such as HTTP. The Security Event Token 
      (SET) specification profiles the JSON Web Token (JWT) and may be optionally signed 
      and/or encrypted. A SET describes a statement of fact that may be 
      shared by an event publisher with event subscribers.</t>
    </abstract>
  </front>

  <middle>
    <section anchor="intro" title="Introduction and Overview" toc="default">
      <t>This specification defines an extensible Security Event Token 
      (SET) format which may be exchanged using protocols such as HTTP. 
      The specification builds on the JSON Web Token (JWT) format <xref target="RFC7519"/> 
      in order to provide a self-contained token that can be optionally 
      signed using JSON Web Signature (JWS) <xref target="RFC7515"/>
      and/or encrypted using JSON Web Encryption (JWE) <xref target="RFC7516"/>.</t>
      
      <t>For the purpose of this specification, an event is a statement
      of fact by a publisher (also known as the event issuer) that the state of 
      a security subject (e.g., a web resource, token, IP address) it 
      controls or is aware of, has changed in some way (explicitly or 
      implicitly). A security subject may be permanent (e.g., a user account) or 
      temporary (e.g., an HTTP session) in nature. A state change 
      may include direct changes of entity state, implicit changes to state 
      or other higher-level security statements such as:
      <list style="symbols">
        <t>The creation, modification, removal of a resource.</t>
        <t>The resetting or suspension of an account.</t>
        <t>The revocation of a security token prior to its expiry.</t>
        <t>The logout of a user session. Or, </t>
        <t>A cumulative conclusion such as to indicate that a user has 
        taken over an email identifier that may have been used in the 
        past by another user.</t>
      </list>
      </t>
      
      <t>Based on some externally agreed criteria for an event feed, 
      the publisher distributes events to the appropriate subscribers of a
      feed. While an event may be delivered via synchronous means (e.g., 
      HTTP POST), the distribution of the event often happens 
      asynchronously to the change of state which generated the security 
      event. As an example, an OAuth2 Authorization Server 
      <xref target="RFC6749"/>, having received a token revocation 
      request <xref target="RFC7009"/>, may issue a token revocation 
      event to downstream web resource providers. Having been informed 
      of a token revocation, the OAuth2 web resource service provider 
      may add the token identifier to its local revocation list assuming 
      the token has not already expired.</t>
      
      <t>A subscriber having received an event, validates and interprets the
      event and takes its own independent action, if any. For example, 
      having been informed of a personal identifier now being associated 
      with a different security subject (i.e., is being used by someone else), the 
      subscriber may choose to ensure that the new user is not granted 
      access to resources associated with the previous user. Or it may
      not have any relationship with the subject, and no action is taken.</t>
      
      <t>While subscribers will often take actions upon receiving one
      or more events, events MUST NOT be assumed to be commands or requests. 
      To do so requires complex bi-directional signals and error recovery 
      mechanisms that fall outside the scope of this specification. 
      The intent of this specification is to define a way of exchanging 
      statements of fact that subscribers may interpret for their own
      purposes. Since events are typically historical statements by a publisher
      and are not commands, idempotency or lack thereof, does not apply.</t>
      
      <t>Unless otherwise specified, this specification uses example 
      events intended to serve as non-normative examples showing how an 
      event may be constructed. It is expected that other "profiling" 
      specifications will use this specification to define normative 
      events within some specified context or protocol.</t>
      
      <t>This specification is scoped to security and identity related events.
      While security event tokens may be used for other purposes, the specification
      only considers security and privacy concerns relevant to identity 
      and personal information.</t>

      <section anchor="notat" title="Notational Conventions" toc="default">
        <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
        "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
        document are to be interpreted as described in <xref
        target="RFC2119"/>. These keywords are capitalized when used to
        unambiguously specify requirements of the protocol or application
        features and behavior that affect the inter-operability and security of
        implementations. When these words are not capitalized, they are meant
        in their natural-language sense.</t>

        <t>For purposes of readability, examples are not URL encoded.
        Implementers MUST percent encode URLs as described in <xref
        target="RFC3986">Section 2.1 of</xref>.</t>

        <t>Throughout this document, all figures MAY contain spaces and extra
        line-wrapping for readability and space limitations. Similarly, some
        URIs contained within examples have been shortened for space and
        readability reasons.</t>
      </section>

      <section anchor="defs" title="Definitions" toc="default">
        
        <t>
          The following definitions are used with SETs:
          <list style="hanging">
            
