dendrite/federationapi/routing/send.go
2020-09-29 14:07:59 +01:00

970 lines
36 KiB
Go

// Copyright 2017 Vector Creations Ltd
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package routing
import (
"context"
"encoding/json"
"fmt"
"net/http"
"sync"
"time"
"github.com/matrix-org/dendrite/clientapi/jsonerror"
eduserverAPI "github.com/matrix-org/dendrite/eduserver/api"
"github.com/matrix-org/dendrite/internal/config"
keyapi "github.com/matrix-org/dendrite/keyserver/api"
"github.com/matrix-org/dendrite/roomserver/api"
"github.com/matrix-org/gomatrixserverlib"
"github.com/matrix-org/util"
"github.com/sirupsen/logrus"
)
// Send implements /_matrix/federation/v1/send/{txnID}
func Send(
httpReq *http.Request,
request *gomatrixserverlib.FederationRequest,
txnID gomatrixserverlib.TransactionID,
cfg *config.FederationAPI,
rsAPI api.RoomserverInternalAPI,
eduAPI eduserverAPI.EDUServerInputAPI,
keyAPI keyapi.KeyInternalAPI,
keys gomatrixserverlib.JSONVerifier,
federation *gomatrixserverlib.FederationClient,
) util.JSONResponse {
t := txnReq{
rsAPI: rsAPI,
eduAPI: eduAPI,
keys: keys,
federation: federation,
haveEvents: make(map[string]*gomatrixserverlib.HeaderedEvent),
newEvents: make(map[string]bool),
keyAPI: keyAPI,
}
var txnEvents struct {
PDUs []json.RawMessage `json:"pdus"`
EDUs []gomatrixserverlib.EDU `json:"edus"`
}
if err := json.Unmarshal(request.Content(), &txnEvents); err != nil {
return util.JSONResponse{
Code: http.StatusBadRequest,
JSON: jsonerror.NotJSON("The request body could not be decoded into valid JSON. " + err.Error()),
}
}
// Transactions are limited in size; they can have at most 50 PDUs and 100 EDUs.
// https://matrix.org/docs/spec/server_server/latest#transactions
if len(txnEvents.PDUs) > 50 || len(txnEvents.EDUs) > 100 {
return util.JSONResponse{
Code: http.StatusBadRequest,
JSON: jsonerror.BadJSON("max 50 pdus / 100 edus"),
}
}
// TODO: Really we should have a function to convert FederationRequest to txnReq
t.PDUs = txnEvents.PDUs
t.EDUs = txnEvents.EDUs
t.Origin = request.Origin()
t.TransactionID = txnID
t.Destination = cfg.Matrix.ServerName
util.GetLogger(httpReq.Context()).Infof("Received transaction %q containing %d PDUs, %d EDUs", txnID, len(t.PDUs), len(t.EDUs))
resp, jsonErr := t.processTransaction(httpReq.Context())
if jsonErr != nil {
util.GetLogger(httpReq.Context()).WithField("jsonErr", jsonErr).Error("t.processTransaction failed")
return *jsonErr
}
// https://matrix.org/docs/spec/server_server/r0.1.3#put-matrix-federation-v1-send-txnid
// Status code 200:
// The result of processing the transaction. The server is to use this response
// even in the event of one or more PDUs failing to be processed.
return util.JSONResponse{
Code: http.StatusOK,
JSON: resp,
}
}
type txnReq struct {
gomatrixserverlib.Transaction
rsAPI api.RoomserverInternalAPI
eduAPI eduserverAPI.EDUServerInputAPI
keyAPI keyapi.KeyInternalAPI
keys gomatrixserverlib.JSONVerifier
federation txnFederationClient
// local cache of events for auth checks, etc - this may include events
// which the roomserver is unaware of.
haveEvents map[string]*gomatrixserverlib.HeaderedEvent
// new events which the roomserver does not know about
newEvents map[string]bool
}
// A subset of FederationClient functionality that txn requires. Useful for testing.
