/*
 *  Copyright (C) 2013-2022 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
 *  Copyright (C) 2007-2013 Sourcefire, Inc.
 *
 *  Authors: Tomasz Kojm
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it 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
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 *  MA 02110-1301, USA.
 */

#if HAVE_CONFIG_H
#include "clamav-config.h"
#endif

#include <stdio.h>
#include <assert.h>

#include "clamav.h"
#include "memory.h"
#include "others.h"
#include "matcher.h"
#include "matcher-bm.h"
#include "filetypes.h"
#include "filtering.h"

#include "mpool.h"

#define BM_MIN_LENGTH 3
#define BM_BLOCK_SIZE 3
#define HASH(a, b, c) (211 * a + 37 * b + c)

cl_error_t cli_bm_addpatt(struct cli_matcher *root, struct cli_bm_patt *pattern, const char *offset)
{
    uint16_t idx, i;
    const unsigned char *pt = pattern->pattern;
    struct cli_bm_patt *prev, *next = NULL;
    cl_error_t ret;

    if (pattern->length < BM_MIN_LENGTH) {
        cli_errmsg("cli_bm_addpatt: Signature for %s is too short\n", pattern->virname);
        return CL_EMALFDB;
    }

    if (CL_SUCCESS != (ret = cli_caloff(offset, NULL, root->type, pattern->offdata, &pattern->offset_min, &pattern->offset_max))) {
        cli_errmsg("cli_bm_addpatt: Can't calculate offset for signature %s\n", pattern->virname);
        return ret;
    }
    if (pattern->offdata[0] != CLI_OFF_ANY) {
        if (pattern->offdata[0] == CLI_OFF_ABSOLUTE)
            root->bm_absoff_num++;
        else
            root->bm_reloff_num++;
    }

    /* bm_offmode doesn't use the prefilter for BM signatures anyway, so
     * don't add these to the filter. */
    if (root->filter && !root->bm_offmode) {
        /* the bm_suffix load balancing below can shorten the sig,
         * we want to see the entire signature! */
        if (filter_add_static(root->filter, pattern->pattern, pattern->length, pattern->virname) == -1) {
            cli_warnmsg("cli_bm_addpatt: cannot use filter for trie\n");
            MPOOL_FREE(root->mempool, root->filter);
            root->filter = NULL;
        }
        /* TODO: should this affect maxpatlen? */
    }

#if BM_MIN_LENGTH == BM_BLOCK_SIZE
    /* try to load balance bm_suffix (at the cost of bm_shift) */
    for (i = 0; i < pattern->length - BM_BLOCK_SIZE + 1; i++) {
        idx = HASH(pt[i], pt[i + 1], pt[i + 2]);
        if (!root->bm_suffix[idx]) {
            if (i) {
                pattern->prefix        = pattern->pattern;
                pattern->prefix_length = i;
                pattern->pattern       = &pattern->pattern[i];
                pattern->length -= i;
                pt = pattern->pattern;
            }
            break;
        }
    }
#endif

    for (i = 0; i <= BM_MIN_LENGTH - BM_BLOCK_SIZE; i++) {
        idx                 = HASH(pt[i], pt[i + 1], pt[i + 2]);
        root->bm_shift[idx] = MIN(root->bm_shift[idx], BM_MIN_LENGTH - BM_BLOCK_SIZE - i);
    }

    prev = next = root->bm_suffix[idx];
    while (next) {
        if (pt[0] >= next->pattern0)
            break;
        prev = next;
        next = next->next;
    }

    if (next == root->bm_suffix[idx]) {
        pattern->next = root->bm_suffix[idx];
        if (root->bm_suffix[idx])
            pattern->cnt = root->bm_suffix[idx]->cnt;
        root->bm_suffix[idx] = pattern;
    } else {
        pattern->next = prev->next;
        prev->next    = pattern;
    }
    pattern->pattern0 = pattern->pattern[0];
    root->bm_suffix[idx]->cnt++;

    if (root->bm_offmode) {
        root->bm_pattab = (struct cli_bm_patt **)MPOOL_REALLOC2(root->mempool, root->bm_pattab, (root->bm_patterns + 1) * sizeof(struct cli_bm_patt *));
        if (!root->bm_pattab) {
            cli_errmsg("cli_bm_addpatt: Can't allocate memory for root->bm_pattab\n");
            return CL_EMEM;
        }
        root->bm_pattab[root->bm_patterns] = pattern;
        if (pattern->offdata[0] != CLI_OFF_ABSOLUTE)
            pattern->offset_min = root->bm_patterns;
    }

    root->bm_patterns++;
    return CL_SUCCESS;
}

cl_error_t cli_bm_init(struct cli_matcher *root)
{
    uint16_t i, size = HASH(255, 255, 255) + 1;
#ifdef USE_MPOOL
    assert(root->mempool && "mempool must be initialized");
#endif

