exfat.c (d370fd1cd8fc69e87dc63f4f4a82e5a8b4956c93) exfat.c (85b4c344c8c69ff7993bc0ac833aaf9a8108b88d)
1/*
2 * Copyright (c) 2017 Conrad Meyer <cem@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright

--- 13 unchanged lines hidden (view full) ---

22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD$");
29
1/*
2 * Copyright (c) 2017 Conrad Meyer <cem@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright

--- 13 unchanged lines hidden (view full) ---

22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD$");
29
30#include <sys/param.h>
31#include <sys/endian.h>
32
33#include <assert.h>
34#include <err.h>
35#include <errno.h>
36#include <iconv.h>
37#include <stdbool.h>
30#include <stdint.h>
31#include <stdio.h>
32#include <stdlib.h>
33#include <string.h>
34
35#include "fstyp.h"
36
38#include <stdint.h>
39#include <stdio.h>
40#include <stdlib.h>
41#include <string.h>
42
43#include "fstyp.h"
44
45/*
46 * https://docs.microsoft.com/en-us/windows/win32/fileio/exfat-specification
47 */
48
37struct exfat_vbr {
38 char ev_jmp[3];
39 char ev_fsname[8];
40 char ev_zeros[53];
41 uint64_t ev_part_offset;
42 uint64_t ev_vol_length;
43 uint32_t ev_fat_offset;
44 uint32_t ev_fat_length;

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50 uint16_t ev_vol_flags;
51 uint8_t ev_log_bytes_per_sect;
52 uint8_t ev_log_sect_per_clust;
53 uint8_t ev_num_fats;
54 uint8_t ev_drive_sel;
55 uint8_t ev_percent_used;
56} __packed;
57
49struct exfat_vbr {
50 char ev_jmp[3];
51 char ev_fsname[8];
52 char ev_zeros[53];
53 uint64_t ev_part_offset;
54 uint64_t ev_vol_length;
55 uint32_t ev_fat_offset;
56 uint32_t ev_fat_length;

