/*
 *  Copyright (C) 2013-2020 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
 *  Copyright (C) 2008-2013 Sourcefire, Inc.
 *
 *  Authors: Alberto Wu
 *
 *  Acknowledgements: Written from scratch based on specs from PKWARE:
 *                    http://www.pkware.com/documents/casestudies/APPNOTE.TXT
 *
 *  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.
 */

/*
 * Written from scratch based on specs from PKWARE:
 * see www.pkware.com/documents/casestudies/APPNOTE.TXT
 *
 * To the best of my knowledge, it's patent free:
 * http://www.unisys.com/about__unisys/lzw
*/

/* To Cami and Dario, the only lawyers I can stand */

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

#if HAVE_STRING_H
#include <string.h>
#endif

#include "clamav.h"
#include "explode.h"
#include "others.h"

/* NOTE: sorting algo must be stable! */
static void bs(uint8_t *k, uint8_t *v, unsigned int elements)
{
    uint8_t tmp;
    unsigned int i = 0, l = 0, stop = 0, r = elements;

    while (!stop) {
        stop = 1;
        for (; i < r; i++) {
            if (v[k[i]] > v[k[i + 1]]) {
                tmp      = k[i];
                k[i]     = k[i + 1];
                k[i + 1] = tmp;
                stop     = 0;
            }
        }
        if (stop) break;
        r--;
        i--;
        for (; i > l; i--) {
            if (v[k[i]] < v[k[i - 1]]) {
                tmp      = k[i];
                k[i]     = k[i - 1];
                k[i - 1] = tmp;
                stop     = 0;
            }
        }
        l++;
        i++;
    }
}

static int unpack_tree(struct xplstate *X, uint32_t *tree, unsigned int expected)
{
    uint8_t temptree[256], order[256], *ttree = temptree;
    uint8_t *cur = X->window;
    uint8_t packsz;
    unsigned int i;
    uint16_t code = 0, codeinc = 0, lastlen = 0;

    packsz = *cur++;

    for (i = 0; i < expected; i++) order[i] = i;

    i = expected;

    do {
        uint8_t values, len;
        values = *cur++;
        len    = (values & 15) + 1;
        values = (values >> 4) + 1;
        if (values > i) return 1;
        i -= values;
        while (values--)
            *ttree++ = len;
    } while (packsz--);

    if (i) return 1;

    bs(order, temptree, expected - 1);

    i = expected - 1;
    do {
        code = code + codeinc;
        if (temptree[order[i]] != lastlen) {
            lastlen = temptree[order[i]];
            codeinc = 1 << (16 - lastlen);
        }
        tree[order[i]] = code | ((uint32_t)lastlen << 16);
    } while (i--);

    return 0;
}

/* bit lame of a lookup, but prolly not worth optimizing */
static int lookup_tree(uint32_t *tree, unsigned int size, uint16_t code, uint8_t len)
{
    uint32_t lookup = ((uint32_t)(len + 1)) << 16 | code;
    unsigned int i;
    for (i = 0; i < size; i++)
        if (tree[i] == lookup) return i;
    return -1;
}

int explode_init(struct xplstate *X, uint16_t flags)
{
    X->bits = X->cur = 0;
    if (flags & 2) {
        X->largewin = 1;
        X->mask     = 0x1fff;
    } else {
        X->largewin = 0;
        X->mask     = 0xfff;
    }
    if (flags & 4) {
        X->state    = GRABLITS;
        X->litcodes = 1;
        X->minlen   = 3;
    } else {
        X->state    = GRABLENS;
        X->litcodes = 0;
        X->minlen   = 2;
    }
    X->got = 0;
    return EXPLODE_OK;
}

#define GETBIT                                     \
    if (X->bits) {                                 \
        X->bits--;                                 \
        val = X->bitmap & 1;                       \
        X->bitmap >>= 1;                           \
    } else {                                       \
        if (!X->avail_in) return EXPLODE_EBUFF;    \
        if (X->avail_in >= 4) {                    \
            X->bitmap = cli_readint32(X->next_in); \
            X->bits   = 31;                        \
            X->next_in += 4;                       \
            X->avail_in -= 4;                      \
        } else {                                   \
            X->bitmap = *X->next_in;               \
            X->bits   = 7;                         \
            X->next_in++;                          \
            X->avail_in--;                         \
        }                                          \
        val = X->bitmap & 1;                       \
        X->bitmap >>= 1;                           \
    }

#define GETBITS(NUM)                                                      \
    if (X->bits >= (NUM)) {                                               \
        val = X->bitmap & ((1 << (NUM)) - 1);                             \
        X->bitmap >>= (NUM);                                              \
        X->bits -= (NUM);                                                 \
    } else {                                                              \
        if (X->avail_in * 8 + X->bits < (NUM)) return EXPLODE_EBUFF;      \
        val = X->bitmap;                                                  \
        if (X->avail_in >= 4) {                                           \
            X->bitmap = cli_readint32(X->next_in);                        \
            X->next_in += 4;                                              \
            X->avail_in -= 4;                                             \
            val |= (X->bitmap & ((1 << ((NUM)-X->bits)) - 1)) << X->bits; \
            X->bitmap >>= (NUM)-X->bits;                                  \
            X->bits = 32 - ((NUM)-X->bits);                               \
        } else {                                                          \
            X->bitmap = *X->next_in;                                      \
            X->next_in++;                                                 \
            X->avail_in--;                                                \
            val |= (X->bitmap & ((1 << ((NUM)-X->bits)) - 1)) << X->bits; \
            X->bitmap >>= (NUM)-X->bits;                                  \
            X->bits = 8 - ((NUM)-X->bits);                                \
        }                                                                 \
    }

