Remove the internal tmux locking and instead detach each client and run the

command specified by a new option "lock-command" (by default "lock -np") in
each client.

This means each terminal has to be unlocked individually but simplifies the
code and allows the system password to be used to unlock.

Note that the set-password command is gone, so it will need to be removed from
configuration files, and the -U command line flag has been removed.

This is the third protocol version change so again it is best to stop the tmux
server before upgrading.

13 files changed, 55 insertions, 449 deletions

diff --git a/Makefile b/Makefile
index c2a51436..f35149df 100644
--- a/Makefile
+++ b/Makefile
@@ -20,7 +20,7 @@ SRCS=	attributes.c buffer-poll.c buffer.c cfg.c client-fn.c \
 	cmd-scroll-mode.c cmd-select-layout.c cmd-select-pane.c \
 	cmd-select-prompt.c cmd-select-window.c cmd-send-keys.c \
 	cmd-send-prefix.c cmd-server-info.c cmd-set-buffer.c cmd-set-option.c \
-	cmd-set-password.c cmd-set-window-option.c cmd-show-buffer.c \
+	cmd-set-window-option.c cmd-show-buffer.c \
 	cmd-show-options.c cmd-show-window-options.c cmd-source-file.c \
 	cmd-split-window.c cmd-start-server.c cmd-string.c cmd-if-shell.c \
 	cmd-run-shell.c cmd-suspend-client.c cmd-swap-pane.c cmd-swap-window.c \
diff --git a/client.c b/client.c
index 7ef61106..ceb054bb 100644
--- a/client.c
+++ b/client.c
@@ -242,6 +242,7 @@ client_msg_dispatch(struct client_ctx *cctx)
 {
 	struct imsg		 imsg;
 	struct msg_print_data	 printdata;
+	struct msg_lock_data	 lockdata;
 	ssize_t			 n, datalen;
 
 	for (;;) {
@@ -295,6 +296,15 @@ client_msg_dispatch(struct client_ctx *cctx)
 
