[Whonix-devel] [qubes-devel] Require script to run immed. after /rw mount

Tue Apr 18 04:01:01 CEST 2017

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On Tue, Apr 18, 2017 at 01:06:00AM +0000, Patrick Schleizer wrote:
> Marek Marczykowski-Górecki:
> > On Mon, Apr 17, 2017 at 11:06:00PM +0000, Patrick Schleizer wrote:
> >> Marek Marczykowski-Górecki:
> >>> On Mon, Apr 17, 2017 at 10:02:00PM +0000, Patrick Schleizer wrote:
> >>>>> Alternately, mount-dirs.sh could have
> >>>>> a hook that points to a specific user script in /etc.
> >>>
> >>>> User script sounds a bit limited. What about something a little more
> >>>> flexible?
> >>>
> >>>> Untested pseudo code:
> >>>
> >>>> if [ -d /etc/qubes/mount-dirs-post.d ]; then
> >>>>    run-parts /etc/qubes/mount-dirs-post.d
> >>>> fi
> >>>
> >>> IMO this is the way to go. In addition to your VM hardening scripts,
> >>> this could be used also for some /rw initialization, beyond /etc/skel.
> >>> AFAIR there was a need for similar thing to copy Tor Browser there.
> >>>
> >>> As for implementation - do we want it in /etc, /usr/lib, or both (so
> >>> files in /etc could override /usr/lib)?
> > 
> >> Yes in both. Actually in all three. I.e. /etc/, /usr/lib and in
> >> /usr/local (/rw) to make it complete.
> > 
> > No, the whole point about this script is to run something _before_
> > anything gets processed/run from /rw.
> 
> Right. (Scratch that /rw idea.)
> 
> >>> But having both means we can't
> >>> use run-parts :(
> > 
> >> Why not just use above "Untested pseudo code" three times with the
> >> different dirs? :)
> > 
> > Because it will not allow to disable/override a script in /usr/lib by
> > placing a script with the same name in /etc.
> 
> Alright. We can have that feature. Then perhaps let's use bash `source`.
> 
> Each snipped could define an entry function named
> number_main_drop-in-name or so. For example.
> 
> /usr/lib/qubes-mount-dirs.d/50_bind_dirs.conf:
> 
> 50_main_bind_dirs() {
>    /path/to/actual/script
> }
> 
> To disable that, a lexically higher configuration file could just do.
> 
> /etc/qubes-mount-dirs.d/50_bind_dirs.conf:
> 
> 50_main_bind_dirs() {
>    true
> }
> 
> Then the mount-dirs.sh script could `source` all these `.conf`s, and use
> `compgen` to get a list of function names, match these for `_main_`.
> Then run these functions in lexical order.
> 
> Does that look good? If needed, I could as well describe that better or
> write some pseudo code for that. I like this override / configureability
> stuff.

IMO forcing people to writing a bash function in such script is a bad
idea. First of all, many will not do that, breaking this override
schema. If more elaborative script is needed anyway, lets work on full
files, like this:

    IFS=$'\n'
    readarray -t files_basename < <(
        find /usr/lib/qubes-mount-dirs.d /etc/qubes-mount-dirs.d 
        -type f -executable -printf '%f\n' | sort | uniq)

    for f in "${files_basename[@]}"; do
        if [ -x "/etc/qubes-mount-dirs.d/$f" ]; then
            "/etc/qubes-mount-dirs.d/$f"
        elif [ -x "/usr/lib/qubes-mount-dirs.d/$f" ]; then
            "/usr/lib/qubes-mount-dirs.d/$f"
        endif
    done

- -- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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