1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org> 5 * Copyright (c) 2006 Tobias Reifenberger 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30 #include <sys/cdefs.h> 31 #include <sys/param.h> 32 #include <sys/systm.h> 33 #include <sys/kernel.h> 34 #include <sys/malloc.h> 35 36 #include <geom/geom.h> 37 #include <geom/geom_dbg.h> 38 #include <geom/label/g_label.h> 39 #include <geom/label/g_label_msdosfs.h> 40 41 #define LABEL_NO_NAME "NO NAME " 42 43 static void 44 g_label_msdosfs_taste(struct g_consumer *cp, char *label, size_t size) 45 { 46 struct g_provider *pp; 47 FAT_BSBPB *pfat_bsbpb; 48 FAT32_BSBPB *pfat32_bsbpb; 49 FAT_DES *pfat_entry; 50 uint8_t *sector0, *sector; 51 size_t copysize; 52 53 g_topology_assert_not(); 54 pp = cp->provider; 55 sector0 = NULL; 56 sector = NULL; 57 bzero(label, size); 58 59 /* Check if the sector size of the medium is a valid FAT sector size. */ 60 switch(pp->sectorsize) { 61 case 512: 62 case 1024: 63 case 2048: 64 case 4096: 65 break; 66 default: 67 G_LABEL_DEBUG(1, "MSDOSFS: %s: sector size %d not compatible.", 68 pp->name, pp->sectorsize); 69 return; 70 } 71 72 /* Load 1st sector with boot sector and boot parameter block. */ 73 sector0 = (uint8_t *)g_read_data(cp, 0, pp->sectorsize, NULL); 74 if (sector0 == NULL) 75 return; 76 77 /* Check for the FAT boot sector signature. */ 78 if (sector0[510] != 0x55 || sector0[511] != 0xaa) { 79 G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT signature found.", 80 pp->name); 81 goto error; 82 } 83 84 /* 85 * Test if this is really a FAT volume and determine the FAT type. 86 */ 87 88 pfat_bsbpb = (FAT_BSBPB *)sector0; 89 pfat32_bsbpb = (FAT32_BSBPB *)sector0; 90 91 if (UINT16BYTES(pfat_bsbpb->BPB_FATSz16) != 0) { 92 /* 93 * If the BPB_FATSz16 field is not zero and the string "FAT" is 94 * at the right place, this should be a FAT12 or FAT16 volume. 95 */ 96 if (strncmp(pfat_bsbpb->BS_FilSysType, "FAT", 3) != 0) { 97 G_LABEL_DEBUG(1, 98 "MSDOSFS: %s: FAT12/16 volume not valid.", 99 pp->name); 100 goto error; 101 } 102 G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT12/FAT16 volume detected.", 103 pp->name); 104 105 /* A volume with no name should have "NO NAME " as label. */ 106 if (strncmp(pfat_bsbpb->BS_VolLab, LABEL_NO_NAME, 107 sizeof(pfat_bsbpb->BS_VolLab)) == 0) { 108 G_LABEL_DEBUG(1, 109 "MSDOSFS: %s: FAT12/16 volume has no name.", 110 pp->name); 111 goto error; 112 } 113 copysize = MIN(size - 1, sizeof(pfat_bsbpb->BS_VolLab)); 114 memcpy(label, pfat_bsbpb->BS_VolLab, copysize); 115 label[copysize] = '\0'; 116 } else if (UINT32BYTES(pfat32_bsbpb->BPB_FATSz32) != 0) { 117 uint32_t fat_FirstDataSector, fat_BytesPerSector, offset; 118 119 /* 120 * If the BPB_FATSz32 field is not zero and the string "FAT" is 121 * at the right place, this should be a FAT32 volume. 