 			client_suspend();
 			break;
+		case MSG_LOCK:
+			if (datalen != sizeof lockdata)
+				fatalx("bad MSG_LOCK size");
+			memcpy(&lockdata, imsg.data, sizeof lockdata);
+			
+			lockdata.cmd[(sizeof lockdata.cmd) - 1] = '\0';
+			system(lockdata.cmd);
+			client_write_server(cctx, MSG_UNLOCK, NULL, 0);
+			break;
 		default:
 			fatalx("unexpected message");
 		}
diff --git a/cmd-set-option.c b/cmd-set-option.c
index 3a6bf022..4984cb1a 100644
--- a/cmd-set-option.c
+++ b/cmd-set-option.c
@@ -62,6 +62,7 @@ const struct set_option_entry set_option_table[] = {
 	{ "display-time", SET_OPTION_NUMBER, 1, INT_MAX, NULL },
 	{ "history-limit", SET_OPTION_NUMBER, 0, INT_MAX, NULL },
 	{ "lock-after-time", SET_OPTION_NUMBER, 0, INT_MAX, NULL },
+	{ "lock-command", SET_OPTION_STRING, 0, 0, NULL },
 	{ "message-attr", SET_OPTION_ATTRIBUTES, 0, 0, NULL },
 	{ "message-bg", SET_OPTION_COLOUR, 0, 0, NULL },
 	{ "message-fg", SET_OPTION_COLOUR, 0, 0, NULL },
diff --git a/cmd-set-password.c b/cmd-set-password.c
deleted file mode 100644
index 1a6da3f1..00000000
--- a/cmd-set-password.c
+++ /dev/null
@@ -1,145 +0,0 @@
-/* $OpenBSD$ */
-
-/*
- * Copyright (c) 2009 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 <pwd.h>
-#include <unistd.h>
-
-#include "tmux.h"
-
-/*
- * Set server password.
- */
-
-int	cmd_set_password_parse(struct cmd *, int, char **, char **);
-int	cmd_set_password_exec(struct cmd *, struct cmd_ctx *);
-void	cmd_set_password_free(struct cmd *);
-void	cmd_set_password_init(struct cmd *, int);
-size_t	cmd_set_password_print(struct cmd *, char *, size_t);
-
-struct cmd_set_password_data {
-	char	*password;
-	int	 flag_encrypted;
-};
-
-const struct cmd_entry cmd_set_password_entry = {
-	"set-password", "pass",
-	"[-c] password",
-	0, 0,
-	cmd_set_password_init,
-	cmd_set_password_parse,
-	cmd_set_password_exec,
-	cmd_set_password_free,
-	cmd_set_password_print
-};
-
-void
-cmd_set_password_init(struct cmd *self, unused int arg)
-{
-	struct cmd_set_password_data	 *data;
-
-	self->data = data = xmalloc(sizeof *data);
-	data->password = NULL;
-	data->flag_encrypted = 0;
-}
-
-int
-cmd_set_password_parse(struct cmd *self, int argc, char **argv, char **cause)
-{
-	struct cmd_set_password_data	*data;
-	int				 opt;
-	char				*out;
-
-	self->entry->init(self, KEYC_NONE);
-	data = self->data;
-
-	while ((opt = getopt(argc, argv, "c")) != -1) {
-		switch (opt) {
-		case 'c':
-			data->flag_encrypted = 1;
-			break;
-		default:
-			goto usage;
-		}
-	}
-	argc -= optind;
-	argv += optind;
-	if (argc != 1)
-		goto usage;
-
-	if (!data->flag_encrypted) {
-		if ((out = crypt(argv[0], "$1")) != NULL)
-			data->password = xstrdup(out);
-	} else
-		data->password = xstrdup(argv[0]);
-
-	return (0);
-
-usage:
-	xasprintf(cause, "usage: %s %s", self->entry->name, self->entry->usage);
-
-	self->entry->free(self);
-	return (-1);
-}
-
-int
-cmd_set_password_exec(struct cmd *self, struct cmd_ctx *ctx)
-{
-	struct cmd_set_password_data	*data = self->data;
-
-	if (data->password == NULL) {
-		ctx->error(ctx, "failed to encrypt password");
-		return (-1);
-	}
-
-	if (server_password != NULL)
-		xfree(server_password);
-	if (*data->password == '\0')
-		server_password = NULL;
-	else
-		server_password = xstrdup(data->password);
-
- 	return (0);
-}
-
-void
-cmd_set_password_free(struct cmd *self)
-{
-	struct cmd_set_password_data	*data = self->data;
-
-	if (data->password != NULL)
-		xfree(data->password);
-	xfree(data);
-}
-
-size_t
-cmd_set_password_print(struct cmd *self, char *buf, size_t len)
-{
-	struct cmd_set_password_data	*data = self->data;
-	size_t				 off = 0;
-
-	off += xsnprintf(buf, len, "%s", self->entry->name);
-	if (data == NULL)
-		return (off);
-	if (off < len && data->flag_encrypted)
-		off += xsnprintf(buf + off, len - off, " -c");
-	if (off < len && data->password != NULL)
-		off += xsnprintf(buf + off, len - off, " password");
-	return (off);
-}
diff --git a/cmd.c b/cmd.c
index a391945d..d027cd9c 100644
--- a/cmd.c
+++ b/cmd.c
@@ -89,7 +89,6 @@ const struct cmd_entry *cmd_table[] = {
 	&cmd_set_buffer_entry,
 	&cmd_set_environment_entry,
 	&cmd_set_option_entry,
-	&cmd_set_password_entry,
 	&cmd_set_window_option_entry,
 	&cmd_show_buffer_entry,
 	&cmd_show_environment_entry,
@@ -260,10 +259,6 @@ usage:
 int
 cmd_exec(struct cmd *cmd, struct cmd_ctx *ctx)
 {
-	if (server_locked) {
-		ctx->error(ctx, "server is locked");
-		return (-1);
-	}
 	return (cmd->entry->exec(cmd, ctx));
 }
 
diff --git a/server-fn.c b/server-fn.c
index e3cee410..b9be1794 100644
--- a/server-fn.c
+++ b/server-fn.c
@@ -18,16 +18,12 @@
 
 #include <sys/types.h>
 
-#include <login_cap.h>
-#include <pwd.h>
 #include <string.h>
 #include <time.h>
 #include <unistd.h>
 
 #include "tmux.h"
 
-int	server_lock_callback(void *, const char *);
-
 void
 server_fill_environ(struct session *s, struct environ *env)
 {
@@ -161,110 +157,30 @@ server_status_window(struct window *w)
 void
 server_lock(void)
 {
-	struct client	       *c;
-	static struct passwd   *pw, pwstore;
-	static char		pwbuf[_PW_BUF_LEN];
-	u_int			i;
-
-	if (server_locked)
-		return;
-
-	if (getpwuid_r(getuid(), &pwstore, pwbuf, sizeof pwbuf, &pw) != 0) {
-		server_locked_pw = NULL;
-		return;
-	}
-	server_locked_pw = pw;
+	struct client		*c;
+	const char		*cmd;
+	struct msg_lock_data	 lockdata;
+	u_int			 i;
 
