Return to client.c CVS log

Up to [local] / src / usr.bin / tmux

Because pledge(2) does not allow us to pass directory file descriptors
around, we can't use file descriptors for the working directory because
we will be unable to pass it to a privileged process to tell it where to
read or write files or spawn children. So move tmux back to using
strings for the current working directory. We try to check it exists
with access() when it is set but ultimately fall back to ~ if it fails
at time of use (or / if that fails too).

/* $OpenBSD: client.c,v 1.102 2015/10/31 08:13:58 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 <sys/file.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/un.h>
#include <sys/wait.h>

#include <errno.h>
#include <event.h>
#include <fcntl.h>
#include <imsg.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "tmux.h"

struct tmuxproc	*client_proc;
struct tmuxpeer	*client_peer;
int		 client_flags;
struct event	 client_stdin;
enum {
	CLIENT_EXIT_NONE,
	CLIENT_EXIT_DETACHED,
	CLIENT_EXIT_DETACHED_HUP,
	CLIENT_EXIT_LOST_TTY,
	CLIENT_EXIT_TERMINATED,
	CLIENT_EXIT_LOST_SERVER,
	CLIENT_EXIT_EXITED,
	CLIENT_EXIT_SERVER_EXITED,
} client_exitreason = CLIENT_EXIT_NONE;
int		 client_exitval;
enum msgtype	 client_exittype;
const char	*client_exitsession;
int		 client_attached;

__dead void	client_exec(const char *);
int		client_get_lock(char *);
int		client_connect(struct event_base *, char *, int);
void		client_send_identify(const char *, const char *);
void		client_stdin_callback(int, short, void *);
void		client_write(int, const char *, size_t);
void		client_signal(int);
void		client_dispatch(struct imsg *, void *);
void		client_dispatch_attached(struct imsg *);
void		client_dispatch_wait(struct imsg *);
const char     *client_exit_message(void);

/*
 * Get server create lock. If already held then server start is happening in
 * another client, so block until the lock is released and return -1 to
 * retry. Ignore other errors - just continue and start the server without the
 * lock.
 */
int
client_get_lock(char *lockfile)
{
	int lockfd;

	if ((lockfd = open(lockfile, O_WRONLY|O_CREAT, 0600)) == -1)
		fatal("open failed");
	log_debug("lock file is %s", lockfile);

	if (flock(lockfd, LOCK_EX|LOCK_NB) == -1) {
		log_debug("flock failed: %s", strerror(errno));
		if (errno != EAGAIN)
			return (lockfd);
		while (flock(lockfd, LOCK_EX) == -1 && errno == EINTR)
			/* nothing */;
		close(lockfd);
		return (-1);
	}
	log_debug("flock succeeded");

	return (lockfd);
}

/* Connect client to server. */
int
client_connect(struct event_base *base, char *path, int start_server)
{
	struct sockaddr_un	sa;
	size_t			size;
	int			fd, lockfd = -1, locked = 0;
	char		       *lockfile = NULL;

	memset(&sa, 0, sizeof sa);
	sa.sun_family = AF_UNIX;
	size = strlcpy(sa.sun_path, path, sizeof sa.sun_path);
	if (size >= sizeof sa.sun_path) {
		errno = ENAMETOOLONG;
		return (-1);
	}
	log_debug("socket is %s", path);

retry:
	if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
		fatal("socket failed");

	log_debug("trying connect");
	if (connect(fd, (struct sockaddr *) &sa, sizeof(sa)) == -1) {
		log_debug("connect failed: %s", strerror(errno));
		if (errno != ECONNREFUSED && errno != ENOENT)
			goto failed;
		if (!start_server)
			goto failed;
		close(fd);

		if (!locked) {
			xasprintf(&lockfile, "%s.lock", path);
			if ((lockfd = client_get_lock(lockfile)) == -1) {
				log_debug("didn't get lock");
				free(lockfile);
				goto retry;
			}
			log_debug("got lock");

			/*
			 * Always retry at least once, even if we got the lock,
			 * because another client could have taken the lock,
			 * started the server and released the lock between our
			 * connect() and flock().
			 */
			locked = 1;
			goto retry;
		}

		if (unlink(path) != 0 && errno != ENOENT) {
			free(lockfile);
			close(lockfd);
			return (-1);
		}
		fd = server_start(base, lockfd, lockfile);
	}

	if (locked) {
		free(lockfile);
		close(lockfd);
	}
	setblocking(fd, 0);
	return (fd);

failed:
	if (locked) {
		free(lockfile);
		close(lockfd);
	}
	close(fd);
	return (-1);
}

