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 #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 /* 43 * XXX the signature 0x55 0xAA as the last two bytes of 512 is not required 44 * by specifications, but was historically required by fstyp. This check 45 * should be removed, with a more comprehensive BPB validation instead. 46 */ 47 static bool 48 check_signature(uint8_t sector0[512]) 49 { 50 /* Check for the FAT boot sector signature. */ 51 if (sector0[510] == 0x55 && sector0[511] == 0xaa) 52 return (true); 53 /* Special case for Raspberry Pi Pico bootloader. */ 54 if (sector0[510] == 0 && sector0[511] == 0 && 55 sector0[0] == 0xeb && sector0[1] == 0x3c && sector0[2] == 0x90) 56 return (true); 57 return (false); 58 } 59 60 int 61 fstyp_msdosfs(FILE *fp, char *label, size_t size) 62 { 63 FAT_BSBPB *pfat_bsbpb; 64 FAT32_BSBPB *pfat32_bsbpb; 65 FAT_DES *pfat_entry; 66 uint8_t *sector0, *sector; 67 size_t copysize; 68 69 sector0 = NULL; 70 sector = NULL; 71 72 /* Load 1st sector with boot sector and boot parameter block. */ 73 sector0 = (uint8_t *)read_buf(fp, 0, 512); 74 if (sector0 == NULL) 75 return (1); 76 77 if (!check_signature(sector0)) { 78 goto error; 79 } 80 81 /* 82 * Test if this is really a FAT volume and determine the FAT type. 83 */ 84 85 pfat_bsbpb = (FAT_BSBPB *)sector0; 86 pfat32_bsbpb = (FAT32_BSBPB *)sector0; 87 88 if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) { 89 /* 90 * If the BPB_FATSz16 field is not zero and the string "FAT" is 91 * at the right place, this should be a FAT12 or FAT16 volume. 92 */ 93 if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) { 94 goto error; 95 } 96 97 /* A volume with no name should have "NO NAME " as label. */ 98 if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME, 99 sizeof(pfat_bsbpb->BS_VolLab)) == 0) { 100 goto endofchecks; 101 } 102 copysize = MIN(size - 1, sizeof(pfat_bsbpb->BS_VolLab)); 103 memcpy(label, pfat_bsbpb->BS_VolLab, copysize); 104 label[copysize] = '\0'; 105 } else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) { 106 uint32_t fat_FirstDataSector, fat_BytesPerSector, offset; 107 108 /* 109 * If the BPB_FATSz32 field is not zero and the string "FAT" is 110 * at the right place, this should be a FAT32 volume. 111 */ 112 if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) { 113 goto error; 114 } 115 116 /* 117 * If the volume label is not "NO NAME " we're done. 118 */ 119 if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME, 120 sizeof(pfat32_bsbpb->BS_VolLab)) != 0) { 121 copysize = MIN(size - 1, 122 sizeof(pfat32_bsbpb->BS_VolLab)); 123 memcpy(label, pfat32_bsbpb->BS_VolLab, copysize); 124 label[copysize] = '\0'; 125 goto endofchecks; 126 } 127 128 /* 129 * If the volume label "NO NAME " is in the boot sector, the 130 * label of FAT32 volumes may be stored as a special entry in 131 * the root directory. 132 */ 133 fat_FirstDataSector = 134 UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) + 135 (pfat32_bsbpb->BPB_NumFATs * 136 UINT32BYTES(pfat32_bsbpb->BPB_FATSz32)); 137 fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec); 138 139 // fat_FirstDataSector, fat_BytesPerSector); 140 141 for (offset = fat_BytesPerSector * fat_FirstDataSector;; 142 offset += fat_BytesPerSector) { 143 sector = (uint8_t *)read_buf(fp, offset, fat_BytesPerSector); 144 if (sector == NULL) 145 goto error; 146 147 pfat_entry = (FAT_DES *)sector; 148 do { 149 /* No more entries available. */ 150 if (pfat_entry->DIR_Name[0] == 0) { 151 goto endofchecks; 152 } 153 154 /* Skip empty or long name entries. */ 155 if (pfat_entry->DIR_Name[0] == 0xe5 || 156 (pfat_entry->DIR_Attr & 157 FAT_DES_ATTR_LONG_NAME) == 158 FAT_DES_ATTR_LONG_NAME) { 159 continue; 160 } 161 162 /* 163 * The name of the entry is the volume label if 164 * ATTR_VOLUME_ID is set. 165 */ 166 if (pfat_entry->DIR_Attr & 167 FAT_DES_ATTR_VOLUME_ID) { 168 copysize = MIN(size - 1, 169 sizeof(pfat_entry->DIR_Name)); 170 memcpy(label, pfat_entry->DIR_Name, 171 copysize); 172 label[copysize] = '\0'; 173 goto endofchecks; 174 } 175 } while((uint8_t *)(++pfat_entry) < 176 (uint8_t *)(sector + fat_BytesPerSector)); 177 free(sector); 178 } 179 } else { 180 goto error; 181 } 182 183 endofchecks: 184 rtrim(label, size); 185 186 free(sector0); 187 free(sector); 188 189 return (0); 190 191 error: 192 free(sector0); 193 free(sector); 194 195 return (1); 196 } 197