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|
/*
* AppArmor security module
*
* This file contains AppArmor dfa based regular expression matching engine
*
* Copyright (C) 1998-2008 Novell/SUSE
* Copyright 2009-2012 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/lib.h"
#include "include/match.h"
#define base_idx(X) ((X) & 0xffffff)
static char nulldfa_src[] = {
#include "nulldfa.in"
};
struct aa_dfa *nulldfa;
static char stacksplitdfa_src[] = {
#include "stacksplitdfa.in"
};
struct aa_dfa *stacksplitdfa;
int aa_setup_dfa_engine(void)
{
int error;
nulldfa = aa_dfa_unpack(nulldfa_src, sizeof(nulldfa_src),
TO_ACCEPT1_FLAG(YYTD_DATA32) |
TO_ACCEPT2_FLAG(YYTD_DATA32));
if (IS_ERR(nulldfa)) {
error = PTR_ERR(nulldfa);
nulldfa = NULL;
return error;
}
stacksplitdfa = aa_dfa_unpack(stacksplitdfa_src,
sizeof(stacksplitdfa_src),
TO_ACCEPT1_FLAG(YYTD_DATA32) |
TO_ACCEPT2_FLAG(YYTD_DATA32));
if (IS_ERR(stacksplitdfa)) {
aa_put_dfa(nulldfa);
nulldfa = NULL;
error = PTR_ERR(stacksplitdfa);
stacksplitdfa = NULL;
return error;
}
return 0;
}
void aa_teardown_dfa_engine(void)
{
aa_put_dfa(stacksplitdfa);
aa_put_dfa(nulldfa);
}
/**
* 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 kfree)
*/
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(*(__be16 *) (blob)) - 1;
if (th.td_id > YYTD_ID_MAX)
goto out;
th.td_flags = be16_to_cpu(*(__be16 *) (blob + 2));
th.td_lolen = be32_to_cpu(*(__be32 *) (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 = kvzalloc(tsize, GFP_KERNEL);
if (table) {
table->td_id = th.td_id;
table->td_flags = th.td_flags;
table->td_lolen = th.td_lolen;
if (th.td_flags == YYTD_DATA8)
UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
u8, u8, byte_to_byte);
else if (th.td_flags == YYTD_DATA16)
UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
u16, __be16, be16_to_cpu);
else if (th.td_flags == YYTD_DATA32)
UNPACK_ARRAY(table->td_data, blob, th.td_lolen,
u32, __be32, be32_to_cpu);
else
goto fail;
/* 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();
}
out:
return table;
fail:
kvfree(table);
return 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
* NOTE: this does not valid accept table values
*
* Returns: %0 else error code on failure to verify
*/
static int verify_table_headers(struct table_header **tables, int flags)
{
size_t state_count, trans_count;
int error = -EPROTO;
/* check that required tables exist */
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 = tables[YYTD_ID_BASE]->td_lolen;
if (ACCEPT1_FLAGS(flags)) {
if (!tables[YYTD_ID_ACCEPT])
goto out;
if (state_count != tables[YYTD_ID_ACCEPT]->td_lolen)
goto out;
}
if (ACCEPT2_FLAGS(flags)) {
if (!tables[YYTD_ID_ACCEPT2])
goto out;
if (state_count != tables[YYTD_ID_ACCEPT2]->td_lolen)
goto out;
}
if (state_count != tables[YYTD_ID_DEF]->td_lolen)
goto out;
/* next.size == chk.size */
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 (tables[YYTD_ID_EC] && tables[YYTD_ID_EC]->td_lolen != 256)
goto out;
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) {
pr_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;
}
/* Now that all the other tables are verified, verify diffencoding */
for (i = 0; i < state_count; i++) {
size_t j, k;
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;
}
/**
* 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/admin-guide/LSM/apparmor.rst
* Assumes the dfa @blob stream has been aligned on a 8 byte boundary
*
* 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(*(__be32 *) data) != YYTH_MAGIC)
goto fail;
hsize = ntohl(*(__be32 *) (data + 4));
if (size < hsize)
goto fail;
dfa->flags = ntohs(*(__be16 *) (data + 12));
if (dfa->flags != 0 && dfa->flags != YYTH_FLAG_DIFF_ENCODE)
goto fail;
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_table_headers(dfa->tables, flags);
if (error)
goto fail;
if (flags & DFA_FLAG_VERIFY_STATES) {
error = verify_dfa(dfa);
if (error)
goto fail;
}
return dfa;
fail:
kvfree(table);
dfa_free(dfa);
return ERR_PTR(error);
}
#define match_char(state, def, base, next, check, C) \
do { \
u32 b = (base)[(state)]; \
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]; \
break; \
} while (1)
/**
* 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;
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);
for (; len; len--)
match_char(state, def, base, next, check,
equiv[(u8) *str++]);
} else {
/* default is direct to next state */
for (; len; len--)
match_char(state, def, base, next, check, (u8) *str++);
}
return state;
}
/**
* aa_dfa_match - 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_match 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)
{
u16 *def = DEFAULT_TABLE(dfa);
u32 *base = BASE_TABLE(dfa);
u16 *next = NEXT_TABLE(dfa);
u16 *check = CHECK_TABLE(dfa);
unsigned int state = start;
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 */
while (*str)
match_char(state, def, base, next, check,
equiv[(u8) *str++]);
} else {
/* default is direct to next state */
while (*str)
