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 Hunt, et al. Expires January 1, 2018 [Page 1] Internet-Draft draft-ietf-secevent-token June 2017 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]. Hunt, et al. Expires January 1, 2018 [Page 2] Internet-Draft draft-ietf-secevent-token June 2017 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. Hunt, et al. Expires January 1, 2018 [Page 3] Internet-Draft draft-ietf-secevent-token June 2017 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. Hunt, et al. Expires January 1, 2018 [Page 4] Internet-Draft draft-ietf-secevent-token June 2017 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. Hunt, et al. Expires January 1, 2018 [Page 5] Internet-Draft draft-ietf-secevent-token June 2017 * 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 Hunt, et al. Expires January 1, 2018 [Page 6] Internet-Draft draft-ietf-secevent-token June 2017 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. Hunt, et al. Expires January 1, 2018 [Page 7] Internet-Draft draft-ietf-secevent-token June 2017 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 Hunt, et al. Expires January 1, 2018 [Page 8] Internet-Draft draft-ietf-secevent-token June 2017 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. Hunt, et al. Expires January 1, 2018 [Page 9] Internet-Draft draft-ietf-secevent-token June 2017 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. Hunt, et al. Expires January 1, 2018 [Page 10] Internet-Draft draft-ietf-secevent-token June 2017 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 Hunt, et al. Expires January 1, 2018 [Page 11] Internet-Draft draft-ietf-secevent-token June 2017 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. Hunt, et al. Expires January 1, 2018 [Page 12] Internet-Draft draft-ietf-secevent-token June 2017 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 Hunt, et al. Expires January 1, 2018 [Page 13] Internet-Draft draft-ietf-secevent-token June 2017 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. Hunt, et al. Expires January 1, 2018 [Page 14] Internet-Draft draft-ietf-secevent-token June 2017 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 Hunt, et al. Expires January 1, 2018 [Page 15] Internet-Draft draft-ietf-secevent-token June 2017 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]. Hunt, et al. Expires January 1, 2018 [Page 16] Internet-Draft draft-ietf-secevent-token June 2017 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 Hunt, et al. Expires January 1, 2018 [Page 17] Internet-Draft draft-ietf-secevent-token June 2017 7. References 7.1. Normative References [IANA.JWT.Claims] IANA, "JSON Web Token Claims", . [IANA.MediaTypes] IANA, "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, . [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, . [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008, . [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and Verification of Domain-Based Application Service Identity within Internet Public Key Infrastructure Using X.509 (PKIX) Certificates in the Context of Transport Layer Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March 2011, . [RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012, . [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, . [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, "Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 2015, . Hunt, et al. Expires January 1, 2018 [Page 18] Internet-Draft draft-ietf-secevent-token June 2017 [RFC7617] Reschke, J., "The 'Basic' HTTP Authentication Scheme", RFC 7617, DOI 10.17487/RFC7617, September 2015, . 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, . [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types", RFC 2046, DOI 10.17487/RFC2046, November 1996, . [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type Specifications and Registration Procedures", BCP 13, RFC 6838, DOI 10.17487/RFC6838, January 2013, . [RFC7009] Lodderstedt, T., Ed., Dronia, S., and M. Scurtescu, "OAuth 2.0 Token Revocation", RFC 7009, DOI 10.17487/RFC7009, August 2013, . [RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015, . [RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)", RFC 7516, DOI 10.17487/RFC7516, May 2015, . [RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517, DOI 10.17487/RFC7517, May 2015, . Hunt, et al. Expires January 1, 2018 [Page 19] Internet-Draft draft-ietf-secevent-token June 2017 [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, . [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, . [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 Hunt, et al. Expires January 1, 2018 [Page 20] Internet-Draft draft-ietf-secevent-token June 2017 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 Hunt, et al. Expires January 1, 2018 [Page 21] Internet-Draft draft-ietf-secevent-token June 2017 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 Hunt, et al. Expires January 1, 2018 [Page 22] Internet-Draft draft-ietf-secevent-token June 2017 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/ Hunt, et al. Expires January 1, 2018 [Page 23]