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// Copyright 2017-2024 New Vector Ltd.
//
// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
// Please see LICENSE files in the repository root for full details.
package routing
import (
"context"
"encoding/json"
"net/http"
"time"
"github.com/element-hq/dendrite/roomserver/api"
"github.com/matrix-org/gomatrixserverlib"
"github.com/matrix-org/gomatrixserverlib/fclient"
"github.com/matrix-org/gomatrixserverlib/spec"
"github.com/matrix-org/util"
)
// GetEvent returns the requested event
func GetEvent(
ctx context.Context,
request *fclient.FederationRequest,
rsAPI api.FederationRoomserverAPI,
eventID string,
origin spec.ServerName,
) util.JSONResponse {
// /_matrix/federation/v1/event/{eventId} doesn't have a roomID, we use an empty string,
// which results in `QueryEventsByID` to first get the event and use that to determine the roomID.
event, err := fetchEvent(ctx, rsAPI, "", eventID)
if err != nil {
return *err
}
err = allowedToSeeEvent(ctx, request.Origin(), rsAPI, eventID, event.RoomID().String())
if err != nil {
return *err
}
return util.JSONResponse{Code: http.StatusOK, JSON: gomatrixserverlib.Transaction{
Origin: origin,
OriginServerTS: spec.AsTimestamp(time.Now()),
PDUs: []json.RawMessage{
event.JSON(),
},
}}
}
// allowedToSeeEvent returns no error if the server is allowed to see this event,
// otherwise it returns an error response which can be sent to the client.
func allowedToSeeEvent(
ctx context.Context,
origin spec.ServerName,
rsAPI api.FederationRoomserverAPI,
eventID string,
roomID string,
) *util.JSONResponse {
allowed, err := rsAPI.QueryServerAllowedToSeeEvent(ctx, origin, eventID, roomID)
if err != nil {
resErr := util.ErrorResponse(err)
return &resErr
}
if !allowed {
resErr := util.MessageResponse(http.StatusForbidden, "server not allowed to see event")
return &resErr
}
return nil
}
// fetchEvent fetches the event without auth checks. Returns an error if the event cannot be found.
func fetchEvent(ctx context.Context, rsAPI api.FederationRoomserverAPI, roomID, eventID string) (gomatrixserverlib.PDU, *util.JSONResponse) {
var eventsResponse api.QueryEventsByIDResponse
err := rsAPI.QueryEventsByID(
ctx,
&api.QueryEventsByIDRequest{EventIDs: []string{eventID}, RoomID: roomID},
&eventsResponse,
)
if err != nil {
resErr := util.ErrorResponse(err)
return nil, &resErr
}
if len(eventsResponse.Events) == 0 {
return nil, &util.JSONResponse{
Code: http.StatusNotFound,
JSON: spec.NotFound("Event not found"),
}
}
return eventsResponse.Events[0].PDU, nil
}
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