Apache Reference: http_core, Require
Require User and Group Authentication
Syntax: Require type [uid-or-gid [...]]
Example: Require group friends
Since: Apache 1.0
This directive selects which authenticated users or groups may access a protected directory. The following syntax variants are allowed: ``
require useruid [uid ...]'', which means that only the named users can access the directory; ``
require groupgid [gid ...]'', which means that only users in the named groups can access the directory; and ``
require== valid==-user'', which means that all valid users can access the directory.
If this directive appears in a <Limit> section, then it restricts access to the named HTTP methods; otherwise, it restricts access for all methods. Require must be accompanied by AuthName and AuthType directives, as well as directives such as AuthUserFile and AuthGroupFile (to define users and groups), to work correctly.