Add difficulty limit for RPC "work_generate" in config.json

nano/core_test/rpc.cpp

@@ -2103,6 +2103,17 @@ TEST (rpc, work_generate_difficulty)
 	uint64_t result_difficulty2;
 	ASSERT_FALSE (nano::work_validate (hash1, work2, &result_difficulty2));
 	ASSERT_GE (result_difficulty2, difficulty2);
+	uint64_t difficulty3 (rpc.config.max_work_generate_difficulty + 1);
+	request1.put ("difficulty", nano::to_string_hex (difficulty3));
+	test_response response3 (request1, rpc, system.io_ctx);
+	system.deadline_set (5s);
+	while (response3.status == 0)
+	{
+		ASSERT_NO_ERROR (system.poll ());
+	}
+	ASSERT_EQ (200, response3.status);
+	std::error_code ec (nano::error_rpc::difficulty_limit);
+	ASSERT_EQ (response3.json.get<std::string> ("error"), ec.message ());
 }
 
 TEST (rpc, work_cancel)

nano/lib/errors.cpp

@@ -148,6 +148,8 @@ std::string nano::error_rpc_messages::message (int ev) const
 			return "Destination account, previous hash, current balance and amount required";
 		case nano::error_rpc::confirmation_not_found:
 			return "Active confirmation not found";
+		case nano::error_rpc::difficulty_limit:
+			return "Difficulty above config limit";
 		case nano::error_rpc::invalid_balance:
 			return "Invalid balance number";
 		case nano::error_rpc::invalid_destinations:

nano/lib/errors.hpp

@@ -90,6 +90,7 @@ enum class error_rpc
 	block_create_requirements_change,
 	block_create_requirements_send,
 	confirmation_not_found,
+	difficulty_limit,
 	invalid_balance,
 	invalid_destinations,
 	invalid_offset,

nano/node/rpc.cpp

@@ -4227,6 +4227,10 @@ void nano::rpc_handler::work_generate ()
 			ec = nano::error_rpc::bad_difficulty_format;
 		}
 	}
+	if (!ec && difficulty > rpc.config.max_work_generate_difficulty)
+	{
+		ec = nano::error_rpc::difficulty_limit;
+	}
 	if (!ec)
 	{
 		bool use_peers (request.get_optional<bool> ("use_peers") == true);

nano/node/rpcconfig.cpp

@@ -38,7 +38,8 @@ port (network_params.default_rpc_port),
 enable_control (enable_control_a),
 max_json_depth (20),
 enable_sign_hash (false),
-max_request_size (32 * 1024 * 1024)
+max_request_size (32 * 1024 * 1024),
+max_work_generate_difficulty (0xffffffffc0000000)
 {
 }
 
@@ -51,6 +52,7 @@ nano::error nano::rpc_config::serialize_json (nano::jsonconfig & json) const
 	json.put ("max_json_depth", max_json_depth);
 	json.put ("enable_sign_hash", enable_sign_hash);
 	json.put ("max_request_size", max_request_size);
+	json.put ("max_work_generate_difficulty", nano::to_string_hex (max_work_generate_difficulty));
 	return json.get_error ();
 }
 
@@ -62,6 +64,7 @@ nano::error nano::rpc_config::deserialize_json (bool & upgraded_a, nano::jsoncon
 		version_l = 1;
 		json.put ("version", *version_l);
 		json.put ("max_request_size", max_request_size);
+		json.put ("max_work_generate_difficulty", nano::to_string_hex (max_work_generate_difficulty));
 		json.erase ("frontier_request_limit");
 		json.erase ("chain_request_limit");
 
@@ -80,5 +83,11 @@ nano::error nano::rpc_config::deserialize_json (bool & upgraded_a, nano::jsoncon
 	json.get_optional<uint8_t> ("max_json_depth", max_json_depth);
 	json.get_optional<bool> ("enable_sign_hash", enable_sign_hash);
 	json.get_optional<uint64_t> ("max_request_size", max_request_size);
+	std::string max_work_generate_difficulty_text;
+	json.get_optional<std::string> ("max_work_generate_difficulty", max_work_generate_difficulty_text);
+	if (!max_work_generate_difficulty_text.empty ())
+	{
+		nano::from_string_hex (max_work_generate_difficulty_text, max_work_generate_difficulty);
+	}
 	return json.get_error ();
 }

nano/node/rpcconfig.hpp

@@ -46,6 +46,7 @@ class rpc_config
 	uint8_t max_json_depth;
 	bool enable_sign_hash;
 	uint64_t max_request_size;
+	uint64_t max_work_generate_difficulty;
 	static int json_version ()
 	{
 		return 1;