1 /* 2 * Copyright (C) 2013 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include <inttypes.h> 18 #include <stdio.h> 19 #include <stdlib.h> 20 #include <string.h> 21 #include <unistd.h> 22 #include <fcntl.h> 23 #include <ctype.h> 24 #include <sys/mount.h> 25 #include <sys/stat.h> 26 #include <errno.h> 27 #include <sys/types.h> 28 #include <sys/wait.h> 29 #include <libgen.h> 30 #include <time.h> 31 32 #include <private/android_filesystem_config.h> 33 #include <cutils/properties.h> 34 #include <logwrap/logwrap.h> 35 36 #include "mincrypt/rsa.h" 37 #include "mincrypt/sha.h" 38 #include "mincrypt/sha256.h" 39 40 #include "ext4_sb.h" 41 42 #include "fs_mgr_priv.h" 43 #include "fs_mgr_priv_verity.h" 44 45 #define VERITY_METADATA_SIZE 32768 46 #define VERITY_METADATA_MAGIC_NUMBER 0xb001b001 47 #define VERITY_TABLE_RSA_KEY "/verity_key" 48 49 extern struct fs_info info; 50 51 static RSAPublicKey *load_key(char *path) 52 { 53 FILE *f; 54 RSAPublicKey *key; 55 56 key = malloc(sizeof(RSAPublicKey)); 57 if (!key) { 58 ERROR("Can't malloc key\n"); 59 return NULL; 60 } 61 62 f = fopen(path, "r"); 63 if (!f) { 64 ERROR("Can't open '%s'\n", path); 65 free(key); 66 return NULL; 67 } 68 69 if (!fread(key, sizeof(*key), 1, f)) { 70 ERROR("Could not read key!"); 71 fclose(f); 72 free(key); 73 return NULL; 74 } 75 76 if (key->len != RSANUMWORDS) { 77 ERROR("Invalid key length %d\n", key->len); 78 fclose(f); 79 free(key); 80 return NULL; 81 } 82 83 fclose(f); 84 return key; 85 } 86 87 static int verify_table(char *signature, char *table, int table_length) 88 { 89 RSAPublicKey *key; 90 uint8_t hash_buf[SHA_DIGEST_SIZE]; 91 int retval = -1; 92 93 // Hash the table 94 SHA_hash((uint8_t*)table, table_length, hash_buf); 95 96 // Now get the public key from the keyfile 97 key = load_key(VERITY_TABLE_RSA_KEY); 98 if (!key) { 99 ERROR("Couldn't load verity keys"); 100 goto out; 101 } 102 103 // verify the result 104 if (!RSA_verify(key, 105 (uint8_t*) signature, 106 RSANUMBYTES, 107 (uint8_t*) hash_buf, 108 SHA_DIGEST_SIZE)) { 109 ERROR("Couldn't verify table."); 110 goto out; 111 } 112 113 retval = 0; 114 115 out: 116 free(key); 117 return retval; 118 } 119 120 static int get_target_device_size(char *blk_device, uint64_t *device_size) 121 { 122 int data_device; 123 struct ext4_super_block sb; 124 struct fs_info info = {0}; 125 126 data_device = open(blk_device, O_RDONLY); 127 if (data_device < 0) { 128 ERROR("Error opening block device (%s)", strerror(errno)); 129 return -1; 130 } 131 132 if (lseek64(data_device, 1024, SEEK_SET) < 0) { 133 ERROR("Error seeking to superblock"); 134 close(data_device); 135 return -1; 136 } 137 138 if (read(data_device, &sb, sizeof(sb)) != sizeof(sb)) { 139 ERROR("Error reading superblock"); 140 close(data_device); 141 return -1; 142 } 143 144 ext4_parse_sb(&sb, &info); 145 *device_size = info.len; 146 147 close(data_device); 148 return 0; 149 } 150 151 static int read_verity_metadata(char *block_device, char **signature, char **table) 152 { 153 unsigned magic_number; 154 unsigned table_length; 155 uint64_t device_length; 156 int protocol_version; 157 FILE *device; 158 int retval = -1; 159 160 device = fopen(block_device, "r"); 161 if (!device) { 162 ERROR("Could not open block device %s (%s).\n", block_device, strerror(errno)); 163 goto out; 164 } 165 166 // find the start of the verity metadata 167 if (get_target_device_size(block_device, &device_length) < 0) { 168 ERROR("Could not get target device size.\n"); 169 goto out; 170 } 171 if (fseek(device, device_length, SEEK_SET) < 0) { 172 ERROR("Could not seek to start of verity metadata block.