| Security Events Working Group | A. Backman, Ed. |
| Internet-Draft | Amazon |
| Intended status: Standards Track | M. Jones, Ed. |
| Expires: April 4, 2019 | Microsoft |
| M. Scurtescu | |
| M. Ansari | |
| Cisco | |
| A. Nadalin | |
| Microsoft | |
| October 1, 2018 |
Push-Based SET Token Delivery Using HTTP
draft-ietf-secevent-http-push-01
This specification defines how a series of security event tokens (SETs) may be delivered to a previously registered receiver using HTTP POST over TLS initiated as a push to the receiver.
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 4, 2019.
Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved.
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This specification defines how SETs (see [RFC8417]) can be transmitted to a previously registered SET Receiver using HTTP [RFC7231] over TLS. The specification defines a method to push SETs via HTTP POST.
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.
Throughout this documents all figures may contain spaces and extra line-wrapping for readability and space limitations.
This specification assumes terminology defined in the Security Event Token specification[RFC8417], as well as the terms defined below:
In Push-Based SET Delivery Using HTTP, SETs are delivered one at a time using HTTP POST requests by a SET Transmitter to a SET Receiver, as described below in Section 2.2. Upon receipt, the SET Receiver acknowledges receipt or indicates an error via the HTTP response, as described below in Section 2.3.
After successful (acknowledged) SET delivery, SET Transmitters SHOULD NOT be required to maintain or record SETs for recovery. Once a SET is acknowledged, the SET Receiver SHALL be responsible for retention and recovery.
Transmitted SETs SHOULD be self-validating (e.g. signed) if there is a requirement to verify they were issued by the SET Transmitter at a later date when de-coupled from the original delivery where authenticity could be checked via the HTTP or TLS mutual authentication.
Upon receiving a SET, the SET Receiver reads the SET and validates it. The SET Receiver MUST acknowledge receipt to the SET Transmitter, using the defined acknowledgement or error method.
The SET Receiver SHALL NOT use the Event acknowledgement mechanism to report Event errors other than relating to the parsing and validation of the SET.
This method allows a SET Transmitter to use HTTP POST (Section 4.3.3) to deliver SETs to a previously registered web callback URI supplied by the SET Receiver as part of a configuration process (not defined by this document).
The SET to be delivered MAY be signed and/or encrypted as defined in [RFC8417].
The HTTP Content-Type (see Section 3.1.1.5) for the HTTP POST is application/secevent+jwt and the request body SHALL consist of a single SET (see [RFC8417]). As per Section 5.3.2, the value of the Accept header is application/json.
The following is a non-normative example of a SET transmission HTTP POST request:
POST /Events HTTP/1.1 Host: notify.examplerp.com Accept: application/json Content-Type: application/secevent+jwt eyJhbGciOiJub25lIn0 . eyJwdWJsaXNoZXJVcmkiOiJodHRwczovL3NjaW0uZXhhbXBsZS5jb20iLCJmZWV kVXJpcyI6WyJodHRwczovL2podWIuZXhhbXBsZS5jb20vRmVlZHMvOThkNTI0Nj FmYTViYmM4Nzk1OTNiNzc1NCIsImh0dHBzOi8vamh1Yi5leGFtcGxlLmNvbS9GZ WVkcy81ZDc2MDQ1MTZiMWQwODY0MWQ3Njc2ZWU3Il0sInJlc291cmNlVXJpcyI6 WyJodHRwczovL3NjaW0uZXhhbXBsZS5jb20vVXNlcnMvNDRmNjE0MmRmOTZiZDZ hYjYxZTc1MjFkOSJdLCJldmVudFR5cGVzIjpbIkNSRUFURSJdLCJhdHRyaWJ1dG VzIjpbImlkIiwibmFtZSIsInVzZXJOYW1lIiwicGFzc3dvcmQiLCJlbWFpbHMiX SwidmFsdWVzIjp7ImVtYWlscyI6W3sidHlwZSI6IndvcmsiLCJ2YWx1ZSI6Impk b2VAZXhhbXBsZS5jb20ifV0sInBhc3N3b3JkIjoibm90NHUybm8iLCJ1c2VyTmF tZSI6Impkb2UiLCJpZCI6IjQ0ZjYxNDJkZjk2YmQ2YWI2MWU3NTIxZDkiLCJuYW 1lIjp7ImdpdmVuTmFtZSI6IkpvaG4iLCJmYW1pbHlOYW1lIjoiRG9lIn19fQ .
