sulogin: remove suid paranoia code, explain why it's not necessary

function                                             old     new   delta
sulogin_main                                         325     270     -55

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

1 files changed, 9 insertions, 13 deletions

diff --git a/loginutils/sulogin.c b/loginutils/sulogin.c
index d2ac1f65d..33f078ae7 100644
--- a/loginutils/sulogin.c
+++ b/loginutils/sulogin.c
@@ -32,6 +32,14 @@ int sulogin_main(int argc UNUSED_PARAM, char **argv)
         struct passwd *pwd;
         const char *shell;
 
+        /* Note: sulogin is not a suid app. It is meant to be run by init
+         * for single user / emergency mode. init starts it as root.
+         * Normal users (potentially malisious ones) can only run it under
+         * their UID, therefore no paranoia here is warranted:
+         * $LD_LIBRARY_PATH in env, TTY = /dev/sda
+         * are no more dangerous here than in e.g. cp applet.
+         */
+
         logmode = LOGMODE_BOTH;
         openlog(applet_name, 0, LOG_AUTH);
 
@@ -47,18 +55,9 @@ int sulogin_main(int argc UNUSED_PARAM, char **argv)
                 dup(0);
         }
 
-        /* Malicious use like "sulogin /dev/sda"? */
-        if (!isatty(0) || !isatty(1) || !isatty(2)) {
-                logmode = LOGMODE_SYSLOG;
-                bb_error_msg_and_die("not a tty");
-        }
-
-        /* Clear dangerous stuff, set PATH */
-        sanitize_env_if_suid();
-
         pwd = getpwuid(0);
         if (!pwd) {
-                goto auth_error;
+                bb_error_msg_and_die("no password entry for root");
         }
 
         while (1) {
@@ -92,7 +91,4 @@ int sulogin_main(int argc UNUSED_PARAM, char **argv)
 
         /* Exec login shell with no additional parameters. Never returns. */
         run_shell(shell, 1, NULL, NULL);
-
- auth_error:
-        bb_error_msg_and_die("no password entry for root");
 }