selinux: introduce permissive types

Introduce the concept of a permissive type.  A new ebitmap is introduced to
the policy database which indicates if a given type has the permissive bit
set or not.  This bit is tested for the scontext of any denial.  The bit is
meaningless on types which only appear as the target of a decision and never
the source.  A domain running with a permissive type will be allowed to
perform any action similarly to when the system is globally set permissive.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

security/selinux/Kconfig

@@ -145,7 +145,7 @@ config SECURITY_SELINUX_POLICYDB_VERSION_MAX
 config SECURITY_SELINUX_POLICYDB_VERSION_MAX_VALUE
 	int "NSA SELinux maximum supported policy format version value"
 	depends on SECURITY_SELINUX_POLICYDB_VERSION_MAX
-	range 15 22
+	range 15 23
 	default 19
 	help
 	  This option sets the value for the maximum policy format version

security/selinux/avc.c

@@ -893,12 +893,13 @@ int avc_has_perm_noaudit(u32 ssid, u32 tsid,
 	denied = requested & ~(p_ae->avd.allowed);
 
 	if (denied) {
-		if (selinux_enforcing || (flags & AVC_STRICT))
+		if (flags & AVC_STRICT)
 			rc = -EACCES;
+		else if (!selinux_enforcing || security_permissive_sid(ssid))
+			avc_update_node(AVC_CALLBACK_GRANT, requested, ssid,
+					tsid, tclass);
 		else
-			if (node)
-				avc_update_node(AVC_CALLBACK_GRANT,requested,
-						ssid,tsid,tclass);
+			rc = -EACCES;
 	}
 
 	rcu_read_unlock();

security/selinux/include/security.h

@@ -26,13 +26,14 @@
 #define POLICYDB_VERSION_AVTAB		20
 #define POLICYDB_VERSION_RANGETRANS	21
 #define POLICYDB_VERSION_POLCAP		22
+#define POLICYDB_VERSION_PERMISSIVE	23
 
 /* Range of policy versions we understand*/
 #define POLICYDB_VERSION_MIN   POLICYDB_VERSION_BASE
 #ifdef CONFIG_SECURITY_SELINUX_POLICYDB_VERSION_MAX
 #define POLICYDB_VERSION_MAX	CONFIG_SECURITY_SELINUX_POLICYDB_VERSION_MAX_VALUE
 #else
-#define POLICYDB_VERSION_MAX	POLICYDB_VERSION_POLCAP
+#define POLICYDB_VERSION_MAX	POLICYDB_VERSION_PERMISSIVE
 #endif
 
 #define CONTEXT_MNT	0x01
@@ -69,6 +70,8 @@ struct av_decision {
 	u32 seqno;
 };
 
+int security_permissive_sid(u32 sid);
+
 int security_compute_av(u32 ssid, u32 tsid,
 	u16 tclass, u32 requested,
 	struct av_decision *avd);

security/selinux/ss/policydb.c

@@ -111,6 +111,11 @@ static struct policydb_compat_info policydb_compat[] = {
 		.version	= POLICYDB_VERSION_POLCAP,
 		.sym_num	= SYM_NUM,
 		.ocon_num	= OCON_NUM,
+	},
+	{
+		.version	= POLICYDB_VERSION_PERMISSIVE,
+		.sym_num	= SYM_NUM,
+		.ocon_num	= OCON_NUM,
 	}
 };
 
@@ -194,6 +199,7 @@ static int policydb_init(struct policydb *p)
 		goto out_free_symtab;
 
 	ebitmap_init(&p->policycaps);
+	ebitmap_init(&p->permissive_map);
 
 out:
 	return rc;
@@ -687,6 +693,7 @@ void policydb_destroy(struct policydb *p)
 	kfree(p->type_attr_map);
 	kfree(p->undefined_perms);
 	ebitmap_destroy(&p->policycaps);
+	ebitmap_destroy(&p->permissive_map);
 
 	return;
 }
@@ -1570,6 +1577,10 @@ int policydb_read(struct policydb *p, void *fp)
 	    ebitmap_read(&p->policycaps, fp) != 0)
 		goto bad;
 
+	if (p->policyvers >= POLICYDB_VERSION_PERMISSIVE &&
+	    ebitmap_read(&p->permissive_map, fp) != 0)
+		goto bad;
+
 	info = policydb_lookup_compat(p->policyvers);
 	if (!info) {
 		printk(KERN_ERR "SELinux:  unable to find policy compat info "

security/selinux/ss/policydb.h

@@ -243,6 +243,8 @@ struct policydb {
 
 	struct ebitmap policycaps;
 
+	struct ebitmap permissive_map;
+
 	unsigned int policyvers;
 
 	unsigned int reject_unknown : 1;

security/selinux/ss/services.c

@@ -417,6 +417,31 @@ inval_class:
 	return -EINVAL;
 }
 
+/*
+ * Given a sid find if the type has the permissive flag set
+ */
+int security_permissive_sid(u32 sid)
+{
+	struct context *context;
+	u32 type;
+	int rc;
+
+	POLICY_RDLOCK;
+
+	context = sidtab_search(&sidtab, sid);
+	BUG_ON(!context);
+
+	type = context->type;
+	/*
+	 * we are intentionally using type here, not type-1, the 0th bit may
+	 * someday indicate that we are globally setting permissive in policy.
+	 */
+	rc = ebitmap_get_bit(&policydb.permissive_map, type);
+
+	POLICY_RDUNLOCK;
+	return rc;
+}
+
 static int security_validtrans_handle_fail(struct context *ocontext,
                                            struct context *ncontext,
                                            struct context *tcontext,