1 /*
2 * Copyright (c) 2017 Conrad Meyer <[email protected]>
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
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 #ifdef WITH_ICONV
37 #include <iconv.h>
38 #endif
39 #include <stdbool.h>
40 #include <stdint.h>
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include <string.h>
44
45 #include "fstyp.h"
46
47 /*
48 * https://docs.microsoft.com/en-us/windows/win32/fileio/exfat-specification
49 */
50
51 struct exfat_vbr {
52 char ev_jmp[3];
53 char ev_fsname[8];
54 char ev_zeros[53];
55 uint64_t ev_part_offset;
56 uint64_t ev_vol_length;
57 uint32_t ev_fat_offset;
58 uint32_t ev_fat_length;
59 uint32_t ev_cluster_offset;
60 uint32_t ev_cluster_count;
61 uint32_t ev_rootdir_cluster;
62 uint32_t ev_vol_serial;
63 uint16_t ev_fs_revision;
64 uint16_t ev_vol_flags;
65 uint8_t ev_log_bytes_per_sect;
66 uint8_t ev_log_sect_per_clust;
67 uint8_t ev_num_fats;
68 uint8_t ev_drive_sel;
69 uint8_t ev_percent_used;
70 } __packed;
71
72 struct exfat_dirent {
73 uint8_t xde_type;
74 #define XDE_TYPE_INUSE_MASK 0x80 /* 1=in use */
75 #define XDE_TYPE_INUSE_SHIFT 7
76 #define XDE_TYPE_CATEGORY_MASK 0x40 /* 0=primary */
77 #define XDE_TYPE_CATEGORY_SHIFT 6
78 #define XDE_TYPE_IMPORTNC_MASK 0x20 /* 0=critical */
79 #define XDE_TYPE_IMPORTNC_SHIFT 5
80 #define XDE_TYPE_CODE_MASK 0x1f
81 /* InUse=0, ..., TypeCode=0: EOD. */
82 #define XDE_TYPE_EOD 0x00
83 #define XDE_TYPE_ALLOC_BITMAP (XDE_TYPE_INUSE_MASK | 0x01)
84 #define XDE_TYPE_UPCASE_TABLE (XDE_TYPE_INUSE_MASK | 0x02)
85 #define XDE_TYPE_VOL_LABEL (XDE_TYPE_INUSE_MASK | 0x03)
86 #define XDE_TYPE_FILE (XDE_TYPE_INUSE_MASK | 0x05)
87 #define XDE_TYPE_VOL_GUID (XDE_TYPE_INUSE_MASK | XDE_TYPE_IMPORTNC_MASK)
88 #define XDE_TYPE_STREAM_EXT (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK)
89 #define XDE_TYPE_FILE_NAME (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | 0x01)
90 #define XDE_TYPE_VENDOR (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | XDE_TYPE_IMPORTNC_MASK)
91 #define XDE_TYPE_VENDOR_ALLOC (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | XDE_TYPE_IMPORTNC_MASK | 0x01)
92 union {
93 uint8_t xde_generic_[19];
94 struct exde_primary {
95 /*
96 * Count of "secondary" dirents following this one.
97 *
98 * A single logical entity may be composed of a
99 * sequence of several dirents, starting with a primary
100 * one; the rest are secondary dirents.
101 */
102 uint8_t xde_secondary_count_;
103 uint16_t xde_set_chksum_;
104 uint16_t xde_prim_flags_;
105 uint8_t xde_prim_generic_[14];
106 } __packed xde_primary_;
107 struct exde_secondary {
108 uint8_t xde_sec_flags_;
109 uint8_t xde_sec_generic_[18];
110 } __packed xde_secondary_;
111 } u;
112 uint32_t xde_first_cluster;
113 uint64_t xde_data_len;
114 } __packed;
115 #define xde_generic u.xde_generic_
116 #define xde_secondary_count u.xde_primary_.xde_secondary_count
117 #define xde_set_chksum u.xde_primary_.xde_set_chksum_
118 #define xde_prim_flags u.xde_primary_.xde_prim_flags_
119 #define xde_sec_flags u.xde_secondary_.xde_sec_flags_
120 _Static_assert(sizeof(struct exfat_dirent) == 32, "spec");
121
122 struct exfat_de_label {
123 uint8_t xdel_type; /* XDE_TYPE_VOL_LABEL */
124 uint8_t xdel_char_cnt; /* Length of UCS-2 label */
125 uint16_t xdel_vol_lbl[11];
126 uint8_t xdel_reserved[8];
127 } __packed;
128 _Static_assert(sizeof(struct exfat_de_label) == 32, "spec");
129
130 #define MAIN_BOOT_REGION_SECT 0
131 #define BACKUP_BOOT_REGION_SECT 12
132
133 #define SUBREGION_CHKSUM_SECT 11
134
135 #define FIRST_CLUSTER 2
136 #define BAD_BLOCK_SENTINEL 0xfffffff7u
137 #define END_CLUSTER_SENTINEL 0xffffffffu
138
139 static inline void *
read_sectn(FILE * fp,off_t sect,unsigned count,unsigned bytespersec)140 read_sectn(FILE *fp, off_t sect, unsigned count, unsigned bytespersec)
141 {
142 return (read_buf(fp, sect * bytespersec, bytespersec * count));
143 }
144
145 static inline void *
read_sect(FILE * fp,off_t sect,unsigned bytespersec)146 read_sect(FILE *fp, off_t sect, unsigned bytespersec)
147 {
148 return (read_sectn(fp, sect, 1, bytespersec));
149 }
150
151 /*
152 * Compute the byte-by-byte multi-sector checksum of the given boot region
153 * (MAIN or BACKUP), for a given bytespersec (typically 512 or 4096).
