linux-kernel - Re: [PATCH] audit: allow logging of user events in non-initial namespace.

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Date:   Mon, 10 May 2021 18:48:16 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Michael Weiß <michael.weiss@...ec.fraunhofer.de>
Cc:     Richard Guy Briggs <rgb@...hat.com>,
        Eric Paris <eparis@...hat.com>, linux-audit@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] audit: allow logging of user events in non-initial namespace.

On Sun, May 9, 2021 at 2:33 PM Michael Weiß
<michael.weiss@...ec.fraunhofer.de> wrote:
>
> Audit subsystem was disabled in total for user namespaces other than
> the initial namespace.
>
> If audit is enabled by kernel command line or audtid in initial namespace,
> it is now possible to allow at least logging of userspace applications
> inside of non-initial namespaces if CAP_AUDIT_WRITE in the corresponding
> namespace is held.
>
> This allows logging of, e.g., PAM or opensshd inside user namespaced
> system containers.
>
> Signed-off-by: Michael Weiß <michael.weiss@...ec.fraunhofer.de>
> ---
>  kernel/audit.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)

I think this needs to wait on the audit container ID patchset to land.

> diff --git a/kernel/audit.c b/kernel/audit.c
> index 121d37e700a6..b5cc0669c3d7 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -1012,7 +1012,13 @@ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)
>          * userspace will reject all logins.  This should be removed when we
>          * support non init namespaces!!
>          */
> -       if (current_user_ns() != &init_user_ns)
> +       /*
> +        * If audit is enabled by kernel command line or audtid in the initial
> +        * namespace allow at least logging of userspace applications inside of
> +        * non-initial namespaces according to CAP_AUDIT_WRITE is held in the
> +        * corresponding namespace.
> +        */
> +       if ((current_user_ns() != &init_user_ns) && !audit_enabled)
>                 return -ECONNREFUSED;
>
>         switch (msg_type) {
> @@ -1043,7 +1049,7 @@ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)
>         case AUDIT_USER:
>         case AUDIT_FIRST_USER_MSG ... AUDIT_LAST_USER_MSG:
>         case AUDIT_FIRST_USER_MSG2 ... AUDIT_LAST_USER_MSG2:
> -               if (!netlink_capable(skb, CAP_AUDIT_WRITE))
> +               if (!netlink_ns_capable(skb, current_user_ns(), CAP_AUDIT_WRITE))
>                         err = -EPERM;
>                 break;
>         default:  /* bad msg */
> --
> 2.20.1

-- 
paul moore
www.paul-moore.com