Honour umask, let temporary key files inherit original's permissions.
[tinc] / doc / sample-config /
drwxr-xr-x   ..
drwxr-xr-x - hosts
-rw-r--r-- 48 rsa_key.priv
-rw-r--r-- 76 tinc-down
-rw-r--r-- 506 tinc-up
-rw-r--r-- 700 tinc.conf