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62 uint16_t ev_vol_flags;
63 uint8_t ev_log_bytes_per_sect;
64 uint8_t ev_log_sect_per_clust;
65 uint8_t ev_num_fats;
66 uint8_t ev_drive_sel;
67 uint8_t ev_percent_used;
68} __packed;
69
70struct exfat_dirent {
71 uint8_t xde_type;
72#define XDE_TYPE_INUSE_MASK 0x80 /* 1=in use */
73#define XDE_TYPE_INUSE_SHIFT 7
74#define XDE_TYPE_CATEGORY_MASK 0x40 /* 0=primary */
75#define XDE_TYPE_CATEGORY_SHIFT 6
76#define XDE_TYPE_IMPORTNC_MASK 0x20 /* 0=critical */
77#define XDE_TYPE_IMPORTNC_SHIFT 5
78#define XDE_TYPE_CODE_MASK 0x1f
79/* InUse=0, ..., TypeCode=0: EOD. */
80#define XDE_TYPE_EOD 0x00
81#define XDE_TYPE_ALLOC_BITMAP (XDE_TYPE_INUSE_MASK | 0x01)
82#define XDE_TYPE_UPCASE_TABLE (XDE_TYPE_INUSE_MASK | 0x02)
83#define XDE_TYPE_VOL_LABEL (XDE_TYPE_INUSE_MASK | 0x03)
84#define XDE_TYPE_FILE (XDE_TYPE_INUSE_MASK | 0x05)
85#define XDE_TYPE_VOL_GUID (XDE_TYPE_INUSE_MASK | XDE_TYPE_IMPORTNC_MASK)
86#define XDE_TYPE_STREAM_EXT (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK)
87#define XDE_TYPE_FILE_NAME (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | 0x01)
88#define XDE_TYPE_VENDOR (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | XDE_TYPE_IMPORTNC_MASK)
89#define XDE_TYPE_VENDOR_ALLOC (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | XDE_TYPE_IMPORTNC_MASK | 0x01)
90 union {
91 uint8_t xde_generic_[19];
92 struct exde_primary {
93 /*
94 * Count of "secondary" dirents following this one.
95 *
96 * A single logical entity may be composed of a
97 * sequence of several dirents, starting with a primary
98 * one; the rest are secondary dirents.
99 */
100 uint8_t xde_secondary_count_;
101 uint16_t xde_set_chksum_;
102 uint16_t xde_prim_flags_;
103 uint8_t xde_prim_generic_[14];
104 } __packed xde_primary_;
105 struct exde_secondary {
106 uint8_t xde_sec_flags_;
107 uint8_t xde_sec_generic_[18];
108 } __packed xde_secondary_;
109 } u;
110 uint32_t xde_first_cluster;
111 uint64_t xde_data_len;
112} __packed;
113#define xde_generic u.xde_generic_
114#define xde_secondary_count u.xde_primary_.xde_secondary_count
115#define xde_set_chksum u.xde_primary_.xde_set_chksum_
116#define xde_prim_flags u.xde_primary_.xde_prim_flags_
117#define xde_sec_flags u.xde_secondary_.xde_sec_flags_
118_Static_assert(sizeof(struct exfat_dirent) == 32, "spec");
119
120struct exfat_de_label {
121 uint8_t xdel_type; /* XDE_TYPE_VOL_LABEL */
122 uint8_t xdel_char_cnt; /* Length of UCS-2 label */
123 uint16_t xdel_vol_lbl[11];
124 uint8_t xdel_reserved[8];
125} __packed;
126_Static_assert(sizeof(struct exfat_de_label) == 32, "spec");
127
128#define MAIN_BOOT_REGION_SECT 0
129#define BACKUP_BOOT_REGION_SECT 12
130
131#define SUBREGION_CHKSUM_SECT 11
132
133#define FIRST_CLUSTER 2
134#define BAD_BLOCK_SENTINEL 0xfffffff7u
135#define END_CLUSTER_SENTINEL 0xffffffffu
136
137static inline void *
138read_sectn(FILE *fp, off_t sect, unsigned count, unsigned bytespersec)
139{
140 return (read_buf(fp, sect * bytespersec, bytespersec * count));
141}
142
143static inline void *
144read_sect(FILE *fp, off_t sect, unsigned bytespersec)
145{
146 return (read_sectn(fp, sect, 1, bytespersec));
147}
148
149/*
150 * Compute the byte-by-byte multi-sector checksum of the given boot region
151 * (MAIN or BACKUP), for a given bytespersec (typically 512 or 4096).
152 *
153 * Endian-safe; result is host endian.
154 */
155static int
156exfat_compute_boot_chksum(FILE *fp, unsigned region, unsigned bytespersec,
157 uint32_t *result)
158{
159 unsigned char *sector;
160 unsigned n, sect;
161 uint32_t checksum;
162
163 checksum = 0;
164 for (sect = 0; sect < 11; sect++) {
165 sector = read_sect(fp, region + sect, bytespersec);
166 if (sector == NULL)
167 return (ENXIO);
168 for (n = 0; n < bytespersec; n++) {
169 if (sect == 0) {
170 switch (n) {
171 case 106:
172 case 107:
173 case 112:
174 continue;
175 }
176 }
177 checksum = ((checksum & 1) ? 0x80000000u : 0u) +
178 (checksum >> 1) + (uint32_t)sector[n];
179 }
180 free(sector);
181 }
182
183 *result = checksum;
184 return (0);
185}
186
187static void
188convert_label(const uint16_t *ucs2label /* LE */, unsigned ucs2len, char
189 *label_out, size_t label_sz)
190{
191 const char *label;
192 char *label_out_orig;
193 iconv_t cd;
194 size_t srcleft, rc;
195
196 /* Currently hardcoded in fstyp.c as 256 or so. */
197 assert(label_sz > 1);
198
199 if (ucs2len == 0) {
200 /*
201 * Kind of seems bogus, but the spec allows an empty label
202 * entry with the same meaning as no label.
203 */
204 return;
205 }
206
207 if (ucs2len > 11) {
208 warnx("exfat: Bogus volume label length: %u", ucs2len);
209 return;
210 }
211
