Setting context in early boot

[Frederick Grose]

I have a general scoping question on setting SELinux context on files/directories during
early boot.
I'm working on a feature in dracut to implement general stacking of filesystem
hierarchies via OverlayFS for the root filesystem within the dmsquash-live-root module.
How should I address the setting of context for new files, directories, or links needed to
assemble the components for the OverlayFS mount?

For example, when I 
  mkdir -m 0755 -p --context=system_u:object_r:root_t:s0 /run/somemountpoint
I get this warning in the journal:
  mkdir: warning: ignoring --context; it requires an SELinux/SMACK-enabled kernel

If the SELinux code is not active at this early stage, what is to be done?

[justina colmena ~biz]

On September 5, 2022 10:52:39 AM AKDT, Frederick Grose <fgrose(a)gmail.com&gt; wrote:
> If the SELinux code is not active at this early stage, what is to be done?
>  
Some parts of it are still functional, curiously enough, but SELinux is mostly an
abandoned NSA government surveillance intelligence project once intended or perhaps
proposed for dealing with sensitive departmental information at Official Use Only,
Confidential, Secret, and Top Secret levels etc. -- but since online hacking, industrial
espionage, and thievery in law are always much more profitable than actual
"security" (national or otherwise)  -- the only *real* answer you will likely
get on this list is akin to the sound of your own voice echoing through the concrete
hallways of a long-abandoned federal government military industrial complex building.
-- 
Sent from my Android device with K-9 Mail. Please excuse my brevity.

[Ondrej Mosnacek]

On Mon, Sep 5, 2022 at 8:52 PM Frederick Grose <fgrose(a)gmail.com&gt; wrote:
>  I have a general scoping question on setting SELinux context on
> files/directories during early boot.
>  I'm working on a feature in dracut to implement general stacking of filesystem
> hierarchies via OverlayFS for the root filesystem within the dmsquash-live-root module.
>  How should I address the setting of context for new files, directories, or links needed
> to assemble the components for the OverlayFS mount?
>
>  For example, when I
>    mkdir -m 0755 -p --context=system_u:object_r:root_t:s0 /run/somemountpoint
>  I get this warning in the journal:
>    mkdir: warning: ignoring --context; it requires an SELinux/SMACK-enabled kernel
>
>  If the SELinux code is not active at this early stage, what is to be done? 
Tools that use libselinux to set labels will probably refuse to work
with SELinux policy not yet loaded, but if you have a recent enough
kernel (5.5+), it should be possible to set the extended attribute
manually - for example using setfattr:

mkdir -m 0755 -p /run/somemountpoint
setfattr -n security.selinux -v system_u:object_r:root_t:s0 /run/somemountpoint

-- 
Ondrej Mosnacek
Senior Software Engineer, Linux Security - SELinux kernel
Red Hat, Inc.