            <t hangText="Feed Publisher"><vspace blankLines="0"/>The Feed Publisher creates
              SETs to be distributed to registered subscribers. In JWT
              terminology, the Feed Publisher is also known as the issuer
              (<spanx style="verb">iss</spanx>).
            </t>

            <t hangText="Security Event Token (SET)"><vspace blankLines="0"/>An SET is a 
              JWT that is to be
              distributed to one or more registered subscribers. A SET MAY
              be signed or encrypted using JWS and/or JWE for authentication 
              and confidentiality reasons.
            </t>

            <t hangText="Feed"><vspace blankLines="0"/>A Feed is a logical
              grouping of SETs or a context under which SETs may be issued. 
              A Subscriber registers with the Feed Publisher to subscribe
              to SETs associated with a Feed. How a Feed is defined or
              the method for subscription is out-of-scope of this specification.
            </t>
            
            <t hangText="Subscriber"><vspace blankLines="0"/>A Subscriber 
              registers to receive SETs from a Feed Publisher using a protocol 
              such as  HTTP. The method of registration and delivery is out-of-scope
              of this specification.
            </t>
            
            <t hangText="Security Subject"><vspace blankLines="0"/>A 
            Security Subject is the entity to which a SET refers. A 
            Security Subject may be a principle (e.g., 
            <xref target="RFC7519">Section 4.1.2</xref>), a web resource,
            or other thing such as an IP address that a SET might reference.</t>
          </list>
        </t>
      </section>
    </section>

    <section anchor="events" title="The Security Event Token (SET)">
      <t>A SET conveys a statement (in the form of a JWT
      <xref target="RFC7519"/>) about a single security event in relation
      to a Security Subject that may be of 
      interest to a Subscriber or set of Subscribers receiving SETs from
      a Feed Publisher.</t>
      
      <t>The schema and structure of a SET follows the JWT <xref target="RFC7519"/>
      specification. A SET has the following structure:
      <list style="symbols">
        <t>An outer JSON structure that acts as the SET envelope. The envelope 
        contains a set of name/value pairs called the JWT Claims Set, 
        typically common to every SET or common to a number of different 
        Security Events within a single profiling specification or a 
        related series of specifications. Claims in the envelope SHOULD 
        be registered in the JWT Token Claims Registry <xref target="RFC7519">Section 10.1</xref> or be
        Public Claims or Private Claims as also defined in <xref target="RFC7519"/>.</t>
        
        <t>Envelope claims that are profiled and defined 
        in this specification are used to validate a SET and declare 
        the event data included in the SET. The claim <spanx style="verb">events</spanx>
        identifies the security event types being expressed related to the 
        Security Subject and MAY also include event-specific data.</t> 
        
        <t>Each JSON member of the <spanx style="verb">events</spanx> object is a
        name/value pair. The JSON attribute name is a URI String value 
        that expresses an event type. The corresponding value is a JSON object known as the 
        event "payload". The payload JSON object contains claims
        typically unique to the event's URI type value and are not
        registered as JWT claims. These claims are defined
        by their associated event specification. An event with no  
        payload claims SHALL be represented as the empty JSON object 
        (<spanx style="verb">{}</spanx>). In many cases, one event URI expresses
        the primary event URI, while other events might be considered extensions
        that MAY be used to do things such as:<list style="symbols">
          <t>A categorization event type to provide classification 
          information (e.g., threat type or level).</t>
          <t>An enhancement of an existing specifications the arise over time.</t>
          <t>An extensions needed to link a potential series of events.</t>
          <t>Localized specific purpose extensions needed between a
          particular publisher and subscriber.</t>
        </list></t>
        
