/
keybackup.go
184 lines (155 loc) · 5.77 KB
/
keybackup.go
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package crypto
import (
"context"
"fmt"
"time"
"github.com/rs/zerolog"
"maunium.net/go/mautrix"
"maunium.net/go/mautrix/crypto/backup"
"maunium.net/go/mautrix/crypto/olm"
"maunium.net/go/mautrix/crypto/signatures"
"maunium.net/go/mautrix/id"
)
func (mach *OlmMachine) DownloadAndStoreLatestKeyBackup(ctx context.Context, megolmBackupKey *backup.MegolmBackupKey) (id.KeyBackupVersion, error) {
log := mach.machOrContextLog(ctx).With().
Str("action", "download and store latest key backup").
Logger()
ctx = log.WithContext(ctx)
versionInfo, err := mach.GetAndVerifyLatestKeyBackupVersion(ctx)
if err != nil {
return "", err
} else if versionInfo == nil {
return "", nil
}
err = mach.GetAndStoreKeyBackup(ctx, versionInfo.Version, megolmBackupKey)
return versionInfo.Version, err
}
func (mach *OlmMachine) GetAndVerifyLatestKeyBackupVersion(ctx context.Context) (*mautrix.RespRoomKeysVersion[backup.MegolmAuthData], error) {
versionInfo, err := mach.Client.GetKeyBackupLatestVersion(ctx)
if err != nil {
return nil, err
}
if versionInfo.Algorithm != id.KeyBackupAlgorithmMegolmBackupV1 {
return nil, fmt.Errorf("unsupported key backup algorithm: %s", versionInfo.Algorithm)
}
log := mach.machOrContextLog(ctx).With().
Int("count", versionInfo.Count).
Str("etag", versionInfo.ETag).
Stringer("key_backup_version", versionInfo.Version).
Logger()
userSignatures, ok := versionInfo.AuthData.Signatures[mach.Client.UserID]
if !ok {
return nil, fmt.Errorf("no signature from user %s found in key backup", mach.Client.UserID)
}
crossSigningPubkeys := mach.GetOwnCrossSigningPublicKeys(ctx)
signatureVerified := false
for keyID := range userSignatures {
keyAlg, keyName := keyID.Parse()
if keyAlg != id.KeyAlgorithmEd25519 {
continue
}
log := log.With().Str("key_name", keyName).Logger()
var key id.Ed25519
if keyName == crossSigningPubkeys.MasterKey.String() {
key = crossSigningPubkeys.MasterKey
} else if device, err := mach.GetOrFetchDevice(ctx, mach.Client.UserID, id.DeviceID(keyName)); err != nil {
log.Warn().Err(err).Msg("Failed to fetch device")
continue
} else if !mach.IsDeviceTrusted(device) {
log.Warn().Err(err).Msg("Device is not trusted")
continue
} else {
key = device.SigningKey
}
ok, err = signatures.VerifySignatureJSON(versionInfo.AuthData, mach.Client.UserID, keyName, key)
if err != nil || !ok {
log.Warn().Err(err).Stringer("key_id", keyID).Msg("Signature verification failed")
continue
} else {
// One of the signatures is valid, break from the loop.
signatureVerified = true
break
}
}
if !signatureVerified {
return nil, fmt.Errorf("no valid signature from user %s found in key backup", mach.Client.UserID)
}
return versionInfo, nil
}
func (mach *OlmMachine) GetAndStoreKeyBackup(ctx context.Context, version id.KeyBackupVersion, megolmBackupKey *backup.MegolmBackupKey) error {
keys, err := mach.Client.GetKeyBackup(ctx, version)
if err != nil {
return err
}
log := zerolog.Ctx(ctx)
var count, failedCount int
for roomID, backup := range keys.Rooms {
for sessionID, keyBackupData := range backup.Sessions {
sessionData, err := keyBackupData.SessionData.Decrypt(megolmBackupKey)
if err != nil {
log.Warn().Err(err).Msg("Failed to decrypt session data")
failedCount++
continue
}
err = mach.ImportRoomKeyFromBackup(ctx, version, roomID, sessionID, sessionData)
if err != nil {
log.Warn().Err(err).Msg("Failed to import room key from backup")
failedCount++
continue
}
count++
}
}
log.Info().
Int("count", count).
Int("failed_count", failedCount).
Msg("successfully imported sessions from backup")
return nil
}
func (mach *OlmMachine) ImportRoomKeyFromBackup(ctx context.Context, version id.KeyBackupVersion, roomID id.RoomID, sessionID id.SessionID, keyBackupData *backup.MegolmSessionData) error {
log := zerolog.Ctx(ctx).With().
Str("room_id", roomID.String()).
Str("session_id", sessionID.String()).
Logger()
if keyBackupData.Algorithm != id.AlgorithmMegolmV1 {
return fmt.Errorf("ignoring room key in backup with weird algorithm %s", keyBackupData.Algorithm)
}
igsInternal, err := olm.InboundGroupSessionImport([]byte(keyBackupData.SessionKey))
if err != nil {
return fmt.Errorf("failed to import inbound group session: %w", err)
} else if igsInternal.ID() != sessionID {
log.Warn().
Stringer("actual_session_id", igsInternal.ID()).
Msg("Mismatched session ID while creating inbound group session from key backup")
return fmt.Errorf("mismatched session ID while creating inbound group session from key backup")
}
var maxAge time.Duration
var maxMessages int
if config, err := mach.StateStore.GetEncryptionEvent(ctx, roomID); err != nil {
log.Error().Err(err).Msg("Failed to get encryption event for room")
} else if config != nil {
maxAge = time.Duration(config.RotationPeriodMillis) * time.Millisecond
maxMessages = config.RotationPeriodMessages
}
if firstKnownIndex := igsInternal.FirstKnownIndex(); firstKnownIndex > 0 {
log.Warn().Uint32("first_known_index", firstKnownIndex).Msg("Importing partial session")
}
igs := &InboundGroupSession{
Internal: *igsInternal,
SigningKey: keyBackupData.SenderClaimedKeys.Ed25519,
SenderKey: keyBackupData.SenderKey,
RoomID: roomID,
ForwardingChains: append(keyBackupData.ForwardingKeyChain, keyBackupData.SenderKey.String()),
id: sessionID,
ReceivedAt: time.Now().UTC(),
MaxAge: maxAge.Milliseconds(),
MaxMessages: maxMessages,
KeyBackupVersion: version,
}
err = mach.CryptoStore.PutGroupSession(ctx, roomID, keyBackupData.SenderKey, sessionID, igs)
if err != nil {
return fmt.Errorf("failed to store new inbound group session: %w", err)
}
mach.markSessionReceived(ctx, sessionID)
return nil
}