Figure 1: Example SET Transmission Request
Upon receipt of the request, the SET Receiver SHALL validate the JWT structure of the SET as defined in Section 7.2. The SET Receiver SHALL also validate the SET information as described in Section 2.
If the SET is determined to be valid, the SET Receiver SHALL "acknowledge" successful submission by responding with HTTP Status 202 as Accepted (see Section 6.3.3).
In order to maintain compatibility with other methods of transmission, the SET Receiver SHOULD NOT include an HTTP response body representation of the submitted SET or what the SET's pending status is when acknowledging success. In the case of an error (e.g. HTTP Status 400), the purpose of the HTTP response body is to indicate any SET parsing, validation, or cryptographic errors.
The following is a non-normative example of a successful receipt of a SET.
HTTP/1.1 202 Accepted
Figure 2: Example Successful Delivery Response
Note that the purpose of the "acknowledgement" response is to let the SET Transmitter know that a SET has been delivered and the information no longer needs to be retained by the SET Transmitter. Before acknowledgement, SET Receivers SHOULD ensure they have validated received SETs and retained them in a manner appropriate to information retention requirements appropriate to the SET event types signaled. The level and method of retention of SETs by SET Receivers is out-of-scope of this specification.
In the Event of a general HTTP error condition, the SET Receiver MAY respond with an appropriate HTTP Status code as defined in Section 6.
When the SET Receiver detects an error parsing or validating a received SET (as defined by [RFC8417]), the SET Receiver SHALL indicate an HTTP Status 400 error with an error response as described in Section 2.3.4.
The following is an example non-normative error response.
HTTP/1.1 400 Bad Request
Content-Type: application/json
{
"err":"dup",
"description":"SET already received. Ignored."
}
Figure 3: Example Error Response
Security Event Token Delivery Error Codes are strings that identify a specific type of error that may occur when parsing or validating a SET. Every Security Event Token Delivery Error Code MUST have a unique name registered in the IANA "Security Event Token Delivery Error Codes" registry established by Section 6.1.
The following table presents the initial set of Error Codes that are registered in the IANA "Security Event Token Delivery Error Codes" registry:
| Error Code | Description |
|---|---|
| json | Invalid JSON object. |
| jwtParse | Invalid or unparsable JWT or JSON structure. |
| jwtHdr | In invalid JWT header was detected. |
| jwtCrypto | Unable to parse due to unsupported algorithm. |
| jws | Signature was not validated. |
| jwe | Unable to decrypt JWE encoded data. |
| jwtAud | Invalid audience value. |
| jwtIss | Issuer not recognized. |
| setType | An unexpected Event type was received. |
| setParse | Invalid structure was encountered such as an inability to parse or an incomplete set of Event claims. |
| setData | SET event claims incomplete or invalid. |
| dup | A duplicate SET was received and has been ignored. |
An error response SHALL include a JSON object which provides details about the error. The JSON object includes the JSON attributes: Figure 3).
When included as part of an HTTP Status 400 response, the above JSON is the HTTP response body (see
The SET delivery method described in this specification is based upon HTTP and depends on the use of TLS and/or standard HTTP authentication and authorization schemes as per [RFC7235].
Because SET Delivery describes a simple function, authorization for the ability to pick-up or deliver SETs can be derived by considering the identity of the SET issuer, or via other employed authentication methods. Because SETs are not commands (see ), SET Receivers are free to ignore SETs that are not of interest.
