I'm a network guy, and I do quite a bit of consulting work for various companies. I have a customer in particular who (prior to this) wasusing a very out-of-date Cisco ACS Server, and couldn't afford the renewal/licensing fees to bring it uptodate. They are using Microsoft's Active Directory on Windows Server 2000 as the primary database for all identities/passwords.

The goals of this configuration are:

1. Provide AAA for administrative access to network devices (mostly, SSH access to Cisco routers/switches/firewalls)
2. Provide AAA for 802.11 WLAN users who are using Windows XP and "Wireless Zero" clients. (Cisco 1231 series access points)
3. Provide AAA for VPN Users who use cisco Secure VPN client from remote locations (cisco 3000 series concentrators)

The freeradius server itself will run on a CentOS 5.4 Linux box. The company doesn't like "make install" application installs (nor do I), so I simply grabbed the SRPM from the Fedora project's KOJI build server for the latest freeradius, and built it. This process is outside the scope of this particular posting, as I want to focus on Freeradius itself.

The Fedora spec file builds multiple binary packages that you can install based on what you want to do with freeradius. These are the packages I'm using:

freeradius-utils-2.1.8-2
freeradius-2.1.8-2
freeradius-ldap-2.1.8-2

The company has one Active Directory forest, and one subdomain. Users exist under both. So, for this configuration, we'll call the primary zone COMPANY.COM and SUB.COMPANY.COM. Both domains must be queried for authorization & authentication. The following rules apply for access:

1. User must exist within the AD forest. (as defined by my LDAP search parameters)
2. User must be a member of a particular group (defined by the Users file) for certain types of access:
  a) For administrative access to network device, the user must be a member of the group networkteam.
  b) Access to use the VPN, user must be a member of the group vpnusers.
  c) Access to the Wireless network, user must be a member of group wifiusers.

VPN and Network-Admin users achieve both Authorization and Authentication using nothing more than the rlm_ldap module. Wireless users do not use ldap at all, but instead, they use the eap and mschap modules. The mschap module is configured to use ntlm_auth which requires samba's winbind to be configured on the backend.

It took me some time (and I will not admit how much time) to figure out how to make this all work. I blame most of this on the fact that freeradius has been around a long time, and as result there's lots of obsolete documentation out there for google to find. I believe this configuration uses mostly uptodate syntax, however I'm always interested in advice on improvements.

Interestingly, this process gave me quite a case of dejavu. I wrote a combination tacacs/radius server WAY back when the Livingston Portmaster 2 series was king of dialup. Many sers on the livingston mailing list used my source code. This really made me feel old. :(

Anyway, on to the good stuff:

Annoyances:

1. Cisco does not support command accounting via Radius. Only Tacacs. Why? They want you to buy ACS ! Sorry Cisco, I love ya, but.. cmon!

2. Cisco PIX/ASA do not support radius for command authorization. So, you have to type 'enable' and your AD account password AGAIN.

3. Cisco 1231-series access points running IOS 12.3(8)JED or earlier do not include NAS-Port-Type in subsequent password attempts for SSH access. So, you only get one shot at typing your password right when you SSH for admin access into a WAP. It'll ask you for your password again, and it'll try to get approval from your Radius server, however, it will not include the port type in the request. So freeradius will not classify the request in the proper huntgroup. Unfortunately, you may think you just keep fat fingering your password, so you just keep trying. This will eventually get your AD account locked and you'll have to bug the windows guys to re-enable it. :)

4. Cisco 3000 platform does not support AAA for admin access.. again, only with tacacs. I know, I know, this platform is OLD, but... you have to admit, it has to be one of the most reliable platforms cisco has ever sold. It's hard to say goodbye.

radiusd.conf

---------------------------------------------------------------------------------------------

