/*      $NetBSD: msdosfs.c,v 1.1 2018/01/09 03:31:15 christos Exp $     */

/*-
* Copyright (c) 2017 The NetBSD Foundation, Inc.
* Copyright (c) 2016 The DragonFly Project
* Copyright (c) 2004 Pawel Jakub Dawidek <[email protected]>
* Copyright (c) 2006 Tobias Reifenberger
* Copyright (c) 2014 The FreeBSD Foundation
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Tomohiro Kusumi <[email protected]>.
*
* This software was developed by Edward Tomasz Napierala under sponsorship
* from the FreeBSD Foundation.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: msdosfs.c,v 1.1 2018/01/09 03:31:15 christos Exp $");

#include <sys/param.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "fstyp.h"
#include "msdosfs.h"

#define LABEL_NO_NAME           "NO NAME    "

int
fstyp_msdosfs(FILE *fp, char *label, size_t size)
{
       FAT_BSBPB *pfat_bsbpb;
       FAT32_BSBPB *pfat32_bsbpb;
       FAT_DES *pfat_entry;
       uint8_t *sector0, *sector;

       sector0 = NULL;
       sector = NULL;

       /* Load 1st sector with boot sector and boot parameter block. */
       sector0 = read_buf(fp, 0, 512);
       if (sector0 == NULL)
               return 1;

       /* Check for the FAT boot sector signature. */
       if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
               goto error;
       }

       /*
        * Test if this is really a FAT volume and determine the FAT type.
        */

       pfat_bsbpb = (FAT_BSBPB *)sector0;
       pfat32_bsbpb = (FAT32_BSBPB *)sector0;

       if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
               /*
                * If the BPB_FATSz16 field is not zero and the string "FAT" is
                * at the right place, this should be a FAT12 or FAT16 volume.
                */
               if (strncmp((char*)pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
                       goto error;
               }

               /* A volume with no name should have "NO NAME    " as label. */
               if (strncmp((char*)pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
                   sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
                       goto endofchecks;
               }
               strlcpy(label, (char*)pfat_bsbpb->BS_VolLab,
                   MIN(size, sizeof(pfat_bsbpb->BS_VolLab) + 1));
       } else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
               uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;

               /*
                * If the BPB_FATSz32 field is not zero and the string "FAT" is
                * at the right place, this should be a FAT32 volume.
                */
               if (strncmp((char*)pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0)
               {
                       goto error;
               }

               /*
                * If the volume label is not "NO NAME    " we're done.
                */
               if (strncmp((char*)pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
                   sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
                       strlcpy(label, (char*)pfat32_bsbpb->BS_VolLab,
                           MIN(size, sizeof(pfat32_bsbpb->BS_VolLab) + 1));
                       goto endofchecks;
               }

               /*
                * If the volume label "NO NAME    " is in the boot sector, the
                * label of FAT32 volumes may be stored as a special entry in
                * the root directory.
                */
               fat_FirstDataSector =
                   UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
                   (pfat32_bsbpb->BPB_NumFATs *
                    UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
               fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);

               //    fat_FirstDataSector, fat_BytesPerSector);

               for (offset = fat_BytesPerSector * fat_FirstDataSector;;
                   offset += fat_BytesPerSector) {
                       sector = read_buf(fp, offset, fat_BytesPerSector);
                       if (sector == NULL)
                               goto error;

                       pfat_entry = (FAT_DES *)sector;
                       do {
                               /* No more entries available. */
                               if (pfat_entry->DIR_Name[0] == 0) {
                                       goto endofchecks;
                               }

                               /* Skip empty or long name entries. */
                               if (pfat_entry->DIR_Name[0] == 0xe5 ||
                                   (pfat_entry->DIR_Attr &
                                    FAT_DES_ATTR_LONG_NAME) ==
                                   FAT_DES_ATTR_LONG_NAME) {
                                       continue;
                               }

                               /*
                                * The name of the entry is the volume label if
                                * ATTR_VOLUME_ID is set.
                                */
                               if (pfat_entry->DIR_Attr &
                                   FAT_DES_ATTR_VOLUME_ID) {
                                       strlcpy(label, (char*)pfat_entry->DIR_Name,
                                           MIN(size,
                                           sizeof(pfat_entry->DIR_Name) + 1));
                                       goto endofchecks;
                               }
                       } while((uint8_t *)(++pfat_entry) <
                           (uint8_t *)(sector + fat_BytesPerSector));
                       free(sector);
               }
       } else {
               goto error;
       }

endofchecks:
       rtrim(label, size);

       free(sector0);
       free(sector);

       return (0);

error:
       free(sector0);
       free(sector);

       return (1);
}

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