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 <stdio.h>
  34 #include <stdlib.h>
  35 #include <string.h>
  36
  37 #include "fstyp.h"
  38 #include "msdosfs.h"
  39
  40 #define LABEL_NO_NAME           "NO NAME    "
  41
  42 int
  43 fstyp_msdosfs(FILE *fp, char *label, size_t size)
  44 {
  45         FAT_BSBPB *pfat_bsbpb;
  46         FAT32_BSBPB *pfat32_bsbpb;
  47         FAT_DES *pfat_entry;
  48         uint8_t *sector0, *sector;
  49
  50         sector0 = NULL;
  51         sector = NULL;
  52
  53         /* Load 1st sector with boot sector and boot parameter block. */
  54         sector0 = (uint8_t *)read_buf(fp, 0, 512);
  55         if (sector0 == NULL)
  56                 return (1);
  57
  58         /* Check for the FAT boot sector signature. */
  59         if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
  60                 goto error;
  61         }
  62
  63         /*
  64          * Test if this is really a FAT volume and determine the FAT type.
  65          */
  66
  67         pfat_bsbpb = (FAT_BSBPB *)sector0;
  68         pfat32_bsbpb = (FAT32_BSBPB *)sector0;
  69
  70         if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
  71                 /*
  72                  * If the BPB_FATSz16 field is not zero and the string "FAT" is
  73                  * at the right place, this should be a FAT12 or FAT16 volume.
  74                  */
  75                 if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
  76                         goto error;
  77                 }
  78
  79                 /* A volume with no name should have "NO NAME    " as label. */
  80                 if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
  81                     sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
  82                         goto endofchecks;
  83                 }
  84                 strlcpy(label, pfat_bsbpb->BS_VolLab,
  85                     MIN(size, sizeof(pfat_bsbpb->BS_VolLab) + 1));
  86         } else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
  87                 uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
  88
  89                 /*
  90                  * If the BPB_FATSz32 field is not zero and the string "FAT" is
  91                  * at the right place, this should be a FAT32 volume.
  92                  */
  93                 if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
  94                         goto error;
  95                 }
  96
  97                 /*
  98                  * If the volume label is not "NO NAME    " we're done.
  99                  */
 100                 if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
 101                     sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
 102                         strlcpy(label, pfat32_bsbpb->BS_VolLab,
 103                             MIN(size, sizeof(pfat32_bsbpb->BS_VolLab) + 1));
 104                         goto endofchecks;
 105                 }
 106
 107                 /*
 108                  * If the volume label "NO NAME    " is in the boot sector, the
 109                  * label of FAT32 volumes may be stored as a special entry in
 110                  * the root directory.
 111                  */
 112                 fat_FirstDataSector =
 113                     UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
 114                     (pfat32_bsbpb->BPB_NumFATs *
 115                      UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
 116                 fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
 117
 118                 //    fat_FirstDataSector, fat_BytesPerSector);
 119
 120                 for (offset = fat_BytesPerSector * fat_FirstDataSector;;
 121                     offset += fat_BytesPerSector) {
 122                         sector = (uint8_t *)read_buf(fp, offset, fat_BytesPerSector);
 123                         if (sector == NULL)
 124                                 goto error;
 125
 126                         pfat_entry = (FAT_DES *)sector;
 127                         do {
 128                                 /* No more entries available. */
 129                                 if (pfat_entry->DIR_Name[0] == 0) {
 130                                         goto endofchecks;
 131                                 }
 132
 133                                 /* Skip empty or long name entries. */
 134                                 if (pfat_entry->DIR_Name[0] == 0xe5 ||
 135                                     (pfat_entry->DIR_Attr &
 136                                      FAT_DES_ATTR_LONG_NAME) ==
 137                                     FAT_DES_ATTR_LONG_NAME) {
 138                                         continue;
 139                                 }
 140
 141                                 /*
 142                                  * The name of the entry is the volume label if
 143                                  * ATTR_VOLUME_ID is set.
 144                                  */
 145                                 if (pfat_entry->DIR_Attr &
 146                                     FAT_DES_ATTR_VOLUME_ID) {
 147                                         strlcpy(label, pfat_entry->DIR_Name,
 148                                             MIN(size,
 149                                             sizeof(pfat_entry->DIR_Name) + 1));
 150                                         goto endofchecks;
 151                                 }
 152                         } while((uint8_t *)(++pfat_entry) <
 153                             (uint8_t *)(sector + fat_BytesPerSector));
 154                         free(sector);
 155                 }
 156         } else {
 157                 goto error;
 158         }
 159
 160 endofchecks:
 161         rtrim(label, size);
 162
 163         free(sector0);
 164         free(sector);
 165
 166         return (0);
 167
 168 error:
 169         free(sector0);
 170         free(sector);
 171
 172         return (1);
 173 }