caep-interop May 2026
Tulshibagwale, et al. Standards Track [Page]
Workgroup:
Shared Signals
Published:
Authors:
A. Tulshibagwale
Crowdstrike
A. Deshpande
Okta
J. Schreiber
Crowdstrike

CAEP Interoperability Profile 1.0 - draft 02

Abstract

This document defines an interoperability profile for implementations of the Shared Signals Framework ([SSF]) and the Continuous Access Evaluation Profile ([CAEP]). It specifies required attributes for SSF endpoints, how to use OAuth 2.0 [RFC6749] for their authorization, and the core use cases to improve security of authenticated sessions. When implemented, the profile enables seamless interoperability between SSF Transmitters and Receivers.

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Table of Contents

1. Introduction

The Shared Signals Framework enables sharing of Security Event Tokens (SETs) [RFC8417] between cooperating peers. When combined with Continuous Access Evaluation Profile ([CAEP]) to share events such as Session Revocation and Credential Change, implementations can greatly improve their session and security outcomes.

The CAEP Interoperability Profile outlines the minimum required features that implementations must offer in order to be considered compliant and to achieve interoperability. It describes specific use cases with CAEP session-revoked, credential-change, and device-compliance-change events. Support for all use cases listed herein is not required in order to be considered compliant with this profile. An implementation can choose specific use cases to support.

The following specifications are profiled in this document:

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.

2. Common Requirements

The following requirements are common across all use cases defined in this document.

2.1. Network Layer Protection

  • The SSF Transmitter MUST offer TLS protected endpoints and MUST establish connections to other servers using TLS. TLS connections MUST be set up to use TLS version 1.2 or later.

  • The SSF Transmitter MUST follow the recommendations for Secure Use of Transport Layer Security in [RFC9325].

  • The SSF Receiver MUST perform TLS server certificate signature checks, chain of trust validations, expiry and revocation status checks before calling the SSF Transmitter APIs, as per [RFC6125].

2.2. CAEP Specification Version

This specification supports CAEP [CAEP] events from OpenID Continuous Access Evaluation Profile 1.0.

2.3. Transmitters

Transmitters MUST implement the following features.

2.3.1. Specification Version

The Transmitter Configuration Metadata MUST include a spec_version field, and its value MUST be 1_0 or greater.

2.3.2. Delivery Method

The Transmitter Configuration Metadata MUST include the delivery_methods_supported field.

2.3.3. JWKS URI

The Transmitter Configuration Metadata MUST include the jwks_uri field, and upon resolution, its value MUST provide the current signing key(s) of the Transmitter.

2.3.4. Configuration Endpoint

The Transmitter Configuration Metadata MUST include the configuration_endpoint field as defined in [SSF] Section 7.1.

The endpoint identified by configuration_endpoint is used to perform the Create Stream operation as defined in [SSF] Section 8.1.1.

2.3.5. Status Endpoint

The Transmitter Configuration Metadata MUST include the status_endpoint field.

The endpoint identified by status_endpoint MUST support the Read Stream Status (HTTP GET) operation as defined in [SSF] Section 8.1.2.1.

2.3.6. Verification Endpoint

The Transmitter Configuration Metadata MUST include the verification_endpoint field.

The endpoint identified by verification_endpoint MUST support Stream Verification as defined in [SSF] Section 8.1.4.

2.3.7. Authorization Schemes

The Transmitter Configuration Metadata MUST include the authorization_schemes field and its value MUST include the value:

{
  "spec_urn": "urn:ietf:rfc:6749"
}

2.3.8. Streams

Transmitters MUST support all required properties and API contracts defined by [SSF] Stream Management API operations, in addition to the requirements specified in this section.

For all Stream Management API requests received by the Transmitter, the following MUST be true.

2.3.8.1. Delivery

The Transmitter MUST support Create Stream requests whose delivery.method is set to one of the following values:

  • urn:ietf:rfc:8935 (Push)

  • urn:ietf:rfc:8936 (Poll)

When a Receiver makes a Create Stream request as defined in [SSF] Section 8.1.1.1 with valid authorization, the Transmitter MUST process the request as specified in [SSF].