      </list>
      </t>

      <figure anchor="examplePassword" title="Example SCIM Password Reset Event">
        <preamble>The following is a non-normative example showing the JWT Claims Set for a hypothetical 
        SCIM password reset SET. This example shows an extension 
        (<spanx style="verb">https://example.com/scim/event/passwordResetExt</spanx>)
        that is used to convey additional information -- in this case, the current
        count of reset attempts:</preamble>
        <artwork>
{ 
  "jti": "3d0c3cf797584bd193bd0fb1bd4e7d30",
  "iat": 1458496025,
  "iss": "https://scim.example.com",  
  "aud": [
    "https://jhub.example.com/Feeds/98d52461fa5bbc879593b7754",
    "https://jhub.example.com/Feeds/5d7604516b1d08641d7676ee7"
  ],  
  "sub": "https://scim.example.com/Users/44f6142df96bd6ab61e7521d9",
  "events": {
    "urn:ietf:params:scim:event:passwordReset": 
      { "id":"44f6142df96bd6ab61e7521d9"},
    "https://example.com/scim/event/passwordResetExt": 
      { "resetAttempts":5}
  }
}
</artwork>
      </figure>      
      <t>The event in the figure above expresses hypothetical password
      reset event for SCIM <xref target="RFC7644"/>. The JWT consists of:<list style="symbols">
        <t>An <spanx style="verb">events</spanx> claim specifying the hypothetical 
        SCIM URN (<spanx style="verb">urn:ietf:params:scim:event:passwordReset</spanx>) 
        for a password reset, and a custom extension, 
        <spanx style="verb">https://example.com/scim/event/passwordResetExt</spanx>, 
        that is used to provide additional event information such as the 
        current count of resets.</t>
        <t>An <spanx style="verb">iss</spanx>
        claim, denoting the event publisher.</t>
        <t>The <spanx style="verb">sub</spanx> claim specifies the SCIM 
        resource URI that was affected.</t>
        <t>The <spanx style="verb">aud</spanx> claim specifies the 
        intended audiences for the event. In practical terms, an audience MAY be 
        the URI for an event feed that a client has subscribed to.
        </t>
      </list></t>
      
      <t>In this example, the SCIM event 
      indicates that a password has been updated and the current 
      password reset count is 5. Notice that the value for 
      "resetAttempts" is actually part of its own JSON object associated
      with its own event URI attribute.  
      </t>

      <t><figure anchor="exampleBackLogoutEvent" title="Example OpenID Back-Channel Logout Event">
            <preamble>Here is another example JWT Claims Set for a security event token, this one
              for a Logout Token:</preamble>

            <artwork>
{
   "iss": "https://server.example.com",
   "sub": "248289761001",
   "aud": "s6BhdRkqt3",
   "iat": 1471566154,
   "jti": "bWJq",
   "sid": "08a5019c-17e1-4977-8f42-65a12843ea02",
   "events": {
     "http://schemas.openid.net/event/backchannel-logout": {}
   }
}
</artwork>
          </figure>Note that the above SET has an empty JSON object and
          uses the JWT registered claims <spanx style="verb">sub</spanx> 
          and <spanx style="verb">sid</spanx> to identify the subject
          that was logged-out.</t>
          <t>
          
          <figure anchor="exampleConsent" title="Example Consent Event">
        <preamble>In the following example JWT Claims Set, a fictional medical service collects 
          consent for medical actions and notifies other parties. The individual
          for whom consent is identified was originally authenticated via
          OpenID Connect.  In this case, the issuer of the security event is an
          application rather than the OpenID provider:</preamble>
        <artwork>
{ 
  "jti": "fb4e75b5411e4e19b6c0fe87950f7749",
  
  "sub": "248289761001",
  "iat": 1458496025,
  "iss": "https://my.examplemed.com",  
  "aud": [
    "https://rp.example.com"
  ],  
  "events": {
    "https://openid.net/heart/specs/consent.html":{
      "iss":"https://connect.example.com",
      "consentUri":[
        "https://terms.examplemed.com/labdisclosure.html#Agree"
      ]
    }
  }
}
</artwork>
      </figure>  
      In the above example, the attribute <spanx style="verb">iss</spanx> contained within the
      payload for the event <spanx style="verb">https://openid.net/heart/specs/consent.html</spanx>, refers
      to the issuer of the Security Subject (<spanx style="verb">sub</spanx>) rather than the event
      issuer <spanx style="verb">https://my.examplemed.com</spanx>. They are
      distinct from the top level value of <spanx style="verb">iss</spanx>
      which always refers to the issuer of the event - a medical consent
      service that is a relying party to the OpenID Provider.
          </t>
      
      <section anchor="EventContents" title="Core SET Claims">
        <t>The following are claims that are based on <xref target="RFC7519"/>
        claim definitions and are profiled for use in an event
        token:<list style="hanging">
            <t hangText="jti"><vspace blankLines="0"/>As defined by 
            <xref target="RFC7519">Section 4.1.7</xref> contains a unique
            identifier for an event. The identifier SHOULD be unique within
            a particular event feed and MAY be used by clients to track
            whether a particular event has already been received. This 
            claim is REQUIRED.</t>

