Re: [RFC][PATCH] audit: log join and part events to the read-only multicast log socket

Richard Guy Briggs
2014-10-07T19:39:51Z

On 14/10/07, Eric Paris wrote:
> On Tue, 2014-10-07 at 14:23 -0400, Richard Guy Briggs wrote:
> > Log the event when a client attempts to connect to the netlink audit multicast
> > socket, requiring CAP_AUDIT_READ capability, binding to the AUDIT_NLGRP_READLOG
> > group. Log the disconnect too.
> >
> > Sample output:
> > time->Tue Oct 7 14:15:19 2014
> > type=UNKNOWN[1348] msg=audit(1412705719.316:117): auid=0 uid=0 gid=0 ses=1 pid=3552 comm="audit-multicast" exe="/home/rgb/rgb/git/audit-multicast-listen/audit-multicast-listen" subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 group=0 op=connect res=1
> >
> > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> > ---
> > For some reason unbind isn't being called on disconnect. I suspect missing
> > plumbing in netlink. Investigation needed...
> >
> > include/uapi/linux/audit.h | 1 +
> > kernel/audit.c | 46 ++++++++++++++++++++++++++++++++++++++++++-
> > 2 files changed, 45 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> > index 4d100c8..7fa6e8f 100644
> > --- a/include/uapi/linux/audit.h
> > +++ b/include/uapi/linux/audit.h
> > @@ -110,6 +110,7 @@
> > #define AUDIT_SECCOMP 1326 /* Secure Computing event */
> > #define AUDIT_PROCTITLE 1327 /* Proctitle emit event */
> > #define AUDIT_FEATURE_CHANGE 1328 /* audit log listing feature changes */
> > +#define AUDIT_EVENT_LISTENER 1348 /* task joined multicast read socket */
> >
> > #define AUDIT_AVC 1400 /* SE Linux avc denial or grant */
> > #define AUDIT_SELINUX_ERR 1401 /* Internal SE Linux Errors */
> > diff --git a/kernel/audit.c b/kernel/audit.c
> > index 53bb39b..74c81a7 100644
> > --- a/kernel/audit.c
> > +++ b/kernel/audit.c
> > @@ -1108,13 +1108,54 @@ static void audit_receive(struct sk_buff *skb)
> > mutex_unlock(&audit_cmd_mutex);
> > }
> >
> > +static void audit_log_bind(int group, char *op, int err)
> > +{
> > + struct audit_buffer *ab;
> > + char comm[sizeof(current->comm)];
> > + struct mm_struct *mm = current->mm;
> > +
> > + ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_EVENT_LISTENER);
> > + if (!ab)
> > + return;
> > +
> > + audit_log_format(ab, "auid=%d",
> > + from_kuid(&init_user_ns, audit_get_loginuid(current)));
> > + audit_log_format(ab, " uid=%d",
> > + from_kuid(&init_user_ns, current_uid()));
> > + audit_log_format(ab, " gid=%d",
> > + from_kgid(&init_user_ns, current_gid()));
> > + audit_log_format(ab, " ses=%d", audit_get_sessionid(current));
> > + audit_log_format(ab, " pid=%d", task_pid_nr(current));
> > + audit_log_format(ab, " comm=");
> > + audit_log_untrustedstring(ab, get_task_comm(comm, current));
> > + if (mm) {
> > + down_read(&mm->mmap_sem);
> > + if (mm->exe_file)
> > + audit_log_d_path(ab, " exe=", &mm->exe_file->f_path);
> > + up_read(&mm->mmap_sem);
> > + } else
> > + audit_log_format(ab, " exe=(null)");
> > + audit_log_task_context(ab); /* subj= */
>
> super crazy yuck. audit_log_task_info() ??

I agree. I already suggested that a while ago. I'd love to. sgrubb
thinks it dumps way too much info. We still haven't got a definitive
answer about what is enough and what is too much info for any given type
of record.

I also thought of moving audit_log_task() from auditsc.c to audit.c
and using that. For that matter, both audit_log_task() and
audit_log_task_info() could use audit_log_session_info(), but they are
in slightly different order of keywords which will upset sgrubb's
parser.

What to do?

Another paragraph I'd like to see added to
http://people.redhat.com/sgrubb/audit/audit-parse.txt
would be a "canonical order" of keywords. However, that discussion went
nowhere. Would it be reasonable to suggest only two possible orders
instead of the almost infinite iterations possible and declare a
standard order of keywords and gradually move to it?

> > + audit_log_format(ab, " group=%d", group);
>
> group seems like too easily confused a name.

"multicast_group" or "mc_group"?

> > + audit_log_format(ab, " op=%s", op);
> > + audit_log_format(ab, " res=%d", !err);
> > + audit_log_end(ab);
> > +}
> > +
> > /* Run custom bind function on netlink socket group connect or bind requests. */
> > static int audit_bind(int group)
> > {
> > + int err = 0;
> > +
> > if (!capable(CAP_AUDIT_READ))
> > - return -EPERM;
> > + err = -EPERM;
> > + audit_log_bind(group, "connect", err);
> > + return err;
> > +}
> >
> > - return 0;
> > +static void audit_unbind(int group)
> > +{
> > + audit_log_bind(group, "disconnect", 0);
> > }
> >
> > static int __net_init audit_net_init(struct net *net)
> > @@ -1124,6 +1165,7 @@ static int __net_init audit_net_init(struct net *net)
> > .bind = audit_bind,
> > .flags = NL_CFG_F_NONROOT_RECV,
> > .groups = AUDIT_NLGRP_MAX,
> > + .unbind = audit_unbind,
> > };
> >
> > struct audit_net *aunet = net_generic(net, audit_net_id);
>
>

- RGB

--
Richard Guy Briggs <rbriggs@redhat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545