/* Get exit string from reason number. */
const char *
client_exit_message(void)
{
	static char msg[256];

	switch (client_exitreason) {
	case CLIENT_EXIT_NONE:
		break;
	case CLIENT_EXIT_DETACHED:
		if (client_exitsession != NULL) {
			xsnprintf(msg, sizeof msg, "detached "
			    "(from session %s)", client_exitsession);
			return (msg);
		}
		return ("detached");
	case CLIENT_EXIT_DETACHED_HUP:
		if (client_exitsession != NULL) {
			xsnprintf(msg, sizeof msg, "detached and SIGHUP "
			    "(from session %s)", client_exitsession);
			return (msg);
		}
		return ("detached and SIGHUP");
	case CLIENT_EXIT_LOST_TTY:
		return ("lost tty");
	case CLIENT_EXIT_TERMINATED:
		return ("terminated");
	case CLIENT_EXIT_LOST_SERVER:
		return ("lost server");
	case CLIENT_EXIT_EXITED:
		return ("exited");
	case CLIENT_EXIT_SERVER_EXITED:
		return ("server exited");
	}
	return ("unknown reason");
}

/* Client main loop. */
int
client_main(struct event_base *base, int argc, char **argv, int flags)
{
	struct cmd		*cmd;
	struct cmd_list		*cmdlist;
	struct msg_command_data	*data;
	int			 cmdflags, fd, i;
	const char		*ttynam, *cwd;
	pid_t			 ppid;
	enum msgtype		 msg;
	char			*cause, path[PATH_MAX];
	struct termios		 tio, saved_tio;
	size_t			 size;

	/* Ignore SIGCHLD now or daemon() in the server will leave a zombie. */
	signal(SIGCHLD, SIG_IGN);

	/* Save the flags. */
	client_flags = flags;

	/* Set up the initial command. */
	cmdflags = 0;
	if (shell_cmd != NULL) {
		msg = MSG_SHELL;
		cmdflags = CMD_STARTSERVER;
	} else if (argc == 0) {
		msg = MSG_COMMAND;
		cmdflags = CMD_STARTSERVER;
	} else {
		msg = MSG_COMMAND;

		/*
		 * It sucks parsing the command string twice (in client and
		 * later in server) but it is necessary to get the start server
		 * flag.
		 */
		cmdlist = cmd_list_parse(argc, argv, NULL, 0, &cause);
		if (cmdlist == NULL) {
			fprintf(stderr, "%s\n", cause);
			return (1);
		}
		cmdflags &= ~CMD_STARTSERVER;
		TAILQ_FOREACH(cmd, &cmdlist->list, qentry) {
			if (cmd->entry->flags & CMD_STARTSERVER)
				cmdflags |= CMD_STARTSERVER;
		}
		cmd_list_free(cmdlist);
	}

	/* Initialize the client socket and start the server. */
	fd = client_connect(base, socket_path, cmdflags & CMD_STARTSERVER);
	if (fd == -1) {
		if (errno == ECONNREFUSED) {
			fprintf(stderr, "no server running on %s\n",
			    socket_path);
		} else {
			fprintf(stderr, "error connecting to %s (%s)\n",
			    socket_path, strerror(errno));
		}
		return (1);
	}

	/* Build process state. */
	client_proc = proc_start("client", base, 0, client_signal);
	client_peer = proc_add_peer(client_proc, fd, client_dispatch, NULL);

	/* Save these before pledge(). */
	if ((cwd = getcwd(path, sizeof path)) == NULL) {
		if ((cwd = find_home()) == NULL)
			cwd = "/";
	}
	if ((ttynam = ttyname(STDIN_FILENO)) == NULL)
		ttynam = "";

	/*
	 * Drop privileges for client. "proc exec" is needed for -c and for
	 * locking (which uses system(3)).
	 *
	 * "tty" is needed to restore termios(4) and also for some reason -CC
	 * does not work properly without it (input is not recognised).
	 *
	 * "sendfd" is dropped later in client_dispatch_wait().
	 */
	if (pledge("stdio unix sendfd proc exec tty", NULL) != 0)
		fatal("pledge failed");

	/* Free stuff that is not used in the client. */
	options_free(global_options);
	options_free(global_s_options);
	options_free(global_w_options);
	environ_free(global_environ);

