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/* Copyright (C) 2007-2010 Open Information Security Foundation
*
* You can copy, redistribute or modify this Program under the terms of
* the GNU General Public License version 2 as published by the Free
* Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* version 2 along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*/
/**
* \file
*
* \author Pablo Rincon Crespo <pablo.rincon.crespo@gmail.com>
*
* Bs2Bm use a simple context array to determine the charactes
* that are not present on the pattern. This way on partial matches
* broken by a char not present, we can skip to the next character
* making less checks
*/
#include "suricata-common.h"
#include "suricata.h"
#include "util-spm-bs2bm.h"
/**
* \brief Array setup function for Bs2Bm of bad characters index (not found at the needle)
*
* \param neddle pointer to the pattern we ar searching for
* \param needle_len length limit of the needle
* \param badchars pointer to an empty array of bachars. The array prepared contains
* characters that can't be inside the needle_len. So the skips can be
* faster
*/
void Bs2BmBadchars(const uint8_t *needle, uint16_t needle_len, uint8_t *badchars)
{
uint32_t i;
for (i = 0; i < ALPHABET_SIZE; i++)
badchars[i] = 1;
/* set to 0 the values where index as ascii is present
* because they are not badchars
*/
for (i = 0; i < needle_len; i++)
badchars[needle[i]] = 0;
}
/**
* \brief Array setup function for Bs2BmNocase of bad characters index (not found at the needle)
*
* \param neddle pointer to the pattern we ar searching for
* \param needle_len length limit of the needle
* \param badchars pointer to an empty array of bachars. The array prepared contains
* characters that can't be inside the needle_len. So the skips can be
* faster
*/
void Bs2BmBadcharsNocase(const uint8_t *needle, uint16_t needle_len, uint8_t *badchars)
{
uint32_t i;
for (i = 0; i < ALPHABET_SIZE; i++)
badchars[i] = 1;
/* set to 0 the values where index as ascii is present
* because they are not badchars
*/
for (i = 0; i < needle_len; i++) {
badchars[u8_tolower(needle[i])] = 0;
}
}
/**
* \brief Basic search with a bad characters array. The array badchars contains
* flags at character's ascii index that can't be inside the needle. So the skips can be
* faster
*
* \param haystack pointer to the buffer to search in
* \param haystack_len length limit of the buffer
* \param neddle pointer to the pattern we ar searching for
* \param needle_len length limit of the needle
* \param badchars pointer to an array of bachars prepared by Bs2BmBadchars()
*
* \retval ptr to start of the match; NULL if no match
*/
uint8_t * Bs2Bm(const uint8_t *haystack, uint32_t haystack_len, const uint8_t *needle, uint16_t needle_len, uint8_t badchars[])
{
const uint8_t *h, *n;
const uint8_t *hmax = haystack + haystack_len;
const uint8_t *nmax = needle + needle_len;
if (needle_len == 0 || needle_len > haystack_len)
return NULL;
for (n = needle; nmax - n <= hmax - haystack; haystack++) {
if (*haystack != *n) {
continue;
}
/* one byte needles */
if (needle_len == 1)
return (uint8_t *)haystack;
for (h = haystack+1, n++; nmax - n <= hmax - haystack; h++, n++) {
if (*h != *n) {
if (badchars[*h] == 1) {
/* skip it! */
haystack = h;
}
break;
}
/* if we run out of needle we fully matched */
if (n == nmax - 1 ) {
return (uint8_t *)haystack;
}
}
n = needle;
}
return NULL;
}
/**
* \brief Basic search case less with a bad characters array. The array badchars contains
* flags at character's ascii index that can't be inside the needle. So the skips can be
* faster
*
* \param haystack pointer to the buffer to search in
* \param haystack_len length limit of the buffer
* \param neddle pointer to the pattern we ar searching for
* \param needle_len length limit of the needle
* \param badchars pointer to an array of bachars prepared by Bs2BmBadchars()
*
* \retval ptr to start of the match; NULL if no match
*/
uint8_t *Bs2BmNocase(const uint8_t *haystack, uint32_t haystack_len, const uint8_t *needle, uint16_t needle_len, uint8_t badchars[])
{
const uint8_t *h, *n;
const uint8_t *hmax = haystack + haystack_len;
const uint8_t *nmax = needle + needle_len;
if (needle_len == 0 || needle_len > haystack_len)
return NULL;
for (n = needle; nmax - n <= hmax - haystack; haystack++) {
if (u8_tolower(*haystack) != u8_tolower(*n)) {
continue;
}
/* one byte needles */
if (needle_len == 1)
return (uint8_t *)haystack;
for (h = haystack+1, n++; nmax - n <= hmax - haystack; h++, n++) {
if (u8_tolower(*h) != u8_tolower(*n)) {
if (badchars[u8_tolower(*h)] == 1) {
/* skip it! */
haystack = h;
}
break;
}
/* if we run out of needle we fully matched */
if (n == nmax - 1) {
return (uint8_t *)haystack;
}
}
n = needle;
}
return NULL;
}
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