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/cdefs.h> 28 #include <sys/param.h> 29 #include <sys/endian.h> 30 31 #include <assert.h> 32 #include <err.h> 33 #include <errno.h> 34 #ifdef WITH_ICONV 35 #include <iconv.h> 36 #endif 37 #include <stdbool.h> 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 49 struct 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; 57 uint32_t ev_cluster_offset; 58 uint32_t ev_cluster_count; 59 uint32_t ev_rootdir_cluster; 60 uint32_t ev_vol_serial; 61 uint16_t ev_fs_revision; 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 70 struct 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 }; 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"); 119 120 struct 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 }; 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 136 137 static inline void * 138 read_sectn(FILE *fp, off_t sect, unsigned count, unsigned bytespersec) 139 { 140 return (read_buf(fp, sect * bytespersec, bytespersec * count)); 141 } 142 143 static inline void * 144 read_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 */ 155 static int 156 exfat_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 } 186 187 #ifdef WITH_ICONV 188 static void 189 convert_label(const uint16_t *ucs2label /* LE */, unsigned ucs2len, char 190 *label_out, size_t label_sz) 191 { 192 const char *label; 193 char *label_out_orig; 194 iconv_t cd; 195 size_t srcleft, rc; 196 197 /* Currently hardcoded in fstyp.c as 256 or so. */ 198 assert(label_sz > 1); 199 200 if (ucs2len == 0) { 201 /* 202 * Kind of seems bogus, but the spec allows an empty label 203 * entry with the same meaning as no label. 204 */ 205 return; 206 } 207 208 if (ucs2len > 11) { 209 warnx("exfat: Bogus volume label length: %u", ucs2len); 210 return; 211 } 212 213 /* dstname="" means convert to the current locale. */ 214 cd = iconv_open("", EXFAT_ENC); 215 if (cd == (iconv_t)-1) { 216 warn("exfat: Could not open iconv"); 217 return; 218 } 219 220 label_out_orig = label_out; 221 222 /* Dummy up the byte pointer and byte length iconv's API wants. */ 223 label = (const void *)ucs2label; 224 srcleft = ucs2len * sizeof(*ucs2label); 225 226 rc = iconv(cd, __DECONST(char **, &label), &srcleft, &label_out, 227 &label_sz); 228 if (rc == (size_t)-1) { 229 warn("exfat: iconv()"); 230 *label_out_orig = '\0'; 231 } else { 232 /* NUL-terminate result (iconv advances label_out). */ 233 if (label_sz == 0) 234 label_out--; 235 *label_out = '\0'; 236 } 237 238 iconv_close(cd); 239 } 240 241 /* 242 * Using the FAT table, look up the next cluster in this chain. 243 */ 244 static uint32_t 245 exfat_fat_next(FILE *fp, const struct exfat_vbr *ev, unsigned BPS, 246 uint32_t cluster) 247 { 248 uint32_t fat_offset_sect, clsect, clsectoff; 249 uint32_t *fatsect, nextclust; 250 251 fat_offset_sect = le32toh(ev->ev_fat_offset); 252 clsect = fat_offset_sect + (cluster / (BPS / sizeof(cluster))); 253 clsectoff = (cluster % (BPS / sizeof(cluster))); 254 255 /* XXX This is pretty wasteful without a block cache for the FAT. */ 256 fatsect = read_sect(fp, clsect, BPS); 257 nextclust = le32toh(fatsect[clsectoff]); 258 free(fatsect); 259 260 return (nextclust); 261 } 262 263 static void 264 exfat_find_label(FILE *fp, const struct exfat_vbr *ev, unsigned BPS, 265 char *label_out, size_t label_sz) 266 { 267 uint32_t rootdir_cluster, sects_per_clust, cluster_offset_sect; 268 off_t rootdir_sect; 269 struct exfat_dirent *declust, *it; 270 271 cluster_offset_sect = le32toh(ev->ev_cluster_offset); 272 rootdir_cluster = le32toh(ev->ev_rootdir_cluster); 273 sects_per_clust = (1u << ev->ev_log_sect_per_clust); 274 275 if (rootdir_cluster < FIRST_CLUSTER) { 276 warnx("%s: invalid rootdir cluster %u < %d", __func__, 277 rootdir_cluster, FIRST_CLUSTER); 278 return; 279 } 280 281 282 for (; rootdir_cluster != END_CLUSTER_SENTINEL; 283 rootdir_cluster = exfat_fat_next(fp, ev, BPS, rootdir_cluster)) { 284 if (rootdir_cluster == BAD_BLOCK_SENTINEL) { 285 warnx("%s: Bogus bad block in root directory chain", 286 __func__); 287 return; 288 } 289 290 rootdir_sect = (rootdir_cluster - FIRST_CLUSTER) * 291 sects_per_clust + cluster_offset_sect; 292 declust = read_sectn(fp, rootdir_sect, sects_per_clust, BPS); 293 for (it = declust; 294 it < declust + (sects_per_clust * BPS / sizeof(*it)); it++) { 295 bool eod = false; 296 297 /* 298 * Simplistic directory traversal; doesn't do any 299 * validation of "MUST" requirements in spec. 300 */ 301 switch (it->xde_type) { 302 case XDE_TYPE_EOD: 303 eod = true; 304 break; 305 case XDE_TYPE_VOL_LABEL: { 306 struct exfat_de_label *lde = (void*)it; 307 convert_label(lde->xdel_vol_lbl, 308 lde->xdel_char_cnt, label_out, label_sz); 309 free(declust); 310 return; 311 } 312 } 313 314 if (eod) 315 break; 316 } 317 free(declust); 318 } 319 } 320 #endif /* WITH_ICONV */ 321 322 int 323 fstyp_exfat(FILE *fp, char *label, size_t size) 324 { 325 struct exfat_vbr *ev; 326 uint32_t *cksect; 327 unsigned bytespersec; 328 uint32_t chksum; 329 int error; 330 331 error = 1; 332 cksect = NULL; 333 ev = (struct exfat_vbr *)read_buf(fp, 0, 512); 334 if (ev == NULL || strncmp(ev->ev_fsname, "EXFAT ", 8) != 0) 335 goto out; 336 337 if (ev->ev_log_bytes_per_sect < 9 || ev->ev_log_bytes_per_sect > 12) { 338 warnx("exfat: Invalid BytesPerSectorShift"); 339 goto out; 340 } 341 342 bytespersec = (1u << ev->ev_log_bytes_per_sect); 343 344 error = exfat_compute_boot_chksum(fp, MAIN_BOOT_REGION_SECT, 345 bytespersec, &chksum); 346 if (error != 0) 347 goto out; 348 349 cksect = read_sect(fp, MAIN_BOOT_REGION_SECT + SUBREGION_CHKSUM_SECT, 350 bytespersec); 351 352 /* 353 * Technically the entire sector should be full of repeating 4-byte 354 * checksum pattern, but we only verify the first. 355 */ 356 if (chksum != le32toh(cksect[0])) { 357 warnx("exfat: Found checksum 0x%08x != computed 0x%08x", 358 le32toh(cksect[0]), chksum); 359 error = 1; 360 goto out; 361 } 362 363 #ifdef WITH_ICONV 364 if (show_label) 365 exfat_find_label(fp, ev, bytespersec, label, size); 366 #else 367 if (show_label) { 368 warnx("label not available without iconv support"); 369 memset(label, 0, size); 370 } 371 #endif 372 373 out: 374 free(cksect); 375 free(ev); 376 return (error != 0); 377 } 378