280 lines
11 KiB
Go
280 lines
11 KiB
Go
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// Copyright (c) 2020 Tulir Asokan
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, You can obtain one at http://mozilla.org/MPL/2.0/.
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package crypto
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import (
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"encoding/json"
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"errors"
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"fmt"
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"maunium.net/go/mautrix"
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"maunium.net/go/mautrix/event"
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"maunium.net/go/mautrix/id"
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)
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var (
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AlreadyShared = errors.New("group session already shared")
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NoGroupSession = errors.New("no group session created")
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)
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func getRelatesTo(content interface{}) *event.RelatesTo {
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contentStruct, ok := content.(*event.Content)
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if ok {
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content = contentStruct.Parsed
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}
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relatable, ok := content.(event.Relatable)
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if ok {
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return relatable.OptionalGetRelatesTo()
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}
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return nil
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}
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type rawMegolmEvent struct {
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RoomID id.RoomID `json:"room_id"`
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Type event.Type `json:"type"`
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Content interface{} `json:"content"`
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}
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// IsShareError returns true if the error is caused by the lack of an outgoing megolm session and can be solved with OlmMachine.ShareGroupSession
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func IsShareError(err error) bool {
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return err == SessionExpired || err == SessionNotShared || err == NoGroupSession
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}
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// EncryptMegolmEvent encrypts data with the m.megolm.v1.aes-sha2 algorithm.
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//
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// If you use the event.Content struct, make sure you pass a pointer to the struct,
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// as JSON serialization will not work correctly otherwise.
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func (mach *OlmMachine) EncryptMegolmEvent(roomID id.RoomID, evtType event.Type, content interface{}) (*event.EncryptedEventContent, error) {
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mach.Log.Trace("Encrypting event of type %s for %s", evtType.Type, roomID)
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session, err := mach.CryptoStore.GetOutboundGroupSession(roomID)
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if err != nil {
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return nil, fmt.Errorf("failed to get outbound group session: %w", err)
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} else if session == nil {
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return nil, NoGroupSession
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}
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plaintext, err := json.Marshal(&rawMegolmEvent{
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RoomID: roomID,
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Type: evtType,
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Content: content,
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})
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if err != nil {
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return nil, err
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}
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ciphertext, err := session.Encrypt(plaintext)
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if err != nil {
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return nil, err
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}
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err = mach.CryptoStore.UpdateOutboundGroupSession(session)
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if err != nil {
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mach.Log.Warn("Failed to update megolm session in crypto store after encrypting: %v", err)
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}
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return &event.EncryptedEventContent{
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Algorithm: id.AlgorithmMegolmV1,
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SenderKey: mach.account.IdentityKey(),
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DeviceID: mach.Client.DeviceID,
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SessionID: session.ID(),
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MegolmCiphertext: ciphertext,
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RelatesTo: getRelatesTo(content),
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}, nil
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}
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func (mach *OlmMachine) newOutboundGroupSession(roomID id.RoomID) *OutboundGroupSession {
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session := NewOutboundGroupSession(roomID, mach.StateStore.GetEncryptionEvent(roomID))
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signingKey, idKey := mach.account.Keys()
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mach.createGroupSession(idKey, signingKey, roomID, session.ID(), session.Internal.Key(), "create")
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return session
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}
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type deviceSessionWrapper struct {
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session *OlmSession
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identity *DeviceIdentity
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}
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// ShareGroupSession shares a group session for a specific room with all the devices of the given user list.
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//
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// For devices with TrustStateBlacklisted, a m.room_key.withheld event with code=m.blacklisted is sent.