            <t hangText="iss"><vspace blankLines="0"/>A single valued
            String containing the URI of the service provider publishing
            the SET (the issuer). This claim is REQUIRED. Note that when
            a SET is expressing an event about a Security Subject for
            which the SET issuer is not the issuer of the Security Subject,
            the conflict SHALL be resolved by including the Security Subject
            <spanx style="verb">iss</spanx> value within the event "payload" 
            (see <spanx style="verb">events</spanx> claim). </t>
 
            <t hangText="aud"><vspace blankLines="0"/>As defined in <xref target="RFC7519">Section 4.1.3</xref>,
            an array containing the StringOrURI values representing the 
            audience of the event. Values are typically URLs of
            the feeds the event is associated with. This claim is RECOMMENDED.</t>
            
            <t hangText="iat"><vspace blankLines="0"/>As defined by <xref target="RFC7519">Section 4.1.6</xref>,
            a value containing a NumericDate, which represents when the 
            event was issued. Unless otherwise specified,
            the value SHOULD be interpreted by the subscriber as equivalent 
            to the actual time of the event. This claim is REQUIRED. 
            </t> 
            
            <t hangText="nbf"><vspace blankLines="0"/>Defined by 
            <xref target="RFC7519">Section 4.1.5</xref>, a number 
            whose value is a NumericDate. In the context of the SET token
            it SHALL be interpreted to mean a date in which
            the event is believed to have occurred (in the past) or will occur in the 
            future. Note: there MAY be some cases where "nbf"
            is still smaller than "iat" such as when it took an extended 
            time for a SET to be issued (for example after some analysis). 
            This claim is OPTIONAL.</t> 
            
            <t hangText="sub">As defined by <xref target="RFC7519">Section 4.1.2</xref>,
            a String or URI value representing the principal or the subject of the SET. 
            This is usually the entity whose "state" was changed. For example,
            an IP Address was added to a black list. A URI representing a
            user resource that was modified. A token identifier for a revoked 
            token. If used, the profile specification SHOULD
            define the content and format semantics for the value. This claim
            is OPTIONAL, as the principal for any given profile may already be
            identified without the inclusion of a subject claim.</t>   
            
            <t hangText="exp">As defined by <xref target="RFC7519"/>, this claim
            is time on which the JWT MUST NOT be accepted for processing. In 
            the context of a SET however, this notion does not apply since
            a SET reflects something that has already been processed and is
            historical in nature. While some specifications MAY have a need
            for this claim, its use in general cases is NOT RECOMMENDED.</t>       
          </list>
        </t>
        <t>The following are new claims defined by this specification:<list style="hanging">
            <t hangText="events" anchor="eventDef"><vspace blankLines="0"/>
            The semantics of this claim is to define a set of event statements
            that each MAY add additional claims to fully describe a single
            logical event that has occurred (e.g. a state change to a subject).
            Multiple event statements of the same type SHALL NOT be accepted. 
            The <spanx style="verb">events</spanx>
            claim SHOULD NOT be used to express multiple logical events.</t>
            <t>The value of <spanx style="verb">events</spanx> is a
            JSON object whose members are a set of JSON name/value pairs
            whose names are URIs representing the event statements being 
            expressed. Event URI values SHOULD be stable values (e.g. a
            permanent URL for an event specification). For each name present, 
            the corresponding value 
            SHALL be a JSON object. The JSON object MAY be an empty 
            object (<spanx style="verb">{}</spanx>), or it MAY be a JSON 
            object containing data as described by the profiling event 
            specification.</t>
            <t hangText="txn" anchor="txnDef"><vspace blankLines="0"/>
	          An OPTIONAL String value that represents a unique transaction 
            identifier. In cases where multiple SETs are issued based on 
            different event URIs, the transaction
            identifier MAY be used to correlate SETs to the same 
            originating event or stateful change.</t>
        </list></t>
      </section>

      <section anchor="eventMessage" title="Security Event Token Construction">
        <t>A SET is a JWT <xref target="RFC7519"/> that is 
        constructed by building a JSON structure that constitutes an event 
        object and which is then used as the body of a JWT.</t>
        <t>While this specification uses JWT to convey a SET, implementers
        SHALL NOT use SETs to convey authentication or authorization assertions.</t>

