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redhat:base-redhat:selinux-redhat [2018/05/08 11:01] – [SELinux Access Control] michael | redhat:base-redhat:selinux-redhat [2018/05/08 11:14] – [Role-Based Access Control (RBAC)] michael | ||
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Although the default configuration of the targeted policy is to use unconfined logins, the administrator can quite easily switch to the **Role-Based Access Control** model. This model also switches to ' | Although the default configuration of the targeted policy is to use unconfined logins, the administrator can quite easily switch to the **Role-Based Access Control** model. This model also switches to ' | ||
- | FIXME | + | < |
+ | # semanage login -a -s " | ||
+ | </ | ||
+ | |||
+ | The semanage-login command maps a Linux username to an SELinux user named " | ||
+ | |||
+ | < | ||
+ | # sudo -r sysadm_r -i | ||
+ | </ | ||
+ | |||
+ | This can be automated by adding a configuration file under / | ||
+ | |||
+ | <sxh plain; gutter: false;> | ||
+ | %wheel | ||
+ | </ | ||
+ | |||
+ | It is still possible to login as an unconfined user or switch to the unconfined role via **newrole**, | ||
+ | |||
+ | < | ||
+ | # semanage user -a -R " | ||
+ | </ | ||
+ | |||
+ | Then substituting staff_u for my_staff_u in the semanage-login command. Now attempting to switch to the unconfined_r role will result in an **AVC** and **SELINUX_ERR** message. If the admin wishes to remove the ability to login as an unconfined user completely, they should remap the __default__ login to a more suitable SELinux user, again using semanage-login. | ||
+ | |||
+ | < | ||
+ | # semanage login -m -s " | ||
+ | </ | ||
+ | |||
+ | If a user wishes to login as a role other than their default it is up to the login program to provide this functionality. SSH allows logging in with an alternative SELinux role by specifying it as part of the login identifier (e.g., as a staff user logging in as unconfined_r). | ||
+ | |||
+ | < | ||
+ | # ssh < | ||
+ | </ | ||
+ | |||
+ | The strict model that comes with Role-Based Access Control isn't perfect from a perspective of least privilege; running a quick search using policy analysis tools we can see that several confined programs can still read a users private SSH keys. | ||
+ | |||
+ | <WRAP center box 100%> | ||
+ | < | ||
+ | # sesearch -ACS -t ssh_home_t -c file -p read | ||
+ | </ | ||
+ | |||
+ | <sxh plain; gutter: false;> | ||
+ | Found 132 semantic av rules: | ||
+ | allow snapperd_t file_type : file { ioctl read getattr lock open } ; | ||
+ | allow oddjob_mkhomedir_t user_home_type : file { ioctl read write create getattr setattr lock append unlink link rename open } ; | ||
+ | allow mplayer_t non_security_file_type : file { ioctl read getattr lock open } ; | ||
+ | allow sendmail_t user_home_type : file { ioctl read getattr lock open } ; | ||
+ | allow systemd_tmpfiles_t non_auth_file_type : file { ioctl read write create getattr setattr lock relabelfrom relabelto append unlink link rename open } ; | ||
+ | allow login_pgm ssh_home_t : file { ioctl read getattr lock open } ; | ||
+ | allow ssh_keygen_t ssh_home_t : file { ioctl read write create getattr setattr lock append unlink link rename open } ; | ||
+ | allow colord_t user_home_type : file { read getattr } ; | ||
+ | ... snip ... | ||
+ | </ | ||
+ | </ | ||
+ | |||
+ | '' | ||
+ | |||
+ | Beyond the strict model, Role-Based Access Control also provides a mechanism for limiting the scope of what a user can do when they use **sudo** to switch to root. It is often desirable to enforce least privilege on users with specific roles like DBAs or auditors and the targeted policy includes several user roles for purposes like those, with documentation in their respective manual pages as mentioned in Policy Documentation. | ||
+ | |||
+ | <WRAP center box 100%> | ||
+ | < | ||
+ | # seinfo -r | ||
+ | </ | ||
+ | <sxh plain; gutter: false;> | ||
+ | Roles: 14 | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | | ||
+ | </ | ||
+ | </ | ||
+ | |||
+ | To map a user to one of these admin roles, the same semanage-user command is used as before to create a new SELinux user associated with the desired roles, and then semanage-login to associate the Linux login with the SELinux user. If the user should also be able to start system daemons they administrate from their user domain (i.e., to start mysql as dbadm_r for debugging from a shell) the system_r role should be included in their list of associated roles. | ||
+ | |||
+ | < | ||
+ | # semanage user -a -R " | ||
+ | # semanage login -a -s " | ||
+ | </ | ||
==== Multi-Category Security (MCS) ==== | ==== Multi-Category Security (MCS) ==== | ||