/*
* AppArmor security module
*
* This file contains AppArmor dfa based regular expression matching engine
*
* Copyright (C) 1998-2008 Novell/SUSE
* Copyright 2009-2010 Canonical Ltd.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation, version 2 of the
* License.
*/
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/err.h>
#include <linux/kref.h>
#include "include/apparmor.h"
#include "include/match.h"
/**
* unpack_table - unpack a dfa table (one of accept, default, base, next check)
* @blob: data to unpack (NOT NULL)
* @bsize: size of blob
*
* Returns: pointer to table else NULL on failure
*
* NOTE: must be freed by kvfree (not kmalloc)
*/
static struct table_header *unpack_table(char *blob, size_t bsize)
{
struct table_header *table = NULL;
struct table_header th;
size_t tsize;
if (bsize < sizeof(struct table_header))
goto out;
/* loaded td_id's start at 1, subtract 1 now to avoid doing
* it every time we use td_id as an index
*/
th.td_id = be16_to_cpu(*(u16 *) (blob)) - 1;
th.td_flags = be16_to_cpu(*(u16 *) (blob + 2));
th.td_lolen = be32_to_cpu(*(u32 *) (blob + 8));
blob += sizeof(struct table_header);
if (!(th.td_flags == YYTD_DATA16 || th.td_flags == YYTD_DATA32 ||
th.td_flags == YYTD_DATA8))
goto out;
tsize = table_size(th.td_lolen, th.td_flags);
if (bsize < tsize)
goto out;
table = kvmalloc(tsize);
if (table) {
*table = th;
if (th.td_flags == YYTD_DATA8)
UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
u8, byte_to_byte);
else if (th.td_flags == YYTD_DATA16)
UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
u16, be16_to_cpu);
else if (th.td_flags == YYTD_DATA32)
UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
u32, be32_to_cpu);
else
goto fail;
}
out:
/* if table was vmalloced make sure the page tables are synced
* before it is used, as it goes live to all cpus.
*/
if (is_vmalloc_addr(table))
vm_unmap_aliases();
return table;
fail:
kvfree(table);
return NULL;
}
/**
* verify_dfa - verify that transitions and states in the tables are in bounds.
* @dfa: dfa to test (NOT NULL)
* @flags: flags controlling what type of accept table are acceptable
*
* 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, int flags)
{
size_t i, 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]))
goto out;
/* accept.size == default.size == base.size */
state_count = dfa->tables[YYTD_ID_BASE]->td_lolen;
if (ACCEPT1_FLAGS(flags)) {
if (!dfa->tables[YYTD_ID_ACCEPT])
goto out;
if (state_count != dfa->tables[YYTD_ID_ACCEPT]->td_lolen)
goto out;
}
if (ACCEPT2_FLAGS(flags)) {
if (!dfa->tables[YYTD_ID_ACCEPT2])
goto out;
if (state_count != dfa->tables[YYTD_ID_ACCEPT2]->td_lolen)
goto out;
}
if (state_count != dfa->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)
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)
goto out;
if (flags & DFA_FLAG_VERIFY_STATES) {
for (i = 0; i < state_count; i++) {
if (DEFAULT_TABLE(dfa)[i] >= state_count)
goto out;
/* TODO: do check that DEF state recursion terminates */
if (BASE_TABLE(dfa)[i] + 255 >= trans_count) {
printk(KERN_ERR "AppArmor DFA next/check upper "
"bounds error\n");
goto out;
}
}
for (i = 0; i < trans_count; i++) {
if (NEXT_TABLE(dfa)[i] >= state_count)
goto out;
if (CHECK_TABLE(dfa)[i] >= state_count)
goto out;
}
}
error = 0;
out:
return error;
}
/**
* dfa_free - free a dfa allocated by aa_dfa_unpack
* @dfa: the dfa to free (MAYBE NULL)
*
* Requires: reference count to dfa == 0
*/
static void dfa_free(struct aa_dfa *dfa)
{
if (dfa) {
int i;
for (i = 0; i < ARRAY_SIZE(dfa->tables); i++) {
kvfree(dfa->tables[i]);
dfa->tables[i] = NULL;
}
kfree(dfa);
}
}
/**
* aa_dfa_free_kref - free aa_dfa by kref (called by aa_put_dfa)
* @kr: kref callback for freeing of a dfa (NOT NULL)
*/
void aa_dfa_free_kref(struct kref *kref)
{
struct aa_dfa *dfa = container_of(kref, struct aa_dfa, count);
dfa_free(dfa);
}
/**
* aa_dfa_unpack - unpack the binary tables of a serialized dfa
* @blob: aligned serialized stream of data to unpack (NOT NULL)