        <t><figure anchor="exampleJsonEvent" title="Example Event Claims">
            <preamble>The
            following is an example JWT Claims Set for a security event token (which has been formatted
            for readability):</preamble>

            <artwork>
{  
  "jti": "4d3559ec67504aaba65d40b0363faad8",
  "iat": 1458496404,
  "iss": "https://scim.example.com",  
  "aud": [
   "https://scim.example.com/Feeds/98d52461fa5bbc879593b7754",
   "https://scim.example.com/Feeds/5d7604516b1d08641d7676ee7"
  ],  
  
  "events": {
    "urn:ietf:params:scim:event:create": {
      "ref":
        "https://scim.example.com/Users/44f6142df96bd6ab61e7521d9",
      "attributes":["id", "name", "userName", "password", "emails"]
    }
  }
}
</artwork>
          </figure></t>

        <t>When transmitted, the above JSON body must be converted into a JWT
        as per <xref target="RFC7519"/>.</t>
     
        <t><figure>
            <preamble>The following is an example of a SCIM Event expressed as
            an unsecured JWT. The JWT header of:</preamble>

            <artwork>{"alg":"none"}</artwork>
          </figure><figure>
            <preamble>Base64url encoding of the octets of the UTF-8
            representation of the header yields:</preamble>

            <artwork>eyJhbGciOiJub25lIn0</artwork>
          </figure>
	  <figure>
            <preamble>The example JSON Event Data is encoded as
            follows:</preamble>

            <artwork>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</artwork>
          </figure>
          <figure anchor="eventToken"
            title="Example Unsecured Security Event Token">
            <preamble>The encoded JWS signature is the empty string.
            Concatenating the parts yields:</preamble>

            <artwork>
eyJhbGciOiJub25lIn0
.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.
</artwork>
          </figure></t>

        <t>For the purpose of a simpler example in <xref target="eventToken"/> 
        an unencrypted token was shown. When SETs are not signed or
        encrypted, the subscriber MUST depend upon TLS and HTTP to 
        authenticate the sender and the security of the channel to 
        authenticate the SET and its sender.
        </t>
        <t>When validation (i.e. auditing), or additional transmission
        security is required, JWS Signing and JWS Encryption MAY be used. 
        To create and or validate a signed or encrypted SET, follow
        the instructions in section 7 of <xref
        target="RFC7519"/>.</t>
      </section>
    </section>

    <section anchor="Security" title="Security Considerations" toc="default">

      
      <section title="Confidentiality and Integrity">
      <t>SETs may often contain sensitive information. Therefore,
      methods for distribution of events SHOULD require the use of a 
      transport-layer security mechanism when distributing events. 
      Parties MUST support TLS 1.2 <xref target="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 <xref target="RFC6125"/>. Implementation
      security considerations for TLS can be found in "Recommendations for
      Secure Use of TLS and DTLS" <xref target="RFC7525"/>.</t>
      
      <t>Security Events distributed through third-parties or that carry personally
      identifiable information, SHOULD be encrypted using JWE <xref target="RFC7516"/>
      or secured for confidentiality by other means.
      </t>
      <t>Security Events distributed without authentication over the channel, such
      as via TLS (<xref target="RFC5246"/> and <xref target="RFC6125"/>), 
      and/or OAuth2 <xref target="RFC6749"/>, or Basic Authentication <xref target="RFC7617"/>,
      MUST be signed using JWS <xref target="RFC7515"></xref> so
      that individual events MAY be authenticated and validated by the subscriber.</t>      
      </section>
      
      <section title="Delivery">
      <t>This specification does not define a delivery mechanism by itself.
      In addition to confidentiality and integrity (discussed above), implementers
      and profile specifications MUST consider the consequences of delivery 
      mechanisms that are not secure and/or not assured. For example, while
      a SET may be end-to-end secured using JWE encrypted SETs, without TLS 
      there is no assurance that the correct endpoint received the SET and 
      that it could be successfully processed.</t>
      </section>
      
      <section title="Sequencing">
        <t>As defined in this specification, there is no defined way to order
        multiple SETs in a sequence. Depending on the type and nature of SET
        event, order may or may not matter. For example, in provisioning, 
        event order is critical -- an object could not be modified before it
        was created. In other SET types, such as a token revocation, the order
        of SETs for revoked tokens does not matter. If however, the event was
        described as a log-in or logged-out status for a user subject, then 
        order becomes important.</t>
        