#define GETCODES(CASE, WHICH, HOWMANY)                                        \
    case CASE: {                                                              \
        if (!X->avail_in) return EXPLODE_EBUFF;                               \
        if (!X->got)                                                          \
            need = *X->next_in;                                               \
        else                                                                  \
            need = X->window[0];                                              \
        if (need > HOWMANY - 1) return EXPLODE_ESTREAM; /* too many codes */  \
        need = need + 2 - X->got;                       /* bytes remaining */ \
        if (need > X->avail_in) {                       /* if not enuff */    \
            /* just copy what's avail... */                                   \
            memcpy(&X->window[X->got], X->next_in, X->avail_in);              \
            X->got += X->avail_in;                                            \
            X->next_in += X->avail_in;                                        \
            X->avail_in = 0;                                                  \
            return EXPLODE_EBUFF; /* ...and beg for more */                   \
        }                                                                     \
        /* else fetch what's needed */                                        \
        memcpy(&X->window[X->got], X->next_in, need);                         \
        X->avail_in -= need;                                                  \
        X->next_in += need;                                                   \
        if (unpack_tree(X, X->WHICH, HOWMANY)) return EXPLODE_ESTREAM;        \
        /* and move on */                                                     \
        X->got = 0;                                                           \
        X->state++;                                                           \
    }

#define SETCASE(CASE)         \
    X->state = (CASE);        \
    case (CASE): { /* FAKE */ \
    }

int explode(struct xplstate *X)
{
    unsigned int val, need;
    int temp = -1;

    switch (X->state) {
        /* grab compressed coded literals, if present */
        GETCODES(GRABLITS, lit_tree, 256);
        /* grab compressed coded lens */
        GETCODES(GRABLENS, len_tree, 64);
        /* grab compressed coded dists */
        GETCODES(GRABDISTS, dist_tree, 64);

        case EXPLODE:
            while (X->avail_in || X->bits) {
                GETBIT; /* can't fail */
                if (val) {
                    if (X->litcodes) {
                        X->backsize = 0;
                        X->state    = EXPLODE_LITCODES;
                        for (X->got = 0; X->got <= 15; X->got++) {
                            case EXPLODE_LITCODES:
                                GETBIT;
                                X->backsize |= val << (15 - X->got);
                                if ((temp = lookup_tree(X->lit_tree, 256, X->backsize, X->got)) != -1) break;
                        }
                        if (temp == -1) return EXPLODE_ESTREAM;
                        X->got = temp;
                    } else {
                        SETCASE(EXPLODE_LITS);
                        GETBITS(8);
                        X->got = val;
                    }
                    SETCASE(EXPLODE_WBYTE);
                    if (!X->avail_out) return EXPLODE_EBUFF;
                    X->avail_out--;
                    *X->next_out = X->window[X->cur & X->mask] = X->got;
                    X->cur++;
                    X->next_out++;
                } else {
                    SETCASE(EXPLODE_BASEDIST);
                    GETBITS(6u + X->largewin);
                    X->backbytes = val;
                    X->backsize  = 0;
                    X->state     = EXPLODE_DECODEDISTS;
                    for (X->got = 0; X->got <= 15; X->got++) {
                        case EXPLODE_DECODEDISTS:
                            GETBIT;
                            X->backsize |= val << (15 - X->got);
                            if ((temp = lookup_tree(X->dist_tree, 64, X->backsize, X->got)) != -1) break;
                    }
                    if (temp == -1) return EXPLODE_ESTREAM;
                    X->backbytes |= temp << (6 + X->largewin);
                    X->backbytes++;
                    X->backsize = 0;
                    X->state    = EXPLODE_DECODELENS;
                    for (X->got = 0; X->got <= 15; X->got++) {
                        case EXPLODE_DECODELENS:
                            GETBIT;
                            X->backsize |= val << (15 - X->got);
                            if ((temp = lookup_tree(X->len_tree, 64, X->backsize, X->got)) != -1) break;
                    }
                    if (temp == -1) return EXPLODE_ESTREAM;

                    if (temp == 63) {
                        SETCASE(EXPLODE_DECODEEXTRA);
                        GETBITS(8);
                        temp = 63 + val;
                    }
                    X->backsize = temp + X->minlen;
                    X->state    = EXPLODE_BACKCOPY;
                    while (X->backsize--) {
                        case EXPLODE_BACKCOPY:
                            if (!X->avail_out) return EXPLODE_EBUFF;
                            X->avail_out--;
                            if (X->cur >= X->backbytes)
                                *X->next_out = X->window[X->cur & X->mask] = X->window[(X->cur - X->backbytes) & X->mask];
                            else
                                *X->next_out = X->window[X->cur & X->mask] = 0;
                            X->cur++;
                            X->next_out++;
                    }
                }
                X->state = EXPLODE;
            }
    }
    return EXPLODE_EBUFF;
}

void explode_shutdown(void) {}