type txnFederationClient interface {
LookupState(ctx context.Context, s gomatrixserverlib.ServerName, roomID string, eventID string, roomVersion gomatrixserverlib.RoomVersion) (
res gomatrixserverlib.RespState, err error,
)
LookupStateIDs(ctx context.Context, s gomatrixserverlib.ServerName, roomID string, eventID string) (res gomatrixserverlib.RespStateIDs, err error)
GetEvent(ctx context.Context, s gomatrixserverlib.ServerName, eventID string) (res gomatrixserverlib.Transaction, err error)
LookupMissingEvents(ctx context.Context, s gomatrixserverlib.ServerName, roomID string, missing gomatrixserverlib.MissingEvents,
roomVersion gomatrixserverlib.RoomVersion) (res gomatrixserverlib.RespMissingEvents, err error)
}
func (t *txnReq) processTransaction(ctx context.Context) (*gomatrixserverlib.RespSend, *util.JSONResponse) {
results := make(map[string]gomatrixserverlib.PDUResult)
pdus := []gomatrixserverlib.HeaderedEvent{}
for _, pdu := range t.PDUs {
var header struct {
RoomID string `json:"room_id"`
}
if err := json.Unmarshal(pdu, &header); err != nil {
util.GetLogger(ctx).WithError(err).Warn("Transaction: Failed to extract room ID from event")
// We don't know the event ID at this point so we can't return the
// failure in the PDU results
continue
}
verReq := api.QueryRoomVersionForRoomRequest{RoomID: header.RoomID}
verRes := api.QueryRoomVersionForRoomResponse{}
if err := t.rsAPI.QueryRoomVersionForRoom(ctx, &verReq, &verRes); err != nil {
util.GetLogger(ctx).WithError(err).Warn("Transaction: Failed to query room version for room", verReq.RoomID)
// We don't know the event ID at this point so we can't return the
// failure in the PDU results
continue
}
event, err := gomatrixserverlib.NewEventFromUntrustedJSON(pdu, verRes.RoomVersion)
if err != nil {
if _, ok := err.(gomatrixserverlib.BadJSONError); ok {
// Room version 6 states that homeservers should strictly enforce canonical JSON
// on PDUs.
//
// This enforces that the entire transaction is rejected if a single bad PDU is
// sent. It is unclear if this is the correct behaviour or not.
//
// See https://github.com/matrix-org/synapse/issues/7543
return nil, &util.JSONResponse{
Code: 400,
JSON: jsonerror.BadJSON("PDU contains bad JSON"),
}
}
util.GetLogger(ctx).WithError(err).Warnf("Transaction: Failed to parse event JSON of event %s", string(pdu))
continue
}
if api.IsServerBannedFromRoom(ctx, t.rsAPI, event.RoomID(), t.Origin) {
results[event.EventID()] = gomatrixserverlib.PDUResult{
Error: "Forbidden by server ACLs",
}
continue
}
if err = gomatrixserverlib.VerifyAllEventSignatures(ctx, []gomatrixserverlib.Event{event}, t.keys); err != nil {
util.GetLogger(ctx).WithError(err).Warnf("Transaction: Couldn't validate signature of event %q", event.EventID())
results[event.EventID()] = gomatrixserverlib.PDUResult{
Error: err.Error(),
}
continue
}
pdus = append(pdus, event.Headered(verRes.RoomVersion))
}
// Process the events.
for _, e := range pdus {
if err := t.processEvent(ctx, e.Unwrap(), true); err != nil {
// If the error is due to the event itself being bad then we skip
// it and move onto the next event. We report an error so that the
// sender knows that we have skipped processing it.
//
// However if the event is due to a temporary failure in our server
// such as a database being unavailable then we should bail, and
// hope that the sender will retry when we are feeling better.
//
// It is uncertain what we should do if an event fails because
// we failed to fetch more information from the sending server.
// For example if a request to /state fails.
// If we skip the event then we risk missing the event until we
// receive another event referencing it.
// If we bail and stop processing then we risk wedging incoming
// transactions from that server forever.
if isProcessingErrorFatal(err) {
// Any other error should be the result of a temporary error in
// our server so we should bail processing the transaction entirely.
util.GetLogger(ctx).Warnf("Processing %s failed fatally: %s", e.EventID(), err)
jsonErr := util.ErrorResponse(err)
return nil, &jsonErr
} else {
// Auth errors mean the event is 'rejected' which have to be silent to appease sytest
errMsg := ""
_, rejected := err.(*gomatrixserverlib.NotAllowed)
if !rejected {
errMsg = err.Error()
}
util.GetLogger(ctx).WithError(err).WithField("event_id", e.EventID()).WithField("rejected", rejected).Warn(
"Failed to process incoming federation event, skipping",
)
results[e.EventID()] = gomatrixserverlib.PDUResult{
Error: errMsg,
}
}
} else {
results[e.EventID()] = gomatrixserverlib.PDUResult{}
}
}
t.processEDUs(ctx)
if c := len(results); c > 0 {
util.GetLogger(ctx).Infof("Processed %d PDUs from transaction %q", c, t.TransactionID)
}
return &gomatrixserverlib.RespSend{PDUs: results}, nil
}
// isProcessingErrorFatal returns true if the error is really bad and
// we should stop processing the transaction, and returns false if it
// is just some less serious error about a specific event.
