From: Maxim Cournoyer <maxim.cournoyer@gmail.com>
To: "Ludovic Courtès" <ludo@gnu.org>
Cc: othacehe@gnu.org, 54786@debbugs.gnu.org
Subject: bug#54786: Installation tests are failing
Date: Sat, 04 Jun 2022 00:37:33 -0400 [thread overview]
Message-ID: <874k11ujqq.fsf@gmail.com> (raw)
In-Reply-To: <87v8tilrsh.fsf@gnu.org> ("Ludovic Courtès"'s message of "Thu, 02 Jun 2022 22:43:58 +0200")
Hi Ludovic!
Ludovic Courtès <ludo@gnu.org> writes:
> Howdy!
>
> Maxim Cournoyer <maxim.cournoyer@gmail.com> skribis:
[...]
>> I reviewed how that works, and it'd be easy; I just didn't see the
>> incentive yet (there's no composition needed for the service, and it'd
>> make the definition slightly less readable). If you tell me
>> mark+forkexec-constructor/container is going the way of the Dodo though,
>> that's a good enough incentive :-).
That turns out to be bit problematic; dbus-daemon must not run in its
own user namespace (CLONE_NEWUSER) as it wants to validate user/group
IDs. That's probably the reason it was working with
'make-forkexec-constructor/container', as this was dropping the user and
net namespaces, contrary to least-authority, which uses them all.
The problem then seems to be that since we need CAP_SYS_ADMIN when
dropping the user namespace, as CLONE_NEWUSER is what gives us
superpowers. Per 'man user_namespaces':
The child process created by clone(2) with the CLONE_NEWUSER flag starts
out with a complete set of capabilities in the new user namespace.
Which means that if we combine something like (untested):
--8<---------------cut here---------------start------------->8---
(make-forkexec-constructor
(least-authority
(list (file-append coreutils "/bin/true"))
(mappings (delq 'user %namespaces))
#:user "nobody"
#:group "nobody"))
--8<---------------cut here---------------end--------------->8---
the make-forkexec-constructor will switch to the non-privileged user
before the clone call is made, and it will fail with EPERM.
When using 'make-forkexec-constructor/container', the clone(2) call
happens before switching user, thus as 'root' in Shepherd, which
explains why it works.
I'm not sure how it could be fixed; it seems the user changing business
would need to be handled by the least-authority-wrapper code? And the
make-forkexec-constructor would probably need to detect that command is
a pola wrapper and then avoid changing the user/group itself to not
interfere.
To be continued!
Maxim
next prev parent reply other threads:[~2022-06-04 4:49 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-08 9:51 bug#54786: Installation tests are failing Mathieu Othacehe
2022-04-08 15:10 ` Mathieu Othacehe
2022-04-28 7:22 ` Mathieu Othacehe
2022-04-28 19:19 ` Ludovic Courtès
2022-04-29 19:50 ` Ludovic Courtès
2022-04-30 13:02 ` Mathieu Othacehe
2022-05-01 13:26 ` Ludovic Courtès
2022-05-25 3:43 ` Maxim Cournoyer
2022-05-28 21:29 ` Ludovic Courtès
2022-05-31 16:44 ` bug#54786: [PATCH] services: jami: Modernize to adjust to Shepherd 0.9+ changes Maxim Cournoyer
2022-06-01 9:54 ` bug#54786: Installation tests are failing Ludovic Courtès
2022-06-01 13:10 ` Maxim Cournoyer
2022-06-02 13:13 ` Ludovic Courtès
2022-06-02 17:24 ` Maxim Cournoyer
2022-06-02 20:43 ` Ludovic Courtès
2022-06-04 4:37 ` Maxim Cournoyer [this message]
2022-06-07 14:00 ` Ludovic Courtès
2022-06-08 0:58 ` bokr
2022-06-11 4:18 ` Maxim Cournoyer
2022-08-09 14:20 ` Mathieu Othacehe
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://guix.gnu.org/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=874k11ujqq.fsf@gmail.com \
--to=maxim.cournoyer@gmail.com \
--cc=54786@debbugs.gnu.org \
--cc=ludo@gnu.org \
--cc=othacehe@gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.savannah.gnu.org/cgit/guix.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).