clamav/libclamav/binhex.c

/*
 *  Copyright (C) 2013-2020 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
 *  Copyright (C) 2010-2013 Sourcefire, Inc.
 *
 *  Authors: aCaB <acab@clamav.net>
 *
 *  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 <string.h>

#include "scanners.h"
#include "others.h"
#include "clamav.h"
#include "fmap.h"
#include "binhex.h"

// clang-format off
static const uint8_t hqxtbl[] = {
    /*           00   01   02   03   04   05   06   07   08   09   0a   0b   0c   0d   0e   0f */
    /* 00-0f */	0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
    /* 10-1f */	0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
    /* 20-2f */	0xff,0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0a,0x0b,0x0c,0xff,0xff,
    /* 30-3f */	0x0d,0x0e,0x0f,0x10,0x11,0x12,0x13,0xff,0x14,0x15,0xff,0xff,0xff,0xff,0xff,0xff,
    /* 40-4f */	0x16,0x17,0x18,0x19,0x1a,0x1b,0x1c,0x1d,0x1e,0x1f,0x20,0x21,0x22,0x23,0x24,0xff,
    /* 50-5f */	0x25,0x26,0x27,0x28,0x29,0x2a,0x2b,0xff,0x2c,0x2d,0x2e,0x2f,0xff,0xff,0xff,0xff,
    /* 60-6f */	0x30,0x31,0x32,0x33,0x34,0x35,0x36,0xff,0x37,0x38,0x39,0x3a,0x3b,0x3c,0xff,0xff,
    /* 70-7f */	0x3d,0x3e,0x3f,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff
};
// clang-format on

#define BH_FLUSH_SZ (BUFSIZ - 256)

int cli_binhex(cli_ctx *ctx)
{
    fmap_t *map            = *ctx->fmap;
    const uint8_t *encoded = NULL;
    uint8_t decoded[BUFSIZ], spare_bits = 0, last_byte = 0, this_byte = 0, offset = 0;
    size_t enc_done = 0, enc_todo = map->len;
    unsigned int dec_done = 0, chunksz = 0, chunkoff = 0;
    uint32_t datalen = 0, reslen = 0;
    int in_data = 0, in_run = 0, datafd, resfd, ret = CL_CLEAN;
    enum binhex_phase { IN_BANNER,
                        IN_HEADER,
                        IN_DATA,
                        IN_LIMBO1,
                        IN_LIMBO2,
                        IN_RES } write_phase = IN_BANNER;
    char *dname, *rname;

    cli_dbgmsg("in cli_binhex\n");
    if (!map->len) return CL_CLEAN;

    if ((ret = cli_gentempfd(ctx->sub_tmpdir, &dname, &datafd)) != CL_SUCCESS)
        return ret;

    if ((ret = cli_gentempfd(ctx->sub_tmpdir, &rname, &resfd)) != CL_SUCCESS) {
        close(datafd);
        if (cli_unlink(dname)) ret = CL_EUNLINK;
        free(dname);
        return ret;
    }

    memset(decoded, 0, 24);

