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

Eric Paris
2014-10-07T19:03:14Z

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() ??

> + audit_log_format(ab, " group=%d", group);

group seems like too easily confused a name.

> + 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);