[LSM-IPsec]: SELinux Authorize

This patch contains a fix for the previous patch that adds security
contexts to IPsec policies and security associations.  In the previous
patch, no authorization (besides the check for write permissions to
SAD and SPD) is required to delete IPsec policies and security
assocations with security contexts.  Thus a user authorized to change
SAD and SPD can bypass the IPsec policy authorization by simply
deleteing policies with security contexts.  To fix this security hole,
an additional authorization check is added for removing security
policies and security associations with security contexts.

Note that if no security context is supplied on add or present on
policy to be deleted, the SELinux module allows the change
unconditionally.  The hook is called on deletion when no context is
present, which we may want to change.  At present, I left it up to the
module.

LSM changes:

The patch adds two new LSM hooks: xfrm_policy_delete and
xfrm_state_delete.  The new hooks are necessary to authorize deletion
of IPsec policies that have security contexts.  The existing hooks
xfrm_policy_free and xfrm_state_free lack the context to do the
authorization, so I decided to split authorization of deletion and
memory management of security data, as is typical in the LSM
interface.

Use:

The new delete hooks are checked when xfrm_policy or xfrm_state are
deleted by either the xfrm_user interface (xfrm_get_policy,
xfrm_del_sa) or the pfkey interface (pfkey_spddelete, pfkey_delete).

SELinux changes:

The new policy_delete and state_delete functions are added.

Signed-off-by: Catherine Zhang <cxzhang@watson.ibm.com>
Signed-off-by: Trent Jaeger <tjaeger@cse.psu.edu>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 0 deletions

diff --git a/security/dummy.c b/security/dummy.c
index 8ccccccc12ac..64f6da0f422e 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -810,6 +810,11 @@ static void dummy_xfrm_policy_free_security(struct xfrm_policy *xp)
 {
 }
 
+static int dummy_xfrm_policy_delete_security(struct xfrm_policy *xp)
+{
+        return 0;
+}
+
 static int dummy_xfrm_state_alloc_security(struct xfrm_state *x, struct xfrm_user_sec_ctx *sec_ctx)
 {
         return 0;
@@ -819,6 +824,11 @@ static void dummy_xfrm_state_free_security(struct xfrm_state *x)
 {
 }
 
+static int dummy_xfrm_state_delete_security(struct xfrm_state *x)
+{
+        return 0;
+}
+
 static int dummy_xfrm_policy_lookup(struct xfrm_policy *xp, u32 sk_sid, u8 dir)
 {
         return 0;
@@ -1024,8 +1034,10 @@ void security_fixup_ops (struct security_operations *ops)
         set_to_dummy_if_null(ops, xfrm_policy_alloc_security);
         set_to_dummy_if_null(ops, xfrm_policy_clone_security);
         set_to_dummy_if_null(ops, xfrm_policy_free_security);
+        set_to_dummy_if_null(ops, xfrm_policy_delete_security);
         set_to_dummy_if_null(ops, xfrm_state_alloc_security);
         set_to_dummy_if_null(ops, xfrm_state_free_security);
+        set_to_dummy_if_null(ops, xfrm_state_delete_security);
         set_to_dummy_if_null(ops, xfrm_policy_lookup);
 #endif  /* CONFIG_SECURITY_NETWORK_XFRM */
 #ifdef CONFIG_KEYS