Adding checks for fd omission

Adding function check_fds to new file fd.c. The function check_fds
should be called in every setuid/setgid program.

Co-developed-by: Alejandro Colomar <alx@kernel.org>

src/chage.c

@@ -768,13 +768,12 @@ int main (int argc, char **argv)
 	gid_t rgid;
 	const struct passwd *pw;
 
-	/*
-	 * Get the program name so that error messages can use it.
-	 */
+	sanitize_env ();
+	check_fds ();
+
 	log_set_progname(Prog);
 	log_set_logfd(stderr);
 
-	sanitize_env ();
 	(void) setlocale (LC_ALL, "");
 	(void) bindtextdomain (PACKAGE, LOCALEDIR);
 	(void) textdomain (PACKAGE);

src/chfn.c

@@ -620,10 +620,12 @@ int main (int argc, char **argv)
 	char                 *user;
 	const struct passwd  *pw;
 
+	sanitize_env ();
+	check_fds ();
+
 	log_set_progname(Prog);
 	log_set_logfd(stderr);
 
-	sanitize_env ();
 	(void) setlocale (LC_ALL, "");
 	(void) bindtextdomain (PACKAGE, LOCALEDIR);
 	(void) textdomain (PACKAGE);

src/chsh.c

@@ -472,6 +472,7 @@ int main (int argc, char **argv)
 	const struct passwd *pw;	/* Password entry from /etc/passwd   */
 
 	sanitize_env ();
+	check_fds ();
 
 	log_set_progname(Prog);
 	log_set_logfd(stderr);

src/expiry.c

@@ -125,11 +125,12 @@ int main (int argc, char **argv)
 	struct passwd *pwd;
 	struct spwd *spwd;
 
+	sanitize_env ();
+	check_fds ();
+
 	log_set_progname(Prog);
 	log_set_logfd(stderr);
 
-	sanitize_env ();
-
 	/*
 	 * Start by disabling all of the keyboard signals.
 	 */

src/gpasswd.c

@@ -930,6 +930,8 @@ int main (int argc, char **argv)
 #endif
 
 	sanitize_env ();
+	check_fds ();
+
 	(void) setlocale (LC_ALL, "");
 	(void) bindtextdomain (PACKAGE, LOCALEDIR);
 	(void) textdomain (PACKAGE);

src/newgrp.c

@@ -390,6 +390,9 @@ int main (int argc, char **argv)
 #ifdef WITH_AUDIT
 	audit_help_open ();
 #endif
+
+	check_fds ();
+
 	(void) setlocale (LC_ALL, "");
 	(void) bindtextdomain (PACKAGE, LOCALEDIR);
 	(void) textdomain (PACKAGE);

src/passwd.c

@@ -728,6 +728,7 @@ int main (int argc, char **argv)
 	const struct spwd *sp;	/* Shadow file entry for user   */
 
 	sanitize_env ();
+	check_fds ();
 
 	log_set_progname(Prog);
 	log_set_logfd(stderr);

src/su.c

@@ -1007,6 +1007,8 @@ int main (int argc, char **argv)
 	int ret;
 #endif				/* USE_PAM */
 
+	check_fds ();
+
 	(void) setlocale (LC_ALL, "");
 	(void) bindtextdomain (PACKAGE, LOCALEDIR);
 	(void) textdomain (PACKAGE);