lib/verity/verity_hash.c

   1 /*
   2  * dm-verity volume handling
   3  *
   4  * Copyright (C) 2012, Red Hat, Inc. All rights reserved.
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * version 2 as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18  */
  19
  20 #include <errno.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <stdint.h>
  25
  26 #include "verity.h"
  27 #include "internal.h"
  28
  29 static unsigned get_bits_up(unsigned u)
  30 {
  31         unsigned i = 0;
  32         while ((1 << i) < u)
  33                 i++;
  34         return i;
  35 }
  36
  37 static unsigned get_bits_down(unsigned u)
  38 {
  39         unsigned i = 0;
  40         while ((u >> i) > 1)
  41                 i++;
  42         return i;
  43 }
  44
  45 static int verify_zero(struct crypt_device *cd, FILE *wr, unsigned bytes)
  46 {
  47         unsigned i;
  48         char block[bytes];
  49
  50         if (fread(block, bytes, 1, wr) != 1)
  51                 return -EIO;
  52         for (i = 0; i < bytes; i++)
  53                 if (block[i]) {
  54                         log_err(cd, "spare area is not zeroed at position %lld\n",
  55                                 (long long)ftello(wr) - bytes);
  56                         return -EPERM;
  57                 }
  58         return 0;
  59 }
  60
  61 static int verify_hash_block(const char *hash_name, int version,
  62                               char *hash, size_t hash_size,
  63                               const char *data, size_t data_size,
  64                               const char *salt, size_t salt_size)
  65 {
  66         struct crypt_hash *ctx = NULL;
  67         int r;
  68
  69         if (crypt_hash_init(&ctx, hash_name))
  70                 return -EINVAL;
  71
  72         if (version == 1 && (r = crypt_hash_write(ctx, salt, salt_size)))
  73                 goto out;
  74
  75         if ((r = crypt_hash_write(ctx, data, data_size)))
  76                 goto out;
  77
  78         if (version == 0 && (r = crypt_hash_write(ctx, salt, salt_size)))
  79                 goto out;
  80
  81         r = crypt_hash_final(ctx, hash, hash_size);
  82 out:
  83         crypt_hash_destroy(ctx);
  84         return r;
  85 }
  86
  87 static int create_or_verify(struct crypt_device *cd, FILE *rd, FILE *wr,
  88                                    off_t data_block, int data_block_size,
  89                                    off_t hash_block, int hash_block_size,
  90                                    off_t blocks, int version,
  91                                    const char *hash_name, int verify,
  92                                    char *calculated_digest, unsigned digest_size,
  93                                    const char *salt, unsigned salt_size)
  94 {
  95         char left_block[hash_block_size];
  96         char data_buffer[data_block_size];
  97         char read_digest[digest_size];
  98         off_t hash_per_block = 1 << get_bits_down(hash_block_size / digest_size);
  99         off_t blocks_to_write = (blocks + hash_per_block - 1) / hash_per_block;
 100         unsigned i, left_bytes;
 101         off_t digest_size_full = 1 << get_bits_up(digest_size);
 102         int r;
 103         unsigned long long pos_rd = (unsigned long long)data_block * data_block_size;
 104         unsigned long long pos_wr = (unsigned long long)hash_block * hash_block_size;
 105
 106         if (fseeko(rd, pos_rd, SEEK_SET))
 107                 return -EIO;
 108
 109         if (wr && fseeko(wr, pos_wr, SEEK_SET))
 110                 return -EIO;
 111
 112         memset(left_block, 0, hash_block_size);
 113         while (blocks_to_write--) {
 114                 left_bytes = hash_block_size;
 115                 for (i = 0; i < hash_per_block; i++) {
 116                         if (!blocks)
 117                                 break;
 118                         blocks--;
 119                         if (fread(data_buffer, data_block_size, 1, rd) != 1)
 120                                 return -EIO;
 121
 122                         if (verify_hash_block(hash_name, version,
 123                                         calculated_digest, digest_size,
 124                                         data_buffer, data_block_size,
 125                                         salt, salt_size))
 126                                 return -EINVAL;
 127
 128                         if (!wr)
 129                                 break;
 130                         if (verify) {
 131                                 if (fread(read_digest, digest_size, 1, wr) != 1)
 132                                         return -EIO;
 133                                 if (memcmp(read_digest, calculated_digest, digest_size)) {
 134                                         log_err(cd, "verification failed at position %lld\n",
 135                                                 (long long)ftello(rd) - data_block_size);
 136                                         return -EPERM;
 137                                 }
 138                         } else {
 139                                 if (fwrite(calculated_digest, digest_size, 1, wr) != 1)
 140                                         return -EIO;