func isProcessingErrorFatal(err error) bool {
switch err.(type) {
case roomNotFoundError:
case *gomatrixserverlib.NotAllowed:
case missingPrevEventsError:
default:
switch err {
case context.Canceled:
case context.DeadlineExceeded:
default:
return true
}
}
return false
}
type roomNotFoundError struct {
roomID string
}
type unmarshalError struct {
err error
}
type verifySigError struct {
eventID string
err error
}
type missingPrevEventsError struct {
eventID string
err error
}
func (e roomNotFoundError) Error() string { return fmt.Sprintf("room %q not found", e.roomID) }
func (e unmarshalError) Error() string { return fmt.Sprintf("unable to parse event: %s", e.err) }
func (e verifySigError) Error() string {
return fmt.Sprintf("unable to verify signature of event %q: %s", e.eventID, e.err)
}
func (e missingPrevEventsError) Error() string {
return fmt.Sprintf("unable to get prev_events for event %q: %s", e.eventID, e.err)
}
func (t *txnReq) haveEventIDs() map[string]bool {
result := make(map[string]bool, len(t.haveEvents))
for eventID := range t.haveEvents {
if t.newEvents[eventID] {
continue
}
result[eventID] = true
}
return result
}
// nolint:gocyclo
func (t *txnReq) processEDUs(ctx context.Context) {
for _, e := range t.EDUs {
switch e.Type {
case gomatrixserverlib.MTyping:
// https://matrix.org/docs/spec/server_server/latest#typing-notifications
var typingPayload struct {
RoomID string `json:"room_id"`
UserID string `json:"user_id"`
Typing bool `json:"typing"`
}
if err := json.Unmarshal(e.Content, &typingPayload); err != nil {
util.GetLogger(ctx).WithError(err).Error("Failed to unmarshal typing event")
continue
}
if err := eduserverAPI.SendTyping(ctx, t.eduAPI, typingPayload.UserID, typingPayload.RoomID, typingPayload.Typing, 30*1000); err != nil {
util.GetLogger(ctx).WithError(err).Error("Failed to send typing event to edu server")
}
case gomatrixserverlib.MDirectToDevice:
// https://matrix.org/docs/spec/server_server/r0.1.3#m-direct-to-device-schema
var directPayload gomatrixserverlib.ToDeviceMessage
if err := json.Unmarshal(e.Content, &directPayload); err != nil {
util.GetLogger(ctx).WithError(err).Error("Failed to unmarshal send-to-device events")
continue
}
for userID, byUser := range directPayload.Messages {
for deviceID, message := range byUser {
// TODO: check that the user and the device actually exist here
if err := eduserverAPI.SendToDevice(ctx, t.eduAPI, directPayload.Sender, userID, deviceID, directPayload.Type, message); err != nil {
util.GetLogger(ctx).WithError(err).WithFields(logrus.Fields{
"sender": directPayload.Sender,
"user_id": userID,
"device_id": deviceID,
}).Error("Failed to send send-to-device event to edu server")
}
}
}
case gomatrixserverlib.MDeviceListUpdate:
t.processDeviceListUpdate(ctx, e)
default:
util.GetLogger(ctx).WithField("type", e.Type).Debug("Unhandled EDU")
}
}
}
func (t *txnReq) processDeviceListUpdate(ctx context.Context, e gomatrixserverlib.EDU) {
var payload gomatrixserverlib.DeviceListUpdateEvent
if err := json.Unmarshal(e.Content, &payload); err != nil {
util.GetLogger(ctx).WithError(err).Error("Failed to unmarshal device list update event")
return
}
var inputRes keyapi.InputDeviceListUpdateResponse
t.keyAPI.InputDeviceListUpdate(context.Background(), &keyapi.InputDeviceListUpdateRequest{
Event: payload,
}, &inputRes)
if inputRes.Error != nil {
util.GetLogger(ctx).WithError(inputRes.Error).WithField("user_id", payload.UserID).Error("failed to InputDeviceListUpdate")
}
}
func (t *txnReq) processEvent(ctx context.Context, e gomatrixserverlib.Event, isInboundTxn bool) error {
logger := util.GetLogger(ctx).WithField("event_id", e.EventID()).WithField("room_id", e.RoomID())
// Work out if the roomserver knows everything it needs to know to auth
// the event.
stateReq := api.QueryMissingAuthPrevEventsRequest{
RoomID: e.RoomID(),
AuthEventIDs: e.AuthEventIDs(),
PrevEventIDs: e.PrevEventIDs(),
}
var stateResp api.QueryMissingAuthPrevEventsResponse
if err := t.rsAPI.QueryMissingAuthPrevEvents(ctx, &stateReq, &stateResp); err != nil {
return err
}
if !stateResp.RoomExists {
// TODO: When synapse receives a message for a room it is not in it
// asks the remote server for the state of the room so that it can
// check if the remote server knows of a join "m.room.member" event
// that this server is unaware of.
