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Add new AAA - TACACS Lab topology (#48)

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* Add new AAA - TACACS Lab topology

This is a sample topology for exploring AAA TACACS.
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Hank Preston
2024-10-08 11:54:17 -04:00
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# Exploring AAA / TACACS Configuration for IOS
Simple topology for practicing AAA TACACS configuration in IOS.
![](topology.jpg)
## Starting Configuration
`rtr1` has the following configuration applied as startup configuration to enable inbound SSH from `desktop` that is locally authenticated.
```
ip domain name lab.intra
crypto key generate rsa general-keys modulus 2048
!
aaa new-model
!
username cisco priv 15 secret cisco
```
## Ensuring the serial / console leverages local authentication
To provide safety and fallback access to devices, we will force the console line to only use local admin accounts.
```
aaa authentication login CONSOLE local
aaa authorization console
aaa authorization exec CONSOLE local
!
line con 0
login authentication CONSOLE
authorization exec CONSOLE
!
```
## Configuring TACACS server as default AAA
Start by identitying the interface that TACACS packets should be sourced from. This is often important because TACACS servers typically only respond to known hosts/addresses.
```
ip tacacs source-interface Ethernet0/0
```
Now create the TACACS server entry for the server. Be sure to double check the "key" (secret) used for communications.
> Note: Be careful to NOT add an extra "space" after the key. This can cause problems on some platforms.
```
tacacs server aaa-server
address ipv4 192.168.0.10
key tacacs123
!
```
Create a `aaa group` that includes the TACACS server. In a production environment, you would typically have at least 2 TACASC servers configured for fallback.
```
aaa group server tacacs+ AAA-TACACS
server name aaa-server
!
```
Test that the TACACS server is responding successfully.
```
test aaa group tacacs+ tacadmin admin123 legacy
```
Configure the authentication, authorization, and accounting policies.
```
aaa authentication login default group AAA-TACACS local
aaa authorization exec default group AAA-TACACS local
!
aaa accounting exec default start-stop group ISE-TACACS
aaa accounting commands 1 default start-stop group AAA-TACACS
aaa accounting commands 15 default start-stop group AAA-TACACS
!
```
## Testing the configuration
Open the console for the `tacacs-server` and monitor the service "journal"
```
journalctl -fu tac_plus
```
Open the console for the `desktop` and attempt to connect to `rtr1` with SSH as the `tacadmin` user.
```
ssh tacadmin@192.168.0.1
```
After you log in, run a command to verify access.
```
show ip interface brief
```
Check the output on the `tacacs-server`. You should see messages for both the `authentication` and `authorization`
```
# Examples
Oct 07 21:30:36 tacacs-server tac_plus[5704]: login query for 'tacadmin' port tty2 from 192.168.0.1 accepted
Oct 07 21:30:36 tacacs-server tac_plus[5705]: connect from 192.168.0.1 [192.168.0.1]
Oct 07 21:30:36 tacacs-server tac_plus[5705]: Start authorization request
Oct 07 21:30:36 tacacs-server tac_plus[5705]: do_author: user='tacadmin'
Oct 07 21:30:36 tacacs-server tac_plus[5705]: user 'tacadmin' found
Oct 07 21:30:36 tacacs-server tac_plus[5705]: exec authorization request for tacadmin
Oct 07 21:30:36 tacacs-server tac_plus[5705]: exec is explicitly permitted by line 4
Oct 07 21:30:36 tacacs-server tac_plus[5705]: nas:service=shell (passed thru)
Oct 07 21:30:36 tacacs-server tac_plus[5705]: nas:cmd* (passed thru)
Oct 07 21:30:36 tacacs-server tac_plus[5705]: nas:absent, server:priv-lvl=15 -> add priv-lvl=15 (k)
Oct 07 21:30:36 tacacs-server tac_plus[5705]: added 1 args
Oct 07 21:30:36 tacacs-server tac_plus[5705]: out_args[0] = service=shell input copy discarded
Oct 07 21:30:36 tacacs-server tac_plus[5705]: out_args[1] = cmd* input copy discarded
Oct 07 21:30:36 tacacs-server tac_plus[5705]: out_args[2] = priv-lvl=15 compacted to out_args[0]
Oct 07 21:30:36 tacacs-server tac_plus[5705]: 1 output args
Oct 07 21:30:36 tacacs-server tac_plus[5705]: authorization query for 'tacadmin' tty2 from 192.168.0.1 accepted
```
Stop the journalctl monitor (`Cntrl-c`), and open the accounting log.