Upon successful creation of a Stream, the Transmitter MUST include a delivery field in the resulting Stream Configuration, and its method value MUST be one of the delivery methods listed above.

2.3.8.2. Stream Control
Create Stream

The Transmitter MUST support the Create Stream operation as defined in [SSF] Section 8.1.1.1 when invoked by a Receiver with valid authorization.

Read Stream Configuration

The Transmitter MUST support the Read Stream Configuration operation as defined in [SSF] Section 8.1.1.2 when invoked by a Receiver with valid authorization.

Read Stream Status

The Transmitter MUST support the Read Stream Status operation as defined in [SSF] Section 8.1.2.1 when invoked by a Receiver with valid authorization.

Stream Verification

The Transmitter MUST support Stream Verification as defined in [SSF] Section 8.1.4.2 and MUST generate a Verification Event as defined in [SSF] Section 8.1.4.1 when requested by a Receiver with valid authorization.

Deleting a Stream

The Transmitter MUST support the Delete Stream operation as defined in [SSF] Section 8.1.1.5 when invoked by a Receiver with valid authorization.

2.4. Receivers

Receivers MUST implement the following features.

2.4.1. Delivery Methods

Receivers MUST be able to accept events using any one of the two delivery methods:

  • Push-Based Security Event Token (SET) Delivery Using HTTP [RFC8935]

  • Poll-Based Security Event Token (SET) Delivery Using HTTP [RFC8936]

2.4.2. JWKS URI

The Receiver MUST obtain the Transmitter's signing key(s) using the jwks_uri from the Transmitter Configuration Metadata, as defined in [SSF] Section 7.1.

2.4.3. Authorization Schemes

The Receiver MUST use OAuth 2.0 [RFC6749] when making Stream Management API requests to the Transmitter.

2.4.4. Implicitly Added Subjects

The Receiver MUST assume that all subjects are implicitly included in a Stream, without any Add Subject method invocations.

2.4.5. Streams

Receivers MUST support all required properties and API contracts defined by [SSF] Stream Management API operations, in addition to the requirements specified in this section.

For Stream Management API requests initiated by the Receiver, and for Streams created by the Receiver, the following MUST be true.

2.4.5.1. Delivery

When creating a Stream using the Create Stream operation defined in [SSF] Section 8.1.1.1, the Receiver MUST include a delivery object whose method value is one of the following, or omit the delivery object.

  • urn:ietf:rfc:8935 (Push)

  • urn:ietf:rfc:8936 (Poll)

If the Create Stream request does not include the delivery property, it is assumed to have a delivery method of urn:ietf:rfc:8936 (Poll), as defined in [SSF].

2.4.5.2. Stream Control

The following Stream Management operations MUST be supported by the Receiver.

Create Stream

The Receiver MUST be able to invoke the Create Stream operation as defined in [SSF] Section 8.1.1.1 using valid authorization.

Read Stream Configuration

The Receiver MUST be able to invoke the Read Stream Configuration operation as defined in [SSF] Section 8.1.1.2 using valid authorization.

Read Stream Status

The Receiver MUST be able to invoke the Read Stream Status operation as defined in [SSF] Section 8.1.2.1 using valid authorization.

Stream Verification

The Receiver MUST be able to initiate Stream Verification as defined in [SSF] Section 8.1.4.2 using valid authorization, and MUST be able to process the resulting Verification Event as defined in [SSF] Section 8.1.4.1.

Deleting a Stream

The Receiver MUST be able to invoke the Delete Stream operation as defined in [SSF] Section 8.1.1.5 using valid authorization.

2.5. Event Subjects

The following subject identifier formats from "Subject Identifiers for Security Event Tokens" [RFC9493] MUST be supported:

  • email

  • iss_sub

  • opaque (for the Verification event only)

Receivers MUST be prepared to accept events with any of the subject identifier formats specified in this section. Transmitters MUST be able to send events with at least one of the subject identifier formats specified in this section.

