426 lines
15 KiB
C
426 lines
15 KiB
C
/*
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* Copyright (C) 2013-2022 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
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* Copyright (C) 2007-2013 Sourcefire, Inc.
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*
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* Authors: Tomasz Kojm
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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* MA 02110-1301, USA.
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*/
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#if HAVE_CONFIG_H
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#include "clamav-config.h"
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#endif
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#include <stdio.h>
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#include <assert.h>
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#include "clamav.h"
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#include "memory.h"
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#include "others.h"
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#include "matcher.h"
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#include "matcher-bm.h"
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#include "filetypes.h"
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#include "filtering.h"
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#include "mpool.h"
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#define BM_MIN_LENGTH 3
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#define BM_BLOCK_SIZE 3
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#define HASH(a, b, c) (211 * a + 37 * b + c)
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cl_error_t cli_bm_addpatt(struct cli_matcher *root, struct cli_bm_patt *pattern, const char *offset)
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{
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uint16_t idx, i;
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const unsigned char *pt = pattern->pattern;
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struct cli_bm_patt *prev, *next = NULL;
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cl_error_t ret;
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if (pattern->length < BM_MIN_LENGTH) {
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cli_errmsg("cli_bm_addpatt: Signature for %s is too short\n", pattern->virname);
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return CL_EMALFDB;
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}
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if (CL_SUCCESS != (ret = cli_caloff(offset, NULL, root->type, pattern->offdata, &pattern->offset_min, &pattern->offset_max))) {
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cli_errmsg("cli_bm_addpatt: Can't calculate offset for signature %s\n", pattern->virname);
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return ret;
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}
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if (pattern->offdata[0] != CLI_OFF_ANY) {
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if (pattern->offdata[0] == CLI_OFF_ABSOLUTE)
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root->bm_absoff_num++;
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else
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root->bm_reloff_num++;
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}
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/* bm_offmode doesn't use the prefilter for BM signatures anyway, so
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* don't add these to the filter. */
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if (root->filter && !root->bm_offmode) {
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/* the bm_suffix load balancing below can shorten the sig,
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* we want to see the entire signature! */
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if (filter_add_static(root->filter, pattern->pattern, pattern->length, pattern->virname) == -1) {
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cli_warnmsg("cli_bm_addpatt: cannot use filter for trie\n");
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MPOOL_FREE(root->mempool, root->filter);
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root->filter = NULL;
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}
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/* TODO: should this affect maxpatlen? */
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}
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#if BM_MIN_LENGTH == BM_BLOCK_SIZE
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/* try to load balance bm_suffix (at the cost of bm_shift) */
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for (i = 0; i < pattern->length - BM_BLOCK_SIZE + 1; i++) {
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idx = HASH(pt[i], pt[i + 1], pt[i + 2]);
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if (!root->bm_suffix[idx]) {
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if (i) {
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pattern->prefix = pattern->pattern;
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pattern->prefix_length = i;
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pattern->pattern = &pattern->pattern[i];
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pattern->length -= i;
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pt = pattern->pattern;
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}
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break;
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}
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}
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#endif
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for (i = 0; i <= BM_MIN_LENGTH - BM_BLOCK_SIZE; i++) {
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idx = HASH(pt[i], pt[i + 1], pt[i + 2]);
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root->bm_shift[idx] = MIN(root->bm_shift[idx], BM_MIN_LENGTH - BM_BLOCK_SIZE - i);
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}
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prev = next = root->bm_suffix[idx];
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while (next) {
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if (pt[0] >= next->pattern0)
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break;
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prev = next;
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next = next->next;
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}
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if (next == root->bm_suffix[idx]) {
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pattern->next = root->bm_suffix[idx];
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if (root->bm_suffix[idx])
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pattern->cnt = root->bm_suffix[idx]->cnt;
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root->bm_suffix[idx] = pattern;
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} else {
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pattern->next = prev->next;
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prev->next = pattern;
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}
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pattern->pattern0 = pattern->pattern[0];
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root->bm_suffix[idx]->cnt++;
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if (root->bm_offmode) {
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root->bm_pattab = (struct cli_bm_patt **)MPOOL_REALLOC2(root->mempool, root->bm_pattab, (root->bm_patterns + 1) * sizeof(struct cli_bm_patt *));
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if (!root->bm_pattab) {
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cli_errmsg("cli_bm_addpatt: Can't allocate memory for root->bm_pattab\n");
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return CL_EMEM;
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}
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root->bm_pattab[root->bm_patterns] = pattern;
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if (pattern->offdata[0] != CLI_OFF_ABSOLUTE)
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pattern->offset_min = root->bm_patterns;
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}
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root->bm_patterns++;
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return CL_SUCCESS;
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}
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cl_error_t cli_bm_init(struct cli_matcher *root)
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{
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uint16_t i, size = HASH(255, 255, 255) + 1;
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#ifdef USE_MPOOL
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assert(root->mempool && "mempool must be initialized");
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#endif
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if (!(root->bm_shift = (uint8_t *)MPOOL_CALLOC(root->mempool, size, sizeof(uint8_t))))
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return CL_EMEM;
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if (!(root->bm_suffix = (struct cli_bm_patt **)MPOOL_CALLOC(root->mempool, size, sizeof(struct cli_bm_patt *)))) {
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MPOOL_FREE(root->mempool, root->bm_shift);
