Merge aa9a203be0 into a6da9443da

changelogs/server_server/newsfragments/2284.clarification

@@ -1 +1 @@
-Specified input validation for PDUs passed to federation membership endpoints.
+Specified input validation for PDUs passed to and returned from federation membership endpoints.

content/server-server-api.md

@@ -868,8 +868,10 @@ selecting a resident from the candidate list, and using the
 enough information for the joining server to fill in the event.
 
 The joining server is expected to add or replace the `origin`,
-`origin_server_ts`, and `event_id` on the templated event received by
-the resident server. This event is then signed by the joining server.
+`origin_server_ts`, and `event_id` on the templated event received by the
+resident server. The joining server MUST also verify that the `type`, `room_id`,
+`sender`, `state_key` and `content.membership` fields have the expected values.
+This event is then signed by the joining server.
 
 To complete the join handshake, the joining server submits this new event
 to the resident server it used for `GET /make_join`, using the `PUT /send_join`

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

@@ -36,6 +36,30 @@ paths:
         Also note that if the remote homeserver is already in the room, it will receive the
         invite event twice; once through this endpoint, and again through a [federation
         transaction](/server-server-api/#transactions).
+
+        Servers MUST apply certain validation to ensure they don't accidentally sign non-invite
+        events from a malicious server. The `M_MISSING_PARAM` error code is used to indicate one
+        or more of the following:
+
+        * The invite event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
+        * The event type is not `m.room.member`.
+        * The `membership` field inside the event content is not `invite`.
+        * The event sender is not a user ID on the origin server.
+        * The `state_key` is not a user ID on the receiving server.
+
+        The `M_MISSING_PARAM` error code is also used to indicate one or more of the following
+        problems in the `invite_room_state` field:
+
+        * The `m.room.create` event is missing from `invite_room_state`.
+        * One or more entries in `invite_room_state` are not formatted according
+          to the room's version.
+        * One or more events fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
+        * One or more events does not reside in the same room as the invite.
+          Note: Some room versions may require calculating the room ID for an
+          event rather than relying on the presence of `room_id`.
+
+        Servers MAY apply the `invite_room_state` validation to room versions 1 through 11,
+        and SHOULD apply the validation to all other room versions.
       operationId: sendInviteV1
       security:
         - signedRequest: []
@@ -178,34 +202,7 @@ paths:
                   }
         "400":
           description: |-
-            The `M_INVALID_PARAM` error code is used to indicate one or more of the following:
-
-            * The invite event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
-            * The event type is not `m.room.member`.
-            * The `membership` field inside the event content is not `invite`.
-            * The event sender is not a user ID on the origin server.
-            * The `state_key` is not a user ID on the receiving server.
-
-            Servers MUST apply the validation above to the invite event before
-            signing it regardless of room version.
-
-            The `M_MISSING_PARAM` error code is used to indicate one or more of
-            the following:
-
-            * The `m.room.create` event is missing from `invite_room_state`.
-            * One or more entries in `invite_room_state` are not formatted according
-              to the room's version.
-            * One or more events fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
-            * One or more events does not reside in the same room as the invite.
-              Note: Some room versions may require calculating the room ID for an
-              event rather than relying on the presence of `room_id`.
-
-            Servers MAY apply the validation above to room versions 1 through 11,
-            and SHOULD apply the validation above to all other room versions.
-
-            If `M_MISSING_PARAM` or `M_INVALID_PARAM` is returned and the request
-            is associated with a Client-Server API request, the Client-Server API
-            request SHOULD fail with a 5xx error rather than being passed through.
+            The request is invalid in some way.
           content:
             application/json:
               schema:

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

@@ -40,6 +40,30 @@ paths:
         Also note that if the remote homeserver is already in the room, it will receive the
         invite event twice; once through this endpoint, and again through a [federation
         transaction](/server-server-api/#transactions).
+
+        Servers MUST apply certain validation to ensure they don't accidentally sign non-invite
+        events from a malicious server. The `M_MISSING_PARAM` error code is used to indicate one
+        or more of the following:
+
+        * The invite event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
+        * The event type is not `m.room.member`.
+        * The `membership` field inside the event content is not `invite`.
+        * The event sender is not a user ID on the origin server.
+        * The `state_key` is not a user ID on the receiving server.
+
+        The `M_MISSING_PARAM` error code is also used to indicate one or more of the following
+        problems in the `invite_room_state` field:
+
+        * The `m.room.create` event is missing from `invite_room_state`.
+        * One or more entries in `invite_room_state` are not formatted according
+          to the room's version.
+        * One or more events fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
+        * One or more events does not reside in the same room as the invite.
+          Note: Some room versions may require calculating the room ID for an
+          event rather than relying on the presence of `room_id`.
+
+        Servers MAY apply the `invite_room_state` validation to room versions 1 through 11,
+        and SHOULD apply the validation to all other room versions.
       operationId: sendInviteV2
       security:
         - signedRequest: []
@@ -154,34 +178,9 @@ paths:
             The error should be passed through to clients so that they
             may give better feedback to users.
 
