Security Event Token (SET)
draft-ietf-secevent-token-02
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (secevent WG) | |
|---|---|---|---|
| Authors | Phil Hunt , William Denniss , Morteza Ansari , Michael Jones | ||
| Last updated | 2017-07-28 (Latest revision 2017-06-30) | ||
| Replaces | draft-hunt-idevent-token | ||
| Stream | Internet Engineering Task Force (IETF) | ||
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| IESG | IESG state | I-D Exists | |
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draft-ietf-secevent-token-02
Security Events Working Group P. Hunt, Ed.
Internet-Draft Oracle
Intended status: Standards Track W. Denniss
Expires: January 1, 2018 Google
M. Ansari
Cisco
M. Jones
Microsoft
June 30, 2017
Security Event Token (SET)
draft-ietf-secevent-token-02
Abstract
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.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 1, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction and Overview . . . . . . . . . . . . . . . . . . 2
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4
1.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4
2. The Security Event Token (SET) . . . . . . . . . . . . . . . 5
2.1. Core SET Claims . . . . . . . . . . . . . . . . . . . . . 8
2.2. Explicit Typing of SETs . . . . . . . . . . . . . . . . . 10
2.3. Security Event Token Construction . . . . . . . . . . . . 10
3. Requirements for SET Profiles . . . . . . . . . . . . . . . . 12
4. Security Considerations . . . . . . . . . . . . . . . . . . . 13
4.1. Confidentiality and Integrity . . . . . . . . . . . . . . 13
4.2. Delivery . . . . . . . . . . . . . . . . . . . . . . . . 13
4.3. Sequencing . . . . . . . . . . . . . . . . . . . . . . . 13
4.4. Timing Issues . . . . . . . . . . . . . . . . . . . . . . 14
4.5. Distinguishing SETs from ID Tokens . . . . . . . . . . . 14
4.6. Distinguishing SETs from Access Tokens . . . . . . . . . 15
4.7. Distinguishing SETs from other kinds of JWTs . . . . . . 15
5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 16
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
6.1. JSON Web Token Claims Registration . . . . . . . . . . . 16
6.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 17
6.2. Media Type Registration . . . . . . . . . . . . . . . . . 17
6.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 17
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.1. Normative References . . . . . . . . . . . . . . . . . . 18
7.2. Informative References . . . . . . . . . . . . . . . . . 19
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 20
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
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].
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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:
o The creation, modification, removal of a resource.
o The resetting or suspension of an account.
o The revocation of a security token prior to its expiry.
o The logout of a user session. Or,
o 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.
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 actions, 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.
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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", "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
The following definitions are used with SETs:
Security Event Token (SET)
A SET is a JWT [RFC7519] that is distributed to one or more
registered Event Receivers.
Event Transmitter
A service provider that delivers SETs to other providers known as
Event Receivers.
Event Receiver
An Event Receiver is an entity that receives SETs through some
distribution method.
Subject
A SET describes an event or state change that has occurred about a
Subject. A Subject may be a principal (e.g., Section 4.1.2
[RFC7519]), a web resource, an entity such as an IP address, or
the issuer itself that a SET might reference.
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Profiling Specification A specification that uses the SET Token
specification to define one or more event types and the associated
claims included.
2. The Security Event Token (SET)
A SET is a data structure (in the form of a JWT [RFC7519])
representing one or more related security events about a Subject.
The schema and structure of a SET follows the JWT [RFC7519]
specification. A SET has the following structure:
o An outer JSON object 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 Events within a single Profiling Specification or a
related series of specifications. Claims in the envelope (the
outer JSON structure) SHOULD be registered in the JWT Token Claims
Registry Section 10.1 [RFC7519] or be Public Claims or Private
Claims as also defined in [RFC7519].
o Envelope claims that are profiled and defined in this
specification are used to validate a SET and declare the contents
of the event data included in the SET. The claim "events"
identifies the event types expressed that are related to the
Security Subject and MAY also include event-specific data.
o Each JSON member of the "events" object is a name and value pair.
The JSON attribute name is a URI String value that expresses an
event type, and 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 Profiling Specification. An event with no payload
claims SHALL be represented as the empty JSON object ("{}"). 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:
* A categorization event type to provide classification
information (e.g., threat type or level).
* An enhancement of an existing specifications the arise over
time.
* An extension needed to link a potential series of events.
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* Localized specific purpose event URI used between a particular
Event Transmitter and Receiver.
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:
o 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.
o An "iss" claim, denoting the Event Transmitter.
o The "sub" claim specifies the SCIM resource URI that was affected.
o 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
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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
Note that the above SET has an empty JSON object and uses the JWT
registered claims "sub" and "sid" to identify the subject that was
logged-out.
