Internet Engineering Task Force (IETF) N. Jenkins, Ed.
Request for Comments: 9670 Fastmail
Updates: 8620 November 2024
Category: Standards Track
ISSN: 2070-1721
JSON Meta Application Protocol (JMAP) Sharing
Abstract
This document specifies a data model for sharing data between users
using the JSON Meta Application Protocol (JMAP). Future documents
can reference this document when defining data types to support a
consistent model of sharing.
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/rfc9670.
Copyright Notice
Copyright (c) 2024 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
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Table of Contents
1. Introduction
1.1. Notational Conventions
1.2. Terminology
1.3. Data Model Overview
1.4. Subscribing to Shared Data
1.5. Addition to the Capabilities Object
1.5.1. urn:ietf:params:jmap:principals
1.5.2. urn:ietf:params:jmap:principals:owner
2. Principals
2.1. Principal/get
2.2. Principal/changes
2.3. Principal/set
2.4. Principal/query
2.4.1. Filtering
2.5. Principal/queryChanges
3. ShareNotifications
3.1. ShareNotification/get
3.2. ShareNotification/changes
3.3. ShareNotification/set
3.4. ShareNotification/query
3.4.1. Filtering
3.4.2. Sorting
3.5. ShareNotification/queryChanges
4. Framework for Shared Data
4.1. Example
5. Internationalization Considerations
6. Security Considerations
6.1. Spoofing
6.2. Unnoticed Sharing
6.3. Denial of Service
6.4. Unauthorized Principals
7. IANA Considerations
7.1. JMAP Capability Registration for "principals"
7.2. JMAP Capability Registration for "principals:owner"
7.3. JMAP Data Type Registration for "Principal"
7.4. JMAP Data Type Registration for "ShareNotification"
8. References
8.1. Normative References
8.2. Informative References
Author's Address
1. Introduction
The JSON Meta Application Protocol (JMAP) [RFC8620] is a generic
protocol for synchronizing data, such as mail, calendars, or
contacts, between a client and a server. It is optimized for mobile
and web environments and provides a consistent interface to query,
read, and modify different data types, including comprehensive error
handling.
This specification defines a data model to represent entities in a
collaborative environment and a framework for sharing data between
them that can be used to provide a consistent sharing model for
different data types. It does not define _what_ may be shared or the
granularity of permissions, as this will depend on the data in
question.
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.
Examples of API exchanges only show the methodCalls array of the
Request object or the methodResponses array of the Response object.
For compactness, the rest of the Request/Response object is omitted.
1.2. Terminology
The same terminology is used in this document as in the core JMAP
specification. See [RFC8620], Section 1.6.
The terms "Principal" and "ShareNotification" (with this specific
capitalization) are used to refer to the data types defined in this
document and instances of those data types.
1.3. Data Model Overview
A Principal (see Section 2) represents an individual, team, or
resource (e.g., a room or projector). The object contains
information about the entity being represented, such as a name,
description, and time zone. It may also hold domain-specific
information. A Principal may be associated with zero or more
Accounts (see [RFC8620], Section 1.6.2) containing data belonging to
the Principal. Managing the set of Principals within a system is out
of scope for this specification, as it is highly domain specific. It
is likely to map directly from a directory service or other user
management system.
Data types may allow users to share data with others by assigning
permissions to Principals. When a user's permissions are changed, a
ShareNotification object is created for them so a client can inform
the user of the changes.
1.4. Subscribing to Shared Data
Permissions determine whether a user _may_ access data but not
whether they _want_ to. Some shared data is of equal importance as
the user's own, while other data is just there should the user wish
to explicitly go find it. Clients will often want to differentiate
the two. For example, a company may share mailing list archives for
all departments with all employees, but a user may only generally be
interested in the few they belong to. They would have _permission_
to access many mailboxes but can _subscribe_ to just the ones they
care about. The client would provide separate interfaces for reading
mail in subscribed mailboxes and browsing all mailboxes they have
permission to access in order to manage those that they are
subscribed to.
