I'm 100% on board with requiring SELinux to be enabled in targeted mode
moving forward.
The SIMP (
https://github.com/NationalSecurityAgency/SIMP) stack runs with
both SELinux targetd mode enabled and FIPS mode enabled in all of our tests
and in our default installation. We identify where there are issues and we
write custom policies as necessary to make our applications function
properly.
I don't know that I would restrict network connections by default (we
don't....yet) but it's certainly something to strive toward. As is all
outbound connections blocked by IPTables by default. (If my phone can do
it, it shouldn't be a giant hurdle)
The SELinux ecosystem has improved to the point where it is usable and
maintainable by most administrators. That said, there does need to be the
understanding that the process for moving forward if SELinux does not work
should be:
1) Set SELinux to permissive on that system (never disable it or your
contexts will be a mess when you try to enable it later)
2) Create an action plan to create the proper policy for your application
3) Create the application policy
4) Implement the application policy
5) Re-enable SELinux in targeted mode
Any broken policy, shipped by a vendor, should be seen as a high priority
incident for that vendor and a patch should be shipped publicly as quickly
as feasible.
The SELinux community seems to have also gotten to the point where there is
some realization that some policy is better than no policy. So that's a big
win overall. You may end up with a weaker policy surrounding your
application than you would like but that's 100% better than disabling
SELinux across the system for one application.
Thanks,
Trevor
On Mon, Mar 21, 2016 at 12:12 PM, Shawn Wells <shawn(a)redhat.com> wrote:
On 3/21/16 10:44 AM, Šimon Lukašík wrote:
On 03/16/2016 07:26 PM, Mackanick, Jason W CIV DISA RE (US) wrote:
I am here with Shawn Wells today and we would like your help in developing the
requirements for a possible inclusion of SELinux requirements to be included in the RHEL7
STIG. As we move away from legacy file permissions to type enforcement, we would like to
work with the community to understand security relevant configuration options such as
SELinux Booleans used in operational environments. To calm any fears associated with
SELinux, we are only considering targeted policy and not the MLS enablement. Shawn will
be working to gather your input. Any of your input would be appreciated if we could get
it by Tuesday March 22, 2016 at the end of business.
Hello Jason,
After talking with selinux crew here in Red Hat, I have learned that
defaults for selinux booleans are set rather defensively. The default is
always the more secure unless too generic use-case would be restricted.
There is over 300 houndred selinux booleans in Red Hat Enterprise Linux
7. I wonder where we can start. Or do you have some specific booleans in
mind?
Perhaps it makes sense to go through these 300 hundreds and put them
into some kind of buckets? Something like
booleans that should absolutely always be true
booleans that should always be false
booleans that default to true, but operators may often need to turn
them false
...
booleans that default to true, but stig advices to keep them false
...
Thoughts?
To ensure everyone is on the same page of booleans, here's a list of the
~300 RHEL7 booleans (output of 'semanage boolean -l'):
http://people.redhat.com/swells/boolean_list.txt
One of the things discussed with DISA was proper scoping of what a RHEL7
STIG looks like. In the past, the RHEL STIGs have been a catch-all and
included configuration settings for things like OpenLDAP Server, HTTPD, and
other 3rd party software (defined as non Operation System functionality).
An example is the "all software library files must be {owned grouped
chmod'd}" rules. In such a case, the RHEL STIG *should* cover RHEL-provided
library files under /usr/lib/{kernel systemd} directories, but not
/usr/lib/3rd_party_app.
Part of this descoping is the reflection that DISA's Application SRG
[0][1] has been maturing. 3rd party software deployments, such as java
middleware servers, should be covered by the Application SRG requirements.
Not lumped into the Operating System STIG.
RHEL7 may ship SELinux booleans for 3rd party software (e.g.
httpd_can_connect_mythtv, or ftpd_connect_db) however their existence
doesn't correlate to inclusion in the *operating system* STIG. The above
booleans would appropriately placed in the Apache STIG or FTP Server STIG,
while the RHEL STIG should ensure SELinux is enforcing and should have
system-level booleans set (e.g. selinuxuser_execmod,
use_ecryptfs_home_dirs, staff_exec_content).
Your buckets idea is really great. Through the above lens, perhaps we can
modify the groupings to something like below:
- Operating System booleans that should be true
- Operating System booleans that should be false
- Non-OS booleans to include in 3rd party STIGs (helping DISA identify
these will expedite their inclusion in things like Apache and JBoss STIGs).
When writing XCCDF rules, their description tag will included cases where
modification of setting may be called for. The OVAL side can use
selinuxboolean_test to automate everything. Thankfully remediation is a
bash 1-liner.
[0]
http://iasecontent.disa.mil/stigs/zip/Oct2015/U_Application_Server_V2R2_S...
[1]
http://iase.disa.mil/stigs/Documents/u_application_server_srg_v2_release_...
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Trevor Vaughan
Vice President, Onyx Point, Inc
(410) 541-6699
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