match_char(state, def, base, next, check, (u8) *str++);
}
return state;
}
/**
* aa_dfa_next - step one character to the next state in the dfa
* @dfa: the dfa to tranverse (NOT NULL)
* @state: the state to start in
* @c: the input character to transition on
*
* aa_dfa_match will step through the dfa by one input character @c
*
* Returns: state reach after input @c
*/
unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state,
const char c)
{
u16 *def = DEFAULT_TABLE(dfa);
u32 *base = BASE_TABLE(dfa);
u16 *next = NEXT_TABLE(dfa);
u16 *check = CHECK_TABLE(dfa);
/* current state is <state>, matching character *str */
if (dfa->tables[YYTD_ID_EC]) {
/* Equivalence class table defined */
u8 *equiv = EQUIV_TABLE(dfa);
match_char(state, def, base, next, check, equiv[(u8) c]);
} else
match_char(state, def, base, next, check, (u8) c);
return state;
}
/**
* aa_dfa_match_until - traverse @dfa until accept state or end of input
* @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)
* @retpos: first character in str after match OR end of string
*
* aa_dfa_match 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_until(struct aa_dfa *dfa, unsigned int start,
const char *str, const char **retpos)
{
u16 *def = DEFAULT_TABLE(dfa);
u32 *base = BASE_TABLE(dfa);
u16 *next = NEXT_TABLE(dfa);
u16 *check = CHECK_TABLE(dfa);
u32 *accept = ACCEPT_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 */
while (*str) {
pos = base_idx(base[state]) + equiv[(u8) *str++];
if (check[pos] == state)
state = next[pos];
else
state = def[state];
if (accept[state])
break;
}
} else {
/* default is direct to next state */
while (*str) {
pos = base_idx(base[state]) + (u8) *str++;
if (check[pos] == state)
state = next[pos];
else
state = def[state];
if (accept[state])
break;
}
}
*retpos = str;
return state;
}
/**
* aa_dfa_matchn_until - traverse @dfa until accept or @n bytes consumed
* @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)
* @n: length of the string of bytes to match
* @retpos: first character in str after match OR str + n
*
* 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 @n input is consumed.
*
* Returns: final state reached after input is consumed
*/
unsigned int aa_dfa_matchn_until(struct aa_dfa *dfa, unsigned int start,
const char *str, int n, const char **retpos)
{
u16 *def = DEFAULT_TABLE(dfa);
u32 *base = BASE_TABLE(dfa);
u16 *next = NEXT_TABLE(dfa);
u16 *check = CHECK_TABLE(dfa);
u32 *accept = ACCEPT_TABLE(dfa);
unsigned int state = start, pos;
*retpos = NULL;
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 (; n; n--) {
pos = base_idx(base[state]) + equiv[(u8) *str++];
if (check[pos] == state)
state = next[pos];
else
state = def[state];
if (accept[state])
break;
}
} else {
/* default is direct to next state */
for (; n; n--) {
pos = base_idx(base[state]) + (u8) *str++;
if (check[pos] == state)
state = next[pos];
else
state = def[state];
if (accept[state])
break;
}
}
*retpos = str;
return state;
}
#define inc_wb_pos(wb) \
do { \
wb->pos = (wb->pos + 1) & (wb->size - 1); \
wb->len = (wb->len + 1) & (wb->size - 1); \
} while (0)
/* For DFAs that don't support extended tagging of states */
static bool is_loop(struct match_workbuf *wb, unsigned int state,
unsigned int *adjust)
{
unsigned int pos = wb->pos;
unsigned int i;
if (wb->history[pos] < state)
return false;
for (i = 0; i <= wb->len; i++) {
if (wb->history[pos] == state) {
*adjust = i;
return true;
}
if (pos == 0)
pos = wb->size;
pos--;
}
*adjust = i;
return true;
}
static unsigned int leftmatch_fb(struct aa_dfa *dfa, unsigned int start,
const char *str, struct match_workbuf *wb,
unsigned int *count)
{
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;
AA_BUG(!dfa);
AA_BUG(!str);
AA_BUG(!wb);
AA_BUG(!count);
*count = 0;
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 */
while (*str) {
unsigned int adjust;
wb->history[wb->pos] = state;
pos = base_idx(base[state]) + equiv[(u8) *str++];
if (check[pos] == state)
state = next[pos];
else
state = def[state];
if (is_loop(wb, state, &adjust)) {
state = aa_dfa_match(dfa, state, str);
*count -= adjust;
goto out;
}
inc_wb_pos(wb);
(*count)++;
}
} else {
/* default is direct to next state */
while (*str) {
unsigned int adjust;
wb->history[wb->pos] = state;
pos = base_idx(base[state]) + (u8) *str++;
if (check[pos] == state)
state = next[pos];
else
state = def[state];
if (is_loop(wb, state, &adjust)) {
state = aa_dfa_match(dfa, state, str);
*count -= adjust;
goto out;
}
inc_wb_pos(wb);
(*count)++;
}
}
out:
if (!state)
*count = 0;
return state;
}
/**
* aa_dfa_leftmatch - 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)
* @count: current count of longest left.
*
* aa_dfa_match 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_leftmatch(struct aa_dfa *dfa, unsigned int start,
const char *str, unsigned int *count)
{
DEFINE_MATCH_WB(wb);
/* TODO: match for extended state dfas */
return leftmatch_fb(dfa, start, str, &wb, count);
}
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