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 #ifdef WITH_ICONV 34 #include <iconv.h> 35 #endif 36 #include <stdbool.h> 37 #include <stdint.h> 38 #include <stdio.h> 39 #include <stdlib.h> 40 #include <string.h> 41 42 #include "fstyp.h" 43 44 /* 45 * https://docs.microsoft.com/en-us/windows/win32/fileio/exfat-specification 46 */ 47 48 struct exfat_vbr { 49 char ev_jmp[3]; 50 char ev_fsname[8]; 51 char ev_zeros[53]; 52 uint64_t ev_part_offset; 53 uint64_t ev_vol_length; 54 uint32_t ev_fat_offset; 55 uint32_t ev_fat_length; 56 uint32_t ev_cluster_offset; 57 uint32_t ev_cluster_count; 58 uint32_t ev_rootdir_cluster; 59 uint32_t ev_vol_serial; 60 uint16_t ev_fs_revision; 61 uint16_t ev_vol_flags; 62 uint8_t ev_log_bytes_per_sect; 63 uint8_t ev_log_sect_per_clust; 64 uint8_t ev_num_fats; 65 uint8_t ev_drive_sel; 66 uint8_t ev_percent_used; 67 } __packed; 68 69 struct exfat_dirent { 70 uint8_t xde_type; 71 #define XDE_TYPE_INUSE_MASK 0x80 /* 1=in use */ 72 #define XDE_TYPE_INUSE_SHIFT 7 73 #define XDE_TYPE_CATEGORY_MASK 0x40 /* 0=primary */ 74 #define XDE_TYPE_CATEGORY_SHIFT 6 75 #define XDE_TYPE_IMPORTNC_MASK 0x20 /* 0=critical */ 76 #define XDE_TYPE_IMPORTNC_SHIFT 5 77 #define XDE_TYPE_CODE_MASK 0x1f 78 /* InUse=0, ..., TypeCode=0: EOD. */ 79 #define XDE_TYPE_EOD 0x00 80 #define XDE_TYPE_ALLOC_BITMAP (XDE_TYPE_INUSE_MASK | 0x01) 81 #define XDE_TYPE_UPCASE_TABLE (XDE_TYPE_INUSE_MASK | 0x02) 82 #define XDE_TYPE_VOL_LABEL (XDE_TYPE_INUSE_MASK | 0x03) 83 #define XDE_TYPE_FILE (XDE_TYPE_INUSE_MASK | 0x05) 84 #define XDE_TYPE_VOL_GUID (XDE_TYPE_INUSE_MASK | XDE_TYPE_IMPORTNC_MASK) 85 #define XDE_TYPE_STREAM_EXT (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK) 86 #define XDE_TYPE_FILE_NAME (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | 0x01) 87 #define XDE_TYPE_VENDOR (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | XDE_TYPE_IMPORTNC_MASK) 88 #define XDE_TYPE_VENDOR_ALLOC (XDE_TYPE_INUSE_MASK | XDE_TYPE_CATEGORY_MASK | XDE_TYPE_IMPORTNC_MASK | 0x01) 89 union { 90 uint8_t xde_generic_[19]; 91 struct exde_primary { 92 /* 93 * Count of "secondary" dirents following this one. 94 * 95 * A single logical entity may be composed of a 96 * sequence of several dirents, starting with a primary 97 * one; the rest are secondary dirents. 98 */ 99 uint8_t xde_secondary_count_; 100 uint16_t xde_set_chksum_; 101 uint16_t xde_prim_flags_; 102 uint8_t xde_prim_generic_[14]; 103 } __packed xde_primary_; 104 struct exde_secondary { 105 uint8_t xde_sec_flags_; 106 uint8_t xde_sec_generic_[18]; 107 } __packed xde_secondary_; 108 } u; 109 uint32_t xde_first_cluster; 110 uint64_t xde_data_len; 111 }; 112 #define xde_generic u.xde_generic_ 113 #define xde_secondary_count u.xde_primary_.xde_secondary_count 114 #define xde_set_chksum u.xde_primary_.xde_set_chksum_ 115 #define xde_prim_flags u.xde_primary_.xde_prim_flags_ 116 #define xde_sec_flags u.xde_secondary_.xde_sec_flags_ 117 _Static_assert(sizeof(struct exfat_dirent) == 32, "spec"); 118 119 struct exfat_de_label { 120 uint8_t xdel_type; /* XDE_TYPE_VOL_LABEL */ 121 uint8_t xdel_char_cnt; /* Length of UCS-2 label */ 122 uint16_t xdel_vol_lbl[11]; 123 uint8_t xdel_reserved[8]; 124 }; 125 _Static_assert(sizeof(struct