122 */ 123 if (strncmp(pfat32_bsbpb->BS_FilSysType, "FAT", 3) != 0) { 124 G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume not valid.", 125 pp->name); 126 goto error; 127 } 128 G_LABEL_DEBUG(1, "MSDOSFS: %s: FAT32 volume detected.", 129 pp->name); 130 131 /* 132 * If the volume label is not "NO NAME " we're done. 133 */ 134 if (strncmp(pfat32_bsbpb->BS_VolLab, LABEL_NO_NAME, 135 sizeof(pfat32_bsbpb->BS_VolLab)) != 0) { 136 copysize = MIN(size - 1, 137 sizeof(pfat32_bsbpb->BS_VolLab)); 138 memcpy(label, pfat32_bsbpb->BS_VolLab, copysize); 139 label[copysize] = '\0'; 140 goto endofchecks; 141 } 142 143 /* 144 * If the volume label "NO NAME " is in the boot sector, the 145 * label of FAT32 volumes may be stored as a special entry in 146 * the root directory. 147 */ 148 fat_FirstDataSector = 149 UINT16BYTES(pfat32_bsbpb->BPB_RsvdSecCnt) + 150 (pfat32_bsbpb->BPB_NumFATs * 151 UINT32BYTES(pfat32_bsbpb->BPB_FATSz32)); 152 fat_BytesPerSector = UINT16BYTES(pfat32_bsbpb->BPB_BytsPerSec); 153 154 G_LABEL_DEBUG(2, 155 "MSDOSFS: FAT_FirstDataSector=0x%x, FAT_BytesPerSector=%d", 156 fat_FirstDataSector, fat_BytesPerSector); 157 if (fat_BytesPerSector == 0 || 158 fat_BytesPerSector % pp->sectorsize != 0) { 159 G_LABEL_DEBUG(1, "MSDOSFS: %s: corrupted BPB", 160 pp->name); 161 goto error; 162 } 163 164 for (offset = fat_BytesPerSector * fat_FirstDataSector;; 165 offset += fat_BytesPerSector) { 166 sector = (uint8_t *)g_read_data(cp, offset, 167 fat_BytesPerSector, NULL); 168 if (sector == NULL) 169 goto error; 170 171 pfat_entry = (FAT_DES *)sector; 172 do { 173 /* No more entries available. */ 174 if (pfat_entry->DIR_Name[0] == 0) { 175 G_LABEL_DEBUG(1, "MSDOSFS: %s: " 176 "FAT32 volume has no name.", 177 pp->name); 178 goto error; 179 } 180 181 /* Skip empty or long name entries. */ 182 if (pfat_entry->DIR_Name[0] == 0xe5 || 183 (pfat_entry->DIR_Attr & 184 FAT_DES_ATTR_LONG_NAME) == 185 FAT_DES_ATTR_LONG_NAME) { 186 continue; 187 } 188 189 /* 190 * The name of the entry is the volume label if 191 * ATTR_VOLUME_ID is set. 192 */ 193 if (pfat_entry->DIR_Attr & 194 FAT_DES_ATTR_VOLUME_ID) { 195 copysize = MIN(size - 1, 196 sizeof(pfat_entry->DIR_Name)); 197 memcpy(label, pfat_entry->DIR_Name, 198 copysize); 199 label[copysize] = '\0'; 200 goto endofchecks; 201 } 202 } while((uint8_t *)(++pfat_entry) < 203 (uint8_t *)(sector + fat_BytesPerSector)); 204 g_free(sector); 205 } 206 } else { 207 G_LABEL_DEBUG(1, "MSDOSFS: %s: no FAT volume detected.", 208 pp->name); 209 goto error; 210 } 211 212 endofchecks: 213 g_label_rtrim(label, size); 214 215 error: 216 g_free(sector0); 217 g_free(sector); 218 } 219 220 struct g_label_desc g_label_msdosfs = { 221 .ld_taste = g_label_msdosfs_taste, 222 .ld_dirprefix = "msdosfs/", 223 .ld_enabled = 1 224 }; 225 226 G_LABEL_INIT(msdosfs, g_label_msdosfs, "Create device nodes for MSDOSFS volumes"); 227