\n"); 173 goto out; 174 } 175 176 // check the magic number 177 if (!fread(&magic_number, sizeof(int), 1, device)) { 178 ERROR("Couldn't read magic number!\n"); 179 goto out; 180 } 181 if (magic_number != VERITY_METADATA_MAGIC_NUMBER) { 182 ERROR("Couldn't find verity metadata at offset %"PRIu64"!\n", device_length); 183 goto out; 184 } 185 186 // check the protocol version 187 if (!fread(&protocol_version, sizeof(int), 1, device)) { 188 ERROR("Couldn't read verity metadata protocol version!\n"); 189 goto out; 190 } 191 if (protocol_version != 0) { 192 ERROR("Got unknown verity metadata protocol version %d!\n", protocol_version); 193 goto out; 194 } 195 196 // get the signature 197 *signature = (char*) malloc(RSANUMBYTES * sizeof(char)); 198 if (!*signature) { 199 ERROR("Couldn't allocate memory for signature!\n"); 200 goto out; 201 } 202 if (!fread(*signature, RSANUMBYTES, 1, device)) { 203 ERROR("Couldn't read signature from verity metadata!\n"); 204 free(*signature); 205 goto out; 206 } 207 208 // get the size of the table 209 if (!fread(&table_length, sizeof(int), 1, device)) { 210 ERROR("Couldn't get the size of the verity table from metadata!\n"); 211 free(*signature); 212 goto out; 213 } 214 215 // get the table + null terminator 216 table_length += 1; 217 *table = malloc(table_length); 218 if(!*table) { 219 ERROR("Couldn't allocate memory for verity table!\n"); 220 goto out; 221 } 222 if (!fgets(*table, table_length, device)) { 223 ERROR("Couldn't read the verity table from metadata!\n"); 224 free(*table); 225 free(*signature); 226 goto out; 227 } 228 229 retval = 0; 230 231 out: 232 if (device) 233 fclose(device); 234 return retval; 235 } 236 237 static void verity_ioctl_init(struct dm_ioctl *io, char *name, unsigned flags) 238 { 239 memset(io, 0, DM_BUF_SIZE); 240 io->data_size = DM_BUF_SIZE; 241 io->data_start = sizeof(struct dm_ioctl); 242 io->version[0] = 4; 243 io->version[1] = 0; 244 io->version[2] = 0; 245 io->flags = flags | DM_READONLY_FLAG; 246 if (name) { 247 strlcpy(io->name, name, sizeof(io->name)); 248 } 249 } 250 251 static int create_verity_device(struct dm_ioctl *io, char *name, int fd) 252 { 253 verity_ioctl_init(io, name, 1); 254 if (ioctl(fd, DM_DEV_CREATE, io)) { 255 ERROR("Error creating device mapping (%s)", strerror(errno)); 256 return -1; 257 } 258 return 0; 259 } 260 261 static int get_verity_device_name(struct dm_ioctl *io, char *name, int fd, char **dev_name) 262 { 263 verity_ioctl_init(io, name, 0); 264 if (ioctl(fd, DM_DEV_STATUS, io)) { 265 ERROR("Error fetching verity device number (%s)", strerror(errno)); 266 return -1; 267 } 268 int dev_num = (io->dev & 0xff) | ((io->dev >> 12) & 0xfff00); 269 if (asprintf(dev_name, "/dev/block/dm-%u", dev_num) < 0) { 270 ERROR("Error getting verity block device name (%s)", strerror(errno)); 271 return -1; 272 } 273 return 0; 274 } 275 276 static int load_verity_table(struct dm_ioctl *io, char *name, char *blockdev, int fd, char *table) 277 { 278 char *verity_params; 279 char *buffer = (char*) io; 280 uint64_t device_size = 0; 281 282 if (get_target_device_size(blockdev, &device_size) < 0) { 283 return -1; 284 } 285 286 verity_ioctl_init(io, name, DM_STATUS_TABLE_FLAG); 287 288 struct dm_target_spec *tgt = (struct dm_target_spec *) &buffer[sizeof(struct dm_ioctl)]; 289 290 // set tgt arguments here 291 io->target_count = 1; 292 tgt->status=0; 293 tgt->sector_start=0; 294 tgt->length=device_size/512; 295 strcpy(tgt->target_type, "verity"); 296 297 // build the verity params here 298 verity_params = buffer + sizeof(struct dm_ioctl) + sizeof(struct dm_target_spec); 299 if (sprintf(verity_params, "%s", table) < 