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, const char *devpath)
  45 {
  46         FAT_BSBPB *pfat_bsbpb;
  47         FAT32_BSBPB *pfat32_bsbpb;
  48         FAT_DES *pfat_entry;
  49         uint8_t *sector0, *sector;
  50         size_t copysize;
  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                 copysize = MIN(size - 1, sizeof(pfat_bsbpb->BS_VolLab));
  87                 memcpy(label, pfat_bsbpb->BS_VolLab, copysize);
  88                 label[copysize] = '\0';
  89         } else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) {
  90                 uint32_t fat_FirstDataSector, fat_BytesPerSector, offset;
  91
  92                 /*
  93                  * If the BPB_FATSz32 field is not zero and the string "FAT" is
  94                  * at the right place, this should be a FAT32 volume.
  95                  */
  96                 if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) {
  97                         goto error;
  98                 }
  99
 100                 /*
 101                  * If the volume label is not "NO NAME    " we're done.
 102                  */
 103                 if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME,
 104                     sizeof(pfat32_bsbpb->BS_VolLab)) != 0) {
 105                         copysize = MIN(size - 1,
 106                             sizeof(pfat32_bsbpb->BS_VolLab));
 107                         memcpy(label, pfat32_bsbpb->BS_VolLab, copysize);
 108                         label[copysize] = '\0';
 109                         goto endofchecks;
 110                 }
 111
 112                 /*
 113                  * If the volume label "NO NAME    " is in the boot sector, the
 114                  * label of FAT32 volumes may be stored as a special entry in
 115                  * the root directory.
 116                  */
 117                 fat_FirstDataSector =
 118                     UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) +
 119                     (pfat32_bsbpb->BPB_NumFATs *
 120                      UINT32BYTES(pfat32_bsbpb->BPB_FATSz32));
 121                 fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec);
 122
 123                 //    fat_FirstDataSector, fat_BytesPerSector);
 124
 125                 for (offset = fat_BytesPerSector * fat_FirstDataSector;;
 126                     offset += fat_BytesPerSector) {
 127                         sector = (uint8_t *)read_buf(fp, offset, fat_BytesPerSector);
 128                         if (sector == NULL)
 129                                 goto error;
 130
 131                         pfat_entry = (FAT_DES *)sector;
 132                         do {
 133                                 /* No more entries available. */
 134                                 if (pfat_entry->DIR_Name[0] == 0) {
 135                                         goto endofchecks;
 136                                 }
 137
 138                                 /* Skip empty or long name entries. */
 139                                 if (pfat_entry->DIR_Name[0] == 0xe5 ||
 140                                     (pfat_entry->DIR_Attr &
 141                                      FAT_DES_ATTR_LONG_NAME) ==
 142                                     FAT_DES_ATTR_LONG_NAME) {
 143                                         continue;
 144                                 }
 145
 146                                 /*
 147                                  * The name of the entry is the volume label if
 148                                  * ATTR_VOLUME_ID is set.
 149                                  */
 150                                 if (pfat_entry->DIR_Attr &
 151                                     FAT_DES_ATTR_VOLUME_ID) {
 152                                         copysize = MIN(size - 1,
 153                                             sizeof(pfat_entry->DIR_Name));
 154                                         memcpy(label, pfat_entry->DIR_Name,
 155                                             copysize);
 156                                         label[copysize] = '\0';
 157                                         goto endofchecks;
 158                                 }
 159                         } while((uint8_t *)(++pfat_entry) <
 160                             (uint8_t *)(sector + fat_BytesPerSector));
 161                         free(sector);
 162                 }
 163         } else {
 164                 goto error;
 165         }
 166
 167 endofchecks:
 168         rtrim(label, size);
 169
 170         free(sector0);
 171         free(sector);
 172
 173         return (0);
 174
 175 error:
 176         free(sector0);
 177         free(sector);
 178
 179         return (1);
 180 }