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), which can be optionally signed and/or encrypted. A SET describes a statement of fact from the perspective of an issuer that it intends to share with one or more receivers.

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at http://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

1. Introduction and Overview

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 [RFC7519] in order to provide a self-contained token that can be optionally signed using JSON Web Signature (JWS) [RFC7515] and/or encrypted using JSON Web Encryption (JWE) [RFC7516].

This specification profiles the use of JWT for the purpose of issuing security event tokens (SETs). This specification defines a base format upon which profiling specifications define actual events and their meanings. Unless otherwise specified, this specification uses non-normative example events intended to demonstrate how events may be constructed.

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.

Security Events are not commands issued between parties. A security event is a statement of fact from the perspective of an issuer about the state of a security subject (e.g., a web resource, token, IP address, the issuer itself) that the issuer controls or is aware of, that 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 could describe a direct change of entity state, an implicit change of state or other higher-level security statements such as:

While subject state changes are often triggered by a user-agent or security-subsystem, the issuance and transmission of an event often occurs asynchronously and in a back-channel to the action which caused the change that generated the security event. Subsequently, an Event Receiver having received a SET, validates and interprets the received SET and takes its own independent action, if any. For example, having been informed of a personal identifier being associated with a different security subject (e.g., an email address is being used by someone else), the Event Receiver may choose to ensure that the new user is not granted access to resources associated with the previous user. Or, the Event Receiver may not have any relationship with the subject, and no action is taken.

While Event Receivers will often take actions upon receiving SETs, security events MUST NOT be assumed to be commands or requests. The intent of this specification is to define a way of exchanging statements of fact that subscribers may interpret for their own purposes. As such, SETs have no capability for error signaling other to ensure the validation of a received SET.

1.1. Notational Conventions

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

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

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.

1.2. Definitions

2. The Security Event Token (SET)

A SET conveys a statement (in the form of a JWT [RFC7519]) about a single security event in relation to a Subject.

The schema and structure of a SET follows the JWT [RFC7519] specification. A SET has the following structure:

The following is a non-normative example showing the JWT Claims Set for a hypothetical SCIM password reset SET. This example shows an additional events value (https://example.com/scim/event/passwordResetExt) used to convey additional information -- in this case, the current count of reset attempts:

{ 
  "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}
  }
}

Figure 1: Example SCIM Password Reset Event

The event in the figure above expresses hypothetical password reset event for SCIM [RFC7644]. The JWT consists of:

An events claim specifying the hypothetical SCIM URN (urn:ietf:params:scim:event:passwordReset) for a password reset, and a local schema, https://example.com/scim/event/passwordResetExt, that is used to provide additional event information such as the current count of resets.
An iss claim, denoting the Event Transmitter.
The sub claim specifies the SCIM resource URI that was affected.
The aud claim specifies the intended audiences for the event. The syntax of the "aud" claim is defined in Section 4.1.3 [RFC7519].

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.

Here is another example JWT Claims Set for a security event token, this one for a Logout Token:

{
   "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": {}
   }
}

Figure 2: Example OpenID Back-Channel Logout Event

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:

{ 
  "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"
      ]
    }
  }
}

Figure 3: Example Consent Event

2.1. Core SET Claims

The following are claims that are based on [RFC7519] claim definitions and are profiled for use in an event token:

jti: As defined by Section 4.1.7 [RFC7519] 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.
iss: 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 iss value within the event "payload" (see events claim).
aud: The syntax of the claim is as defined in Section 4.1.3 [RFC7519]. This claim MAY contains one or more audience identifiers for the SET. This claim is RECOMMENDED.
iat: As defined by Section 4.1.6 [RFC7519], a value containing a NumericDate, which represents when the event was issued. Unless otherwise specified, the value SHOULD be interpreted as equivalent to the actual time of the event. This claim is REQUIRED.
nbf: Defined by Section 4.1.5 [RFC7519], 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.
sub: As defined by Section 4.1.2 [RFC7519], 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.
exp: As defined by [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.

