selinux: dynamic class/perm discovery

Modify SELinux to dynamically discover class and permission values
upon policy load, based on the dynamic object class/perm discovery
logic from libselinux.  A mapping is created between kernel-private
class and permission indices used outside the security server and the
policy values used within the security server.

The mappings are only applied upon kernel-internal computations;
similar mappings for the private indices of userspace object managers
is handled on a per-object manager basis by the userspace AVC.  The
interfaces for compute_av and transition_sid are split for kernel
vs. userspace; the userspace functions are distinguished by a _user
suffix.

The kernel-private class indices are no longer tied to the policy
values and thus do not need to skip indices for userspace classes;
thus the kernel class index values are compressed.  The flask.h
definitions were regenerated by deleting the userspace classes from
refpolicy's definitions and then regenerating the headers.  Going
forward, we can just maintain the flask.h, av_permissions.h, and
classmap.h definitions separately from policy as they are no longer
tied to the policy values.  The next patch introduces a utility to
automate generation of flask.h and av_permissions.h from the
classmap.h definitions.

The older kernel class and permission string tables are removed and
replaced by a single security class mapping table that is walked at
policy load to generate the mapping.  The old kernel class validation
logic is completely replaced by the mapping logic.

The handle unknown logic is reworked.  reject_unknown=1 is handled
when the mappings are computed at policy load time, similar to the old
handling by the class validation logic.  allow_unknown=1 is handled
when computing and mapping decisions - if the permission was not able
to be mapped (i.e. undefined, mapped to zero), then it is
automatically added to the allowed vector.  If the class was not able
to be mapped (i.e. undefined, mapped to zero), then all permissions
are allowed for it if allow_unknown=1.

avc_audit leverages the new security class mapping table to lookup the
class and permission names from the kernel-private indices.

The mdp program is updated to use the new table when generating the
class definitions and allow rules for a minimal boot policy for the
kernel.  It should be noted that this policy will not include any
userspace classes, nor will its policy index values for the kernel
classes correspond with the ones in refpolicy (they will instead match
the kernel-private indices).

Signed-off-by:  Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 45 insertions, 2 deletions

diff --git a/security/selinux/ss/policydb.c b/security/selinux/ss/policydb.c
index 72e4a54973aa..f03667213ea8 100644
--- a/security/selinux/ss/policydb.c
+++ b/security/selinux/ss/policydb.c
@@ -713,7 +713,6 @@ void policydb_destroy(struct policydb *p)
                         ebitmap_destroy(&p->type_attr_map[i]);
         }
         kfree(p->type_attr_map);
-        kfree(p->undefined_perms);
         ebitmap_destroy(&p->policycaps);
         ebitmap_destroy(&p->permissive_map);
 
@@ -1640,6 +1639,40 @@ static int policydb_bounds_sanity_check(struct policydb *p)
 
 extern int ss_initialized;
 
+u16 string_to_security_class(struct policydb *p, const char *name)
+{
+        struct class_datum *cladatum;
+
+        cladatum = hashtab_search(p->p_classes.table, name);
+        if (!cladatum)
+                return 0;
+
+        return cladatum->value;
+}
+
+u32 string_to_av_perm(struct policydb *p, u16 tclass, const char *name)
+{
+        struct class_datum *cladatum;
+        struct perm_datum *perdatum = NULL;
+        struct common_datum *comdatum;
+
+        if (!tclass || tclass > p->p_classes.nprim)
+                return 0;
+
+        cladatum = p->class_val_to_struct[tclass-1];
+        comdatum = cladatum->comdatum;
+        if (comdatum)
+                perdatum = hashtab_search(comdatum->permissions.table,
+                                          name);
+        if (!perdatum)
+                perdatum = hashtab_search(cladatum->permissions.table,
+                                          name);
+        if (!perdatum)
+                return 0;
+
+        return 1U << (perdatum->value-1);
+}
+
 /*
  * Read the configuration data from a policy database binary
  * representation file into a policy database structure.
@@ -1861,6 +1894,16 @@ int policydb_read(struct policydb *p, void *fp)
         if (rc)
                 goto bad;
 
+        p->process_class = string_to_security_class(p, "process");
+        if (!p->process_class)
+                goto bad;
+        p->process_trans_perms = string_to_av_perm(p, p->process_class,
+                                                   "transition");
+        p->process_trans_perms |= string_to_av_perm(p, p->process_class,
+                                                    "dyntransition");
+        if (!p->process_trans_perms)
+                goto bad;
+
         for (i = 0; i < info->ocon_num; i++) {
                 rc = next_entry(buf, fp, sizeof(u32));
                 if (rc < 0)
@@ -2101,7 +2144,7 @@ int policydb_read(struct policydb *p, void *fp)
                                         goto bad;
                                 rt->target_class = le32_to_cpu(buf[0]);
                         } else
-                                rt->target_class = SECCLASS_PROCESS;
+                                rt->target_class = p->process_class;
                         if (!policydb_type_isvalid(p, rt->source_type) ||
                             !policydb_type_isvalid(p, rt->target_type) ||
                             !policydb_class_isvalid(p, rt->target_class)) {