-            The `M_INVALID_PARAM` error code is used to indicate one or more of the following:
-
-            * The invite event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
-            * The event type is not `m.room.member`.
-            * The `membership` field inside the event content is not `invite`.
-            * The event sender is not a user ID on the origin server.
-            * The `state_key` is not a user ID on the receiving server.
-
-            Servers MUST apply the validation above to the invite event before
-            signing it regardless of room version.
-
-            The `M_MISSING_PARAM` error code is used to indicate one or more of
-            the following:
-
-            * The `m.room.create` event is missing from `invite_room_state`.
-            * One or more entries in `invite_room_state` are not formatted according
-              to the room's version.
-            * One or more events fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
-            * One or more events does not reside in the same room as the invite.
-              Note: Some room versions may require calculating the room ID for an
-              event rather than relying on the presence of `room_id`.
-
-            Servers MAY apply the validation above to room versions 1 through 11,
-            and SHOULD apply the validation above to all other room versions.
-
-            If `M_MISSING_PARAM` or `M_INVALID_PARAM` is returned and the request
-            is associated with a Client-Server API request, the Client-Server API
-            request SHOULD fail with a 5xx error rather than being passed through.
+            If `M_MISSING_PARAM` is returned and the request is associated with a
+            Client-Server API request, the Client-Server API request SHOULD fail
+            with a 5xx error rather than being passed through.
           content:
             application/json:
               schema:

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

@@ -23,6 +23,17 @@ paths:
       description: |-
         Asks the receiving server to return information that the sending
         server will need to prepare a join event to get into the room.
+
+        Before signing the returned template and calling `/send_join`,
+        the sending server MUST verify that:
+
+        * the `room_id` is equal to the `roomId` path parameter.
+        * both the `sender` and `state_key` are equal to the `userId` path parameter.
+        * the `type` of the event is `m.room.member`.
+        * the `membership` field inside `content` is `join`.
+
+        In case any of the above checks fail, the response MUST be treated as malformed and
+        discarded. The caller MAY try to join through another server.
       operationId: makeJoin
       security:
         - signedRequest: []
@@ -238,6 +249,15 @@ paths:
         **The request and response body here describe the common
         event fields in more detail and may be missing other required
         fields for a PDU.**
+
+        The receiving server MUST apply certain validation before accepting the event.
+        The `M_INVALID_PARAM` error code is used to indicate one or more of the following:
+
+        * The join event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
+        * The event type is not `m.room.member`.
+        * The `membership` field inside the event content is not `join`.
+        * The event sender is not a user ID on the origin server.
+        * The `state_key` is not equal to the `sender`.
       operationId: sendJoinV1
       security:
         - signedRequest: []
@@ -391,16 +411,6 @@ paths:
         "400":
           description: |-
             The request is invalid in some way.
-
-            The `M_INVALID_PARAM` error code is used to indicate one or more of the following:
-
-            * The join event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
-            * The event type is not `m.room.member`.
-            * The `membership` field inside the event content is not `join`.
-            * The event sender is not a user ID on the origin server.
-            * The `state_key` is not equal to the `sender`.
-
-            Servers MUST apply the validation above to the join event.
           content:
             application/json:
               schema:

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

@@ -38,6 +38,15 @@ paths:
         **The request and response body here describe the common
         event fields in more detail and may be missing other required
         fields for a PDU.**
+
+        The receiving server MUST apply certain validation before accepting the event.
+        The `M_INVALID_PARAM` error code is used to indicate one or more of the following:
+
+        * The join event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
+        * The event type is not `m.room.member`.
+        * The `membership` field inside the event content is not `join`.
+        * The event sender is not a user ID on the origin server.
+        * The `state_key` is not equal to the `sender`.
       operationId: sendJoinV2
       security:
         - signedRequest: []
@@ -247,15 +256,9 @@ paths:
             The error should be passed through to clients so that they
             may give better feedback to users.
 
-            The `M_INVALID_PARAM` error code is used to indicate one or more of the following:
-
-            * The join event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
-            * The event type is not `m.room.member`.
-            * The `membership` field inside the event content is not `join`.
-            * The event sender is not a user ID on the origin server.
-            * The `state_key` is not equal to the `sender`.
-
-            Servers MUST apply the validation above to the join event.
+            If `M_MISSING_PARAM` is returned and the request is associated with a
+            Client-Server API request, the Client-Server API request SHOULD fail
+            with a 5xx error rather than being passed through.
 
