sqldb: add network validation interface and backends

Author: ziggie1984

sqldb/interfaces.go

@@ -401,6 +401,12 @@ type DB interface {
 	// both sqlc and custom in-code migrations.
 	ApplyAllMigrations(ctx context.Context,
 		customMigrations []MigrationConfig) error
+
+	// ValidateNetwork checks that the database was initialised for the
+	// given Bitcoin network and returns an error if there is a mismatch.
+	// On the very first call the network is recorded so that subsequent
+	// calls can detect a change.
+	ValidateNetwork(ctx context.Context, network string) error
 }
 
 // BaseDB is the base database struct that each implementation can embed to

sqldb/no_sqlite.go

@@ -38,3 +38,11 @@ func (s *SqliteStore) ApplyAllMigrations(context.Context,
 
 	return fmt.Errorf("SQLite backend not supported in WebAssembly")
 }
+
+// ValidateNetwork is a no-op for the no-sqlite build; this backend is not
+// usable and always returns errors on initialization.
+//
+// NOTE: This is part of the sqldb.DB interface.
+func (s *SqliteStore) ValidateNetwork(context.Context, string) error {
+	return nil
+}

sqldb/postgres.go

@@ -186,6 +186,69 @@ func (s *PostgresStore) ExecuteMigrations(target MigrationTarget) error {
 	)
 }
 
+// metadataNetworkKey is the key used to store the network name in the metadata
+// table.
+const metadataNetworkKey = "network"
+
+// ValidateNetwork checks that the network stored in the metadata table matches
+// the provided network name. On the first call the network is persisted so
+// that subsequent restarts can detect an accidental network switch.
+//
+// This prevents silent data corruption when a user points the same postgres
+// DSN at a different Bitcoin network.
+//
+// NOTE: This is part of the sqldb.DB interface.
+func (s *PostgresStore) ValidateNetwork(ctx context.Context,
+	network string) error {
+
+	return s.BaseDB.ValidateNetwork(ctx, network)
+}
+
+// ValidateNetwork checks that the network stored in the metadata table matches
+// the provided network name. On the first call the network is persisted so
+// that subsequent restarts can detect an accidental network switch.
+func (b *BaseDB) ValidateNetwork(ctx context.Context, network string) error {
+	executor := NewTransactionExecutor(
+		b, func(tx *sql.Tx) *sqlc.Queries {
+			return b.WithTx(tx)
+		},
+	)
+
+	return executor.ExecTx(ctx, WriteTxOpt(), func(tx *sqlc.Queries) error {
+		// Insert the network only if the key doesn't exist yet.
+		// ON CONFLICT DO NOTHING means this is a no-op on every
+		// startup after the first.
+		err := tx.SetMetaValue(ctx, sqlc.SetMetaValueParams{
+			Key:   metadataNetworkKey,
+			Value: network,
+		})
+		if err != nil {
+			return fmt.Errorf("unable to set network in "+
+				"metadata: %w", err)
+		}
+
+		// Read back whatever is stored. This is either the value we
+		// just inserted (first startup) or a value from a previous run.
+		storedNetwork, err := tx.GetMetaValue(ctx, metadataNetworkKey)
+		if err != nil {
+			return fmt.Errorf("unable to read network from "+
+				"metadata: %w", err)
+		}
+
+		if storedNetwork != network {
+			return fmt.Errorf("database network mismatch: the "+
+				"database was previously used with network "+
+				"'%s', but lnd is now configured for network "+
+				"'%s'. To fix this, either point lnd at a "+
+				"different database or reconfigure lnd to use "+
+				"network '%s'",
+				storedNetwork, network, storedNetwork)
+		}
+
+		return nil
+	}, func() {})
+}
+
 // GetSchemaVersion returns the current schema version of the Postgres database.
 func (s *PostgresStore) GetSchemaVersion() (int, bool, error) {
 	driver, err := pgx_migrate.WithInstance(s.DB, &pgx_migrate.Config{})

sqldb/sqlite.go

@@ -158,6 +158,17 @@ func (s *SqliteStore) GetBaseDB() *BaseDB {
 	return s.BaseDB
 }
 
+// ValidateNetwork checks that the network stored in the metadata table matches
+// the provided network name. On the first call the network is persisted so
+// that subsequent restarts can detect an accidental network switch.
+//
+// NOTE: This is part of the sqldb.DB interface.
+func (s *SqliteStore) ValidateNetwork(ctx context.Context,
+	network string) error {
+
+	return s.BaseDB.ValidateNetwork(ctx, network)
+}
+
 // ApplyAllMigrations applies both the SQLC and custom in-code migrations to the
 // SQLite database.
 func (s *SqliteStore) ApplyAllMigrations(ctx context.Context,