/etc/freeradius/modules/chap is in freeradius 2.2.8+dfsg-0.1build2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 | # -*- text -*-
#
#  $Id$
# CHAP module
#
#  To authenticate requests containing a CHAP-Password attribute.
#
chap {
	# no configuration
}
 |