Security Events Working Group P. Hunt, Ed.
Internet-Draft Oracle
Intended status: Standards Track M. Jones
Expires: October 19, 2018 Microsoft
W. Denniss
Google
M. Ansari
Cisco
April 17, 2018
Security Event Token (SET)
draft-ietf-secevent-token-09
Abstract
This specification defines the Security Event Token (SET) data
structure. A SET describes statements of fact from the perspective
of an issuer about a subject. These statements of fact represent an
event that occurred directly to or about a security subject, for
example, a statement about the issuance or revocation of a token on
behalf of a subject. This specification is intended to enable
representing security- and identity-related events. A SET is a JSON
Web Token (JWT), which can be optionally signed and/or encrypted.
SETs can be distributed via protocols such as HTTP.
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 https://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 October 19, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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Table of Contents
1. Introduction and Overview . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4
1.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . 4
2. The Security Event Token (SET) . . . . . . . . . . . . . . . 5
2.1. Illustrative Examples . . . . . . . . . . . . . . . . . . 6
2.1.1. SCIM Example . . . . . . . . . . . . . . . . . . . . 6
2.1.2. Logout Example . . . . . . . . . . . . . . . . . . . 8
2.1.3. Consent Example . . . . . . . . . . . . . . . . . . . 8
2.1.4. RISC Example . . . . . . . . . . . . . . . . . . . . 9
2.2. Core SET Claims . . . . . . . . . . . . . . . . . . . . . 10
2.3. Explicit Typing of SETs . . . . . . . . . . . . . . . . . 12
2.4. Security Event Token Construction . . . . . . . . . . . . 13
3. Requirements for SET Profiles . . . . . . . . . . . . . . . . 14
4. Preventing Confusion between SETs and other JWTs . . . . . . 15
4.1. Distinguishing SETs from ID Tokens . . . . . . . . . . . 16
4.2. Distinguishing SETs from Access Tokens . . . . . . . . . 16
4.3. Distinguishing SETs from other kinds of JWTs . . . . . . 17
5. Security Considerations . . . . . . . . . . . . . . . . . . . 17
5.1. Confidentiality and Integrity . . . . . . . . . . . . . . 18
5.2. Delivery . . . . . . . . . . . . . . . . . . . . . . . . 18
5.3. Sequencing . . . . . . . . . . . . . . . . . . . . . . . 18
5.4. Timing Issues . . . . . . . . . . . . . . . . . . . . . . 19
5.5. Preventing Confusion . . . . . . . . . . . . . . . . . . 19
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 19
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
7.1. JSON Web Token Claims Registration . . . . . . . . . . . 20
7.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 20
7.2. Media Type Registration . . . . . . . . . . . . . . . . . 20
7.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 20
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1. Normative References . . . . . . . . . . . . . . . . . . 21
8.2. Informative References . . . . . . . . . . . . . . . . . 22
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 24
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
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1. Introduction and Overview
This specification defines an extensible Security Event Token (SET)
data structure, which can 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 used by profiling specifications to define actual events and
their meanings. This specification uses non-normative example events
to demonstrate how events can 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 SET
describes statements of fact from the perspective of an issuer about
a subject (e.g., a web resource, token, IP address, the issuer
itself). These statements of fact represent a logical event that
occurred directly to or about a security subject, for example, a
statement about the issuance or revocation of a token on behalf of a
subject. 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 An indication that a user has been given control of an email
identifier that was previously controlled by another user.
While subject state changes are often triggered by a user agent or
security subsystem, the issuance and transmission of an event may
occur asynchronously and in a back channel to the action that caused
the change that generated the security event. Subsequently, a SET
recipient, having received a SET, validates and interprets the
received SET and takes its own independent actions, if any. For
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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 SET recipient may choose to
ensure that the new user is not granted access to resources
associated with the previous user. Or, the SET recipient may not
have any relationship with the subject, and no action is taken.
