userdel: --force: Allow the flag to be specified twice, for more gran…

…ularity

Previously, with a single --force, one could only chose between not
forcing, and forcing (which could destroy one's system entirely).

Now one can pass --force, with only a small danger, to skip some checks,
and a double --force --force with the meaning of the previous --force,
which will possibly destroy the entire system.

Closes: <shadow-maint#1050>
Reported-by: Matthew Horsfall <wolfsage@gmail.com>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>

man/userdel.8.xml

@@ -79,7 +79,16 @@
 	  <para>
 	    This option forces the removal of the user account
 	    and any other requested actions,
-	    skipping any safety checks.
+	    skipping safety checks.
+	  </para>
+	  <para>
+	    If specified once,
+	    a user is removed
+	    even if it's still logged in,
+	    and its primary group is removed
+	    even if it's the primary group of another user.
+	    If specified twice,
+	    it skips all safety checks.
 	  </para>
 	  <para>
 	    <emphasis>Note:</emphasis> This option is dangerous and may leave

src/userdel.c

@@ -79,7 +79,7 @@ static uid_t user_id;
 static gid_t user_gid;
 static char *user_home;
 
-static bool fflg = false;
+static int fflg = 0;
 static bool rflg = false;
 #ifdef WITH_SELINUX
 static bool Zflg = false;
@@ -312,7 +312,7 @@ static void remove_usergroup (void)
 		return;
 	}
 
-	if (!fflg) {
+	if (fflg < 1) {
 		/*
 		 * Scan the passwd file to check if this group is still
 		 * used as a primary group.
@@ -832,7 +832,7 @@ static int remove_mailbox (void)
 		}
 	}
 
-	if (fflg) {
+	if (fflg >= 2) {
 		if (unlink (mailfile) != 0) {
 			fprintf (stderr,
 			         _("%s: warning: can't remove %s: %s\n"),
@@ -997,8 +997,8 @@ int main (int argc, char **argv)
 #endif				/* !WITH_SELINUX */
 		                         long_options, NULL)) != -1) {
 			switch (c) {
-			case 'f':	/* force remove even if not owned by user */
-				fflg = true;
+			case 'f':
+				fflg++;
 				break;
 			case 'h':
 				usage (E_SUCCESS);
@@ -1131,7 +1131,7 @@ int main (int argc, char **argv)
 	 * a cron job may be started on her behalf, etc.
 	 */
 	if ((prefix[0] == '\0') && !Rflg && user_busy (user_name, user_id) != 0) {
-		if (!fflg) {
+		if (fflg < 1) {
 #ifdef WITH_AUDIT
 			audit_logger (AUDIT_DEL_USER, Prog,
 			              "deleting user logged in",
@@ -1160,7 +1160,7 @@ int main (int argc, char **argv)
 			         _("%s: %s home directory (%s) not found\n"),
 			         Prog, user_name, user_home);
 			rflg = 0;
-		} else if ((0 == home_owned) && !fflg) {
+		} else if ((0 == home_owned) && fflg < 2) {
 			fprintf (stderr,
 			         _("%s: %s not owned by %s, not removing\n"),
 			         Prog, user_home, user_name);
@@ -1172,7 +1172,7 @@ int main (int argc, char **argv)
 
 #ifdef EXTRA_CHECK_HOME_DIR
 	/* This may be slow, the above should be good enough. */
-	if (rflg && !fflg) {
+	if (rflg && fflg < 2) {
 		struct passwd *pwd;
 		/*
 		 * For safety, refuse to remove the home directory if it