Reject abandoned chain anchor hashes

cmd/config/config.go

@@ -51,7 +51,13 @@ func validateHarmonyConfig(config harmonyconfig.HarmonyConfig) error {
 		return fmt.Errorf("flag --run.offline must have p2p IP be %v", nodeconfig.DefaultLocalListenIP)
 	}
 
-	if !config.Sync.Client && !config.DNSSync.Client {
+	// Recovery maintenance must be able to open a stopped database without
+	// starting either downloader. The mainnet validator exception is paired
+	// with a fail-closed runtime checkpoint/sync guard in cmd/harmony.
+	recoveryValidator := config.Network.NetworkType == nodeconfig.Mainnet &&
+		config.General.NodeType == NodeTypeValidator
+	if !config.Sync.Client && !config.DNSSync.Client &&
+		!config.General.IsOffline && !recoveryValidator {
 		// There is no module up for sync
 		return errors.New("either --sync.client or --sync.legacy.client shall be enabled")
 	}

cmd/config/recovery_config_test.go

@@ -0,0 +1,27 @@
+package config
+
+import (
+	"testing"
+
+	nodeconfig "github.com/harmony-one/harmony/internal/configs/node"
+	"github.com/stretchr/testify/require"
+)
+
+func TestRecoveryConfigAllowsNoSyncClientOnlyInNarrowCases(t *testing.T) {
+	offline := GetDefaultHmyConfigCopy(nodeconfig.Mainnet)
+	offline.General.IsOffline = true
+	offline.P2P.IP = nodeconfig.DefaultLocalListenIP
+	offline.Sync.Client = false
+	offline.DNSSync.Client = false
+	require.NoError(t, validateHarmonyConfig(offline))
+
+	recoveryValidator := GetDefaultHmyConfigCopy(nodeconfig.Mainnet)
+	recoveryValidator.Sync.Client = false
+	recoveryValidator.DNSSync.Client = false
+	require.NoError(t, validateHarmonyConfig(recoveryValidator))
+
+	testnet := GetDefaultHmyConfigCopy(nodeconfig.Testnet)
+	testnet.Sync.Client = false
+	testnet.DNSSync.Client = false
+	require.Error(t, validateHarmonyConfig(testnet))
+}