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return CL_EMEM;
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}
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for (i = 0; i < size; i++)
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root->bm_shift[i] = BM_MIN_LENGTH - BM_BLOCK_SIZE + 1;
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return CL_SUCCESS;
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}
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cl_error_t cli_bm_initoff(const struct cli_matcher *root, struct cli_bm_off *data, const struct cli_target_info *info)
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{
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cl_error_t ret;
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unsigned int i;
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struct cli_bm_patt *patt;
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if (!root->bm_patterns) {
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data->offtab = data->offset = NULL;
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data->cnt = data->pos = 0;
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return CL_SUCCESS;
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}
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data->cnt = data->pos = 0;
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data->offtab = (uint32_t *)cli_malloc(root->bm_patterns * sizeof(uint32_t));
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if (!data->offtab) {
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cli_errmsg("cli_bm_initoff: Can't allocate memory for data->offtab\n");
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return CL_EMEM;
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}
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data->offset = (uint32_t *)cli_malloc(root->bm_patterns * sizeof(uint32_t));
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if (!data->offset) {
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cli_errmsg("cli_bm_initoff: Can't allocate memory for data->offset\n");
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free(data->offtab);
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return CL_EMEM;
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}
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for (i = 0; i < root->bm_patterns; i++) {
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patt = root->bm_pattab[i];
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if (patt->offdata[0] == CLI_OFF_ABSOLUTE) {
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data->offtab[data->cnt] = patt->offset_min + patt->prefix_length;
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if (data->offtab[data->cnt] >= info->fsize)
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continue;
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data->cnt++;
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} else if (CL_SUCCESS != (ret = cli_caloff(NULL, info, root->type, patt->offdata, &data->offset[patt->offset_min], NULL))) {
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cli_errmsg("cli_bm_initoff: Can't calculate relative offset in signature for %s\n", patt->virname);
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free(data->offtab);
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free(data->offset);
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return ret;
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} else if ((data->offset[patt->offset_min] != CLI_OFF_NONE) && (data->offset[patt->offset_min] + patt->length <= info->fsize)) {
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if (!data->cnt || (data->offset[patt->offset_min] + patt->prefix_length != data->offtab[data->cnt - 1])) {
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data->offtab[data->cnt] = data->offset[patt->offset_min] + patt->prefix_length;
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if (data->offtab[data->cnt] >= info->fsize)
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continue;
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data->cnt++;
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}
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}
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}
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cli_qsort(data->offtab, data->cnt, sizeof(uint32_t), NULL);
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return CL_SUCCESS;
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}
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void cli_bm_freeoff(struct cli_bm_off *data)
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{
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free(data->offset);
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data->offset = NULL;
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free(data->offtab);
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data->offtab = NULL;
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}
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void cli_bm_free(struct cli_matcher *root)
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{
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struct cli_bm_patt *patt, *prev;
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uint16_t i, size = HASH(255, 255, 255) + 1;
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if (root->bm_shift)
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MPOOL_FREE(root->mempool, root->bm_shift);
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if (root->bm_pattab)
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MPOOL_FREE(root->mempool, root->bm_pattab);
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if (root->bm_suffix) {
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for (i = 0; i < size; i++) {
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patt = root->bm_suffix[i];
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while (patt) {
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prev = patt;
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patt = patt->next;
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if (prev->prefix)
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MPOOL_FREE(root->mempool, prev->prefix);
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else
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MPOOL_FREE(root->mempool, prev->pattern);
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if (prev->virname)
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MPOOL_FREE(root->mempool, prev->virname);
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MPOOL_FREE(root->mempool, prev);
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}
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}
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MPOOL_FREE(root->mempool, root->bm_suffix);
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}
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}
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cl_error_t cli_bm_scanbuff(const unsigned char *buffer, uint32_t length, const char **virname, const struct cli_bm_patt **patt, const struct cli_matcher *root, uint32_t offset, const struct cli_target_info *info, struct cli_bm_off *offdata, cli_ctx *ctx)
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{
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uint32_t i, j, off, off_min, off_max;
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uint8_t found, pchain, shift;
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uint16_t idx, idxchk;
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struct cli_bm_patt *p;
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const unsigned char *bp, *pt;
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unsigned char prefix;
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cl_error_t ret;
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int viruses_found = 0;
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if (!root || !root->bm_shift)
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return CL_CLEAN;
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if (length < BM_MIN_LENGTH)
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return CL_CLEAN;
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i = BM_MIN_LENGTH - BM_BLOCK_SIZE;
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if (offdata) {
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if (!offdata->cnt)
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return CL_CLEAN;
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if (offdata->pos == offdata->cnt)
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offdata->pos--;
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for (; offdata->pos && offdata->offtab[offdata->pos] > offset; offdata->pos--)
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;
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if (offdata->offtab[offdata->pos] < offset)
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offdata->pos++;
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if (offdata->pos >= offdata->cnt)
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return CL_CLEAN;
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i += offdata->offtab[offdata->pos] - offset;
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}
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for (; i < length - BM_BLOCK_SIZE + 1;) {
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idx = HASH(buffer[i], buffer[i + 1], buffer[i + 2]);
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shift = root->bm_shift[idx];
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if (shift == 0) {
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prefix = buffer[i - BM_MIN_LENGTH + BM_BLOCK_SIZE];
