Implement platform specific input buffer flushing

Minecraft servers have a longstanding bug that omits newlines
when sending messages via RCON. This patch manually inserts
newlines to address the issue.

Reference: https://bugs.mojang.com/browse/MC-7569

Fixes #1

CHANGELOG.md

@@ -1,17 +1,21 @@
 #### Version history:
 
-###### 0.7.3
- - Add support to Valve style rcon authentication
+###### 0.8.0
+ - Implement support for multipacket responses
+ - Add support for Valve style rcon authentication
+ - Add experimental UTF-8 support for Windows
  - Change maximum packet size to correct value (4096 -> 4106)
+ - Attempt to add missing newlines in bugged Minecraft servers
+    * Implemented for responses to the 'help' command and unknown commands
  - Print auth failed message to stderr instead of stdout
  - Fail immediately if received packet size is out of spec
  - Return proper exit code from run_terminal_mode()
  - Add error messages to rcon_command() function
- 
+
 ###### 0.7.2
  - Quit gracefully when Ctrl-D or Ctrl+C is pressed
  - Remove "exit" and "quit" as quitting commands
-    * these are actual rcon commands on some servers
+    * These are actual rcon commands on some servers
  - Suppress compiler warning (strncpy)
  - Fix erroneous string length in packet building function
  - Fix typo in ANSI escape sequence for LCYAN

Makefile

@@ -15,7 +15,7 @@ RM = rm -v -f
 
 CC ?= gcc
 CFLAGS = -std=gnu99 -Wall -Wextra -Wpedantic -Wno-gnu-zero-variadic-macro-arguments -O2
-EXTRAFLAGS ?= -fstack-protector-all
+EXTRAFLAGS ?= -fstack-protector-strong -D_FORTIFY_SOURCE=2 -fPIE -pie -Wl,-z,relro -Wl,-z,now -fno-common
 
 ifeq ($(OS), Windows_NT)
 	LINKER = -lws2_32

mcrcon.1

@@ -1,7 +1,7 @@
 .\" Process this file with
 .\" groff -man -Tascii mcrcon.1
 .\"
-.TH MCRCON 1 "November 2024" "Version 0.7.3"
+.TH MCRCON 1 "December 2024" "Version 0.8.0"
 .SH NAME 
 mcrcon \- send rcon commands to a Minecraft server
 .SH SYNOPSIS

mcrcon.c

@@ -31,17 +31,20 @@
 #include <errno.h>
 #include <unistd.h>
 
-
 #ifdef _WIN32
 	#include <winsock2.h>
-    #include <windows.h>
-    #include <ws2tcpip.h>
+	#include <windows.h>
+	#include <ws2tcpip.h>
+	#include <fcntl.h>
+	#include <wchar.h>
 #else
-    #include <sys/socket.h>
-    #include <netdb.h>
+	#include <sys/socket.h>
+	#include <sys/select.h>
+	#include <netdb.h>
+	#include <termios.h>
 #endif
 
-#define VERSION "0.7.3"
+#define VERSION "0.8.0"
 #define IN_NAME "mcrcon"
 #define VER_STR IN_NAME" "VERSION" (built: "__DATE__" "__TIME__")"
 
@@ -56,19 +59,21 @@
 #define MAX_PACKET_SIZE		4106 // id (4) + cmd (4) + DATA_BUFFSIZE
 #define MIN_PACKET_SIZE		10   // id (4) + cmd (4) + two empty strings (2)
 
+#define MAX_WAIT_TIME 600
+
 #define log_error(fmt, ...) fprintf(stderr, fmt,  ##__VA_ARGS__);
 
 // rcon packet structure
 typedef struct {
-    int32_t size;
-    int32_t id;
-    int32_t cmd;
-    uint8_t data[DATA_BUFFSIZE];
-    // ignoring string2 for now
+	int32_t size;
+	int32_t id;
+	int32_t cmd;
+	uint8_t data[DATA_BUFFSIZE];
+	// ignoring string2 for now
 } rc_packet;
 
 // ===================================
-//  FUNCTION DEFINITIONS              
+//  FUNCTION DEFINITIONS
 // ===================================
 
 // Network related functions
@@ -95,20 +100,25 @@ void        packet_print(rc_packet *packet);
 bool        rcon_auth(int sock, char *passwd);
 int         rcon_command(int sock, char *command);
 
