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. */