    while (1) {
        uint8_t b;
        if (!enc_todo || dec_done >= BH_FLUSH_SZ) {
            if (write_phase == IN_HEADER) {
                uint32_t namelen = (uint32_t)decoded[0], hdrlen = 1 + namelen + 1 + 4 + 4 + 2;
                if (!dec_done) {
                    cli_dbgmsg("cli_binhex: file is empty\n");
                    break;
                }
                datalen = (decoded[hdrlen] << 24) | (decoded[hdrlen + 1] << 16) | (decoded[hdrlen + 2] << 8) | decoded[hdrlen + 3];
                hdrlen += 4;
                reslen = (decoded[hdrlen] << 24) | (decoded[hdrlen + 1] << 16) | (decoded[hdrlen + 2] << 8) | decoded[hdrlen + 3];
                hdrlen += 4 + 2;
                decoded[namelen + 1] = 0;
                if (dec_done <= hdrlen) {
                    cli_dbgmsg("cli_binhex: file too short for header\n");
                    break;
                }
                if ((ret = cli_checklimits("cli_binhex(data)", ctx, datalen, 0, 0)) != CL_CLEAN)
                    break;
                if (cli_checklimits("cli_binhex(resources)", ctx, reslen, 0, 0) != CL_CLEAN)
                    reslen = 0;
                cli_dbgmsg("cli_binhex: decoding '%s' - %u bytes of data to %s - %u bytes or resources to %s\n", decoded + 1, datalen, dname, reslen, rname);
                memmove(decoded, &decoded[hdrlen], dec_done - hdrlen);
                dec_done -= hdrlen;
                write_phase++;
            }
            if (dec_done && write_phase == IN_DATA) {
                unsigned int todo = MIN(dec_done, datalen);
                datalen -= todo;
                dec_done -= todo;
                if (cli_writen(datafd, decoded, todo) != todo) {
                    ret = CL_EWRITE;
                    break;
                }
                if (!datalen) {
                    write_phase++;
                    if (lseek(datafd, 0, SEEK_SET) == -1) {
                        cli_dbgmsg("cli_binhex: call to lseek() has failed\n");
                        ret = CL_ESEEK;
                        break;
                    }
                    ret = cli_magic_scan_desc(datafd, dname, ctx, NULL);
                    if (ret == CL_VIRUS) break;
                }
                if (dec_done)
                    memmove(decoded, &decoded[todo], dec_done);
            }
            if (dec_done && write_phase == IN_LIMBO1) {
                if (dec_done > 1) {
                    if (reslen < 5) {
                        cli_dbgmsg("cli_binhex: skipping resources (too small)\n");
                        break;
                    }
                    dec_done -= 2;
                    write_phase += 2;
                    if (dec_done)
                        memmove(decoded, &decoded[2], dec_done);
                } else {
                    dec_done--;
                    write_phase++;
                    if (dec_done)
                        memmove(decoded, &decoded[1], dec_done);
                }
            }
            if (dec_done && write_phase == IN_LIMBO2) {
                if (reslen < 5) {
                    cli_dbgmsg("cli_binhex: skipping resources (too small)\n");
                    break;
                }
                write_phase++;
                if (--dec_done)
                    memmove(decoded, &decoded[1], dec_done);
            }
            if (dec_done && write_phase == IN_RES) {
                unsigned int todo = MIN(dec_done, reslen);
                reslen -= todo;
                dec_done -= todo;
                if (cli_writen(resfd, decoded, todo) != todo) {
                    ret = CL_EWRITE;
                    break;
                }
                if (!reslen) {
                    if (lseek(resfd, 0, SEEK_SET) == -1) {
                        cli_dbgmsg("cli_binhex: call to lseek() has failed\n");
                        ret = CL_ESEEK;
                        break;
                    }
                    ret = cli_magic_scan_desc(resfd, rname, ctx, NULL);
                    break;
                }
            }
            if (!enc_todo) {
                if (write_phase == IN_DATA) {
                    cli_dbgmsg("cli_binhex: scanning partially extracted data fork\n");
                    if (lseek(datafd, 0, SEEK_SET) == -1) {
                        cli_dbgmsg("cli_binhex: call to lseek() has failed\n");
                        ret = CL_ESEEK;
                        break;
                    }
                    ret = cli_magic_scan_desc(datafd, dname, ctx, NULL);
                } else if (write_phase == IN_RES) {
                    cli_dbgmsg("cli_binhex: scanning partially extracted resource fork\n");
                    if (lseek(resfd, 0, SEEK_SET) == -1) {
                        cli_dbgmsg("cli_binhex: call to lseek() has failed\n");
                        ret = CL_ESEEK;
                        break;
                    }
                    ret = cli_magic_scan_desc(resfd, rname, ctx, NULL);
                }
                break;
            }
        }

        // 'chunksz' must be 0 the first iteration,
        // so that 'encoded' will be initialized before first dereference.
        if (!chunksz) {
            chunksz = MIN(enc_todo, map->pgsz);
            encoded = fmap_need_off_once(map, enc_done, chunksz);
            if (!encoded) {
                ret = CL_EREAD;
                break;
            }
            chunkoff = 0;
        }
        chunksz--;

        b = encoded[chunkoff++];
        enc_done++;
        enc_todo--;

        if ((char)b == '\r' || (char)b == '\n') {
            in_data = 1;
            continue;
        }
        if (!in_data) continue;
        if (write_phase == IN_BANNER) {
            if ((char)b != ':') {
                cli_dbgmsg("cli_binhex: broken file (missing stream start identifier)\n");
                break;
            }
            write_phase++;
        }
        if ((char)b == ':')
            continue;
        if (b > 0x7f || (b = hqxtbl[b]) == 0xff) {
            cli_dbgmsg("cli_binhex: Invalid character (%02x)\n", encoded[chunkoff - 1]);
            break;
        }
        switch ((offset++) & 3) { /* 6 bits per char */
            case 0:               /* left-6h */
                spare_bits = b << 2;
                continue;
            case 1: /* left-2l + middle-4h */
                this_byte  = spare_bits | (b >> 4);
                spare_bits = b << 4;
                break;
            case 2: /* middle-4l + right-2h */
                this_byte  = spare_bits | (b >> 2);
                spare_bits = b << 6;
                break;
            case 3: /* right-6l */
                this_byte = spare_bits | b;
        }

        if (in_run) {
            in_run = 0;
            if (!this_byte)
                this_byte = 0x90;
            else {
                while (--this_byte)
                    decoded[dec_done++] = last_byte;
                continue;
            }
        } else if (this_byte == 0x90) {
            in_run = 1;
            continue;
        }
        decoded[dec_done++] = this_byte;
        last_byte           = this_byte;
    }

    close(datafd);
    close(resfd);
    if (!ctx->engine->keeptmp) {
        if (cli_unlink(dname) && ret != CL_VIRUS) ret = CL_EUNLINK;
        if (cli_unlink(rname) && ret != CL_VIRUS) ret = CL_EUNLINK;
    }
    free(dname);
    free(rname);
    return ret;
}