-
 // =============================================
 //  GLOBAL VARIABLES
 // =============================================
-static int flag_raw_output = 0;
-static int flag_silent_mode = 0;
-static int flag_disable_colors = 0;
-static int flag_wait_seconds = 0;
-static int global_connection_alive = 1;
-static int global_rsock;
+static int  flag_raw_output = 0;
+static int  flag_silent_mode = 0;
+static int  flag_disable_colors = 0;
+static int  flag_wait_seconds = 0;
+static int  global_connection_alive = 1;
+static bool global_valve_protocol = false;
+static bool global_minecraft_newline_fix = false;
+static int  global_rsock;
 
 #ifdef _WIN32
-  // console coloring on windows
-  HANDLE console_handle;
+// console coloring on windows
+HANDLE console_handle;
+
+// console code pages
+UINT old_output_codepage;
+UINT old_input_codepage;
 #endif
 
 // safety stuff (windows is still misbehaving)
@@ -116,6 +126,15 @@ void exit_proc(void)
 {
 	if (global_rsock != -1)
 		net_close(global_rsock);
+
+	#ifdef _WIN32
+	// Restore previous code pages
+	SetConsoleOutputCP(old_output_codepage);
+	SetConsoleCP(old_input_codepage);
+
+	// Set back to binary mode
+	_setmode(_fileno(stdin), _O_BINARY);
+	#endif
 }
 
 // TODO: check exact windows and linux behaviour
@@ -125,13 +144,9 @@ void sighandler(int sig)
 		putchar('\n');
 
 	global_connection_alive = 0;
-	#ifndef _WIN32
-	    exit(EXIT_SUCCESS);
-	#endif
+	exit(EXIT_SUCCESS);
 }
 
-#define MAX_WAIT_TIME 600
-
 unsigned int mcrcon_parse_seconds(char *str)
 {
 	char *end;
@@ -162,14 +177,10 @@ int main(int argc, char *argv[])
 	char *host = getenv("MCRCON_HOST");
 	char *pass = getenv("MCRCON_PASS");
 	char *port = getenv("MCRCON_PORT");
-	
+
 	if (!port) port = "25575";
 	if (!host) host = "localhost";
 
-	// disable output buffering (https://github.com/Tiiffi/mcrcon/pull/39)
-	setvbuf(stdout, NULL, _IONBF, 0);
-	setvbuf(stderr, NULL, _IONBF, 0);
-
 	if(argc < 1 && pass == NULL) usage();
 
 	// default getopt error handler enabled
@@ -188,7 +199,7 @@ int main(int argc, char *argv[])
 			case 'r': flag_raw_output = 1;           break;
 			case 'w':
 				flag_wait_seconds = mcrcon_parse_seconds(optarg);
-			break;
+				break;
 
 			case 'v':
 				puts(VER_STR);
@@ -219,10 +230,20 @@ int main(int argc, char *argv[])
 	signal(SIGINT, &sighandler);
 
 	#ifdef _WIN32
-		net_init_WSA();
-		console_handle = GetStdHandle(STD_OUTPUT_HANDLE);
-		if (console_handle == INVALID_HANDLE_VALUE)
-			console_handle = NULL;
+	net_init_WSA();
+	console_handle = GetStdHandle(STD_OUTPUT_HANDLE);
+	if (console_handle == INVALID_HANDLE_VALUE)
+		console_handle = NULL;
+
+	// Set the output and input code pages to utf-8
+	old_output_codepage = GetConsoleOutputCP();
+	old_input_codepage = GetConsoleCP();
+
+	SetConsoleOutputCP(CP_UTF8);
+	SetConsoleCP(CP_UTF8);
+
+	// Set the file translation mode to UTF16
+	_setmode(_fileno(stdin), _O_U16TEXT);
 	#endif
 
 	// open socket
@@ -273,8 +294,8 @@ void usage(void)
 	puts("Example:\n\t"IN_NAME" -H my.minecraft.server -p password -w 5 \"say Server is restarting!\" save-all stop\n");
 
 	#ifdef _WIN32
-	    puts("Press enter to exit.");
-	    getchar();
+	puts("Press enter to exit.");
+	getchar();
 	#endif
 
 	exit(EXIT_SUCCESS);
@@ -301,10 +322,10 @@ void net_init_WSA(void)
 void net_close(int sd)
 {
 	#ifdef _WIN32
-		closesocket(sd);
-		WSACleanup();
+	closesocket(sd);
+	WSACleanup();
 	#else
-		close(sd);
+	close(sd);
 	#endif
 }
 