While SET recipients will often take actions upon receiving SETs,
security events cannot be assumed to be commands or requests. The
intent of this specification is to define a syntax for statements of
fact that SET recipients may interpret for their own purposes.
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 BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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] conforming to this specification.
SET Issuer
A service provider that creates SETs to be sent to other service
providers known as SET recipients.
SET Recipient
A SET recipient is an entity that receives SETs through some
distribution method. A SET recipient is the same entity referred
as a "recipient" in [RFC7519] or "receiver" in related
specifications.
Subject
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A SET describes an event or state change that has occurred to a
subject. A subject might, for instance, be a principal (e.g.,
Section 4.1.2 of [RFC7519]), a web resource, an entity such as an
IP address, or the issuer of the SET.
Event Identifier
A member name for an element of the JSON object that is the value
of the "events" claim in a SET. This member name MUST be a URI.
Event Payload
A member value for an element of the JSON object that is the value
of the "events" claim in a SET. This member value MUST be a JSON
object.
Profiling Specification
A specification that profiles the SET data structure to define one
or more specific event types and their associated claims and
processing rules.
2. The Security Event Token (SET)
A SET is a JWT [RFC7519] data structure that represents one or more
related aspects of a security event that occurred to a subject. The
JWT Claims Set in a SET has the following structure:
o The top-level claims in the JWT Claims Set are called the SET
"envelope". Some of these claims are present in every SET; others
will be specific to particular SET profiles or profile families.
Claims in the envelope SHOULD be registered in the "JSON Web Token
Claims" registry [IANA.JWT.Claims] or be Public Claims or Private
Claims, as defined in [RFC7519].
o Envelope claims that are profiled and defined in this
specification are used to validate the SET and provide information
about the event data included in the SET. The claim "events"
contains the event identifiers and event-specific data expressed
about the security subject. The envelope MAY include event-
specific or profile-specific data. The "events" claim value MUST
be a JSON object that contains at least one member.
o Each member of the "events" JSON object is a name/value pair. The
JSON member name is a URI string value, which is the event
identifier, and the corresponding value is a JSON object known as
the event "payload". The payload JSON object contains claims that
pertain to that event identifier and need not be registered as JWT
claims. These claims are defined by the profiling specification
that defines the event. An event with no payload claims SHALL be
represented as the empty JSON object ("{}").
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o When multiple event identifiers are contained in a SET, they
represent multiple aspects of the same state transition that
occurred to the security subject. They are not intended to be
used to aggregate distinct events about the same subject. Beyond
this, the interpretation of SETs containing multiple event
identifiers is out of scope for this specification; profiling
specifications MAY define their own rules regarding their use of
SETs containing multiple event identifiers, as described in
Section 3. Possible uses of multiple values include, but are not
limited to:
* Values to provide classification information (e.g., threat type
or level).
* Additions to existing event representations.
* Values used to link potential series of events.
* Specific-purpose event URIs used between particular SET issuers
and SET recipients.
2.1. Illustrative Examples
This section illustrates several possible uses of SETs through non-
normative examples.
2.1.1. SCIM Example
The following example shows the JWT Claims Set for a hypothetical
SCIM [RFC7644] password reset SET. Such a SET might be used by a
receiver as a trigger to reset active user-agent sessions related to
the identified user.
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{
"iss": "https://scim.example.com",
"iat": 1458496025,
"jti": "3d0c3cf797584bd193bd0fb1bd4e7d30",
"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 JWT Claims Set usage consists of:
o The "events" claim specifying the hypothetical SCIM URN
("urn:ietf:params:scim:event:passwordReset") for a password reset,
and a second value, "https://example.com/scim/event/
passwordResetExt", that is used to provide additional event
information such as the current count of resets.
o The "iss" claim, denoting the SET issuer.
o The "sub" claim, specifying the SCIM resource URI that was
affected.
o The "aud" claim, specifying the intended audiences for the event.
(The syntax of the "aud" claim is defined in Section 4.1.3 of
[RFC7519].)