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// If AllowUnverifiedDevices is false, a similar event with code=m.unverified is sent to devices with TrustStateUnset
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func (mach *OlmMachine) ShareGroupSession(roomID id.RoomID, users []id.UserID) error {
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mach.Log.Debug("Sharing group session for room %s to %v", roomID, users)
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session, err := mach.CryptoStore.GetOutboundGroupSession(roomID)
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if err != nil {
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return fmt.Errorf("failed to get previous outbound group session: %w", err)
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} else if session != nil && session.Shared && !session.Expired() {
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return AlreadyShared
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}
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if session == nil || session.Expired() {
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session = mach.newOutboundGroupSession(roomID)
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}
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withheldCount := 0
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toDeviceWithheld := &mautrix.ReqSendToDevice{Messages: make(map[id.UserID]map[id.DeviceID]*event.Content)}
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olmSessions := make(map[id.UserID]map[id.DeviceID]deviceSessionWrapper)
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missingSessions := make(map[id.UserID]map[id.DeviceID]*DeviceIdentity)
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missingUserSessions := make(map[id.DeviceID]*DeviceIdentity)
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var fetchKeys []id.UserID
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for _, userID := range users {
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devices, err := mach.CryptoStore.GetDevices(userID)
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if err != nil {
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mach.Log.Error("Failed to get devices of %s", userID)
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} else if devices == nil {
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mach.Log.Trace("GetDevices returned nil for %s, will fetch keys and retry", userID)
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fetchKeys = append(fetchKeys, userID)
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} else if len(devices) == 0 {
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mach.Log.Trace("%s has no devices, skipping", userID)
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} else {
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mach.Log.Trace("Trying to find olm sessions to encrypt %s for %s", session.ID(), userID)
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toDeviceWithheld.Messages[userID] = make(map[id.DeviceID]*event.Content)
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olmSessions[userID] = make(map[id.DeviceID]deviceSessionWrapper)
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mach.findOlmSessionsForUser(session, userID, devices, olmSessions[userID], toDeviceWithheld.Messages[userID], missingUserSessions)
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mach.Log.Trace("Found %d sessions, withholding from %d sessions and missing %d sessions to encrypt %s for for %s", len(olmSessions[userID]), len(toDeviceWithheld.Messages[userID]), len(missingUserSessions), session.ID(), userID)
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withheldCount += len(toDeviceWithheld.Messages[userID])
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if len(missingUserSessions) > 0 {
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missingSessions[userID] = missingUserSessions
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missingUserSessions = make(map[id.DeviceID]*DeviceIdentity)
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}
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if len(toDeviceWithheld.Messages[userID]) == 0 {
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delete(toDeviceWithheld.Messages, userID)
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}
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}
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}
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if len(fetchKeys) > 0 {
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mach.Log.Trace("Fetching missing keys for %v", fetchKeys)
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for userID, devices := range mach.fetchKeys(fetchKeys, "", true) {
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mach.Log.Trace("Got %d device keys for %s", len(devices), userID)
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missingSessions[userID] = devices
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}
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}
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if len(missingSessions) > 0 {
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mach.Log.Trace("Creating missing outbound sessions")
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err = mach.createOutboundSessions(missingSessions)
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if err != nil {
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mach.Log.Error("Failed to create missing outbound sessions: %v", err)
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}
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}
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for userID, devices := range missingSessions {
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if len(devices) == 0 {
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// No missing sessions
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continue
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}
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output, ok := olmSessions[userID]
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if !ok {
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output = make(map[id.DeviceID]deviceSessionWrapper)
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olmSessions[userID] = output
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}
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withheld, ok := toDeviceWithheld.Messages[userID]
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if !ok {
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withheld = make(map[id.DeviceID]*event.Content)
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toDeviceWithheld.Messages[userID] = withheld
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}
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mach.Log.Trace("Trying to find olm sessions to encrypt %s for %s (post-fetch retry)", session.ID(), userID)
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mach.findOlmSessionsForUser(session, userID, devices, output, withheld, nil)
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mach.Log.Trace("Found %d sessions and withholding from %d sessions to encrypt %s for for %s (post-fetch retry)", len(output), len(withheld), session.ID(), userID)
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withheldCount += len(toDeviceWithheld.Messages[userID])
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if len(toDeviceWithheld.Messages[userID]) == 0 {
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delete(toDeviceWithheld.Messages, userID)
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}
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}
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err = mach.encryptAndSendGroupSession(session, olmSessions)
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if err != nil {
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return fmt.Errorf("failed to share group session: %w", err)
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}
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if len(toDeviceWithheld.Messages) > 0 {
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mach.Log.Trace("Sending to-device messages to %d devices of %d users to report withheld keys in %s", withheldCount, len(toDeviceWithheld.Messages), roomID)