2.6. Event Signatures

All events MUST be signed using the RS256 algorithm with a minimum of 2048-bit keys.

2.7. OAuth Support

Implementations MUST support OAuth 2.0 [RFC6749]. In this context, the OAuth 2.0 roles map to SSF roles as follows:

  • The Resource Server is the SSF Transmitter.

  • The Client is the SSF Receiver.

  • The Authorization Server is an entity trusted by the SSF Transmitter to issue access tokens.

2.7.1. Authorization Server

An OAuth [RFC6749] Authorization Server issues access tokens. In the context of this profile, the Authorization Server that issues access tokens can be a different entity than the SSF Transmitter.

  • The Authorization Server MAY distribute discovery metadata (such as the authorization endpoint) via Authorization Server Metadata as specified in [RFC8414]

  • The Authorization Server MUST support at least one of the following to issue a short-lived access token to the Receiver:

    • client credentials grant [RFC6749] Section 4.4

    • authorization code grant [RFC6749] Section 4.1

A short-lived access token is defined as one whose lifetime is no more than 60 minutes. Please refer to access token lifetimes in the security considerations of [FAPI] for additional considerations.

2.7.2. OAuth Scopes

The following scopes MUST be supported:

  • An OAuth [RFC6749] Authorization Server that is used to issue tokens to SSF Receivers MUST reserve the scopes for the SSF endpoints with the prefix of ssf

  • All the SSF stream configuration management API operations MUST accept ssf.manage scope

  • All the SSF stream configuration Read API operations MUST accept ssf.read scope

2.7.3. The SSF Transmitter as a Resource Server

  • MUST accept access tokens in the HTTP header as in Section 2.1 of OAuth 2.0 Bearer Token Usage [RFC6750]

  • MUST NOT accept access tokens via the URI query parameter mechanism described in Section 2.3 of OAuth 2.0 Bearer Token Usage [RFC6750]

  • MUST verify the validity, integrity, expiration and revocation status of access tokens

  • MUST verify that the authorization represented by the access token is sufficient for the requested resource access

  • If the access token is not sufficient for the requested action, the Resource Server MUST return errors as per Section 3.1 of [RFC6750]

2.8. Security Event Token

2.8.1. The "events" claim

The "events" claim of the SET MUST contain only one event.

3. Use Cases

An implementation conforming to this profile MUST support at least one of the following use cases.

3.1. Session Revocation / Logout

In order to support session revocation or logout, implementations MUST support the CAEP event type session-revoked. The reason_admin field of the event MUST be populated with a non-empty object.

3.2. Credential Change

In order to support notifying and responding to credential changes, implementations MUST support the CAEP event type credential-change. Within the credential-change event, implementations MUST support the following field values:

change_type

Receivers MUST interpret all allowable values of this field. Transmitters MAY generate any allowable value of this field

credential_type

Receivers MUST interpret all allowable values of this field. Transmitters MAY generate any allowable value of this field

reason_admin

Transmitters MUST populate this value with a non-empty object

3.3. Device Compliance Change

In order to support notifying and responding to changes in device compliance status, implementations MUST support the CAEP event type device-compliance-change. This event is used to signal that a device's adherence to a set of security or organizational compliance policies has changed. Implementations MUST support the following field values:

previous_status

Receivers MUST interpret all allowable values of this field. Transmitters MAY generate any allowable value of this field

current_status

Receivers MUST interpret all allowable values of this field. Transmitters MAY generate any allowable value of this field

reason_admin

Transmitters MUST populate this value with a non-empty object

4. Security Considerations

There are no additional security considerations that arise from this document. Security considerations applicable to this profile are covered in the "Security Considerations" sections of [SSF] and [CAEP].