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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
In the above example, the attribute "iss" contained within the
payload for the event "https://openid.net/heart/specs/consent.html"
refers to the issuer of the Security Subject ("sub") rather than the
event issuer "https://my.examplemed.com". They are distinct from the
top level value of "iss", which always refers to the issuer of the
event - a medical consent service that is a relying party to the
OpenID Provider.
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
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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 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. Note that
some SET profiles MAY choose to convey event subject information
in the event payload, particularly if the subject information is
relative to issuer information that is also conveyed in the event
payload, which may be the case for some identity SET profiles.
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.
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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. Explicit Typing of SETs
This specification registers the "application/secevent+jwt" media
type, which can be used to indicate that the content is a SET. SETs
MAY include this media type in the "typ" header parameter of the JWT
representing the SET to explicitly declare that the JWT is a SET.
This MUST be included if the SET could be used in an application
context in which it could be confused with other kinds of JWTs.
Per the definition of "typ" in Section 4.1.9 of [RFC7515], it is
RECOMMENDED that the "application/" prefix be omitted. Therefore,
the "typ" value used SHOULD be "secevent+jwt".
2.3. 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.
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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 JOSE Header is:
{"typ":"secevent+jwt","alg":"none"}
Base64url encoding of the octets of the UTF-8 representation of the
JOSE Header yields:
eyJ0eXAiOiJzZWNldmVudCtqd3QiLCJhbGciOiJub25lIn0
The example JWT Claims Set is encoded as follows:
eyJqdGkiOiI0ZDM1NTllYzY3NTA0YWFiYTY1ZDQwYjAzNjNmYWFkOCIsImlhdCI6MTQ1
ODQ5NjQwNCwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbImh0
dHBzOi8vc2NpbS5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M2I3
NzU0IiwiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIxZDA4
NjQxZDc2NzZlZTciXSwiZXZlbnRzIjp7InVybjppZXRmOnBhcmFtczpzY2ltOmV2ZW50
OmNyZWF0ZSI6eyJyZWYiOiJodHRwczovL3NjaW0uZXhhbXBsZS5jb20vVXNlcnMvNDRm
NjE0MmRmOTZiZDZhYjYxZTc1MjFkOSIsImF0dHJpYnV0ZXMiOlsiaWQiLCJuYW1lIiwi
dXNlck5hbWUiLCJwYXNzd29yZCIsImVtYWlscyJdfX19
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The encoded JWS signature is the empty string. Concatenating the
parts yields:
eyJ0eXAiOiJzZWNldmVudCtqd3QiLCJhbGciOiJub25lIn0.
eyJqdGkiOiI0ZDM1NTllYzY3NTA0YWFiYTY1ZDQwYjAzNjNmYWFkOCIsImlhdCI6MTQ1
ODQ5NjQwNCwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbImh0
dHBzOi8vc2NpbS5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M2I3
NzU0IiwiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIxZDA4
NjQxZDc2NzZlZTciXSwiZXZlbnRzIjp7InVybjppZXRmOnBhcmFtczpzY2ltOmV2ZW50
OmNyZWF0ZSI6eyJyZWYiOiJodHRwczovL3NjaW0uZXhhbXBsZS5jb20vVXNlcnMvNDRm
NjE0MmRmOTZiZDZhYjYxZTc1MjFkOSIsImF0dHJpYnV0ZXMiOlsiaWQiLCJuYW1lIiwi
dXNlck5hbWUiLCJwYXNzd29yZCIsImVtYWlscyJdfX19.
Figure 5: Example Unsecured Security Event Token
For the purpose of a simpler example in Figure 5, an unsecured token
was shown. When SETs are not signed or encrypted, the Event Receiver
MUST employ other mechanisms such as TLS and HTTP to provide
integrity, confidentiality, and issuer validation, as needed by the
application.
When validation (i.e. auditing), or additional transmission security
is required, JWS signing and/or JWE encryption MAY be used. To
create and or validate a signed and/or encrypted SET, follow the
instructions in Section 7 of [RFC7519].
3. Requirements for SET Profiles
Profile Specifications for SETs define the syntax and semantics of
SETs conforming to that SET profile and rules for validating those
SETs. The syntax defined by profiling specifications includes what
claims and event payload values are used by SETs utilizing the
profile.
Defining the semantics of the SET contents for SETs utilizing the
profile is equally important. Possibly most important is defining
the procedures used to validate the SET issuer and to obtain the keys
controlled by the issuer that were used for cryptographic operations
used in the JWT representing the SET. For instance, some profiles
may define an algorithm for retrieving the SET issuer's keys that
uses the "iss" claim value as its input.
Profile Specifications MUST clearly specify the steps that a
recipient of a SET utilizing that profile MUST perform to validate
that the SET is both syntactically and semantically valid.
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4. Security Considerations
4.1. 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 OAuth 2.0
[RFC6749], or Basic Authentication [RFC7617], MUST be signed using
JWS [RFC7515] so that individual events can be authenticated and
validated by the Event Receiver.
