Cisco Systems Configuring Cisco Secure ACS for Downloadable Access Lists

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Cisco ASA 5500 Series Configuration Guide using ASDM
Chapter41 Configuring AAA Rules for Network Access
Configuring Authorization for Network Access
In addition, the ASA signs the request with the Message-Authenticator attribute (IETF RADIUS
attribute 80).
4. After receipt of a RADIUS authentication request that has a username attribute that includes the
name of a downloadable access list, Cisco Secure ACS authenticates the request by checking the
Message-Authenticator attribute. If the Message-Authenticator attribute is missing or incorrect,
Cisco Secure ACS ignores the request. The presence of the Message-Authenticator attribute
prevents malicious use of a downloadable access list name to gain unauthorized network access. The
Message-Authenticator attribute and its use are defined in RFC 2869, RADIUS Extensions,
available at http://www.ietf.org.
5. If the access list required is less than approximately 4 KB in length, Cisco Secure ACS responds
with an access-accept message that includes the access list. The largest access list that can fit in a
single access-accept message is slightly less than 4 KB, because part of the message must be other
required attributes.
Cisco Secure ACS sends the downloadable access list in a cisco-av-pair RADIUS VSA. The access
list is formatted as a series of attribute-value pairs that each include an ACE and are numbered
serially:
ip:inacl#1=ACE-1
ip:inacl#2=ACE-2
.
.
.
ip:inacl#n=ACE-n
The following example is of an attribute-value pair:
ip:inacl#1=permit tcp 10.1.0.0 255.0.0.0 10.0.0.0 255.0.0.0
6. If the access list required is more than approximately 4 KB in length, Cisco Secure ACS responds
with an access-challenge message that includes a portion of the access list, formatted as described
previously, and a State attribute (IETF RADIUS attribute 24), which includes control data used by
Cisco Secure ACS to track the progress of the download. Cisco Secure ACS fits as many complete
attribute-value pairs into the cisco-av-pair RADIUS VSA as it can without exceeding the maximum
RADIUS message size.
The ASA stores the portion of the access list received and responds with another access-request
message that includes the same attributes as the first request for the downloadable access list, plus
a copy of the State attribute received in the access-challenge message.
This process repeats until Cisco Secure ACS sends the last of the access list in an access-accept
message.
Configuring Cisco Secure ACS for Downloadable Access Lists
You can configure downloadable access lists on Cisco Secure ACS as a shared profile component and
then assign the access list to a group or to an individual user.
The access list definition consists of one or more ASA commands that are similar to the extended
access-list command (see command reference), except without the following prefix:
access-list acl_name extended
The following example is a downloadable access list definition on Cisco Secure ACS version 3.3:
+--------------------------------------------+
| Shared profile Components |
| |
| Downloadable IP ACLs Content |