0) { 300 return -1; 301 } 302 303 // set next target boundary 304 verity_params += strlen(verity_params) + 1; 305 verity_params = (char*) (((unsigned long)verity_params + 7) & ~8); 306 tgt->next = verity_params - buffer; 307 308 // send the ioctl to load the verity table 309 if (ioctl(fd, DM_TABLE_LOAD, io)) { 310 ERROR("Error loading verity table (%s)", strerror(errno)); 311 return -1; 312 } 313 314 return 0; 315 } 316 317 static int resume_verity_table(struct dm_ioctl *io, char *name, int fd) 318 { 319 verity_ioctl_init(io, name, 0); 320 if (ioctl(fd, DM_DEV_SUSPEND, io)) { 321 ERROR("Error activating verity device (%s)", strerror(errno)); 322 return -1; 323 } 324 return 0; 325 } 326 327 static int test_access(char *device) { 328 int tries = 25; 329 while (tries--) { 330 if (!access(device, F_OK) || errno != ENOENT) { 331 return 0; 332 } 333 usleep(40 * 1000); 334 } 335 return -1; 336 } 337 338 static int set_verified_property(char *name) { 339 int ret; 340 char *key; 341 ret = asprintf(&key, "partition.%s.verified", name); 342 if (ret < 0) { 343 ERROR("Error formatting verified property"); 344 return ret; 345 } 346 ret = PROP_NAME_MAX - strlen(key); 347 if (ret < 0) { 348 ERROR("Verified property name is too long"); 349 return -1; 350 } 351 ret = property_set(key, "1"); 352 if (ret < 0) 353 ERROR("Error setting verified property %s: %d", key, ret); 354 free(key); 355 return ret; 356 } 357 358 int fs_mgr_setup_verity(struct fstab_rec *fstab) { 359 360 int retval = -1; 361 362 char *verity_blk_name; 363 char *verity_table; 364 char *verity_table_signature; 365 366 char buffer[DM_BUF_SIZE]; 367 struct dm_ioctl *io = (struct dm_ioctl *) buffer; 368 char *mount_point = basename(fstab->mount_point); 369 370 // set the dm_ioctl flags 371 io->flags |= 1; 372 io->target_count = 1; 373 374 // check to ensure that the verity device is ext4 375 // TODO: support non-ext4 filesystems 376 if (strcmp(fstab->fs_type, "ext4")) { 377 ERROR("Cannot verify non-ext4 device (%s)", fstab->fs_type); 378 return retval; 379 } 380 381 // get the device mapper fd 382 int fd; 383 if ((fd = open("/dev/device-mapper", O_RDWR)) < 0) { 384 ERROR("Error opening device mapper (%s)", strerror(errno)); 385 return retval; 386 } 387 388 // create the device 389 if (create_verity_device(io, mount_point, fd) < 0) { 390 ERROR("Couldn't create verity device!"); 391 goto out; 392 } 393 394 // get the name of the device file 395 if (get_verity_device_name(io, mount_point, fd, &verity_blk_name) < 0) { 396 ERROR("Couldn't get verity device number!"); 397 goto out; 398 } 399 400 // read the verity block at the end of the block device 401 if (read_verity_metadata(fstab->blk_device, 402 &verity_table_signature, 403 &verity_table) < 0) { 404 goto out; 405 } 406 407 // verify the signature on the table 408 if (verify_table(verity_table_signature, 409 verity_table, 410 strlen(verity_table)) < 0) { 411 goto out; 412 } 413 414 // load the verity mapping table 415 if (load_verity_table(io, mount_point, fstab->blk_device, fd, verity_table) < 0) { 416 goto out; 417 } 418 419 // activate the device 420 if (resume_verity_table(io, mount_point, fd) < 0) { 421 goto out; 422 } 423 424 // assign the new verity block device as the block device 425 free(fstab->blk_device); 426 fstab->blk_device = verity_blk_name; 427 428 // make sure we've set everything up properly 429 if (test_access(fstab->blk_device) < 0) { 430 goto out; 431 } 432 433 // set the property indicating that the partition is verified 434 retval = set_verified_property(mount_point); 435 436 out: 437 close(fd); 438 return retval; 439 } 440