// However generally speaking we should reject events for rooms we
// aren't a member of.
return roomNotFoundError{e.RoomID()}
}
if len(stateResp.MissingAuthEventIDs) > 0 {
logger.Infof("Event refers to %d unknown auth_events", len(stateResp.MissingAuthEventIDs))
servers := []gomatrixserverlib.ServerName{t.Origin}
serverReq := &api.QueryServerJoinedToRoomRequest{
RoomID: e.RoomID(),
}
serverRes := &api.QueryServerJoinedToRoomResponse{}
if err := t.rsAPI.QueryServerJoinedToRoom(ctx, serverReq, serverRes); err == nil {
servers = append(servers, serverRes.ServerNames...)
logger.Infof("Found %d server(s) to query for missing events", len(servers))
}
getAuthEvent:
for _, missingAuthEventID := range stateResp.MissingAuthEventIDs {
for _, server := range servers {
logger.Infof("Retrieving missing auth event %q from %q", missingAuthEventID, server)
tx, err := t.federation.GetEvent(ctx, server, missingAuthEventID)
if err != nil {
continue // try the next server
}
ev, err := gomatrixserverlib.NewEventFromUntrustedJSON(tx.PDUs[0], stateResp.RoomVersion)
if err != nil {
logger.WithError(err).Errorf("Failed to unmarshal auth event %q", missingAuthEventID)
continue // try the next server
}
if err = api.SendInputRoomEvents(
context.Background(),
t.rsAPI,
[]api.InputRoomEvent{
{
Kind: api.KindOutlier,
Event: ev.Headered(stateResp.RoomVersion),
AuthEventIDs: ev.AuthEventIDs(),
SendAsServer: api.DoNotSendToOtherServers,
},
},
); err != nil {
logger.WithError(err).Errorf("Failed to send auth event %q to roomserver", missingAuthEventID)
continue getAuthEvent // move onto the next event
}
}
}
}
if len(stateResp.MissingPrevEventIDs) > 0 {
logger.Infof("Event refers to %d unknown prev_events", len(stateResp.MissingPrevEventIDs))
return t.processEventWithMissingState(ctx, e, stateResp.RoomVersion, isInboundTxn)
}
// pass the event to the roomserver which will do auth checks
// If the event fail auth checks, gmsl.NotAllowed error will be returned which we be silently
// discarded by the caller of this function
return api.SendEvents(
context.Background(),
t.rsAPI,
[]gomatrixserverlib.HeaderedEvent{
e.Headered(stateResp.RoomVersion),
},
api.DoNotSendToOtherServers,
nil,
)
}
func checkAllowedByState(e gomatrixserverlib.Event, stateEvents []gomatrixserverlib.Event) error {
authUsingState := gomatrixserverlib.NewAuthEvents(nil)
for i := range stateEvents {
err := authUsingState.AddEvent(&stateEvents[i])
if err != nil {
return err
}
}
return gomatrixserverlib.Allowed(e, &authUsingState)
}
func (t *txnReq) processEventWithMissingState(ctx context.Context, e gomatrixserverlib.Event, roomVersion gomatrixserverlib.RoomVersion, isInboundTxn bool) error {
// Do this with a fresh context, so that we keep working even if the
// original request times out. With any luck, by the time the remote
// side retries, we'll have fetched the missing state.
gmectx, cancel := context.WithTimeout(context.Background(), time.Minute*5)
defer cancel()
// We are missing the previous events for this events.
// This means that there is a gap in our view of the history of the
// room. There two ways that we can handle such a gap:
// 1) We can fill in the gap using /get_missing_events
// 2) We can leave the gap and request the state of the room at
// this event from the remote server using either /state_ids
// or /state.
// Synapse will attempt to do 1 and if that fails or if the gap is
// too large then it will attempt 2.
// Synapse will use /state_ids if possible since usually the state
// is largely unchanged and it is more efficient to fetch a list of
// event ids and then use /event to fetch the individual events.
// However not all version of synapse support /state_ids so you may
// need to fallback to /state.
// Attempt to fill in the gap using /get_missing_events
// This will either:
// - fill in the gap completely then process event `e` returning no backwards extremity
// - fail to fill in the gap and tell us to terminate the transaction err=not nil
// - fail to fill in the gap and tell us to fetch state at the new backwards extremity, and to not terminate the transaction
backwardsExtremity, err := t.getMissingEvents(gmectx, e, roomVersion, isInboundTxn)
if err != nil {
return err
}
if backwardsExtremity == nil {
// we filled in the gap!
return nil
}
// at this point we know we're going to have a gap: we need to work out the room state at the new backwards extremity.
