From: Jonathan Calmels <jcalmels@3xx0.net>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: brauner@kernel.org, Luis Chamberlain <mcgrof@kernel.org>,
Kees Cook <keescook@chromium.org>,
Joel Granados <j.granados@samsung.com>,
Serge Hallyn <serge@hallyn.com>,
Paul Moore <paul@paul-moore.com>,
James Morris <jmorris@namei.org>,
David Howells <dhowells@redhat.com>,
Jarkko Sakkinen <jarkko@kernel.org>,
containers@lists.linux.dev, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org,
linux-security-module@vger.kernel.org, keyrings@vger.kernel.org
Subject: Re: [PATCH 1/3] capabilities: user namespace capabilities
Date: Fri, 17 May 2024 11:02:23 -0700 [thread overview]
Message-ID: <mya7cjq5yzf4xc53un65zia2bwp45mbrt5ys67mgr4azn3phet@o54svegibxze> (raw)
In-Reply-To: <87jzjsa57k.fsf@email.froward.int.ebiederm.org>
> > On Fri, May 17, 2024 at 06:32:46AM GMT, Eric W. Biederman wrote:
> As I read your introduction you were justifying the introduction
> of a new security mechanism with the observation that distributions
> were carrying distribution specific patches.
>
> To the best of my knowledge distribution specific patches and
> distributions disabling user namespaces have been gone for quite a
> while. So if that has changed recently I would like to know.
On the top of my head:
- RHEL based:
namespace.unpriv_enable
user_namespace.enable
- Arch/Debian based:
kernel.unprivileged_userns_clone
- Ubuntu based:
kernel.apparmor_restrict_unprivileged_userns
I'm not sure which exact version those apply to, but it's definitely
still out there.
The observation is that while you can disable namespaces today, in
practice it breaks userspace in various ways. Hence, being able to
control capabilities is a better way to approach it.
For example, today's big hammer to prevent CAP_NET_ADMIN in userns:
# sysctl -qw user.max_net_namespaces=0
$ unshare -U -r -n ip tuntap add mode tap tap0 && echo OK
unshare: unshare failed: No space left on device
With patch, this becomes manageable:
# capsh --drop=cap_net_admin --secbits=$((1 << 8)) --user=$USER -- \
-c 'unshare -U -r -n ip tuntap add mode tap tap0 && echo OK'
ioctl(TUNSETIFF): Operation not permitted
next prev parent reply other threads:[~2024-05-17 17:57 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-16 9:22 [PATCH 0/3] Introduce user namespace capabilities Jonathan Calmels
2024-05-16 9:22 ` [PATCH 1/3] capabilities: " Jonathan Calmels
2024-05-16 12:27 ` Jarkko Sakkinen
2024-05-16 22:07 ` John Johansen
2024-05-17 10:51 ` Jonathan Calmels
2024-05-17 11:59 ` John Johansen
2024-05-18 3:50 ` Jonathan Calmels
2024-05-18 12:27 ` John Johansen
2024-05-19 1:33 ` Jonathan Calmels
2024-05-17 11:32 ` Eric W. Biederman
2024-05-17 11:55 ` Jonathan Calmels
2024-05-17 12:48 ` John Johansen
2024-05-17 14:22 ` Eric W. Biederman
2024-05-17 18:02 ` Jonathan Calmels [this message]
2024-05-21 15:52 ` John Johansen
2024-05-20 3:30 ` Serge E. Hallyn
2024-05-20 3:36 ` Serge E. Hallyn
2024-05-16 9:22 ` [PATCH 2/3] capabilities: add securebit for strict userns caps Jonathan Calmels
2024-05-16 12:42 ` Jarkko Sakkinen
2024-05-20 3:38 ` Serge E. Hallyn
2024-05-16 9:22 ` [PATCH 3/3] capabilities: add cap userns sysctl mask Jonathan Calmels
2024-05-16 12:44 ` Jarkko Sakkinen
2024-05-20 3:38 ` Serge E. Hallyn
2024-05-20 13:30 ` Tycho Andersen
2024-05-20 19:25 ` Jonathan Calmels
2024-05-20 21:13 ` Tycho Andersen
2024-05-20 22:12 ` Jarkko Sakkinen
2024-05-21 14:29 ` Tycho Andersen
2024-05-21 14:45 ` Jarkko Sakkinen
2024-05-16 13:30 ` [PATCH 0/3] Introduce user namespace capabilities Ben Boeckel
2024-05-16 13:36 ` Jarkko Sakkinen
2024-05-17 10:00 ` Jonathan Calmels
2024-05-16 16:23 ` Paul Moore
2024-05-16 17:18 ` Jarkko Sakkinen
2024-05-16 19:07 ` Casey Schaufler
2024-05-16 19:29 ` Jarkko Sakkinen
2024-05-16 19:31 ` Jarkko Sakkinen
2024-05-16 20:00 ` Jarkko Sakkinen
2024-05-17 11:42 ` Jonathan Calmels
2024-05-17 17:53 ` Casey Schaufler
2024-05-17 19:11 ` Jonathan Calmels
2024-05-18 11:08 ` Jarkko Sakkinen
2024-05-18 11:17 ` Jarkko Sakkinen
2024-05-18 11:21 ` Jarkko Sakkinen
2024-05-21 13:57 ` John Johansen
2024-05-21 14:12 ` Jarkko Sakkinen
2024-05-21 14:45 ` John Johansen
2024-05-22 0:45 ` Jonathan Calmels
2024-05-31 7:43 ` John Johansen
2024-05-18 12:20 ` Serge Hallyn
2024-05-19 17:03 ` Casey Schaufler
2024-05-20 0:54 ` Jonathan Calmels
2024-05-21 14:29 ` John Johansen
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
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=mya7cjq5yzf4xc53un65zia2bwp45mbrt5ys67mgr4azn3phet@o54svegibxze \
--to=jcalmels@3xx0.net \
--cc=brauner@kernel.org \
--cc=containers@lists.linux.dev \
--cc=dhowells@redhat.com \
--cc=ebiederm@xmission.com \
--cc=j.granados@samsung.com \
--cc=jarkko@kernel.org \
--cc=jmorris@namei.org \
--cc=keescook@chromium.org \
--cc=keyrings@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=mcgrof@kernel.org \
--cc=paul@paul-moore.com \
--cc=serge@hallyn.com \
/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.
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).