154 *
155 * Endian-safe; result is host endian.
156 */
157 static int
exfat_compute_boot_chksum(FILE * fp,unsigned region,unsigned bytespersec,uint32_t * result)158 exfat_compute_boot_chksum(FILE *fp, unsigned region, unsigned bytespersec,
159 uint32_t *result)
160 {
161 unsigned char *sector;
162 unsigned n, sect;
163 uint32_t checksum;
164
165 checksum = 0;
166 for (sect = 0; sect < 11; sect++) {
167 sector = read_sect(fp, region + sect, bytespersec);
168 if (sector == NULL)
169 return (ENXIO);
170 for (n = 0; n < bytespersec; n++) {
171 if (sect == 0) {
172 switch (n) {
173 case 106:
174 case 107:
175 case 112:
176 continue;
177 }
178 }
179 checksum = ((checksum & 1) ? 0x80000000u : 0u) +
180 (checksum >> 1) + (uint32_t)sector[n];
181 }
182 free(sector);
183 }
184
185 *result = checksum;
186 return (0);
187 }
188
189 #ifdef WITH_ICONV
190 static void
convert_label(const uint16_t * ucs2label,unsigned ucs2len,char * label_out,size_t label_sz)191 convert_label(const uint16_t *ucs2label /* LE */, unsigned ucs2len, char
192 *label_out, size_t label_sz)
193 {
194 const char *label;
195 char *label_out_orig;
196 iconv_t cd;
197 size_t srcleft, rc;
198
199 /* Currently hardcoded in fstyp.c as 256 or so. */
200 assert(label_sz > 1);
201
202 if (ucs2len == 0) {
203 /*
204 * Kind of seems bogus, but the spec allows an empty label
205 * entry with the same meaning as no label.
206 */
207 return;
208 }
209
210 if (ucs2len > 11) {
211 warnx("exfat: Bogus volume label length: %u", ucs2len);
212 return;
213 }
214
215 /* dstname="" means convert to the current locale. */
216 cd = iconv_open("", EXFAT_ENC);
217 if (cd == (iconv_t)-1) {
218 warn("exfat: Could not open iconv");
219 return;
220 }
221
222 label_out_orig = label_out;
223
224 /* Dummy up the byte pointer and byte length iconv's API wants. */
225 label = (const void *)ucs2label;
226 srcleft = ucs2len * sizeof(*ucs2label);
227
228 rc = iconv(cd, __DECONST(char **, &label), &srcleft, &label_out,
229 &label_sz);
230 if (rc == (size_t)-1) {
231 warn("exfat: iconv()");
232 *label_out_orig = '\0';
233 } else {
234 /* NUL-terminate result (iconv advances label_out). */
235 if (label_sz == 0)
236 label_out--;
237 *label_out = '\0';
238 }
239
240 iconv_close(cd);
241 }
242
243 /*
244 * Using the FAT table, look up the next cluster in this chain.
