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[thirdparty/systemd.git] / extras / volume_id / lib / fat.c
1 /*
2 * volume_id - reads filesystem label and uuid
3 *
4 * Copyright (C) 2004-2007 Kay Sievers <kay.sievers@vrfy.org>
5 * Copyright (C) 2007 Ryan Lortie <desrt@desrt.ca>
6 *
7 * This program is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program. If not, see <http://www.gnu.org/licenses/>.
19 */
20
21 #ifndef _GNU_SOURCE
22 #define _GNU_SOURCE 1
23 #endif
24
25 #include <stdio.h>
26 #include <stdlib.h>
27 #include <unistd.h>
28 #include <string.h>
29 #include <errno.h>
30 #include <ctype.h>
31
32 #include "libvolume_id.h"
33 #include "libvolume_id-private.h"
34
35 #define FAT12_MAX 0xff5
36 #define FAT16_MAX 0xfff5
37 #define FAT_ATTR_VOLUME_ID 0x08
38 #define FAT_ATTR_DIR 0x10
39 #define FAT_ATTR_LONG_NAME 0x0f
40 #define FAT_ATTR_MASK 0x3f
41 #define FAT_ENTRY_FREE 0xe5
42
43 #define VFAT_LFN_SEQ_MASK 0x3f
44 #define VFAT_LFN_SEQ_LAST 0x40
45 #define VFAT_LFN_SEQ_MAX 20
46 #define VFAT_LFN_CHARS_PER_ENTRY (5 + 6 + 2)
47 #define VFAT_LOWERCASE_NAME 0x10
48 #define VFAT_LOWERCASE_EXT 0x08
49
50 struct vfat_super_block {
51 uint8_t boot_jump[3];
52 uint8_t sysid[8];
53 uint16_t sector_size;
54 uint8_t sectors_per_cluster;
55 uint16_t reserved;
56 uint8_t fats;
57 uint16_t dir_entries;
58 uint16_t sectors;
59 uint8_t media;
60 uint16_t fat_length;
61 uint16_t secs_track;
62 uint16_t heads;
63 uint32_t hidden;
64 uint32_t total_sect;
65 union {
66 struct fat_super_block {
67 uint8_t unknown[3];
68 uint8_t serno[4];
69 uint8_t label[11];
70 uint8_t magic[8];
71 uint8_t dummy2[192];
72 uint8_t pmagic[2];
73 } PACKED fat;
74 struct fat32_super_block {
75 uint32_t fat32_length;
76 uint16_t flags;
77 uint8_t version[2];
78 uint32_t root_cluster;
79 uint16_t fsinfo_sector;
80 uint16_t backup_boot;
81 uint16_t reserved2[6];
82 uint8_t unknown[3];
83 uint8_t serno[4];
84 uint8_t label[11];
85 uint8_t magic[8];
86 uint8_t dummy2[164];
87 uint8_t pmagic[2];
88 } PACKED fat32;
89 } PACKED type;
90 } PACKED;
91
92 struct fat32_fsinfo {
93 uint8_t signature1[4];
94 uint32_t reserved1[120];
95 uint8_t signature2[4];
96 uint32_t free_clusters;
97 uint32_t next_cluster;
98 uint32_t reserved2[4];
99 } PACKED;
100
101 struct vfat_dir_entry {
102 uint8_t name[11];
103 uint8_t attr;
104 uint8_t lowercase;
105 uint8_t fine_time_creat;
106 uint16_t time_creat;
107 uint16_t date_creat;
108 uint16_t date_acc;
109 uint16_t cluster_high;
110 uint16_t time_write;
111 uint16_t date_write;
112 uint16_t cluster_low;
113 uint32_t size;
114 } PACKED;
115
116
117 struct vfat_lfn_entry {
118 uint8_t seq;
119 uint16_t name0[5];
120 uint8_t attr;
121 uint8_t reserved;
122 uint8_t cksum;
123 uint16_t name1[6];
124 uint16_t cluster;
125 uint16_t name2[2];
126 } PACKED;
127
128 static uint8_t fat_lfn_checksum(const uint8_t name[11])
129 {
130 uint8_t cksum = 0;
131 int i;
132
133 /* http://en.wikipedia.org/wiki/File_Allocation_Table */
134 for (i = 0; i < 11; i++)
135 cksum = ((cksum & 1) ? 0x80 : 0) + (cksum >> 1) + name[i];
136
137 return cksum;
138 }
139
140 static size_t fat_read_lfn(uint8_t *filename, size_t fnsize,
141 struct vfat_dir_entry *dir,
142 struct vfat_dir_entry *entry)
143 {
144 uint8_t buffer[VFAT_LFN_SEQ_MAX * VFAT_LFN_CHARS_PER_ENTRY * 2];
145 uint8_t expected_seq = 1;
146 uint8_t cksum;
147 size_t len = 0;
148 size_t fnlen = 0;
149
150 cksum = fat_lfn_checksum(entry->name);
151
152 while (--entry >= dir) {
