problems switching between roles (newrole)

[Christopher J. PeBenito]

On Mon, 2007-05-07 at 15:03 -0400, Philip Tricca wrote:
> Hello List,
> 
> Question about managing roles:  I'm trying to setup my user to have 
> access to both the unprivileged user_r role and the administrative role 
> sysadm_r.  My system is FC6 using the latest policy from yum:
[...]
> I've created new SELinux user:
> semanage user -a -R sysadm_r -R user_r -P user MyUser_u
> 
> I've associated a Linux user with my SELinux user:
> semanage login -a -s MyUser_u MyUser
> 
> When I login with my new user I see ...
> 
> <shell>
> 	[MyUser at test ~]$ id -Z
> 	MyUser_u:user_r:user_t
> 	[MyUser at test ~]$ newrole -r sysadm_r -t sysadm_t
> 	Authenticating MyUser.
> 	Password:
> 	failed to exec shell
> 	: Permission denied
> 	[MyUser at test ~]$
> </shell>
> 
> The initial role is user_r which I like.  But when MyUser attempts to 
> change to the new role (sysadm_r through use of newrole)... they cannot.
> 
> <avc>
> type=AVC msg=audit(1178544785.335:2418): avc:  denied  { transition } 
> for  pid=13798 comm="newrole" name="bash" dev=hda3 ino=162298 
> scontex=MyUser_u:user_r:newrole_t:s0 
> tcontext=MyUser_u:sysadm_r:sysadm_t:s0 tclass=process
> </avc>
[...]
> A similar problem seems to arise when associating Linux users with 
> user_r, staff_r and sysadm_r.  The user will login with the default 
> staff_r, will be able to newrole up to the sysadm_r role, but cannot 
> change their role to user_r through similar means (newrole -r user_r -t 
> user_t).

Allowed role changes are defined in the policy, and the stock policy
does not allow a change of staff_r <-> user_r or user_r -> sysadm_r.

> I'd assume it's a fairly standard practice to make an SELinux user with 
> the user_r and sysadm_r roles

No, user_r is for generic unprivileged users.  If you want an
unprivileged user that can change to the sysadm_r, you should be using
staff_r instead of user_r.  User_r and staff_r basically have the same
rules except staff_r can change to sysadm_r, where user_r can't.

-- 
Chris PeBenito
Tresys Technology, LLC
(410) 290-1411 x150