# freeradius config for a typical company using Active Directory for password management

# George Shearer (doc at lame dot org)

# Primary uses:

# 1. AAA for admin access to network devices (ldap)

# 2. AAA for user access to 802.11 Wireless Networks (WPA2-Enterprise / EAP-PEAP / EAP-MSCHAPv2)

# 3. AAA for remote user access to VPN (ldap)

name = radiusd

# Locations

prefix = /usr

exec_prefix = /usr

sysconfdir = /etc

localstatedir = /var

sbindir = /usr/sbin

logdir = ${localstatedir}/log/radius

raddbdir = ${sysconfdir}/raddb

radacctdir = ${logdir}/radacct

confdir = ${raddbdir}

run_dir = ${localstatedir}/run/${name}

db_dir = ${raddbdir}

libdir = /usr/lib/freeradius

pidfile = ${run_dir}/${name}.pid

# Security

#chroot = /path/to/chroot/directory

user = radiusd

group = radiusd

security {

max_attributes = 200

reject_delay = 1

status_server = yes

}

# Network

hostname_lookups = yes

proxy_requests = no

listen {

type = auth

ipaddr = ip-addr-of-eth0

port = 1812

}

listen {

type = acct

ipaddr = ip-addr-of-eth0

port = 1813

}

listen {

type = control

socket = ${run_dir}/${name}.sock

mode = ro

}

# Performance

max_request_time = 10

cleanup_delay = 5

max_requests = 1024

allow_core_dumps = no

regular_expressions = yes

extended_expressions = yes

thread pool {

start_servers = 5

max_servers = 15

min_spare_servers = 3

max_spare_servers = 5

max_requests_per_server = 0

}

# Logging

log {

destination = syslog

syslog_facility = authpriv

stripped_names = no

auth = yes

auth_badpass = yes

auth_goodpass = no

}

# freeradius modules

modules {

# Create unique acct ID's per session -- so tell network devices to use common id's and let radiusd handle

acct_unique {

key = "User-Name, Acct-Session-Id, NAS-IP-Address, Client-IP-Address, NAS-Port"

}

preprocess {

huntgroups = ${confdir}/huntgroups

}

detail {

detailfile = ${radacctdir}/%{Huntgroup-Name}/detail-%Y%m%d

detailperm = 0600

header = "%t"

}

files {

usersfile = ${confdir}/users

acctusersfile = ${confdir}/acct_users

compat = no

}

ldap {

server = "ip-addr-of-domain-contoller"

port = 3268

# Global Catalog port not LDAP. This allows combined searches of both SUB.MYCOMPANY.COM and MYCOMPANY.COM

identity = "CN=myqueryacct,OU=System Accounts,DC=mycompany,DC=com"

password = "mypassword"

basedn = "DC=mycompany,DC=com"

filter = "(&(objectCategory=person)(sAMAccountName=%{%{Stripped-User-Name}:-%{User-Name}}))"

groupname_attribute = "cn"

groupmembership_filter = "(&(objectClass=group)(member=%{control:Ldap-UserDn}))"

groupmembership_attribute = memberOf

ldap_connections_number = 3

timeout = 4

timelimit = 3

net_timeout = 1

directory_mappings = ${confdir}/ldap.attrmap

}

eap {

default_eap_type = peap

timer_expire = 60

max_sessions = 500

ignore_unknown_eap_types = no

tls {

cert_dir = ${confdir}/certs

rsa_key_length = 2048

dh_key_length = 2048

private_key_password = password-for-my-encrypted-key

private_key_file = ${cert_dir}/combined-cert-and-key-file.pem

certificate_file = ${private_key_file}

CA_file = ${cert_dir}/my-ca-cert-file.pem

dh_file = ${cert_dir}/dh

random_file = ${cert_dir}/random

fragment_size = 1024

include_length = yes

cipher_list = "DEFAULT"

cache {

enable = yes

lifetime = 24

max_entries = 500

}

peap {

default_eap_type = mschapv2

}

mschapv2 {

}

mschap {

use_mppe = yes

require_encryption = yes

require_strong = yes

with_ntdomain_hack = yes

ntlm_auth = "/usr/bin/ntlm_auth --request-nt-key --username=%{%{mschap:User-Name}:-None} --domain=%{%{mschap:NT-Domain}:-EDLENDING} --challenge=%{%{mschap:Challenge}:-00} --nt-response=%{%{mschap:NT-Response}:-00} --require-membership-of=wifiusers"

}

radutmp {

filename = ${logdir}/radutmp

username = %{%{Stripped-User-Name}:-%{User-Name}}

case_sensitive = yes

check_with_nas = yes

perm = 0600

}

realm ntdomain {

format = prefix

delimiter = "\\"

}

instantiate {

}

authorize {

preprocess

eap {

ok = return

updated = return

}

# The eap {} stuff above prevents your ldap server from being used for wireless users. Since we handle this via ntlm, no need to bug ldap.