 	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
 		c = ARRAY_ITEM(&clients, i);
 		if (c == NULL || c->session == NULL)
 			continue;
-
-		status_prompt_clear(c);
-		status_prompt_set(c,
-		    "Password:", server_lock_callback, NULL, c, PROMPT_HIDDEN);
-  		server_redraw_client(c);
-	}
-
-	server_locked = 1;
-}
-
-int
-server_lock_callback(unused void *data, const char *s)
-{
-	return (server_unlock(s));
-}
-
-int
-server_unlock(const char *s)
-{
-	struct client	*c;
-	login_cap_t	*lc;
-	u_int		 i;
-	char		*out;
-	u_int		 failures, tries, backoff;
-
-	if (!server_locked || server_locked_pw == NULL)
-		return (0);
-	server_activity = time(NULL);
-	if (server_activity < password_backoff)
-		return (-2);
-
-	if (server_password != NULL) {
-		if (s == NULL)
-			return (-1);
-		out = crypt(s, server_password);
-		if (strcmp(out, server_password) != 0)
-			goto wrong;
-	}
-
-	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
-		c = ARRAY_ITEM(&clients, i);
-		if (c == NULL)
+		if (c->flags & CLIENT_SUSPENDED)
 			continue;
 
-		status_prompt_clear(c);
-  		server_redraw_client(c);
-	}
-
-	server_locked = 0;
-	password_failures = 0;
-	password_backoff = 0;
-	return (0);
-
-wrong:
-	password_failures++;
-	password_backoff = 0;
-
-	for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
-		c = ARRAY_ITEM(&clients, i);
-		if (c == NULL || c->prompt_buffer == NULL)
+		cmd = options_get_string(&c->session->options, "lock-command");
+		if (strlcpy(lockdata.cmd, 
+		    cmd, sizeof lockdata.cmd) >= sizeof lockdata.cmd)
 			continue;
 
-		*c->prompt_buffer = '\0';
-		c->prompt_index = 0;
-  		server_redraw_client(c);
-	}
+		tty_stop_tty(&c->tty);
+		tty_raw(&c->tty, tty_term_string(c->tty.term, TTYC_SMCUP));
+		tty_raw(&c->tty, tty_term_string(c->tty.term, TTYC_CLEAR));
 
-	/*
-	 * Start slowing down after "login-backoff" attempts and reset every
-	 * "login-tries" attempts.
-	 */
-	lc = login_getclass(server_locked_pw->pw_class);
-	if (lc != NULL) {
-		tries = login_getcapnum(lc, (char *) "login-tries", 10, 10);
-		backoff = login_getcapnum(lc, (char *) "login-backoff", 3, 3);
-	} else {
-		tries = 10;
-		backoff = 3;
-	}
-	failures = password_failures % tries;
-	if (failures > backoff) {
-		password_backoff = 
-		    server_activity + ((failures - backoff) * tries / 2);
-		return (-2);
+		c->flags |= CLIENT_SUSPENDED;
+		server_write_client(c, MSG_LOCK, &lockdata, sizeof lockdata);
 	}
-	return (-1);
 }
 
 void
diff --git a/server-msg.c b/server-msg.c
index 7f88e262..0b9b2a90 100644
--- a/server-msg.c
+++ b/server-msg.c
@@ -40,7 +40,6 @@ server_msg_dispatch(struct client *c)
 	struct imsg		 imsg;
 	struct msg_command_data	 commanddata;
 	struct msg_identify_data identifydata;
-	struct msg_unlock_data	 unlockdata;
 	struct msg_environ_data	 environdata;
 	ssize_t			 n, datalen;
 