	/* Create stdin handler. */
	setblocking(STDIN_FILENO, 0);
	event_set(&client_stdin, STDIN_FILENO, EV_READ|EV_PERSIST,
	    client_stdin_callback, NULL);
	if (client_flags & CLIENT_CONTROLCONTROL) {
		if (tcgetattr(STDIN_FILENO, &saved_tio) != 0) {
			fprintf(stderr, "tcgetattr failed: %s\n",
			    strerror(errno));
			return (1);
		}
		cfmakeraw(&tio);
		tio.c_iflag = ICRNL|IXANY;
		tio.c_oflag = OPOST|ONLCR;
		tio.c_lflag = NOKERNINFO;
		tio.c_cflag = CREAD|CS8|HUPCL;
		tio.c_cc[VMIN] = 1;
		tio.c_cc[VTIME] = 0;
		cfsetispeed(&tio, cfgetispeed(&saved_tio));
		cfsetospeed(&tio, cfgetospeed(&saved_tio));
		tcsetattr(STDIN_FILENO, TCSANOW, &tio);
	}

	/* Send identify messages. */
	client_send_identify(ttynam, cwd);

	/* Send first command. */
	if (msg == MSG_COMMAND) {
		/* How big is the command? */
		size = 0;
		for (i = 0; i < argc; i++)
			size += strlen(argv[i]) + 1;
		data = xmalloc((sizeof *data) + size);

		/* Prepare command for server. */
		data->argc = argc;
		if (cmd_pack_argv(argc, argv, (char *)(data + 1), size) != 0) {
			fprintf(stderr, "command too long\n");
			free(data);
			return (1);
		}
		size += sizeof *data;

		/* Send the command. */
		if (proc_send(client_peer, msg, -1, data, size) != 0) {
			fprintf(stderr, "failed to send command\n");
			free(data);
			return (1);
		}
		free(data);
	} else if (msg == MSG_SHELL)
		proc_send(client_peer, msg, -1, NULL, 0);

	/* Start main loop. */
	proc_loop(client_proc, NULL);

	/* Print the exit message, if any, and exit. */
	if (client_attached) {
		if (client_exitreason != CLIENT_EXIT_NONE)
			printf("[%s]\n", client_exit_message());

		ppid = getppid();
		if (client_exittype == MSG_DETACHKILL && ppid > 1)
			kill(ppid, SIGHUP);
	} else if (client_flags & CLIENT_CONTROLCONTROL) {
		if (client_exitreason != CLIENT_EXIT_NONE)
			printf("%%exit %s\n", client_exit_message());
		else
			printf("%%exit\n");
		printf("\033\\");
		tcsetattr(STDOUT_FILENO, TCSAFLUSH, &saved_tio);
	}
	setblocking(STDIN_FILENO, 1);
	return (client_exitval);
}

/* Send identify messages to server. */
void
client_send_identify(const char *ttynam, const char *cwd)
{
	const char	 *s;
	char		**ss;
	size_t		  sslen;
	int		  fd, flags = client_flags;
	pid_t		  pid;

	proc_send(client_peer, MSG_IDENTIFY_FLAGS, -1, &flags, sizeof flags);

	if ((s = getenv("TERM")) == NULL)
		s = "";
	proc_send(client_peer, MSG_IDENTIFY_TERM, -1, s, strlen(s) + 1);

	proc_send(client_peer, MSG_IDENTIFY_TTYNAME, -1, ttynam, strlen(ttynam) + 1);
	proc_send(client_peer, MSG_IDENTIFY_CWD, -1, cwd, strlen(cwd) + 1);

	if ((fd = dup(STDIN_FILENO)) == -1)
		fatal("dup failed");
	proc_send(client_peer, MSG_IDENTIFY_STDIN, fd, NULL, 0);

	pid = getpid();
	proc_send(client_peer, MSG_IDENTIFY_CLIENTPID, -1, &pid, sizeof pid);

	for (ss = environ; *ss != NULL; ss++) {
		sslen = strlen(*ss) + 1;
		if (sslen <= MAX_IMSGSIZE - IMSG_HEADER_SIZE)
			proc_send(client_peer, MSG_IDENTIFY_ENVIRON, -1, *ss, sslen);
	}

	proc_send(client_peer, MSG_IDENTIFY_DONE, -1, NULL, 0);
}

/* Callback for client stdin read events. */
void
client_stdin_callback(unused int fd, unused short events, unused void *arg)
{
	struct msg_stdin_data	data;

	data.size = read(STDIN_FILENO, data.data, sizeof data.data);
	if (data.size < 0 && (errno == EINTR || errno == EAGAIN))
		return;

	proc_send(client_peer, MSG_STDIN, -1, &data, sizeof data);
	if (data.size <= 0)
		event_del(&client_stdin);
}

