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Bug 1922450 - staff_u users can utilize newrole, resulting in ability to access su directly
Summary: staff_u users can utilize newrole, resulting in ability to access su directly
Keywords:
Status: CLOSED NOTABUG
Alias: None
Product: Red Hat Enterprise Linux 8
Classification: Red Hat
Component: selinux-policy
Version: 8.3
Hardware: All
OS: Linux
high
medium
Target Milestone: rc
: 8.0
Assignee: Zdenek Pytela
QA Contact: BaseOS QE Security Team
URL:
Whiteboard:
Depends On:
Blocks: 1778780
TreeView+ depends on / blocked
 
Reported: 2021-01-29 18:35 UTC by Ryan Mullett
Modified: 2022-01-05 13:43 UTC (History)
8 users (show)

Fixed In Version:
Doc Type: No Doc Update
Doc Text:
Clone Of:
Environment:
Last Closed: 2021-03-25 16:42:57 UTC
Type: Bug
Target Upstream Version:
Embargoed:
pm-rhel: mirror+

Attachments (Terms of Use)

Description Ryan Mullett 2021-01-29 18:35:04 UTC 
Description of problem:
According to documentation here:

Using SELinux Red Hat Enterprise Linux 8 | Red Hat Customer Portal
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html-single/using_selinux/index#managing-confined-and-unconfined-users_using-selinux

Users with the staff_u role should only be able to access sudo, but should not have access to su. Because staff_u can utilize the newrole command to change to sysadm_r, they can still access su

Version-Release number of selected component (if applicable):
policycoreutils-newrole-2.9-9.el8.x86_64
selinux-policy-3.14.3-54.el8.noarch

How reproducible:
Always

Steps to Reproduce:

1. useradd -Z staff_u someuser -G wheel
2. ssh someuser.com
3. newrole -r sysadm_r
4. id -Z
5. su - will be successful (according to docs this should fail)

Actual results:
su - is successful

Expected results:
According to documentation staff_u should not be able to utilize su, and should be limited to sudo.

Additional info:
In the default configuration, staff_u is listed as having access to staff_r, sysadm_r, and unconfined_r. I expect that this may be expected behavior, and that the issue lies on the documentation side, if so I believe some clarification is needed regarding what the actual limitations of staff_u are.

[root@localhost ~]# semanage user -l

                Labeling   MLS/       MLS/                          
SELinux User    Prefix     MCS Level  MCS Range                      SELinux Roles

guest_u         user       s0         s0                             guest_r
root            user       s0         s0-s0:c0.c1023                 staff_r sysadm_r system_r unconfined_r
staff_u         user       s0         s0-s0:c0.c1023                 staff_r sysadm_r unconfined_r
sysadm_u        user       s0         s0-s0:c0.c1023                 sysadm_r
system_u        user       s0         s0-s0:c0.c1023                 system_r unconfined_r
unconfined_u    user       s0         s0-s0:c0.c1023                 system_r unconfined_r
user_u          user       s0         s0                             user_r
xguest_u        user       s0         s0                             xguest_r
Comment 2 Zdenek Pytela 2021-02-08 21:28:09 UTC 
There are 2 ways for staff_u users how to get the sysadm_r role: using sudo or newrole. The scenario described in the bz is a correct way, after the change sysadm_r role should be allowed run su. This is not a bug.

It looks it is the documentation which needs improving as there is only one line containing staff_u together with staff_r and staff_t which does not cover changing users roles. Thank you for reporting it.

Also note the user part of context cannot be changed.
Comment 5 W. de Heiden 2021-02-17 07:47:33 UTC 
"There are 2 ways for staff_u users how to get the sysadm_r role: using sudo or newrole." Well, there is a third option; I can login using userx/sysadm_r.com. (when the boolean ssh_sysadm_login is enabled)
Comment 7 Zdenek Pytela 2021-03-25 16:42:57 UTC 
The problem reported in this bz is not a selinux-policy bug.
The documentation ambiguity will eventually be addressed by distinguishing between users and roles.
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