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apparmor: dfa add support for state differential encoding 

State differential encoding can provide better compression for
apparmor policy, without having significant impact on match time.

Signed-off-by: John Johansen <john.johansen@canonical.com>
This commit is contained in:
John Johansen 2017-08-08 12:10:50 -07:00
parent 074c1cd798
commit 031dcc8f4e
2 changed files with 29 additions and 1 deletions
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4
security/apparmor/include/match.h
View File

@ -40,6 +40,7 @@
*/
#define YYTH_MAGIC 0x1B5E783D
#define YYTH_FLAG_DIFF_ENCODE 1
struct table_set_header {
u32 th_magic; /* YYTH_MAGIC */
@ -164,4 +165,7 @@ static inline void aa_put_dfa(struct aa_dfa *dfa)
kref_put(&dfa->count, aa_dfa_free_kref);
}
#define MATCH_FLAG_DIFF_ENCODE 0x80000000
#define MARK_DIFF_ENCODE 0x40000000
#endif /* __AA_MATCH_H */

26
security/apparmor/match.c
View File

@ -185,7 +185,8 @@ static int verify_dfa(struct aa_dfa *dfa, int flags)
if (flags & DFA_FLAG_VERIFY_STATES) {
for (i = 0; i < state_count; i++) {
if (DEFAULT_TABLE(dfa)[i] >= state_count)
if (!(BASE_TABLE(dfa)[i] & MATCH_FLAG_DIFF_ENCODE) &&
(DEFAULT_TABLE(dfa)[i] >= state_count))
goto out;
if (base_idx(BASE_TABLE(dfa)[i]) + 255 >= trans_count) {
printk(KERN_ERR "AppArmor DFA next/check upper "
@ -202,6 +203,24 @@ static int verify_dfa(struct aa_dfa *dfa, int flags)
}
}
/* Now that all the other tables are verified, verify diffencoding */
if (flags & DFA_FLAG_VERIFY_STATES) {
size_t j, k;
for (i = 0; i < state_count; i++) {
for (j = i;
(BASE_TABLE(dfa)[j] & MATCH_FLAG_DIFF_ENCODE) &&
!(BASE_TABLE(dfa)[j] & MARK_DIFF_ENCODE);
j = k) {
k = DEFAULT_TABLE(dfa)[j];
if (j == k)
goto out;
if (k < j)
break; /* already verified */
BASE_TABLE(dfa)[j] |= MARK_DIFF_ENCODE;
}
}
}
error = 0;
out:
return error;
@ -274,6 +293,9 @@ struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags)
goto fail;
dfa->flags = ntohs(*(__be16 *) (data + 12));
if (dfa->flags != 0 && dfa->flags != YYTH_FLAG_DIFF_ENCODE)
goto fail;
data += hsize;
size -= hsize;
@ -335,6 +357,8 @@ do { \
unsigned int pos = base_idx(b) + (C); \
if ((check)[pos] != (state)) { \
(state) = (def)[(state)]; \
if (b & MATCH_FLAG_DIFF_ENCODE) \
continue; \
break; \
} \
(state) = (next)[pos]; \