Commit d901d6a2 authored by John Johansen's avatar John Johansen
Browse files

apparmor: dfa split verification of table headers 



separate the different types of verification so they are logically
separate and can be reused separate of each other.

Signed-off-by: default avatarJohn Johansen <john.johansen@canonical.com>
parent 031dcc8f

security/apparmor/match.c

+68 −48
Original line number Diff line number Diff line
@@ -136,8 +136,8 @@ static struct table_header *unpack_table(char *blob, size_t bsize) 
}



/**

 * verify_dfa - verify that transitions and states in the tables are in bounds.

 * @dfa: dfa to test  (NOT NULL)

 * verify_table_headers - verify that the tables headers are as expected

 * @tables - array of dfa tables to check (NOT NULL)

 * @flags: flags controlling what type of accept table are acceptable

 *

 * Assumes dfa has gone through the first pass verification done by unpacking
@@ -145,52 +145,69 @@ static struct table_header *unpack_table(char *blob, size_t bsize) 
 *

 * Returns: %0 else error code on failure to verify

 */

static int verify_dfa(struct aa_dfa *dfa, int flags)

static int verify_table_headers(struct table_header **tables, int flags)

{

	size_t i, state_count, trans_count;

	size_t state_count, trans_count;

	int error = -EPROTO;



	/* check that required tables exist */

	if (!(dfa->tables[YYTD_ID_DEF] &&

	      dfa->tables[YYTD_ID_BASE] &&

	      dfa->tables[YYTD_ID_NXT] && dfa->tables[YYTD_ID_CHK]))

	if (!(tables[YYTD_ID_DEF] && tables[YYTD_ID_BASE] &&

	      tables[YYTD_ID_NXT] && tables[YYTD_ID_CHK]))

		goto out;



	/* accept.size == default.size == base.size */

	state_count = dfa->tables[YYTD_ID_BASE]->td_lolen;

	state_count = tables[YYTD_ID_BASE]->td_lolen;

	if (ACCEPT1_FLAGS(flags)) {

		if (!dfa->tables[YYTD_ID_ACCEPT])

		if (!tables[YYTD_ID_ACCEPT])

			goto out;

		if (state_count != dfa->tables[YYTD_ID_ACCEPT]->td_lolen)

		if (state_count != tables[YYTD_ID_ACCEPT]->td_lolen)

			goto out;

	}

	if (ACCEPT2_FLAGS(flags)) {

		if (!dfa->tables[YYTD_ID_ACCEPT2])

		if (!tables[YYTD_ID_ACCEPT2])

			goto out;

		if (state_count != dfa->tables[YYTD_ID_ACCEPT2]->td_lolen)

		if (state_count != tables[YYTD_ID_ACCEPT2]->td_lolen)

			goto out;

	}

	if (state_count != dfa->tables[YYTD_ID_DEF]->td_lolen)

	if (state_count != tables[YYTD_ID_DEF]->td_lolen)

		goto out;



	/* next.size == chk.size */

	trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen;

	if (trans_count != dfa->tables[YYTD_ID_CHK]->td_lolen)

	trans_count = tables[YYTD_ID_NXT]->td_lolen;

	if (trans_count != tables[YYTD_ID_CHK]->td_lolen)

		goto out;



	/* if equivalence classes then its table size must be 256 */

	if (dfa->tables[YYTD_ID_EC] &&

	    dfa->tables[YYTD_ID_EC]->td_lolen != 256)

	if (tables[YYTD_ID_EC] && tables[YYTD_ID_EC]->td_lolen != 256)

		goto out;



	if (flags & DFA_FLAG_VERIFY_STATES) {

	error = 0;

out:

	return error;

}



/**

 * verify_dfa - verify that transitions and states in the tables are in bounds.

 * @dfa: dfa to test  (NOT NULL)

 *

 * Assumes dfa has gone through the first pass verification done by unpacking

 * NOTE: this does not valid accept table values

 *

 * Returns: %0 else error code on failure to verify

 */

static int verify_dfa(struct aa_dfa *dfa)

{

	size_t i, state_count, trans_count;

	int error = EPROTO;



	state_count = dfa->tables[YYTD_ID_BASE]->td_lolen;

	trans_count = dfa->tables[YYTD_ID_NXT]->td_lolen;

	for (i = 0; i < state_count; i++) {

		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 "

				       "bounds error\n");

			pr_err("AppArmor DFA next/check upper bounds error\n");

			goto out;

		}

	}
@@ -201,13 +218,11 @@ static int verify_dfa(struct aa_dfa *dfa, int flags) 
		if (CHECK_TABLE(dfa)[i] >= state_count)

			goto out;

	}

	}



	/* Now that all the other tables are verified, verify diffencoding */

	if (flags & DFA_FLAG_VERIFY_STATES) {

	for (i = 0; i < state_count; i++) {

		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);
@@ -220,8 +235,8 @@ static int verify_dfa(struct aa_dfa *dfa, int flags) 
			BASE_TABLE(dfa)[j] |= MARK_DIFF_ENCODE;

		}

	}

	}

	error = 0;



out:

	return error;

}
@@ -338,10 +353,15 @@ struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags) 
		size -= table_size(table->td_lolen, table->td_flags);

		table = NULL;

	}

	error = verify_table_headers(dfa->tables, flags);

	if (error)

		goto fail;



	error = verify_dfa(dfa, flags);

	if (flags & DFA_FLAG_VERIFY_STATES) {

		error = verify_dfa(dfa);

		if (error)

			goto fail;

	}



	return dfa;