NAME
rlm_attr_filter - FreeRADIUS Module
DESCRIPTION
The rlm_attr_filter module exists for filtering certain attributes and
values in received ( or transmitted ) radius packets. It gives the
server a flexible framework to filter the attributes we send to or
receive from home servers or NASes. This makes sense, for example, in
an out-sourced dialup situation to various policy decisions, such as
restricting a client to certain ranges of Idle-Timeout or Session-
Timeout.
Filter rules are normally defined and applied on a per-realm basis,
where the realm is anything that is defined and matched based on the
configuration of the rlm_realm module. Filter rules can optionally be
applied using another attribute, by editing the key configuration for
this module.
In 2.0.1 and earlier versions, the "accounting" section filtered the
Accounting-Request, even though it was documented as filtering the
response. This issue has been fixed in version 2.0.2 and later
versions. The "preacct" section may now be used to filter Accounting-
Request packets. The "accounting" section now filters Accounting-
Response packets. Administrators using "attr_filter" in the
"accounting" section SHOULD move the reference to "attr_filter" from
"accounting" to "preacct".
The file that defines the attribute filtering rules follows a similar
syntax to the users file. There are a few differences however:
There are no check-items allowed other than the name of the key.
There can only be a single DEFAULT entry.
The rules for each entry are parsed to top to bottom, and an
attribute must pass *all* the rules which affect it in order to
make it past the filter. Order of the rules is important.
The operators and their purpose in defining the rules are as
follows:
= THIS OPERATOR IS NOT ALLOWED. If used, and warning message is
printed and it is treated as ==
:= Set, this attribute and value will always be placed in the
output A/V Pairs. If the attribute exists, it is overwritten.
== Equal, value must match exactly.
=* Always Equal, allow all values for the specified attribute.
!* Never Equal, disallow all values for the specified attribute.
( This is redundant, as any A/V Pair not explicitly permitted
will be dropped ).
!= Not Equal, value must not match.
>= Greater Than or Equal
<= Less Than or Equal
> Greater Than
< Less Than
If regular expressions are enabled the following operators are
also possible. ( Regular Expressions are included by default
unless your system doesn’t support them, which should be rare ).
The value field uses standard regular expression syntax.
=~ Regular Expression Equal
!~ Regular Expression Not Equal
See the default /etc/raddb/attrs for working examples of
sample rule ordering and how to use the different operators.
The configuration items are:
attrsfile
This specifies the location of the file used to load the filter
rules. This file is used to filter the accounting response,
packet before it is proxied, proxy response from the home
server, or our response to the NAS.
key Usually %{Realm} (the default). Can also be %{User-Name}, or
other attribute that exists in the request. Note that the
module always keys off of attributes in the request, and NOT in
any other packet.
SECTIONS
preacct
Filters Accounting-Request packets.
accounting
Filters Accounting-Response packets.
pre-proxy
Filters Accounting-Request or Access-Request packets prior to
proxying them.
post-proxy
Filters Accounting-Response, Access-Accept, Access-Reject, or
Access-Challenge responses from a home server.
authorize
Filters Access-Request packets.
post-auth
Filters Access-Accept or Access-Reject packets.
FILES
/etc/raddb/radiusd.conf /etc/raddb/attrs
SEE ALSO
radiusd(8), radiusd.conf(5)
AUTHOR
Chris Parker, cparker@segv.org
12 February 2008 rlm_attr_filter(5)