linux-kernel - Re: [PATCH ghak90 V9 13/13] audit: add capcontid to set contid outside init_user

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Message-ID: <CAHC9VhRvuu-_+gh9ejr0sFDNR6erV2BAig6qrT9gOEB6GczXvw@mail.gmail.com>
Date:   Sun, 5 Jul 2020 11:11:47 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Richard Guy Briggs <rgb@...hat.com>
Cc:     containers@...ts.linux-foundation.org, linux-api@...r.kernel.org,
        Linux-Audit Mailing List <linux-audit@...hat.com>,
        linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        sgrubb@...hat.com, Ondrej Mosnacek <omosnace@...hat.com>,
        dhowells@...hat.com, simo@...hat.com,
        Eric Paris <eparis@...isplace.org>,
        Serge Hallyn <serge@...lyn.com>, ebiederm@...ssion.com,
        nhorman@...driver.com, Dan Walsh <dwalsh@...hat.com>,
        mpatel@...hat.com
Subject: Re: [PATCH ghak90 V9 13/13] audit: add capcontid to set contid
 outside init_user_ns

On Sat, Jun 27, 2020 at 9:24 AM Richard Guy Briggs <rgb@...hat.com> wrote:
>
> Provide a mechanism similar to CAP_AUDIT_CONTROL to explicitly give a
> process in a non-init user namespace the capability to set audit
> container identifiers of individual children.
>
> Provide the /proc/$PID/audit_capcontid interface to capcontid.
> Valid values are: 1==enabled, 0==disabled
>
> Writing a "1" to this special file for the target process $PID will
> enable the target process to set audit container identifiers of its
> descendants.
>
> A process must already have CAP_AUDIT_CONTROL in the initial user
> namespace or have had audit_capcontid enabled by a previous use of this
> feature by its parent on this process in order to be able to enable it
> for another process.  The target process must be a descendant of the
> calling process.
>
> Report this action in new message type AUDIT_SET_CAPCONTID 1022 with
> fields opid= capcontid= old-capcontid=
>
> Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> ---
>  fs/proc/base.c             | 57 +++++++++++++++++++++++++++++++++++++++++++++-
>  include/linux/audit.h      | 14 ++++++++++++
>  include/uapi/linux/audit.h |  1 +
>  kernel/audit.c             | 38 ++++++++++++++++++++++++++++++-
>  4 files changed, 108 insertions(+), 2 deletions(-)

This seems very similar to the capable/ns_capable combination I
mentioned in patch 11/13; any reasons why you feel that this might be
a better approach?  My current thinking is that the capable/ns_capable
approach is preferable as it leverages existing kernel mechanisms and
doesn't require us to reinvent the wheel in the audit subsystem.


--
paul moore
www.paul-moore.com