    if (!(root->bm_shift = (uint8_t *)MPOOL_CALLOC(root->mempool, size, sizeof(uint8_t))))
        return CL_EMEM;

    if (!(root->bm_suffix = (struct cli_bm_patt **)MPOOL_CALLOC(root->mempool, size, sizeof(struct cli_bm_patt *)))) {
        MPOOL_FREE(root->mempool, root->bm_shift);
        return CL_EMEM;
    }

    for (i = 0; i < size; i++)
        root->bm_shift[i] = BM_MIN_LENGTH - BM_BLOCK_SIZE + 1;

    return CL_SUCCESS;
}

cl_error_t cli_bm_initoff(const struct cli_matcher *root, struct cli_bm_off *data, const struct cli_target_info *info)
{
    cl_error_t ret;
    unsigned int i;
    struct cli_bm_patt *patt;

    if (!root->bm_patterns) {
        data->offtab = data->offset = NULL;
        data->cnt = data->pos = 0;
        return CL_SUCCESS;
    }

    data->cnt = data->pos = 0;
    data->offtab          = (uint32_t *)cli_malloc(root->bm_patterns * sizeof(uint32_t));
    if (!data->offtab) {
        cli_errmsg("cli_bm_initoff: Can't allocate memory for data->offtab\n");
        return CL_EMEM;
    }
    data->offset = (uint32_t *)cli_malloc(root->bm_patterns * sizeof(uint32_t));
    if (!data->offset) {
        cli_errmsg("cli_bm_initoff: Can't allocate memory for data->offset\n");
        free(data->offtab);
        return CL_EMEM;
    }
    for (i = 0; i < root->bm_patterns; i++) {
        patt = root->bm_pattab[i];
        if (patt->offdata[0] == CLI_OFF_ABSOLUTE) {
            data->offtab[data->cnt] = patt->offset_min + patt->prefix_length;
            if (data->offtab[data->cnt] >= info->fsize)
                continue;
            data->cnt++;
        } else if (CL_SUCCESS != (ret = cli_caloff(NULL, info, root->type, patt->offdata, &data->offset[patt->offset_min], NULL))) {
            cli_errmsg("cli_bm_initoff: Can't calculate relative offset in signature for %s\n", patt->virname);
            free(data->offtab);
            free(data->offset);
            return ret;
        } else if ((data->offset[patt->offset_min] != CLI_OFF_NONE) && (data->offset[patt->offset_min] + patt->length <= info->fsize)) {
            if (!data->cnt || (data->offset[patt->offset_min] + patt->prefix_length != data->offtab[data->cnt - 1])) {
                data->offtab[data->cnt] = data->offset[patt->offset_min] + patt->prefix_length;
                if (data->offtab[data->cnt] >= info->fsize)
                    continue;
                data->cnt++;
            }
        }
    }

    cli_qsort(data->offtab, data->cnt, sizeof(uint32_t), NULL);
    return CL_SUCCESS;
}

void cli_bm_freeoff(struct cli_bm_off *data)
{
    free(data->offset);
    data->offset = NULL;
    free(data->offtab);
    data->offtab = NULL;
}

void cli_bm_free(struct cli_matcher *root)
{
    struct cli_bm_patt *patt, *prev;
    uint16_t i, size = HASH(255, 255, 255) + 1;

    if (root->bm_shift)
        MPOOL_FREE(root->mempool, root->bm_shift);

    if (root->bm_pattab)
        MPOOL_FREE(root->mempool, root->bm_pattab);

    if (root->bm_suffix) {
        for (i = 0; i < size; i++) {
            patt = root->bm_suffix[i];
            while (patt) {
                prev = patt;
                patt = patt->next;
                if (prev->prefix)
                    MPOOL_FREE(root->mempool, prev->prefix);
                else
                    MPOOL_FREE(root->mempool, prev->pattern);
                if (prev->virname)
                    MPOOL_FREE(root->mempool, prev->virname);
                MPOOL_FREE(root->mempool, prev);
            }
        }
        MPOOL_FREE(root->mempool, root->bm_suffix);
    }
}

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)
{
    uint32_t i, j, off, off_min, off_max;
    uint8_t found, pchain, shift;
    uint16_t idx, idxchk;
    struct cli_bm_patt *p;
    const unsigned char *bp, *pt;
    unsigned char prefix;
    cl_error_t ret;
    int viruses_found = 0;

    if (!root || !root->bm_shift)
        return CL_CLEAN;

    if (length < BM_MIN_LENGTH)
        return CL_CLEAN;

    i = BM_MIN_LENGTH - BM_BLOCK_SIZE;
    if (offdata) {
        if (!offdata->cnt)
            return CL_CLEAN;
        if (offdata->pos == offdata->cnt)
            offdata->pos--;
        for (; offdata->pos && offdata->offtab[offdata->pos] > offset; offdata->pos--)
            ;
        if (offdata->offtab[offdata->pos] < offset)
            offdata->pos++;
        if (offdata->pos >= offdata->cnt)
            return CL_CLEAN;
        i += offdata->offtab[offdata->pos] - offset;
    }
    for (; i < length - BM_BLOCK_SIZE + 1;) {
        idx   = HASH(buffer[i], buffer[i + 1], buffer[i + 2]);
        shift = root->bm_shift[idx];