5. Normative References

[CAEP]
Cappalli, T. and A. Tulshibagwale, "OpenID Continuous Access Evaluation Profile 1.0", n.d., <https://openid.net/specs/openid-caep-1_0-final.html>.
[FAPI]
Fett, D., Tonge, D., and J. Heenan, "FAPI 2.0 Security Profile", n.d., <https://openid.net/specs/fapi-security-profile-2_0-final.html>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[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, , <https://www.rfc-editor.org/info/rfc6125>.
[RFC6749]
Hardt, D., Ed., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, , <https://www.rfc-editor.org/info/rfc6749>.
[RFC6750]
Jones, M. and D. Hardt, "The OAuth 2.0 Authorization Framework: Bearer Token Usage", RFC 6750, DOI 10.17487/RFC6750, , <https://www.rfc-editor.org/info/rfc6750>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/info/rfc8174>.
[RFC8414]
Jones, M., Sakimura, N., and J. Bradley, "OAuth 2.0 Authorization Server Metadata", RFC 8414, DOI 10.17487/RFC8414, , <https://www.rfc-editor.org/info/rfc8414>.
[RFC8417]
Hunt, P., Ed., Jones, M., Denniss, W., and M. Ansari, "Security Event Token (SET)", RFC 8417, DOI 10.17487/RFC8417, , <https://www.rfc-editor.org/info/rfc8417>.
[RFC8935]
Backman, A., Ed., Jones, M., Ed., Scurtescu, M., Ansari, M., and A. Nadalin, "Push-Based Security Event Token (SET) Delivery Using HTTP", RFC 8935, DOI 10.17487/RFC8935, , <https://www.rfc-editor.org/info/rfc8935>.
[RFC8936]
Backman, A., Ed., Jones, M., Ed., Scurtescu, M., Ansari, M., and A. Nadalin, "Poll-Based Security Event Token (SET) Delivery Using HTTP", RFC 8936, DOI 10.17487/RFC8936, , <https://www.rfc-editor.org/info/rfc8936>.
[RFC9325]
Sheffer, Y., Saint-Andre, P., and T. Fossati, "Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC9325, , <https://www.rfc-editor.org/info/rfc9325>.
[RFC9493]
Backman, A., Ed., Scurtescu, M., and P. Jain, "Subject Identifiers for Security Event Tokens", RFC 9493, DOI 10.17487/RFC9493, , <https://www.rfc-editor.org/info/rfc9493>.
[SSF]
Tulshibagwale, A., Cappalli, T., Scurtescu, M., Backman, A., Bradley, J., and S. Miel, "OpenID Shared Signals Framework Specification 1.0", n.d., <https://openid.net/specs/openid-sharedsignals-framework-1_0-final.html>.

Appendix A. Acknowledgements

The authors wish to thank all members of the OpenID Foundation Shared Signals Working Group who contributed to the development of this specification.

Appendix B. Notices

Copyright (c) 2025 The OpenID Foundation.

The OpenID Foundation (OIDF) grants to any Contributor, developer, implementer, or other interested party a non-exclusive, royalty free, worldwide copyright license to reproduce, prepare derivative works from, distribute, perform and display, this Implementers Draft or Final Specification solely for the purposes of (i) developing specifications, and (ii) implementing Implementers Drafts and Final Specifications based on such documents, provided that attribution be made to the OIDF as the source of the material, but that such attribution does not indicate an endorsement by the OIDF.

The technology described in this specification was made available from contributions from various sources, including members of the OpenID Foundation and others. Although the OpenID Foundation has taken steps to help ensure that the technology is available for distribution, it takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this specification or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any independent effort to identify any such rights. The OpenID Foundation and the contributors to this specification make no (and hereby expressly disclaim any) warranties (express, implied, or otherwise), including implied warranties of merchantability, non-infringement, fitness for a particular purpose, or title, related to this specification, and the entire risk as to implementing this specification is assumed by the implementer. The OpenID Intellectual Property Rights policy requires contributors to offer a patent promise not to assert certain patent claims against other contributors and against implementers. The OpenID Foundation invites any interested party to bring to its attention any copyrights, patents, patent applications, or other proprietary rights that may cover technology that may be required to practice this specification.

Document History

[[ To be removed from the final specification ]]

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Authors' Addresses

Atul Tulshibagwale
Crowdstrike
Apoorva Deshpande
Okta
Jen Schreiber
Crowdstrike