Spec for MSC4380: Invite blocking (#2305)

Signed-off-by: Kévin Commaille <zecakeh@tedomum.fr>

changelogs/client_server/newsfragments/2305.feature

@@ -0,0 +1 @@
+Add invite blocking, as per [MSC4380](https://github.com/matrix-org/matrix-spec-proposals/pull/4380).

content/client-server-api/_index.md

@@ -4071,6 +4071,7 @@ that profile.
 | [Sticker Messages](#sticker-messages)                      | Optional  | Optional | Optional | Optional | Optional |
 | [Third-party Networks](#third-party-networks)              | Optional  | Optional | Optional | Optional | Optional |
 | [Threading](#threading)                                    | Optional  | Optional | Optional | Optional | Optional |
+| [Invite permission](#invite-permission)                    | Optional  | Optional | Optional | Optional | Optional |
 
 *Please see each module for more details on what clients need to
 implement.*
@@ -4144,6 +4145,7 @@ systems.
 {{% cs-module name="SSO client login/authentication" filename="sso_login" %}}
 {{% cs-module name="Direct Messaging" filename="dm" %}}
 {{% cs-module name="Ignoring Users" filename="ignore_users" %}}
+{{% cs-module name="Invite permission" filename="invite_permission" %}}
 {{% cs-module name="Sticker Messages" filename="stickers" %}}
 {{% cs-module name="Reporting Content" filename="report_content" %}}
 {{% cs-module name="Third-party Networks" filename="third_party_networks" %}}

content/client-server-api/modules/invite_permission.md

@@ -0,0 +1,51 @@
+
+### Invite permission
+
+{{% added-in v="1.18" %}}
+
+Users may want to control who is allowed to invite them to new rooms. This module defines how
+clients and servers can implement invite permission.
+
+#### Account data
+
+{{% event event="m.invite_permission_config" %}}
+
+#### Client behaviour
+
+To reject invites from all users automatically, clients MAY add an [`m.invite_permission_config`](#minvite_permission_config)
+event in the user's [account data](#client-config) with the `default_action` property set to
+`block`. To stop rejecting all invites, the same event without the `default_action` property MUST be
+added to the account data.
+
+When the `default_action` field is unset, other parts of the specification might still have effects
+on invites seen by clients, like [ignoring users](#ignoring-users).
+
+Attempting to send an invite to a user that blocks invites will result in an error response with the
+`M_INVITE_BLOCKED` error code.
+
+#### Server behaviour
+
+When invites to a given user are blocked, the user's homeserver MUST respond to the following
+endpoints with an HTTP 403 status code, with the Matrix error code `M_INVITE_BLOCKED`, if the user
+is invited:
+
+* [`PUT /_matrix/federation/v1/invite/{roomId}/{eventId}`](/server-server-api/#put_matrixfederationv1inviteroomideventid)
+* [`PUT /_matrix/federation/v2/invite/{roomId}/{eventId}`](/server-server-api/#put_matrixfederationv2inviteroomideventid)
+* [`POST /_matrix/client/v3/rooms/{roomId}/invite`](#post_matrixclientv3roomsroomidinvite)
+* [`POST /_matrix/client/v3/createRoom`](#post_matrixclientv3createroom), due to a user in the
+  `invite` list. It is possible for one of the invited users to be rejected whilst the room creation
+  as a whole succeeds.
+* [`PUT /_matrix/client/v3/rooms/{roomId}/state/m.room.member/{stateKey}`](#put_matrixclientv3roomsroomidstateeventtypestatekey),
+  when the `membership` is set to `invite`.
+
+In addition, invite events for this user already in the database, or received over federation, MUST
+NOT be served over client synchronisation endpoints such as [`GET /sync`](#get_matrixclientv3sync).
+ 
+Servers MAY return any suppressed invite events over `GET /sync` if invite blocking is later
+disabled.
+ 
+Other endpoints, such as [`GET /rooms/{roomId}/state`](#get_matrixclientv3roomsroomidstate), are not
+affected by invite blocking: invite events are returned as normal.
+ 
+The Application Services API is also unaffected by invite blocking: invite events are sent over
+[`PUT /_matrix/app/v1/transactions/{txnId}`](/application-service-api/#put_matrixappv1transactionstxnid).

data/api/client-server/create_room.yaml

@@ -250,7 +250,6 @@ paths:
                   }
         "400":
           description: |-
-
             The request is invalid. A meaningful `errcode` and description
             error text will be returned. Example reasons for rejection include:
 
