ssh: enable empty password login for all users

Disabling password login for all users is unnecessary, as the virtme-ng
instance is intended solely for testing purposes.

In fact, enabling empty password for all users can be quite convenient
and does not pose a security risk, since all filesystem access is
ultimately handled by the host user (due to virtiofsd running as the
host user).

In particular, enabling empty password login eliminates the need for
managing ssh authorized keys, simplifying the configuration further.

Signed-off-by: Andrea Righi <arighi@nvidia.com>

src/main.rs

@@ -315,7 +315,7 @@ fn generate_shadow() -> io::Result<()> {
 
     for line in reader.lines() {
         if let Some((username, _)) = line?.split_once(':') {
-            writeln!(writer, "{}:!:::::::", username)?;
+            writeln!(writer, "{}::::::::", username)?;
         }
     }
     utils::do_mount(