Make all messages sent between the client and server fixed size.

This is the first of two changes to make the protocol more resilient and less
sensitive to other changes in the code, particularly with commands. The client
now packs argv into a buffer and sends it to the server for parsing, rather
than doing it itself and sending the parsed command data.

As a side-effect this also removes a lot of now-unused command marshalling
code.

Mixing a server without this change and a client with or vice versa will cause
tmux to hang or crash, please ensure that tmux is entirely killed before
upgrading.

1 files changed, 33 insertions, 25 deletions

diff --git a/tmux.h b/tmux.h
index 2eeb9f5d..159711e7 100644
--- a/tmux.h
+++ b/tmux.h
@@ -19,7 +19,7 @@
 #ifndef TMUX_H
 #define TMUX_H
 
-#define PROTOCOL_VERSION -14
+#define PROTOCOL_VERSION -15
 
 #include <sys/param.h>
 #include <sys/time.h>
@@ -62,6 +62,14 @@ extern char    *__progname;
 /* Maximum poll timeout (when attached). */
 #define POLL_TIMEOUT 50
 
+/*
+ * Maximum sizes of strings in message data. Don't forget to bump
+ * PROTOCOL_VERSION if any of these change!
+ */
+#define COMMAND_LENGTH 2048	/* packed argv size */
+#define TERMINAL_LENGTH 128	/* length of TERM environment variable */
+#define PRINT_LENGTH 512	/* printed error/message size */
+
 /* Fatal errors. */
 #define fatal(msg) log_fatal("%s: %s", __func__, msg);
 #define fatalx(msg) log_fatalx("%s: %s", __func__, msg);
@@ -293,17 +301,29 @@ enum hdrtype {
 	MSG_WAKEUP,
 };
 
-/* Message header structure. */
+/*
+ * Message header and data. 
+ *
+ * Don't forget to bump PROTOCOL_VERSION if any of these change!
+ *
+ * Changing sizeof (struct hdr) or sizeof (struct msg_identify_data) will make
+ * the tmux client hang even if the protocol version is bumped.
+ */
 struct hdr {
 	enum hdrtype	type;
 	size_t		size;
 };
 
+struct msg_print_data {
+	char		msg[PRINT_LENGTH];
+};
+
 struct msg_command_data {
 	pid_t		pid;			/* pid from $TMUX or -1 */
 	u_int		idx;			/* index from $TMUX */
 
-	size_t		namelen;
+	int		argc;
+	char		argv[COMMAND_LENGTH];
 };
 
 struct msg_identify_data {
@@ -312,6 +332,8 @@ struct msg_identify_data {
 
 	char		cwd[MAXPATHLEN];
 
+	char		term[TERMINAL_LENGTH];
+
 #define IDENTIFY_UTF8 0x1
 #define IDENTIFY_256COLOURS 0x2
 #define IDENTIFY_88COLOURS 0x4
@@ -320,8 +342,6 @@ struct msg_identify_data {
 
 	u_int		sx;
 	u_int		sy;
-
-	size_t		termlen;
 };
 
 struct msg_resize_data {
@@ -329,6 +349,10 @@ struct msg_resize_data {
 	u_int		sy;
 };
 
+struct msg_unlock_data {
+	char	       	pass[PASS_MAX];
+};
+
 /* Editing keys. */
 enum mode_key_cmd {
 	MODEKEYCMD_BACKSPACE = 0x1000,
@@ -907,8 +931,6 @@ struct cmd_entry {
 	void		 (*init)(struct cmd *, int);
 	int		 (*parse)(struct cmd *, int, char **, char **);
 	int		 (*exec)(struct cmd *, struct cmd_ctx *);
-	void		 (*send)(struct cmd *, struct buffer *);
-	void	         (*recv)(struct cmd *, struct buffer *);
 	void		 (*free)(struct cmd *);
 	size_t 		 (*print)(struct cmd *, char *, size_t);
 };
@@ -1113,14 +1135,13 @@ int		 paste_replace(struct paste_stack *, u_int, char *);
 void		 clock_draw(struct screen_write_ctx *, u_int, int);
 
 /* cmd.c */
+int		 cmd_pack_argv(int, char **, char *, size_t);
+int		 cmd_unpack_argv(char *, size_t, int, char ***);
+void		 cmd_free_argv(int, char **);
 struct cmd	*cmd_parse(int, char **, char **);
 int		 cmd_exec(struct cmd *, struct cmd_ctx *);
-void		 cmd_send(struct cmd *, struct buffer *);
-struct cmd	*cmd_recv(struct buffer *);
 void		 cmd_free(struct cmd *);
 size_t		 cmd_print(struct cmd *, char *, size_t);
-void		 cmd_send_string(struct buffer *, const char *);
-char		*cmd_recv_string(struct buffer *);
 struct session	*cmd_current_session(struct cmd_ctx *);
 struct client	*cmd_find_client(struct cmd_ctx *, const char *);
 struct session	*cmd_find_session(struct cmd_ctx *, const char *);
@@ -1205,8 +1226,6 @@ extern const struct cmd_entry cmd_up_pane_entry;
 /* cmd-list.c */
 struct cmd_list	*cmd_list_parse(int, char **, char **);
 int		 cmd_list_exec(struct cmd_list *, struct cmd_ctx *);
-void		 cmd_list_send(struct cmd_list *, struct buffer *);
-struct cmd_list	*cmd_list_recv(struct buffer *);
 void		 cmd_list_free(struct cmd_list *);
 size_t		 cmd_list_print(struct cmd_list *, char *, size_t);
 