        if (shift == 0) {
            prefix = buffer[i - BM_MIN_LENGTH + BM_BLOCK_SIZE];
            p      = root->bm_suffix[idx];
            if (p && p->cnt == 1 && p->pattern0 != prefix) {
                if (offdata) {
                    off = offset + i - BM_MIN_LENGTH + BM_BLOCK_SIZE;
                    for (; offdata->pos < offdata->cnt && off >= offdata->offtab[offdata->pos]; offdata->pos++)
                        ;
                    if (offdata->pos == offdata->cnt || off >= offdata->offtab[offdata->pos]) {
                        if (viruses_found)
                            return CL_VIRUS;
                        return CL_CLEAN;
                    }
                    i += offdata->offtab[offdata->pos] - off;
                } else {
                    i++;
                }
                continue;
            }
            pchain = 0;
            while (p) {
                if (p->pattern0 != prefix) {
                    if (pchain)
                        break;
                    p = p->next;
                    continue;
                } else
                    pchain = 1;

                off = i - BM_MIN_LENGTH + BM_BLOCK_SIZE;
                bp  = buffer + off;

                if ((off + p->length > length) || (p->prefix_length > off)) {
                    p = p->next;
                    continue;
                }

                if (offdata) {
                    if (p->offdata[0] == CLI_OFF_ABSOLUTE) {
                        if (p->offset_min != offset + off - p->prefix_length) {
                            p = p->next;
                            continue;
                        }
                    } else if ((offdata->offset[p->offset_min] == CLI_OFF_NONE) || (offdata->offset[p->offset_min] != offset + off - p->prefix_length)) {
                        p = p->next;
                        continue;
                    }
                }

                idxchk = MIN(p->length, length - off) - 1;
                if (idxchk) {
                    if ((bp[idxchk] != p->pattern[idxchk]) || (bp[idxchk / 2] != p->pattern[idxchk / 2])) {
                        p = p->next;
                        continue;
                    }
                }

                if (p->prefix_length) {
                    off -= p->prefix_length;
                    bp -= p->prefix_length;
                    pt = p->prefix;
                } else {
                    pt = p->pattern;
                }

                found = 1;
                for (j = 0; j < p->length + p->prefix_length && off < length; j++, off++) {
                    if (bp[j] != pt[j]) {
                        found = 0;
                        break;
                    }
                }

                if (found && (p->boundary & BM_BOUNDARY_EOL)) {
                    if (off != length) {
                        p = p->next;
                        continue;
                    }
                }

                if (found && p->length + p->prefix_length == j) {
                    if (!offdata && (p->offset_min != CLI_OFF_ANY)) {
                        if (p->offdata[0] != CLI_OFF_ABSOLUTE) {
                            if (!info) {
                                p = p->next;
                                continue;
                            }
                            ret = cli_caloff(NULL, info, root->type, p->offdata, &off_min, &off_max);
                            if (ret != CL_SUCCESS) {
                                cli_errmsg("cli_bm_scanbuff: Can't calculate relative offset in signature for %s\n", p->virname);
                                return ret;
                            }
                        } else {
                            off_min = p->offset_min;
                            off_max = p->offset_max;
                        }
                        off = offset + i - p->prefix_length - BM_MIN_LENGTH + BM_BLOCK_SIZE;
                        if (off_min == CLI_OFF_NONE || off_max < off || off_min > off) {
                            p = p->next;
                            continue;
                        }
                    }

                    viruses_found += 1;
                    if (virname) {
                        *virname = p->virname;
                        if (ctx != NULL && SCAN_ALLMATCHES) {
                            ret = cli_append_virus(ctx, *virname);
                            if (ret == CL_CLEAN && viruses_found > 0) {
                                viruses_found -= 1;
                            }
                        }
                    }

                    if (patt)
                        *patt = p;

                    if (ctx != NULL && !SCAN_ALLMATCHES)
                        return CL_VIRUS;
                }
                p = p->next;
            }
            shift = 1;
        }

        if (offdata) {
            off = offset + i - BM_MIN_LENGTH + BM_BLOCK_SIZE;
            for (; offdata->pos < offdata->cnt && off >= offdata->offtab[offdata->pos]; offdata->pos++)
                ;
            if (offdata->pos == offdata->cnt || off >= offdata->offtab[offdata->pos]) {
                if (viruses_found > 0) {
                    return CL_VIRUS;
                }
                return CL_CLEAN;
            }
            i += offdata->offtab[offdata->pos] - off;
        } else {
            i += shift;
        }
    }

    if (viruses_found > 0) {
        return CL_VIRUS;
    }
    return CL_CLEAN;
}