// security: we have to do state resolution on the new backwards extremity (TODO: WHY)
// Therefore, we cannot just query /state_ids with this event to get the state before. Instead, we need to query
// the state AFTER all the prev_events for this event, then apply state resolution to that to get the state before the event.
var states []*gomatrixserverlib.RespState
needed := gomatrixserverlib.StateNeededForAuth([]gomatrixserverlib.Event{*backwardsExtremity}).Tuples()
for _, prevEventID := range backwardsExtremity.PrevEventIDs() {
var prevState *gomatrixserverlib.RespState
prevState, err = t.lookupStateAfterEvent(gmectx, roomVersion, backwardsExtremity.RoomID(), prevEventID, needed)
if err != nil {
util.GetLogger(ctx).WithError(err).Errorf("Failed to lookup state after prev_event: %s", prevEventID)
return err
}
states = append(states, prevState)
}
resolvedState, err := t.resolveStatesAndCheck(gmectx, roomVersion, states, backwardsExtremity)
if err != nil {
util.GetLogger(ctx).WithError(err).Errorf("Failed to resolve state conflicts for event %s", backwardsExtremity.EventID())
return err
}
// pass the event along with the state to the roomserver using a background context so we don't
// needlessly expire
return api.SendEventWithState(context.Background(), t.rsAPI, resolvedState, e.Headered(roomVersion), t.haveEventIDs())
}
// lookupStateAfterEvent returns the room state after `eventID`, which is the state before eventID with the state of `eventID` (if it's a state event)
// added into the mix.
func (t *txnReq) lookupStateAfterEvent(ctx context.Context, roomVersion gomatrixserverlib.RoomVersion, roomID, eventID string, needed []gomatrixserverlib.StateKeyTuple) (*gomatrixserverlib.RespState, error) {
// try doing all this locally before we resort to querying federation
respState := t.lookupStateAfterEventLocally(ctx, roomID, eventID, needed)
if respState != nil {
return respState, nil
}
respState, err := t.lookupStateBeforeEvent(ctx, roomVersion, roomID, eventID)
if err != nil {
return nil, err
}
// fetch the event we're missing and add it to the pile
h, err := t.lookupEvent(ctx, roomVersion, eventID, false)
switch err.(type) {
case verifySigError:
return respState, nil
case nil:
// do nothing
default:
return nil, err
}
t.haveEvents[h.EventID()] = h
if h.StateKey() != nil {
addedToState := false
for i := range respState.StateEvents {
se := respState.StateEvents[i]
if se.Type() == h.Type() && se.StateKeyEquals(*h.StateKey()) {
respState.StateEvents[i] = h.Unwrap()
addedToState = true
break
}
}
if !addedToState {
respState.StateEvents = append(respState.StateEvents, h.Unwrap())
}
}
return respState, nil
}
func (t *txnReq) lookupStateAfterEventLocally(ctx context.Context, roomID, eventID string, needed []gomatrixserverlib.StateKeyTuple) *gomatrixserverlib.RespState {
var res api.QueryStateAfterEventsResponse
err := t.rsAPI.QueryStateAfterEvents(ctx, &api.QueryStateAfterEventsRequest{
RoomID: roomID,
PrevEventIDs: []string{eventID},
StateToFetch: needed,
}, &res)
if err != nil || !res.PrevEventsExist {
util.GetLogger(ctx).WithError(err).Warnf("failed to query state after %s locally", eventID)
return nil
}
for i, ev := range res.StateEvents {
t.haveEvents[ev.EventID()] = &res.StateEvents[i]
}
var authEvents []gomatrixserverlib.Event
missingAuthEvents := make(map[string]bool)
for _, ev := range res.StateEvents {
for _, ae := range ev.AuthEventIDs() {
aev, ok := t.haveEvents[ae]
if ok {
authEvents = append(authEvents, aev.Unwrap())
} else {
missingAuthEvents[ae] = true
}
}
}
// QueryStateAfterEvents does not return the auth events, so fetch them now. We know the roomserver has them else it wouldn't
// have stored the event.
var missingEventList []string
for evID := range missingAuthEvents {
missingEventList = append(missingEventList, evID)
}
queryReq := api.QueryEventsByIDRequest{
EventIDs: missingEventList,
}
util.GetLogger(ctx).Infof("Fetching missing auth events: %v", missingEventList)
var queryRes api.QueryEventsByIDResponse
if err = t.rsAPI.QueryEventsByID(ctx, &queryReq, &queryRes); err != nil {
return nil
}
for i := range queryRes.Events {
evID := queryRes.Events[i].EventID()
t.haveEvents[evID] = &queryRes.Events[i]
authEvents = append(authEvents, queryRes.Events[i].Unwrap())
}
evs := gomatrixserverlib.UnwrapEventHeaders(res.StateEvents)
return &gomatrixserverlib.RespState{
StateEvents: evs,
AuthEvents: authEvents,
}
}
// lookuptStateBeforeEvent returns the room state before the event e, which is just /state_ids and/or /state depending on what
// the server supports.
func (t *txnReq) lookupStateBeforeEvent(ctx context.Context, roomVersion gomatrixserverlib.RoomVersion, roomID, eventID string) (
*gomatrixserverlib.RespState, error) {
util.GetLogger(ctx).Infof("lookupStateBeforeEvent %s", eventID)
// Attempt to fetch the missing state using /state_ids and /events
return t.lookupMissingStateViaStateIDs(ctx, roomID, eventID, roomVersion)
}
func (t *txnReq) resolveStatesAndCheck(ctx context.Context, roomVersion gomatrixserverlib.RoomVersion, states []*gomatrixserverlib.RespState, backwardsExtremity *gomatrixserverlib.Event) (*gomatrixserverlib.RespState, error) {
var authEventList []gomatrixserverlib.Event
var stateEventList []gomatrixserverlib.Event
for _, state := range states {
authEventList = append(authEventList, state.AuthEvents...)
stateEventList = append(stateEventList, state.StateEvents...)