The JMAP Session object (see [RFC8620], Section 2) is defined to
include an object in the "accounts" property for every Account that
the user has access to. Collaborative systems may share data between
a very large number of Principals, most of which the user does not
care about day to day. For servers implementing this specification,
the Session object MUST only include Accounts where either the user
is subscribed to at least one record (see [RFC8620], Section 1.6.3)
in the Account or the Account belongs to the user. StateChange
events ([RFC8620], Section 7.1) for changes to data SHOULD only be
sent for data the user has subscribed to and MUST NOT be sent for any
Account where the user is not subscribed to any records in the
Account, except where that Account belongs to the user.
The server MAY reject the user's attempt to subscribe to some
resources even if they have permission to access them (e.g., a
calendar representing a location).
A user can query the set of Principals they have access to with
"Principal/query" (see Section 2.4). The Principal object will
contain an Account object for all Accounts where the user has
permission to access data for that Principal, even if they are not
yet subscribed.
1.5. Addition to the Capabilities Object
The capabilities object is returned as part of the JMAP Session
object; see [RFC8620], Section 2. This document defines two
additional capability URIs.
1.5.1. urn:ietf:params:jmap:principals
The urn:ietf:params:jmap:principals capability represents support for
the Principal and ShareNotification data types and associated API
methods.
The value of this property in the JMAP Session "capabilities"
property is an empty object.
The value of this property in an Account's "accountCapabilities"
property is an object that MUST contain the following information on
server capabilities and permissions for that Account:
*currentUserPrincipalId*: Id|null
The id of the Principal in this Account that corresponds to the
user fetching this object, if any.
1.5.2. urn:ietf:params:jmap:principals:owner
The URI urn:ietf:params:jmap:principals:owner is solely used as a key
in an Account's "accountCapabilities" property. It does not appear
in the JMAP Session capabilities -- support is indicated by the
urn:ietf:params:jmap:principals URI being present in the session
capabilities.
If urn:ietf:params:jmap:principals:owner is a key in an Account's
"accountCapabilities" property, that Account (and the data therein)
is owned by a Principal. Some Accounts may not be owned by a
Principal (e.g., the Account that contains the data for the
Principals themselves), in which case this property is omitted.
The value of this property is an object with the following
properties:
*accountIdForPrincipal*: Id
The id of an Account with the urn:ietf:params:jmap:principals
capability that contains the corresponding Principal object.
*principalId*:Id
The id of the Principal that owns this Account.
2. Principals
A Principal represents an individual, a group, a location (e.g., a
room), a resource (e.g., a projector), or another entity in a
collaborative environment. Sharing in JMAP is generally configured
by assigning rights to certain data within an Account to other
Principals. For example, a user may assign permission to read their
calendar to a Principal representing another user or their team.
In a shared environment, such as a workplace, a user may have access
to a large number of Principals.
In most systems, the user will have access to a single Account
containing Principal objects. In some situations, for example, when
aggregating data from different places, there may be multiple
Accounts containing Principal objects.
A *Principal* object has the following properties:
*id*: Id (immutable; server-set)
The id of the Principal.
*type*: String
This MUST be one of the following values:
* "individual": This represents a single person.
* "group": This represents a group of other Principals.
* "resource": This represents some resource, e.g., a projector.
* "location": This represents a location.
* "other": This represents some other undefined Principal.
*name*: String
The name of the Principal, e.g., "Jane Doe" or "Room 4B".
*description*: String|null
A longer description of the Principal, for example, details about
the facilities of a resource, or null if no description is
available.
*email*: String|null
An email address for the Principal, or null if no email is
available. If given, the value MUST conform to the "addr-spec"
syntax, as defined in [RFC5322], Section 3.4.1.
*timeZone*: String|null
The time zone for this Principal, if known. If not null, the
value MUST be a time zone name from the IANA Time Zone Database
[IANA-TZDB].