212 /* dstname="" means convert to the current locale. */
213 cd = iconv_open("", EXFAT_ENC);
214 if (cd == (iconv_t)-1) {
215 warn("exfat: Could not open iconv");
216 return;
217 }
218
219 label_out_orig = label_out;
220
221 /* Dummy up the byte pointer and byte length iconv's API wants. */
222 label = (const void *)ucs2label;
223 srcleft = ucs2len * sizeof(*ucs2label);
224
225 rc = iconv(cd, __DECONST(char **, &label), &srcleft, &label_out,
226 &label_sz);
227 if (rc == (size_t)-1) {
228 warn("exfat: iconv()");
229 *label_out_orig = '\0';
230 } else {
231 /* NUL-terminate result (iconv advances label_out). */
232 if (label_sz == 0)
233 label_out--;
234 *label_out = '\0';
235 }
236
237 iconv_close(cd);
238}
239
240/*
241 * Using the FAT table, look up the next cluster in this chain.
242 */
243static uint32_t
244exfat_fat_next(FILE *fp, const struct exfat_vbr *ev, unsigned BPS,
245 uint32_t cluster)
246{
247 uint32_t fat_offset_sect, clsect, clsectoff;
248 uint32_t *fatsect, nextclust;
249
250 fat_offset_sect = le32toh(ev->ev_fat_offset);
251 clsect = fat_offset_sect + (cluster / (BPS / sizeof(cluster)));
252 clsectoff = (cluster % (BPS / sizeof(cluster)));
253
254 /* XXX This is pretty wasteful without a block cache for the FAT. */
255 fatsect = read_sect(fp, clsect, BPS);
256 nextclust = le32toh(fatsect[clsectoff]);
257 free(fatsect);
258
259 return (nextclust);
260}
261
262static void
263exfat_find_label(FILE *fp, const struct exfat_vbr *ev, unsigned BPS,
264 char *label_out, size_t label_sz)
265{
266 uint32_t rootdir_cluster, sects_per_clust, cluster_offset_sect;
267 off_t rootdir_sect;
268 struct exfat_dirent *declust, *it;
269
270 cluster_offset_sect = le32toh(ev->ev_cluster_offset);
271 rootdir_cluster = le32toh(ev->ev_rootdir_cluster);
272 sects_per_clust = (1u << ev->ev_log_sect_per_clust);
273
274 if (rootdir_cluster < FIRST_CLUSTER) {
275 warnx("%s: invalid rootdir cluster %u < %d", __func__,
276 rootdir_cluster, FIRST_CLUSTER);
277 return;
278 }
279
280
281 for (; rootdir_cluster != END_CLUSTER_SENTINEL;
282 rootdir_cluster = exfat_fat_next(fp, ev, BPS, rootdir_cluster)) {
283 if (rootdir_cluster == BAD_BLOCK_SENTINEL) {
284 warnx("%s: Bogus bad block in root directory chain",
285 __func__);
286 return;
287 }
288
289 rootdir_sect = (rootdir_cluster - FIRST_CLUSTER) *
290 sects_per_clust + cluster_offset_sect;
291 declust = read_sectn(fp, rootdir_sect, sects_per_clust, BPS);
292 for (it = declust;
293 it < declust + (sects_per_clust * BPS / sizeof(*it)); it++) {
294 bool eod = false;
295
296 /*
297 * Simplistic directory traversal; doesn't do any
298 * validation of "MUST" requirements in spec.
299 */
300 switch (it->xde_type) {
301 case XDE_TYPE_EOD:
302 eod = true;
303 break;
304 case XDE_TYPE_VOL_LABEL: {
305 struct exfat_de_label *lde = (void*)it;
306 convert_label(lde->xdel_vol_lbl,
307 lde->xdel_char_cnt, label_out, label_sz);
308 free(declust);
309 return;
310 }
311 }
312
313 if (eod)
314 break;
315 }
316 free(declust);
317 }
318}
319
58int
59fstyp_exfat(FILE *fp, char *label, size_t size)
60{
61 struct exfat_vbr *ev;
320int
321fstyp_exfat(FILE *fp, char *label, size_t size)
322{
323 struct exfat_vbr *ev;
324 uint32_t *cksect;
325 unsigned bytespersec;
326 uint32_t chksum;
327 int error;
62
328
329 cksect = NULL;
63 ev = (struct exfat_vbr *)read_buf(fp, 0, 512);
64 if (ev == NULL || strncmp(ev->ev_fsname, "EXFAT ", 8) != 0)
65 goto fail;
66
330 ev = (struct exfat_vbr *)read_buf(fp, 0, 512);
331 if (ev == NULL || strncmp(ev->ev_fsname, "EXFAT ", 8) != 0)
332 goto fail;
333
334 if (ev->ev_log_bytes_per_sect < 9 || ev->ev_log_bytes_per_sect > 12) {
335 warnx("exfat: Invalid BytesPerSectorShift");
336 goto done;
337 }
338
339 bytespersec = (1u << ev->ev_log_bytes_per_sect);
340
341 error = exfat_compute_boot_chksum(fp, MAIN_BOOT_REGION_SECT,
342 bytespersec, &chksum);
343 if (error != 0)
344 goto done;
345
346 cksect = read_sect(fp, MAIN_BOOT_REGION_SECT + SUBREGION_CHKSUM_SECT,
347 bytespersec);
348
67 /*
349 /*
68 * Reading the volume label requires walking the root directory to look
69 * for a special label file. Left as an exercise for the reader.
350 * Technically the entire sector should be full of repeating 4-byte
351 * checksum pattern, but we only verify the first.
70 */
352 */
353 if (chksum != le32toh(cksect[0])) {
354 warnx("exfat: Found checksum 0x%08x != computed 0x%08x",
355 le32toh(cksect[0]), chksum);
356 goto done;
357 }
358
359 if (show_label)
360 exfat_find_label(fp, ev, bytespersec, label, size);
361
362done:
363 free(cksect);
71 free(ev);
72 return (0);
73
74fail:
75 free(ev);
76 return (1);
77}
364 free(ev);
365 return (0);
366
367fail:
368 free(ev);
369 return (1);
370}