exfat_de_label) == 32, "spec"); 126 127 #define MAIN_BOOT_REGION_SECT 0 128 #define BACKUP_BOOT_REGION_SECT 12 129 130 #define SUBREGION_CHKSUM_SECT 11 131 132 #define FIRST_CLUSTER 2 133 #define BAD_BLOCK_SENTINEL 0xfffffff7u 134 #define END_CLUSTER_SENTINEL 0xffffffffu 135 136 static inline void * 137 read_sectn(FILE *fp, off_t sect, unsigned count, unsigned bytespersec) 138 { 139 return (read_buf(fp, sect * bytespersec, bytespersec * count)); 140 } 141 142 static inline void * 143 read_sect(FILE *fp, off_t sect, unsigned bytespersec) 144 { 145 return (read_sectn(fp, sect, 1, bytespersec)); 146 } 147 148 /* 149 * Compute the byte-by-byte multi-sector checksum of the given boot region 150 * (MAIN or BACKUP), for a given bytespersec (typically 512 or 4096). 151 * 152 * Endian-safe; result is host endian. 153 */ 154 static int 155 exfat_compute_boot_chksum(FILE *fp, unsigned region, unsigned bytespersec, 156 uint32_t *result) 157 { 158 unsigned char *sector; 159 unsigned n, sect; 160 uint32_t checksum; 161 162 checksum = 0; 163 for (sect = 0; sect < 11; sect++) { 164 sector = read_sect(fp, region + sect, bytespersec); 165 if (sector == NULL) 166 return (ENXIO); 167 for (n = 0; n < bytespersec; n++) { 168 if (sect == 0) { 169 switch (n) { 170 case 106: 171 case 107: 172 case 112: 173 continue; 174 } 175 } 176 checksum = ((checksum & 1) ? 0x80000000u : 0u) + 177 (checksum >> 1) + (uint32_t)sector[n]; 178 } 179 free(sector); 180 } 181 182 *result = checksum; 183 return (0); 184 } 185 186 #ifdef WITH_ICONV 187 static void 188 convert_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 */ 243 static uint32_t 244 exfat_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 } 261 262 static void 263 exfat_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 #endif /* WITH_ICONV */ 320 321 int 322 fstyp_exfat(FILE *fp, char *label, size_t size) 323 { 324 struct exfat_vbr *ev; 325 uint32_t *cksect; 326 unsigned bytespersec; 327 uint32_t chksum; 328 int error; 329 330 error = 1; 331 cksect = NULL; 332 ev = (struct exfat_vbr *)read_buf(fp, 0, 512); 333 if (ev == NULL || strncmp(ev->ev_fsname, "EXFAT ", 8) != 0) 334 goto out; 335 336 if (ev->ev_log_bytes_per_sect < 9 || ev->ev_log_bytes_per_sect > 12) { 337 warnx("exfat: Invalid BytesPerSectorShift"); 338 goto out; 339 } 340 341 bytespersec = (1u << ev->ev_log_bytes_per_sect); 342 343 error = exfat_compute_boot_chksum(fp, MAIN_BOOT_REGION_SECT, 344 bytespersec, &chksum); 345 if (error != 0) 346 goto out; 347 348 cksect = read_sect(fp, MAIN_BOOT_REGION_SECT + SUBREGION_CHKSUM_SECT, 349 bytespersec); 350 351 /* 352 * Technically the entire sector should be full of repeating 4-byte 353 * checksum pattern, but we only verify the first. 354 */ 355 if (chksum != le32toh(cksect[0])) { 356 warnx("exfat: Found checksum 0x%08x != computed 0x%08x", 357 le32toh(cksect[0]), chksum); 358 error = 1; 359 goto out; 360 } 361 362 #ifdef WITH_ICONV 363 if (show_label) 364 exfat_find_label(fp, ev, bytespersec, label, size); 365 #else 366 if (show_label) { 367 warnx("label not available without iconv support"); 368 memset(label, 0, size); 369 } 370 #endif 371 372 out: 373 free(cksect); 374 free(ev); 375 return (error != 0); 376 } 377