@@ -95,31 +94,15 @@ server_msg_dispatch(struct client *c)
 			tty_close(&c->tty);
 			server_write_client(c, MSG_EXITED, NULL, 0);
 			break;
-		case MSG_UNLOCK:
-			if (datalen != sizeof unlockdata)
-				fatalx("bad MSG_UNLOCK size");
-			memcpy(&unlockdata, imsg.data, sizeof unlockdata);
-
-			unlockdata.pass[(sizeof unlockdata.pass) - 1] = '\0';
-			switch (server_unlock(unlockdata.pass)) {
-			case -1:
-				server_write_error(c, "bad password");
-				break;
-			case -2:
-				server_write_error(c,
-				    "too many bad passwords, sleeping");
-				break;
-			}
-			memset(&unlockdata, 0, sizeof unlockdata);
-			server_write_client(c, MSG_EXIT, NULL, 0);
-			break;
 		case MSG_WAKEUP:
+		case MSG_UNLOCK:
 			if (datalen != 0)
 				fatalx("bad MSG_WAKEUP size");
 
 			c->flags &= ~CLIENT_SUSPENDED;
 			tty_start_tty(&c->tty);
 			server_redraw_client(c);
+			server_activity = time(NULL);
 			break;
 		case MSG_ENVIRON:
 			if (datalen != sizeof environdata)
diff --git a/server.c b/server.c
index cb69df0f..e465ace0 100644
--- a/server.c
+++ b/server.c
@@ -67,7 +67,6 @@ void		 server_lost_client(struct client *);
 void	 	 server_check_window(struct window *);
 void		 server_check_redraw(struct client *);
 void		 server_set_title(struct client *);
-void		 server_redraw_locked(struct client *);
 void		 server_check_timers(struct client *);
 void		 server_second_timers(void);
 int		 server_update_socket(void);
@@ -160,8 +159,6 @@ server_start(char *path)
 	key_bindings_init();
 	utf8_build();
 
-	server_locked = 0;
-	server_password = NULL;
 	server_activity = time(NULL);
 
 	start_time = time(NULL);
@@ -382,8 +379,6 @@ server_main(int srv_fd)
 
 	options_free(&global_s_options);
 	options_free(&global_w_options);
-	if (server_password != NULL)
-		xfree(server_password);
 
 	return (0);
 }
@@ -541,10 +536,7 @@ server_check_redraw(struct client *c)
 	}
 
 	if (c->flags & CLIENT_REDRAW) {
-		if (server_locked)
-			server_redraw_locked(c);
-		else
- 			screen_redraw_screen(c, 0);
+		screen_redraw_screen(c, 0);
 		c->flags &= ~CLIENT_STATUS;
 	} else {
 		TAILQ_FOREACH(wp, &c->session->curw->window->panes, entry) {
@@ -581,49 +573,6 @@ server_set_title(struct client *c)
 	xfree(title);
 }
 
-/* Redraw client when locked. */
-void
-server_redraw_locked(struct client *c)
-{
-	struct screen_write_ctx	ctx;
-	struct screen		screen;
-	struct grid_cell	gc;
-	u_int			colour, xx, yy, i;
-	int    			style;
-
-	xx = c->tty.sx;
-	yy = c->tty.sy - 1;
-	if (xx == 0 || yy == 0)
-		return;
-	colour = options_get_number(&global_w_options, "clock-mode-colour");
-	style = options_get_number(&global_w_options, "clock-mode-style");
-
-	memcpy(&gc, &grid_default_cell, sizeof gc);
-	colour_set_fg(&gc, colour);
-	gc.attr |= GRID_ATTR_BRIGHT;
-
-	screen_init(&screen, xx, yy, 0);
-
-	screen_write_start(&ctx, NULL, &screen);
-	clock_draw(&ctx, colour, style);
-
-	if (password_failures != 0) {
-		screen_write_cursormove(&ctx, 0, 0);
-		screen_write_puts(
-		    &ctx, &gc, "%u failed attempts", password_failures);
-		if (time(NULL) < password_backoff)
-			screen_write_puts(&ctx, &gc, "; sleeping");
-	}
-
-	screen_write_stop(&ctx);
-
-	for (i = 0; i < screen_size_y(&screen); i++)
-		tty_draw_line(&c->tty, &screen, i, 0, 0);
-	screen_redraw_screen(c, 1);
-
-	screen_free(&screen);
-}
-
 /* Check for timers on client. */
 void
 server_check_timers(struct client *c)
@@ -836,8 +785,6 @@ server_handle_client(struct client *c)
 			status_prompt_key(c, key);
 			continue;
 		}
-		if (server_locked)
-			continue;
 
