TACACS+ Installation and Configuration

Summary

This document provides the steps necessary to complete the download and configuration of the TACACS+ CentOS 7 VM.

The TACACS+ configuration already contains configuration for the most common use cases including AD/LDAP integration, privilege levels and per-command authorization. The configuration can be customized to meet the specific requirements of the environment.

TACACS+ OVA Download

Navigate to the URL below and initiate the download of the TACACS+ CentOS 7 OVA. Import the OVA into your existing ESXi infrastructure. The OVA was built on ESXi6.5 and VM Hardware Version 13.

https://nac-downloads.opswat.com/IE/tacacs/OPSWAT-TACACS+-VM.ova

The VM image requires 4Gig of dedicated memory with 40Gig thin provisioned storage partition and 2 vCPUs.

TACACS+ VM Configuration

The default username and password are below:

user = root

password = P@55w0rD

It is highly recommended that you change the default password. To do this type passwd and hit enter. You will be prompted to type in the new password.

Configure networking:

# vi /etc/sysconfig/network-scripts/ifcfg-ens160

Change the following fields to the desired setting for your network

IPADDR=x.x.x.x

NETMASK=x.x.x.x

GATEWAY=x.x.x.x

DNS1=x.x.x.x

DNS2=x.x.x.x

# systemctl restart network.service

Configure the desired hostname for the server:

# hostnamectl set-hostname hostname.your.domain

Reboot for the hostname change to take effect.

TACACS+ Configuration - AD/LDAP

# vi /usr/local/etc/tac_plus.cfg

#!/usr/local/sbin/tac_plus

id = spawnd {

listen = {

port = 49

}

spawn = {

instances min = 1

instances max = 10

}

background = yes

}

id = tac_plus {

access log = /var/log/tac_plus/access/%Y%m%d.log

accounting log = /var/log/tac_plus/acct/%Y%m%d.log

authentication log = /var/log/tac_plus/authentication/%Y%m%d.log

authorization log = /var/log/tac_plus/authorization/%Y%m%d.log

#debug = ALL

mavis module = external {

script out = {

# Require group membership:

if (undef($TACMEMBER) && $RESULT == ACK) set $RESULT = NAK

# Don.t cache passwords:

if ($RESULT == ACK) set $PASSWORD_ONESHOT = 1

}

setenv LDAP_SERVER_TYPE = "microsoft"

###################################################

TACACS+ Configuration - Privilege Level Concept

#################################################################################

# The following can be used to assign a privilege level to users based on group #

# Note: AD groups need to be prefaced with “TACACS” when created on the AD #

# server, e.g. TACACSNetEngPriv in AD, NetEngPriv in tac_plus.cfg. #

#################################################################################

group = NetEngPriv {

enable = login

default service = permit

service = shell {

default command = permit

default attribute = permit

set priv-lvl = 15

}

group = NetAdminPriv {

default service = permit

service = shell {

default command = permit

default attribute = permit

TACACS+ Configuration - Per Command Authorization

##################################################################################

# As an alternative to privilege levels, the following configuration can be used #

# to assign specific commands that a user is allowed to issue #

# Note: Privilege level defaults to 1 #

##################################################################################

group = NetAdminCmd {

default service = deny

service = shell {

default command = deny

default attribute = deny

cmd = ping { permit .* }

cmd = show { permit .* }

cmd = traceroute { permit .* }

cmd = terminal { permit [length].* }

cmd = exit

}

TACACS+ Configuration - Validation

Once the desired changes have been made to the configuration, the tac_plus configuration will need to be verified and the service restarted in order for the changes to take effect.

################################################################################

# If changes have been made to this file, the tac_plus service must be #

# restarted in order for them to take effect #

# #

# Pre-flight check - /usr/local/sbin/tac_plus -P /usr/local/etc/tac_plus.cfg #

# Make sure there are no errors returned #

# #

# Restart the service #

# systemctl restart tac_plus.service #

# #

# Make sure that the service is running #

# systemctl status tac_plus.service –l #

################################################################################

[root@tacacs-vm ~]# /usr/local/sbin/tac_plus -P /usr/local/etc/tac_plus.cfg

[root@tacacs-vm ~]# systemctl restart tac_plus.service

[root@tacacs-vm ~]# systemctl status tac_plus.service –l

● tac_plus.service - TACACS+ Service

Loaded: loaded (/etc/systemd/system/tac_plus.service; enabled; vendor preset:

disabled)

Active: active (running) since Tue 2017-05-30 17:57:09 EDT; 12s ago

Main PID: 5709 (tac_plus)

CGroup: /system.slice/tac_plus.service

├─5709 tac_plus: 0 connections, accepting up to 600 more

├─5710 tac_plus: 0 connections

└─5711 perl /usr/local/lib/mavis/mavis_tacplus_ldap.pl

May 30 17:57:09 tacacs-vm.impulse.com systemd[1]: Started TACACS+ Service.

May 30 17:57:09 tacacs-vm.impulse.com systemd[1]: Starting TACACS+ Service...

May 30 17:57:09 tacacs-vm.impulse.com tac_plus[5709]: startup (version 201705210930)

May 30 17:57:09 tacacs-vm.impulse.com tac_plus[5709]: epoll event notification mechanism

Device Configuration - Cisco Example

Note – In the event the device is unable to connect to the TACACS+ server, the device will resort back to using the local access credentials after a default or specified time-out period.

conf t

aaa new-model

aaa authentication login default local group tacacs+

aaa authentication login telnet group tacacs+ local

aaa authentication login console group tacacs+ local

aaa authentication enable default group tacacs+ enable

aaa authorization exec default group tacacs+ local

aaa authorization commands 0 default group tacacs+ local

aaa authorization commands 1 default group tacacs+ local

aaa authorization commands 15 default group tacacs+ local

aaa accounting update newinfo

aaa accounting exec default start-stop group tacacs+