selinux: Support for the new TUN LSM hooks

Add support for the new TUN LSM hooks: security_tun_dev_create(),
security_tun_dev_post_create() and security_tun_dev_attach().  This includes
the addition of a new object class, tun_socket, which represents the socks
associated with TUN devices.  The _tun_dev_create() and _tun_dev_post_create()
hooks are fairly similar to the standard socket functions but _tun_dev_attach()
is a bit special.  The _tun_dev_attach() is unique because it involves a
domain attaching to an existing TUN device and its associated tun_socket
object, an operation which does not exist with standard sockets and most
closely resembles a relabel operation.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Acked-by: Eric Paris <eparis@parisplace.org>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 58 insertions, 2 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index ac79f9ef2da8..27b4c5527358 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -13,8 +13,8 @@
  *                                         Eric Paris <eparis@redhat.com>
  *  Copyright (C) 2004-2005 Trusted Computer Solutions, Inc.
  *                          <dgoeddel@trustedcs.com>
- *  Copyright (C) 2006, 2007 Hewlett-Packard Development Company, L.P.
- *              Paul Moore <paul.moore@hp.com>
+ *  Copyright (C) 2006, 2007, 2009 Hewlett-Packard Development Company, L.P.
+ *      Paul Moore <paul.moore@hp.com>
  *  Copyright (C) 2007 Hitachi Software Engineering Co., Ltd.
  *                     Yuichi Nakamura <ynakam@hitachisoft.jp>
  *
@@ -4325,6 +4325,59 @@ static void selinux_req_classify_flow(const struct request_sock *req,
         fl->secid = req->secid;
 }
 
+static int selinux_tun_dev_create(void)
+{
+        u32 sid = current_sid();
+
+        /* we aren't taking into account the "sockcreate" SID since the socket
+         * that is being created here is not a socket in the traditional sense,
+         * instead it is a private sock, accessible only to the kernel, and
+         * representing a wide range of network traffic spanning multiple
+         * connections unlike traditional sockets - check the TUN driver to
+         * get a better understanding of why this socket is special */
+
+        return avc_has_perm(sid, sid, SECCLASS_TUN_SOCKET, TUN_SOCKET__CREATE,
+                            NULL);
+}
+
+static void selinux_tun_dev_post_create(struct sock *sk)
+{
+        struct sk_security_struct *sksec = sk->sk_security;
+
+        /* we don't currently perform any NetLabel based labeling here and it
+         * isn't clear that we would want to do so anyway; while we could apply
+         * labeling without the support of the TUN user the resulting labeled
+         * traffic from the other end of the connection would almost certainly
+         * cause confusion to the TUN user that had no idea network labeling
+         * protocols were being used */
+
+        /* see the comments in selinux_tun_dev_create() about why we don't use
+         * the sockcreate SID here */
+
+        sksec->sid = current_sid();
+        sksec->sclass = SECCLASS_TUN_SOCKET;
+}
+
+static int selinux_tun_dev_attach(struct sock *sk)
+{
+        struct sk_security_struct *sksec = sk->sk_security;
+        u32 sid = current_sid();
+        int err;
+
+        err = avc_has_perm(sid, sksec->sid, SECCLASS_TUN_SOCKET,
+                           TUN_SOCKET__RELABELFROM, NULL);
+        if (err)
+                return err;
+        err = avc_has_perm(sid, sid, SECCLASS_TUN_SOCKET,
+                           TUN_SOCKET__RELABELTO, NULL);
+        if (err)
+                return err;
+
+        sksec->sid = sid;
+
+        return 0;
+}
+
 static int selinux_nlmsg_perm(struct sock *sk, struct sk_buff *skb)
 {
         int err = 0;
@@ -5494,6 +5547,9 @@ static struct security_operations selinux_ops = {
         .inet_csk_clone =               selinux_inet_csk_clone,
         .inet_conn_established =        selinux_inet_conn_established,
         .req_classify_flow =            selinux_req_classify_flow,
+        .tun_dev_create =               selinux_tun_dev_create,
+        .tun_dev_post_create =          selinux_tun_dev_post_create,
+        .tun_dev_attach =               selinux_tun_dev_attach,
 
 #ifdef CONFIG_SECURITY_NETWORK_XFRM
         .xfrm_policy_alloc_security =   selinux_xfrm_policy_alloc,