audit: add netlink audit protocol bind to check capabilities on multicast join

Register a netlink per-protocol bind fuction for audit to check userspace
process capabilities before allowing a multicast group connection.

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 0 deletions

diff --git a/kernel/audit.c b/kernel/audit.c
index 7c2893602d06..223cb746f141 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1076,10 +1076,20 @@ static void audit_receive(struct sk_buff  *skb)
         mutex_unlock(&audit_cmd_mutex);
 }
 
+/* Run custom bind function on netlink socket group connect or bind requests. */
+static int audit_bind(int group)
+{
+        if (!capable(CAP_AUDIT_READ))
+                return -EPERM;
+
+        return 0;
+}
+
 static int __net_init audit_net_init(struct net *net)
 {
         struct netlink_kernel_cfg cfg = {
                 .input  = audit_receive,
+                .bind   = audit_bind,
         };
 
         struct audit_net *aunet = net_generic(net, audit_net_id);