usr.sbin/fstyp/msdosfs.c

   1 /*-
   2  * Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
   3  * Copyright (c) 2006 Tobias Reifenberger
   4  * Copyright (c) 2014 The FreeBSD Foundation
   5  * All rights reserved.
   6  *
   7  * This software was developed by Edward Tomasz Napierala under sponsorship
   8  * from the FreeBSD Foundation.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 __FBSDID("$FreeBSD$");
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <string.h>
  38
  39 #include "fstyp.h"
  40 #include "msdosfs.h"
  41
  42 #define LABEL_NO_NAME           "NO NAME    "
  43
  44 int
  45 fstyp_msdosfs(FILE *fp, char *label, size_t size)
  46 {
  47         FAT_BSBPB *pfat_bsbpb;
  48         FAT32_BSBPB *pfat32_bsbpb;
  49         FAT_DES *pfat_entry;
  50         uint8_t *sector0, *sector;
  51
  52         sector0 = NULL;
  53         sector = NULL;
  54
  55         /* Load 1st sector with boot sector and boot parameter block. */
  56         sector0 = (uint8_t *)read_buf(fp, 0, 512);
  57         if (sector0 == NULL)
  58                 return (1);
  59
  60         /* Check for the FAT boot sector signature. */
  61         if (sector0[510] != 0x55 || sector0[511] != 0xaa) {
  62                 goto error;
  63         }
  64
  65         /*
  66          * Test if this is really a FAT volume and determine the FAT type.
  67          */
  68
  69         pfat_bsbpb = (FAT_BSBPB *)sector0;
  70         pfat32_bsbpb = (FAT32_BSBPB *)sector0;
  71
  72         if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) {
  73                 /*
  74                  * If the BPB_FATSz16 field is not zero and the string "FAT" is
  75                  * at the right place, this should be a FAT12 or FAT16 volume.
  76                  */
  77                 if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
  78                         goto error;
  79                 }
  80
  81                 /* A volume with no name should have "NO NAME    " as label. */
  82                 if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME,
  83                     sizeof(pfat_bsbpb->BS_VolLab)) == 0) {
  84                         goto endofchecks;
  85                 }
  86                 strlcpy(label, pfat_bsbpb->BS_VolLab,
  87                     MIN(size, sizeof(pfat_bsbpb->BS_VolLab) + 1));
  88         } else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
  89                 uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
  90
  91                 /*
  92                  * If the BPB_FATSz32 field is not zero and the string "FAT" is
  93                  * at the right place, this should be a FAT32 volume.
  94                  */
  95                 if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
  96                         goto error;
  97                 }
  98
  99                 /*
 100                  * If the volume label is not "NO NAME    " we're done.
 101                  */
 102                 if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
 103                     sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
 104                         strlcpy(label, pfat32_bsbpb->BS_VolLab,
 105                             MIN(size, sizeof(pfat32_bsbpb->BS_VolLab) + 1));
 106                         goto endofchecks;
 107                 }
 108
 109                 /*
 110                  * If the volume label "NO NAME    " is in the boot sector, the
 111                  * label of FAT32 volumes may be stored as a special entry in
 112                  * the root directory.
 113                  */
 114                 fat_FirstDataSector =
 115                     UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
 116                     (pfat32_bsbpb->BPB_NumFATs *
 117                      UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
 118                 fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
 119
 120                 //    fat_FirstDataSector, fat_BytesPerSector);
 121
 122                 for (offset = fat_BytesPerSector * fat_FirstDataSector;;
 123                     offset += fat_BytesPerSector) {
 124                         sector = (uint8_t *)read_buf(fp, offset, fat_BytesPerSector);
 125                         if (sector == NULL)
 126                                 goto error;
 127
 128                         pfat_entry = (FAT_DES *)sector;
 129                         do {
 130                                 /* No more entries available. */
 131                                 if (pfat_entry->DIR_Name[0] == 0) {
 132                                         goto endofchecks;
 133                                 }
 134
 135                                 /* Skip empty or long name entries. */
 136                                 if (pfat_entry->DIR_Name[0] == 0xe5 ||
 137                                     (pfat_entry->DIR_Attr &
 138                                      FAT_DES_ATTR_LONG_NAME) ==
 139                                     FAT_DES_ATTR_LONG_NAME) {
 140                                         continue;
 141                                 }
 142
 143                                 /*
 144                                  * The name of the entry is the volume label if
 145                                  * ATTR_VOLUME_ID is set.
 146                                  */
 147                                 if (pfat_entry->DIR_Attr &
 148                                     FAT_DES_ATTR_VOLUME_ID) {
 149                                         strlcpy(label, pfat_entry->DIR_Name,
 150                                             MIN(size,
 151                                             sizeof(pfat_entry->DIR_Name) + 1));
 152                                         goto endofchecks;
 153                                 }
 154                         } while((uint8_t *)(++pfat_entry) <
 155                             (uint8_t *)(sector + fat_BytesPerSector));
 156                         free(sector);
 157                 }
 158         } else {
 159                 goto error;
 160         }
 161
 162 endofchecks:
 163         rtrim(label, size);
 164
 165         free(sector0);
 166         free(sector);
 167
 168         return (0);
 169
 170 error:
 171         free(sector0);
 172         free(sector);
 173
 174         return (1);
 175 }