Re: [PATCH ghak90 (was ghak32) V4 02/10] audit: add container id

[Paul Moore]

On Tue, Jul 31, 2018 at 4:11 PM Richard Guy Briggs <rgb@xxxxxxxxxx> wrote:
>
> Implement the proc fs write to set the audit container identifier of a
> process, emitting an AUDIT_CONTAINER_OP record to document the event.
>
> This is a write from the container orchestrator task to a proc entry of
> the form /proc/PID/audit_containerid where PID is the process ID of the
> newly created task that is to become the first task in a container, or
> an additional task added to a container.
>
> The write expects up to a u64 value (unset: 18446744073709551615).
>
> The writer must have capability CAP_AUDIT_CONTROL.
>
> This will produce a record such as this:
>   type=CONTAINER_ID msg=audit(2018-06-06 12:39:29.636:26949) : op=set opid=2209 old-contid=18446744073709551615 contid=123456 pid=628 auid=root uid=root tty=ttyS0 ses=1 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 comm=bash exe=/usr/bin/bash res=yes

You need to update the record type in the example above.

> The "op" field indicates an initial set.  The "pid" to "ses" fields are
> the orchestrator while the "opid" field is the object's PID, the process
> being "contained".  Old and new audit container identifier values are
> given in the "contid" fields, while res indicates its success.

I understand Steve's concern around the "op" field, but I think it
might be a bit premature to think we might not need to do some sort of
audit container ID management in the future that would want to make
use of the CONTAINER_OP message type.  I would like to see the "op"
field preserved.

> It is not permitted to unset the audit container identifier.
> A child inherits its parent's audit container identifier.
>
> See: https://github.com/linux-audit/audit-kernel/issues/90
> See: https://github.com/linux-audit/audit-userspace/issues/51
> See: https://github.com/linux-audit/audit-testsuite/issues/64
> See: https://github.com/linux-audit/audit-kernel/wiki/RFE-Audit-Container-ID
>
> Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> Acked-by: Serge Hallyn <serge@xxxxxxxxxx>
> Acked-by: Steve Grubb <sgrubb@xxxxxxxxxx>
> ---
>  fs/proc/base.c             | 37 +++++++++++++++++++++++++
>  include/linux/audit.h      | 24 ++++++++++++++++
>  include/uapi/linux/audit.h |  2 ++
>  kernel/auditsc.c           | 68 ++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 131 insertions(+)

...

> @@ -2112,6 +2114,72 @@ int audit_set_loginuid(kuid_t loginuid)
>  }
>
>  /**
> + * audit_set_contid - set current task's audit_context contid
> + * @contid: contid value
> + *
> + * Returns 0 on success, -EPERM on permission failure.
> + *
> + * Called (set) from fs/proc/base.c::proc_contid_write().
> + */
> +int audit_set_contid(struct task_struct *task, u64 contid)
> +{
> +       u64 oldcontid;
> +       int rc = 0;
> +       struct audit_buffer *ab;
> +       uid_t uid;
> +       struct tty_struct *tty;
> +       char comm[sizeof(current->comm)];
> +
> +       task_lock(task);
> +       /* Can't set if audit disabled */
> +       if (!task->audit) {
> +               task_unlock(task);
> +               return -ENOPROTOOPT;
> +       }
> +       oldcontid = audit_get_contid(task);
> +       read_lock(&tasklist_lock);

I assume lockdep was happy with nesting the tasklist_lock inside the task lock?

> +       /* Don't allow the audit containerid to be unset */
> +       if (!audit_contid_valid(contid))
> +               rc = -EINVAL;
> +       /* if we don't have caps, reject */
> +       else if (!capable(CAP_AUDIT_CONTROL))
> +               rc = -EPERM;
> +       /* if task has children or is not single-threaded, deny */
> +       else if (!list_empty(&task->children))
> +               rc = -EBUSY;
> +       else if (!(thread_group_leader(task) && thread_group_empty(task)))
> +               rc = -EALREADY;
> +       read_unlock(&tasklist_lock);
> +       if (!rc)
> +               task->audit->contid = contid;
> +       task_unlock(task);
> +
> +       if (!audit_enabled)
> +               return rc;
> +
> +       ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_CONTAINER_OP);
> +       if (!ab)
> +               return rc;
> +
> +       uid = from_kuid(&init_user_ns, task_uid(current));
> +       tty = audit_get_tty(current);
> +       audit_log_format(ab, "op=set opid=%d old-contid=%llu contid=%llu pid=%d uid=%u auid=%u tty=%s ses=%u",
> +                        task_tgid_nr(task), oldcontid, contid,
> +                        task_tgid_nr(current), uid,
> +                        from_kuid(&init_user_ns, audit_get_loginuid(current)),
> +                        tty ? tty_name(tty) : "(none)",
> +                        audit_get_sessionid(current));
> +       audit_put_tty(tty);
> +       audit_log_task_context(ab);
> +       audit_log_format(ab, " comm=");
> +       audit_log_untrustedstring(ab, get_task_comm(comm, current));
> +       audit_log_d_path_exe(ab, current->mm);
> +       audit_log_format(ab, " res=%d", !rc);
> +       audit_log_end(ab);
> +       return rc;
> +}

-- 
paul moore
www.paul-moore.com