Internet Engineering Task Force (IETF) R. Cordier, Ed.
Request for Comments: 9425 Linagora Vietnam
Category: Standards Track June 2023
ISSN: 2070-1721
JSON Meta Application Protocol (JMAP) for Quotas
Abstract
This document specifies a data model for handling quotas on accounts
with a server using the JSON Meta Application Protocol (JMAP).
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9425.
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Table of Contents
1. Introduction
1.1. Notational Conventions
1.2. Terminology
2. Addition to the Capabilities Object
2.1. urn:ietf:params:jmap:quota
3. Sub-types of the Quota Data Type
3.1. Scope
3.2. ResourceType
4. Quota
4.1. Properties of the Quota Object
4.2. Quota/get
4.3. Quota/changes
4.4. Quota/query
4.5. Quota/queryChanges
5. Examples
5.1. Fetching Quotas
5.2. Requesting Latest Quota Changes
6. Push
7. IANA Considerations
7.1. JMAP Capability Registration for "quota"
7.2. JMAP Data Type Registration for "Quota"
8. Security Considerations
9. Normative References
Acknowledgements
Author's Address
1. Introduction
The JSON Meta Application Protocol (JMAP) [RFC8620] is a generic
protocol for synchronizing data, such as mails, calendars, or
contacts between a client and a server. It is optimized for mobile
and web environments and aims to provide a consistent interface to
different data types.
This specification defines a data model for handling quotas over
JMAP, allowing a user to obtain details about a certain quota.
This specification does not address quota administration, which
should be handled by other means.
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.
Type signatures, examples, and property descriptions in this document
follow the conventions established in Section 1.1 of [RFC8620]. Data
types defined in the core specification are also used in this
document.
1.2. Terminology
This document reuses the terminology from the core JMAP specification
established in Section 1.6 of [RFC8620].
The term "Quota" (when capitalized) is used to refer to the data type
defined in Section 4 and instance of that data type.
2. Addition to the Capabilities Object
The capabilities object is returned as part of the JMAP Session
object; see [RFC8620], Section 2.
This document defines one additional capability URI.
2.1. urn:ietf:params:jmap:quota
This represents support for the Quota data type and associated API
methods. Servers supporting this specification MUST add a property
called "urn:ietf:params:jmap:quota" to the capabilities object.
The value of this property is an empty object in both the JMAP
Session capabilities property and an account's accountCapabilities
property.
3. Sub-types of the Quota Data Type
There are two fields within the Quota data type, which have an
enumerated set of possible values. These are:
3.1. Scope
The Scope data type is used to represent the entities the quota
applies to. It is defined as a "String" with values from the
following set:
* account: The quota information applies to just the client's
account.
* domain: The quota information applies to all accounts sharing this
domain.
* global: The quota information applies to all accounts belonging to
the server.
3.2. ResourceType
The ResourceType data type is used to act as a unit of measure for
the quota usage. It is defined as a "String" with values from the
following set:
* count: The quota is measured in a number of data type objects.
For example, a quota can have a limit of 50 "Mail" objects.
* octets: The quota is measured in size (in octets). For example, a
quota can have a limit of 25000 octets.
4. Quota
The Quota is an object that displays the limit set to an account
usage. It then shows as well the current usage in regard to that
limit.
4.1. Properties of the Quota Object
The Quota object MUST contain the following fields:
* id: Id
The unique identifier for this object.
* resourceType: String
The resource type of the quota as defined in Section 3.2.
* used: UnsignedInt
The current usage of the defined quota, using the "resourceType"
defined as unit of measure. Computation of this value is handled
by the server.
* hardLimit: UnsignedInt
The hard limit set by this quota, using the "resourceType" defined
as unit of measure. Objects in scope may not be created or
updated if this limit is reached.
* scope: String
The "Scope" of this quota as defined in Section 3.1.
* name: String
The name of the quota. Useful for managing quotas and using
queries for searching.
* types: String[]
A list of all the type names as defined in the "JMAP Types Names"
registry (e.g., Email, Calendar, etc.) to which this quota
applies. This allows the quotas to be assigned to distinct or
shared data types.