 		/* Check for mouse keys. */
 		if (key == KEYC_MOUSE) {
@@ -929,8 +876,6 @@ server_handle_client(struct client *c)
 		tty_cursor(&c->tty, s->cx, s->cy, wp->xoff, wp->yoff);
 
 	mode = s->mode;
-	if (server_locked)
-		mode &= ~TTY_NOCURSOR;
 	tty_update_mode(&c->tty, mode);
 	tty_reset(&c->tty);
 }
@@ -1235,12 +1180,9 @@ void
 server_second_timers(void)
 {
 	struct window		*w;
-	struct client		*c;
 	struct window_pane	*wp;
 	u_int		 	 i;
 	int			 xtimeout;
-	struct tm	 	 now, then;
-	static time_t	 	 last_t = 0;
 	time_t		 	 t;
 
 	t = time(NULL);
@@ -1259,29 +1201,6 @@ server_second_timers(void)
 				wp->mode->timer(wp);
 		}
 	}
-
-	if (password_backoff != 0 && t >= password_backoff) {
-		for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
-			if ((c = ARRAY_ITEM(&clients, i)) != NULL)
-				server_redraw_client(c);
-		}
-		password_backoff = 0;
-	}
-
-	/* Check for a minute having passed. */
-	gmtime_r(&t, &now);
-	gmtime_r(&last_t, &then);
-	if (now.tm_min == then.tm_min)
-		return;
-	last_t = t;
-
-	/* If locked, redraw all clients. */
-	if (server_locked) {
-		for (i = 0; i < ARRAY_LENGTH(&clients); i++) {
-			if ((c = ARRAY_ITEM(&clients, i)) != NULL)
-				server_redraw_client(c);
-		}
-	}
 }
 
 /* Update socket execute permissions based on whether sessions are attached. */
diff --git a/status.c b/status.c
index 77062729..6527630c 100644
--- a/status.c
+++ b/status.c
@@ -890,9 +890,6 @@ status_prompt_key(struct client *c, int key)
 		}
 		break;
 	case MODEKEYEDIT_HISTORYUP:
-		if (server_locked)
-			break;
-
 		if (ARRAY_LENGTH(&c->prompt_hdata) == 0)
 			break;
 		if (c->prompt_flags & PROMPT_HIDDEN)
@@ -908,9 +905,6 @@ status_prompt_key(struct client *c, int key)
 		c->flags |= CLIENT_STATUS;
 		break;
 	case MODEKEYEDIT_HISTORYDOWN:
-		if (server_locked)
-			break;
-
 		if (c->prompt_flags & PROMPT_HIDDEN)
 			memset(c->prompt_buffer, 0, strlen(c->prompt_buffer));
 		xfree(c->prompt_buffer);
@@ -1003,9 +997,6 @@ status_prompt_key(struct client *c, int key)
 void
 status_prompt_add_history(struct client *c)
 {
-	if (server_locked)
-		return;
-
 	if (ARRAY_LENGTH(&c->prompt_hdata) > 0 &&
 	    strcmp(ARRAY_LAST(&c->prompt_hdata), c->prompt_buffer) == 0)
 		return;
diff --git a/tmux.1 b/tmux.1
index 802b0fd9..7155dcd2 100644
--- a/tmux.1
+++ b/tmux.1
@@ -23,7 +23,7 @@
 .Sh SYNOPSIS
 .Nm tmux
 .Bk -words
-.Op Fl 28dlqUuv
+.Op Fl 28dlquv
 .Op Fl f Ar file
 .Op Fl L Ar socket-name
 .Op Fl S Ar socket-path
@@ -154,8 +154,6 @@ If
 is specified, the default socket directory is not used and any
 .Fl L
 flag is ignored.
-.It Fl U
-Unlock the server.
 .It Fl u
 .Nm
 attempts to guess if the terminal is likely to support UTF-8 by checking the
@@ -337,8 +335,6 @@ rename-session -tfirst newname
 set-window-option -t:0 monitor-activity on
 
