[PATCH 4/6] audit: add netlink audit protocol bind to check capabilities on multicast join

[Richard Guy Briggs]

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@xxxxxxxxxx>
---
 include/uapi/linux/capability.h     |    7 ++++++-
 kernel/audit.c                      |   10 ++++++++++
 security/selinux/include/classmap.h |    2 +-
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/capability.h b/include/uapi/linux/capability.h
index 154dd6d..12c37a1 100644
--- a/include/uapi/linux/capability.h
+++ b/include/uapi/linux/capability.h
@@ -347,7 +347,12 @@ struct vfs_cap_data {
 
 #define CAP_BLOCK_SUSPEND    36
 
-#define CAP_LAST_CAP         CAP_BLOCK_SUSPEND
+/* Allow reading the audit log via multicast netlink socket */
+
+#define CAP_AUDIT_READ		37
+
+
+#define CAP_LAST_CAP         CAP_AUDIT_READ
 
 #define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP)
 
diff --git a/kernel/audit.c b/kernel/audit.c
index 7c28936..223cb74 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);
diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 14d04e6..be491a7 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h
@@ -147,7 +147,7 @@ struct security_class_mapping secclass_map[] = {
 	{ "peer", { "recv", NULL } },
 	{ "capability2",
 	  { "mac_override", "mac_admin", "syslog", "wake_alarm", "block_suspend",
-	    NULL } },
+	    "audit_read", NULL } },
 	{ "kernel_service", { "use_as_override", "create_files_as", NULL } },
 	{ "tun_socket",
 	  { COMMON_SOCK_PERMS, "attach_queue", NULL } },
-- 
1.7.1

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