| Security Events Working Group | A. Backman, Ed. |
| Internet-Draft | Amazon |
| Intended status: Standards Track | M. Jones, Ed. |
| Expires: December 17, 2020 | Microsoft |
| M. Scurtescu | |
| Coinbase | |
| M. Ansari | |
| Cisco | |
| A. Nadalin | |
| Microsoft | |
| June 15, 2020 |
Poll-Based Security Event Token (SET) Delivery Using HTTP
draft-ietf-secevent-http-poll-11
This specification defines how a series of Security Event Tokens (SETs) can be delivered to an intended recipient using HTTP POST over TLS initiated as a poll by the recipient. The specification also defines how delivery can be assured, subject to the SET Recipient's need for assurance.
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 December 17, 2020.
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This specification defines how a stream of Security Event Tokens (SETs) [RFC8417] can be transmitted to an intended SET Recipient using HTTP [RFC7231] over TLS. The specification defines a method to poll for SETs using HTTP POST. This is an alternative SET delivery method to the one defined in [I-D.ietf-secevent-http-push].
A mechanism for exchanging configuration metadata such as endpoint URLs and cryptographic keys between the transmitter and recipient is out of scope for this specification. How SETs are defined and the process by which security events are identified for SET Recipients are specified in [RFC8417].
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 document, all figures may contain spaces and extra line wrapping for readability and due to space limitations.
This specification utilizes terminology defined in [RFC8417] and [I-D.ietf-secevent-http-push].
When a SET is available for a SET Recipient, the SET Transmitter queues the SET in a buffer so that a SET Recipient can poll for SETs using HTTP POST.
In poll-based SET delivery using HTTP over TLS, zero or more SETs are delivered in a JSON [RFC8259] document to a SET Recipient in response to an HTTP POST request to the SET Transmitter. Then in a following request, the SET Recipient acknowledges received SETs and can poll for more. All requests and responses are JSON documents and use a Content-Type of application/json, as described in Section 2.1.
After successful (acknowledged) SET delivery, SET Transmitters are not required to retain or record SETs for retransmission. Once a SET is acknowledged, the SET Recipient SHALL be responsible for retention, if needed. Transmitters may also discard undelivered SETs under deployment-specific conditions, such as if they have not been polled for over too long a period of time or if an excessive amount of storage is needed to retain them.
Upon receiving a SET, the SET Recipient reads the SET and validates it in the manner described in Section 2 of [I-D.ietf-secevent-http-push]. The SET Recipient MUST acknowledge receipt to the SET Transmitter, and SHOULD do in a timely fashion, as described in Section 2.4. The SET Recipient SHALL NOT use the event acknowledgement mechanism to report event errors other than those relating to the parsing and validation of the SET.
This method allows a SET Recipient to use HTTP POST (Section 4.3.3 of [RFC7231]) to acknowledge SETs and to check for and receive zero or more SETs. Requests MAY be made at a periodic interval (short polling) or requests MAY wait, pending availability of new SETs using long polling, per Section 2 of [RFC6202]. Note that short polling will result in retrieving zero or more SETs whereas long polling will typically result in retrieving one or more SETs unless a timeout occurs.
The delivery of SETs in this method is facilitated by HTTP POST requests initiated by the SET Recipient in which:
The purpose of the acknowledgement is to inform the SET Transmitter that delivery has succeeded and redelivery is no longer required. Before acknowledgement, SET Recipients SHOULD ensure that received SETs have been validated and retained in a manner appropriate to the recipient's requirements. The level and method of retention of SETs by SET Recipients is out of scope of this specification.
When initiating a poll request, the SET Recipient constructs a JSON document that consists of polling request parameters and SET acknowledgement parameters in the form of JSON objects.
When making a request, the HTTP header Content-Type is set to application/json.
The following JSON object members are used in a polling request:
In response to a poll request, the SET Transmitter checks for available SETs and responds with a JSON document containing the following JSON object members:
When making a response, the HTTP header Content-Type is set to application/json.
The SET Recipient performs an HTTP POST (see Section 4.3.4 of [RFC7231]) to a pre-arranged polling endpoint URI to check for SETs that are available. Because the SET Recipient has no prior SETs to acknowledge, the ack and setErrs request parameters are omitted.