The server MUST filter out any types for which the client did not
request the associated capability in the "using" section of the
request. Further, the server MUST NOT return Quota objects for
which there are no types recognized by the client.
The Quota object MAY contain the following fields:
* warnLimit: UnsignedInt|null
The warn limit set by this quota, using the "resourceType" defined
as unit of measure. It can be used to send a warning to an entity
about to reach the hard limit soon, but with no action taken yet.
If set, it SHOULD be lower than the "softLimit" (if present and
different from null) and the "hardLimit".
* softLimit: UnsignedInt|null
The soft limit set by this quota, using the "resourceType" defined
as unit of measure. It can be used to still allow some operations
but refuse some others. What is allowed or not is up to the
server. For example, it could be used for blocking outgoing
events of an entity (sending emails, creating calendar events,
etc.) while still receiving incoming events (receiving emails,
receiving calendars events, etc.). If set, it SHOULD be higher
than the "warnLimit" (if present and different from null) but
lower than the "hardLimit".
* description: String|null
Arbitrary, free, human-readable description of this quota. It
might be used to explain where the different limits come from and
explain the entities and data types this quota applies to. The
description MUST be encoded in UTF-8 [RFC3629] as described in
[RFC8620], Section 1.5, and selected based on an Accept-Language
header in the request (as defined in [RFC9110], Section 12.5.4) or
out-of-band information about the user's language or locale.
The following JMAP methods are supported.
4.2. Quota/get
Standard "/get" method as described in [RFC8620], Section 5.1. The
_id_'s argument may be "null" to fetch all quotas of the account at
once, as demonstrated in Section 5.1.
4.3. Quota/changes
Standard "/changes" method as described in [RFC8620], Section 5.2,
but with one extra argument in the response:
* updatedProperties: String[]|null
If only the "used" Quota property has changed since the old state,
this will be a list containing only that property. If the server
is unable to tell if only "used" has changed, it MUST be null.
Since "used" frequently changes, but other properties are generally
only changed rarely, the server can help the client optimize data
transfer by keeping track of changes to quota usage separate from
other state changes. The updatedProperties array may be used
directly via a back-reference in a subsequent Quota/get call in the
same request, so only these properties are returned if nothing else
has changed.
Servers MAY decide to add other properties to the list that they
judge to be changing frequently.
This method's usage is demonstrated in Section 5.2.
4.4. Quota/query
This is a standard "/query" method as described in [RFC8620],
Section 5.5.
A FilterCondition object has the following properties, any of which
may be included or omitted:
* name: String
The Quota _name_ property contains the given string.
* scope: String
The Quota _scope_ property must match the given value exactly.
* resourceType: String
The Quota _resourceType_ property must match the given value
exactly.
* type: String
The Quota _types_ property contains the given value.
A Quota object matches the FilterCondition if, and only if, all the
given conditions match. If zero properties are specified, it is
automatically true for all objects.
The following Quota properties MUST be supported for sorting:
* name
* used
4.5. Quota/queryChanges
This is a standard "/queryChanges" method as described in [RFC8620],
Section 5.6.
5. Examples
5.1. Fetching Quotas
Request fetching all quotas related to an account:
[[ "Quota/get", {
"accountId": "u33084183",
"ids": null
}, "0" ]]
With response:
[[ "Quota/get", {
"accountId": "u33084183",
"state": "78540",
"list": [{
"id": "2a06df0d-9865-4e74-a92f-74dcc814270e",
"resourceType": "count",
"used": 1056,
"warnLimit": 1600,
"softLimit": 1800,
"hardLimit": 2000,
"scope": "account",
"name": "bob@example.com",
"description": "Personal account usage. When the soft limit is
reached, the user is not allowed to send mails or
create contacts and calendar events anymore.",
"types" : [ "Mail", "Calendar", "Contact" ]
}, {
"id": "3b06df0e-3761-4s74-a92f-74dcc963501x",
"resourceType": "octets",
...
