JMAP Sharing
draft-ietf-jmap-sharing-03

JMAP                                                   N.M. Jenkins, Ed.
Internet-Draft                                                  Fastmail
Intended status: Standards Track                           31 March 2023
Expires: 2 October 2023

                              JMAP Sharing
                       draft-ietf-jmap-sharing-03

Abstract

   This document specifies a data model for sharing data between users
   using JMAP.  Specifications for other data types can reference this
   document to support a consistent model of sharing.

Status of This Memo

   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 2 October 2023.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.3.  Data Model Overview . . . . . . . . . . . . . . . . . . .   3
     1.4.  Subscriptions . . . . . . . . . . . . . . . . . . . . . .   4
     1.5.  Addition to the Capabilities Object . . . . . . . . . . .   4
       1.5.1.  urn:ietf:params:jmap:principals . . . . . . . . . . .   4
       1.5.2.  urn:ietf:params:jmap:principals:owner . . . . . . . .   5
   2.  Principals  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     2.1.  Principal/get . . . . . . . . . . . . . . . . . . . . . .   6
     2.2.  Principal/changes . . . . . . . . . . . . . . . . . . . .   6
     2.3.  Principal/set . . . . . . . . . . . . . . . . . . . . . .   6
     2.4.  Principal/query . . . . . . . . . . . . . . . . . . . . .   7
       2.4.1.  Filtering . . . . . . . . . . . . . . . . . . . . . .   7
     2.5.  Principal/queryChanges  . . . . . . . . . . . . . . . . .   7
   3.  Share Notifications . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Auto-deletion of Notifications  . . . . . . . . . . . . .   8
     3.2.  Object Properties . . . . . . . . . . . . . . . . . . . .   8
     3.3.  ShareNotification/get . . . . . . . . . . . . . . . . . .   9
     3.4.  ShareNotification/changes . . . . . . . . . . . . . . . .   9
     3.5.  ShareNotification/set . . . . . . . . . . . . . . . . . .   9
     3.6.  ShareNotification/query . . . . . . . . . . . . . . . . .   9
       3.6.1.  Filtering . . . . . . . . . . . . . . . . . . . . . .   9
       3.6.2.  Sorting . . . . . . . . . . . . . . . . . . . . . . .  10
     3.7.  ShareNotification/queryChanges  . . . . . . . . . . . . .  10
   4.  Framework for shared data . . . . . . . . . . . . . . . . . .  10
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
     5.1.  Spoofing  . . . . . . . . . . . . . . . . . . . . . . . .  10
     5.2.  Unnoticed sharing . . . . . . . . . . . . . . . . . . . .  11
     5.3.  Unauthorised principals . . . . . . . . . . . . . . . . .  11
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
     6.1.  JMAP Capability Registration for "principals" . . . . . .  11
     6.2.  JMAP Capability Registration for "principals:owner" . . .  11
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .  12
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   JMAP ([RFC8620] JSON Meta Application Protocol) 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 aims to provide a consistent interface to different
   data types.

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   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.

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 these specific
   capitalizations) 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.

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1.4.  Subscriptions

   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 their subscriptions.

   The JMAP Session object (see [RFC8620], Section 2) typically includes
   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.  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 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 may query the set of Principals they have access to with
   "Principal/query" (see Section 2.4).  The Principal object may then
   provide Account objects if 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

   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.

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   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

   This URI is solely used as a key in an account’s accountCapabilities
   property; it does not appear in the JMAP Session capabilities.
   Support is implied by the urn:ietf:params:jmap:principals session
   capability.

   If present, the account (and 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, group, location (e.g., a room),
   resource (e.g., a projector) or other 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, but they may have access to multiple
   if, for example, aggregating data from different places.

   A *Principal* object has the following properties:

   *  *id*: Id (immutable; server-set)

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      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 people.
      -  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 available.
   *  *email*: String|null
      An email address for the principal, or null if no email is
      available.
   *  *timeZone*: String|null
      The time zone for this principal, if known.  If not null, the
      value MUST be a time zone id from the IANA Time Zone Database TZDB
      (https://www.iana.org/time-zones).
   *  *capabilities*: String[Object]
      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
      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.

2.3.  Principal/set

   This is a standard "/set" method as described in [RFC8620],
   Section 5.3.

   Users SHOULD be allowed to update the "name", "description" and
   "timeZone" properties of the Principal with the same id as the
   "currentUserPrincipalId" in the Account capabilities.

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   However, the server may reject this change, and probably will reject
   any other change, with a forbidden SetError.  Managing principals is
   likely tied to a directory service or some other vendor-specific
   solution, and may occur out-of-band, or via an additional capability
   defined elsewhere.