The SET contains two event payloads:
o The "id" claim represents SCIM's unique identifier for a subject.
o The second payload identified by "https://example.com/scim/event/
passwordResetExt") and the payload claim "resetAttempts" conveys
the current count of reset attempts. In this example, while the
count is a simple factual statement for the issuer, the meaning of
the value (a count) is up to the receiver. As an example, such a
value might be used by the receiver to infer increasing risk.
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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 in the event payload of an event used to
convey this information.
2.1.2. Logout Example
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
claims "sub" and "sid" to identify the subject that was logged out.
At the time of this writing, this example corresponds to the logout
token defined in the OpenID Connect Back-Channel Logout 1.0
[OpenID.BackChannel] specification.
2.1.3. Consent Example
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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:
{
"iss": "https://my.med.example.org",
"iat": 1458496025,
"jti": "fb4e75b5411e4e19b6c0fe87950f7749",
"aud": [
"https://rp.example.com"
],
"events": {
"https://openid.net/heart/specs/consent.html": {
"iss": "https://connect.example.com",
"sub": "248289761001",
"consentUri": [
"https://terms.med.example.org/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
SET issuer "https://my.med.example.org". 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.
2.1.4. RISC Example
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The following example JWT Claims Set is for an account disabled
event. This example was taken from a working draft of the RISC
events specification, where RISC is the OpenID RISC (Risk and
Incident Sharing and Coordination) working group [RISC]. The example
is subject to change.
{
"iss": "https://idp.example.com/",
"jti": "756E69717565206964656E746966696572",
"iat": 1508184845,
"aud": "636C69656E745F6964",
"events": {
"http://schemas.openid.net/secevent/risc/event-type/\
account-disabled": {
"subject": {
"subject_type": "iss-sub",
"iss": "https://idp.example.com/",
"sub": "7375626A656374"
},
"reason": "hijacking",
"cause-time": 1508012752
}
}
}
Figure 4: Example RISC Event
Notice that parameters to the event are included in the event
payload, in this case, the "reason" and "cause-time" values. The
subject of the event is identified using the "subject" payload value,
which itself is a JSON object.
2.2. Core SET Claims
The following claims from [RFC7519] are profiled for use in SETs:
"iss" (Issuer) Claim
As defined by Section 4.1.1 of [RFC7519], this claim contains a
string identifying the service provider publishing the SET (the
issuer). In some cases, the SET issuer is not the issuer of the
security subject. Therefore, implementers cannot assume that the
issuers are the same unless the profiling specification specifies
that they are for SETs conforming to that profile. This claim is
REQUIRED.
"iat" (Issued At) Claim
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As defined by Section 4.1.6 of [RFC7519], this claim contains a
value representing when the SET was issued. This claim is
REQUIRED.
"jti" (JWT ID) Claim
As defined by Section 4.1.7 of [RFC7519], this claim contains a
unique identifier for the SET. The identifier MUST be unique
within a particular event feed and MAY be used by clients to track
whether a particular SET has already been received. This claim is
REQUIRED.
"aud" (Audience) Claim
As defined by Section 4.1.3 of [RFC7519], this claim contains one
or more audience identifiers for the SET. This claim is
RECOMMENDED.
"sub" (Subject) Claim
As defined by Section 4.1.2 of [RFC7519], this claim contains a
StringOrURI value representing the principal that is 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; or,
* a token identifier (e.g. "jti") for a revoked token.
If used, the profiling 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
(either using the "sub" member name or another name), 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" (Expiration Time) Claim
As defined by Section 4.1.4 of [RFC7519], this claim is the time
after which the JWT MUST NOT be accepted for processing. In the
context of a SET however, this notion does not typically apply,
since a SET represents something that has already occurred and is
historical in nature. Therefore, its use is NOT RECOMMENDED.
(Also, see Section 4.1 for additional reasons not to use the "exp"
claim in some SET use cases.)
The following new claims are defined by this specification:
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"events" (Security Events) Claim
This claim contains a set of event statements that each provide
information describing a single logical event that has occurred
about a security subject (e.g., a state change to the subject).
