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>

diff --git a/include/linux/security.h b/include/linux/security.h
index 17e1888ff505c6fd35b08ce7a42d575fa6b553d3..0e99312e324f1adc522467604f92b2f2e214aa40 100644 (file)
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1313,6 +1313,13 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
  *     @pages contains the number of pages.
  *     Return 0 if permission is granted.
  *
+ * @ismaclabel:
+ *     Check if the extended attribute specified by @name
+ *     represents a MAC label. Returns 1 if name is a MAC
+ *     attribute otherwise returns 0.
+ *     @name full extended attribute name to check against
+ *     LSM as a MAC label.
+ *
  * @secid_to_secctx:
  *     Convert secid to security context.  If secdata is NULL the length of
  *     the result will be returned in seclen, but no secdata will be returned.
@@ -1595,6 +1602,7 @@ struct security_operations {
 
        int (*getprocattr) (struct task_struct *p, char *name, char **value);
        int (*setprocattr) (struct task_struct *p, char *name, void *value, size_t size);
+       int (*ismaclabel) (const char *name);
        int (*secid_to_secctx) (u32 secid, char **secdata, u32 *seclen);
        int (*secctx_to_secid) (const char *secdata, u32 seclen, u32 *secid);
        void (*release_secctx) (char *secdata, u32 seclen);
@@ -1849,6 +1857,7 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode);
 int security_getprocattr(struct task_struct *p, char *name, char **value);
 int security_setprocattr(struct task_struct *p, char *name, void *value, size_t size);
 int security_netlink_send(struct sock *sk, struct sk_buff *skb);
+int security_ismaclabel(const char *name);
 int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen);
 int security_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid);
 void security_release_secctx(char *secdata, u32 seclen);
@@ -2549,6 +2558,11 @@ static inline int security_netlink_send(struct sock *sk, struct sk_buff *skb)
        return cap_netlink_send(sk, skb);
 }
 
+static inline int security_ismaclabel(const char *name)
+{
+       return 0;
+}
+
 static inline int security_secid_to_secctx(u32 secid, char **secdata, u32 *seclen)
 {
        return -EOPNOTSUPP;

diff --git a/security/capability.c b/security/capability.c
index 6e4fc776badf16cf568adcd88386d1fcfeacb8aa..8758d6a46a9b769778f615735faf2f3923b502bc 100644 (file)
--- a/security/capability.c
+++ b/security/capability.c
@@ -836,6 +836,11 @@ 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;
@@ -1058,6 +1063,7 @@ 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 d6ab2d2b363dace7394b060a2a64646762dc0d1f..36e6b526264abb9f748034e0031330432d5e16ac 100644 (file)
--- a/security/security.c
+++ b/security/security.c
@@ -1067,6 +1067,12 @@ 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 a8de30bd733a5cc2d2043e234fbf0ba360d7282f..f46b1c39acfcfd0cdd8ca958f30ad4a799f1122e 100644 (file)
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -5505,6 +5505,11 @@ 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);
@@ -5747,6 +5752,7 @@ 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 6a083303501dd8cf702c26ea0af8df72e7b89650..3f7682a387b730b9c75fc6e547de98d512b46dbb 100644 (file)
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -3639,6 +3639,16 @@ 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
@@ -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,