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
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/param.h>
28 #include <sys/endian.h>
29
30 #include <assert.h>
31 #include <err.h>
32 #include <errno.h>
33 #include <iconv.h>
34 #include <stdbool.h>
35 #include <stdint.h>
36 #include <stdio.h>
37 #include <stdlib.h>
38 #include <string.h>
39
40 #include "fstyp.h"
41
42 /*
43 * https://docs.microsoft.com/en-us/windows/win32/fileio/exfat-specification
44 */
45
46 struct exfat_vbr {
47 char ev_jmp[3];
48 char ev_fsname[8];
49 char ev_zeros[53];
50 uint64_t ev_part_offset;
51 uint64_t ev_vol_length;
52 uint32_t ev_fat_offset;
53 uint32_t ev_fat_length;
54 uint32_t ev_cluster_offset;
55 uint32_t ev_cluster_count;
56 uint32_t ev_rootdir_cluster;
57 uint32_t ev_vol_serial;
58 uint16_t ev_fs_revision;
59 uint16_t ev_vol_flags;
60 uint8_t ev_log_bytes_per_sect;
61 uint8_t ev_log_sect_per_clust;
62 uint8_t ev_num_fats;
63 uint8_t ev_drive_sel;
64 uint8_t ev_percent_used;
65 } __packed;
66
67 struct exfat_dirent {
68 uint8_t xde_type;
69 #define XDE_TYPE_INUSE_MASK 0x80 /* 1=in use */
70 #define XDE_TYPE_INUSE_SHIFT 7
71 #define XDE_TYPE_CATEGORY_MASK 0x40 /* 0=primary */
72 #define XDE_TYPE_CATEGORY_SHIFT 6
73 #define XDE_TYPE_IMPORTNC_MASK 0x20 /* 0=critical */
74 #define XDE_TYPE_IMPORTNC_SHIFT 5
75 #define XDE_TYPE_CODE_MASK 0x1f
76 /* InUse=0, ..., TypeCode=0: EOD. */
77 #define XDE_TYPE_EOD 0x00
78 #define XDE_TYPE_ALLOC_BITMAP (XDE_TYPE_INUSE_MASK | 0x01)
79 #define XDE_TYPE_UPCASE_TABLE (XDE_TYPE_INUSE_MASK | 0x02)
80 #define XDE_TYPE_VOL_LABEL (XDE_TYPE_INUSE_MASK | 0x03)
81 #define XDE_TYPE_FILE (XDE_TYPE_INUSE_MASK | 0x05)
82 #define XDE_TYPE_VOL_GUID (XDE_TYPE_INUSE_MASK | XDE_TYPE_IMPORTNC_MASK)
83 #define XDE_TYPE_STREAM_EXT (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK)
84 #define XDE_TYPE_FILE_NAME (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | 0x01)
85 #define XDE_TYPE_VENDOR (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | XDE_TYPE_IMPORTNC_MASK)
86 #define XDE_TYPE_VENDOR_ALLOC (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | XDE_TYPE_IMPORTNC_MASK | 0x01)
87 union {
88 uint8_t xde_generic_[19];
89 struct exde_primary {
90 /*
91 * Count of "secondary" dirents following this one.
92 *
93 * A single logical entity may be composed of a
94 * sequence of several dirents, starting with a primary
95 * one; the rest are secondary dirents.
