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Commit 031dcc8f authored by John Johansen's avatar John Johansen
Browse files

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: default avatarJohn Johansen <john.johansen@canonical.com>
parent 074c1cd7

security/apparmor/include/match.h

+4 −0
Original line number Diff line number Diff line
@@ -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 */

security/apparmor/match.c

+25 −1
Original line number Diff line number Diff line
@@ -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];				\