/* Force write to file descriptor. */
void
client_write(int fd, const char *data, size_t size)
{
	ssize_t	used;

	while (size != 0) {
		used = write(fd, data, size);
		if (used == -1) {
			if (errno == EINTR || errno == EAGAIN)
				continue;
			break;
		}
		data += used;
		size -= used;
	}
}

/* Run command in shell; used for -c. */
__dead void
client_exec(const char *shell)
{
	const char	*name, *ptr;
	char		*argv0;

	log_debug("shell %s, command %s", shell, shell_cmd);

	ptr = strrchr(shell, '/');
	if (ptr != NULL && *(ptr + 1) != '\0')
		name = ptr + 1;
	else
		name = shell;
	if (client_flags & CLIENT_LOGIN)
		xasprintf(&argv0, "-%s", name);
	else
		xasprintf(&argv0, "%s", name);
	setenv("SHELL", shell, 1);

	setblocking(STDIN_FILENO, 1);
	setblocking(STDOUT_FILENO, 1);
	setblocking(STDERR_FILENO, 1);
	closefrom(STDERR_FILENO + 1);

	execl(shell, argv0, "-c", shell_cmd, (char *) NULL);
	fatal("execl failed");
}

/* Callback to handle signals in the client. */
void
client_signal(int sig)
{
	struct sigaction sigact;
	int		 status;

	if (sig == SIGCHLD)
		waitpid(WAIT_ANY, &status, WNOHANG);
	else if (!client_attached) {
		if (sig == SIGTERM)
			proc_exit(client_proc);
	} else {
		switch (sig) {
		case SIGHUP:
			client_exitreason = CLIENT_EXIT_LOST_TTY;
			client_exitval = 1;
			proc_send(client_peer, MSG_EXITING, -1, NULL, 0);
			break;
		case SIGTERM:
			client_exitreason = CLIENT_EXIT_TERMINATED;
			client_exitval = 1;
			proc_send(client_peer, MSG_EXITING, -1, NULL, 0);
			break;
		case SIGWINCH:
			proc_send(client_peer, MSG_RESIZE, -1, NULL, 0);
			break;
		case SIGCONT:
			memset(&sigact, 0, sizeof sigact);
			sigemptyset(&sigact.sa_mask);
			sigact.sa_flags = SA_RESTART;
			sigact.sa_handler = SIG_IGN;
			if (sigaction(SIGTSTP, &sigact, NULL) != 0)
				fatal("sigaction failed");
			proc_send(client_peer, MSG_WAKEUP, -1, NULL, 0);
			break;
		}
	}
}

/* Callback for client read events. */
void
client_dispatch(struct imsg *imsg, unused void *arg)
{
	if (imsg == NULL) {
		client_exitreason = CLIENT_EXIT_LOST_SERVER;
		client_exitval = 1;
	} else if (client_attached)
		client_dispatch_attached(imsg);
	else
		client_dispatch_wait(imsg);
}

/* Dispatch imsgs when in wait state (before MSG_READY). */
void
client_dispatch_wait(struct imsg *imsg)
{
	char			*data;
	ssize_t			 datalen;
	struct msg_stdout_data	 stdoutdata;
	struct msg_stderr_data	 stderrdata;
	int			 retval;
	static int		 pledge_applied;

	/*
	 * "sendfd" is no longer required once all of the identify messages
	 * have been sent. We know the server won't send us anything until that
	 * point (because we don't ask it to), so we can drop "sendfd" once we
	 * get the first message from the server.
	 */
	if (!pledge_applied) {
		if (pledge("stdio unix proc exec tty", NULL) != 0)
			fatal("pledge failed");
		pledge_applied = 1;
	};

	data = imsg->data;
	datalen = imsg->hdr.len - IMSG_HEADER_SIZE;

