Security Event Token (SET)Oracle Corporationphil.hunt@yahoo.comGooglewdenniss@google.comCiscomorteza.ansari@cisco.comMicrosoftmbj@microsoft.comhttp://self-issued.info/
Security
Security Events Working GroupIdentitySecurityEventTokenInternet-DraftThis 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 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
in order to provide a self-contained token that can be optionally
signed using JSON Web Signature (JWS)
and/or encrypted using JSON Web Encryption (JWE) .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:
The creation, modification, removal of a resource.The resetting or suspension of an account.The revocation of a security token prior to its expiry.The logout of a user session. Or, 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.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. 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 . 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.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.
The following definitions are used with SETs:
A SET is a JWT that is
distributed to one or more registered Event Receivers.
A service provider that delivers SETs to other providers known
as Event Receivers.
An Event Receiver is an entity that receives SETs through
some distribution method.
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), a web resource,
an entity such as an IP address, or the issuer itself that
a SET might reference.
A specification that
uses the SET Token specification to define one or more event
types and the associated claims included.
A SET is a data structure (in the form of a JWT
) representing one or more related security events
about a Subject.The schema and structure of a SET follows the JWT
specification. A SET has the following structure:
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 or be
Public Claims or Private Claims as also defined in .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.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.Localized specific purpose event URI used between a
particular Event Transmitter and Receiver.The event in the figure above expresses hypothetical password
reset event for SCIM . 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.
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.
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.
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.
The following are claims that are based on
claim definitions and are profiled for use in an event
token:As defined by
Section 4.1.7 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.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). The syntax of the
claim is as defined in Section 4.1.3.
This claim contains one or more audience identifiers
for the SET. This claim is RECOMMENDED.As defined by Section 4.1.6,
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.
Defined by
Section 4.1.5, 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.As defined by Section 4.1.2,
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.
As defined by , 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:
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.
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.
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 ,
it is RECOMMENDED that the "application/" prefix be omitted.
Therefore, the typ value used SHOULD be
secevent+jwt.
A SET is a JWT 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.When transmitted, the above JSON body must be converted into a JWT
as per .For the purpose of a simpler example in ,
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 .
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.
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 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 . Implementation
security considerations for TLS can be found in "Recommendations for
Secure Use of TLS and DTLS" .Security Events distributed through third-parties or that carry personally
identifiable information, SHOULD be encrypted using JWE
or secured for confidentiality by other means.
Security Events distributed without authentication over the channel, such
as via TLS ( and ),
and/or OAuth 2.0 , or Basic Authentication ,
MUST be signed using JWS so
that individual events can be authenticated and validated by the
Event Receiver.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.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.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.
Because 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
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 ,
will not achieve disambiguation between ID Tokens and SETs, as the ID Token validation rules
do not use the typ header parameter value.
OAuth 2.0 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:
Prohibit use of the exp claim,
as is done to prevent ID Token confusion.
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.
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.
Employ explicit typing, as described in ,
and modify access token validation systems to use the
typ header parameter value.
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
and
Personal Assertion Token (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 ,
and modify applicable token validation 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 ,
the sip_callid claim could be omitted
and for ,
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 .
The proposed best practices in that draft may also be applicable
for particular SET profiles and use cases.
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.
This specification registers the events and
txn claims in the IANA
"JSON Web Token Claims" registry
established by .
Claim Name: events
Claim Description: Security Event Object
Change Controller: IESG
Specification Document(s): of [[ this specification ]]
Claim Name: txn
Claim Description: Transaction Identifier
Change Controller: IESG
Specification Document(s): of [[ this specification ]]
This section registers the application/secevent+jwt
media type
in the "Media Types" registry
in the manner described in ,
which can be used to indicate that the content is a SET.
Type name: application
Subtype name: secevent+jwt
Required parameters: n/a
Optional parameters: n/a
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.
Security considerations: See the Security Considerations section of [[ this specification ]]
Interoperability considerations: n/a
Published specification: of [[ this specification ]]
Applications that use this media type:
TBD
Fragment identifier considerations: n/a
Additional information:Magic number(s): n/aFile extension(s): n/aMacintosh file type code(s): n/a
Person & email address to contact for further information:
Michael B. Jones, mbj@microsoft.com
Intended usage: COMMON
Restrictions on usage: none
Author: Michael B. Jones, mbj@microsoft.com
Change controller: IESG
Provisional registration? No
JSON Web Token ClaimsIANAMedia TypesIANAOpenID Connect Core 1.0Nomura Research Institute, Ltd.Ping IdentityMicrosoftGoogleSalesforceAssertions and Protocols for the OASIS Security Assertion Markup Language (SAML) V2.0Internet2The 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.From the original draft-hunt-idevent-token:Draft 01 - PH - Renamed eventUris to eventsDraft 00 - PH - First DraftDraft 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 SquireChanged "event" term to "SET"Corrected author organization for William Denniss to GoogleChanged 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 - Re-added the "sub" claim with clarifications that any SET type may use it.Added additional clarification on the use of envelope vs. payload attributesAdded 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 claimcDraft 06 - PH - Corrected typosNew txn claimNew 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 examplesChanged 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-tokenDraft 01 - PH - Changes as follows:Changed terminology away from pub-sub to transmitter/receiver based on WG feedbackCleaned up/removed some text about extensions (now only used as example)Clarify purpose of spec vs. future profiling specs that define actual events
Draft 02 - Changes are as follows:
mbj -
Added the Requirements for SET Profiles section.
mbj -
Expanded the Security Considerations section to describe
how to prevent confusion of SETs with ID Tokens, access tokens,
and other kinds of JWTs.
mbj -
Registered the application/secevent+jwt media type
and defined how to use it for explicit typing of SETs.
mbj -
Clarified the misleading statement that used to say that
a SET conveys a single security event.
mbj -
Added a note explicitly acknowledging that some SET profiles
may choose to convey event subject information in the event payload.
PH -
Corrected encoded claim example on page 10.
mbj -
Applied grammar corrections.