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:

   *  *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
      Looks for the text in the email property.
   *  *name*: String
      Looks for the text in the name property.
   *  *text* String
      Looks for the text in the name, email, and description properties.
   *  *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 conditions in the FilterCondition object must match for the
   Principal to match.

2.5.  Principal/queryChanges

   This is a standard "/queryChanges" method as described in [RFC8620],
   Section 5.6.

3.  Share Notifications

   The ShareNotification data type records when the user's permissions
   to access a shared object changes.  ShareNotification are only
   created by the server; users cannot create them explicitly.
   Notifications are stored in the same Account as the Principals.

   Clients SHOULD present the list of notifications to the user and
   allow them to dismiss them.  To dismiss a notification you use a
   standard "/set" call to destroy it.

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   The server SHOULD create a ShareNotification whenever the user's
   permissions change on an object.  It SHOULD NOT create a notification
   for permission changes to a group principal, even if the user is in
   the group.

3.1.  Auto-deletion of Notifications

   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 that it deems are no longer relevant or after a certain
   period of time.  The server SHOULD automatically destroy a
   notification about an object if the user subscribes to that object.

3.2.  Object Properties

   The *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*: Person (immutable; server-set)
      Who made the change.
      -  *name*: String
         The name of the person who made the change.
      -  *email*: String|null
         The email of the person who made the change, or null if no
         email is available.
      -  *principalId*: String|null
         The id of the Principal corresponding to the person 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, e.g., "Calendar" or "Mailbox".
   *  *objectAccountId*: String (immutable; server-set)
      The id of the account where this object exists.
   *  *objectId*: String (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.

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   *  *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, and is implementation specific.  The name is
      to show to users who have had their access rights to the object
      removed, so that they know what it is they can no longer access.

3.3.  ShareNotification/get

   This is a standard "/get" method as described in [RFC8620],
   Section 5.1.

3.4.  ShareNotification/changes

   This is a standard "/changes" method as described in [RFC8620],
   Section 5.2.

3.5.  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.

3.6.  ShareNotification/query

   This is a standard "/query" method as described in [RFC8620],
   Section 5.5.

3.6.1.  Filtering

   A *FilterCondition* object has the following properties:

   *  *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*: String
      The objectAccountId value must be identical to the given value to
      match the condition.

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3.6.2.  Sorting

   The "created" property MUST be supported for sorting.

3.7.  ShareNotification/queryChanges

   This is a standard "/queryChanges" method as described in [RFC8620],
   Section 5.6.

4.  Framework for shared data

   Shareable data types SHOULD define the following three properties:

   *  *isSubscribed*: Boolean
      Has the user indicated they wish to see this data?  The initial
      value for this 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
      A map of principal id to rights to give that principal (in the
      same format as the myRights property), or null if not shared with
      anyone.  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
      this data is in MUST NOT be in the set of sharees; their rights
      are implicit.

5.  Security Considerations

   All security considerations of JMAP [RFC8620] apply to this
   specification.  Additional considerations are detailed below.

5.1.  Spoofing

   Allowing users to edit their own Principal's name (and, to a lesser
   extent, description) could allow a user to change their name to that
   of 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.

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5.2.  Unnoticed sharing

   Sharing data with another user allows someone to turn a transitory
   account compromise (e.g., brief access to an unlocked, logged in
   client) into a persistant compromise (by setting up sharing with a
   user controlled by the attacker).  This can be mitigated by requiring
   further authorisation for configuring sharing, or sending
   notifications to the sharer via another channel whenever a new sharee
   is added.

5.3.  Unauthorised principals

   The set of principals within a shared environment SHOULD 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 may share unwanted or offensive information with the
      user.
   *  An attacker may share items with spam content in the names in
      order to generate ShareNotification objects, which are likely to
      be prominently displayed to the sharee.

6.  IANA Considerations

6.1.  JMAP Capability Registration for "principals"

   IANA will register the "principals" JMAP Capability as follows:

   Capability Name: urn:ietf:params:jmap:principals

   Specification document: this document

   Intended use: common

   Change Controller: IETF

   Security and privacy considerations: this document, Section 5

6.2.  JMAP Capability Registration for "principals:owner"

   IANA will register the "principals:owner" JMAP Capability as follows:

   Capability Name: urn:ietf:params:jmap:principals:owner

   Specification document: this document

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   Intended use: common

   Change Controller: IETF

   Security and privacy considerations: this document, Section 5

7.  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>.

   [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>.

Author's Address

   Neil Jenkins (editor)
   Fastmail
   PO Box 234, Collins St West
   Melbourne  VIC 8007
   Australia
   Email: neilj@fastmailteam.com
   URI:   https://www.fastmail.com

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