The following are new claims defined by this specification:

events: 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 events claim SHOULD NOT be used to express multiple logical events.
: The value of events 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 ({}), or it MAY be a JSON object containing data as described by the Profiling Specification.
txn: 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.

2.2. Security Event Token Construction

A SET is a JWT [RFC7519] that is constructed by building a JSON structure that constitutes an event object which is then used as the body of a JWT.

While this specification uses JWT to convey a SET, implementers SHALL NOT use SETs to convey authentication or authorization assertions.

The following is an example JWT Claims Set for a security event token (which has been formatted for readability):

{  
  "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"]
    }
  }
}

Figure 4: Example Event Claims

When transmitted, the above JSON body must be converted into a JWT as per [RFC7519].

The following is an example of a SCIM Event expressed as an unsecured JWT. The JWT header of:

{"alg":"none"}

Base64url encoding of the octets of the UTF-8 representation of the header yields:

eyJhbGciOiJub25lIn0

The example JSON Event Data is encoded as follows:
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The encoded JWS signature is the empty string. Concatenating the parts yields:

eyJhbGciOiJub25lIn0
.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.

Figure 5: Example Unsecured Security Event Token

For the purpose of a simpler example in Figure 5, an unencrypted token was shown. When SETs are not signed or encrypted, the Event Receiver MUST depend upon TLS and HTTP to authenticate the sender and the security of the channel to authenticate the SET and its sender.

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 [RFC7519].

3. Security Considerations

3.1. Confidentiality and Integrity

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 [RFC5246] and MAY support additional transport-layer mechanisms meeting its security requirements. When using TLS, the client MUST perform a TLS/SSL server certificate check, per [RFC6125]. Implementation security considerations for TLS can be found in "Recommendations for Secure Use of TLS and DTLS" [RFC7525].

Security Events distributed through third-parties or that carry personally identifiable information, SHOULD be encrypted using JWE [RFC7516] or secured for confidentiality by other means.

Security Events distributed without authentication over the channel, such as via TLS ([RFC5246] and [RFC6125]), and/or OAuth2 [RFC6749], or Basic Authentication [RFC7617], MUST be signed using JWS [RFC7515] so that individual events MAY be authenticated and validated by the Event Receiver.

3.2. Delivery

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.

3.3. Sequencing

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.

Profiling Specifications and implementers SHOULD take caution when using timestamps such as iat to define order. Distributed systems will have some amount of clock-skew and thus time by itself will not guarantee order.

Specifications profiling SET SHOULD define a mechanism for detecting order or sequence of events. For example, the txn claim could contain an ordered value (e.g., a counter) that the issuer defines.

3.4. Timing Issues

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.

3.5. Distinguishing SETs from Access Tokens

Because [RFC7519] states that all claims that are not understood by implementations MUST be ignored., 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:

Avoid use of the JWT claim exp within the envelope.
Where possible, use a separate aud 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.
Modify access validation systems to check for the presence of the events claim as a means to detect security event tokens. This is particularly useful if the same endpoint may receive both types of tokens.
Consider avoiding use of the sub claim at the top level.

4. Privacy Considerations

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

Event Transmitters SHOULD attempt to specialize feeds so that the content is targeted to the specific business and protocol needs of subscribers.

When sharing personally identifiable information or information that is otherwise considered confidential to affected users, Event Transmitters and Receivers MUST have the appropriate legal agreements and user consent or terms of service in place.

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

5. IANA Considerations

5.1. JSON Web Token Claims Registration

This specification registers the events and txn claims in the IANA "JSON Web Token Claims" registry [IANA.JWT.Claims] established by [RFC7519].

