usr.sbin/fstyp/msdosfs.c

   1 /*-
   2  * Copyright (c) 2016 The DragonFly Project
   3  * Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
   4  * Copyright (c) 2006 Tobias Reifenberger
   5  * Copyright (c) 2014 The FreeBSD Foundation
   6  * All rights reserved.
   7  *
   8  * This software was developed by Edward Tomasz Napierala under sponsorship
   9  * from the FreeBSD Foundation.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <sys/param.h>
  34 #include <stdio.h>
  35 #include <stdlib.h>
  36 #include <string.h>
  37
  38 #include "fstyp.h"
  39 #include "msdosfs.h"
  40
  41 #define LABEL_NO_NAME           "NO NAME    "
  42
  43 int
  44 fstyp_msdosfs(FILE *fp, char *label, size_t size)
  45 {
  46         FAT_BSBPB *pfat_bsbpb;
  47         FAT32_BSBPB *pfat32_bsbpb;
  48         FAT_DES *pfat_entry;
  49         uint8_t *sector0, *sector;
  50
  51         sector0 = NULL;
  52         sector = NULL;
  53
  54         /* Load 1st sector with boot sector and boot parameter block. */
  55         sector0 = (uint8_t *)read_buf(fp, 0, 512);
  56         if (sector0 == NULL)
  57                 return (1);
  58
  59         /* Check for the FAT boot sector signature. */
  60         if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
  61                 goto error;
  62         }
  63
  64         /*
  65          * Test if this is really a FAT volume and determine the FAT type.
  66          */
  67
  68         pfat_bsbpb = (FAT_BSBPB *)sector0;
  69         pfat32_bsbpb = (FAT32_BSBPB *)sector0;
  70
  71         if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
  72                 /*
  73                  * If the BPB_FATSz16 field is not zero and the string "FAT" is
  74                  * at the right place, this should be a FAT12 or FAT16 volume.
  75                  */
  76                 if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
  77                         goto error;
  78                 }
  79
  80                 /* A volume with no name should have "NO NAME    " as label. */
  81                 if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
  82                     sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
  83                         goto endofchecks;
  84                 }
  85                 strlcpy(label, pfat_bsbpb->BS_VolLab,
  86                     MIN(size, sizeof(pfat_bsbpb->BS_VolLab) + 1));
  87         } else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
  88                 uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
  89
  90                 /*
  91                  * If the BPB_FATSz32 field is not zero and the string "FAT" is
  92                  * at the right place, this should be a FAT32 volume.
  93                  */
  94                 if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
  95                         goto error;
  96                 }
  97
  98                 /*
  99                  * If the volume label is not "NO NAME    " we're done.
 100                  */
 101                 if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
 102                     sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
 103                         strlcpy(label, pfat32_bsbpb->BS_VolLab,
 104                             MIN(size, sizeof(pfat32_bsbpb->BS_VolLab) + 1));
 105                         goto endofchecks;
 106                 }
 107
 108                 /*
 109                  * If the volume label "NO NAME    " is in the boot sector, the
 110                  * label of FAT32 volumes may be stored as a special entry in
 111                  * the root directory.
 112                  */
 113                 fat_FirstDataSector =
 114                     UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
 115                     (pfat32_bsbpb->BPB_NumFATs *
 116                      UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
 117                 fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
 118
 119                 //    fat_FirstDataSector, fat_BytesPerSector);
 120
 121                 for (offset = fat_BytesPerSector * fat_FirstDataSector;;
 122                     offset += fat_BytesPerSector) {
 123                         sector = (uint8_t *)read_buf(fp, offset, fat_BytesPerSector);
 124                         if (sector == NULL)
 125                                 goto error;
 126
 127                         pfat_entry = (FAT_DES *)sector;
 128                         do {
 129                                 /* No more entries available. */
 130                                 if (pfat_entry->DIR_Name[0] == 0) {
 131                                         goto endofchecks;
 132                                 }
 133
 134                                 /* Skip empty or long name entries. */
 135                                 if (pfat_entry->DIR_Name[0] == 0xe5 ||
 136                                     (pfat_entry->DIR_Attr &
 137                                      FAT_DES_ATTR_LONG_NAME) ==
 138                                     FAT_DES_ATTR_LONG_NAME) {
 139                                         continue;
 140                                 }
 141
 142                                 /*
 143                                  * The name of the entry is the volume label if
 144                                  * ATTR_VOLUME_ID is set.
 145                                  */
 146                                 if (pfat_entry->DIR_Attr &
 147                                     FAT_DES_ATTR_VOLUME_ID) {
 148                                         strlcpy(label, pfat_entry->DIR_Name,
 149                                             MIN(size,
 150                                             sizeof(pfat_entry->DIR_Name) + 1));
 151                                         goto endofchecks;
 152                                 }
 153                         } while((uint8_t *)(++pfat_entry) <
 154                             (uint8_t *)(sector + fat_BytesPerSector));
 155                         free(sector);
 156                 }
 157         } else {
 158                 goto error;
 159         }
 160
 161 endofchecks:
 162         rtrim(label, size);
 163
 164         free(sector0);
 165         free(sector);
 166
 167         return (0);
 168
 169 error:
 170         free(sector0);
 171         free(sector);
 172
 173         return (1);
 174 }