4.2. 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.
4.3. 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
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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.
4.4. 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.
4.5. Distinguishing SETs from ID 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 with ID Token [OpenID.Core] if a SET is
mistakenly or intentionally used in a context requiring an ID Token.
If a SET could otherwise be interpreted as a valid ID Token (because
it includes the required claims for an ID Token and valid issuer and
audience claim values for an ID Token) then that SET profile MUST
require that the "exp" claim not be present in the SET. Because
"exp" is a required claim in ID Tokens, valid ID Token
implementations will reject such a SET if presented as if it were an
ID Token.
Excluding "exp" from SETs that could otherwise be confused with ID
Tokens is actually defense in depth. In any OpenID Connect contexts
in which an attacker could attempt to substitute a SET for an ID
Token, the SET would actually already be rejected as an ID Token
because it would not contain the correct "nonce" claim value for the
ID Token to be accepted in that context.
Note that the use of explicit typing, as described in Section 2.2,
will not achieve disambiguation between ID Tokens and SETs, as the ID
Token validation rules do not use the "typ" header parameter value.
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4.6. Distinguishing SETs from Access Tokens
OAuth 2.0 [RFC6749] defines access tokens as being opaque.
Nonetheless, some implementations implement access tokens as JWTs.
Because the structure of these JWTs is implementation-specific,
ensuring that a SET cannot be confused with such an access token is
therefore likewise, in general, implementation specific.
Nonetheless, it is recommended that SET profiles employ the following
strategies to prevent possible substitutions of SETs for access
tokens in contexts in which that might be possible:
o Prohibit use of the "exp" claim, as is done to prevent ID Token
confusion.
o Where possible, use a separate "aud" claim value to distinguish
between the SET subscriber and the protected resource that is the
audience of an access token.
o Modify access token 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.
o Employ explicit typing, as described in Section 2.2, and modify
access token validation systems to use the "typ" header parameter
value.
4.7. Distinguishing SETs from other kinds of JWTs
JWTs are now being used in application areas beyond the identity
applications in which they first appeared. For instance, the Session
Initiation Protocol (SIP) Via Header Field [RFC8055] and Personal
Assertion Token (PASSporT) [I-D.ietf-stir-passport] specifications
both define JWT profiles that use mostly or completely different sets
of claims than are used by ID Tokens. If it would otherwise be
possible for an attacker to substitute a SET for one of these (or
other) kinds of JWTs, then the SET profile must be defined in such a
way that any substituted SET will result in its rejection when
validated as the intended kind of JWT.
The most direct way to ensure that a SET is not confused with another
kind of JWT is to have the JWT validation logic reject JWTs
containing an "events" claim unless the JWT is intended to be a SET.
This approach can be employed for new systems but may not be
applicable to existing systems.
Another direct way to prevent confusion is to employ explicit typing,
as described in Section 2.2, and modify applicable token validation
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systems to use the "typ" header parameter value. This approach can
be employed for new systems but may not be applicable to existing
systems.
For many use cases, the simplest way to prevent substitution is
requiring that the SET not include claims that are required for the
kind of JWT that might be the target of an attack. For example, for
[RFC8055], the "sip_callid" claim could be omitted and for
[I-D.ietf-stir-passport], the "orig" claim could be omitted.
In many contexts, simple measures such as these will accomplish the
task, should confusion otherwise even be possible. Note that this
topic is being explored in a more general fashion in JSON Web Token
Best Current Practices [I-D.sheffer-oauth-jwt-bcp]. The proposed
best practices in that draft may also be applicable for particular
SET profiles and use cases.
5. Privacy Considerations
If a SET needs to be retained for audit purposes, JWS MAY be used to
provide verification of its authenticity.
Event Transmitters SHOULD attempt to specialize 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.
6. IANA Considerations
6.1. 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].
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6.1.1. Registry Contents
o Claim Name: "events"
o Claim Description: Security Event Object
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]]
o Claim Name: "txn"
o Claim Description: Transaction Identifier
o Change Controller: IESG
o Specification Document(s): Section 2 of [[ this specification ]]
6.2. Media Type Registration
6.2.1. Registry Contents
This section registers the "application/secevent+jwt" media type
[RFC2046] in the "Media Types" registry [IANA.MediaTypes] in the
manner described in [RFC6838], which can be used to indicate that the
content is a SET.
o Type name: application
o Subtype name: secevent+jwt
o Required parameters: n/a
o Optional parameters: n/a
o Encoding considerations: 8bit; A SET is a JWT; JWT values are
encoded as a series of base64url-encoded values (some of which may
be the empty string) separated by period ('.') characters.
o Security considerations: See the Security Considerations section
of [[ this specification ]]
o Interoperability considerations: n/a
o Published specification: Section 2.2 of [[ this specification ]]
o Applications that use this media type: TBD
o Fragment identifier considerations: n/a
o Additional information:
Magic number(s): n/a
File extension(s): n/a
Macintosh file type code(s): n/a
o Person & email address to contact for further information:
Michael B. Jones, mbj@microsoft.com
o Intended usage: COMMON
o Restrictions on usage: none
o Author: Michael B. Jones, mbj@microsoft.com
o Change controller: IESG
o Provisional registration? No
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7. References
7.1. Normative References
[IANA.JWT.Claims]
IANA, "JSON Web Token Claims",
<http://www.iana.org/assignments/jwt>.