Multiple event identifiers with the same value MUST NOT be used.
The "events" claim MUST NOT be used to express multiple
independent logical events.
The value of the "events" claim is a JSON object whose members are
name/value pairs whose names are URIs identifying the event
statements being expressed. Event identifiers SHOULD be stable
values (e.g., a permanent URL for an event specification). For
each name present, the corresponding value MUST be a JSON object.
The JSON object MAY be an empty object ("{}"), or it MAY be a JSON
object containing data described by the profiling specification.
"txn" (Transaction Identifier) Claim
An OPTIONAL string value that represents a unique transaction
identifier. In cases in which multiple related JWTs are issued,
the transaction identifier claim can be used to correlate these
related JWTs. Note that this claim can be used in JWTs that are
SETs and also in JWTs using non-SET profiles.
"toe" (Time of Event) Claim
A value that represents the date and time at which the event
occurred. This value is a NumericDate (see Section 2 of
[RFC7519]). By omitting this claim, the issuer indicates that
they are not sharing an event time with the recipient. (Note that
in some use cases, the represented time might be approximate;
statements about the accuracy of this field MAY be made by
profiling specifications.) This claim is OPTIONAL.
2.3. 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".
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2.4. Security Event Token Construction
This section describes how to construct a SET.
The following is an example JWT Claims Set for a hypothetical SCIM
SET (which has been formatted for readability):
{
"iss": "https://scim.example.com",
"iat": 1458496404,
"jti": "4d3559ec67504aaba65d40b0363faad8",
"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 5: Example Event Claims
The JSON Claims Set is encoded per [RFC7519].
In this example, the SCIM SET claims are encoded in an unsecured JWT.
The JOSE Header for this example is:
{"typ":"secevent+jwt","alg":"none"}
Base64url encoding of the octets of the UTF-8 representation of the
JOSE Header yields:
eyJ0eXAiOiJzZWNldmVudCtqd3QiLCJhbGciOiJub25lIn0
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The above example JWT Claims Set is encoded as follows:
eyJqdGkiOiI0ZDM1NTllYzY3NTA0YWFiYTY1ZDQwYjAzNjNmYWFkOCIsImlhdCI6MTQ1
ODQ5NjQwNCwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbImh0
dHBzOi8vc2NpbS5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M2I3
NzU0IiwiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIxZDA4
NjQxZDc2NzZlZTciXSwiZXZlbnRzIjp7InVybjppZXRmOnBhcmFtczpzY2ltOmV2ZW50
OmNyZWF0ZSI6eyJyZWYiOiJodHRwczovL3NjaW0uZXhhbXBsZS5jb20vVXNlcnMvNDRm
NjE0MmRmOTZiZDZhYjYxZTc1MjFkOSIsImF0dHJpYnV0ZXMiOlsiaWQiLCJuYW1lIiwi
dXNlck5hbWUiLCJwYXNzd29yZCIsImVtYWlscyJdfX19
The encoded JWS signature is the empty string. Concatenating the
parts yields this complete SET:
eyJ0eXAiOiJzZWNldmVudCtqd3QiLCJhbGciOiJub25lIn0.
eyJqdGkiOiI0ZDM1NTllYzY3NTA0YWFiYTY1ZDQwYjAzNjNmYWFkOCIsImlhdCI6MTQ1
ODQ5NjQwNCwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbImh0
dHBzOi8vc2NpbS5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M2I3
NzU0IiwiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIxZDA4
NjQxZDc2NzZlZTciXSwiZXZlbnRzIjp7InVybjppZXRmOnBhcmFtczpzY2ltOmV2ZW50
OmNyZWF0ZSI6eyJyZWYiOiJodHRwczovL3NjaW0uZXhhbXBsZS5jb20vVXNlcnMvNDRm
NjE0MmRmOTZiZDZhYjYxZTc1MjFkOSIsImF0dHJpYnV0ZXMiOlsiaWQiLCJuYW1lIiwi
dXNlck5hbWUiLCJwYXNzd29yZCIsImVtYWlscyJdfX19.