}
resolvedStateEvents, err := gomatrixserverlib.ResolveConflicts(roomVersion, stateEventList, authEventList)
if err != nil {
return nil, err
}
// apply the current event
retryAllowedState:
if err = checkAllowedByState(*backwardsExtremity, resolvedStateEvents); err != nil {
switch missing := err.(type) {
case gomatrixserverlib.MissingAuthEventError:
h, err2 := t.lookupEvent(ctx, roomVersion, missing.AuthEventID, true)
switch err2.(type) {
case verifySigError:
return &gomatrixserverlib.RespState{
AuthEvents: authEventList,
StateEvents: resolvedStateEvents,
}, nil
case nil:
// do nothing
default:
return nil, fmt.Errorf("missing auth event %s and failed to look it up: %w", missing.AuthEventID, err2)
}
util.GetLogger(ctx).Infof("fetched event %s", missing.AuthEventID)
resolvedStateEvents = append(resolvedStateEvents, h.Unwrap())
goto retryAllowedState
default:
}
return nil, err
}
return &gomatrixserverlib.RespState{
AuthEvents: authEventList,
StateEvents: resolvedStateEvents,
}, nil
}
// getMissingEvents returns a nil backwardsExtremity if missing events were fetched and handled, else returns the new backwards extremity which we should
// begin from. Returns an error only if we should terminate the transaction which initiated /get_missing_events
// This function recursively calls txnReq.processEvent with the missing events, which will be processed before this function returns.
// This means that we may recursively call this function, as we spider back up prev_events.
// nolint:gocyclo
func (t *txnReq) getMissingEvents(ctx context.Context, e gomatrixserverlib.Event, roomVersion gomatrixserverlib.RoomVersion, isInboundTxn bool) (backwardsExtremity *gomatrixserverlib.Event, err error) {
if !isInboundTxn {
// we've recursed here, so just take a state snapshot please!
return &e, nil
}
logger := util.GetLogger(ctx).WithField("event_id", e.EventID()).WithField("room_id", e.RoomID())
needed := gomatrixserverlib.StateNeededForAuth([]gomatrixserverlib.Event{e})
// query latest events (our trusted forward extremities)
req := api.QueryLatestEventsAndStateRequest{
RoomID: e.RoomID(),
StateToFetch: needed.Tuples(),
}
var res api.QueryLatestEventsAndStateResponse
if err = t.rsAPI.QueryLatestEventsAndState(ctx, &req, &res); err != nil {
logger.WithError(err).Warn("Failed to query latest events")
return &e, nil
}
latestEvents := make([]string, len(res.LatestEvents))
for i := range res.LatestEvents {
latestEvents[i] = res.LatestEvents[i].EventID
}
servers := []gomatrixserverlib.ServerName{t.Origin}
serverReq := &api.QueryServerJoinedToRoomRequest{
RoomID: e.RoomID(),
}
serverRes := &api.QueryServerJoinedToRoomResponse{}
if err = t.rsAPI.QueryServerJoinedToRoom(ctx, serverReq, serverRes); err == nil {
servers = append(servers, serverRes.ServerNames...)
logger.Infof("Found %d server(s) to query for missing events", len(servers))
}
var missingResp *gomatrixserverlib.RespMissingEvents
for _, server := range servers {
var m gomatrixserverlib.RespMissingEvents
if m, err = t.federation.LookupMissingEvents(ctx, server, e.RoomID(), gomatrixserverlib.MissingEvents{
Limit: 20,
// The latest event IDs that the sender already has. These are skipped when retrieving the previous events of latest_events.
EarliestEvents: latestEvents,
// The event IDs to retrieve the previous events for.
LatestEvents: []string{e.EventID()},
}, roomVersion); err == nil {
missingResp = &m
break
} else {
logger.WithError(err).Errorf("%s pushed us an event but %q did not respond to /get_missing_events", t.Origin, server)
}
}
if missingResp == nil {
logger.WithError(err).Errorf(
"%s pushed us an event but %d server(s) couldn't give us details about prev_events via /get_missing_events - dropping this event until it can",
t.Origin, len(servers),
)
return nil, missingPrevEventsError{
eventID: e.EventID(),
err: err,
}
}
// security: how we handle failures depends on whether or not this event will become the new forward extremity for the room.