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p = root->bm_suffix[idx];
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if (p && p->cnt == 1 && p->pattern0 != prefix) {
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if (offdata) {
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off = offset + i - BM_MIN_LENGTH + BM_BLOCK_SIZE;
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for (; offdata->pos < offdata->cnt && off >= offdata->offtab[offdata->pos]; offdata->pos++)
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;
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if (offdata->pos == offdata->cnt || off >= offdata->offtab[offdata->pos]) {
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if (viruses_found)
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return CL_VIRUS;
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return CL_CLEAN;
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}
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i += offdata->offtab[offdata->pos] - off;
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} else {
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i++;
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}
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continue;
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}
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pchain = 0;
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while (p) {
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if (p->pattern0 != prefix) {
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if (pchain)
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break;
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p = p->next;
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continue;
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} else
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pchain = 1;
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off = i - BM_MIN_LENGTH + BM_BLOCK_SIZE;
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bp = buffer + off;
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if ((off + p->length > length) || (p->prefix_length > off)) {
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p = p->next;
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continue;
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}
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if (offdata) {
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if (p->offdata[0] == CLI_OFF_ABSOLUTE) {
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if (p->offset_min != offset + off - p->prefix_length) {
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p = p->next;
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continue;
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}
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} else if ((offdata->offset[p->offset_min] == CLI_OFF_NONE) || (offdata->offset[p->offset_min] != offset + off - p->prefix_length)) {
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p = p->next;
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continue;
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}
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}
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idxchk = MIN(p->length, length - off) - 1;
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if (idxchk) {
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if ((bp[idxchk] != p->pattern[idxchk]) || (bp[idxchk / 2] != p->pattern[idxchk / 2])) {
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p = p->next;
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continue;
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}
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}
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if (p->prefix_length) {
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off -= p->prefix_length;
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bp -= p->prefix_length;
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pt = p->prefix;
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} else {
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pt = p->pattern;
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}
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found = 1;
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for (j = 0; j < p->length + p->prefix_length && off < length; j++, off++) {
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if (bp[j] != pt[j]) {
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found = 0;
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break;
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}
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}
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if (found && (p->boundary & BM_BOUNDARY_EOL)) {
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if (off != length) {
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p = p->next;
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continue;
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}
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}
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if (found && p->length + p->prefix_length == j) {
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if (!offdata && (p->offset_min != CLI_OFF_ANY)) {
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if (p->offdata[0] != CLI_OFF_ABSOLUTE) {
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if (!info) {
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p = p->next;
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continue;
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}
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ret = cli_caloff(NULL, info, root->type, p->offdata, &off_min, &off_max);
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if (ret != CL_SUCCESS) {
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cli_errmsg("cli_bm_scanbuff: Can't calculate relative offset in signature for %s\n", p->virname);
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return ret;
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}
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} else {
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off_min = p->offset_min;
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off_max = p->offset_max;
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}
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off = offset + i - p->prefix_length - BM_MIN_LENGTH + BM_BLOCK_SIZE;
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if (off_min == CLI_OFF_NONE || off_max < off || off_min > off) {
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p = p->next;
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continue;
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}
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}
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viruses_found += 1;
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if (virname) {
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*virname = p->virname;
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if (ctx != NULL && SCAN_ALLMATCHES) {
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ret = cli_append_virus(ctx, *virname);
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if (ret == CL_CLEAN && viruses_found > 0) {
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viruses_found -= 1;
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}
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}
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}
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if (patt)
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*patt = p;
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if (ctx != NULL && !SCAN_ALLMATCHES)
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return CL_VIRUS;
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}
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p = p->next;
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}
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shift = 1;
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}
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if (offdata) {
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off = offset + i - BM_MIN_LENGTH + BM_BLOCK_SIZE;
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for (; offdata->pos < offdata->cnt && off >= offdata->offtab[offdata->pos]; offdata->pos++)
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;
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if (offdata->pos == offdata->cnt || off >= offdata->offtab[offdata->pos]) {
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if (viruses_found > 0) {
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return CL_VIRUS;
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}
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return CL_CLEAN;
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}
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i += offdata->offtab[offdata->pos] - off;
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} else {
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i += shift;
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}
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}
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if (viruses_found > 0) {
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return CL_VIRUS;
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}
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return CL_CLEAN;
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}
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