245 */
246 static uint32_t
exfat_fat_next(FILE * fp,const struct exfat_vbr * ev,unsigned BPS,uint32_t cluster)247 exfat_fat_next(FILE *fp, const struct exfat_vbr *ev, unsigned BPS,
248 uint32_t cluster)
249 {
250 uint32_t fat_offset_sect, clsect, clsectoff;
251 uint32_t *fatsect, nextclust;
252
253 fat_offset_sect = le32toh(ev->ev_fat_offset);
254 clsect = fat_offset_sect + (cluster / (BPS / sizeof(cluster)));
255 clsectoff = (cluster % (BPS / sizeof(cluster)));
256
257 /* XXX This is pretty wasteful without a block cache for the FAT. */
258 fatsect = read_sect(fp, clsect, BPS);
259 nextclust = le32toh(fatsect[clsectoff]);
260 free(fatsect);
261
262 return (nextclust);
263 }
264
265 static void
exfat_find_label(FILE * fp,const struct exfat_vbr * ev,unsigned BPS,char * label_out,size_t label_sz)266 exfat_find_label(FILE *fp, const struct exfat_vbr *ev, unsigned BPS,
267 char *label_out, size_t label_sz)
268 {
269 uint32_t rootdir_cluster, sects_per_clust, cluster_offset_sect;
270 off_t rootdir_sect;
271 struct exfat_dirent *declust, *it;
272
273 cluster_offset_sect = le32toh(ev->ev_cluster_offset);
274 rootdir_cluster = le32toh(ev->ev_rootdir_cluster);
275 sects_per_clust = (1u << ev->ev_log_sect_per_clust);
276
277 if (rootdir_cluster < FIRST_CLUSTER) {
278 warnx("%s: invalid rootdir cluster %u < %d", __func__,
279 rootdir_cluster, FIRST_CLUSTER);
280 return;
281 }
282
283
284 for (; rootdir_cluster != END_CLUSTER_SENTINEL;
285 rootdir_cluster = exfat_fat_next(fp, ev, BPS, rootdir_cluster)) {
286 if (rootdir_cluster == BAD_BLOCK_SENTINEL) {
287 warnx("%s: Bogus bad block in root directory chain",
288 __func__);
289 return;
290 }
291
292 rootdir_sect = (rootdir_cluster - FIRST_CLUSTER) *
293 sects_per_clust + cluster_offset_sect;
294 declust = read_sectn(fp, rootdir_sect, sects_per_clust, BPS);
295 for (it = declust;
296 it < declust + (sects_per_clust * BPS / sizeof(*it)); it++) {
297 bool eod = false;
298
299 /*
300 * Simplistic directory traversal; doesn't do any
301 * validation of "MUST" requirements in spec.
302 */
303 switch (it->xde_type) {
304 case XDE_TYPE_EOD:
305 eod = true;
306 break;
307 case XDE_TYPE_VOL_LABEL: {
308 struct exfat_de_label *lde = (void*)it;
309 convert_label(lde->xdel_vol_lbl,
310 lde->xdel_char_cnt, label_out, label_sz);
311 free(declust);
312 return;
313 }
314 }
315
316 if (eod)
317 break;
318 }
319 free(declust);
320 }
321 }
322 #endif /* WITH_ICONV */
323
324 int
fstyp_exfat(FILE * fp,char * label,size_t size)325 fstyp_exfat(FILE *fp, char *label, size_t size)
326 {
327 struct exfat_vbr *ev;
328 uint32_t *cksect;
329 unsigned bytespersec;
330 uint32_t chksum;
331 int error;
332
333 error = 1;
334 cksect = NULL;
335 ev = (struct exfat_vbr *)read_buf(fp, 0, 512);
336 if (ev == NULL || strncmp(ev->ev_fsname, "EXFAT ", 8) != 0)
337 goto out;
338
339 if (ev->ev_log_bytes_per_sect < 9 || ev->ev_log_bytes_per_sect > 12) {
340 warnx("exfat: Invalid BytesPerSectorShift");
341 goto out;
342 }
343
344 bytespersec = (1u << ev->ev_log_bytes_per_sect);
345
346 error = exfat_compute_boot_chksum(fp, MAIN_BOOT_REGION_SECT,
347 bytespersec, &chksum);
348 if (error != 0)
349 goto out;
350
351 cksect = read_sect(fp, MAIN_BOOT_REGION_SECT + SUBREGION_CHKSUM_SECT,
352 bytespersec);
353
354 /*
355 * Technically the entire sector should be full of repeating 4-byte
356 * checksum pattern, but we only verify the first.
357 */
358 if (chksum != le32toh(cksect[0])) {
359 warnx("exfat: Found checksum 0x%08x != computed 0x%08x",
360 le32toh(cksect[0]), chksum);
361 error = 1;
362 goto out;
363 }
364
365 #ifdef WITH_ICONV
366 if (show_label)
367 exfat_find_label(fp, ev, bytespersec, label, size);
368 #else
369 if (show_label) {
370 warnx("label not available without iconv support");
371 memset(label, 0, size);
372 }
373 #endif
374
375 out:
376 free(cksect);
377 free(ev);
378 return (error != 0);
379 }
380