@@ -323,16 +344,16 @@ int net_connect(const char *host, const char *port)
 	hints.ai_protocol = IPPROTO_TCP;
 
 	#ifdef _WIN32
-	  net_init_WSA();
+	net_init_WSA();
 	#endif
 
 	int ret = getaddrinfo(host, port, &hints, &server_info);
 	if (ret != 0) {
 		log_error("Name resolution failed.\n");
 		#ifdef _WIN32
-			log_error("Error %d: %s", ret, gai_strerror(ret));
+		log_error("Error %d: %s", ret, gai_strerror(ret));
 		#else
-			log_error("Error %d: %s\n", ret, gai_strerror(ret));
+		log_error("Error %d: %s\n", ret, gai_strerror(ret));
 		#endif
 
 		exit(EXIT_FAILURE);
@@ -358,7 +379,7 @@ int net_connect(const char *host, const char *port)
 		/* TODO (Tiiffi): Check why windows does not report errors */
 		log_error("Connection failed.\n");
 		#ifndef _WIN32
-			log_error("Error %d: %s\n", errno, strerror(errno));
+		log_error("Error %d: %s\n", errno, strerror(errno));
 		#endif
 
 		freeaddrinfo(server_info);
@@ -389,6 +410,9 @@ bool net_send_packet(int sd, rc_packet *packet)
 	return true;
 }
 
+
+// TODO: Fix the wonky behaviour when server quit/exit/stop/close
+//       command is issued. Client should close gracefully without errors.
 rc_packet *net_recv_packet(int sd)
 {
 	int32_t psize;
@@ -470,9 +494,9 @@ void print_color(int color)
 		else return;
 
 		#ifndef _WIN32
-			fputs(colors[color], stdout);
+		fputs(colors[color], stdout);
 		#else
-			SetConsoleTextAttribute(console_handle, color);
+		SetConsoleTextAttribute(console_handle, color);
 		#endif
 	}
 }
@@ -481,52 +505,67 @@ void print_color(int color)
 void packet_print(rc_packet *packet)
 {
 	uint8_t *data = packet->data;
+	int i;
 
 	if (flag_raw_output == 1) {
-		for (int i = 0; data[i] != 0; ++i) {
-			putchar(data[i]);
-		}
+		fputs((char *) data, stdout);
 		return;
 	}
 
-	int i;
+	// Newline fix for Minecraft
+	if (global_valve_protocol == false) {
+		const char test[] = "Unknown or incomplete command, see below for error";
+		size_t test_size = sizeof test - 1;
+		if (strncmp((char *) data, test, test_size) == 0) {
+			fwrite(data, test_size, 1, stdout);
+			putchar('\n');
+			data = &data[test_size];
+		}
+	}
+
 	int default_color = 0;
 
 	#ifdef _WIN32
-		CONSOLE_SCREEN_BUFFER_INFO console_info;
-		if (GetConsoleScreenBufferInfo(console_handle, &console_info) != 0) {
-			default_color = console_info.wAttributes + 0x30;
-		} else default_color = 0x37;
+	CONSOLE_SCREEN_BUFFER_INFO console_info;
+	if (GetConsoleScreenBufferInfo(console_handle, &console_info) != 0) {
+		default_color = console_info.wAttributes + 0x30;
+	}
+	else default_color = 0x37;
 	#endif
 
-	// colors enabled so try to handle the bukkit colors for terminal
-	if (flag_disable_colors == 0) {
-		for (i = 0; data[i] != 0; ++i) {
-			if (data[i] == 0x0A) print_color(default_color);
-			else if(data[i] == 0xc2 && data[i + 1] == 0xa7) {
-				i += 2;
+	bool slash = false;
+	bool colors_detected = false;
+
+	for (i = 0; data[i] != 0; ++i)
+	{
+		if (data[i] == 0x0A) {
+			print_color(default_color);
+		}
+		else if(data[i] == 0xc2 && data[i + 1] == 0xa7) {
+			// Disable new line fixes if Bukkit colors are detected
+			colors_detected = true;
+			i += 2;
+			if (flag_disable_colors == 0) {
 				print_color(data[i]);
-				continue;
 			}
-			putchar(data[i]);
+			continue;
 		}
-		print_color(default_color); // cancel coloring
-	}
-	// strip colors
-	else {
-		for (i = 0; data[i] != 0; ++i) {
-			if (data[i] == 0xc2 && data[i + 1] == 0xa7) {
-				i += 2;
-				continue;
-			}	
-			putchar(data[i]);
+
+		// Add missing newlines
+		if (colors_detected == false && global_minecraft_newline_fix && data[i] == '/') {
+			slash ? putchar('\n') : (slash = true);
 		}
+
+		putchar(data[i]);
 	}
+	print_color(default_color); // cancel coloring
 
