[PATCH] selinux: add hooks for key subsystem

Introduce SELinux hooks to support the access key retention subsystem
within the kernel.  Incorporate new flask headers from a modified version
of the SELinux reference policy, with support for the new security class
representing retained keys.  Extend the "key_alloc" security hook with a
task parameter representing the intended ownership context for the key
being allocated.  Attach security information to root's default keyrings
within the SELinux initialization routine.

Has passed David's testsuite.

Signed-off-by: Michael LeMay <mdlemay@epoch.ncsc.mil>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
Acked-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

security/selinux/hooks.c

@@ -4252,6 +4252,57 @@ static int selinux_setprocattr(struct task_struct *p,
 	return size;
 }
 
+#ifdef CONFIG_KEYS
+
+static int selinux_key_alloc(struct key *k, struct task_struct *tsk)
+{
+	struct task_security_struct *tsec = tsk->security;
+	struct key_security_struct *ksec;
+
+	ksec = kzalloc(sizeof(struct key_security_struct), GFP_KERNEL);
+	if (!ksec)
+		return -ENOMEM;
+
+	ksec->obj = k;
+	ksec->sid = tsec->sid;
+	k->security = ksec;
+
+	return 0;
+}
+
+static void selinux_key_free(struct key *k)
+{
+	struct key_security_struct *ksec = k->security;
+
+	k->security = NULL;
+	kfree(ksec);
+}
+
+static int selinux_key_permission(key_ref_t key_ref,
+			    struct task_struct *ctx,
+			    key_perm_t perm)
+{
+	struct key *key;
+	struct task_security_struct *tsec;
+	struct key_security_struct *ksec;
+
+	key = key_ref_to_ptr(key_ref);
+
+	tsec = ctx->security;
+	ksec = key->security;
+
+	/* if no specific permissions are requested, we skip the
+	   permission check. No serious, additional covert channels
+	   appear to be created. */
+	if (perm == 0)
+		return 0;
+
+	return avc_has_perm(tsec->sid, ksec->sid,
+			    SECCLASS_KEY, perm, NULL);
+}
+
+#endif
+
 static struct security_operations selinux_ops = {
 	.ptrace =			selinux_ptrace,
 	.capget =			selinux_capget,
@@ -4406,6 +4457,12 @@ static struct security_operations selinux_ops = {
 	.xfrm_state_delete_security =	selinux_xfrm_state_delete,
 	.xfrm_policy_lookup = 		selinux_xfrm_policy_lookup,
 #endif
+
+#ifdef CONFIG_KEYS
+	.key_alloc =                    selinux_key_alloc,
+	.key_free =                     selinux_key_free,
+	.key_permission =               selinux_key_permission,
+#endif
 };
 
 static __init int selinux_init(void)
@@ -4441,6 +4498,13 @@ static __init int selinux_init(void)
 	} else {
 		printk(KERN_INFO "SELinux:  Starting in permissive mode\n");
 	}
+
+#ifdef CONFIG_KEYS
+	/* Add security information to initial keyrings */
+	security_key_alloc(&root_user_keyring, current);
+	security_key_alloc(&root_session_keyring, current);
+#endif
+
 	return 0;
 }
 

security/selinux/include/av_perm_to_string.h

@@ -242,3 +242,9 @@
    S_(SECCLASS_PACKET, PACKET__SEND, "send")
    S_(SECCLASS_PACKET, PACKET__RECV, "recv")
    S_(SECCLASS_PACKET, PACKET__RELABELTO, "relabelto")
+   S_(SECCLASS_KEY, KEY__VIEW, "view")
+   S_(SECCLASS_KEY, KEY__READ, "read")
+   S_(SECCLASS_KEY, KEY__WRITE, "write")
+   S_(SECCLASS_KEY, KEY__SEARCH, "search")
+   S_(SECCLASS_KEY, KEY__LINK, "link")
+   S_(SECCLASS_KEY, KEY__SETATTR, "setattr")

security/selinux/include/av_permissions.h

@@ -959,3 +959,11 @@
 #define PACKET__SEND                              0x00000001UL
 #define PACKET__RECV                              0x00000002UL
 #define PACKET__RELABELTO                         0x00000004UL
+
+#define KEY__VIEW                                 0x00000001UL
+#define KEY__READ                                 0x00000002UL
+#define KEY__WRITE                                0x00000004UL
+#define KEY__SEARCH                               0x00000008UL
+#define KEY__LINK                                 0x00000010UL
+#define KEY__SETATTR                              0x00000020UL
+

security/selinux/include/class_to_string.h

@@ -60,3 +60,4 @@
     S_("netlink_kobject_uevent_socket")
     S_("appletalk_socket")
     S_("packet")
+    S_("key")

security/selinux/include/flask.h

@@ -62,6 +62,7 @@
 #define SECCLASS_NETLINK_KOBJECT_UEVENT_SOCKET           55
 #define SECCLASS_APPLETALK_SOCKET                        56
 #define SECCLASS_PACKET                                  57
+#define SECCLASS_KEY                                     58
 
 /*
  * Security identifier indices for initial entities

security/selinux/include/objsec.h

@@ -99,6 +99,11 @@ struct sk_security_struct {
 	u32 peer_sid;			/* SID of peer */
 };
 
+struct key_security_struct {
+	struct key *obj; /* back pointer */
+	u32 sid;         /* SID of key */
+};
+
 extern unsigned int selinux_checkreqprot;
 
 #endif /* _SELINUX_OBJSEC_H_ */