add a sanity check to RPC input data size

reported by m31007

contrib/epee/include/net/http_protocol_handler.h

@@ -56,6 +56,7 @@ namespace net_utils
 			std::string m_folder;
 			std::vector<std::string> m_access_control_origins;
 			boost::optional<login> m_user;
+			size_t m_max_content_length{std::numeric_limits<size_t>::max()};
 			critical_section m_lock;
 		};
 
@@ -142,6 +143,7 @@ namespace net_utils
 			config_type& m_config;
 			bool m_want_close;
 			size_t m_newlines;
+			size_t m_bytes_read;
 		protected:
 			i_service_endpoint* m_psnd_hndlr; 
 			t_connection_context& m_conn_context;

contrib/epee/include/net/http_protocol_handler.inl

@@ -206,6 +206,7 @@ namespace net_utils
 		m_config(config),
 		m_want_close(false),
 		m_newlines(0),
+		m_bytes_read(0),
 		m_psnd_hndlr(psnd_hndlr),
 		m_conn_context(conn_context)
 	{
@@ -221,6 +222,7 @@ namespace net_utils
 		m_query_info.clear();
 		m_len_summary = 0;
 		m_newlines = 0;
+		m_bytes_read = 0;
 		return true;
 	}
 	//--------------------------------------------------------------------------------------------
@@ -243,6 +245,14 @@ namespace net_utils
 
 		size_t ndel;
 
+		m_bytes_read += buf.size();
+		if (m_bytes_read > m_config.m_max_content_length)
+		{
+			LOG_ERROR("simple_http_connection_handler::handle_buff_in: Too much data: got " << m_bytes_read);
+			m_state = http_state_error;
+			return false;
+		}
+
 		if(m_cache.size())
 			m_cache += buf;
 		else

src/cryptonote_config.h

@@ -126,6 +126,7 @@
 
 #define COMMAND_RPC_GET_BLOCKS_FAST_MAX_BLOCK_COUNT     1000
 #define COMMAND_RPC_GET_BLOCKS_FAST_MAX_TX_COUNT        20000
+#define MAX_RPC_CONTENT_LENGTH                          1048576 // 1 MB
 
 #define P2P_LOCAL_WHITE_PEERLIST_LIMIT                  1000
 #define P2P_LOCAL_GRAY_PEERLIST_LIMIT                   5000

src/rpc/core_rpc_server.cpp

@@ -344,6 +344,8 @@ namespace cryptonote
     if (m_rpc_payment)
       m_net_server.add_idle_handler([this](){ return m_rpc_payment->on_idle(); }, 60 * 1000);
 
+    m_net_server.get_config_object().m_max_content_length = MAX_RPC_CONTENT_LENGTH;
+
     auto rng = [](size_t len, uint8_t *ptr){ return crypto::rand(len, ptr); };
     return epee::http_server_impl_base<core_rpc_server, connection_context>::init(
       rng, std::move(port), std::move(bind_ip_str),