*capabilities*: String[Object] (server-set)
A map of JMAP capability URIs to domain-specific information about
the Principal in relation to that capability, as defined in the
document that registered the capability.
*accounts*: Id[Account]|null (server-set)
A map of Account id to Account object for each JMAP Account
containing data for this Principal that the user has access to, or
null if none.
2.1. Principal/get
This is a standard "/get" method as described in [RFC8620],
Section 5.1.
2.2. Principal/changes
This is a standard "/changes" method as described in [RFC8620],
Section 5.2.
| Note: Implementations backed by an external directory may be
| unable to calculate changes. In this case, they will always
| return a "cannotCalculateChanges" error as described in the
| core JMAP specification.
2.3. Principal/set
This is a standard "/set" method as described in [RFC8620],
Section 5.3.
Managing Principals is likely tied to a directory service or some
other vendor-specific solution. This management may occur out of
band or via an additional capability defined elsewhere. Allowing
direct user modification of properties has security considerations,
as noted in Section 6. A server MUST reject any change it doesn't
allow with a "forbidden" SetError.
Where a server does support changes via this API, it SHOULD allow an
update to the "name", "description", and "timeZone" properties of the
Principal with the same id as the "currentUserPrincipalId" in the
Account capabilities. This allows the user to update their own
details.
2.4. Principal/query
This is a standard "/query" method as described in [RFC8620],
Section 5.5.
2.4.1. Filtering
A *FilterCondition* object has the following properties, all of which
are optional:
*accountIds*: String[]
A list of Account ids. The Principal matches if any of the ids in
this list are keys in the Principal's "accounts" property (i.e.,
if any of the Account ids belong to the Principal).
*email*: String
The email property of the Principal contains the given string.
*name*: String
The name property of the Principal contains the given string.
*text*: String
The name, email, or description property of the Principal contains
the given string.
*type*: String
The type must be exactly as given to match the condition.
*timeZone*: String
The timeZone must be exactly as given to match the condition.
All given conditions in the FilterCondition object must match for the
Principal to match.
Text matches for "contains" SHOULD be simple substring matches.
2.5. Principal/queryChanges
This is a standard "/queryChanges" method as described in [RFC8620],
Section 5.6.
| Note: Implementations backed by an external directory may be
| unable to calculate changes. In this case, they will always
| return a "cannotCalculateChanges" error as described in the
| core JMAP specification.
3. ShareNotifications
The ShareNotification data type records when the user's permissions
to access a shared object changes. ShareNotifications are only
created by the server; users cannot create them explicitly. They are
stored in the same Account as the Principals.
Clients may present the list of notifications to the user and allow
the user to dismiss them. To dismiss a notification, use a standard
"/set" call to destroy it.
The server SHOULD create a ShareNotification whenever the user's
permissions change on an object. It MAY choose not to create a
notification for permission changes to a group Principal, even if the
user is in the group, if this is more likely to be overwhelming than
helpful, or if it would create excessive notifications within the
system.
The server MAY limit the maximum number of notifications it will
store for a user. When the limit is reached, any new notification
will cause the previously oldest notification to be automatically
deleted.
The server MAY coalesce notifications if appropriate or remove
notifications after a certain period of time or that it deems are no
longer relevant.
A *ShareNotification* object has the following properties:
*id*: String (immutable; server-set)
The id of the ShareNotification.
*created*: UTCDate (immutable; server-set)
The time this notification was created.
*changedBy*: Entity (immutable; server-set)
Who made the change. An *Entity* object has the following
properties:
*name*: String
The name of the entity who made the change.
*email*: String|null
The email of the entity who made the change, or null if no
email is available.
*principalId*: Id|null
The id of the Principal corresponding to the entity who made
the change, or null if no associated Principal.
*objectType*: String (immutable; server-set)
The name of the data type for the object whose permissions have
changed, as registered in the IANA "JMAP Data Types" registry
[IANA-JMAP], e.g., "Calendar" or "Mailbox".
