Lighttpd

If you use different userfile files for authenticating in different directories, you can attach each to the correct directory by using conditionals.

Let's say you have a /admin directory that authenticates with admin_users.txt file which is an htpasswd file.
You can set it up in the configuration file like this:

{{{
$HTTP["url"] =~ "^/admin/" {
auth.backend = "htpasswd"
auth.backend.htpasswd.userfile = "/http/admin_users.txt"
auth.require = ("/admin" => (
"method" => "basic",
"realm" => "admin",
"require" => "valid-user"
))
}
}}}

Now you need to setup directory /work/admin that authenticates with
work_users.txt. You can use this:

{{{
$HTTP["url"] =~ "^/work/admin/" {
auth.backend = "htpasswd"
auth.backend.htpasswd.userfile = "/http/work_users.txt"
auth.require = ("/work/admin" => (
"method" => "basic",
"realm" => "work_admin",
"require" => "valid-user"
))
}
}}}