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 /* 45 * XXX the signature 0x55 0xAA as the last two bytes of 512 is not required 46 * by specifications, but was historically required by fstyp. This check 47 * should be removed, with a more comprehensive BPB validation instead. 48 */ 49 static bool 50 check_signature(uint8_t sector0[512]) 51 { 52 /* Check for the FAT boot sector signature. */ 53 if (sector0[510] == 0x55 && sector0[511] == 0xaa) 54 return (true); 55 /* Special case for Raspberry Pi Pico bootloader. */ 56 if (sector0[510] == 0 && sector0[511] == 0 && 57 sector0[0] == 0xeb && sector0[1] == 0x3c && sector0[2] == 0x90) 58 return (true); 59 return (false); 60 } 61 62 int 63 fstyp_msdosfs(FILE *fp, char *label, size_t size) 64 { 65 FAT_BSBPB *pfat_bsbpb; 66 FAT32_BSBPB *pfat32_bsbpb; 67 FAT_DES *pfat_entry; 68 uint8_t *sector0, *sector; 69 size_t copysize; 70 71 sector0 = NULL; 72 sector = NULL; 73 74 /* Load 1st sector with boot sector and boot parameter block. */ 75 sector0 = (uint8_t *)read_buf(fp, 0, 512); 76 if (sector0 == NULL) 77 return (1); 78 79 if (!check_signature(sector0)) { 80 goto error; 81 } 82 83 /* 84 * Test if this is really a FAT volume and determine the FAT type. 85 */ 86 87 pfat_bsbpb = (FAT_BSBPB *)sector0; 88 pfat32_bsbpb = (FAT32_BSBPB *)sector0; 89 90 if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) { 91 /* 92 * If the BPB_FATSz16 field is not zero and the string "FAT" is 93 * at the right place, this should be a FAT12 or FAT16 volume. 94 */ 95 if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) { 96 goto error; 97 } 98 99 /* A volume with no name should have "NO NAME " as label. */ 100 if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME, 101 sizeof(pfat_bsbpb->BS_VolLab)) == 0) { 102 goto endofchecks; 103 } 104 copysize = MIN(size - 1, sizeof(pfat_bsbpb->BS_VolLab)); 105 memcpy(label, pfat_bsbpb->BS_VolLab, copysize); 106 label[copysize] = '\0'; 107 } else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) { 108 uint32_t fat_FirstDataSector, fat_BytesPerSector, offset; 109 110 /* 111 * If the BPB_FATSz32 field is not zero and the string "FAT" is 112 * at the right place, this should be a FAT32 volume. 113 */ 114 if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) { 115 goto error; 116 } 117 118 /* 119 * If the volume label is not "NO NAME " we're done. 120 */ 121 if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME, 122 sizeof(pfat32_bsbpb->BS_VolLab)) != 0) { 123 copysize = MIN(size - 1, 124 sizeof(pfat32_bsbpb->BS_VolLab)); 125 memcpy(label, pfat32_bsbpb->BS_VolLab, copysize); 126 label[copysize] = '\0'; 127 goto endofchecks; 128 } 129 130 /* 131 * If the volume label "NO NAME " is in the boot sector, the 132 * label of FAT32 volumes may be stored as a special entry in 133 * the root directory. 134 */ 135 fat_FirstDataSector = 136 UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) + 137 (pfat32_bsbpb->BPB_NumFATs * 138 UINT32BYTES(pfat32_bsbpb->BPB_FATSz32)); 139 fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec); 140 141 // fat_FirstDataSector, fat_BytesPerSector); 142 143 for (offset = fat_BytesPerSector * fat_FirstDataSector;; 144 offset += fat_BytesPerSector) { 145 sector = (uint8_t *)read_buf(fp, offset, fat_BytesPerSector); 146 if (sector == NULL) 147 goto error; 148 149 pfat_entry = (FAT_DES *)sector; 150 do { 151 /* No more entries available. */ 152 if (pfat_entry->DIR_Name[0] == 0) { 153 goto endofchecks; 154 } 155 156 /* Skip empty or long name entries. */ 157 if (pfat_entry->DIR_Name[0] == 0xe5 || 158 (pfat_entry->DIR_Attr & 159 FAT_DES_ATTR_LONG_NAME) == 160 FAT_DES_ATTR_LONG_NAME) { 161 continue; 162 } 163 164 /* 165 * The name of the entry is the volume label if 166 * ATTR_VOLUME_ID is set. 167 */ 168 if (pfat_entry->DIR_Attr & 169 FAT_DES_ATTR_VOLUME_ID) { 170 copysize = MIN(size - 1, 171 sizeof(pfat_entry->DIR_Name)); 172 memcpy(label, pfat_entry->DIR_Name, 173 copysize); 174 label[copysize] = '\0'; 175 goto endofchecks; 176 } 177 } while((uint8_t *)(++pfat_entry) < 178 (uint8_t *)(sector + fat_BytesPerSector)); 179 free(sector); 180 } 181 } else { 182 goto error; 183 } 184 185 endofchecks: 186 rtrim(label, size); 187 188 free(sector0); 189 free(sector); 190 191 return (0); 192 193 error: 194 free(sector0); 195 free(sector); 196 197 return (1); 198 } 199