su: move restricted_shell into su.c (the only user)

function                                             old     new   delta
su_main                                              448     468     +20
buffer_fill_and_print                                179     196     +17
scriptreplay_main                                    205     208      +3
localcmd                                             275     277      +2
hash_find                                            233     234      +1
devmem_main                                          469     463      -6
install_main                                         724     716      -8
setusershell                                          11       -     -11
find_pair                                            187     169     -18
restricted_shell                                      49       -     -49
------------------------------------------------------------------------------
(add/remove: 0/3 grow/shrink: 5/3 up/down: 43/-92)            Total: -49 bytes

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

1 files changed, 18 insertions, 1 deletions

diff --git a/loginutils/su.c b/loginutils/su.c
index 6356631b8..af25655fd 100644
--- a/loginutils/su.c
+++ b/loginutils/su.c
@@ -8,6 +8,23 @@
 #include "libbb.h"
 #include <syslog.h>
 
+#if ENABLE_FEATURE_SU_CHECKS_SHELLS
+/* Return 1 if SHELL is a restricted shell (one not returned by
+   getusershell), else 0, meaning it is a standard shell.  */
+static int restricted_shell(const char *shell)
+{
+        char *line;
+
+        /*setusershell(); - getusershell does it itself*/
+        while ((line = getusershell()) != NULL) {
+                if (/* *line != '#' && */ strcmp(line, shell) == 0)
+                        return 0;
+        }
+        endusershell();
+        return 1;
+}
+#endif
+
 #define SU_OPT_mp (3)
 #define SU_OPT_l (4)
 
@@ -89,7 +106,7 @@ int su_main(int argc UNUSED_PARAM, char **argv)
                 opt_shell = getenv("SHELL");
 
 #if ENABLE_FEATURE_SU_CHECKS_SHELLS
-        if (opt_shell && cur_uid && restricted_shell(pw->pw_shell)) {
+        if (opt_shell && cur_uid != 0 && 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