RADIUS AAA
Cumulus Linux provides add-on packages to enable RADIUS users to log into the switch transparently with minimal configuration. There is no need to create accounts or directories on the switch. Authentication uses PAM and includes login, ssh
, sudo
and su
.
Install the RADIUS Packages
NVUE automatically installs the RADIUS AAA packages; you do not have to install the packages if you use NVUE commands to configure RADIUS AAA.
If you use Linux commands to configure RADIUS AAA, you must install the RADIUS libnss-mapuser
and libpam-radius-auth
packages before you start configuration. The packages are in the cumulus-local-apt-archive
repository, which is embedded in the Cumulus Linux image. You can install the packages even when the switch is not connected to the internet.
To install the RADIUS packages:
cumulus@switch:~$ sudo apt-get update
cumulus@switch:~$ sudo apt-get install libnss-mapuser libpam-radius-auth
After installation completes, either reboot the switch or run the sudo systemctl restart nvued
command.
The nvshow
group includes the radius_user
account, and the nvset
and nvapply
groups. The sudo
groups include the radius_priv_user
account. This enables all RADIUS logins to run NVUE nv show
commands and all privileged RADIUS users to also run nv set
, nv unset
, and nv apply
commands, and to use sudo
.
Required RADIUS Client Configuration
After you install the required RADIUS packages, configure the following required settings on the switch (the RADIUS client):
- Set the IP address or hostname of at least one RADIUS server. You can specify a port for the server (optional). The default port number is 1812.
- Set the secret key shared between the RADIUS server and client. If you include special characters in the key (such as $), you must enclose the key in single quotes (').
- If you use NVUE commands to configure RADIUS, you must also:
- Set the priority at which Cumulus Linux contacts a RADIUS server for load balancing. You can set a value between 1 and 100. The lower value is the higher priority.
- Set the priority for the authentication order for local and RADIUS users. You can set a value between 1 and 100. The lower value is the higher priority.
- Enable RADIUS.
After you configure any RADIUS settings with NVUE and you run nv config apply
, you must restart the NVUE service with the sudo systemctl restart nvued.service
command.
The following example commands set:
- The IP address of the RADIUS server to 192.168.0.254 and the port to 42.
- The secret to
'myradius$key'
. - The priority at which Cumulus Linux contacts the RADIUS server to 10.
- The authentication order to 10 so that RADIUS authentication has priority over local.
- The RADIUS option to
enable
.
cumulus@switch:~$ nv set system aaa radius server 192.168.0.254 port 42
cumulus@switch:~$ nv set system aaa radius server 192.168.0.254 secret 'myradius$key'
cumulus@switch:~$ nv set system aaa radius server 192.168.0.254 priority 10
cumulus@switch:~$ nv set system aaa authentication-order 10 radius
cumulus@switch:~$ nv set system aaa authentication-order 20 local
cumulus@switch:~$ nv set system aaa radius enable on
cumulus@switch:~$ nv config apply
Edit the /etc/pam_radius_auth.conf
file to specify the hostname or IP address of at least one RADIUS server, and the shared secret you want to use to authenticate and encrypt communication with each server.
...
mapped_priv_user radius_priv_user
# server[:port] shared_secret timeout (secs) src_ip
192.168.0.254:42 myradius$key 3
...
You must be able to resolve the hostname of the switch to an IP address. If you cannot find the hostname in DNS, you can add the hostname to the /etc/hosts
file manually. Be aware that adding the hostname to the /etc/hosts
file manually can cause problems because DHCP assigns the IP address, which can change at any time.
Cumulus Linux verifies multiple server configuration lines in the order listed. Other than memory, there is no limit to the number of RADIUS servers you can use.
The server port number is optional. The system looks up the port in the /etc/services
file. However, you can override the ports in the /etc/pam_radius_auth.conf
file.
Optional RADIUS Configuration
You can configure the following global RADIUS settings and server specific settings.