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// TODO remove the next 4 lines once clients support m.room_key.withheld
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_, err = mach.Client.SendToDevice(event.ToDeviceOrgMatrixRoomKeyWithheld, toDeviceWithheld)
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if err != nil {
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mach.Log.Warn("Failed to report withheld keys in %s (legacy event type): %v", roomID, err)
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}
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_, err = mach.Client.SendToDevice(event.ToDeviceRoomKeyWithheld, toDeviceWithheld)
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if err != nil {
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mach.Log.Warn("Failed to report withheld keys in %s: %v", roomID, err)
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}
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}
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mach.Log.Debug("Group session %s for %s successfully shared", session.ID(), roomID)
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session.Shared = true
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return mach.CryptoStore.AddOutboundGroupSession(session)
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}
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func (mach *OlmMachine) encryptAndSendGroupSession(session *OutboundGroupSession, olmSessions map[id.UserID]map[id.DeviceID]deviceSessionWrapper) error {
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mach.olmLock.Lock()
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defer mach.olmLock.Unlock()
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mach.Log.Trace("Encrypting group session %s for all found devices", session.ID())
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deviceCount := 0
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toDevice := &mautrix.ReqSendToDevice{Messages: make(map[id.UserID]map[id.DeviceID]*event.Content)}
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for userID, sessions := range olmSessions {
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if len(sessions) == 0 {
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continue
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}
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output := make(map[id.DeviceID]*event.Content)
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toDevice.Messages[userID] = output
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for deviceID, device := range sessions {
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mach.Log.Trace("Encrypting group session %s for %s of %s", session.ID(), deviceID, userID)
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content := mach.encryptOlmEvent(device.session, device.identity, event.ToDeviceRoomKey, session.ShareContent())
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output[deviceID] = &event.Content{Parsed: content}
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deviceCount++
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mach.Log.Trace("Encrypted group session %s for %s of %s", session.ID(), deviceID, userID)
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}
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}
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mach.Log.Trace("Sending to-device to %d devices of %d users to share group session %s", deviceCount, len(toDevice.Messages), session.ID())
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_, err := mach.Client.SendToDevice(event.ToDeviceEncrypted, toDevice)
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return err
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}
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func (mach *OlmMachine) findOlmSessionsForUser(session *OutboundGroupSession, userID id.UserID, devices map[id.DeviceID]*DeviceIdentity, output map[id.DeviceID]deviceSessionWrapper, withheld map[id.DeviceID]*event.Content, missingOutput map[id.DeviceID]*DeviceIdentity) {
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for deviceID, device := range devices {
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userKey := UserDevice{UserID: userID, DeviceID: deviceID}
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if state := session.Users[userKey]; state != OGSNotShared {
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continue
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} else if userID == mach.Client.UserID && deviceID == mach.Client.DeviceID {
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session.Users[userKey] = OGSIgnored
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} else if device.Trust == TrustStateBlacklisted {
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mach.Log.Debug("Not encrypting group session %s for %s of %s: device is blacklisted", session.ID(), deviceID, userID)
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withheld[deviceID] = &event.Content{Parsed: &event.RoomKeyWithheldEventContent{
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RoomID: session.RoomID,
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Algorithm: id.AlgorithmMegolmV1,
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SessionID: session.ID(),
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SenderKey: mach.account.IdentityKey(),
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Code: event.RoomKeyWithheldBlacklisted,
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Reason: "Device is blacklisted",
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}}
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session.Users[userKey] = OGSIgnored
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} else if !mach.AllowUnverifiedDevices && !mach.IsDeviceTrusted(device) {
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mach.Log.Debug("Not encrypting group session %s for %s of %s: device is not verified", session.ID(), deviceID, userID)
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withheld[deviceID] = &event.Content{Parsed: &event.RoomKeyWithheldEventContent{
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RoomID: session.RoomID,
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Algorithm: id.AlgorithmMegolmV1,
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SessionID: session.ID(),
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SenderKey: mach.account.IdentityKey(),
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Code: event.RoomKeyWithheldUnverified,
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Reason: "This device does not encrypt messages for unverified devices",
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}}
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session.Users[userKey] = OGSIgnored
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} else if deviceSession, err := mach.CryptoStore.GetLatestSession(device.IdentityKey); err != nil {
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mach.Log.Error("Failed to get session for %s of %s: %v", deviceID, userID, err)
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} else if deviceSession == nil {
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mach.Log.Warn("Didn't find a session for %s of %s", deviceID, userID)
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if missingOutput != nil {
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missingOutput[deviceID] = device
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}
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} else {
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output[deviceID] = deviceSessionWrapper{
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session: deviceSession,
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identity: device,
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}
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session.Users[userKey] = OGSAlreadyShared
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}
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}
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}
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