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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.

/* $OpenBSD: server-msg.c,v 1.7 2009/07/26 12:58:44 nicm Exp $ */

/*
 * Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
 * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <sys/types.h>

#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include "tmux.h"

void	server_msg_fn_command(struct hdr *, struct client *);
void	server_msg_fn_identify(struct hdr *, struct client *);
void	server_msg_fn_resize(struct hdr *, struct client *);
void	server_msg_fn_exiting(struct hdr *, struct client *);
void	server_msg_fn_unlock(struct hdr *, struct client *);
void	server_msg_fn_wakeup(struct hdr *, struct client *);

void printflike2 server_msg_fn_command_error(
    	    struct cmd_ctx *, const char *, ...);
void printflike2 server_msg_fn_command_print(
    	    struct cmd_ctx *, const char *, ...);
void printflike2 server_msg_fn_command_info(
    	    struct cmd_ctx *, const char *, ...);

struct server_msg {
	enum hdrtype	type;
	void	        (*fn)(struct hdr *, struct client *);
};
const struct server_msg server_msg_table[] = {
	{ MSG_IDENTIFY, server_msg_fn_identify },
	{ MSG_COMMAND, server_msg_fn_command },
	{ MSG_RESIZE, server_msg_fn_resize },
	{ MSG_EXITING, server_msg_fn_exiting },
	{ MSG_UNLOCK, server_msg_fn_unlock },
	{ MSG_WAKEUP, server_msg_fn_wakeup },
};

int
server_msg_dispatch(struct client *c)
{
	struct hdr		 hdr;
	const struct server_msg	*msg;
	u_int		 	 i;

	for (;;) {
		if (BUFFER_USED(c->in) < sizeof hdr)
			return (0);
		memcpy(&hdr, BUFFER_OUT(c->in), sizeof hdr);
		if (BUFFER_USED(c->in) < (sizeof hdr) + hdr.size)
			return (0);
		buffer_remove(c->in, sizeof hdr);

		for (i = 0; i < nitems(server_msg_table); i++) {
			msg = server_msg_table + i;
			if (msg->type == hdr.type) {
				msg->fn(&hdr, c);
				break;
			}
		}
		if (i == nitems(server_msg_table))
			fatalx("unexpected message");
	}
}

void printflike2
server_msg_fn_command_error(struct cmd_ctx *ctx, const char *fmt, ...)
{
	struct msg_print_data	data;
	va_list			ap;

	va_start(ap, fmt);
	xvsnprintf(data.msg, sizeof data.msg, fmt, ap);
	va_end(ap);

	server_write_client(ctx->cmdclient, MSG_ERROR, &data, sizeof data);
}

void printflike2
server_msg_fn_command_print(struct cmd_ctx *ctx, const char *fmt, ...)
{
	struct msg_print_data	data;
	va_list			ap;

	va_start(ap, fmt);
	xvsnprintf(data.msg, sizeof data.msg, fmt, ap);
	va_end(ap);

	server_write_client(ctx->cmdclient, MSG_PRINT, &data, sizeof data);
}

void printflike2
server_msg_fn_command_info(struct cmd_ctx *ctx, const char *fmt, ...)
{
	struct msg_print_data	data;
	va_list			ap;

	if (be_quiet)
		return;

	va_start(ap, fmt);
	xvsnprintf(data.msg, sizeof data.msg, fmt, ap);
	va_end(ap);

	server_write_client(ctx->cmdclient, MSG_PRINT, &data, sizeof data);
}

void
server_msg_fn_command(struct hdr *hdr, struct client *c)
{
	struct msg_command_data	data;
	struct cmd_ctx	 	ctx;
	struct cmd_list	       *cmdlist = NULL;
	struct cmd	       *cmd;
	int			argc;
	char		      **argv, *cause;

	if (hdr->size < sizeof data)
		fatalx("bad MSG_COMMAND size");
	buffer_read(c->in, &data, sizeof data);

	server_activity = time(NULL);

	ctx.error = server_msg_fn_command_error;
	ctx.print = server_msg_fn_command_print;
	ctx.info = server_msg_fn_command_info;

	ctx.msgdata = &data;
	ctx.curclient = NULL;
	ctx.cursession = NULL;

	ctx.cmdclient = c;

	argc = data.argc;
	data.argv[(sizeof data.argv) - 1] = '\0';
	if (cmd_unpack_argv(data.argv, sizeof data.argv, argc, &argv) != 0) {
		server_msg_fn_command_error(&ctx, "command too long");
		goto error;
	}

	if (argc == 0) {
		argc = 1;
		argv = xcalloc(1, sizeof *argv);
		*argv = xstrdup("new-session");
	}