Figure 6: Example Unsecured Security Event Token
For the purpose of having a simpler example in Figure 6, an unsecured
token is shown. When SETs are not signed or encrypted, other
mechanisms such as TLS MUST be employed to provide integrity
protection, confidentiality, and issuer authenticity, 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
Profiling specifications of this specification define actual SETs to
be used in particular use cases. These profiling specifications
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
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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. Likewise, if the profile
allows (or requires) that the JWT be unsecured, the means by which
the integrity of the JWT is ensured MUST be specified.
Profiling specifications MUST define how the event subject is
identified in the SET, as well as how to differentiate between the
event subject's issuer and the SET issuer, if applicable. It is NOT
RECOMMENDED for profiling specifications to use the "sub" claim in
cases in which the subject is not globally unique and has a different
issuer from the SET itself.
Among the syntax and semantics of SETs that a profiling specification
may define is whether the value of the "events" claim may contain
multiple members, and what processing instructions are employed in
the single- and multiple-valued cases for SETs conforming to that
profile. Many valid choices are possible. For instance, some
profiles might allow multiple event identifiers to be present and
specify that any that are not understood by recipients be ignored,
thus enabling extensibility. Other profiles might allow multiple
event identifiers to be present but require that all be understood if
the SET is to be accepted. Some profiles might require that only a
single value be present. All such choices are within the scope of
profiling specifications to define.
Profiling 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.
4. Preventing Confusion between SETs and other JWTs
Because [RFC7519] states that "all claims that are not understood by
implementations MUST be ignored", there is a consideration that a SET
might be confused with another kind of JWT from the same issuer.
Unless this confusion is prevented, this might enable an attacker who
possesses a SET to use it in a context in which another kind of JWT
is expected, or vice-versa. This section presents concrete
techniques for preventing confusion between SETs and several other
specific kinds of JWTs, as well as generic techniques for preventing
possible confusion between SETs and other kinds of JWTs.
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4.1. Distinguishing SETs from ID Tokens
A SET might be confused with ID Token [OpenID.Core] if a SET is
mistakenly or maliciously 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 contexts for which substitution is
possible.
Note that the use of explicit typing, as described in Section 2.3,
will not achieve disambiguation between ID Tokens and SETs, as the ID
Token validation rules do not use the "typ" header parameter value.
4.2. 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 recipient 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.
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o Employ explicit typing, as described in Section 2.3, and modify
access token validation systems to use the "typ" header parameter
value.
4.3. 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) [RFC8225] 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 prevent confusion is to employ explicit
typing, as described in Section 2.3, 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.
Another 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.
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 [RFC8225],
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.ietf-oauth-jwt-bcp]. The proposed best
practices in that draft may also be applicable for particular SET
profiles and use cases.
5. Security Considerations
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5.1. Confidentiality and Integrity
SETs may 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] or a higher version and MAY support additional
transport-layer mechanisms meeting its security requirements. When
using TLS, the client MUST perform a TLS 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.
Unless integrity of the JWT is ensured by other means, it MUST be
signed using JWS [RFC7515] so that the SET can be authenticated and
validated by the SET recipient.
5.2. Delivery
This specification does not define a delivery mechanism for SETs. In
addition to confidentiality and integrity (discussed above),
implementers and profiling 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 (mutual) TLS, there is no assurance that
the correct endpoint received the SET and that it could be
successfully processed.
5.3. Sequencing
This specification defines no means of ordering multiple SETs in a
sequence. Depending on the type and nature of the events represented
by SETs, order may or may not matter. For example, in provisioning,
event order is critical -- an object cannot be modified before it is
created. In other SET types, such as a token revocation, the order
of SETs for revoked tokens does not matter. If, however, the event
conveys a logged 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. Thus, time by itself will not
guarantee order.