*objectAccountId*: Id (immutable; server-set)
The id of the Account where this object exists.
*objectId*: Id (immutable; server-set)
The id of the object that this notification is about.
*oldRights*: String[Boolean]|null (immutable; server-set)
The "myRights" property of the object for the user before the
change.
*newRights*: String[Boolean]|null (immutable; server-set)
The "myRights" property of the object for the user after the
change.
*name*: String (immutable; server-set)
The name of the object at the time the notification was made.
Determining the name will depend on the data type in question.
For example, it might be the "title" property of a CalendarEvent
or the "name" of a Mailbox. The name is to show users who have
had their access rights to the object removed what it is that they
can no longer access.
3.1. ShareNotification/get
This is a standard "/get" method as described in [RFC8620],
Section 5.1.
3.2. ShareNotification/changes
This is a standard "/changes" method as described in [RFC8620],
Section 5.2.
3.3. ShareNotification/set
This is a standard "/set" method as described in [RFC8620],
Section 5.3.
Only destroy is supported; any attempt to create/update MUST be
rejected with a "forbidden" SetError.
3.4. ShareNotification/query
This is a standard "/query" method as described in [RFC8620],
Section 5.5.
3.4.1. Filtering
A *FilterCondition* object has the following properties, all of which
are optional:
*after*: UTCDate|null
The creation date must be on or after this date to match the
condition.
*before*: UTCDate|null
The creation date must be before this date to match the condition.
*objectType*: String
The objectType value must be identical to the given value to match
the condition.
*objectAccountId*: Id
The objectAccountId value must be identical to the given value to
match the condition.
All given conditions in the FilterCondition object must match for the
ShareNotification to match.
3.4.2. Sorting
The "created" property MUST be supported for sorting.
3.5. ShareNotification/queryChanges
This is a standard "/queryChanges" method as described in [RFC8620],
Section 5.6.
4. Framework for Shared Data
Shareable data types MUST define the following three properties:
*isSubscribed*: Boolean
The value true indicates that the user wishes to subscribe to see
this data. The value false indicates that the user does not wish
to subscribe to see this data. The initial value for this
property when data is shared by another user is implementation
dependent, although data types may give advice on appropriate
defaults.
*myRights*: String[Boolean]
The set of permissions the user currently has. Appropriate
permissions are domain specific and must be defined per data type.
Each key is the name of a permission defined for that data type.
The value for the key is true if the user has the permission or
false if they do not.
*shareWith*: Id[String[Boolean]]|null
The value of this property is null if the data is not shared with
anyone. Otherwise, it is a map where each key is the id of a
Principal with which this data is shared, and the value associated
with that key is the rights to give that Principal, in the same
format as the "myRights" property. The Account id for the
Principal id can be found in the capabilities of the Account this
object is in (see Section 1.5.2).
Users with appropriate permission may set this property to modify
who the data is shared with. The Principal that owns the Account
that this data is in MUST NOT be in the map, since the owner's
rights are implicit.
4.1. Example
Suppose we are designing a data model for a very simple to-do list.
There is a Todo data type representing a single item to do, each of
which belongs to a single TodoList. The specification makes the
TodoLists shareable by referencing this document and defining the
common properties.
First, it would define a set of domain-specific rights. For example,
a TodoListRights object may have the following properties:
*mayRead*: Boolean
The user may fetch this TodoList and any Todos that belong to this
TodoList.
*mayWrite*: Boolean
The user may create, update, or destroy Todos that belong to this
TodoList and may change the "name" property of this TodoList.
*mayAdmin*: Boolean
The user may see and modify the "myRights" property of this
TodoList and may destroy this TodoList.
Then in the TodoList data type, we would include the three common
properties described in Section 4, in addition to any type-specific
properties (like "name" in this case):
*id*: Id (immutable; server-set)
The id of the object.
*name*: String
A name for this list of Todos.