 141                         }
 142                         if (version == 0) {
 143                                 left_bytes -= digest_size;
 144                         } else {
 145                                 if (digest_size_full - digest_size) {
 146                                         if (verify) {
 147                                                 r = verify_zero(cd, wr, digest_size_full - digest_size);
 148                                                 if (r)
 149                                                         return r;
 150                                         } else if (fwrite(left_block, digest_size_full - digest_size, 1, wr) != 1)
 151                                                 return -EIO;
 152                                 }
 153                                 left_bytes -= digest_size_full;
 154                         }
 155                 }
 156                 if (wr && left_bytes) {
 157                         if (verify) {
 158                                 r = verify_zero(cd , wr, left_bytes);
 159                                 if (r)
 160                                         return r;
 161                         } else if (fwrite(left_block, left_bytes, 1, wr) != 1)
 162                                 return -EIO;
 163                 }
 164         }
 165
 166         return 0;
 167 }
 168
 169 static int VERITY_create_or_verify_hash(struct crypt_device *cd,
 170         int verify,
 171         int version,
 172         const char *hash_name,
 173         const char *hash_device,
 174         const char *data_device,
 175         int hash_block_size,
 176         int data_block_size,
 177         off_t data_blocks,
 178         long long hash_position,
 179         char *root_hash,
 180         unsigned digest_size,
 181         const char *salt,
 182         unsigned salt_size)
 183 {
 184         static FILE *data_file = NULL;
 185         static FILE *hash_file = NULL, *hash_file_2;
 186
 187         int i, r;
 188         char calculated_digest[digest_size];
 189         off_t hash_level_block[VERITY_MAX_LEVELS];
 190         off_t hash_level_size[VERITY_MAX_LEVELS];
 191         off_t data_file_blocks;
 192         uint64_t data_device_size;
 193         unsigned long long hash_per_block, hash_per_block_bits;
 194         unsigned levels;
 195
 196         log_dbg("Userspace hash %s %s, data device %s, data blocks %u, hash device %s, offset %u.",
 197                 verify ? "verification" : "creation", hash_name, data_device,
 198                 (unsigned)data_blocks, hash_device, (unsigned)hash_position);
 199
 200         if (!data_blocks) {
 201                 r = device_size(data_device, &data_device_size);
 202                 if (r < 0)
 203                         return r;
 204
 205                 data_file_blocks = data_device_size / data_block_size;
 206         } else
 207                 data_file_blocks = data_blocks;
 208
 209         hash_per_block_bits = get_bits_down(hash_block_size / digest_size);
 210         hash_per_block = 1 << hash_per_block_bits;
 211         if (!hash_per_block_bits) {
 212                 log_err(cd, "at least two hashes must fit in a hash file block\n");
 213                 return -EINVAL;
 214         }
 215
 216         levels = 0;
 217         if (data_file_blocks) {
 218                 while (hash_per_block_bits * levels < 64 &&
 219                        (unsigned long long)(data_file_blocks - 1) >>
 220                        (hash_per_block_bits * levels))
 221                         levels++;
 222         }
 223
 224         if (levels > VERITY_MAX_LEVELS) {
 225                 log_err(cd, "too many tree levels\n");
 226                 return -EINVAL;
 227         }
 228
 229         for (i = levels - 1; i >= 0; i--) {
 230                 off_t s;
 231                 hash_level_block[i] = hash_position;
 232                 // verity position of block data_file_blocks at level i
 233                 s = data_file_blocks >> (i * hash_per_block_bits);
 234                 s = (s + hash_per_block - 1) / hash_per_block;
 235                 hash_level_size[i] = s;
 236                 if (hash_position + s < hash_position ||
 237                     (off_t)(hash_position + s) < 0 ||
 238                     (off_t)(hash_position + s) != hash_position + s) {
 239                         log_err(cd, "hash device offset overflow\n");
 240                         return -EINVAL;
 241                 }
 242                 hash_position += s;
 243         }
 244
 245         data_file = fopen(data_device, "r");
 246         if (!data_file) {
 247                 log_err(cd, "Cannot open %s.\n", data_device);
 248                 r = -EIO;
 249                 goto out;
 250         }
 251
 252         hash_file = fopen(hash_device, verify ? "r" : "r+");
 253         if (!hash_file) {
 254                 log_err(cd, "Cannot open %s.\n", hash_device);
 255                 r = -EIO;
 256                 goto out;
 257         }
 258
 259         memset(calculated_digest, 0, digest_size);
 260
 261         for (i = 0; i < levels; i++) {
 262                 if (!i) {
 263                         r = create_or_verify(cd, data_file, hash_file,
