Unit 8: Sudo rule management ============================ **Prerequisites**: - `Unit 3: User management and Kerberos authentication <3-user-management.rst>`_ - `Unit 4: Host-based access control (HBAC) <4-hbac.rst>`_ Sudo is a program that allows users to run programs as another user with different privileges (possibly ``root``). Sudo rules provide fine-grained control over who can execute which processes, as which users. FreeIPA allows centralised management of Sudo rules. To simplify management, Sudo rules can refer to User Groups, Host Groups and *Command Groups* as well as individual users, hosts and commands. Older versions of sudo did not require pam access for passwordless rules (e.g. rules with the NOPASSWD keyword). sudo-1.8.23 and newer require pam access for all rules. The goal of this unit is to allow ``alice`` (being a ``sysadmin``) to run any command on any FreeIPA-enrolled machine, and to allow ``bob`` (who is merely a web server administrator) to control ``httpd`` on hosts that are ``webservers``. As of FreeIPA 4.6.90.pre2, you should enable SSSD's sudo responder by running:: [client]$ sudo authselect enable-feature with-sudo Restart SSSD:: [client]$ sudo systemctl restart sssd Permitting ``alice`` to run all commmands ----------------------------------------- Let's deal with ``alice`` first. Before we do anything else, log in as ``alice`` and attempt to run the ``id`` command as ``root``. Observe that the action is denied:: [client]$ su -l alice Password: [alice@client]$ sudo id [sudo] password for alice: alice is not allowed to run sudo on client. This incident will be reported. [alice@client]$ exit logout Now define the ``sysadmin_sudo`` rule, which allows members of the ``sysadmin`` User Group to to run any command on any host:: [client]$ ipa sudorule-add sysadmin_sudo \ --hostcat=all --runasusercat=all --runasgroupcat=all --cmdcat=all ------------------------------- Added Sudo Rule "sysadmin_sudo" ------------------------------- Rule name: sysadmin_sudo Enabled: TRUE Host category: all Command category: all RunAs User category: all RunAs Group category: all Next add the ``sysadmin`` User Group to the Sudo rule:: [client]$ ipa sudorule-add-user sysadmin_sudo --group sysadmin Rule name: sysadmin_sudo Enabled: TRUE Host category: all Command category: all RunAs User category: all RunAs Group category: all User Groups: sysadmin ------------------------- Number of members added 1 ------------------------- Now attempt to ``sudo id`` as ``alice`` again:: [client]$ su -l alice Password: [alice@client]$ sudo id [sudo] password for alice: uid=0(root) gid=0(root) groups=0(root) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 This time the action was allowed, and we can see from the output that ``alice`` indeed executed the ``id`` command as ``root``. **Note:** if the command is prevented there may be some stale cache entries. Move on with the workshop and try again in 5 minutes. Permitting ``bob`` to run web administration commands ----------------------------------------------------- Now let us turn our attention to ``bob``. The goal is to allow ``bob`` and other web servers administrators to run commands related to web server administration (and only such commands). First, create a new User Group named ``webadmin`` and add ``bob`` as a member. Add an ``hbacrule`` that allows ``bob`` to log into hosts that are members of the ``webservers`` Host Group using the ``sshd`` service. Once this is done you should be able to login, but not use ``su -l``:: [client]$ su -l bob Password: [bob@client]$ su -l bob Password: su: Permission denied Then, let's observe that ``bob`` currently cannot restart Apache:: [bob@client]$ sudo systemctl restart httpd [sudo] password for bob: sudo: PAM account management error: Permission denied Take note that the error is different from the one alice got, which was:: alice is not allowed to run sudo on client. This incident will be reported. While the HBAC rule alice uses (sysadmin_webservers) was created with "--servicecat=all", the HBAC rule for bob was created with sshd in mind, like this:: [server]$ ipa hbacrule-add-service webadmin_webservers --hbacsvcs=sshd As bob needs to run both ``su -l`` and ``sudo``, add both commands to the list of allowed services in your access control rule, for instance:: [server]$ ipa hbacrule-add-service webadmin_webservers \ --hbacsvcs=sudo --hbacsvcs=su-l Now login and logout as bob. Not only bob should now be able to use ``su -l``, but the error message from ``sudo`` should change:: [bob@client]$ sudo systemctl restart httpd [sudo] password for bob: Sorry, user bob is not allowed to execute '/bin/systemctl restart httpd' as root on client.ipademo.local. Now define the ``webadmin_sudo`` rule. Note that we *do not* use ``--hostcat=all`` or ``cmdcat=all`` this time. :: [client]$ ipa sudorule-add webadmin_sudo \ --runasusercat=all --runasgroupcat=all ------------------------------- Added Sudo Rule "webadmin_sudo" ------------------------------- Rule name: webadmin_sudo Enabled: TRUE RunAs User category: all RunAs Group category: all Add the ``webadmin`` User Group and ``webservers`` Host Group to the rule:: [client]$ ipa sudorule-add-user webadmin_sudo --group webadmin Rule name: webadmin_sudo Enabled: TRUE RunAs User category: all RunAs Group category: all User Groups: webadmin ------------------------- Number of members added 1 ------------------------- [client]$ ipa sudorule-add-host webadmin_sudo --hostgroup webservers Rule name: webadmin_sudo Enabled: TRUE RunAs User category: all RunAs Group category: all User Groups: webadmin Host Groups: webservers ------------------------- Number of members added 1 ------------------------- Next, define *Sudo Commands* and a *Sudo Command Group* for web server administration:: [client]$ ipa sudocmd-add "/usr/bin/systemctl start httpd" --------------------------------------------------- Added Sudo Command "/usr/bin/systemctl start httpd" --------------------------------------------------- Sudo Command: /usr/bin/systemctl start httpd [client]$ ipa sudocmd-add "/usr/bin/systemctl restart httpd" ----------------------------------------------------- Added Sudo Command "/usr/bin/systemctl restart httpd" ----------------------------------------------------- Sudo Command: /usr/bin/systemctl restart httpd [client]$ ipa sudocmdgroup-add webadmin_cmds ---------------------------------------- Added Sudo Command Group "webadmin_cmds" ---------------------------------------- Sudo Command Group: webadmin_cmds [client]$ ipa sudocmdgroup-add-member webadmin_cmds \ --sudocmds "/usr/bin/systemctl start httpd" \ --sudocmds "/usr/bin/systemctl restart httpd" Sudo Command Group: webadmin_cmds Member Sudo commands: /usr/bin/systemctl start httpd, /usr/bin/systemctl restart httpd ------------------------- Number of members added 2 ------------------------- Finally, add this new command group to the Sudo rule:: [client]$ ipa sudorule-add-allow-command webadmin_sudo \ --sudocmdgroups webadmin_cmds Rule name: webadmin_sudo Enabled: TRUE RunAs User category: all RunAs Group category: all User Groups: webadmin Host Groups: webservers Sudo Allow Command Groups: webadmin_cmds ------------------------- Number of members added 1 ------------------------- Now log in again as ``bob`` and observe that we have reached our goal: he can restart (or start) Apache, but not run other commands via ``sudo``:: [client]$ su -l bob Password: [bob@client]$ sudo systemctl restart httpd [sudo] password for bob: [bob@client]$ sudo id Sorry, user bob is not allowed to execute '/bin/id' as root on client.ipademo.local. This concludes the unit. Now that you have Sudo rules working, proceed to `Unit 9: SELinux User Maps <9-selinux-user-map.rst>`_.