# also, the ntdomain stuff isnt even needed because the mschap module has variables to do the stripping built in..

ntdomain

files

ldap

}

authenticate {

Auth-Type LDAP {

ldap

}

Auth-Type MS-CHAP {

mschap

}

eap

}

preacct {

preprocess

update request {

NAS-Port = 1

# Cisco ASA's annoyingly do not include NAS-Port for administrative logins. This breaks radwho. The

# above statement forces Nas-Port to be '1' if it doesn't already exist.

}

ntdomain

acct_unique

}

accounting {

detail

radutmp

}

session {

radutmp

}

# Realms (domains)

realm MYCOMPANY {

authhost = LOCAL

accthost = LOCAL

type = radius

}

realm SUB {

authhost = LOCAL

accthost = LOCAL

type = radius

}

realm NULL {

authhost = LOCAL

accthost = LOCAL

type = radius

realm = MYCOMPANY

}

# Include our clients

$INCLUDE clients.conf

---------------------------------------------------------------------------------------------

huntgroups

# All devices that network-admins want to log into for administrative access

# Cisco sends "Virtual" for type on most things I've tried for SSH access

network-admin NAS-IP-Address == ipaddr1, NAS-Port-Type == "Virtual"

network-admin NAS-IP-Address == ipaddr2, NAS-Port-Type == "Virtual"

network-admin NAS-IP-Address == ipaddr3, NAS-Port-Type == "Virtual"

network-admin NAS-IP-Address == ipaddr4, NAS-Port-Type == "Virtual"

# Cisco 1200 series WAPs

# Since I handle AAA for wireless via ntlm_auth (not LDAP), this group isnt even necessary

# However you could expand upon my config and use this group to create a seperate

# accounting file, or various other uses.

wireless NAS-IP-Address == ipaddr1, NAS-Port-Type == "Wireless-802.11"

wireless NAS-IP-Address == ipaddr2, NAS-Port-Type == "Wireless-802.11"

wireless NAS-IP-Address == ipaddr3, NAS-Port-Type == "Wireless-802.11"

# Cisco 3000 Concentrators

# These also send "VirtuaL" as type for users connecting via IPsec. Unfortunately,

# the 3000 platform does not support radius AAA for administrative access :(

vpn NAS-IP-Address == ipaddr1, NAS-Port-Type == "Virtual"

vpn NAS-IP-Address == ipaddr2, NAS-Port-Type == "Virtual"

---------------------------------------------------------------------------------------------

users

# this 'locally managed' account matches the same account thats in the local configs on the devices

# various scripts use this account for things like downloading configs or whatever. And its not in

# active directory. It also has a limited security level.

admin Huntgroup-Name == "network-admin", Cleartext-Password := "localadminaccountpw"

Service-Type := NAS-Prompt-User,

cisco-avpair := "shell:priv-lvl=2"

# This drops all users who are a member of the 'networkteam' group right into an "enabled" prompt

# Unfortunately, PIX/ASA's do not support this cisco-avpair on Radius, so you'll still type 'enable'

# but when you're asked for a password, you'll give your AD account password again as opposed to

# the real enable password. The only time you should need the real enable password for any device

# is when the radius server is down

DEFAULT Huntgroup-Name == "network-admin", Ldap-Group == "networkteam"

Service-Type := NAS-Prompt-User,

cisco-avpair := "shell:priv-lvl=15",

Auth-Type := LDAP

DEFAULT Huntgroup-Name == "vpn", Ldap-Group == "vpnusers"

Auth-Type := LDAP

DEFAULT Auth-Type := Reject

Reply-Message := "Access Denied. Your attempt has been logged.",

---------------------------------------------------------------------------------------------

Cisco IOS based device config: (relevant parts, anyway)

aaa new-model

aaa authentication login networkteam group radius local-case

aaa authentication login wifi-access group radius

aaa authorization exec default group radius local

aaa accounting session-duration ntp-adjusted

aaa accounting exec default start-stop group radius

aaa accounting network default start-stop group radius

aaa session-id common

! Obviously you dont need the wireless stuff for non-access points

dot11 ssid OURSSID

authentication open eap wifi-access

authentication key-management wpa

accounting default

! The "accounting-default" statement is what causes IOS to send accounting packets for that SSID

radius-server host my-radius-server auth-port 1812 acct-port 1813 key myradiuskey

line con 0

line vty 0 15

---------------------------------------------------------------------------------------------

Cisco ASA/PIX config:

username admin password whatever

aaa-server radius protocol radius

max-failed-attempts 3

aaa-server radius (INSIDE) host my-radius-server

timeout 3

key slxradkey2010

authentication-port 1812

accounting-port 1813

aaa authentication ssh console radius LOCAL

aaa authentication enable console radius LOCAL

aaa authentication serial console radius LOCAL

aaa authentication telnet console radius LOCAL

aaa authentication http console radius LOCAL

aaa accounting ssh console radius

aaa accounting telnet console radius

aaa accounting serial console radius