153 struct vfat_lfn_entry *lfn = (struct vfat_lfn_entry *) entry;
154
155 if (expected_seq > VFAT_LFN_SEQ_MAX)
156 break;
157
158 if ((lfn->attr & FAT_ATTR_MASK) != FAT_ATTR_LONG_NAME)
159 break;
160
161 if (lfn->cksum != cksum)
162 break;
163
164 if ((lfn->seq & VFAT_LFN_SEQ_MASK) != expected_seq++)
165 break;
166
167 if (lfn->cluster != 0)
168 break;
169
170 /* extra paranoia -- should never happen */
171 if (len + sizeof(lfn->name0) + sizeof(lfn->name1) +
172 sizeof(lfn->name2) > sizeof(buffer))
173 break;
174
175 memcpy (&buffer[len], lfn->name0, sizeof(lfn->name0));
176 len += sizeof(lfn->name0);
177 memcpy (&buffer[len], lfn->name1, sizeof(lfn->name1));
178 len += sizeof(lfn->name1);
179 memcpy (&buffer[len], lfn->name2, sizeof(lfn->name2));
180 len += sizeof(lfn->name2);
181
182 if (lfn->seq & VFAT_LFN_SEQ_LAST) {
183 fnlen = volume_id_set_unicode16(filename, fnsize, buffer, LE, len);
184 break;
185 }
186 }
187
188 return fnlen;
189 }
190
191 static size_t fat_read_filename(uint8_t *filename, size_t fnsize,
192 struct vfat_dir_entry *dir, struct vfat_dir_entry *entry)
193 {
194 size_t len;
195 int i;
196
197 /* check if maybe we have LFN entries */
198 len = fat_read_lfn(filename, fnsize, dir, entry);
199 if (len > 0)
200 goto out;
201
202 /* else, read the normal 8.3 name */
203 for (i = 0; i < 11; i++) {
204 if (entry->lowercase & ((i < 8) ? VFAT_LOWERCASE_NAME : VFAT_LOWERCASE_EXT))
205 filename[i] = tolower(entry->name[i]);
206 else
207 filename[i] = entry->name[i];
208 }
209 len = 11;
210
211 out:
212 filename[len] = '\0';
213 return len;
214 }
215
216 /* fills filename, returns string length */
217 static size_t get_fat_attr_volume_id(uint8_t *filename, size_t fnsize,
218 struct vfat_dir_entry *dir, unsigned int count)
219 {
220 unsigned int i;
221
222 for (i = 0; i < count; i++) {
223 /* end marker */
224 if (dir[i].name[0] == 0x00) {
225 dbg("end of dir\n");
226 break;
227 }
228
229 /* empty entry */
230 if (dir[i].name[0] == FAT_ENTRY_FREE)
231 continue;
232
233 /* long name */
234 if ((dir[i].attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
235 continue;
236
237 if ((dir[i].attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
238 /* labels do not have file data */
239 if (dir[i].cluster_high != 0 || dir[i].cluster_low != 0)
240 continue;
241
242 dbg("found ATTR_VOLUME_ID id in root dir\n");
243 return fat_read_filename(filename, fnsize, dir, &dir[i]);
244 }
245
246 dbg("skip dir entry\n");
247 }
248
249 return 0;
250 }
251
252 int volume_id_probe_vfat(struct volume_id *id, uint64_t off, uint64_t size)
253 {
254 uint8_t filename[255 * 3];
255 struct vfat_super_block *vs;
256 struct vfat_dir_entry *dir;
257 struct fat32_fsinfo *fsinfo;
258 uint16_t sector_size;
259 uint16_t dir_entries;
260 uint32_t sect_count;
261 uint16_t reserved;
262 uint32_t fat_size;
263 uint32_t root_cluster;
264 uint32_t dir_size;
265 uint32_t cluster_count;
266 uint16_t fat_length;
267 uint32_t fat32_length;
268 uint64_t root_start;
269 uint32_t start_data_sect;
270 uint16_t root_dir_entries;
271 uint16_t fsinfo_sect;
272 uint8_t *buf;
273 uint32_t buf_size;
274 uint32_t next;
275 int maxloop;
276 size_t fnlen;
277
278 info("probing at offset 0x%" PRIx64 "\n", off);
279
280 buf = volume_id_get_buffer(id, off, 0x400);
281 if (buf == NULL)
282 return -1;
283
284 /* check signature */
285 if (buf[510] != 0x55 || buf[511] != 0xaa)
286 return -1;
287
288 vs = (struct vfat_super_block *) buf;
289 if (memcmp(vs->sysid, "NTFS", 4) == 0)
