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selinux: dynamic class/perm discovery
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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 <[email protected]>
Signed-off-by: James Morris <[email protected]>
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stephensmalley authored and James Morris committed Oct 7, 2009
1 parent 23acb98 commit c6d3aaa
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Showing 16 changed files with 583 additions and 867 deletions.
151 changes: 28 additions & 123 deletions scripts/selinux/mdp/mdp.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -29,86 +29,27 @@
#include <unistd.h>
#include <string.h>

#include "flask.h"

static void usage(char *name)
{
printf("usage: %s [-m] policy_file context_file\n", name);
exit(1);
}

static void find_common_name(char *cname, char *dest, int len)
{
char *start, *end;

start = strchr(cname, '_')+1;
end = strchr(start, '_');
if (!start || !end || start-cname > len || end-start > len) {
printf("Error with commons defines\n");
exit(1);
}
strncpy(dest, start, end-start);
dest[end-start] = '\0';
}

#define S_(x) x,
static char *classlist[] = {
#include "class_to_string.h"
NULL
/* Class/perm mapping support */
struct security_class_mapping {
const char *name;
const char *perms[sizeof(unsigned) * 8 + 1];
};
#undef S_

#include "classmap.h"
#include "initial_sid_to_string.h"

#define TB_(x) char *x[] = {
#define TE_(x) NULL };
#define S_(x) x,
#include "common_perm_to_string.h"
#undef TB_
#undef TE_
#undef S_

struct common {
char *cname;
char **perms;
};
struct common common[] = {
#define TB_(x) { #x, x },
#define S_(x)
#define TE_(x)
#include "common_perm_to_string.h"
#undef TB_
#undef TE_
#undef S_
};

#define S_(x, y, z) {x, #y},
struct av_inherit {
int class;
char *common;
};
struct av_inherit av_inherit[] = {
#include "av_inherit.h"
};
#undef S_

#include "av_permissions.h"
#define S_(x, y, z) {x, y, z},
struct av_perms {
int class;
int perm_i;
char *perm_s;
};
struct av_perms av_perms[] = {
#include "av_perm_to_string.h"
};
#undef S_

int main(int argc, char *argv[])
{
int i, j, mls = 0;
int initial_sid_to_string_len;
char **arg, *polout, *ctxout;
int classlist_len, initial_sid_to_string_len;

FILE *fout;

if (argc < 3)
Expand All @@ -127,64 +68,25 @@ int main(int argc, char *argv[])
usage(argv[0]);
}

classlist_len = sizeof(classlist) / sizeof(char *);
/* print out the classes */
for (i=1; i < classlist_len; i++) {
if(classlist[i])
fprintf(fout, "class %s\n", classlist[i]);
else
fprintf(fout, "class user%d\n", i);
}
for (i = 0; secclass_map[i].name; i++)
fprintf(fout, "class %s\n", secclass_map[i].name);
fprintf(fout, "\n");

initial_sid_to_string_len = sizeof(initial_sid_to_string) / sizeof (char *);
/* print out the sids */
for (i=1; i < initial_sid_to_string_len; i++)
for (i = 1; i < initial_sid_to_string_len; i++)
fprintf(fout, "sid %s\n", initial_sid_to_string[i]);
fprintf(fout, "\n");

/* print out the commons */
for (i=0; i< sizeof(common)/sizeof(struct common); i++) {
char cname[101];
find_common_name(common[i].cname, cname, 100);
cname[100] = '\0';
fprintf(fout, "common %s\n{\n", cname);
for (j=0; common[i].perms[j]; j++)
fprintf(fout, "\t%s\n", common[i].perms[j]);
fprintf(fout, "}\n\n");
}
fprintf(fout, "\n");

/* print out the class permissions */
for (i=1; i < classlist_len; i++) {
if (classlist[i]) {
int firstperm = -1, numperms = 0;

fprintf(fout, "class %s\n", classlist[i]);
/* does it inherit from a common? */
for (j=0; j < sizeof(av_inherit)/sizeof(struct av_inherit); j++)
if (av_inherit[j].class == i)
fprintf(fout, "inherits %s\n", av_inherit[j].common);

for (j=0; j < sizeof(av_perms)/sizeof(struct av_perms); j++) {
if (av_perms[j].class == i) {
if (firstperm == -1)
firstperm = j;
numperms++;
}
}
if (!numperms) {
fprintf(fout, "\n");
continue;
}

fprintf(fout, "{\n");
/* print out the av_perms */
for (j=0; j < numperms; j++) {
fprintf(fout, "\t%s\n", av_perms[firstperm+j].perm_s);
}
fprintf(fout, "}\n\n");
}
for (i = 0; secclass_map[i].name; i++) {
struct security_class_mapping *map = &secclass_map[i];
fprintf(fout, "class %s\n", map->name);
fprintf(fout, "{\n");
for (j = 0; map->perms[j]; j++)
fprintf(fout, "\t%s\n", map->perms[j]);
fprintf(fout, "}\n\n");
}
fprintf(fout, "\n");

Expand All @@ -197,31 +99,34 @@ int main(int argc, char *argv[])
/* types, roles, and allows */
fprintf(fout, "type base_t;\n");
fprintf(fout, "role base_r types { base_t };\n");
for (i=1; i < classlist_len; i++) {
if (classlist[i])
fprintf(fout, "allow base_t base_t:%s *;\n", classlist[i]);
else
fprintf(fout, "allow base_t base_t:user%d *;\n", i);
}
for (i = 0; secclass_map[i].name; i++)
fprintf(fout, "allow base_t base_t:%s *;\n",
secclass_map[i].name);
fprintf(fout, "user user_u roles { base_r };\n");
fprintf(fout, "\n");

/* default sids */
for (i=1; i < initial_sid_to_string_len; i++)
for (i = 1; i < initial_sid_to_string_len; i++)
fprintf(fout, "sid %s user_u:base_r:base_t\n", initial_sid_to_string[i]);
fprintf(fout, "\n");


fprintf(fout, "fs_use_xattr ext2 user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_xattr ext3 user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_xattr ext4 user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_xattr jfs user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_xattr xfs user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_xattr reiserfs user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_xattr jffs2 user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_xattr gfs2 user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_xattr lustre user_u:base_r:base_t;\n");

fprintf(fout, "fs_use_task eventpollfs user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_task pipefs user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_task sockfs user_u:base_r:base_t;\n");

fprintf(fout, "fs_use_trans mqueue user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_trans devpts user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_trans hugetlbfs user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_trans tmpfs user_u:base_r:base_t;\n");
fprintf(fout, "fs_use_trans shm user_u:base_r:base_t;\n");

Expand Down
76 changes: 8 additions & 68 deletions security/selinux/avc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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);

Expand Down Expand Up @@ -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);
}

/**
Expand Down
34 changes: 0 additions & 34 deletions security/selinux/include/av_inherit.h
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