        <t>Extension specifications and implementers SHOULD take caution when
        using timestamps such as <spanx style="verb">iat</spanx> to define order. Distributed systems will have 
        some amount of clock-skew and thus time by itself will not guarantee order.</t>
        
        <t>Specifications profiling SET SHOULD define a mechanism for detecting
        order or sequence of events. For example, the <spanx style="verb">txn</spanx>
        claim could contain an ordered value (e.g., a counter) that the publisher defines.</t>
      </section>
      
      <section title="Timing Issues">
        <t>When SETs are delivered asynchronously and/or out-of-band with respect to
        the original action that incurred the security event, it is important
        to consider that a SET might be delivered to a Subscriber in advance
        or well behind the process that caused the event. For example, a 
        user having been required to logout and then log back in again, may
        cause a logout SET to be issued that may arrive at the same time 
        as the user-agent accesses a web site having just logged-in. If
        timing is not handled properly, the effect would be to erroneously
        treat the new user session as logged out. Profiling specifications 
        SHOULD be careful to anticipate timing and subject selection information. 
        For example, it might be more appropriate to cancel a "session" 
        rather than a "user". Alternatively, the specification could use timestamps
        that allows new sessions to be started immediately after a stated 
        logout event time.</t>
      </section>
      
      <section title="Distinguishing SETs from Access Tokens">
        <t>Because <xref target="RFC7519"/> states that <spanx style="verb">all claims that are not understood
        by implementations MUST be ignored.</spanx>, there is a consideration that 
        a SET token might be confused as an access or authorization token in 
        the case where a SET is mistakenly or intentionally intercepted and 
        presented as an access token. To avoid this, it is recommended that
        implementers consider one or more of the following:<list style="symbols">
          <t>Avoid use of the JWT claim <spanx style="verb">exp</spanx> within the
          envelope.</t>
          <t>Where possible, use a separate <spanx style="verb">aud</spanx>
          claim value to distinguish between the SET subscriber and the 
          audience of an access token. For example, a Logout while intended
          for the same relying party could use a different audience to 
          distinguish between normal access and logout notification.</t>
          <t>Modify access validation systems to check for the presence of 
          the <spanx style="verb">events</spanx> claim as a means to detect
          security event tokens. This is particularly useful if the same endpoint
          may receive both types of tokens.</t>
          <t>Consider avoiding use of the <spanx style="verb">sub</spanx>
          claim at the top level.</t>
        </list></t>
      </section>
    </section>
    
    <section title="Privacy Considerations">
    
      <t>If a SET needs to be retained for audit purposes, JWS MAY 
      be used to provide verification of its authenticity.</t>
      
      <t>Event Publishers SHOULD attempt to specialize feeds so that the content
      is 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, the 
      publishers and subscribers MUST have the appropriate legal agreements
      and user consent in place.</t>
      
      <t>The propagation of subject identifiers can be perceived as personally
      identifiable information. Where possible, publishers and subscribers
      should devise approaches that prevent propagation -- for example, the
      passing of a hash value that requires the subscriber to already know
      the subject.</t>
    </section>

    <section anchor="IANA" title="IANA Considerations">

      <section anchor="ClaimsRegistry" title="JSON Web Token Claims Registration">
	<t>
	  This specification registers the <spanx style="verb">events</spanx> and
	  <spanx style="verb">txn</spanx> claims in the IANA
	  "JSON Web Token Claims" registry <xref target="IANA.JWT.Claims"/>
	  established by <xref target="RFC7519"/>.
	</t>

	<section anchor='ClaimsContents' title='Registry Contents'>
	  <t>
	    <?rfc subcompact="yes"?>
	    <list style='symbols'>
	      <t>
		Claim Name: <spanx style="verb">events</spanx>
	      </t>
	      <t>
		Claim Description: Security Event Object
	      </t>
	      <t>
		Change Controller: IESG
	      </t>
	      <t>
		Specification Document(s): <xref target="events"/> of [[ this specification ]]
	      <vspace blankLines="1"/></t>
        
        <t>
    Claim Name: <spanx style="verb">txn</spanx>
        </t>
        <t>
    Claim Description: Transaction Identifier
        </t>
        <t>
    Change Controller: IESG
        </t>
        <t>
    Specification Document(s): <xref target="events"/> of [[ this specification ]]
        </t>
	    </list>
	  </t>
	</section>
	<?rfc subcompact="no"?>
      </section>
      
