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

Richard Guy Briggs
2014-10-07T18:23:19Z

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= */
+ audit_log_format(ab, " group=%d", 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);
--
1.7.1