96 */
97 uint8_t xde_secondary_count_;
98 uint16_t xde_set_chksum_;
99 uint16_t xde_prim_flags_;
100 uint8_t xde_prim_generic_[14];
101 } __packed xde_primary_;
102 struct exde_secondary {
103 uint8_t xde_sec_flags_;
104 uint8_t xde_sec_generic_[18];
105 } __packed xde_secondary_;
106 } u;
107 uint32_t xde_first_cluster;
108 uint64_t xde_data_len;
109 } __packed;
110 #define xde_generic u.xde_generic_
111 #define xde_secondary_count u.xde_primary_.xde_secondary_count
112 #define xde_set_chksum u.xde_primary_.xde_set_chksum_
113 #define xde_prim_flags u.xde_primary_.xde_prim_flags_
114 #define xde_sec_flags u.xde_secondary_.xde_sec_flags_
115 _Static_assert(sizeof(struct exfat_dirent) == 32, "spec");
116
117 struct exfat_de_label {
118 uint8_t xdel_type; /* XDE_TYPE_VOL_LABEL */
119 uint8_t xdel_char_cnt; /* Length of UCS-2 label */
120 uint16_t xdel_vol_lbl[11];
121 uint8_t xdel_reserved[8];
122 } __packed;
123 _Static_assert(sizeof(struct exfat_de_label) == 32, "spec");
124
125 #define MAIN_BOOT_REGION_SECT 0
126 #define BACKUP_BOOT_REGION_SECT 12
127
128 #define SUBREGION_CHKSUM_SECT 11
129
130 #define FIRST_CLUSTER 2
131 #define BAD_BLOCK_SENTINEL 0xfffffff7u
132 #define END_CLUSTER_SENTINEL 0xffffffffu
133
134 static inline void *
read_sectn(FILE * fp,off_t sect,unsigned count,unsigned bytespersec)135 read_sectn(FILE *fp, off_t sect, unsigned count, unsigned bytespersec)
136 {
137 return (read_buf(fp, sect * bytespersec, bytespersec * count));
138 }
139
140 static inline void *
read_sect(FILE * fp,off_t sect,unsigned bytespersec)141 read_sect(FILE *fp, off_t sect, unsigned bytespersec)
142 {
143 return (read_sectn(fp, sect, 1, bytespersec));
144 }
145
146 /*
147 * Compute the byte-by-byte multi-sector checksum of the given boot region
148 * (MAIN or BACKUP), for a given bytespersec (typically 512 or 4096).
149 *
150 * Endian-safe; result is host endian.
151 */
152 static int
exfat_compute_boot_chksum(FILE * fp,unsigned region,unsigned bytespersec,uint32_t * result)153 exfat_compute_boot_chksum(FILE *fp, unsigned region, unsigned bytespersec,
154 uint32_t *result)
155 {
156 unsigned char *sector;
157 unsigned n, sect;
158 uint32_t checksum;
159
160 checksum = 0;
161 for (sect = 0; sect < 11; sect++) {
162 sector = read_sect(fp, region + sect, bytespersec);
163 if (sector == NULL)
164 return (ENXIO);
165 for (n = 0; n < bytespersec; n++) {
166 if (sect == 0) {
167 switch (n) {
168 case 106:
169 case 107:
170 case 112:
171 continue;
172 }
173 }
174 checksum = ((checksum & 1) ? 0x80000000u : 0u) +
175 (checksum >> 1) + (uint32_t)sector[n];
176 }
177 free(sector);
178 }
179
180 *result = checksum;
181 return (0);
182 }
183
184 static void
convert_label(const uint16_t * ucs2label,unsigned ucs2len,char * label_out,size_t label_sz)185 convert_label(const uint16_t *ucs2label /* LE */, unsigned ucs2len, char
186 *label_out, size_t label_sz)
187 {
188 const char *label;
189 char *label_out_orig;
190 iconv_t cd;
191 size_t srcleft, rc;
192
193 /* Currently hardcoded in fstyp.c as 256 or so. */
194 assert(label_sz > 1);
195
196 if (ucs2len == 0) {
197 /*
198 * Kind of seems bogus, but the spec allows an empty label
199 * entry with the same meaning as no label.
200 */
201 return;
202 }
203
204 if (ucs2len > 11) {
205 warnx("exfat: Bogus volume label length: %u", ucs2len);
206 return;
207 }
208
209 /* dstname="" means convert to the current locale. */
210 cd = iconv_open("", EXFAT_ENC);
211 if (cd == (iconv_t)-1) {
212 warn("exfat: Could not open iconv");
213 return;
214 }
215
216 label_out_orig = label_out;
217
218 /* Dummy up the byte pointer and byte length iconv's API wants. */
219 label = (const void *)ucs2label;
220 srcleft = ucs2len * sizeof(*ucs2label);
221
222 rc = iconv(cd, __DECONST(char **, &label), &srcleft, &label_out,
223 &label_sz);
224 if (rc == (size_t)-1) {
225 warn("exfat: iconv()");
226 *label_out_orig = '\0';
227 } else {
228 /* NUL-terminate result (iconv advances label_out). */
229 if (label_sz == 0)
230 label_out--;
231 *label_out = '\0';
232 }
233
234 iconv_close(cd);
235 }
236
237 /*
238 * Using the FAT table, look up the next cluster in this chain.