	switch (imsg->hdr.type) {
	case MSG_EXIT:
	case MSG_SHUTDOWN:
		if (datalen != sizeof retval && datalen != 0)
			fatalx("bad MSG_EXIT size");
		if (datalen == sizeof retval) {
			memcpy(&retval, data, sizeof retval);
			client_exitval = retval;
		}
		proc_exit(client_proc);
		break;
	case MSG_READY:
		if (datalen != 0)
			fatalx("bad MSG_READY size");

		event_del(&client_stdin);
		client_attached = 1;
		proc_send(client_peer, MSG_RESIZE, -1, NULL, 0);
		break;
	case MSG_STDIN:
		if (datalen != 0)
			fatalx("bad MSG_STDIN size");

		event_add(&client_stdin, NULL);
		break;
	case MSG_STDOUT:
		if (datalen != sizeof stdoutdata)
			fatalx("bad MSG_STDOUT size");
		memcpy(&stdoutdata, data, sizeof stdoutdata);

		client_write(STDOUT_FILENO, stdoutdata.data,
		    stdoutdata.size);
		break;
	case MSG_STDERR:
		if (datalen != sizeof stderrdata)
			fatalx("bad MSG_STDERR size");
		memcpy(&stderrdata, data, sizeof stderrdata);

		client_write(STDERR_FILENO, stderrdata.data,
		    stderrdata.size);
		break;
	case MSG_VERSION:
		if (datalen != 0)
			fatalx("bad MSG_VERSION size");

		fprintf(stderr, "protocol version mismatch "
		    "(client %d, server %u)\n", PROTOCOL_VERSION,
		    imsg->hdr.peerid);
		client_exitval = 1;
		proc_exit(client_proc);
		break;
	case MSG_SHELL:
		if (datalen == 0 || data[datalen - 1] != '\0')
			fatalx("bad MSG_SHELL string");

		clear_signals(0);
		client_exec(data);
		/* NOTREACHED */
	case MSG_DETACH:
	case MSG_DETACHKILL:
		proc_send(client_peer, MSG_EXITING, -1, NULL, 0);
		break;
	case MSG_EXITED:
		proc_exit(client_proc);
		break;
	}
}

/* Dispatch imsgs in attached state (after MSG_READY). */
void
client_dispatch_attached(struct imsg *imsg)
{
	struct sigaction	 sigact;
	char			*data;
	ssize_t			 datalen;

	data = imsg->data;
	datalen = imsg->hdr.len - IMSG_HEADER_SIZE;

	switch (imsg->hdr.type) {
	case MSG_DETACH:
	case MSG_DETACHKILL:
		if (datalen == 0 || data[datalen - 1] != '\0')
			fatalx("bad MSG_DETACH string");

		client_exitsession = xstrdup(data);
		client_exittype = imsg->hdr.type;
		if (imsg->hdr.type == MSG_DETACHKILL)
			client_exitreason = CLIENT_EXIT_DETACHED_HUP;
		else
			client_exitreason = CLIENT_EXIT_DETACHED;
		proc_send(client_peer, MSG_EXITING, -1, NULL, 0);
		break;
	case MSG_EXIT:
		if (datalen != 0 && datalen != sizeof (int))
			fatalx("bad MSG_EXIT size");

		proc_send(client_peer, MSG_EXITING, -1, NULL, 0);
		client_exitreason = CLIENT_EXIT_EXITED;
		break;
	case MSG_EXITED:
		if (datalen != 0)
			fatalx("bad MSG_EXITED size");

		proc_exit(client_proc);
		break;
	case MSG_SHUTDOWN:
		if (datalen != 0)
			fatalx("bad MSG_SHUTDOWN size");

		proc_send(client_peer, MSG_EXITING, -1, NULL, 0);
		client_exitreason = CLIENT_EXIT_SERVER_EXITED;
		client_exitval = 1;
		break;
	case MSG_SUSPEND:
		if (datalen != 0)
			fatalx("bad MSG_SUSPEND size");

		memset(&sigact, 0, sizeof sigact);
		sigemptyset(&sigact.sa_mask);
		sigact.sa_flags = SA_RESTART;
		sigact.sa_handler = SIG_DFL;
		if (sigaction(SIGTSTP, &sigact, NULL) != 0)
			fatal("sigaction failed");
		kill(getpid(), SIGTSTP);
		break;
	case MSG_LOCK:
		if (datalen == 0 || data[datalen - 1] != '\0')
			fatalx("bad MSG_LOCK string");

		system(data);
		proc_send(client_peer, MSG_UNLOCK, -1, NULL, 0);
		break;
	}
}