After a period of time configured between the SET Transmitter and Recipient, a SET Transmitter MAY redeliver SETs it has previously delivered. The SET Recipient SHOULD accept repeat SETs and acknowledge the SETs regardless of whether the Recipient believes it has already acknowledged the SETs previously. A SET Transmitter MAY limit the number of times it attempts to deliver a SET.
If the SET Recipient has received SETs from the SET Transmitter, the SET Recipient SHOULD parse and validate received SETs to meet its own requirements and SHOULD acknowledge receipt in a timely fashion (e.g., seconds or minutes) so that the SET Transmitter can mark the SETs as received. SET Recipients SHOULD acknowledge receipt before taking any local actions based on the SETs to avoid unnecessary delay in acknowledgement, where possible.
Poll requests have three variations:
In the case where no SETs were received in a previous poll (see Figure 7), the SET Recipient simply polls without acknowledgement parameters (ack and setErrs).
The following is an example request made by a SET Recipient that has no outstanding SETs to acknowledge and is polling for available SETs at the endpoint https://notify.idp.example.com/Events:
POST /Events HTTP/1.1
Host: notify.idp.example.com
Content-Type: application/json
{
"returnImmediately": true
}
Figure 1: Example Initial Poll Request
A SET Recipient can poll using default parameter values by passing an empty JSON object.
The following is a non-normative example default poll request to the endpoint https://notify.idp.example.com/Events:
POST /Events HTTP/1.1
Host: notify.idp.example.com
Content-Type: application/json
{}
Figure 2: Example Default Poll Request
In this variation, the SET Recipient acknowledges previously received SETs and indicates it does not want to receive SETs in response by setting the maxEvents value to 0.
This variation might be used, for instance, when a SET Recipient needs to acknowledge received SETs independently (e.g., on separate threads) from the process of receiving SETs.
The following is a non-normative example poll request with acknowledgement of SETs received (for example as shown in Figure 6):
POST /Events HTTP/1.1
Host: notify.idp.example.com
Content-Type: application/json
{
"ack": [
"4d3559ec67504aaba65d40b0363faad8",
"3d0c3cf797584bd193bd0fb1bd4e7d30"
],
"maxEvents": 0,
"returnImmediately": true
}
Figure 3: Example Acknowledge Only Request
This variation allows a recipient thread to simultaneously acknowledge previously received SETs and wait for the next group of SETs in a single request.
The following is a non-normative example poll with acknowledgement of the SETs received in Figure 6:
POST /Events HTTP/1.1
Host: notify.idp.example.com
Content-Type: application/json
{
"ack": [
"4d3559ec67504aaba65d40b0363faad8",
"3d0c3cf797584bd193bd0fb1bd4e7d30"
],
"returnImmediately": false
}
Figure 4: Example Poll with Acknowledgement and No Errors
In the above acknowledgement, the SET Recipient has acknowledged receipt of two SETs and has indicated it wants to wait until the next SET is available.
In the case where errors were detected in previously delivered SETs, the SET Recipient MAY use the setErrs member to communicate the errors in the following poll request.
The following is a non-normative example of a response acknowledging one successfully received SET and one SET with an error from the two SETs received in Figure 6:
POST /Events HTTP/1.1
Host: notify.idp.example.com
Content-Language: en-US
Content-Type: application/json
{
"ack": ["3d0c3cf797584bd193bd0fb1bd4e7d30"],
"setErrs": {
"4d3559ec67504aaba65d40b0363faad8": {
"err": "authentication_failed",
"description": "The SET could not be authenticated"
}
},
"returnImmediately": true
}
Figure 5: Example Poll Acknowledgement with Error
In response to a valid poll request, the service provider MAY respond immediately if SETs are available to be delivered. If no SETs are available at the time of the request, the SET Transmitter SHALL delay responding until a SET is available or the timeout interval has elapsed unless the poll request parameter returnImmediately is present with the value true.
As described in Section 2.3, a JSON document is returned containing members including sets, which SHALL contain zero or more SETs.
