Linux – tacacs+ for Linux authentication/authorization using pam_tacplus

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I am using TACACS+ to authenticate Linux users using pam_tacplus.so PAM module and it works without issues.

I have modified the pam_tacplus module to meet some of my custom requirements.

I know by default, TACACS+ does not have any means to support linux groups or access level control over linux bash commands, however, I was wondering is there any way that some information could be passed from TACACS+ server side to let the pam_tacplus.so module which can be used to allow/deny , or modify the user group on the fly [from pam module itself].

Example: If I could pass the priv-lvl number from server to the client and which could be used for some decision making at the PAM module.

PS: I would prefer a method which involved no modification at the server side [code], all modification should be done at Linux side ie pam_tacplus module.

Thanks for any help.

Best Answer

Eventually I got it working.

Issue 1:

The issue I faced was there is very few documentation available to configure TACACS+ server for a non CISCO device.

Issue 2:

The tac_plus version that I am using

tac_plus -v
tac_plus version F4.0.4.28

does not seem to support

service = shell protocol = ssh

option in tac_plus.conf file.

So eventually I used

service = system  {
                default attribute = permit
                priv-lvl = 15
        }

On the client side (pam_tacplus.so),

I sent the AVP service=system at authorization phase(pam_acct_mgmt), which forced the service to return priv-lvl defined at the configuration file, which I used to device privilege level of the user.

NOTE: In some documentations it is mentioned that service=system is not used anymore. So this option may not work with CISCO devices.

HTH

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