             New in `v1.2`, the following error conditions might happen:
 

data/api/server-server/knocks.yaml

@@ -23,6 +23,17 @@ paths:
       description: |-
         Asks the receiving server to return information that the sending
         server will need to prepare a knock event for the room.
+
+        Before signing the returned template and calling `/send_knock`,
+        the sending server MUST verify that:
+
+        * the `room_id` is equal to the `roomId` path parameter.
+        * both the `sender` and `state_key` are equal to the `userId` path parameter.
+        * the `type` of the event is `m.room.member`.
+        * the `membership` field inside `content` is `knock`.
+
+        In case any of the above checks fail, the response MUST be treated as malformed and
+        discarded. The caller MAY try to knock through another server.
       operationId: makeKnock
       security:
         - signedRequest: []
@@ -204,6 +215,15 @@ paths:
         **The request and response body here describe the common
         event fields in more detail and may be missing other required
         fields for a PDU.**
+
+        The receiving server MUST apply certain validation before accepting the event.
+        The `M_INVALID_PARAM` error code is used to indicate one or more of the following:
+
+        * The knock event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
+        * The event type is not `m.room.member`.
+        * The `membership` field inside the event content is not `knock`.
+        * The event sender is not a user ID on the origin server.
+        * The `state_key` is not equal to the `sender`.
       operationId: sendKnock
       security:
         - signedRequest: []
@@ -332,15 +352,7 @@ paths:
                   }
         "400":
           description: |-
-            The `M_INVALID_PARAM` error code is used to indicate one or more of the following:
-
-            * The knock event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
-            * The event type is not `m.room.member`.
-            * The `membership` field inside the event content is not `knock`.
-            * The event sender is not a user ID on the origin server.
-            * The `state_key` is not equal to the `sender`.
-
-            Servers MUST apply the validation above to the knock event.
+            The request is invalid in some way.
           content:
             application/json:
               schema:

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

@@ -23,6 +23,17 @@ paths:
       description: |-
         Asks the receiving server to return information that the sending
         server will need to prepare a leave event to get out of the room.
+
+        Before signing the returned template and calling `/send_leave`,
+        the sending server MUST verify that:
+
+        * the `room_id` is equal to the `roomId` path parameter.
+        * both the `sender` and `state_key` are equal to the `userId` path parameter.
+        * the `type` of the event is `m.room.member`.
+        * the `membership` field inside `content` is `leave`.
+
+        In case any of the above checks fail, the response MUST be treated as malformed and
+        discarded. The caller MAY try to leave through another server.
       operationId: makeLeave
       security:
         - signedRequest: []
@@ -153,6 +164,15 @@ paths:
         **The request and response body here describe the common
         event fields in more detail and may be missing other required
         fields for a PDU.**
+
+        The receiving server MUST apply certain validation before accepting the event.
+        The `M_INVALID_PARAM` error code is used to indicate one or more of the following:
+
+        * The leave event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
+        * The event type is not `m.room.member`.
+        * The `membership` field inside the event content is not `leave`.
+        * The event sender is not a user ID on the origin server.
+        * The `state_key` is not equal to the `sender`.
       operationId: sendLeaveV1
       security:
         - signedRequest: []
@@ -251,15 +271,7 @@ paths:
                   ]
         "400":
           description: |-
-            The `M_INVALID_PARAM` error code is used to indicate one or more of the following:
-
-            * The leave event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
-            * The event type is not `m.room.member`.
-            * The `membership` field inside the event content is not `leave`.
-            * The event sender is not a user ID on the origin server.
-            * The `state_key` is not equal to the `sender`.
-
-            Servers MUST apply the validation above to the leave event.
+            The request is invalid in some way.
           content:
             application/json:
               schema:

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

@@ -38,6 +38,15 @@ paths:
         **The request and response body here describe the common
         event fields in more detail and may be missing other required
         fields for a PDU.**
+
+        The receiving server MUST apply certain validation before accepting the event.
+        The `M_INVALID_PARAM` error code is used to indicate one or more of the following:
+
+        * The leave event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
+        * The event type is not `m.room.member`.
+        * The `membership` field inside the event content is not `leave`.
+        * The event sender is not a user ID on the origin server.
+        * The `state_key` is not equal to the `sender`.
       operationId: sendLeaveV2
       security:
         - signedRequest: []
@@ -136,15 +145,7 @@ paths:
                   value: {}
         "400":
           description: |-
-            The `M_INVALID_PARAM` error code is used to indicate one or more of the following:
-
-            * The leave event fails a [signature check](/server-server-api/#validating-hashes-and-signatures-on-received-events).
-            * The event type is not `m.room.member`.
-            * The `membership` field inside the event content is not `leave`.
-            * The event sender is not a user ID on the origin server.
-            * The `state_key` is not equal to the `sender`.
-
-            Servers MUST apply the validation above to the leave event.
+            The request is invalid in some way.
           content:
             application/json:
               schema: