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, 8 insertions, 68 deletions

diff --git a/security/selinux/avc.c b/security/selinux/avc.c
index b4b5da1c0a42..18f4103e02b7 100644
--- a/security/selinux/avc.c
+++ b/security/selinux/avc.c
@@ -31,43 +31,7 @@
 #include <net/ipv6.h>
 #include "avc.h"
 #include "avc_ss.h"
-
-static const struct av_perm_to_string av_perm_to_string[] = {
-#define S_(c, v, s) { c, v, s },
-#include "av_perm_to_string.h"
-#undef S_
-};
-
-static const char *class_to_string[] = {
-#define S_(s) s,
-#include "class_to_string.h"
-#undef S_
-};
-
-#define TB_(s) static const char *s[] = {
-#define TE_(s) };
-#define S_(s) s,
-#include "common_perm_to_string.h"
-#undef TB_
-#undef TE_
-#undef S_
-
-static const struct av_inherit av_inherit[] = {
-#define S_(c, i, b) {   .tclass = c,\
-                        .common_pts = common_##i##_perm_to_string,\
-                        .common_base =  b },
-#include "av_inherit.h"
-#undef S_
-};
-
-const struct selinux_class_perm selinux_class_perm = {
-        .av_perm_to_string = av_perm_to_string,
-        .av_pts_len = ARRAY_SIZE(av_perm_to_string),
-        .class_to_string = class_to_string,
-        .cts_len = ARRAY_SIZE(class_to_string),
-        .av_inherit = av_inherit,
-        .av_inherit_len = ARRAY_SIZE(av_inherit)
-};
+#include "classmap.h"
 
 #define AVC_CACHE_SLOTS                 512
 #define AVC_DEF_CACHE_THRESHOLD         512
@@ -139,52 +103,28 @@ static inline int avc_hash(u32 ssid, u32 tsid, u16 tclass)
  */
 static void avc_dump_av(struct audit_buffer *ab, u16 tclass, u32 av)
 {
-        const char **common_pts = NULL;
-        u32 common_base = 0;
-        int i, i2, perm;
+        const char **perms;
+        int i, perm;
 
         if (av == 0) {
                 audit_log_format(ab, " null");
                 return;
         }
 
-        for (i = 0; i < ARRAY_SIZE(av_inherit); i++) {
-                if (av_inherit[i].tclass == tclass) {
-                        common_pts = av_inherit[i].common_pts;
-                        common_base = av_inherit[i].common_base;
-                        break;
-                }
-        }
+        perms = secclass_map[tclass-1].perms;
 
         audit_log_format(ab, " {");
         i = 0;
         perm = 1;
-        while (perm < common_base) {
+        while (i < (sizeof(av) * 8)) {
                 if (perm & av) {
-                        audit_log_format(ab, " %s", common_pts[i]);
+                        audit_log_format(ab, " %s", perms[i]);
                         av &= ~perm;
                 }
                 i++;
                 perm <<= 1;
         }
 
-        while (i < sizeof(av) * 8) {
-                if (perm & av) {
-                        for (i2 = 0; i2 < ARRAY_SIZE(av_perm_to_string); i2++) {
-                                if ((av_perm_to_string[i2].tclass == tclass) &&
-                                    (av_perm_to_string[i2].value == perm))
-                                        break;
-                        }
-                        if (i2 < ARRAY_SIZE(av_perm_to_string)) {
-                                audit_log_format(ab, " %s",
-                                                 av_perm_to_string[i2].name);
-                                av &= ~perm;
-                        }
-                }
-                i++;
-                perm <<= 1;
-        }
-
         if (av)
                 audit_log_format(ab, " 0x%x", av);
 
@@ -219,8 +159,8 @@ static void avc_dump_query(struct audit_buffer *ab, u32 ssid, u32 tsid, u16 tcla
                 kfree(scontext);
         }
 
-        BUG_ON(tclass >= ARRAY_SIZE(class_to_string) || !class_to_string[tclass]);
-        audit_log_format(ab, " tclass=%s", class_to_string[tclass]);
+        BUG_ON(tclass >= ARRAY_SIZE(secclass_map));
+        audit_log_format(ab, " tclass=%s", secclass_map[tclass-1].name);
 }
 
 /**