 	// print newline if string has no newline
-	if (data[i - 1] != 10 && data[i - 1] != 13) {
+	if (data[i - 1] != '\n') {
 		putchar('\n');
 	}
+
+	fflush(stdout);
 }
 
 rc_packet *packet_build(int id, int cmd, char s[static 1])
@@ -564,7 +603,7 @@ bool rcon_auth(int sock, char *passwd)
 		return 0; // send failed
 	}
 
-receive:
+	receive:
 	packet = net_recv_packet(sock);
 	if (packet == NULL)
 		return 0;
@@ -573,6 +612,7 @@ receive:
 	 * so we have to check packet type and try again if necessary.
 	 */
 	if (packet->cmd != RCON_AUTH_RESPONSE) {
+		global_valve_protocol = true;
 		goto receive;
 	}
 
@@ -580,9 +620,11 @@ receive:
 	return packet->id == -1 ? false : true;
 }
 
-// TODO: Add proper error handling and reporting!
 int rcon_command(int sock, char *command)
 {
+	if (global_valve_protocol == false && strcasecmp(command, "help") == 0)
+		global_minecraft_newline_fix = true;
+
 	rc_packet *packet = packet_build(RCON_PID, RCON_EXEC_COMMAND, command);
 	if (packet == NULL) {
 		log_error("Error: packet build() failed!\n");
@@ -594,21 +636,60 @@ int rcon_command(int sock, char *command)
 		return 0;
 	}
 
-	packet = net_recv_packet(sock);
+	// Workaround to handle valve multipacket responses
+	// This one does not require using select()
+	packet = packet_build(0xBADA55, 0xBADA55, "");
 	if (packet == NULL) {
-		log_error("Error: net_recv_packet() failed!\n");
+		log_error("Error: packet build() failed!\n");
 		return 0;
 	}
 
-	if (packet->id != RCON_PID) {
-		log_error("Error: invalid packet id!\n");
+	if (!net_send_packet(sock, packet)) {
+		log_error("Error: net_send_packet() failed!\n");
 		return 0;
 	}
 
-	if (!flag_silent_mode) {
-		if (packet->size > 10)
-		packet_print(packet);
+	// initialize stuff for select()
+	fd_set read_fds;
+	FD_ZERO(&read_fds);
+	FD_SET(sock, &read_fds);
+
+	// Set 5 second timeout
+	struct timeval timeout = {0};
+	timeout.tv_sec = 5;
+	timeout.tv_usec = 0;
+
+	int incoming = 0;
+
+	do {
+		packet = net_recv_packet(sock);
+		if (packet == NULL) {
+			log_error("Error: net_recv_packet() failed!\n");
+			return 0;
+		}
+
+		// Check for packet id and multipacket guard id
+		if (packet->id != RCON_PID && packet->id != 0xBADA55) {
+			log_error("Error: invalid packet id!\n");
+			return 0;
+		}
+
+		if (packet->id == 0xBADA55) break;
+
+		if (flag_silent_mode == false) {
+			if (packet->size > 10)
+				packet_print(packet);
+		}
+
+		int result = select(sock + 1, &read_fds, NULL, NULL, &timeout);
+		if (result == -1) {
+			log_error("Error: select() failed!\n");
+			return 0;
+		}
+
+		incoming = (result > 0 && FD_ISSET(sock, &read_fds));
 	}
+	while(incoming);
 
 	return 1;
 }
@@ -628,9 +709,9 @@ int run_commands(int argc, char *argv[])
 
 		if (flag_wait_seconds > 0) {
 			#ifdef _WIN32
-				Sleep(flag_wait_seconds * 1000);
+			Sleep(flag_wait_seconds * 1000);
 			#else
-				sleep(flag_wait_seconds);
+			sleep(flag_wait_seconds);
 			#endif
 		}
 	}
@@ -641,15 +722,14 @@ int run_terminal_mode(int sock)
 {
 	char command[MAX_COMMAND_LENGTH] = {0};
 