* @size: size of data to unpack
* @flags: flags controlling what type of accept tables are acceptable
*
* Unpack a dfa that has been serialized. To find information on the dfa
* format look in Documentation/apparmor.txt
* Assumes the dfa @blob stream has been aligned on a 8 byte boundry
*
* Returns: an unpacked dfa ready for matching or ERR_PTR on failure
*/
struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags)
{
int hsize;
int error = -ENOMEM;
char *data = blob;
struct table_header *table = NULL;
struct aa_dfa *dfa = kzalloc(sizeof(struct aa_dfa), GFP_KERNEL);
if (!dfa)
goto fail;
kref_init(&dfa->count);
error = -EPROTO;
/* get dfa table set header */
if (size < sizeof(struct table_set_header))
goto fail;
if (ntohl(*(u32 *) data) != YYTH_MAGIC)
goto fail;
hsize = ntohl(*(u32 *) (data + 4));
if (size < hsize)
goto fail;
dfa->flags = ntohs(*(u16 *) (data + 12));
data += hsize;
size -= hsize;
while (size > 0) {
table = unpack_table(data, size);
if (!table)
goto fail;
switch (table->td_id) {
case YYTD_ID_ACCEPT:
if (!(table->td_flags & ACCEPT1_FLAGS(flags)))
goto fail;
break;
case YYTD_ID_ACCEPT2:
if (!(table->td_flags & ACCEPT2_FLAGS(flags)))
goto fail;
break;
case YYTD_ID_BASE:
if (table->td_flags != YYTD_DATA32)
goto fail;
break;
case YYTD_ID_DEF:
case YYTD_ID_NXT:
case YYTD_ID_CHK:
if (table->td_flags != YYTD_DATA16)
goto fail;
break;
case YYTD_ID_EC:
if (table->td_flags != YYTD_DATA8)
goto fail;
break;
default:
goto fail;
}
/* check for duplicate table entry */
if (dfa->tables[table->td_id])
goto fail;
dfa->tables[table->td_id] = table;
data += table_size(table->td_lolen, table->td_flags);
size -= table_size(table->td_lolen, table->td_flags);
table = NULL;
}
error = verify_dfa(dfa, flags);
if (error)
goto fail;
return dfa;
fail:
kvfree(table);
dfa_free(dfa);
return ERR_PTR(error);
}
/**
* aa_dfa_match_len - traverse @dfa to find state @str stops at
* @dfa: the dfa to match @str against (NOT NULL)
* @start: the state of the dfa to start matching in
* @str: the string of bytes to match against the dfa (NOT NULL)
* @len: length of the string of bytes to match
*
* aa_dfa_match_len will match @str against the dfa and return the state it
* finished matching in. The final state can be used to look up the accepting
* label, or as the start state of a continuing match.
*
* This function will happily match again the 0 byte and only finishes
* when @len input is consumed.
*
* Returns: final state reached after input is consumed
*/
unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int start,
const char *str, int len)
{
u16 *def = DEFAULT_TABLE(dfa);
u32 *base = BASE_TABLE(dfa);
u16 *next = NEXT_TABLE(dfa);
u16 *check = CHECK_TABLE(dfa);
unsigned int state = start, pos;
if (state == 0)
return 0;
/* current state is <state>, matching character *str */
if (dfa->tables[YYTD_ID_EC]) {
/* Equivalence class table defined */
u8 *equiv = EQUIV_TABLE(dfa);
/* default is direct to next state */
for (; len; len--) {
pos = base[state] + equiv[(u8) *str++];
if (check[pos] == state)
state = next[pos];
else
state = def[state];
}
} else {
/* default is direct to next state */
for (; len; len--) {
pos = base[state] + (u8) *str++;
if (check[pos] == state)
state = next[pos];
else
state = def[state];
}
}
return state;
}
/**
* aa_dfa_next_state - traverse @dfa to find state @str stops at
* @dfa: the dfa to match @str against (NOT NULL)
* @start: the state of the dfa to start matching in
* @str: the null terminated string of bytes to match against the dfa (NOT NULL)
*
* aa_dfa_next_state will match @str against the dfa and return the state it
* finished matching in. The final state can be used to look up the accepting
* label, or as the start state of a continuing match.
*
* Returns: final state reached after input is consumed
*/
unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start,
const char *str)
{
return aa_dfa_match_len(dfa, start, str, strlen(str));
}