Specifications profiling SET SHOULD define a mechanism for detecting
order or sequence of events when the order matters. For example, the
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"txn" claim could contain an ordered value (e.g., a counter) that the
issuer includes, although just as for timestamps, ensuring such
ordering can be difficult in distributed systems.
5.4. 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 SET
recipient in advance of or behind the process that caused the event.
For example, a user having been required to log out and then log back
in again, may cause a token revoked SET to be issued, typically
causing the receiver to reset all active sessions at the receiver
that are related to that user. If revocation SET arrives at the same
time as the user agent re-logs in, timing could cause problems by
erroneously treating the new user session as logged out. Profiling
specifications SHOULD be careful to consider both SET expression and
timing issues. For example, it might be more appropriate to revoke a
specific session or identity token rather than a general logout
statement about a "user". Alternatively, profiling specifications
could use timestamps that allow new sessions to be started
immediately after a stated logout event time.
5.5. Preventing Confusion
Also, see Section 4 above for both additional security considerations
and normative text on preventing SETs from being confused with other
kinds of JWTs.
6. Privacy Considerations
If a SET needs to be retained for audit purposes, the signature can
be used to provide verification of its authenticity.
SET issuers SHOULD attempt to specialize SETs so that their content
is targeted to the specific business and protocol needs of the
intended SET recipients.
When sharing personally identifiable information or information that
is otherwise considered confidential to affected users, SET issuers
and recipients should have the appropriate legal agreements and user
consent and/or terms of service in place.
The propagation of subject identifiers can be perceived as personally
identifiable information. Where possible, SET issuers and recipients
SHOULD devise approaches that prevent propagation -- for example, the
passing of a salted hash value that requires the SET recipient to
know the subject.
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In some cases, it may be possible for a SET recipient to correlate
different events and thereby gain information about a subject that
the SET issuer did not intend to share. For example, a SET recipient
might be able to use "iat" values or highly precise "toe" values to
determine that two otherwise un-relatable events actually relate to
the same real-world event. The union of information from both events
could allow a SET recipient to de-anonymize data or recognize that
unrelated identifiers relate to the same individual. SET issuers
SHOULD take steps to minimize the chance of event correlation, when
such correlation would constitute a privacy violation. For instance,
they could use approximate values for the "toe" claim or arbitrarily
delay SET issuance, where such delay can be tolerated.
7. IANA Considerations
7.1. JSON Web Token Claims Registration
This specification registers the "events", "toe", and "txn" claims in
the IANA "JSON Web Token Claims" registry [IANA.JWT.Claims]
established by [RFC7519].
7.1.1. Registry Contents
o Claim Name: "events"
o Claim Description: Security Events
o Change Controller: IESG
o Specification Document(s): Section 2.2 of [[ this specification ]]
o Claim Name: "toe"
o Claim Description: Time of Event
o Change Controller: IESG
o Specification Document(s): Section 2.2 of [[ this specification ]]
o Claim Name: "txn"
o Claim Description: Transaction Identifier
o Change Controller: IESG
o Specification Document(s): Section 2.2 of [[ this specification ]]
7.2. Media Type Registration
7.2.1. 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
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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 2.3 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
8. References
8.1. 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,
<https://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,
<https://www.rfc-editor.org/info/rfc3986>.
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[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://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, <https://www.rfc-editor.org/info/rfc6125>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://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,
<https://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, <https://www.rfc-editor.org/info/rfc7525>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
8.2. Informative References
[I-D.ietf-oauth-jwt-bcp]
Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
Current Practices", draft-ietf-oauth-jwt-bcp-01 (work in
progress), March 2018.
[OpenID.BackChannel]
Jones, M. and J. Bradley, "OpenID Connect Back-Channel
Logout 1.0", January 2017, <http://openid.net/specs/
openid-connect-backchannel-1_0.html>.
[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>.
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[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
DOI 10.17487/RFC2046, November 1996,
<https://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,
<https://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, <https://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, <https://www.rfc-editor.org/info/rfc7515>.
[RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015,
<https://www.rfc-editor.org/info/rfc7516>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/info/rfc7517>.
[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, <https://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,
<https://www.rfc-editor.org/info/rfc8055>.
[RFC8225] Wendt, C. and J. Peterson, "PASSporT: Personal Assertion
Token", RFC 8225, DOI 10.17487/RFC8225, February 2018,
<https://www.rfc-editor.org/info/rfc8225>.
[RISC] OpenID Foundation, "OpenID Risk and Incident Sharing and
Coordination (RISC) Working Group",
<http://openid.net/wg/risc/>.
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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, the Security
Events working group, and related working groups for their
contributions to this specification. The specification incorporates
suggestions made by many people, including Annabelle Backman, John
Bradley, Dick Hardt, Russ Housley, Benjamin Kaduk, Mark Lizar, Andrew
Nash, Justin Richer, Nat Sakimura, Marius Scurtescu, and Yaron
Sheffer.
Appendix B. Change Log
[[ to be removed by the RFC Editor before publication as an RFC ]]
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
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 -
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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
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
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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.
Draft 03 - Changes are as follows:
o pjh - Corrected old "subscriber" to "Event Receiver". Added
clarification in definition that Event Receiver is the same as JWT
recipient.
o pjh - Added definition for "toe" (and IANA registration).
o pjh - Removed "nbf" claim.
o pjh - Figure 3, moved "sub" to the events payload next to "iss".
o pjh - Clarified the use of "nonce" in contexts where substitution
is possible.
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o mbj - Addressed WGLC comments by Nat Sakimura.
o mbj - Addressed WGLC comments by Annabelle Backman.
o mbj - Addressed WGLC comments by Marius Scurtescu.
Draft 04 - mbj - Changes were as follows:
o Clarified that all "events" values must represent aspects of the
same state change that occurred to the subject -- not an
aggregation of unrelated events about the subject.
o Removed ambiguities about the roles of multiple "events" values
and the responsibilities of profiling specifications for defining
how and when they are used.
o Corrected places where the term JWT was used when what was
actually being discussed was the JWT Claims Set.
o Addressed terminology inconsistencies. In particular,
standardized on using the term "issuer" to align with JWT
terminology and the "iss" claim. Previously the term
"transmitter" was sometimes used and "issuer" was sometimes used.
Likewise, standardized on using the term "recipient" instead of
"receiver" for the same reasons.
o Added a RISC event example, courtesy of Marius Scurtescu.
o Applied wording clarifications suggested by Annabelle Backman and
Yaron Sheffer.
o Applied numerous grammar, syntax, and formatting corrections.
Draft 05 - mbj - Changes were as follows:
o Simplified the definitions of the "iat" and "toe" claims in ways
suggested by Annabelle Backman.
o Added privacy considerations text suggested by Annabelle Backman.
o Updated the RISC event example, courtesy of Marius Scurtescu.
o Reordered the claim definitions to place the required claims
first.
o Changed to using the RFC 8174 boilerplate instead of the RFC 2119
boilerplate.
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Draft 06 - mbj - Changes were as follows:
o Changed "when the event was issued" to "when the SET was issued"
in the "iat" description, as suggested by Annabelle Backman.
o Applied editorial improvements that improve the consistency of the
specification that were suggested by Annabelle Backman, Marius
Scurtescu, and Yaron Sheffer.
Draft 07 - PH - Text refinement to Section 3 proposed by Annabelle
Backman post WGLC
Draft 08 - mbj - Changes were as follows:
o Incorporated wording improvements resulting from Russ Housley's
SecDir comments.
o Acknowledged individuals who made significant contributions.
Draft 09 - pjh/mbj - Changes addressing AD review comments by
Benjamin Kaduk
Authors' Addresses
Phil Hunt (editor)
Oracle Corporation
Email: phil.hunt@yahoo.com
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://self-issued.info/
William Denniss
Google
Email: wdenniss@google.com
Morteza Ansari
Cisco
Email: morteza.ansari@cisco.com
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