	if ((cmdlist = cmd_list_parse(argc, argv, &cause)) == NULL) {
		server_msg_fn_command_error(&ctx, "%s", cause);
		cmd_free_argv(argc, argv);
		goto error;
	}
	cmd_free_argv(argc, argv);

	if (data.pid != -1) {
		TAILQ_FOREACH(cmd, cmdlist, qentry) {
			if (cmd->entry->flags & CMD_CANTNEST) {
				server_msg_fn_command_error(&ctx,
				    "sessions should be nested with care. "
				    "unset $TMUX to force");
				goto error;
			}
		}
	}

	if (cmd_list_exec(cmdlist, &ctx) != 1)
		server_write_client(c, MSG_EXIT, NULL, 0);
	cmd_list_free(cmdlist);
	return;

error:
	if (cmdlist != NULL)
		cmd_list_free(cmdlist);
	server_write_client(c, MSG_EXIT, NULL, 0);
}

void
server_msg_fn_identify(struct hdr *hdr, struct client *c)
{
	struct msg_identify_data	data;

	if (hdr->size < sizeof data)
		fatalx("bad MSG_IDENTIFY size");
	buffer_read(c->in, &data, sizeof data);

	log_debug("identify msg from client: %u,%u (%d)",
	    data.sx, data.sy, data.version);

	if (data.version != PROTOCOL_VERSION) {
		server_write_error(c, "protocol version mismatch");
		return;
	}

	c->tty.sx = data.sx;
	c->tty.sy = data.sy;

	c->cwd = NULL;
	data.cwd[(sizeof data.cwd) - 1] = '\0';
	if (*data.cwd != '\0')
		c->cwd = xstrdup(data.cwd);

	data.tty[(sizeof data.tty) - 1] = '\0';
	data.term[(sizeof data.term) - 1] = '\0';
	tty_init(&c->tty, data.tty, data.term);
	if (data.flags & IDENTIFY_UTF8)
		c->tty.flags |= TTY_UTF8;
	if (data.flags & IDENTIFY_256COLOURS)
		c->tty.term_flags |= TERM_256COLOURS;
	else if (data.flags & IDENTIFY_88COLOURS)
		c->tty.term_flags |= TERM_88COLOURS;
	if (data.flags & IDENTIFY_HASDEFAULTS)
		c->tty.term_flags |= TERM_HASDEFAULTS;

	c->flags |= CLIENT_TERMINAL;
}

void
server_msg_fn_resize(struct hdr *hdr, struct client *c)
{
	struct msg_resize_data	data;

	if (hdr->size != sizeof data)
		fatalx("bad MSG_RESIZE size");
	buffer_read(c->in, &data, sizeof data);

	log_debug("resize msg from client: %u,%u", data.sx, data.sy);

	c->tty.sx = data.sx;
	if (c->tty.sx == 0)
		c->tty.sx = 80;
	c->tty.sy = data.sy;
	if (c->tty.sy == 0)
		c->tty.sy = 25;

	c->tty.cx = UINT_MAX;
	c->tty.cy = UINT_MAX;
	c->tty.rupper = UINT_MAX;
	c->tty.rlower = UINT_MAX;

	recalculate_sizes();

	/* Always redraw this client. */
	server_redraw_client(c);
}

void
server_msg_fn_exiting(struct hdr *hdr, struct client *c)
{
	if (hdr->size != 0)
		fatalx("bad MSG_EXITING size");

	log_debug("exiting msg from client");

	c->session = NULL;

	tty_close(&c->tty, c->flags & CLIENT_SUSPENDED);

	server_write_client(c, MSG_EXITED, NULL, 0);
}

void
server_msg_fn_unlock(struct hdr *hdr, struct client *c)
{
	struct msg_unlock_data	data;

	if (hdr->size != sizeof data)
		fatalx("bad MSG_UNLOCK size");
	buffer_read(c->in, &data, sizeof data);

	log_debug("unlock msg from client");

	data.pass[(sizeof data.pass) - 1] = '\0';
	if (server_unlock(data.pass) != 0)
		server_write_error(c, "bad password");
	memset(&data, 0, sizeof data);

	server_write_client(c, MSG_EXIT, NULL, 0);
}

void
server_msg_fn_wakeup(struct hdr *hdr, struct client *c)
{
	if (hdr->size != 0)
		fatalx("bad MSG_WAKEUP size");

	log_debug("wakeup msg from client");

	c->flags &= ~CLIENT_SUSPENDED;
	tty_start_tty(&c->tty);
	server_redraw_client(c);
}