Initial context for init
by Philip Seeley
Hi all,
Quick question is:
In the targeted policy should init run SystemHigh as it does in the mls
policy?
The background:
We're setting up a targeted system where we confine all users and remove
the unconfined policy module, but we also enable polyinstantiation of /tmp
and /var/tmp.
If we ssh in as a staff_u user phil and elevate to root/sysadm_r then we
have a context of:
staff_u:sysadm_r:sysadm_t:s0-s0:c0.c1023
And therefore /var/tmp is:
drwxrwxrwt. root root system_u:object_r:tmp_t:s0-s0:c0.c1023 /var/tmp
Which is really:
drwxrwxrwt. root root
system_u:object_r:tmp_t:s0-s0:c0.c1023 /var/tmp-inst/system_u:object_r:tmp_t:s0-s0:c0.c1023_phil
The real /var/tmp is:
drwxrwxrwt. root root system_u:object_r:tmp_t:s0 /var/tmp
Now if we use run_init to update an RPM that contains a post install
script, rpm can't create the temporary script file:
# run_init bash -c 'rpm -i
--force /root/libselinux-2.0.94-7.el6.x86_64.rpm'
Authenticating phil.
Password:
error: error creating temporary file /var/tmp/rpm-tmp.atkHTf: Permission
denied
error: Couldn't create temporary file for %post
(libselinux-2.0.94-7.el6.x86_64): Permission denied
Note: you need to use run_init as the rpm might restart a service, e.g. the
sssd rpm.
We've traced this to the /etc/selinux/targeted/contexts/initrc_context file
which contains:
system_u:system_r:initrc_t:s0
So we transition to initrc_t and then to rpm_t without any categories, but
because the polyinstantiated /var/tmp directory has c0.c1023 we get denied.
Normally in targeted init runs unconfined, but we've removed this.
type=AVC msg=audit(1467342325.016:716): avc: denied { read } for
pid=2779 comm="rpm" name="system_u:object_r:tmp_t:s0-s0:c0.c1023_phil"
dev=dm-0 ino=1966082 scontext=system_u:system_r:rpm_t:s0
tcontext=system_u:object_r:tmp_t:s0-s0:c0.c1023 tclass=dir
It works if we change initrc_context to:
system_u:system_r:initrc_t:s0-s0:c0.c1023
We don't see the issue under mls because the default initrc_context is:
system_u:system_r:initrc_t:s0-s15:c0.c1023
We've traces this back through the selinux-policy src RPM and to the
upstream refpolicy and see that config/appconfig-mcs/initrc_context is:
system_u:system_r:initrc_t:s0
whereas config/appconfig-mls/initrc_context is:
system_u:system_r:initrc_t:s0-mls_systemhigh
So under mls init's context is SystemHigh, but under mcs/targeted it
doesn't have any categories.
So the long question is should config/appconfig-mcs/initrc_context really
be:
system_u:system_r:initrc_t:mcs_systemhigh
as it seems odd that the more secure mls policy would run init at
SystemHigh but targeted doesn't.
Thanks
Phil Seeley
4 years, 10 months
- 3
- 3
Re: RHEL 7 consoletype_exec interface issue
by Douglas Brown
Hi,
In RHEL 7 when using the userdom_unpriv_user_template interface to create a new role, it in turn uses the consoletype_exec interface; but when I attempt to insert a policy compiled with this, it says the type consoletype_exec_t doesn’t exist.
N.B. This works on RHEL 6.
Thanks,
Doug
7 years, 2 months
- 3
- 2
A daemon that needs execmem
by Göran Uddeborg
Hello,
It seems I have to use Teamviewer. I downloaded and installed it.
Now I'm trying to put together a policy module to make it run without
putting SELinux in permissive mode.
This program uses a daemon, and for this I've created a new domain:
type teamviewerd_t;
type teamviewerd_exec_t;
init_daemon_domain(teamviewerd_t, teamviewerd_exec_t)
/opt/teamviewer/tv_bin/teamviewerd -- gen_context(system_u:object_r:teamviewerd_exec_t,s0)
Then I started to add "allow" rules. Ausearch tells me I get an AVC
when "init_t" tries to use "execmem". I'm guessing this is because
the execmem test is done before the type transition happens.
Obviously, I don't want to allow init_t the execmem permission in
general. Is there some good way around this? My best idea so far is
to create a wrapper binary, give this wrapper the teamviewerd_exec_t
type, and let it do exec() on the real teamviewerd program. But it
feels a bit clumsy. Are there more direct ways to do it?
7 years, 11 months
- 2
- 2
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