The following is a non-normative example response to the request shown in Section 2.4. This example shows two SETs being returned:
HTTP/1.1 200 OK
Content-Type: application/json
{
"sets": {
"4d3559ec67504aaba65d40b0363faad8":
"eyJhbGciOiJub25lIn0.
eyJqdGkiOiI0ZDM1NTllYzY3NTA0YWFiYTY1ZDQwYjAzNjNmYWFkOCIsImlhdCI6MTQ
1ODQ5NjQwNCwiaXNzIjoiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tIiwiYXVkIjpbIm
h0dHBzOi8vc2NpbS5leGFtcGxlLmNvbS9GZWVkcy85OGQ1MjQ2MWZhNWJiYzg3OTU5M
2I3NzU0IiwiaHR0cHM6Ly9zY2ltLmV4YW1wbGUuY29tL0ZlZWRzLzVkNzYwNDUxNmIx
ZDA4NjQxZDc2NzZlZTciXSwiZXZlbnRzIjp7InVybjppZXRmOnBhcmFtczpzY2ltOmV
2ZW50OmNyZWF0ZSI6eyJyZWYiOiJodHRwczovL3NjaW0uZXhhbXBsZS5jb20vVXNlcn
MvNDRmNjE0MmRmOTZiZDZhYjYxZTc1MjFkOSIsImF0dHJpYnV0ZXMiOlsiaWQiLCJuY
W1lIiwidXNlck5hbWUiLCJwYXNzd29yZCIsImVtYWlscyJdfX19.",
"3d0c3cf797584bd193bd0fb1bd4e7d30":
"eyJhbGciOiJub25lIn0.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."
}
}
Figure 6: Example Poll Response
In the above example, two SETs whose jti values are 4d3559ec67504aaba65d40b0363faad8 and 3d0c3cf797584bd193bd0fb1bd4e7d30 are delivered.
The following is a non-normative example response to the request shown in Section 2.4.1, which indicates that no new SETs or unacknowledged SETs are available:
HTTP/1.1 200 OK
Content-Type: application/json
{
"sets": {}
}
Figure 7: Example No SETs Poll Response
Upon receiving the JSON document (e.g., as shown in Figure 6), the SET Recipient parses and verifies the received SETs and notifies the SET Transmitter of successfully received SETs and SETs with errors via the next poll request to the SET Transmitter, as described in Section 2.4.3 or Section 2.4.4.
In the event of a general HTTP error condition in the context of processing a poll request, the service provider SHOULD respond with an appropriate HTTP Response Status Code as defined in Section 6 of [RFC7231].
Service providers MAY respond to any invalid poll request with an HTTP Response Status Code of 400 (Bad Request) even when a more specific code might apply, for example if the service provider deemed that a more specific code presented an information disclosure risk. When no more specific code might apply, the service provider SHALL respond to an invalid poll request with an HTTP Status Code of 400.
The response body for responses to invalid poll requests is left undefined, and its contents SHOULD be ignored.
The following is a non-normative example of a response to an invalid poll request:
HTTP/1.1 400 Bad Request
Example Poll Error Response
If a SET is invalid, error codes from the IANA "Security Event Token Delivery Error Codes" registry established by [I-D.ietf-secevent-http-push] are used in error responses. As described in Section 2.3 of [I-D.ietf-secevent-http-push], an error response is a JSON object providing details about the error that includes the following name/value pairs:
When included as part of a batch of SETs, the above JSON is included as part of the setErrs member, as defined in Section 2.2 and Section 2.4.4.
When the SET Recipient includes one or more error responses in a request to the SET Transmitter, it must also include in the request a Content-Language header whose value indicates the language of the error descriptions included in the request. The method of language selection in the case when the SET Recipient can provide error messages in multiple languages is out of scope for this specification.
The SET delivery method described in this specification is based upon HTTP over TLS [RFC2818] and standard HTTP authentication and authorization schemes, as per [RFC7235]. The TLS server certificate MUST be validated, per [RFC6125]. As per Section 4.1 of [RFC7235], a SET delivery endpoint SHALL indicate supported HTTP authentication schemes via the WWW-Authenticate header when using HTTP authentication.
Authorization for the eligibility to provide actionable SETs can be determined by using the identity of the SET Issuer, validating the polling endpoint URL, perhaps using mutual TLS, or via other employed authentication methods. Because SETs are not commands, SET Recipients are free to ignore SETs that are not of interest after acknowledging their receipt.
JWS signed SETs can be used (see [RFC7515] and Section 5 of [RFC8417]) to enable the SET Recipient to validate that the SET Issuer is authorized to provide actionable SETs.
SET delivery depends on the use of Hypertext Transfer Protocol and is thus subject to the security considerations of HTTP Section 9 of [RFC7230] and its related specifications.