    </section>
  </middle>

  <back>
    <references title="Normative References">

    <!-- 
      <reference anchor="idevent-subscription">
        
        <front>
          <title>Identity Event Subscription Protocol (work in progress)</title>
          <author fullname="Phil Hunt"><organization>Oracle Corporation</organization></author>
          <date/>
        </front>  
      </reference>
       -->
       
      <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml' ?><!-- Keywords -->
      <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.3986.xml'?><!-- URIs -->
      <?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 Cert-->
      <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.6749.xml'?><!-- OAuth 2 -->
      <?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 BCP -->
      <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7617.xml'?><!-- Basic Auth -->

      <reference anchor="IANA.JWT.Claims" target="http://www.iana.org/assignments/jwt">
        <front>
          <title>JSON Web Token Claims</title>
          <author>
            <organization>IANA</organization>
          </author>
	  <date/>
        </front>
      </reference>

    </references>
 
    <references title="Informative References">
      <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7009.xml'?><!-- OAuth Revocation -->
      <?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.7517.xml'?><!-- JWK -->
      <?rfc include='http://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7644.xml'?><!-- SCIM Protocl -->
     
 <!-- 
      <reference anchor="RISC">
        <front>
          <title>OpenID Risk and Incident Sharing and Coordination (RISC) Working Group</title>
          <author> <organization>OpenID Foundation</organization></author>
          <date/>
        </front>
      </reference>

      <reference anchor="HEART" target="http://openid.net/wg/heart/">
        <front>
          <title>OpenID Health Relationship Trust (HEART) Working Group</title>
          <author> <organization>OpenID Foundation</organization></author>
          <date/>
        </front>
      </reference>
      
       -->

    </references>

    <!-- <section anchor="Contributors" title="Contributors"/> Uncomment if and when this section is non-empty -->

    <section anchor="Acknowledgments" title="Acknowledgments">
      <t>The editors would like to thank the participants in the IETF id-event
      mailing list and related working groups for their support of this specification.</t>
    </section>

    <section anchor="History" title="Change Log">
      <t>Draft 01 - PH - Renamed eventUris to events</t>
      <t>Draft 00 - PH - First Draft</t>
      <t>Draft 01 - PH - Fixed some alignment issues with JWT. Remove event type attribute.</t>
      <t>Draft 02 - PH - Renamed to Security Events, removed questions, clarified examples and intro text, and added security and privacy section.</t>
      <t>Draft 03 - PH <list style="symboles">
        <t>General edit corrections from Sarah Squire</t>
        <t>Changed "event" term to "SET"</t>
        <t>Corrected author organization for William Denniss to Google</t>
        <t>Changed definition of SET to be 2 parts, an envelope and 1 or more payloads.</t>
        <t>Clarified that the intent is to express a single event with optional extensions only.</t>
      </list>
                  - mbj - Registered <spanx style="verb">events</spanx> claim, and proof-reading corrections.</t> 
      <t>Draft 04 - PH - <list style="symbols">
        <t>Re-added the "sub" claim with clarifications that any SET type may use it.</t>
        <t>Added additional clarification on the use of envelope vs. payload attributes</t>
        <t>Added security consideration for event timing.</t>
        <t>Switched use of "attribute" to "claim" for consistency.</t>
        <t>Revised examples to put "sub" claim back in the top level.</t>
        <t>Added clarification that SETs typically do not use "exp".</t>
        <t>Added security consideration for distinguishing Access Tokens and SETs.</t>
      </list></t>
      
      <t>Draft 05 - PH - Fixed find/replace error that resulted in claim being spelled claimc</t>
      <t>Draft 06 - PH - <list style="symbols">
        <t>Corrected typos</t>
        <t>New txn claim</t>
        <t>New security considerations Sequencing and Timing Issues</t>
      </list></t>
      <t>
	Draft 07 -
	<list style="symbols">
	  <t>PH - Moved payload objects to be values of event URI attributes, per discussion.</t>
	  <t>mbj - Applied terminology consistency and grammar cleanups.</t>
	</list>
      </t>
      <t>Draft 08 - PH - <list style="symbols">
        <t>Added clarification to status of examples</t>
        <t>Changed from primary vs. extension to state that multiple 
        events may be expressed, some of which may or may not
        be considered extensions of others (which is for the subscriber 
        or profiling specifications to determine).</t>
        <t>Other editorial changes suggested by Yaron </t>
      </list></t>
    </section>
  </back>
</rfc>