// There's 2 scenarios to consider:
// - Case A: We got pushed an event and are now fetching missing prev_events. (isInboundTxn=true)
// - Case B: We are fetching missing prev_events already and now fetching some more (isInboundTxn=false)
// In Case B, we know for sure that the event we are currently processing will not become the new forward extremity for the room,
// as it was called in response to an inbound txn which had it as a prev_event.
// In Case A, the event is a forward extremity, and could eventually become the _only_ forward extremity in the room. This is bad
// because it means we would trust the state at that event to be the state for the entire room, and allows rooms to be hijacked.
// https://github.com/matrix-org/synapse/pull/3456
// https://github.com/matrix-org/synapse/blob/229eb81498b0fe1da81e9b5b333a0285acde9446/synapse/handlers/federation.py#L335
// For now, we do not allow Case B, so reject the event.
logger.Infof("get_missing_events returned %d events", len(missingResp.Events))
// topologically sort and sanity check that we are making forward progress
newEvents := gomatrixserverlib.ReverseTopologicalOrdering(missingResp.Events, gomatrixserverlib.TopologicalOrderByPrevEvents)
shouldHaveSomeEventIDs := e.PrevEventIDs()
hasPrevEvent := false
Event:
for _, pe := range shouldHaveSomeEventIDs {
for _, ev := range newEvents {
if ev.EventID() == pe {
hasPrevEvent = true
break Event
}
}
}
if !hasPrevEvent {
err = fmt.Errorf("called /get_missing_events but server %s didn't return any prev_events with IDs %v", t.Origin, shouldHaveSomeEventIDs)
logger.WithError(err).Errorf(
"%s pushed us an event but couldn't give us details about prev_events via /get_missing_events - dropping this event until it can",
t.Origin,
)
return nil, missingPrevEventsError{
eventID: e.EventID(),
err: err,
}
}
// process the missing events then the event which started this whole thing
for _, ev := range append(newEvents, e) {
err := t.processEvent(ctx, ev, false)
if err != nil {
return nil, err
}
}
// we processed everything!
return nil, nil
}
func (t *txnReq) lookupMissingStateViaState(ctx context.Context, roomID, eventID string, roomVersion gomatrixserverlib.RoomVersion) (
respState *gomatrixserverlib.RespState, err error) {
state, err := t.federation.LookupState(ctx, t.Origin, roomID, eventID, roomVersion)
if err != nil {
return nil, err
}
// Check that the returned state is valid.
if err := state.Check(ctx, t.keys, nil); err != nil {
return nil, err
}
return &state, nil
}
// nolint:gocyclo
func (t *txnReq) lookupMissingStateViaStateIDs(ctx context.Context, roomID, eventID string, roomVersion gomatrixserverlib.RoomVersion) (
*gomatrixserverlib.RespState, error) {
util.GetLogger(ctx).Infof("lookupMissingStateViaStateIDs %s", eventID)
// fetch the state event IDs at the time of the event
stateIDs, err := t.federation.LookupStateIDs(ctx, t.Origin, roomID, eventID)
if err != nil {
return nil, err
}
// work out which auth/state IDs are missing
wantIDs := append(stateIDs.StateEventIDs, stateIDs.AuthEventIDs...)
missing := make(map[string]bool)
var missingEventList []string
for _, sid := range wantIDs {
if _, ok := t.haveEvents[sid]; !ok {
if !missing[sid] {
missing[sid] = true
missingEventList = append(missingEventList, sid)
}
}
}
// fetch as many as we can from the roomserver
queryReq := api.QueryEventsByIDRequest{
EventIDs: missingEventList,
}
var queryRes api.QueryEventsByIDResponse
if err = t.rsAPI.QueryEventsByID(ctx, &queryReq, &queryRes); err != nil {
return nil, err
}
for i := range queryRes.Events {
evID := queryRes.Events[i].EventID()
t.haveEvents[evID] = &queryRes.Events[i]
if missing[evID] {
delete(missing, evID)
}
}
concurrentRequests := 8
missingCount := len(missing)
// If over 50% of the auth/state events from /state_ids are missing
// then we'll just call /state instead, otherwise we'll just end up
// hammering the remote side with /event requests unnecessarily.
if missingCount > concurrentRequests && missingCount > len(wantIDs)/2 {
util.GetLogger(ctx).WithFields(logrus.Fields{
"missing": missingCount,
"event_id": eventID,
"room_id": roomID,
"total_state": len(stateIDs.StateEventIDs),
"total_auth_events": len(stateIDs.AuthEventIDs),
}).Info("Fetching all state at event")
return t.lookupMissingStateViaState(ctx, roomID, eventID, roomVersion)
}
util.GetLogger(ctx).WithFields(logrus.Fields{
"missing": missingCount,
"event_id": eventID,
"room_id": roomID,
"total_state": len(stateIDs.StateEventIDs),
"total_auth_events": len(stateIDs.AuthEventIDs),
"concurrent_requests": concurrentRequests,
}).Info("Fetching missing state at event")
// Create a queue containing all of the missing event IDs that we want
// to retrieve.