SETs may contain sensitive information that is considered Personally Identifiable Information (PII). In such cases, SET Transmitters and SET Recipients MUST protect the confidentiality of the SET contents. In some use cases, using TLS to secure the transmitted SETs will be sufficient. In other use cases, encrypting the SET as described in JWE [RFC7516] will also be required. The Event delivery endpoint MUST support at least TLS version 1.2 [RFC5246] and SHOULD support the newest version of TLS that meets its security requirements, which as of the time of this publication is TLS 1.3 [RFC8446]. The client MUST perform a TLS/SSL server certificate check using DNS-ID [RFC6125]. How a SET Recipient determines the expected service identity to match the SET Transmitter's server certificate against is out of scope for this document. Implementation security considerations for TLS can be found in "Recommendations for Secure Use of TLS and DTLS" [RFC7525].
If HTTP Authentication is performed using OAuth access tokens [RFC6749], implementers MUST take into account the threats and countermeasures documented in Section 8 of [RFC7521].
Transmitting Bearer tokens [RFC6750] using TLS helps prevent their interception.
Bearer tokens SHOULD have a limited lifetime that can be determined directly or indirectly (e.g., by checking with a validation service) by the service provider. By expiring tokens, clients are forced to obtain a new token (which usually involves re-authentication) for continued authorized access. For example, in OAuth 2.0, a client MAY use an OAuth refresh token to obtain a new bearer token after authenticating to an authorization server, per Section 6 of [RFC6749].
Implementations supporting OAuth bearer tokens need to factor in security considerations of this authorization method [RFC7521]. Since security is only as good as the weakest link, implementers also need to consider authentication choices coupled with OAuth bearer tokens. The security considerations of the default authentication method for OAuth bearer tokens, HTTP Basic, are well documented in [RFC7617], therefore implementers are encouraged to prefer stronger authentication methods.
SET Transmitters SHOULD attempt to deliver SETs that are 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, SET Transmitters and Recipients MUST have the appropriate legal agreements and user consent or terms of service in place. Furthermore, data that needs confidentiality protection MUST be encrypted, at least with TLS and sometimes also using JSON Web Encryption (JWE) [RFC7516].
In some cases, subject identifiers themselves may be considered sensitive information, such that their inclusion within a SET may be considered a violation of privacy. SET Issuers should consider the ramifications of sharing a particular subject identifier with a SET Recipient (e.g., whether doing so could enable correlation and/or de-anonymization of data) and choose appropriate subject identifiers for their use cases.
This specification requires no IANA actions.
| [RFC6202] | Loreto, S., Saint-Andre, P., Salsano, S. and G. Wilkins, "Known Issues and Best Practices for the Use of Long Polling and Streaming in Bidirectional HTTP", RFC 6202, DOI 10.17487/RFC6202, April 2011. |
| [RFC6749] | Hardt, D., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012. |
| [RFC6750] | Jones, M. and D. Hardt, "The OAuth 2.0 Authorization Framework: Bearer Token Usage", RFC 6750, DOI 10.17487/RFC6750, October 2012. |
| [RFC7230] | Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, DOI 10.17487/RFC7230, June 2014. |
| [RFC7235] | Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Authentication", RFC 7235, DOI 10.17487/RFC7235, June 2014. |
| [RFC7617] | Reschke, J., "The 'Basic' HTTP Authentication Scheme", RFC 7617, DOI 10.17487/RFC7617, September 2015. |
Earlier versions of this specification made the use of TLS optional and described security and privacy considerations resulting from use of unencrypted HTTP as the underlying transport. When the working group decided to mandate usage HTTP over TLS, it also decided to preserve the description of these considerations in a non-normative manner.
The considerations for using unencrypted HTTP with this protocol are the same as those described in Appendix A of [I-D.ietf-secevent-http-push], and are therefore not repeated here.
The editors would like to thank the members of the SCIM working group, which began discussions of provisioning events starting with draft-hunt-scim-notify-00 in 2015. We would like to thank Phil Hunt and the other the authors of draft-ietf-secevent-delivery-02, upon which this specification is based. We would like to thank the participants in the SecEvents working group for their contributions to this specification.
Additionally, we would like to thank the following individuals for their reviews of the specification: Benjamin Kaduk, Mark Nottingham, Yaron Sheffer, Valery Smyslov, and Robert Sparks.
[[ to be removed by the RFC Editor before publication as an RFC ]]
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