}, ...],
"notFound": []
}, "0" ]]
5.2. Requesting Latest Quota Changes
Request fetching the changes for a specific quota:
[[ "Quota/changes", {
"accountId": "u33084183",
"sinceState": "78540",
"maxChanges": 20
}, "0" ],
[ "Quota/get", {
"accountId": "u33084183",
"#ids": {
"resultOf": "0",
"name": "Quota/changes",
"path": "/updated"
},
"#properties": {
"resultOf": "0",
"name": "Quota/changes",
"path": "/updatedProperties"
}
}, "1" ]]
With response:
[[ "Quota/changes", {
"accountId": "u33084183",
"oldState": "78540",
"newState": "78542",
"hasMoreChanges": false,
"updatedProperties": ["used"],
"created": [],
"updated": ["2a06df0d-9865-4e74-a92f-74dcc814270e"],
"destroyed": []
}, "0" ],
[ "Quota/get", {
"accountId": "u33084183",
"state": "10826",
"list": [{
"id": "2a06df0d-9865-4e74-a92f-74dcc814270e",
"used": 1246
}],
"notFound": []
}, "1" ]]
6. Push
Servers MUST support the JMAP push mechanisms, as specified in
[RFC8620], Section 7, to allow clients to receive notifications when
the state changes for the Quota type defined in this specification.
7. IANA Considerations
7.1. JMAP Capability Registration for "quota"
IANA has registered the "quota" JMAP Capability as follows:
Capability Name: urn:ietf:params:jmap:quota
Reference: RFC 9425
Intended Use: common
Change Controller: IETF
Security and Privacy Considerations: RFC 9425, Section 8
7.2. JMAP Data Type Registration for "Quota"
IANA has registered the "Quota" Data Type as follows:
Type Name: Quota
Can Reference Blobs: No
Can Use for State Change: Yes
Capability: urn:ietf:params:jmap:quota
Reference: RFC 9425
8. Security Considerations
All security considerations of JMAP [RFC8620] apply to this
specification.
Implementors should be careful to make sure the implementation of the
extension specified in this document does not violate the site's
security policy. The resource usage of other users is likely to be
considered confidential information and should not be divulged to
unauthorized persons.
As for any resource shared across users (for example, a quota with
the "domain" or "global" scope), a user that can consume the resource
can affect the resources available to the other users. For example,
a user could spam themselves with events and make the shared resource
hit the limit and unusable for others (implementors could mitigate
that with some rate-limiting implementation on the server).
Also, revealing domain and global quota counts to all users may cause
privacy leakage of other sensitive data, or at least the existence of
other sensitive data. For example, some users are part of a private
list belonging to the server, so they shouldn't know how many users
are in there. However, by comparing the quota count before and after
sending a message to the list, it could reveal the number of people
of the list, as the domain or global quota count would go up by the
number of people subscribed. In order to limit those attacks, quotas
with "domain" or "global" scope SHOULD only be visible to server
administrators and not to general users.
9. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <https://www.rfc-editor.org/info/rfc3629>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8620] Jenkins, N. and C. Newman, "The JSON Meta Application
Protocol (JMAP)", RFC 8620, DOI 10.17487/RFC8620, July
2019, <https://www.rfc-editor.org/info/rfc8620>.
[RFC9007] Ouazana, R., Ed., "Handling Message Disposition
Notification with the JSON Meta Application Protocol
(JMAP)", RFC 9007, DOI 10.17487/RFC9007, March 2021,
<https://www.rfc-editor.org/info/rfc9007>.
[RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/info/rfc9110>.
Acknowledgements
Thank you to Michael Bailly, who co-wrote the first draft version of
this document, before deciding to turn to other matters.
Thank you to Benoit Tellier for his constant help and support on
writing this document.
Thank you to Raphael Ouazana for sharing his own experience on how to
write an RFC after finalizing his own document: [RFC9007].
Thank you to Bron Gondwana, Neil Jenkins, Alexey Melnikov, Joris
Baum, and the people from the IETF JMAP working group in general, who
helped with extensive discussions, reviews, and feedback.
Thank you to the people in the IETF organization, who took the time
to read, understand, comment, and give great feedback in the last
rounds.
Author's Address
René Cordier (editor)
Linagora Vietnam
5 Dien Bien Phu
Hanoi
10000
Vietnam
Email: rcordier@linagora.com
URI: https://linagora.vn