239 */
240 static uint32_t
exfat_fat_next(FILE * fp,const struct exfat_vbr * ev,unsigned BPS,uint32_t cluster)241 exfat_fat_next(FILE *fp, const struct exfat_vbr *ev, unsigned BPS,
242 uint32_t cluster)
243 {
244 uint32_t fat_offset_sect, clsect, clsectoff;
245 uint32_t *fatsect, nextclust;
246
247 fat_offset_sect = le32toh(ev->ev_fat_offset);
248 clsect = fat_offset_sect + (cluster / (BPS / sizeof(cluster)));
249 clsectoff = (cluster % (BPS / sizeof(cluster)));
250
251 /* XXX This is pretty wasteful without a block cache for the FAT. */
252 fatsect = read_sect(fp, clsect, BPS);
253 nextclust = le32toh(fatsect[clsectoff]);
254 free(fatsect);
255
256 return (nextclust);
257 }
258
259 static void
exfat_find_label(FILE * fp,const struct exfat_vbr * ev,unsigned BPS,char * label_out,size_t label_sz)260 exfat_find_label(FILE *fp, const struct exfat_vbr *ev, unsigned BPS,
261 char *label_out, size_t label_sz)
262 {
263 uint32_t rootdir_cluster, sects_per_clust, cluster_offset_sect;
264 off_t rootdir_sect;
265 struct exfat_dirent *declust, *it;
266
267 cluster_offset_sect = le32toh(ev->ev_cluster_offset);
268 rootdir_cluster = le32toh(ev->ev_rootdir_cluster);
269 sects_per_clust = (1u << ev->ev_log_sect_per_clust);
270
271 if (rootdir_cluster < FIRST_CLUSTER) {
272 warnx("%s: invalid rootdir cluster %u < %d", __func__,
273 rootdir_cluster, FIRST_CLUSTER);
274 return;
275 }
276
277
278 for (; rootdir_cluster != END_CLUSTER_SENTINEL;
279 rootdir_cluster = exfat_fat_next(fp, ev, BPS, rootdir_cluster)) {
280 if (rootdir_cluster == BAD_BLOCK_SENTINEL) {
281 warnx("%s: Bogus bad block in root directory chain",
282 __func__);
283 return;
284 }
285
286 rootdir_sect = (rootdir_cluster - FIRST_CLUSTER) *
287 sects_per_clust + cluster_offset_sect;
288 declust = read_sectn(fp, rootdir_sect, sects_per_clust, BPS);
289 for (it = declust;
290 it < declust + (sects_per_clust * BPS / sizeof(*it)); it++) {
291 bool eod = false;
292
293 /*
294 * Simplistic directory traversal; doesn't do any
295 * validation of "MUST" requirements in spec.
296 */
297 switch (it->xde_type) {
298 case XDE_TYPE_EOD:
299 eod = true;
300 break;
301 case XDE_TYPE_VOL_LABEL: {
302 struct exfat_de_label *lde = (void*)it;
303 convert_label(lde->xdel_vol_lbl,
304 lde->xdel_char_cnt, label_out, label_sz);
305 free(declust);
306 return;
307 }
308 }
309
310 if (eod)
311 break;
312 }
313 free(declust);
314 }
315 }
316
317 int
fstyp_exfat(FILE * fp,char * label,size_t size,const char * devpath)318 fstyp_exfat(FILE *fp, char *label, size_t size, const char *devpath)
319 {
320 struct exfat_vbr *ev;
321 uint32_t *cksect;
322 unsigned bytespersec;
323 uint32_t chksum;
324 int error;
325
326 error = 1;
327 cksect = NULL;
328 ev = (struct exfat_vbr *)read_buf(fp, 0, 512);
329 if (ev == NULL || strncmp(ev->ev_fsname, "EXFAT ", 8) != 0)
330 goto out;
331
332 if (ev->ev_log_bytes_per_sect < 9 || ev->ev_log_bytes_per_sect > 12) {
333 warnx("exfat: Invalid BytesPerSectorShift");
334 goto out;
335 }
336
337 bytespersec = (1u << ev->ev_log_bytes_per_sect);
338
339 error = exfat_compute_boot_chksum(fp, MAIN_BOOT_REGION_SECT,
340 bytespersec, &chksum);
341 if (error != 0)
342 goto out;
343
344 cksect = read_sect(fp, MAIN_BOOT_REGION_SECT + SUBREGION_CHKSUM_SECT,
345 bytespersec);
346
347 /*
348 * Technically the entire sector should be full of repeating 4-byte
349 * checksum pattern, but we only verify the first.
350 */
351 if (chksum != le32toh(cksect[0])) {
352 warnx("exfat: Found checksum 0x%08x != computed 0x%08x",
353 le32toh(cksect[0]), chksum);
354 error = 1;
355 goto out;
356 }
357
358 if (show_label)
359 exfat_find_label(fp, ev, bytespersec, label, size);
360
361 out:
362 free(cksect);
363 free(ev);
364 return (error != 0);
365 }
366