*isSubscribed*: Boolean
True if the user has indicated they wish to see this list. If
false, clients should not display this TodoList with the user's
other TodoLists but should provide a means for users to see and
subscribe to all TodoLists that have been shared with them.
*myRights*: TodoListRights
The set of permissions the user currently has for this TodoList.
*shareWith*: Id[TodoListRights]|null
If not shared with anyone, the value is null. Otherwise, it's a
map where the keys are Principal ids and the values are the rights
given to those Principals. Users with the "mayAdmin" right may
set this property to modify who the data is shared with. The
Principal that owns the Account that this data is in MUST NOT be
in the map; their rights are implicit.
We would also define a new Principal capability with two properties:
*accountId*: Id|null
The accountId containing the Todo data for this Principal, if it
has been shared with the requesting user.
*mayShareWith*: Boolean
The user may give this Principal permission to access a TodoList.
A client wishing to let the user configure sharing would look at the
"capabilities" for the Account containing the user's Todo data and
find the "urn:ietf:params:jmap:principals:owner" property, as per
Section 1.5.2. For example, the JMAP Session object might contain:
{
"accounts": {
"u12345678": {
"name": "jane.doe@example.com",
"isPersonal": true,
"isReadOnly": false,
"accountCapabilities": {
"urn:com.example:jmap:todo": {},
"urn:ietf:params:jmap:principals:owner": {
"accountIdForPrincipal": "u33084183",
"principalId": "P105aga511jaa"
}
}
},
...
},
...
}
Figure 1: Part of a JMAP Session Object
From this, the client now knows which Account has the Principal data,
and it can fetch the list of Principals and offer to share it with
the user by making an API request like this:
[[ "Principal/get", {
"accountId": "u33084183",
"ids": null
}, "0" ]]
Figure 2: "methodCalls" Property of a JMAP Request
Here's an example response (where "Joe Bloggs" is another user that
this user could share their TodoList with; Joe has not shared any of
their own data with this user, so the "accounts" property is null):
[[ "Principal/get", {
"accountId": "u33084183",
"state": "7b8eff5zz",
"list": [{
"id": "P2342fnddd20",
"type": "individual",
"name": "Joe Bloggs",
"description": null,
"email": "joe.bloggs@example.com",
"timeZone": "Australia/Melbourne",
"capabilities": {
"urn:com.example:jmap:todo": {
"accountId": null,
"mayShareWith": true
}
},
"accounts": null
}, {
"id": "P674pp24095qo49pr",
"name": "Board room",
"type": "location",
...
}, ... ],
"notFound": []
}, "0" ]]
Figure 3: "methodResponses" Property of a JMAP Response
A TodoList can be shared with "Joe Bloggs" by updating its shareWith
property, as in this example request:
[[ "TodoList/set", {
"accountId": "u12345678",
"update": {
"tl01n231": {
"shareWith": {
"P2342fnddd20": {
"mayRead": true,
"mayWrite": true,
"mayAdmin": false
}
}
}
}
}, "0" ]]
Figure 4: "methodCalls" Property of a JMAP Request
5. Internationalization Considerations
Experience has shown that unrestricted use of Unicode can lead to
problems such as inconsistent rendering, users reading text and
interpreting it differently than intended, and unexpected results
when copying text from one location to another. Servers MAY choose
to mitigate this by restricting the set of characters allowed in
otherwise unconstrained String fields. The FreeformClass, as
documented in [RFC8264], Section 4.3, might be a good starting point
for this.
Attempts to set a value containing code points outside of the
permissible set can be handled in a few ways by the server. The
first option is to simply strip the forbidden characters and store
the resulting string. This is likely to be appropriate for control
characters, for example, where they can end up in data accidentally
due to copy-and-paste issues and are probably invisible to the end
user. JMAP allows the server to transform data on create/update, as
long as any changed properties are returned to the client in the
"/set" response so it knows what has changed, as per [RFC8620],
Section 5.3. Alternatively, the server MAY just reject the create/
update with an "invalidProperties" SetError.