Setting | Description |
---|---|
vrf | The VRF you want to use to communicate with the RADIUS servers. This is typically the management VRF (mgmt ), which is the default VRF on the switch. You cannot specify more than one VRF. |
privilege-level | The minimum privilege level that determines if users can configure the switch with NVUE commands and sudo, or have read-only rights. The default privilege level is 15, which provides full administrator access. This is a global option only; you cannot set the minimum privilege level for specific RADIUS servers. |
retransmit | The maximum number of retransmission attempts allowed for requests when a RADIUS authentication request times out. This is a global option only; you cannot set the number of retransmission attempts for specific RADIUS servers. |
timeout | The timeout value when a server is slow or latencies are high. You can set a value between 1 and 60. The default timeout is 3 seconds. If you configure multiple RADIUS servers, you can set a global timeout for all servers. |
source-ipv4 source-ipv6 | A specific interface to reach all RADIUS servers. To configure the source IP address for a specific RADIUS server, use the source-ip option. |
debug | The debug option for troubleshooting. The debugging messages write to /var/log/syslog . When the RADIUS client is working correctly, you can disable the debug option. You enable the debug option globally for all the servers. |
The following example configures global RADIUS settings:
cumulus@switch:~$ nv set system aaa radius vrf mgmt
cumulus@switch:~$ nv set system aaa radius privilege-level 10
cumulus@switch:~$ nv set system aaa radius retransmit 8
cumulus@switch:~$ nv set system aaa radius timeout 10
cumulus@switch:~$ nv set system aaa radius source-ipv4 192.168.1.10
cumulus@switch:~$ nv set system aaa radius debug enable
cumulus@switch:~$ nv config apply
The following example configures RADIUS settings for a specific RADIUS server:
cumulus@switch:~$ nv set system aaa radius server 192.168.0.254 source-ip 192.168.1.10
cumulus@switch:~$ nv set system aaa radius server 192.168.0.254 timeout 10
cumulus@switch:~$ nv config apply
Setting | Description |
---|---|
vrf | The VRF you want to use to communicate with the RADIUS servers. This is typically the management VRF (mgmt ), which is the default VRF on the switch. You cannot specify more than one VRF. |
privilege-level | Determines the privilege level for the user on the switch. |
timeout | The timeout value when a server is slow or latencies are high. You can set a value between 1 and 60. The default timeout is 3 seconds. If you configure multiple RADIUS servers, you can set a global timeout for all servers. |
src_ip | A specific IPv4 or IPv6 interface to reach the RADIUS server. If you configure multiple RADIUS servers, you can configure a specific interface to reach all RADIUS servers. |
debug | The debug option for troubleshooting. The debugging messages write to /var/log/syslog . When the RADIUS client is working correctly, you can disable the debug option. If you configure multiple RADIUS servers, you can enable the debug option globally for all the servers. |
Edit the /etc/pam_radius_auth.conf
file.
...
# Set the minimum privilege level in VSA attribute shell:privilege-level=VALUE
# default is 15, range is 0-15.
privilege-level 10
#
# Uncomment to enable debugging, can be used instead of altering pam files
debug
#
# Account for privileged radius user mapping. If you change it here, you need
# to change /etc/nss_mapuser.conf as well
mapped_priv_user radius_priv_user
# server[:port] shared_secret timeout (secs) src_ip
192.168.0.254:42 myradius$key 10 192.168.1.10
vrf-name mgmt
Enable Login without Local Accounts
NVUE does not provide commands to enable login without local accounts.
LDAP is not commonly used with switches and adding accounts locally is cumbersome, Cumulus Linux includes a mapping capability with the libnss-mapuser
package.
Mapping uses two NSS (Name Service Switch) plugins, one for account name, and one for UID lookup. The installation process configures these accounts automatically in the /etc/nsswitch.conf
file and removes them when you delete the package. See the nss_mapuser (8)
man page for the full description of this plugin.
A username is mapped at login to a fixed account specified in the configuration file, with the fields of the fixed account used as a template for the user that is logging in.
For example, if you look up the name dave
and the fixed account in the configuration file is radius\_user
, and that entry in /etc/passwd
is:
radius_user:x:1017:1002:radius user:/home/radius_user:/bin/bash
then the matching line that returns when you run getent passwd dave
is:
cumulus@switch:~$ getent passwd dave
dave:x:1017:1002:dave mapped user:/home/dave:/bin/bash
The login process creates the home directory /home/dave
if it does not already exist and populates it with the standard skeleton files by the mkhomedir_helper
command.
The configuration file /etc/nss_mapuser.conf
configures the plugins. The file includes the mapped account name, which is radius_user
by default. You can change the mapped account name by editing the file. The nss_mapuser (5)
man page describes the configuration file.
A flat file mapping derives from the session number assigned during login, which persists across su
and sudo
. Cumulus Linux removes the mapping at logout.
Local Fallback Authentication
NVUE does not provide commands to configure local fallback authentication.
If a site wants to allow local fallback authentication for a user when none of the RADIUS servers are reachable, you can add a privileged user account as a local account on the switch. The local account must have the same unique identifier as the privileged user and the shell must be the same.