```
tail -f /var/log/tac_plus.acct
```
> Note: If the command fails and the file isn't found, return to the SSH session to the router and run a couple commands. The file isn't created until an accounting message is sent to the server.
Run some more commands on `rtr1`. Try some that are `priv 15` as well as `priv 1`
```
! Priv 1
show ip route
! Priv 15
write mem
```
Verify the accounting logs were received.
Logout from the router, and log in as `tacoper`. Verify through the same logs that the user is given the correct access.
## Other useful commands
### Debugs on the router
```
debug aaa authentication
debug aaa authorization
debug aaa accounting
debug tacacs authentication
debug tacacs authorization
debug tacacs accounting
```
### Show commands on router
```
show tacacs
show aaa sessions
```
### Test AAA
```
test aaa group tacacs+ tacadmin admin123 legacy
```
### tacacs-server logs
```
journalctl -fu tac_plus
tail -f /var/log/tac_plus.acct
tail -f /var/log/tac_plus.log
```
### tac_plus server maintenance
```
systemctl status tac_plus
sudo systemctl stop tac_plus
sudo systemctl start tac_plus
```

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lab-topologies/aaa-tacacs-exploration/Snack_Minute_AAA_TACACS_Exploration.yaml Normal file
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annotations:
- border_color: '#00000000'
border_style: ''
color: '#808080FF'
rotation: 0
text_bold: false
text_content: 192.168.0.10
text_font: monospace
text_italic: false
text_size: 10
text_unit: pt
thickness: 1
type: text
x1: -565.0
y1: -74.0
z_index: 0
- border_color: '#00000000'
border_style: ''
color: '#808080FF'
rotation: 0
text_bold: false
text_content: 192.168.0.11
text_font: monospace
text_italic: false
text_size: 10
text_unit: pt
thickness: 1
type: text
x1: -325.0
y1: -73.0
z_index: 0
- border_color: '#00000000'
border_style: ''
color: '#808080FF'
rotation: 0
text_bold: false
text_content: 192.168.0.1
text_font: monospace
text_italic: false
text_size: 10
text_unit: pt
thickness: 1
type: text
x1: -446.3066108896985
y1: 47.653305444849266
z_index: 0
- border_color: '#00000000'
border_style: ''
color: '#808080FF'
rotation: 0
text_bold: false
text_content: cisco / cisco
text_font: monospace
text_italic: false
text_size: 8
text_unit: pt
thickness: 1
type: text
x1: -559.75
y1: -55.5
z_index: 1
- border_color: '#00000000'
border_style: ''
color: '#808080FF'
rotation: 0
text_bold: false
text_content: cisco / cisco
text_font: monospace
text_italic: false
text_size: 8
text_unit: pt
thickness: 1
type: text
x1: -318.75
y1: -53.5
z_index: 1
- border_color: '#00000000'
border_style: ''
color: '#808080FF'
rotation: 0
text_bold: false
text_content: |-
TACACS Accounts
tacadmin / admin123 (priv 15)
tacoper / oper123 (priv 1)
TACACS Secret
tacacs123
TACACS Log Files
journalctl -fu tac_plus
tail -f /var/log/tac_plus.acct
text_font: monospace
text_italic: false
text_size: 10
text_unit: pt
thickness: 1
type: text
x1: -960.4378534132434
y1: -244.7193548844158
z_index: 2
- border_color: '#00000000'
border_style: ''
color: '#808080FF'
rotation: 0
text_bold: false
text_content: cisco / cisco
text_font: monospace
text_italic: false
text_size: 8
text_unit: pt
thickness: 1
type: text
x1: -443.7290720829766
y1: 67.39536041488296
z_index: 1
- border_color: '#00000000'
border_style: ''
color: '#0C0C0C'
rotation: 0
text_bold: true
text_content: Exploring AAA / TACACS Configuration for IOS
text_font: monospace
text_italic: false
text_size: 13
text_unit: pt
thickness: 1
type: text
x1: -962.0997946295324
y1: -292.6838112360871
z_index: 3
nodes:
- boot_disk_size: null
