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dendrite/federationapi/routing/send.go
Kegsay 18231f25b4
Implement rejected events (#1426)
* WIP Event rejection

* Still send back errors for rejected events

Instead, discard them at the federationapi /send layer rather than
re-implementing checks at the clientapi/PerformJoin layer.

* Implement rejected events

Critically, rejected events CAN cause state resolution to happen
as it can merge forks in the DAG. This is fine, _provided_ we
do not add the rejected event when performing state resolution,
which is what this PR does. It also fixes the error handling
when NotAllowed happens, as we were checking too early and needlessly
handling NotAllowed in more than one place.

* Update test to match reality

* Modify InputRoomEvents to no longer return an error

Errors do not serialise across HTTP boundaries in polylith mode,
so instead set fields on the InputRoomEventsResponse. Add `Err()`
function to make the API shape basically the same.

* Remove redundant returns; linting

* Update blacklist
2020-09-16 13:00:52 +01:00

849 lines
32 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"
"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
_, rejected := err.(*gomatrixserverlib.NotAllowed)
errMsg := err.Error()
if rejected {
errMsg = ""
}
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 {
prevEventIDs := e.PrevEventIDs()
// Fetch the state needed to authenticate the event.
needed := gomatrixserverlib.StateNeededForAuth([]gomatrixserverlib.Event{e})
stateReq := api.QueryStateAfterEventsRequest{
RoomID: e.RoomID(),
PrevEventIDs: prevEventIDs,
StateToFetch: needed.Tuples(),
}
var stateResp api.QueryStateAfterEventsResponse
if err := t.rsAPI.QueryStateAfterEvents(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 !stateResp.PrevEventsExist {
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) (
respState *gomatrixserverlib.RespState, err error) {
util.GetLogger(ctx).Infof("lookupStateBeforeEvent %s", eventID)
// Attempt to fetch the missing state using /state_ids and /events
respState, err = t.lookupMissingStateViaStateIDs(ctx, roomID, eventID, roomVersion)
if err != nil {
// Fallback to /state
util.GetLogger(ctx).WithError(err).Warn("lookupStateBeforeEvent failed to /state_ids, falling back to /state")
respState, err = t.lookupMissingStateViaState(ctx, roomID, eventID, roomVersion)
}
return
}
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 to the min depth.
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
}
// this server just sent us an event for which we do not know its prev_events - ask that server for those prev_events.
minDepth := int(res.Depth) - 20
if minDepth < 0 {
minDepth = 0
}
missingResp, err := t.federation.LookupMissingEvents(ctx, t.Origin, e.RoomID(), gomatrixserverlib.MissingEvents{
Limit: 20,
// synapse uses the min depth they've ever seen in that room
MinDepth: minDepth,
// 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)
// 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.
if err != nil {
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,
}
}
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
}
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)
}
}
util.GetLogger(ctx).WithFields(logrus.Fields{
"missing": len(missing),
"event_id": eventID,
"room_id": roomID,
"total_state": len(stateIDs.StateEventIDs),
"total_auth_events": len(stateIDs.AuthEventIDs),
}).Info("Fetching missing state at event")
for missingEventID := range missing {
var h *gomatrixserverlib.HeaderedEvent
h, err = t.lookupEvent(ctx, roomVersion, missingEventID, false)
switch err.(type) {
case verifySigError:
continue
case nil:
// do nothing
default:
return nil, err
}
t.haveEvents[h.EventID()] = h
}
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
}