sysprep: add Kerberos keytab file removal

This new operation removes the Kerberos /etc/krb5.keytab file from the
guest.

Thanks to Christian Heimes and François Cami for the hints.

Related to RHBZ#1789592.

(cherry picked from commit faa5d8507f)

sysprep/Makefile.am

@@ -45,6 +45,7 @@ operations = \
 	fs_uuids \
 	ipa_client \
 	kerberos_data \
+	kerberos_hostkeytab \
 	lvm_uuids \
 	logfiles \
 	machine_id \

sysprep/sysprep_operation_kerberos_hostkeytab.ml

@@ -0,0 +1,38 @@
+(* virt-sysprep
+ * Copyright (C) 2020 Red Hat Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *)
+
+open Sysprep_operation
+open Common_gettext.Gettext
+
+module G = Guestfs
+
+let kerberos_hostkeytab_perform (g : Guestfs.guestfs) root side_effects =
+  let typ = g#inspect_get_type root in
+  if typ <> "windows" then (
+    (try g#rm "/etc/krb5.keytab" with G.Error _ -> ())
+  )
+
+let op = {
+  defaults with
+    name = "kerberos-hostkeytab";
+    enabled_by_default = true;
+    heading = s_"Remove the Kerberos host keytab file in the guest";
+    perform_on_filesystems = Some kerberos_hostkeytab_perform;
+}
+
+let () = register_operation op