@@ -1220,8 +1239,6 @@ size_t  cmd_prarg(char *, size_t, const char *, char *);
 #define CMD_TARGET_CLIENT_USAGE "[-t target-client]"
 void	cmd_target_init(struct cmd *, int);
 int	cmd_target_parse(struct cmd *, int, char **, char **);
-void	cmd_target_send(struct cmd *, struct buffer *);
-void	cmd_target_recv(struct cmd *, struct buffer *);
 void	cmd_target_free(struct cmd *);
 size_t	cmd_target_print(struct cmd *, char *, size_t);
 #define CMD_SRCDST_WINDOW_USAGE "[-s src-window] [-t dst-window]"
@@ -1229,8 +1246,6 @@ size_t	cmd_target_print(struct cmd *, char *, size_t);
 #define CMD_SRCDST_CLIENT_USAGE "[-s src-client] [-t dst-client]"
 void	cmd_srcdst_init(struct cmd *, int);
 int	cmd_srcdst_parse(struct cmd *, int, char **, char **);
-void	cmd_srcdst_send(struct cmd *, struct buffer *);
-void	cmd_srcdst_recv(struct cmd *, struct buffer *);
 void	cmd_srcdst_free(struct cmd *);
 size_t	cmd_srcdst_print(struct cmd *, char *, size_t);
 #define CMD_BUFFER_WINDOW_USAGE "[-b buffer-index] [-t target-window]"
@@ -1238,8 +1253,6 @@ size_t	cmd_srcdst_print(struct cmd *, char *, size_t);
 #define CMD_BUFFER_CLIENT_USAGE "[-b buffer-index] [-t target-client]"
 void	cmd_buffer_init(struct cmd *, int);
 int	cmd_buffer_parse(struct cmd *, int, char **, char **);
-void	cmd_buffer_send(struct cmd *, struct buffer *);
-void	cmd_buffer_recv(struct cmd *, struct buffer *);
 void	cmd_buffer_free(struct cmd *);
 size_t	cmd_buffer_print(struct cmd *, char *, size_t);
 #define CMD_OPTION_WINDOW_USAGE "[-gu] [-t target-window] option [value]"
@@ -1247,8 +1260,6 @@ size_t	cmd_buffer_print(struct cmd *, char *, size_t);
 #define CMD_OPTION_CLIENT_USAGE "[-gu] [-t target-client] option [value]"
 void	cmd_option_init(struct cmd *, int);
 int	cmd_option_parse(struct cmd *, int, char **, char **);
-void	cmd_option_send(struct cmd *, struct buffer *);
-void	cmd_option_recv(struct cmd *, struct buffer *);
 void	cmd_option_free(struct cmd *);
 size_t	cmd_option_print(struct cmd *, char *, size_t);
 #define CMD_PANE_WINDOW_USAGE "[-t target-window] [-p pane-index]"
@@ -1256,8 +1267,6 @@ size_t	cmd_option_print(struct cmd *, char *, size_t);
 #define CMD_PANE_CLIENT_USAGE "[-t target-client] [-p pane-index]"
 void	cmd_pane_init(struct cmd *, int);
 int	cmd_pane_parse(struct cmd *, int, char **, char **);
-void	cmd_pane_send(struct cmd *, struct buffer *);
-void	cmd_pane_recv(struct cmd *, struct buffer *);
 void	cmd_pane_free(struct cmd *);
 size_t	cmd_pane_print(struct cmd *, char *, size_t);
 
@@ -1270,8 +1279,6 @@ int	 client_msg_dispatch(struct client_ctx *);
 
 /* client-fn.c */
 void	 client_write_server(struct client_ctx *, enum hdrtype, void *, size_t);
-void	 client_write_server2(
-    	     struct client_ctx *, enum hdrtype, void *, size_t, void *, size_t);
 void	 client_fill_session(struct msg_command_data *);
 
 /* key-bindings.c */
@@ -1303,6 +1310,7 @@ int	 server_msg_dispatch(struct client *);
 
 /* server-fn.c */
 const char **server_fill_environ(struct session *);
+void	 server_write_error(struct client *, const char *);
 void	 server_write_client(
              struct client *, enum hdrtype, const void *, size_t);
 void	 server_write_session(