Reject unknown config options

Fail TOML parsing when unsupported config keys are present so typos do
not get silently ignored. Keep the LSPS2 service section typed in all
builds, while default builds still parse and ignore it unless the
experimental feature is enabled.

Author: benthecarman

ldk-server/src/util/config.rs

@@ -460,6 +460,7 @@ impl ConfigBuilder {
 
 /// Configuration loaded from a TOML file.
 #[derive(Deserialize, Serialize)]
+#[serde(deny_unknown_fields)]
 pub struct TomlConfig {
 	node: Option<NodeConfig>,
 	storage: Option<StorageConfig>,
@@ -475,6 +476,7 @@ pub struct TomlConfig {
 }
 
 #[derive(Deserialize, Serialize)]
+#[serde(deny_unknown_fields)]
 struct NodeConfig {
 	network: Option<Network>,
 	listening_addresses: Option<Vec<String>>,
@@ -487,46 +489,54 @@ struct NodeConfig {
 }
 
 #[derive(Deserialize, Serialize)]
+#[serde(deny_unknown_fields)]
 struct StorageConfig {
 	disk: Option<DiskConfig>,
 }
 
 #[derive(Deserialize, Serialize)]
+#[serde(deny_unknown_fields)]
 struct DiskConfig {
 	dir_path: Option<String>,
 }
 
 #[derive(Deserialize, Serialize)]
+#[serde(deny_unknown_fields)]
 struct BitcoindConfig {
 	rpc_address: Option<String>,
 	rpc_user: Option<String>,
 	rpc_password: Option<String>,
 }
 
 #[derive(Deserialize, Serialize)]
+#[serde(deny_unknown_fields)]
 struct ElectrumConfig {
 	server_url: String,
 }
 
 #[derive(Deserialize, Serialize)]
+#[serde(deny_unknown_fields)]
 struct EsploraConfig {
 	server_url: String,
 }
 
 #[derive(Deserialize, Serialize)]
+#[serde(deny_unknown_fields)]
 struct LogConfig {
 	level: Option<String>,
 	file: Option<String>,
 }
 
 #[derive(Deserialize, Serialize)]
+#[serde(deny_unknown_fields)]
 struct TomlTlsConfig {
 	cert_path: Option<String>,
 	key_path: Option<String>,
 	hosts: Option<Vec<String>>,
 }
 
 #[derive(Deserialize, Serialize)]
+#[serde(deny_unknown_fields)]
 struct MetricsTomlConfig {
 	enabled: Option<bool>,
 	poll_metrics_interval: Option<u64>,
@@ -535,11 +545,13 @@ struct MetricsTomlConfig {
 }
 
 #[derive(Deserialize, Serialize)]
+#[serde(deny_unknown_fields)]
 struct TomlTorConfig {
 	proxy_address: String,
 }
 
 #[derive(Deserialize, Serialize)]
+#[serde(deny_unknown_fields)]
 struct HrnTomlConfig {
 	mode: Option<String>,
 	dns_server_address: Option<String>,
@@ -645,19 +657,22 @@ fn parse_async_payments_role(role: &str) -> io::Result<AsyncPaymentsRole> {
 }
 
 #[derive(Deserialize, Serialize)]
+#[serde(deny_unknown_fields)]
 struct LiquidityConfig {
 	lsps2_client: Option<LSPSClientTomlConfig>,
 	lsps2_service: Option<LSPS2ServiceTomlConfig>,
 }
 
 #[derive(Deserialize, Serialize, Debug)]
+#[serde(deny_unknown_fields)]
 struct LSPSClientTomlConfig {
 	node_pubkey: String,
 	address: String,
 	token: Option<String>,
 }
 
 #[derive(Deserialize, Serialize, Debug)]
+#[serde(deny_unknown_fields)]
 struct LSPS2ServiceTomlConfig {
 	advertise_service: bool,
 	channel_opening_fee_ppm: u32,
@@ -1343,6 +1358,73 @@ mod tests {
 		validate_missing!("network =", missing_field_msg("network"));
 	}
 
+	#[test]
+	fn test_config_unknown_fields_in_file() {
+		let storage_path = std::env::temp_dir();
+		let config_file_name = "test_config_unknown_fields_in_file.toml";
+
+		let mut args_config = empty_args_config();
+		args_config.config_file =
+			Some(storage_path.join(config_file_name).to_string_lossy().to_string());
+
+		fs::write(
+			storage_path.join(config_file_name),
+			format!("{}\n[unknown]\noption = true\n", DEFAULT_CONFIG),
+		)
+		.unwrap();
+		let err = load_config(&args_config).unwrap_err();
+		assert_eq!(err.kind(), io::ErrorKind::InvalidData);
+		assert!(err.to_string().contains("unknown field `unknown`"));
+
+		fs::write(
+			storage_path.join(config_file_name),
+			DEFAULT_CONFIG
+				.replace("network = \"regtest\"", "network = \"regtest\"\nunknown = true"),
+		)
+		.unwrap();
+		let err = load_config(&args_config).unwrap_err();
+		assert_eq!(err.kind(), io::ErrorKind::InvalidData);
+		assert!(err.to_string().contains("unknown field `unknown`"));
+	}
+
+	#[test]
+	#[cfg(not(feature = "experimental-lsps2-support"))]
+	fn test_config_allows_unused_lsps2_service_config_without_feature() {
+		let storage_path = std::env::temp_dir();
+		let config_file_name =
+			"test_config_allows_unused_lsps2_service_config_without_feature.toml";
+
+		let mut args_config = empty_args_config();
+		args_config.config_file =
+			Some(storage_path.join(config_file_name).to_string_lossy().to_string());
+
+		let toml_config = r#"
+			[node]
+			network = "regtest"
+
+			[bitcoind]
+			rpc_address = "127.0.0.1:8332"
+			rpc_user = "bitcoind-testuser"
+			rpc_password = "bitcoind-testpassword"
+
+			[liquidity.lsps2_service]
+			advertise_service = false
+			channel_opening_fee_ppm = 1000
+			channel_over_provisioning_ppm = 500000
+			min_channel_opening_fee_msat = 10000000
+			min_channel_lifetime = 4320
+			max_client_to_self_delay = 1440
+			min_payment_size_msat = 10000000
+			max_payment_size_msat = 25000000000
+			client_trusts_lsp = true
+			disable_client_reserve = false
+			"#;
+
+		fs::write(storage_path.join(config_file_name), toml_config).unwrap();
+		let config = load_config(&args_config).unwrap();
+		assert!(config.lsps2_service_config.is_none());
+	}
+
 	fn remove_config_line(config: &str, key: &str) -> String {
 		config
 			.lines()