--- sh-utils-2.0/src/su.c.nostdin	Sat Aug 28 14:35:51 1999
+++ sh-utils-2.0/src/su.c	Sat Aug 28 14:38:43 1999
@@ -316,7 +316,6 @@
 correct_password (const struct passwd *pw)
 {
 #ifdef USE_PAM
-
   /* root always succeeds; this isn't an authentication question (no
    * extra privs are being granted) so it shouldn't authenticate with PAM.
    * However, we want to create the pam_handle so that proper credentials
@@ -325,6 +324,12 @@
   PAM_BAIL_P;
   if (getuid () == 0)
     return 1;
+
+  if (!isatty(0)) {
+       fprintf(stderr, "standard in must be a tty\n");
+       exit(1);
+  }
+
   retval = pam_authenticate(pamh, 0);
   PAM_BAIL_P;
   retval = pam_acct_mgmt(pamh, 0);