To configure local fallback authentication:
Add a local privileged user account. For example, if the
radius_priv_user
account in the/etc/passwd
file isradius_priv_user:x:1002:1001::/home/radius_priv_user:/sbin/radius_shell
, run the following command to add a local privileged user account namedjohnadmin
:cumulus@switch:~$ sudo useradd -u 1002 -g 1001 -o -s /sbin/radius_shell johnadmin
To enable the local privileged user to run
sudo
and NVUE commands, run the following commands:cumulus@switch:~$ sudo adduser johnadmin nvset cumulus@switch:~$ sudo adduser johnadmin nvapply cumulus@switch:~$ sudo adduser johnadmin sudo cumulus@switch:~$ sudo systemctl restart nvued
Edit the
/etc/passwd
file to move the local user line before to theradius_priv_user
line:cumulus@switch:~$ sudo vi /etc/passwd ... johnadmin:x:1002:1001::/home/johnadmin:/sbin/radius_shell radius_priv_user:x:1002:1001::/home/radius_priv_user:/sbin/radius_shell
To set the local password for the local user, run the following command:
cumulus@switch:~$ sudo passwd johnadmin
Verify RADIUS Client Configuration
To verify the RADIUS client configuration, log in as a non-privileged user and run the nv set interface
command.
In this example, the ops
user is not a privileged RADIUS user so the ops
user cannot add an interface.
ops@leaf01:~$ nv set interface swp1
ERROR: User ops does not have permission to make networking changes.
In this example, the admin
user is a privileged RADIUS user (with privilege level 15) so is able to add interface swp1.
admin@leaf01:~$ nv set interface swp1
admin@leaf01:~$ nv apply
Show RADIUS Configuration
To show global RADIUS configuration, run the nv show system aaa radius
command:
cumulus@switch:~$ nv show system aaa radius
operational applied
--------------- ------------- -------------
enable on on
vrf mgmt mgmt
debug disabled disabled
privilege-level 15
retransmit 0 0
port 1812
timeout 3
[server] 192.168.0.254 192.168.0.254
To show all RADIUS configured servers, run the nv show system aaa radius server
command:
cumulus@switch:~$ nv show system aaa radius server
Hostname Port Priority Password source-ip Timeout
------------- ---- -------- -------- ------------ -------
192.168.0.254 42 1 * 192.168.1.10 10
To show configuration for a specific RADIUS server, run the nv show system aaa radius server <server>
command:
cumulus@switch:~$ nv show system aaa radius server 192.168.0.254
operational applied
--------- ------------ ------------
port 42 42
timeout 10 10
secret * *
priority 1 10
Remove RADIUS Client Packages
Remove the RADIUS packages with the following command:
cumulus@switch:~$ sudo apt-get remove libnss-mapuser libpam-radius-auth
When you remove the packages, Cumulus Linux deletes the plugins from the /etc/nsswitch.conf
file and from the PAM files.
To remove all configuration files for these packages, run:
cumulus@switch:~$ sudo apt-get purge libnss-mapuser libpam-radius-auth
Cumulus Linux does not remove the RADIUS fixed account from the /etc/passwd
or /etc/group
file or the home directories. They remain in case of modifications to the account or files in the home directories.
To remove the home directories of the RADIUS users, obtain the list by running the following command:
cumulus@switch:~$ sudo ls -l /home | grep radius
For all users listed, except the radius_user
, run the following command to remove the home directories:
cumulus@switch:~$ sudo deluser --remove-home USERNAME
USERNAME
is the account name (the home directory relative portion). This command gives the following warning because the user is not listed in the /etc/passwd
file.
userdel: cannot remove entry 'USERNAME' from /etc/passwd
/usr/sbin/deluser: `/usr/sbin/userdel USERNAME' returned error code 1. Exiting.
After you remove all the RADIUS users, run the command to remove the fixed account. If there are changes to the account in the /etc/nss_mapuser.conf
file, use that account name instead of radius_user
.
cumulus@switch:~$ sudo deluser --remove-home radius_user
cumulus@switch:~$ sudo deluser --remove-home radius_priv_user
cumulus@switch:~$ sudo delgroup radius_users
Considerations
If two or more RADIUS users log in simultaneously, a UID lookup only returns the user that logs in first. Any process that either user runs applies to both, and all files that either user creates apply to the first name matched. This process is similar to adding two local users to the password file with the same UID and GID, and is an inherent limitation of using the UID for the fixed user from the password file. The current algorithm returns the first name matching the UID from the mapping file, which is either the first or second user that logs in.
When you install both the TACACS+ and the RADIUS AAA client, Cumulus Linux does not attempt the RADIUS login. As a workaround, do not install both the TACACS+ and the RADIUS AAA client on the same switch.
When the RADIUS server is reachable outside of the management VRF, such as the default VRF, you might see the following error message when you try to run
sudo
:2008-10-31T07:06:36.191359+00:00 SW01 sudo: pam_radius_auth(sudo:auth): Bind for server 10.1.1.25 failed: Cannot assign requested address 2008-10-31T07:06:36.192307+00:00 sw01 sudo: pam_radius_auth(sudo:auth): No valid server found in configuration file /etc/pam_radius_auth.conf
The error occurs because
sudo
tries to authenticate to the RADIUS server through the management VRF. Before you runsudo
, you must set the shell to the correct VRF:cumulus@switch:~$ vrf exec default bash cumulus@switch:~$ sudo