configuration: []
cpu_limit: null
cpus: null
data_volume: null
hide_links: false
id: n0
image_definition: null
label: internet
node_definition: external_connector
parameters: {}
ram: null
tags: []
x: -640
y: -240
interfaces:
- id: i0
label: port
slot: 0
type: physical
- boot_disk_size: null
configuration: []
cpu_limit: null
cpus: null
data_volume: null
hide_links: false
id: n1
image_definition: null
label: internet-sw
node_definition: unmanaged_switch
parameters: {}
ram: null
tags: []
x: -640
y: -120
interfaces:
- id: i0
label: port0
slot: 0
type: physical
- id: i1
label: port1
slot: 1
type: physical
- id: i2
label: port2
slot: 2
type: physical
- id: i3
label: port3
slot: 3
type: physical
- id: i4
label: port4
slot: 4
type: physical
- id: i5
label: port5
slot: 5
type: physical
- id: i6
label: port6
slot: 6
type: physical
- id: i7
label: port7
slot: 7
type: physical
- boot_disk_size: null
configuration:
- name: user-data
content: |-
#cloud-config
hostname: tacacs-server
manage_etc_hosts: True
system_info:
default_user:
name: cisco
password: cisco
chpasswd: { expire: False }
ssh_pwauth: True
ssh_authorized_keys:
- your-ssh-pubkey-line-goes-here
# Install requirements for tac_plus
package_update: true
packages:
- wget
- make
- gcc
- flex
- bison
- libwrap0-dev
write_files:
# Create the tac_plus configuration file
- path: /etc/tacacs/tac_plus.conf
content: |
key = tacacs123
group = netadmin {
default service = permit
service = exec {
priv-lvl = 15
}
}
group = netoper {
default service = permit
service = exec {
priv-lvl = 1
}
}
user = tacadmin {
login = cleartext admin123
member = netadmin
}
user = tacoper {
login = cleartext oper123
member = netoper
}
# Create a systemd service to manage tac_plus
- path: /etc/systemd/system/tac_plus.service
content: |
[Unit]
Description=tac_plus Service
After=network.target
[Service]
Type=simple
ExecStart=/tacacs/sbin/tac_plus -G -C /etc/tacacs/tac_plus.conf -d 8 -d 16 -l /var/log/tac_plus.log
[Install]
WantedBy=multi-user.target
runcmd:
# Download tac_plus source code and un-tar it
- wget https://shrubbery.net/pub/tac_plus/tacacs-F4.0.4.28.tar.gz -O /opt/tacacs-F4.0.4.28.tar.gz
- cd /opt && tar -xzf tacacs-F4.0.4.28.tar.gz
# Compile and install tac_plus
- cd /opt/tacacs-F4.0.4.28 && ./configure --prefix=/tacacs && make && make install
# Enable and start the systemd service
- systemctl enable tac_plus
- systemctl start tac_plus
# Configure "inside" network adapter
# Note: ens2 is connected to internet through NAT ext-con and
# required to download the software
- ip address add 192.168.0.10/24 dev ens3
- ip link set up dev ens3
cpu_limit: null
cpus: null
data_volume: null
hide_links: false
id: n2
image_definition: ubuntu-22-04-20240126
label: tacacs-server
node_definition: ubuntu
parameters: {}
ram: null
tags: []
x: -520
y: -120
interfaces:
- id: i0
label: ens2
slot: 0
type: physical
- id: i1
label: ens3
slot: 1
type: physical
- boot_disk_size: null
configuration: []
cpu_limit: null
cpus: null
data_volume: null
hide_links: false
id: n3
image_definition: null
label: lab-sw
node_definition: unmanaged_switch
parameters: {}
ram: null
tags: []
x: -400
y: -120
interfaces:
- id: i0
label: port0
slot: 0
type: physical
- id: i1
label: port1
slot: 1
type: physical
- id: i2
label: port2
slot: 2
type: physical
- id: i3
label: port3
slot: 3
type: physical
- id: i4
label: port4
slot: 4
type: physical
- id: i5
label: port5
slot: 5
type: physical
- id: i6
label: port6
slot: 6
type: physical
- id: i7
label: port7
slot: 7
type: physical
- boot_disk_size: null
configuration:
- name: ios_config.txt
content: |-
hostname rtr1
!
! In order to avoid entering a configuration dialog
! on boot, please ensure that all ethernet interfaces
! have some ip configuration present here such as the
! example below:
!
interface range Ethernet 0/0 - 3
no ip address
shutdown
!
no ip domain lookup
ip domain name lab.intra
crypto key generate rsa general-keys modulus 2048
!
aaa new-model
!
username cisco priv 15 secret cisco
!
interface Eth0/0
no shutdown
ip address 192.168.0.1 255.255.255.0
exit
!
end
cpu_limit: null
cpus: null
data_volume: null
hide_links: false
id: n4
image_definition: null
label: rtr1
node_definition: iol-xe
parameters: {}
ram: null
tags: []
x: -400
y: 0
interfaces:
- id: i0
label: Loopback0
type: loopback
- id: i1
label: Ethernet0/0
slot: 0
type: physical
- id: i2
label: Ethernet0/1
slot: 1
type: physical
- id: i3
label: Ethernet0/2
slot: 2
type: physical
- id: i4
label: Ethernet0/3
slot: 3
type: physical
- boot_disk_size: null
configuration:
- name: node.cfg
content: |
# this is a shell script which will be sourced at boot
hostname desktop
# configurable user account
USERNAME=cisco
PASSWORD=cisco
# Network Settings
ip address add 192.168.0.11/24 dev eth0
cpu_limit: null
cpus: null
data_volume: null
hide_links: false
id: n5
image_definition: null
label: desktop
node_definition: desktop
parameters: {}
ram: null
tags: []
x: -280
y: -120
interfaces:
- id: i0
label: eth0
slot: 0
type: physical
- id: i1
label: eth1
slot: 1
type: physical
links:
- id: l0
n1: n1
n2: n0
i1: i0
i2: i0
conditioning: {}
label: ext-sw-port0<->ext-conn-0-port
- id: l1
n1: n2
n2: n1
i1: i0
i2: i3
conditioning: {}
label: aaa-server_0-ens2<->ext-sw-port3
- id: l2
n1: n2
n2: n3
i1: i1
i2: i0
conditioning: {}
label: aaa-server_0-ens3<->ext-sw_0-port0
- id: l3
n1: n4
n2: n3
i1: i1
i2: i1
conditioning: {}
label: router1_0-Ethernet0/0<->ext-sw_0-port1
- id: l4
n1: n5
n2: n3
i1: i0
i2: i2
conditioning: {}
label: desktop-0-eth0<->ext-sw_0-port2
lab:
description: Simple topology for practicing AAA TACACS configuration in IOS.
notes: |-
# Exploring AAA / TACACS Configuration for IOS
## Starting Configuration
`rtr1` has the following configuration applied as startup configuration to enable inbound SSH from `desktop` that is locally authenticated.
```
ip domain name lab.intra
crypto key generate rsa general-keys modulus 2048
!
aaa new-model
!
username cisco priv 15 secret cisco
```
## Ensuring the serial / console leverages local authentication
To provide safety and fallback access to devices, we will force the console line to only use local admin accounts.
```
aaa authentication login CONSOLE local
aaa authorization console
aaa authorization exec CONSOLE local
!
line con 0
login authentication CONSOLE
authorization exec CONSOLE
!
```
## Configuring TACACS server as default AAA
Start by identitying the interface that TACACS packets should be sourced from. This is often important because TACACS servers typically only respond to known hosts/addresses.
```
ip tacacs source-interface Ethernet0/0
```
Now create the TACACS server entry for the server. Be sure to double check the "key" (secret) used for communications.
> Note: Be careful to NOT add an extra "space" after the key. This can cause problems on some platforms.
```
tacacs server aaa-server
address ipv4 192.168.0.10
key tacacs123
!
```
Create a `aaa group` that includes the TACACS server. In a production environment, you would typically have at least 2 TACASC servers configured for fallback.