290 return -1;
291
292 /* believe only that's fat, don't trust the version */
293 if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0)
294 goto magic;
295
296 if (memcmp(vs->type.fat32.magic, "FAT32 ", 8) == 0)
297 goto magic;
298
299 if (memcmp(vs->type.fat.magic, "FAT16 ", 8) == 0)
300 goto magic;
301
302 if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0)
303 goto magic;
304
305 if (memcmp(vs->type.fat.magic, "FAT12 ", 8) == 0)
306 goto magic;
307
308 /* some old floppies don't have a magic, expect the boot jump address to match */
309 if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) &&
310 vs->boot_jump[0] != 0xe9)
311 return -1;
312
313 magic:
314 info("magic found\n");
315 /* reserverd sector count */
316 if (!vs->reserved)
317 return -1;
318
319 /* fat count */
320 if (!vs->fats)
321 return -1;
322
323 /* media check */
324 if (vs->media < 0xf8 && vs->media != 0xf0)
325 return -1;
326
327 /* cluster size check */
328 if (vs->sectors_per_cluster == 0 ||
329 (vs->sectors_per_cluster & (vs->sectors_per_cluster-1)))
330 return -1;
331
332 /* sector size check */
333 sector_size = le16_to_cpu(vs->sector_size);
334 if (sector_size == 0 || ((sector_size & (sector_size-1)) != 0))
335 return -1;
336
337 info("checks passed\n");
338 dbg("sector_size 0x%x\n", sector_size);
339 dbg("sectors_per_cluster 0x%x\n", vs->sectors_per_cluster);
340
341 dir_entries = le16_to_cpu(vs->dir_entries);
342 reserved = le16_to_cpu(vs->reserved);
343 dbg("reserved 0x%x\n", reserved);
344
345 sect_count = le16_to_cpu(vs->sectors);
346 if (sect_count == 0)
347 sect_count = le32_to_cpu(vs->total_sect);
348 dbg("sect_count 0x%x\n", sect_count);
349
350 fat_length = le16_to_cpu(vs->fat_length);
351 info("fat_length 0x%x\n", fat_length);
352 fat32_length = le32_to_cpu(vs->type.fat32.fat32_length);
353 info("fat32_length 0x%x\n", fat32_length);
354
355 if (fat_length)
356 fat_size = fat_length * vs->fats;
357 else if (fat32_length)
358 fat_size = fat32_length * vs->fats;
359 else
360 return -1;
361 info("fat_size 0x%x\n", fat_size);
362
363 dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
364 (sector_size-1)) / sector_size;
365 info("dir_size 0x%x\n", dir_size);
366
367 cluster_count = sect_count - (reserved + fat_size + dir_size);
368 cluster_count /= vs->sectors_per_cluster;
369 info("cluster_count 0x%x\n", cluster_count);
370
371 /* must be FAT32 */
372 if (!fat_length && fat32_length)
373 goto fat32;
374
375 /* cluster_count tells us the format */
376 if (cluster_count < FAT12_MAX)
377 strcpy(id->type_version, "FAT12");
378 else if (cluster_count < FAT16_MAX)
379 strcpy(id->type_version, "FAT16");
380 else
381 goto fat32;
382
383 /* the label may be an attribute in the root directory */
384 root_start = (reserved + fat_size) * sector_size;
385 dbg("root dir start 0x%" PRIx64 "\n", root_start);
386 root_dir_entries = le16_to_cpu(vs->dir_entries);
387 dbg("expected entries 0x%x\n", root_dir_entries);
388
389 buf_size = root_dir_entries * sizeof(struct vfat_dir_entry);
390 buf = volume_id_get_buffer(id, off + root_start, buf_size);
391 if (buf == NULL)
392 goto found;
393
394 dir = (struct vfat_dir_entry*) buf;
395
396 fnlen = get_fat_attr_volume_id(filename, sizeof(filename), dir, root_dir_entries);
397
398 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
399 if (vs == NULL)
400 return -1;
401
402 if (fnlen > 0 && memcmp(filename, "NO NAME ", 11) != 0) {
403 volume_id_set_label_raw(id, filename, fnlen);