In scenarios where HTTP authorization or TLS mutual authentication are not used or are considered weak, JWS signed SETs SHOULD be used (see [RFC7515] and Security Considerations). This enables the SET Receiver to validate that the SET issuer is authorized to deliver SETs.
SETs contain sensitive information that is considered PII (e.g. subject claims). Therefore, SET Transmitters and SET Receivers MUST require the use of a transport-layer security mechanism. Event delivery endpoints 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].
The SET Receiver may be vulnerable to a denial-of-service attack where a malicious party makes a high volume of requests containing invalid SETs, causing the endpoint to expend significant resources on cryptographic operations that are bound to fail. This may be mitigated by authenticating SET Transmitters with a mechanism with low runtime overhead, such as mutual TLS or statically assigned bearer tokens.
If a SET needs to be retained for audit purposes, JWS MAY be used to provide verification of its authenticity.
When sharing personally identifiable information or information that is otherwise considered confidential to affected users, SET 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, SET Transmitters and Receivers SHOULD devise approaches that prevent propagation -- for example, the passing of a hash value that requires the subscriber to already know the subject.
This document defines Security Event Token Delivery Error Codes, for which IANA is asked to create and maintain a new registry titled "Security Event Token Delivery Error Codes". Initial values for the Security Event Token Delivery Error Codes registry are given in Table 1. Future assignments are to be made through the Expert Review registration policy ([RFC8126]) and shall follow the template presented in Section 6.1.1.
[[EDITORS NOTE: This section to be removed prior to publication]]
The following pub/sub, queuing, streaming systems were reviewed as possible solutions or as input to the current draft:
XMPP Events
The WG considered the XMPP events ands its ability to provide a single messaging solution without the need for both polling and push modes. The feeling was the size and methodology of XMPP was to far apart from the current capabilities of the SECEVENTs community which focuses in on HTTP based service delivery and authorization.
Amazon Simple Notification Service
Simple Notification Service, is a pub/sub messaging product from AWS. SNS supports a variety of subscriber types: HTTP/HTTPS endpoints, AWS Lambda functions, email addresses (as JSON or plain text), phone numbers (via SMS), and AWS SQS standard queues. It doesn’t directly support pull, but subscribers can get the pull model by creating an SQS queue and subscribing it to the topic. Note that this puts the cost of pull support back onto the subscriber, just as it is in the push model. It is not clear that one way is strictly better than the other; larger, sophisticated developers may be happy to own message persistence so they can have their own internal delivery guarantees. The long tail of OIDC clients may not care about that, or may fail to get it right. Regardless, I think we can learn something from the Delivery Policies supported by SNS, as well as the delivery controls that SQS offers (e.g. Visibility Timeout, Dead-Letter Queues). I’m not suggesting that we need all of these things in the spec, but they give an idea of what features people have found useful.
Other information:
Apache Kafka
Apache Kafka is an Apache open source project based upon TCP for distributed streaming. It prescribes some interesting general purpose features that seem to extend far beyond the simpler streaming model SECEVENTs is after. A comment from MS has been that Kafka does an acknowledge with poll combination event which seems to be a performance advantage. See: https://kafka.apache.org/intro
Google Pub/Sub
Google Pub Sub system favours a model whereby polling and acknowledgement of events is done as separate endpoints as separate functions.
Information:
The editors would like to thanks the members of the SCIM WG which began discussions of provisioning events starting with: draft-hunt-scim-notify-00 in 2015.
The editors would like to thank Phil Hunt and the other authors of draft-ietf-secevent-delivery-02, on which this draft is based.
The editor would like to thank the participants in the the SECEVENTS working group for their support of this specification.
Draft 00 - AB - Based on draft-ietf-secevent-delivery-02 with the following changes:
Draft 01 - AB: