GNU bug report logs - #31894
Containerize openntpd service

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Efraim Flashner <efraim <at> flashner.co.il>
To: guix-patches <at> gnu.org
Subject: Containerize openntpd service
Date: Tue, 19 Jun 2018 12:31:55 +0300

[Message part 1 (text/plain, inline)]

I tested this patch with the included vm image, using the following
script. After logging in, 'ntpctl -s all' shows openntpd connecting to
the ntp servers and updating the time.

/.$(./pre-inst-env guix environment guix -- ./pre-inst-env guix system vm ~/vm-image.scm) -m 768 -device e1000,netdev=net0 -netdev user,id=net0,hostfwd=tcp::5555-:53


-- 
Efraim Flashner   <efraim <at> flashner.co.il>   אפרים פלשנר
GPG key = A28B F40C 3E55 1372 662D  14F7 41AA E7DC CA3D 8351
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[0001-services-openntpd-Containerize-openntpd-service.patch (text/plain, attachment)]

[vm-image.scm (text/plain, attachment)]

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Message #8 received at 31894 <at> debbugs.gnu.org (full text, mbox):

From: ludo <at> gnu.org (Ludovic Courtès)
To: Efraim Flashner <efraim <at> flashner.co.il>
Cc: 31894 <at> debbugs.gnu.org
Subject: Re: [bug#31894] Containerize openntpd service
Date: Fri, 22 Jun 2018 21:39:01 +0200

Hello Efraim,

Efraim Flashner <efraim <at> flashner.co.il> skribis:

> I tested this patch with the included vm image, using the following
> script. After logging in, 'ntpctl -s all' shows openntpd connecting to
> the ntp servers and updating the time.
>
> /.$(./pre-inst-env guix environment guix -- ./pre-inst-env guix system vm ~/vm-image.scm) -m 768 -device e1000,netdev=net0 -netdev user,id=net0,hostfwd=tcp::5555-:53

[...]

> From 064903c5a976280b95cd9bba17e958e662be605d Mon Sep 17 00:00:00 2001
> From: Efraim Flashner <efraim <at> flashner.co.il>
> Date: Tue, 19 Jun 2018 12:24:47 +0300
> Subject: [PATCH] services: openntpd: Containerize openntpd service.
>
> * gnu/packages/ntp.scm (openntpd)[arguments]: Add 'privsep-path' to
> 'configure-flags and adjust the 'localstatedir' flag.
> * gnu/services/networking.scm (openntpd-shepherd-service): Change the
> start-service command to run in a container, expose '/var/log/openntpd'
> and '/var/lib/openntpd' to the container.
> (openntpd-service-activation): Adjust directories for the changes above.

Neat!  The patch LGTM, especially since you’ve confirmed that it still
works as expected.  :-)

One thing though: could you make sure containerization isn’t redundant
with what OpenNTPD already does?  Namely, could you grep the source for
calls to “chroot”, “unshare”, or “seccomp”?  If it happens to be already
doing one of these things, it may be that using a container brings
little or nothing.

If it’s OK, please push!

While I’m at it, one question about this comment (which was already there):

> +                           ;; When ntpd is daemonized it repeatedly tries to respawn
> +                           ;; while running, leading shepherd to disable it.  To
> +                           ;; prevent spamming stderr, redirect output to logfile.
> +                           #:log-file "/var/log/ntpd"))

What’s described here is expected: when it daemonizes, the initial
process that shepherd spawned terminates immediately, which is why
shepherd tries to respawn it (it cannot guess that there’s in fact a
child process that keeps running.)

The right thing to do for things that daemonize is to use the #:pid-file
option, which instructs shepherd to poll that file.  Should we do this
here?  There are many examples of that, including bitlbee, which is
containerized.

Thanks,
Ludo’.

Message #13 received at 31894-done <at> debbugs.gnu.org (full text, mbox):

From: Efraim Flashner <efraim <at> flashner.co.il>
To: Ludovic Courtès <ludo <at> gnu.org>
Cc: 31894-done <at> debbugs.gnu.org
Subject: Re: [bug#31894] Containerize openntpd service
Date: Tue, 26 Jun 2018 11:25:57 +0300

[Message part 1 (text/plain, inline)]

On Fri, Jun 22, 2018 at 09:39:01PM +0200, Ludovic Courtès wrote:
> Hello Efraim,
> 
> Efraim Flashner <efraim <at> flashner.co.il> skribis:
> 
> > I tested this patch with the included vm image, using the following
> > script. After logging in, 'ntpctl -s all' shows openntpd connecting to
> > the ntp servers and updating the time.
> >
> > /.$(./pre-inst-env guix environment guix -- ./pre-inst-env guix system vm ~/vm-image.scm) -m 768 -device e1000,netdev=net0 -netdev user,id=net0,hostfwd=tcp::5555-:53
> 
> [...]
> 
> > From 064903c5a976280b95cd9bba17e958e662be605d Mon Sep 17 00:00:00 2001
> > From: Efraim Flashner <efraim <at> flashner.co.il>
> > Date: Tue, 19 Jun 2018 12:24:47 +0300
> > Subject: [PATCH] services: openntpd: Containerize openntpd service.
> >
> > * gnu/packages/ntp.scm (openntpd)[arguments]: Add 'privsep-path' to
> > 'configure-flags and adjust the 'localstatedir' flag.
> > * gnu/services/networking.scm (openntpd-shepherd-service): Change the
> > start-service command to run in a container, expose '/var/log/openntpd'
> > and '/var/lib/openntpd' to the container.
> > (openntpd-service-activation): Adjust directories for the changes above.
> 
> Neat!  The patch LGTM, especially since you’ve confirmed that it still
> works as expected.  :-)
> 
> One thing though: could you make sure containerization isn’t redundant
> with what OpenNTPD already does?  Namely, could you grep the source for
> calls to “chroot”, “unshare”, or “seccomp”?  If it happens to be already
> doing one of these things, it may be that using a container brings
> little or nothing.
> 
> If it’s OK, please push!

From grepping the source:

./INSTALL-OpenNTPD always uses Privilege Separation (ie the majority of the
./INSTALL:processing is done as a chroot'ed, unprivileged user).

The code also supports the assertion.

it defaults to /var/empty, unless the --with-privsep-path=path flag is
set, so it looks like my patch is unnecessary after all. :)

> 
> While I’m at it, one question about this comment (which was already there):
> 
> > +                           ;; When ntpd is daemonized it repeatedly tries to respawn
> > +                           ;; while running, leading shepherd to disable it.  To
> > +                           ;; prevent spamming stderr, redirect output to logfile.
> > +                           #:log-file "/var/log/ntpd"))
> 
> What’s described here is expected: when it daemonizes, the initial
> process that shepherd spawned terminates immediately, which is why
> shepherd tries to respawn it (it cannot guess that there’s in fact a
> child process that keeps running.)
> 
> The right thing to do for things that daemonize is to use the #:pid-file
> option, which instructs shepherd to poll that file.  Should we do this
> here?  There are many examples of that, including bitlbee, which is
> containerized.
> 

I'll take a look at that and see if I can fix that.

> Thanks,
> Ludo’.

-- 
Efraim Flashner   <efraim <at> flashner.co.il>   אפרים פלשנר
GPG key = A28B F40C 3E55 1372 662D  14F7 41AA E7DC CA3D 8351
Confidentiality cannot be guaranteed on emails sent or received unencrypted

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Message #16 received at 31894-done <at> debbugs.gnu.org (full text, mbox):

From: ludo <at> gnu.org (Ludovic Courtès)
To: Efraim Flashner <efraim <at> flashner.co.il>
Cc: 31894-done <at> debbugs.gnu.org
Subject: Re: [bug#31894] Containerize openntpd service
Date: Tue, 26 Jun 2018 15:48:34 +0200

Efraim Flashner <efraim <at> flashner.co.il> skribis:

> On Fri, Jun 22, 2018 at 09:39:01PM +0200, Ludovic Courtès wrote:

[...]

>> One thing though: could you make sure containerization isn’t redundant
>> with what OpenNTPD already does?  Namely, could you grep the source for
>> calls to “chroot”, “unshare”, or “seccomp”?  If it happens to be already
>> doing one of these things, it may be that using a container brings
>> little or nothing.
>> 
>> If it’s OK, please push!
>
> From grepping the source:
>
> ./INSTALL-OpenNTPD always uses Privilege Separation (ie the majority of the
> ./INSTALL:processing is done as a chroot'ed, unprivileged user).
>
> The code also supports the assertion.
>
> it defaults to /var/empty, unless the --with-privsep-path=path flag is
> set, so it looks like my patch is unnecessary after all. :)

Heh, alright.  Perhaps you’ll find another candidate for
containerization.  ;-)

Thanks,
Ludo’.

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