 new-window ; split-window -d
-
-bind-key D detach-client \e\; lock-server
 .Ed
 .Sh CLIENTS AND SESSIONS
 The following commands are available:
@@ -1213,17 +1209,20 @@ Set the maximum number of lines held in window history.
 This setting applies only to new windows - existing window histories are not
 resized and retain the limit at the point they were created.
 .It Ic lock-after-time Ar number
-Lock the server after
+Lock the server (like the
+.Ic lock-server
+command) after
 .Ar number
 seconds of inactivity.
 The default is off (set to 0).
 This has no effect as a session option; it must be set as a global option using
 .Fl g .
-When passwords are entered incorrectly,
-.Nm
-follows the behaviour of
-.Xr login 1
-and ignores further password attempts for an increasing timeout.
+.It Ic lock-command Ar command
+Command to run when locking each client.
+The default is to run
+.Xr lock 1
+with
+.Fl np .
 .It Ic message-attr Ar attributes
 Set status line message attributes, where
 .Ar attributes
@@ -1962,7 +1961,9 @@ if
 returns success.
 .It Ic lock-server
 .D1 (alias: Ic lock )
-Lock the server until a password is entered.
+Lock each client individually by running the command specified by the
+.Ic lock-command
+option.
 .It Ic run-shell Ar command
 .D1 (alias: Ic run )
 Execute
@@ -1975,21 +1976,6 @@ doesn't return success, the exit status is also displayed.
 .It Ic server-info
 .D1 (alias: Ic info )
 Show server information and terminal details.
-.It Xo Ic set-password
-.Op Fl c
-.Ar password
-.Xc
-.D1 (alias: Ic pass )
-Set the server password.
-If the
-.Fl c
-option is given, a pre-encrypted password may be specified.
-By default, the password is blank, thus any entered password will be accepted
-when unlocking the server (see the
-.Ic lock-server
-command).
-To prevent variable expansion when an encrypted password is read from a
-configuration file, enclose it in single quotes (').
 .El
 .Sh FILES
 .Bl -tag -width "/etc/tmux.confXXX" -compact
diff --git a/tmux.c b/tmux.c
index 02657e32..bde1e7f2 100644
--- a/tmux.c
+++ b/tmux.c
@@ -46,11 +46,6 @@ struct options	 global_s_options;	/* session options */
 struct options	 global_w_options;	/* window options */
 struct environ	 global_environ;
 
-int		 server_locked;
-struct passwd	*server_locked_pw;
-u_int		 password_failures;
-time_t		 password_backoff;
-char		*server_password;
 time_t		 server_activity;
 
 int		 debug_level;
@@ -61,7 +56,6 @@ int		 login_shell;
 
 __dead void	 usage(void);
 char 		*makesockpath(const char *);
-int		 prepare_unlock(enum msgtype *, void **, size_t *, int);
 int		 prepare_cmd(enum msgtype *, void **, size_t *, int, char **);
 int		 dispatch_imsg(struct client_ctx *, int *);
 
@@ -69,7 +63,7 @@ __dead void
 usage(void)
 {
 	fprintf(stderr,
-	    "usage: %s [-28dlqUuv] [-f file] [-L socket-name]\n"
+	    "usage: %s [-28dlquv] [-f file] [-L socket-name]\n"
 	    "            [-S socket-path] [command [flags]]\n",
 	    __progname);
 	exit(1);
@@ -251,35 +245,6 @@ makesockpath(const char *label)
 }
 
 int
-prepare_unlock(enum msgtype *msg, void **buf, size_t *len, int argc)
-{
-	static struct msg_unlock_data	 unlockdata;
-	char				*pass;
-
-	if (argc != 0) {
-		log_warnx("can't specify a command when unlocking");
-		return (-1);
-	}
-	
-	if ((pass = getpass("Password:")) == NULL)
-		return (-1);
-
-	if (strlen(pass) >= sizeof unlockdata.pass) {
-		log_warnx("password too long");
-		return (-1);
-	}
-		
-	strlcpy(unlockdata.pass, pass, sizeof unlockdata.pass);
-	memset(pass, 0, strlen(pass));
-
-	*buf = &unlockdata;
-	*len = sizeof unlockdata;
-
-	*msg = MSG_UNLOCK;
-	return (0);
-}
-
-int
 prepare_cmd(enum msgtype *msg, void **buf, size_t *len, int argc, char **argv)
 {
 	static struct msg_command_data	 cmddata;
@@ -314,10 +279,10 @@ main(int argc, char **argv)
 	char			 cwd[MAXPATHLEN];
 	void			*buf;
 	size_t			 len;
-	int	 		 retcode, opt, flags, unlock, cmdflags = 0;
+	int	 		 retcode, opt, flags, cmdflags = 0;
 	int			 nfds;
 
