libbb/login/su: do not sanitize shell name twice

function                                             old     new   delta
setup_environment                                    191     205     +14
login_main                                          1002     987     -15
su_main                                              474     458     -16
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/2 up/down: 14/-31)            Total: -17 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

3 files changed, 7 insertions, 14 deletions

diff --git a/libbb/setup_environment.c b/libbb/setup_environment.c
index a95fbc5bf..73229ca6c 100644
--- a/libbb/setup_environment.c
+++ b/libbb/setup_environment.c
@@ -32,6 +32,9 @@
 
 void FAST_FUNC setup_environment(const char *shell, int flags, const struct passwd *pw)
 {
+	if (!shell || !shell[0])
+		shell = DEFAULT_SHELL;
+
 	/* Change the current working directory to be the home directory
 	 * of the user */
 	if (chdir(pw->pw_dir)) {
diff --git a/loginutils/login.c b/loginutils/login.c
index 952b3aadd..028a099b6 100644
--- a/loginutils/login.c
+++ b/loginutils/login.c
@@ -198,7 +198,6 @@ int login_main(int argc UNUSED_PARAM, char **argv)
 	};
 	char *fromhost;
 	char username[USERNAME_SIZE];
-	const char *shell;
 	int run_by_root;
 	unsigned opt;
 	int count = 0;
@@ -391,10 +390,7 @@ int login_main(int argc UNUSED_PARAM, char **argv)
 		run_login_script(pw, full_tty);
 
 	change_identity(pw);
-	shell = pw->pw_shell;
-	if (!shell || !shell[0])
-		shell = DEFAULT_SHELL;
-	setup_environment(shell,
+	setup_environment(pw->pw_shell,
 			(!(opt & LOGIN_OPT_p) * SETUP_ENV_CLEARENV) + SETUP_ENV_CHANGEENV,
 			pw);
 
@@ -442,7 +438,7 @@ int login_main(int argc UNUSED_PARAM, char **argv)
 	signal(SIGINT, SIG_DFL);
 
 	/* Exec login shell with no additional parameters */
-	run_shell(shell, 1, NULL, NULL);
+	run_shell(pw->pw_shell, 1, NULL, NULL);
 
 	/* return EXIT_FAILURE; - not reached */
 }
diff --git a/loginutils/su.c b/loginutils/su.c
index db303af6d..72dd0f06f 100644
--- a/loginutils/su.c
+++ b/loginutils/su.c
@@ -114,20 +114,14 @@ int su_main(int argc UNUSED_PARAM, char **argv)
 		opt_shell = getenv("SHELL");
 	}
 
-	/* Make sure pw->pw_shell is non-NULL.  It may be NULL when NEW_USER
-	 * is a username that is retrieved via NIS (YP), that doesn't have
-	 * a default shell listed.  */
-	if (!pw->pw_shell || !pw->pw_shell[0])
-		pw->pw_shell = (char *)DEFAULT_SHELL;
-
 #if ENABLE_FEATURE_SU_CHECKS_SHELLS
-	if (opt_shell && cur_uid != 0 && restricted_shell(pw->pw_shell)) {
+	if (opt_shell && cur_uid != 0 && pw->pw_shell && restricted_shell(pw->pw_shell)) {
 		/* The user being su'd to has a nonstandard shell, and so is
 		 * probably a uucp account or has restricted access.  Don't
 		 * compromise the account by allowing access with a standard
 		 * shell.  */
 		bb_error_msg("using restricted shell");
-		opt_shell = NULL;
+		opt_shell = NULL; /* ignore -s PROG */
 	}
 	/* else: user can run whatever he wants via "su -s PROG USER".
 	 * This is safe since PROG is run under user's uid/gid. */