[PATCH weston v2 2/2] weston-launch: Allow the user to use her login shell

[Quentin Glidic]

From: Quentin Glidic <sardemff7+git at sardemff7.net>

This avoids the need to maintain two parallel shell profile files for
users with a compatible shell (at least bash, sh and zsh are).

There is no major security issue here, as the shell is the one returned
from the password database, and thus is retricted by /etc/shells (or
root override).

Signed-off-by: Quentin Glidic <sardemff7+git at sardemff7.net>
---

v2: Added some rationale to the commit message

 src/weston-launch.c | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/src/weston-launch.c b/src/weston-launch.c
index 140fde1..c206094 100644
--- a/src/weston-launch.c
+++ b/src/weston-launch.c
@@ -108,6 +108,7 @@ struct weston_launch {
 	pid_t child;
 	int verbose;
 	char *new_user;
+	int use_user_shell;
 };
 
 union cmsg_data { unsigned char b[4]; int fd; };
@@ -613,7 +614,10 @@ setup_session(struct weston_launch *wl, char **child_argv)
 	 * We open a new session, so it makes sense
 	 * to run a new login shell
 	 */
-	child_argv[0] = "/bin/sh";
+	if (wl->use_user_shell)
+		child_argv[0] = wl->pw->pw_shell;
+	else
+		child_argv[0] = "/bin/sh";
 	child_argv[1] = "-l";
 	child_argv[2] = "-c";
 	child_argv[3] = BINDIR "/weston \"$@\"";
@@ -675,10 +679,11 @@ static void
 help(const char *name)
 {
 	fprintf(stderr, "Usage: %s [args...] [-- [weston args..]]\n", name);
-	fprintf(stderr, "  -u, --user      Start session as specified username\n");
-	fprintf(stderr, "  -t, --tty       Start session on alternative tty\n");
-	fprintf(stderr, "  -v, --verbose   Be verbose\n");
-	fprintf(stderr, "  -h, --help      Display this help message\n");
+	fprintf(stderr, "  -u, --user              Start session as specified username\n");
+	fprintf(stderr, "  -s, --use-user-shell    Use the user login shell (from PAM) instead of /bin/sh, only has effect with --user\n");
+	fprintf(stderr, "  -t, --tty               Start session on alternative tty\n");
+	fprintf(stderr, "  -v, --verbose           Be verbose\n");
+	fprintf(stderr, "  -h, --help              Display this help message\n");
 }
 
 int
@@ -688,11 +693,12 @@ main(int argc, char *argv[])
 	int i, c;
 	char *tty = NULL;
 	struct option opts[] = {
-		{ "user",    required_argument, NULL, 'u' },
-		{ "tty",     required_argument, NULL, 't' },
-		{ "verbose", no_argument,       NULL, 'v' },
-		{ "help",    no_argument,       NULL, 'h' },
-		{ 0,         0,                 NULL,  0  }
+		{ "user",           required_argument, NULL, 'u' },
+		{ "use-user-shell", no_argument,       NULL, 's' },
+		{ "tty",            required_argument, NULL, 't' },
+		{ "verbose",        no_argument,       NULL, 'v' },
+		{ "help",           no_argument,       NULL, 'h' },
+		{ 0,                0,                 NULL,  0  }
 	};
 
 	memset(&wl, 0, sizeof wl);
@@ -704,6 +710,9 @@ main(int argc, char *argv[])
 			if (getuid() != 0)
 				error(1, 0, "Permission denied. -u allowed for root only");
 			break;
+		case 's':
+			wl.use_user_shell = 1;
+			break;
 		case 't':
 			tty = optarg;
 			break;
-- 
2.8.3