Security: Add Hook to test if the particular xattr is part of a MAC model.

The interface to request security labels from user space is the xattr
interface. When requesting the security label from an NFS server it is
important to make sure the requested xattr actually is a MAC label. This allows
us to make sure that we get the desired semantics from the attribute instead of
something else such as capabilities or a time based LSM.

Change-Id: I283f116953f958877826ba772661b5755986ac99
Acked-by: Eric Paris <eparis@redhat.com>
Acked-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Matthew N. Dodd <Matthew.Dodd@sparta.com>
Signed-off-by: Miguel Rodel Felipe <Rodel_FM@dsi.a-star.edu.sg>
Signed-off-by: Phua Eu Gene <PHUA_Eu_Gene@dsi.a-star.edu.sg>
Signed-off-by: Khin Mi Mi Aung <Mi_Mi_AUNG@dsi.a-star.edu.sg>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>

4 files changed, 29 insertions, 0 deletions

diff --git a/security/capability.c b/security/capability.c
index 1728d4e375d..26e0d3da8fd 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -816,6 +816,11 @@ static int cap_setprocattr(struct task_struct *p, char *name, void *value,
 	return -EINVAL;
 }
 
+static int cap_ismaclabel(const char *name)
+{
+	return 0;
+}
+
 static int cap_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 {
 	return -EOPNOTSUPP;
@@ -1034,6 +1039,7 @@ void __init security_fixup_ops(struct security_operations *ops)
 	set_to_cap_if_null(ops, d_instantiate);
 	set_to_cap_if_null(ops, getprocattr);
 	set_to_cap_if_null(ops, setprocattr);
+	set_to_cap_if_null(ops, ismaclabel);
 	set_to_cap_if_null(ops, secid_to_secctx);
 	set_to_cap_if_null(ops, secctx_to_secid);
 	set_to_cap_if_null(ops, release_secctx);
diff --git a/security/security.c b/security/security.c
index a3dce87d1ae..bf919ce7982 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1047,6 +1047,12 @@ int security_netlink_send(struct sock *sk, struct sk_buff *skb)
 	return security_ops->netlink_send(sk, skb);
 }
 
+int security_ismaclabel(const char *name)
+{
+	return security_ops->ismaclabel(name);
+}
+EXPORT_SYMBOL(security_ismaclabel);
+
 int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 {
 	return security_ops->secid_to_secctx(secid, secdata, seclen);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index fdd6e4f8be3..26a201e5125 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5544,6 +5544,11 @@ abort_change:
 	return error;
 }
 
+static int selinux_ismaclabel(const char *name)
+{
+	return (strcmp(name, XATTR_SELINUX_SUFFIX) == 0);
+}
+
 static int selinux_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 {
 	return security_sid_to_context(secid, secdata, seclen);
@@ -5781,6 +5786,7 @@ static struct security_operations selinux_ops = {
 	.getprocattr =			selinux_getprocattr,
 	.setprocattr =			selinux_setprocattr,
 
+	.ismaclabel =			selinux_ismaclabel,
 	.secid_to_secctx =		selinux_secid_to_secctx,
 	.secctx_to_secid =		selinux_secctx_to_secid,
 	.release_secctx =		selinux_release_secctx,
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 6a083303501..3f7682a387b 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -3640,6 +3640,16 @@ static void smack_audit_rule_free(void *vrule)
 #endif /* CONFIG_AUDIT */
 
 /**
+ * smack_ismaclabel - check if xattr @name references a smack MAC label
+ * @name: Full xattr name to check.
+ */
+static int smack_ismaclabel(const char *name)
+{
+	return (strcmp(name, XATTR_SMACK_SUFFIX) == 0);
+}
+
+
+/**
  * smack_secid_to_secctx - return the smack label for a secid
  * @secid: incoming integer
  * @secdata: destination
@@ -3836,6 +3846,7 @@ struct security_operations smack_ops = {
 	.audit_rule_free =		smack_audit_rule_free,
 #endif /* CONFIG_AUDIT */
 
+	.ismaclabel =			smack_ismaclabel,
 	.secid_to_secctx = 		smack_secid_to_secctx,
 	.secctx_to_secid = 		smack_secctx_to_secid,
 	.release_secctx = 		smack_release_secctx,