From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Stefan Berger <stefanb@linux.vnet.ibm.com>,
ebiederm@xmission.com, containers@lists.linux-foundation.org
Cc: lkp@01.org, xiaolong.ye@intel.com, linux-kernel@vger.kernel.org,
zohar@linux.vnet.ibm.com, serge@hallyn.com, tycho@docker.com,
christian.brauner@mailbox.org, vgoyal@redhat.com,
amir73il@gmail.com, linux-security-module@vger.kernel.org
Subject: Re: [PATCH 0/3] Enable namespaced file capabilities
Date: Thu, 22 Jun 2017 16:29:21 -0700 [thread overview]
Message-ID: <1498174161.7636.4.camel@HansenPartnership.com> (raw)
In-Reply-To: <1498157989-11814-1-git-send-email-stefanb@linux.vnet.ibm.com>
On Thu, 2017-06-22 at 14:59 -0400, Stefan Berger wrote:
> This series of patches primary goal is to enable file capabilities
> in user namespaces without affecting the file capabilities that are
> effective on the host. This is to prevent that any unprivileged user
> on the host maps his own uid to root in a private namespace, writes
> the xattr, and executes the file with privilege on the host.
>
> We achieve this goal by writing extended attributes with a different
> name when a user namespace is used. If for example the root user
> in a user namespace writes the security.capability xattr, the name
> of the xattr that is actually written is encoded as
> security.capability@uid=1000 for root mapped to uid 1000 on the host.
> When listing the xattrs on the host, the existing security.capability
> as well as the security.capability@uid=1000 will be shown. Inside the
> namespace only 'security.capability', with the value of
> security.capability@uid=1000, is visible.
I'm a bit bothered by the @uid=1000 suffix. What if I want to use this
capability but am dynamically mapping the namespaces (i.e. I know I
want unprivileged root, but I'm going to dynamically select the range
to map based on what's currently available on the orchestration
system). If we stick with the @uid=X suffix, then dynamic mapping
won't work because X is potentially different each time and there'll be
a name mismatch in my xattrs. Why not just make the suffix @uid, which
means if root is mapped to any unprivileged uid then we pick this up
otherwise we go with the unsuffixed property?
As far as I can see there's no real advantage to discriminating userns
specific xattrs based on where root is mapped to, unless there's a use
case I'm missing?
James
next prev parent reply other threads:[~2017-06-22 23:29 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-22 18:59 [PATCH 0/3] Enable namespaced file capabilities Stefan Berger
2017-06-22 18:59 ` [PATCH 1/3] xattr: Enable security.capability in user namespaces Stefan Berger
2017-06-24 21:02 ` kbuild test robot
2017-06-24 21:02 ` [PATCH] xattr: fix kstrdup.cocci warnings kbuild test robot
2017-06-22 18:59 ` [PATCH 2/3] Enable capabilities of files from shared filesystem Stefan Berger
2017-06-22 18:59 ` [PATCH 3/3] Enable security.selinux in user namespaces Stefan Berger
2017-06-23 20:30 ` Stephen Smalley
2017-06-23 23:41 ` Stefan Berger
2017-06-22 19:59 ` [PATCH 0/3] Enable namespaced file capabilities Casey Schaufler
2017-06-22 20:12 ` Stefan Berger
2017-06-22 20:33 ` Casey Schaufler
2017-06-22 21:03 ` Stefan Berger
2017-06-22 21:09 ` Serge E. Hallyn
2017-06-22 22:40 ` Casey Schaufler
2017-06-22 23:07 ` Serge E. Hallyn
2017-06-22 23:29 ` James Bottomley [this message]
2017-06-22 23:32 ` Serge E. Hallyn
2017-06-22 23:36 ` Serge E. Hallyn
2017-06-23 0:13 ` James Bottomley
2017-06-23 1:19 ` Serge E. Hallyn
2017-06-23 17:37 ` Eric W. Biederman
2017-06-23 18:39 ` Serge E. Hallyn
2017-06-23 7:01 ` Amir Goldstein
2017-06-23 16:00 ` Serge E. Hallyn
2017-06-23 16:16 ` Casey Schaufler
2017-06-23 16:30 ` Serge E. Hallyn
2017-06-23 16:53 ` Casey Schaufler
2017-06-23 17:01 ` Serge E. Hallyn
2017-06-23 17:49 ` Eric W. Biederman
2017-06-23 18:32 ` Serge E. Hallyn
2017-06-23 17:07 ` James Bottomley
2017-06-23 17:20 ` Serge E. Hallyn
2017-06-23 17:38 ` Stefan Berger
2017-06-23 18:34 ` Serge E. Hallyn
2017-06-23 18:08 ` Stefan Berger
2017-06-23 18:35 ` Serge E. Hallyn
2017-06-23 20:30 ` Casey Schaufler
2017-06-23 23:09 ` Stefan Berger
2017-06-23 23:51 ` Casey Schaufler
2017-06-28 5:41 ` Serge E. Hallyn
2017-06-28 7:18 ` Amir Goldstein
2017-06-28 14:04 ` Stefan Berger
2017-06-28 14:28 ` Serge E. Hallyn
2017-06-23 20:09 ` Vivek Goyal
2017-06-23 20:17 ` Serge E. Hallyn
2017-06-23 20:36 ` Vivek Goyal
2017-06-23 20:51 ` Serge E. Hallyn
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