5.1.1. Registry Contents

Claim Name: events
Claim Description: Security Event Object
Change Controller: IESG
Specification Document(s): Section 2 of [[ this specification ]]
Claim Name: txn
Claim Description: Transaction Identifier
Change Controller: IESG
Specification Document(s): Section 2 of [[ this specification ]]

6. References

6.1. Normative References

[IANA.JWT.Claims]	IANA, "JSON Web Token Claims"
[RFC2119]	Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC3986]	Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005.
[RFC5246]	Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008.
[RFC6125]	Saint-Andre, P. and J. Hodges, "Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March 2011.
[RFC6749]	Hardt, D., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012.
[RFC7519]	Jones, M., Bradley, J. and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015.
[RFC7525]	Sheffer, Y., Holz, R. and P. Saint-Andre, "Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 2015.
[RFC7617]	Reschke, J., "The 'Basic' HTTP Authentication Scheme", RFC 7617, DOI 10.17487/RFC7617, September 2015.

6.2. Informative References

[openid-connect-core]	Sakimura, N., Bradley, J., Jones, M., de Medeiros, B. and C. Mortimore, "OpenID Connect Core 1.0", November 2014.
[RFC7009]	Lodderstedt, T., Dronia, S. and M. Scurtescu, "OAuth 2.0 Token Revocation", RFC 7009, DOI 10.17487/RFC7009, August 2013.
[RFC7515]	Jones, M., Bradley, J. and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015.
[RFC7516]	Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)", RFC 7516, DOI 10.17487/RFC7516, May 2015.
[RFC7517]	Jones, M., "JSON Web Key (JWK)", RFC 7517, DOI 10.17487/RFC7517, May 2015.
[RFC7644]	Hunt, P., Grizzle, K., Ansari, M., Wahlstroem, E. and C. Mortimore, "System for Cross-domain Identity Management: Protocol", RFC 7644, DOI 10.17487/RFC7644, September 2015.
[saml-core-2.0]	Internet2, "Assertions and Protocols for the OASIS Security Assertion Markup Language (SAML) V2.0", March 2005.

Appendix A. Acknowledgments

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

The editors would like to thank the participants in the IETF id-event mailing list and related working groups for their support of this specification.

Appendix B. Change Log

From the original draft-hunt-idevent-token:

Draft 01 - PH - Renamed eventUris to events

Draft 00 - PH - First Draft

Draft 01 - PH - Fixed some alignment issues with JWT. Remove event type attribute.

Draft 02 - PH - Renamed to Security Events, removed questions, clarified examples and intro text, and added security and privacy section.

Draft 03 - PH events claim, and proof-reading corrections.

General edit corrections from Sarah Squire
Changed "event" term to "SET"
Corrected author organization for William Denniss to Google
Changed definition of SET to be 2 parts, an envelope and 1 or more payloads.
Clarified that the intent is to express a single event with optional extensions only.

- mbj - Registered

Draft 04 - PH -

Re-added the "sub" claim with clarifications that any SET type may use it.
Added additional clarification on the use of envelope vs. payload attributes
Added security consideration for event timing.
Switched use of "attribute" to "claim" for consistency.
Revised examples to put "sub" claim back in the top level.
Added clarification that SETs typically do not use "exp".
Added security consideration for distinguishing Access Tokens and SETs.

Draft 05 - PH - Fixed find/replace error that resulted in claim being spelled claimc

Draft 06 - PH -

Corrected typos
New txn claim
New security considerations Sequencing and Timing Issues

Draft 07 -

PH - Moved payload objects to be values of event URI attributes, per discussion.
mbj - Applied terminology consistency and grammar cleanups.

Draft 08 - PH -

Added clarification to status of examples
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).
Other editorial changes suggested by Yaron

From draft-ietf-secevent-token:

Draft 00 - PH - First WG Draft based on draft-hunt-idevent-token

Draft 01 - PH - Changes as follows:

Changed terminology away from pub-sub to transmitter/receiver based on WG feedback
Cleaned up/removed some text about extensions (now only used as example)
Clarify purpose of spec vs. future profiling specs that define actual events

Authors' Addresses

Phil Hunt (editor) Oracle Corporation EMail: phil.hunt@yahoo.com

William Denniss Google EMail: wdenniss@google.com

Morteza Ansari Cisco EMail: morteza.ansari@cisco.com

Michael B. Jones Microsoft EMail: mbj@microsoft.com URI: http://self-issued.info/

Abstract

Status of This Memo

Copyright Notice

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