pending := make(chan string, missingCount)
for missingEventID := range missing {
pending <- missingEventID
}
close(pending)
// Define how many workers we should start to do this.
if missingCount < concurrentRequests {
concurrentRequests = missingCount
}
// Create the wait group.
var fetchgroup sync.WaitGroup
fetchgroup.Add(concurrentRequests)
// This is the only place where we'll write to t.haveEvents from
// multiple goroutines, and everywhere else is blocked on this
// synchronous function anyway.
var haveEventsMutex sync.Mutex
// Define what we'll do in order to fetch the missing event ID.
fetch := func(missingEventID string) {
var h *gomatrixserverlib.HeaderedEvent
h, err = t.lookupEvent(ctx, roomVersion, missingEventID, false)
switch err.(type) {
case verifySigError:
break
case nil:
break
default:
util.GetLogger(ctx).WithFields(logrus.Fields{
"event_id": missingEventID,
"room_id": roomID,
}).Info("Failed to fetch missing event")
return
}
haveEventsMutex.Lock()
t.haveEvents[h.EventID()] = h
haveEventsMutex.Unlock()
}
// Create the worker.
worker := func(ch <-chan string) {
defer fetchgroup.Done()
for missingEventID := range ch {
fetch(missingEventID)
}
}
// Start the workers.
for i := 0; i < concurrentRequests; i++ {
go worker(pending)
}
// Wait for the workers to finish.
fetchgroup.Wait()
resp, err := t.createRespStateFromStateIDs(stateIDs)
return resp, err
}
func (t *txnReq) createRespStateFromStateIDs(stateIDs gomatrixserverlib.RespStateIDs) (
*gomatrixserverlib.RespState, error) {
// create a RespState response using the response to /state_ids as a guide
respState := gomatrixserverlib.RespState{
AuthEvents: make([]gomatrixserverlib.Event, len(stateIDs.AuthEventIDs)),
StateEvents: make([]gomatrixserverlib.Event, len(stateIDs.StateEventIDs)),
}
for i := range stateIDs.StateEventIDs {
ev, ok := t.haveEvents[stateIDs.StateEventIDs[i]]
if !ok {
return nil, fmt.Errorf("missing state event %s", stateIDs.StateEventIDs[i])
}
respState.StateEvents[i] = ev.Unwrap()
}
for i := range stateIDs.AuthEventIDs {
ev, ok := t.haveEvents[stateIDs.AuthEventIDs[i]]
if !ok {
return nil, fmt.Errorf("missing auth event %s", stateIDs.AuthEventIDs[i])
}
respState.AuthEvents[i] = ev.Unwrap()
}
// We purposefully do not do auth checks on the returned events, as they will still
// be processed in the exact same way, just as a 'rejected' event
// TODO: Add a field to HeaderedEvent to indicate if the event is rejected.
return &respState, nil
}
func (t *txnReq) lookupEvent(ctx context.Context, roomVersion gomatrixserverlib.RoomVersion, missingEventID string, localFirst bool) (*gomatrixserverlib.HeaderedEvent, error) {
if localFirst {
// fetch from the roomserver
queryReq := api.QueryEventsByIDRequest{
EventIDs: []string{missingEventID},
}
var queryRes api.QueryEventsByIDResponse
if err := t.rsAPI.QueryEventsByID(ctx, &queryReq, &queryRes); err != nil {
util.GetLogger(ctx).Warnf("Failed to query roomserver for missing event %s: %s - falling back to remote", missingEventID, err)
} else if len(queryRes.Events) == 1 {
return &queryRes.Events[0], nil
}
}
txn, err := t.federation.GetEvent(ctx, t.Origin, missingEventID)
if err != nil || len(txn.PDUs) == 0 {
util.GetLogger(ctx).WithError(err).WithField("event_id", missingEventID).Warn("failed to get missing /event for event ID")
return nil, err
}
pdu := txn.PDUs[0]
var event gomatrixserverlib.Event
event, err = gomatrixserverlib.NewEventFromUntrustedJSON(pdu, roomVersion)
if err != nil {
util.GetLogger(ctx).WithError(err).Warnf("Transaction: Failed to parse event JSON of event %q", event.EventID())
return nil, unmarshalError{err}
}
if err = gomatrixserverlib.VerifyAllEventSignatures(ctx, []gomatrixserverlib.Event{event}, t.keys); err != nil {
util.GetLogger(ctx).WithError(err).Warnf("Transaction: Couldn't validate signature of event %q", event.EventID())
return nil, verifySigError{event.EventID(), err}
}
h := event.Headered(roomVersion)
t.newEvents[h.EventID()] = true
return &h, nil
}