 264                                                     0, data_block_size,
 265                                                     hash_level_block[i], hash_block_size,
 266                                                     data_file_blocks, version, hash_name, verify,
 267                                                     calculated_digest, digest_size, salt, salt_size);
 268                         if (r)
 269                                 goto out;
 270                 } else {
 271                         hash_file_2 = fopen(hash_device, "r");
 272                         if (!hash_file_2) {
 273                                 r = -EIO;
 274                                 goto out;
 275                         }
 276                         r = create_or_verify(cd, hash_file_2, hash_file,
 277                                                     hash_level_block[i - 1], hash_block_size,
 278                                                     hash_level_block[i], hash_block_size,
 279                                                     hash_level_size[i - 1], version, hash_name, verify,
 280                                                     calculated_digest, digest_size, salt, salt_size);
 281                         fclose(hash_file_2);
 282                         if (r)
 283                                 goto out;
 284                 }
 285         }
 286
 287         if (levels)
 288                 r = create_or_verify(cd, hash_file, NULL,
 289                                             hash_level_block[levels - 1], hash_block_size,
 290                                             0, 0,
 291                                             1, version, hash_name, verify,
 292                                             calculated_digest, digest_size, salt, salt_size);
 293         else
 294                 r = create_or_verify(cd, data_file, NULL,
 295                                             0, data_block_size,
 296                                             0, 0,
 297                                             data_file_blocks, version, hash_name, verify,
 298                                             calculated_digest, digest_size, salt, salt_size);
 299
 300         if (r) {
 301                 log_err(cd, "Hash of data area verification failed.\n");
 302                 goto out;
 303         } else
 304                 log_dbg("Hash of data area successfully verified.");
 305
 306         /* root hash verification */
 307         if (verify) {
 308                 r = memcmp(root_hash, calculated_digest, digest_size) ? -EPERM : 0;
 309                 if (r)
 310                         log_err(cd, "Root hash verification failed.\n");
 311                 else
 312                         log_dbg("Root hash successfully verified.");
 313         } else {
 314                 fsync(fileno(hash_file));
 315                 memcpy(root_hash, calculated_digest, digest_size);
 316         }
 317 out:
 318         if (data_file)
 319                 fclose(data_file);
 320         if (hash_file)
 321                 fclose(hash_file);
 322         return r;
 323 }
 324
 325 /* Verify verity device using userspace crypto backend */
 326 int VERITY_verify(struct crypt_device *cd,
 327                   struct crypt_params_verity *verity_hdr,
 328                   const char *data_device,
 329                   const char *hash_device,
 330                   const char *root_hash,
 331                   size_t root_hash_size)
 332 {
 333         int r = VERITY_create_or_verify_hash(cd, 1,
 334                 verity_hdr->version,
 335                 verity_hdr->hash_name,
 336                 hash_device,
 337                 data_device,
 338                 verity_hdr->hash_block_size,
 339                 verity_hdr->data_block_size,
 340                 verity_hdr->data_size,
 341                 VERITY_hash_offset_block(verity_hdr),
 342                 CONST_CAST(char*)root_hash,
 343                 root_hash_size,
 344                 verity_hdr->salt,
 345                 verity_hdr->salt_size);
 346
 347         if (r == -EPERM)
 348                 log_err(cd, "Userspace hash verification failed.\n");
 349
 350         return r;
 351 }
 352
 353 int VERITY_create(struct crypt_device *cd,
 354                   struct crypt_params_verity *verity_hdr,
 355                   const char *data_device,
 356                   const char *hash_device,
 357                   char *root_hash,
 358                   size_t root_hash_size)
 359 {
 360         if (verity_hdr->salt_size > VERITY_MAX_SALT_SIZE)
 361                 return -EINVAL;
 362
 363         return VERITY_create_or_verify_hash(cd, 0,
 364                 verity_hdr->version,
 365                 verity_hdr->hash_name,
 366                 hash_device,
 367                 data_device,
 368                 verity_hdr->hash_block_size,
 369                 verity_hdr->data_block_size,
 370                 verity_hdr->data_size,
 371                 VERITY_hash_offset_block(verity_hdr),
 372                 root_hash,
 373                 root_hash_size,
 374                 verity_hdr->salt,
 375                 verity_hdr->salt_size);
 376 }