404 volume_id_set_label_string(id, filename, fnlen);
405 } else if (memcmp(vs->type.fat.label, "NO NAME ", 11) != 0) {
406 volume_id_set_label_raw(id, vs->type.fat.label, 11);
407 volume_id_set_label_string(id, vs->type.fat.label, 11);
408 }
409 volume_id_set_uuid(id, vs->type.fat.serno, 0, UUID_DOS);
410 goto found;
411
412 fat32:
413 info("looking for FAT32\n");
414 /* FAT32 should have a valid signature in the fsinfo block */
415 fsinfo_sect = le16_to_cpu(vs->type.fat32.fsinfo_sector);
416 buf = volume_id_get_buffer(id, off + (fsinfo_sect * sector_size), 0x200);
417 if (buf == NULL)
418 return -1;
419 fsinfo = (struct fat32_fsinfo *) buf;
420 info("signature1: 0x%02x%02x%02x%02x\n",
421 fsinfo->signature1[0], fsinfo->signature1[1],
422 fsinfo->signature1[2], fsinfo->signature1[3]);
423 info("signature2: 0x%02x%02x%02x%02x\n",
424 fsinfo->signature2[0], fsinfo->signature2[1],
425 fsinfo->signature2[2], fsinfo->signature2[3]);
426 if (memcmp(fsinfo->signature1, "\x52\x52\x61\x41", 4) != 0)
427 return -1;
428 if (memcmp(fsinfo->signature2, "\x72\x72\x41\x61", 4) != 0)
429 return -1 ;
430 info("FAT32 signatures match\n");
431
432 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
433 if (vs == NULL)
434 return -1;
435
436 strcpy(id->type_version, "FAT32");
437
438 /* FAT32 root dir is a cluster chain like any other directory */
439 buf_size = vs->sectors_per_cluster * sector_size;
440 root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
441 dbg("root dir cluster %u\n", root_cluster);
442 start_data_sect = reserved + fat_size;
443
444 next = root_cluster;
445 maxloop = 100;
446 while (--maxloop) {
447 uint32_t next_sect_off;
448 uint64_t next_off;
449 uint64_t fat_entry_off;
450 int count;
451
452 dbg("next cluster %u\n", next);
453 next_sect_off = (next - 2) * vs->sectors_per_cluster;
454 next_off = (start_data_sect + next_sect_off) * sector_size;
455 dbg("cluster offset 0x%" PRIx64 "\n", next_off);
456
457 /* get cluster */
458 buf = volume_id_get_buffer(id, off + next_off, buf_size);
459 if (buf == NULL)
460 goto found;
461
462 dir = (struct vfat_dir_entry*) buf;
463 count = buf_size / sizeof(struct vfat_dir_entry);
464 dbg("expected entries 0x%x\n", count);
465
466 fnlen = get_fat_attr_volume_id(filename, sizeof(filename), dir, count);
467 if (fnlen > 0)
468 break;
469
470 /* get FAT entry */
471 fat_entry_off = (reserved * sector_size) + (next * sizeof(uint32_t));
472 buf = volume_id_get_buffer(id, off + fat_entry_off, buf_size);
473 if (buf == NULL)
474 goto found;
475
476 /* set next cluster */
477 next = le32_to_cpu(*((uint32_t *) buf)) & 0x0fffffff;
478 if (next < 2 || next >= 0x0ffffff0)
479 break;
480 }
481 if (maxloop == 0)
482 dbg("reached maximum follow count of root cluster chain, give up\n");
483
484 vs = (struct vfat_super_block *) volume_id_get_buffer(id, off, 0x200);
485 if (vs == NULL)
486 return -1;
487
488 if (fnlen > 0 && memcmp(filename, "NO NAME ", 11) != 0) {
489 volume_id_set_label_raw(id, filename, fnlen);
490 volume_id_set_label_string(id, filename, fnlen);
491 } else if (memcmp(vs->type.fat32.label, "NO NAME ", 11) != 0) {
492 volume_id_set_label_raw(id, vs->type.fat32.label, 11);
493 volume_id_set_label_string(id, vs->type.fat32.label, 11);
494 }
495 volume_id_set_uuid(id, vs->type.fat32.serno, 0, UUID_DOS);
496
497 found:
498 volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
499 id->type = "vfat";
500
501 return 0;
502 }
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