6. Security Considerations
All security considerations of JMAP [RFC8620] apply to this
specification. Additional considerations are detailed below.
6.1. Spoofing
Allowing users to edit their own Principal's name (and, to a lesser
extent, email, description, or type) could allow a user to change
their Principal to look like another user in the system, potentially
tricking others into sharing private data with them. Servers may
choose to forbid this and SHOULD keep logs of such changes to provide
an audit trail.
Note that simply forbidding the use of a name already in the system
is insufficient protection, as a malicious user could still change
their name to something easily confused with the existing name by
using trivial misspellings or visually similar Unicode characters.
6.2. Unnoticed Sharing
Sharing data with another user allows someone to turn a transitory
account compromise (e.g., brief access to an unlocked or logged-in
client) into a persistent compromise (by setting up sharing with a
user that is controlled by the attacker). This can be mitigated by
requiring further authorization for configuring sharing or sending
notifications to the sharer via another channel whenever a new
permission is added.
6.3. Denial of Service
By creating many changes to the sharing status of objects, a user can
cause many ShareNotifications to be generated, which could lead to
resource exhaustion. Servers can mitigate this by coalescing
multiple changes to the same object into a single notification,
limiting the maximum number of notifications it stores per user and/
or rate-limiting the changes to sharing permissions in the first
place. Automatically deleting older notifications after reaching a
limit can mean the user is not made aware of a sharing change, which
can itself be a security issue. For this reason, it is better to
coalesce changes and use other mitigation strategies.
6.4. Unauthorized Principals
The set of Principals within a shared environment MUST be strictly
controlled. If adding a new Principal is open to the public, risks
include:
* An increased risk of a user accidentally sharing data with an
unintended person.
* An attacker sharing unwanted or offensive information with the
user.
* An attacker sharing items with spam content in the names in order
to generate ShareNotification objects, which are likely to be
prominently displayed to the user receiving them.
7. IANA Considerations
7.1. JMAP Capability Registration for "principals"
IANA has registered "principals" in the "JMAP Capabilities" registry
as follows:
Capability Name: urn:ietf:params:jmap:principals
Intended Use: common
Change Controller: IETF
Security and Privacy Considerations: RFC 9670, Section 6
Reference: RFC 9670
7.2. JMAP Capability Registration for "principals:owner"
IANA has registered "principals:owner" in the "JMAP Capabilities"
registry as follows:
Capability Name: urn:ietf:params:jmap:principals:owner
Intended Use: common
Change Controller: IETF
Security and Privacy Considerations: RFC 9670, Section 6
Reference: RFC 9670
7.3. JMAP Data Type Registration for "Principal"
IANA has registered "Principal" in the "JMAP Data Types" registry as
follows:
Type Name: Principal
Can Reference Blobs: No
Can Use for State Change: Yes
Capability: urn:ietf:params:jmap:principals
Reference: RFC 9670
7.4. JMAP Data Type Registration for "ShareNotification"
IANA has registered "ShareNotification" in the "JMAP Data Types"
registry as follows:
Type Name: ShareNotification
Can Reference Blobs: No
Can Use for State Change: Yes
Capability: urn:ietf:params:jmap:principals
Reference: RFC 9670
8. References
8.1. 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>.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
DOI 10.17487/RFC5322, October 2008,
<https://www.rfc-editor.org/info/rfc5322>.
[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>.
8.2. Informative References
[IANA-JMAP]
IANA, "JMAP Data Types",
<https://www.iana.org/assignments/jmap>.
[IANA-TZDB]
IANA, "Time Zone Database",
<https://www.iana.org/time-zones>.
[RFC8264] Saint-Andre, P. and M. Blanchet, "PRECIS Framework:
Preparation, Enforcement, and Comparison of
Internationalized Strings in Application Protocols",
RFC 8264, DOI 10.17487/RFC8264, October 2017,
<https://www.rfc-editor.org/info/rfc8264>.
Author's Address