-	unlock = flags = 0;
+	flags = 0;
 	label = path = NULL;
 	login_shell = (**argv == '-');
 	while ((opt = getopt(argc, argv, "28df:lL:qS:uUv")) != -1) {
@@ -357,9 +322,6 @@ main(int argc, char **argv)
 		case 'u':
 			flags |= IDENTIFY_UTF8;
 			break;
-		case 'U':
-			unlock = 1;
-			break;
 		case 'v':
 			debug_level++;
 			break;
@@ -407,6 +369,7 @@ main(int argc, char **argv)
 	options_set_number(so, "display-time", 750);
 	options_set_number(so, "history-limit", 2000);
 	options_set_number(so, "lock-after-time", 0);
+	options_set_string(so, "lock-command", "lock -np");
 	options_set_number(so, "message-attr", 0);
 	options_set_number(so, "message-bg", 3);
 	options_set_number(so, "message-fg", 0);
@@ -514,17 +477,10 @@ main(int argc, char **argv)
 	}
 	xfree(label);
 
-	if (unlock) {
-		if (prepare_unlock(&msg, &buf, &len, argc) != 0)
-			exit(1);
-	} else {
-		if (prepare_cmd(&msg, &buf, &len, argc, argv) != 0)
-			exit(1);
-	}
+	if (prepare_cmd(&msg, &buf, &len, argc, argv) != 0)
+		exit(1);
 
-	if (unlock)
-		cmdflags &= ~CMD_STARTSERVER;
-	else if (argc == 0)	/* new-session is the default */
+	if (argc == 0)	/* new-session is the default */
 		cmdflags |= CMD_STARTSERVER|CMD_SENDENVIRON;
 	else {
 		/*
diff --git a/tmux.h b/tmux.h
index 6325bca2..cea6c194 100644
--- a/tmux.h
+++ b/tmux.h
@@ -19,7 +19,7 @@
 #ifndef TMUX_H
 #define TMUX_H
 
-#define PROTOCOL_VERSION 3
+#define PROTOCOL_VERSION 4
 
 #include <sys/param.h>
 #include <sys/time.h>
@@ -304,10 +304,11 @@ enum msgtype {
 	MSG_RESIZE,
 	MSG_SHUTDOWN,
 	MSG_SUSPEND,
-	MSG_UNLOCK,
 	MSG_VERSION,
 	MSG_WAKEUP,
-	MSG_ENVIRON
+	MSG_ENVIRON,
+	MSG_UNLOCK,
+	MSG_LOCK
 };
 
 /*
@@ -339,8 +340,8 @@ struct msg_identify_data {
 	int		flags;
 };
 
-struct msg_unlock_data {
-	char	       	pass[PASS_MAX];
+struct msg_lock_data {
+	char	       	cmd[COMMAND_LENGTH];
 };
 
 struct msg_environ_data {
@@ -1108,11 +1109,6 @@ extern struct options global_s_options;
 extern struct options global_w_options;
 extern struct environ global_environ;
 extern char	*cfg_file;
-extern int	 server_locked;
-extern struct passwd *server_locked_pw;
-extern u_int	 password_failures;
-extern time_t	 password_backoff;
-extern char	*server_password;
 extern time_t	 server_activity;
 extern int	 debug_level;
 extern int	 be_quiet;
@@ -1179,6 +1175,7 @@ void	environ_unset(struct environ *, const char *);
 void 	environ_update(const char *, struct environ *, struct environ *);
 
 /* tty.c */
+void	tty_raw(struct tty *, const char *);
 u_char	tty_get_acs(struct tty *, u_char);
 void	tty_attributes(struct tty *, const struct grid_cell *);
 void	tty_reset(struct tty *);
@@ -1352,7 +1349,6 @@ extern const struct cmd_entry cmd_server_info_entry;
 extern const struct cmd_entry cmd_set_buffer_entry;
 extern const struct cmd_entry cmd_set_environment_entry;
 extern const struct cmd_entry cmd_set_option_entry;
-extern const struct cmd_entry cmd_set_password_entry;
 extern const struct cmd_entry cmd_set_window_option_entry;
 extern const struct cmd_entry cmd_show_buffer_entry;
 extern const struct cmd_entry cmd_show_environment_entry;
diff --git a/tty.c b/tty.c
index 12535f94..82cfac80 100644
--- a/tty.c
+++ b/tty.c
@@ -29,8 +29,6 @@
 
 void	tty_fill_acs(struct tty *);
 
-void	tty_raw(struct tty *, const char *);
-
 int	tty_try_256(struct tty *, u_char, const char *);
 int	tty_try_88(struct tty *, u_char, const char *);