```
aaa group server tacacs+ AAA-TACACS
server name aaa-server
!
```
Test that the TACACS server is responding successfully.
```
test aaa group tacacs+ tacadmin admin123 legacy
```
Configure the authentication, authorization, and accounting policies.
```
aaa authentication login default group AAA-TACACS local
aaa authorization exec default group AAA-TACACS local
!
aaa accounting exec default start-stop group ISE-TACACS
aaa accounting commands 1 default start-stop group AAA-TACACS
aaa accounting commands 15 default start-stop group AAA-TACACS
!
```
## Testing the configuration
Open the console for the `tacacs-server` and monitor the service "journal"
```
journalctl -fu tac_plus
```
Open the console for the `desktop` and attempt to connect to `rtr1` with SSH as the `tacadmin` user.
```
ssh tacadmin@192.168.0.1
```
After you log in, run a command to verify access.
```
show ip interface brief
```
Check the output on the `tacacs-server`. You should see messages for both the `authentication` and `authorization`
```
# Examples
Oct 07 21:30:36 tacacs-server tac_plus[5704]: login query for 'tacadmin' port tty2 from 192.168.0.1 accepted
Oct 07 21:30:36 tacacs-server tac_plus[5705]: connect from 192.168.0.1 [192.168.0.1]
Oct 07 21:30:36 tacacs-server tac_plus[5705]: Start authorization request
Oct 07 21:30:36 tacacs-server tac_plus[5705]: do_author: user='tacadmin'
Oct 07 21:30:36 tacacs-server tac_plus[5705]: user 'tacadmin' found
Oct 07 21:30:36 tacacs-server tac_plus[5705]: exec authorization request for tacadmin
Oct 07 21:30:36 tacacs-server tac_plus[5705]: exec is explicitly permitted by line 4
Oct 07 21:30:36 tacacs-server tac_plus[5705]: nas:service=shell (passed thru)
Oct 07 21:30:36 tacacs-server tac_plus[5705]: nas:cmd* (passed thru)
Oct 07 21:30:36 tacacs-server tac_plus[5705]: nas:absent, server:priv-lvl=15 -> add priv-lvl=15 (k)
Oct 07 21:30:36 tacacs-server tac_plus[5705]: added 1 args
Oct 07 21:30:36 tacacs-server tac_plus[5705]: out_args[0] = service=shell input copy discarded
Oct 07 21:30:36 tacacs-server tac_plus[5705]: out_args[1] = cmd* input copy discarded
Oct 07 21:30:36 tacacs-server tac_plus[5705]: out_args[2] = priv-lvl=15 compacted to out_args[0]
Oct 07 21:30:36 tacacs-server tac_plus[5705]: 1 output args
Oct 07 21:30:36 tacacs-server tac_plus[5705]: authorization query for 'tacadmin' tty2 from 192.168.0.1 accepted
```
Stop the journalctl monitor (`Cntrl-c`), and open the accounting log.
```
tail -f /var/log/tac_plus.acct
```
> Note: If the command fails and the file isn't found, return to the SSH session to the router and run a couple commands. The file isn't created until an accounting message is sent to the server.
Run some more commands on `rtr1`. Try some that are `priv 15` as well as `priv 1`
```
! Priv 1
show ip route
! Priv 15
write mem
```
Verify the accounting logs were received.
Logout from the router, and log in as `tacoper`. Verify through the same logs that the user is given the correct access.
## Other useful commands
### Debugs on the router
```
debug aaa authentication
debug aaa authorization
debug aaa accounting
debug tacacs authentication
debug tacacs authorization
debug tacacs accounting
```
### Show commands on router
```
show tacacs
show aaa sessions
```
### Test AAA
```
test aaa group tacacs+ tacadmin admin123 legacy
```
### tacacs-server logs
```
journalctl -fu tac_plus
tail -f /var/log/tac_plus.acct
tail -f /var/log/tac_plus.log
```
### tac_plus server maintenance
```
systemctl status tac_plus
sudo systemctl stop tac_plus
sudo systemctl start tac_plus
```
title: Snack Minute AAA TACACS Exploration
version: 0.2.2

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