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/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,