MT#64527 ngcp-panel-create-keys: Fix race condition when creating TLS certs

We should not create and populate the TLS keys and certificate files
with the default permissions from open(), to then fix that up in a later
call. Instead use the specified permissions (even if they might get
restricted further by the current umask), and then we will possibly open
them up again when doing the chmod().

Spotted-by: Michael Prokop <mprokop@sipwise.com>
Change-Id: I810e041cc4038bdaed8a3335ca45009129c928de

tools_bin/ngcp-panel-create-keys

@@ -108,7 +108,9 @@ sub save_pem {
         path_mod => $path_mod,
         path_owner => $path_owner,
         path_group => $path_group);
-    open(my $fh, '>', $filename) or die "Could not open file '$filename': $!\n";
+
+    sysopen my $fh, $filename, O_WRONLY | O_CREAT, $mod
+        or die "Could not open file '$filename': $!\n";
     print $fh $data;
     close $fh;
     _chownmod($filename,$owner,$group,$mod);