@@ -274,6 +273,17 @@ paths:
             application/json:
               schema:
                 $ref: definitions/errors/error.yaml
+        "403":
+          description: |-
+            Creating the room is not allowed.
+
+            {{% added-in v="1.18"%}} The `M_INVITE_BLOCKED` error code is used to
+            indicate that one of the homeservers of the invited users rejected
+            the invite due to [invite blocking](/client-server-api/#invite-permission).
+          content:
+            application/json:
+              schema:
+                $ref: definitions/errors/error.yaml
       tags:
         - Room creation
 servers:

data/api/client-server/inviting.yaml

@@ -83,7 +83,7 @@ paths:
                   value: {}
         "400":
           description: |-
-            
+
             The request is invalid. A meaningful `errcode` and description
             error text will be returned. Example reasons for rejection include:
 
@@ -99,12 +99,18 @@ paths:
                 $ref: definitions/errors/error.yaml
         "403":
           description: |-
-            You do not have permission to invite the user to the room. A meaningful `errcode` and description error text will be returned. Example reasons for rejections are:
+            You do not have permission to invite the user to the room. A
+            meaningful `errcode` and description error text will be returned.
+            Example reasons for rejections are:
 
             - The invitee has been banned from the room.
             - The invitee is already a member of the room.
             - The inviter is not currently in the room.
             - The inviter's power level is insufficient to invite users to the room.
+
+            {{% added-in v="1.18"%}} The `M_INVITE_BLOCKED` error code is used to
+            indicate that the homeserver rejected the invite due to
+            [invite blocking](/client-server-api/#invite-permission).
           content:
             application/json:
               schema:

data/api/client-server/room_state.yaml

@@ -116,7 +116,13 @@ paths:
                     "error": "The alias '#hello:example.org' does not point to this room."
                   }
         "403":
-          description: The sender doesn't have permission to send the event into the room.
+          description: |-
+            The sender doesn't have permission to send the event into the room.
+
+            {{% added-in v="1.18"%}} If the `eventType` is `m.room.member` and
+            the `membership` is `invite`, the `M_INVITE_BLOCKED` error code is
+            used to indicate that the homeserver rejected the invite due to
+            [invite blocking](/client-server-api/#invite-permission).
           content:
             application/json:
               schema:

data/api/client-server/third_party_membership.yaml

@@ -97,6 +97,10 @@ paths:
             - The invitee is already a member of the room.
             - The inviter is not currently in the room.
             - The inviter's power level is insufficient to invite users to the room.
+
+            {{% added-in v="1.18"%}} The `M_INVITE_BLOCKED` error code is used to
+            indicate that the homeserver rejected the invite due to
+            [invite blocking](/client-server-api/#invite-permission).
           content:
             application/json:
               schema:

data/api/server-server/invites-v1.yaml

@@ -155,11 +155,17 @@ paths:
                   ]
         "403":
           description: |-
-            The invite is not allowed. This could be for a number of reasons, including:
+            The invite is not allowed.
+
+            The `M_FORBIDDEN` error code is used to indicate one of the following:
 
             * The sender is not allowed to send invites to the target user/homeserver.
             * The homeserver does not permit anyone to invite its users.
             * The homeserver refuses to participate in the room.
+
+            {{% added-in v="1.18"%}} The `M_INVITE_BLOCKED` error code is used to
+            indicate that the homeserver rejected the invite due to
+            [invite blocking](/client-server-api/#invite-permission).
           content:
             application/json:
               schema:

data/api/server-server/invites-v2.yaml

@@ -192,11 +192,17 @@ paths:
                   }
         "403":
           description: |-
-            The invite is not allowed. This could be for a number of reasons, including:
+            The invite is not allowed.
+
+            The `M_FORBIDDEN` error code is used to indicate one of the following:
 
             * The sender is not allowed to send invites to the target user/homeserver.
             * The homeserver does not permit anyone to invite its users.
             * The homeserver refuses to participate in the room.
+
+            {{% added-in v="1.18"%}} The `M_INVITE_BLOCKED` error code is used to
+            indicate that the homeserver rejected the invite due to
+            [invite blocking](/client-server-api/#invite-permission).
           content:
             application/json:
               schema:

data/event-schemas/examples/m.invite_permission_config.yaml

@@ -0,0 +1,7 @@
+{
+  "$ref": "core/event.json",
+  "type": "m.invite_permission_config",
+  "content": {
+    "default_action": "block"
+  }
+}

data/event-schemas/schema/m.invite_permission_config.yaml

@@ -0,0 +1,21 @@
+---
+$schema: https://json-schema.org/draft/2020-12/schema
+allOf:
+  - $ref: core-event-schema/event.yaml
+  - title: Invite Permission
+    type: object
+    description: |-
+      The permission configuration for receiving invites for the current account.
+    properties:
+      content:
+        type: object
+        properties:
+          default_action:
+            type: string
+            description: |-
+              When set to `block`, the user does not wish to receive *any* room invites, and they
+              should be rejected automatically by the homeserver.
+
+              A missing, invalid or unsupported value means that the user wants to receive invites
+              as normal. Other parts of the specification might still have effects on invites, like
+              [ignoring users](/client-server-api/#ignoring-users).