[IANA.MediaTypes]
IANA, "Media Types",
<http://www.iana.org/assignments/media-types>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>.
[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, <http://www.rfc-editor.org/info/rfc6125>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<http://www.rfc-editor.org/info/rfc6749>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<http://www.rfc-editor.org/info/rfc7519>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <http://www.rfc-editor.org/info/rfc7525>.
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[RFC7617] Reschke, J., "The 'Basic' HTTP Authentication Scheme",
RFC 7617, DOI 10.17487/RFC7617, September 2015,
<http://www.rfc-editor.org/info/rfc7617>.
7.2. Informative References
[I-D.ietf-stir-passport]
Wendt, C. and J. Peterson, "Personal Assertion Token
(PASSporT)", draft-ietf-stir-passport-11 (work in
progress), February 2017.
[I-D.sheffer-oauth-jwt-bcp]
Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
Current Practices", draft-sheffer-oauth-jwt-bcp-00 (work
in progress), June 2017.
[OpenID.Core]
Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
C. Mortimore, "OpenID Connect Core 1.0", November 2014,
<http://openid.net/specs/openid-connect-core-1_0.html>.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
DOI 10.17487/RFC2046, November 1996,
<http://www.rfc-editor.org/info/rfc2046>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<http://www.rfc-editor.org/info/rfc6838>.
[RFC7009] Lodderstedt, T., Ed., Dronia, S., and M. Scurtescu, "OAuth
2.0 Token Revocation", RFC 7009, DOI 10.17487/RFC7009,
August 2013, <http://www.rfc-editor.org/info/rfc7009>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <http://www.rfc-editor.org/info/rfc7515>.
[RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015,
<http://www.rfc-editor.org/info/rfc7516>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<http://www.rfc-editor.org/info/rfc7517>.
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[RFC7644] Hunt, P., Ed., Grizzle, K., Ansari, M., Wahlstroem, E.,
and C. Mortimore, "System for Cross-domain Identity
Management: Protocol", RFC 7644, DOI 10.17487/RFC7644,
September 2015, <http://www.rfc-editor.org/info/rfc7644>.
[RFC8055] Holmberg, C. and Y. Jiang, "Session Initiation Protocol
(SIP) Via Header Field Parameter to Indicate Received
Realm", RFC 8055, DOI 10.17487/RFC8055, January 2017,
<http://www.rfc-editor.org/info/rfc8055>.
[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 IETF SCIM working
group, 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
General edit corrections from Sarah Squire
Changed "event" term to "SET"
Corrected author organization for William Denniss to Google
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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 "events" claim, and proof-reading corrections.
Draft 04 - PH -
o Re-added the "sub" claim with clarifications that any SET type may
use it.
o Added additional clarification on the use of envelope vs. payload
attributes
o Added security consideration for event timing.
o Switched use of "attribute" to "claim" for consistency.
o Revised examples to put "sub" claim back in the top level.
o Added clarification that SETs typically do not use "exp".
o 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 -
o Corrected typos
o New txn claim
o New security considerations Sequencing and Timing Issues
Draft 07 -
o PH - Moved payload objects to be values of event URI attributes,
per discussion.
o mbj - Applied terminology consistency and grammar cleanups.
Draft 08 - PH -
o Added clarification to status of examples
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o 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).
o 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:
o Changed terminology away from pub-sub to transmitter/receiver
based on WG feedback
o Cleaned up/removed some text about extensions (now only used as
example)
o Clarify purpose of spec vs. future profiling specs that define
actual events
Draft 02 - Changes are as follows:
o mbj - Added the Requirements for SET Profiles section.
o mbj - Expanded the Security Considerations section to describe how
to prevent confusion of SETs with ID Tokens, access tokens, and
other kinds of JWTs.
o mbj - Registered the "application/secevent+jwt" media type and
defined how to use it for explicit typing of SETs.
o mbj - Clarified the misleading statement that used to say that a
SET conveys a single security event.
o mbj - Added a note explicitly acknowledging that some SET profiles
may choose to convey event subject information in the event
payload.
o PH - Corrected encoded claim example on page 10.
o mbj - Applied grammar corrections.
Authors' Addresses
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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/
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