-	puts("Logged in.\nType 'Q' or press Ctrl-D / Ctrl-C to disconnect.");
+	puts("Logged in. Press Ctrl-D or Ctrl-C to disconnect.");
 
 	while (global_connection_alive) {
 		putchar('>');
+		fflush(stdout);
 
 		int len = get_line(command, MAX_COMMAND_LENGTH);
-		if (len < 1) continue; 
-	
-		if (strcasecmp(command, "Q") == 0) break;
+		if (len < 1) continue;
 
 		if (len > 0 && global_connection_alive) {
 			if (!rcon_command(sock, command)) {
@@ -659,23 +739,81 @@ int run_terminal_mode(int sock)
 
 		/* Special case for "stop" command to prevent server-side bug.
 		 * https://bugs.mojang.com/browse/MC-154617
-		 * 
-		 * NOTE: This is hacky workaround which should be handled better to
-		 *       ensure compatibility with other servers using source RCON.
-		 * NOTE: strcasecmp() is POSIX function.
+		 *
+		 * NOTE: Not sure if this still a problem?!
 		 */
-		if (strcasecmp(command, "stop") == 0) {
-			break;
+		if (global_valve_protocol == false && strcasecmp(command, "stop") == 0) {
+			// Timeout to before checking if connection was closed
+			#ifdef _WIN32
+			Sleep(2 * 1000);
+			#else
+			sleep(2);
+			#endif
+
+			char tmp[1];
+			#ifdef _WIN32
+			// TODO: More Windows side testing!
+			int result = recv(sock, tmp, sizeof(tmp), MSG_PEEK | 0);
+			#else
+			int result = recv(sock, tmp, sizeof(tmp), MSG_PEEK | MSG_DONTWAIT);
+			#endif
+			if (result == 0) {
+				break; // Connection closed
+			}
+			// TODO: Check for return values and errors!
 		}
 	}
 
 	return EXIT_SUCCESS;
 }
 
+#ifdef _WIN32
+char *utf8_getline(char *buf, int size, FILE *stream)
+{
+	// Widechar fgets
+	wchar_t in[MAX_COMMAND_LENGTH] = {0};
+
+	wchar_t *result = fgetws(in, MAX_COMMAND_LENGTH, stream);
+	if (result == NULL) {
+		return NULL;
+	}
+
+	// Calculates UTF-8 buffer size
+	int required_size = WideCharToMultiByte(CP_UTF8, 0, in, -1, NULL, 0, NULL, NULL);
+	if (size < required_size) {
+		// TODO: Proper error handling & reporting
+		return NULL;
+	}
+
+	if (WideCharToMultiByte(CP_UTF8, 0, in, -1, buf, size, NULL, NULL) == 0) {
+		// TODO: Proper error handling & reporting
+		return NULL;
+	}
+
+	return buf;
+}
+#endif
+
+void flush_input(void)
+{
+	#ifdef _WIN32
+	FlushConsoleInputBuffer(console_handle);
+	#else
+	tcflush(STDIN_FILENO, TCIFLUSH);
+	#endif
+}
+
 // gets line from stdin and deals with rubbish left in the input buffer
 int get_line(char *buffer, int bsize)
 {
+	#ifdef _WIN32
+	char *ret = utf8_getline(buffer, bsize, stdin);
+	#else
 	char *ret = fgets(buffer, bsize, stdin);
+	#endif
+
+	flush_input();
+
 	if (ret == NULL) {
 		if (ferror(stdin)) {
 			log_error("Error %d: %s\n", errno, strerror(errno));
@@ -687,14 +825,17 @@ int get_line(char *buffer, int bsize)
 
 	// remove unwanted characters from the buffer
 	buffer[strcspn(buffer, "\r\n")] = '\0';
-
 	int len = strlen(buffer);
 
-	// clean input buffer if needed 
+#if 0
+	// clean input buffer if needed
+	#ifndef _WIN32
 	if (len == bsize - 1) {
 		int ch;
 		while ((ch = getchar()) != '\n' && ch != EOF);
 	}
+	#endif
+#endif
 
 	return len;
 }