Ignore default-shell (and use /bin/sh) if it invalid not just if it is

tmux itself, also refuse to set the option to something invalid in the
first place. GitHub issue 2120.

5 files changed, 20 insertions, 11 deletions

diff --git a/usr.bin/tmux/cmd-set-option.c b/usr.bin/tmux/cmd-set-option.c
index 55691d015d1..c91f623d665 100644
--- a/usr.bin/tmux/cmd-set-option.c
+++ b/usr.bin/tmux/cmd-set-option.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: cmd-set-option.c,v 1.127 2019/06/20 11:59:59 nicm Exp $ */
+/* $OpenBSD: cmd-set-option.c,v 1.128 2020/03/17 11:10:12 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -309,6 +309,13 @@ cmd_set_option_set(struct cmd *self, struct cmdq_item *item, struct options *oo,
 		old = xstrdup(options_get_string(oo, oe->name));
 		options_set_string(oo, oe->name, append, "%s", value);
 		new = options_get_string(oo, oe->name);
+		if (strcmp(oe->name, "default-shell") == 0 &&
+		    !checkshell(new)) {
+			options_set_string(oo, oe->name, 0, "%s", old);
+			free(old);
+			cmdq_error(item, "not a suitable shell: %s", value);
+			return (-1);
+		}
 		if (oe->pattern != NULL && fnmatch(oe->pattern, new, 0) != 0) {
 			options_set_string(oo, oe->name, 0, "%s", old);
 			free(old);
diff --git a/usr.bin/tmux/server-client.c b/usr.bin/tmux/server-client.c
index c33be44fa0b..f4666cd704f 100644
--- a/usr.bin/tmux/server-client.c
+++ b/usr.bin/tmux/server-client.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: server-client.c,v 1.307 2020/03/16 06:12:42 nicm Exp $ */
+/* $OpenBSD: server-client.c,v 1.308 2020/03/17 11:10:12 nicm Exp $ */
 
 /*
  * Copyright (c) 2009 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -400,6 +400,8 @@ server_client_exec(struct client *c, const char *cmd)
 		shell = options_get_string(s->options, "default-shell");
 	else
 		shell = options_get_string(global_s_options, "default-shell");
+	if (!checkshell(shell))
+		shell = _PATH_BSHELL;
 	shellsize = strlen(shell) + 1;
 
 	msg = xmalloc(cmdsize + shellsize);
@@ -2009,7 +2011,7 @@ server_client_dispatch_shell(struct client *c)
 	const char	*shell;
 
 	shell = options_get_string(global_s_options, "default-shell");
-	if (*shell == '\0' || areshell(shell))
+	if (!checkshell(shell))
 		shell = _PATH_BSHELL;
 	proc_send(c->peer, MSG_SHELL, -1, shell, strlen(shell) + 1);
 
diff --git a/usr.bin/tmux/spawn.c b/usr.bin/tmux/spawn.c
index 6cbd837c14b..915640f2e8e 100644
--- a/usr.bin/tmux/spawn.c
+++ b/usr.bin/tmux/spawn.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: spawn.c,v 1.15 2020/03/02 08:30:30 nicm Exp $ */
+/* $OpenBSD: spawn.c,v 1.16 2020/03/17 11:10:12 nicm Exp $ */
 
 /*
  * Copyright (c) 2019 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -320,7 +320,7 @@ spawn_pane(struct spawn_context *sc, char **cause)
 	/* Then the shell. If respawning, use the old one. */
 	if (~sc->flags & SPAWN_RESPAWN) {
 		tmp = options_get_string(s->options, "default-shell");
-		if (*tmp == '\0' || areshell(tmp))
+		if (!checkshell(tmp))
 			tmp = _PATH_BSHELL;
 		free(new_wp->shell);
 		new_wp->shell = xstrdup(tmp);
diff --git a/usr.bin/tmux/tmux.c b/usr.bin/tmux/tmux.c
index 576409c0bd1..b75d851d381 100644
--- a/usr.bin/tmux/tmux.c
+++ b/usr.bin/tmux/tmux.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tmux.c,v 1.193 2020/03/12 09:26:34 nicm Exp $ */
+/* $OpenBSD: tmux.c,v 1.194 2020/03/17 11:10:12 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -49,8 +49,8 @@ const char	*shell_command;
 static __dead void	 usage(void);
 static char		*make_label(const char *, char **);
 
+static int		 areshell(const char *);
 static const char	*getshell(void);
-static int		 checkshell(const char *);
 
 static __dead void
 usage(void)
@@ -79,7 +79,7 @@ getshell(void)
 	return (_PATH_BSHELL);
 }
 
-static int
+int
 checkshell(const char *shell)
 {
 	if (shell == NULL || *shell != '/')
@@ -91,7 +91,7 @@ checkshell(const char *shell)
 	return (1);
 }
 
-int
+static int
 areshell(const char *shell)
 {
 	const char	*progname, *ptr;
diff --git a/usr.bin/tmux/tmux.h b/usr.bin/tmux/tmux.h
index 188e7ae5557..4913274c9d6 100644
--- a/usr.bin/tmux/tmux.h
+++ b/usr.bin/tmux/tmux.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: tmux.h,v 1.958 2020/03/16 06:12:43 nicm Exp $ */
+/* $OpenBSD: tmux.h,v 1.959 2020/03/17 11:10:12 nicm Exp $ */
 
 /*
  * Copyright (c) 2007 Nicholas Marriott <nicholas.marriott@gmail.com>
@@ -1771,7 +1771,7 @@ extern const char	*socket_path;
 extern const char	*shell_command;
 extern int		 ptm_fd;
 extern const char	*shell_command;
-int		 areshell(const char *);
+int		 checkshell(const char *);
 void		 setblocking(int, int);
 const char	*find_cwd(void);
 const char	*find_home(void);