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 #define VERITY_MAX_LEVELS       63
  30
  31 static unsigned get_bits_up(size_t u)
  32 {
  33         unsigned i = 0;
  34         while ((1 << i) < u)
  35                 i++;
  36         return i;
  37 }
  38
  39 static unsigned get_bits_down(size_t u)
  40 {
  41         unsigned i = 0;
  42         while ((u >> i) > 1)
  43                 i++;
  44         return i;
  45 }
  46
  47 static int verify_zero(struct crypt_device *cd, FILE *wr, size_t bytes)
  48 {
  49         char block[bytes];
  50         size_t i;
  51
  52         if (fread(block, bytes, 1, wr) != 1) {
  53                 log_dbg("EIO while reading spare area.");
  54                 return -EIO;
  55         }
  56         for (i = 0; i < bytes; i++)
  57                 if (block[i]) {
  58                         log_err(cd, _("Spare area is not zeroed at position %" PRIu64 ".\n"),
  59                                 ftello(wr) - bytes);
  60                         return -EPERM;
  61                 }
  62         return 0;
  63 }
  64
  65 static int verify_hash_block(const char *hash_name, int version,
  66                               char *hash, size_t hash_size,
  67                               const char *data, size_t data_size,
  68                               const char *salt, size_t salt_size)
  69 {
  70         struct crypt_hash *ctx = NULL;
  71         int r;
  72
  73         if (crypt_hash_init(&ctx, hash_name))
  74                 return -EINVAL;
  75
  76         if (version == 1 && (r = crypt_hash_write(ctx, salt, salt_size)))
  77                 goto out;
  78
  79         if ((r = crypt_hash_write(ctx, data, data_size)))
  80                 goto out;
  81
  82         if (version == 0 && (r = crypt_hash_write(ctx, salt, salt_size)))
  83                 goto out;
  84
  85         r = crypt_hash_final(ctx, hash, hash_size);
  86 out:
  87         crypt_hash_destroy(ctx);
  88         return r;
  89 }
  90
  91 static int create_or_verify(struct crypt_device *cd, FILE *rd, FILE *wr,
  92                                    off_t data_block, size_t data_block_size,
  93                                    off_t hash_block, size_t hash_block_size,
  94                                    off_t blocks, int version,
  95                                    const char *hash_name, int verify,
  96                                    char *calculated_digest, size_t digest_size,
  97                                    const char *salt, size_t salt_size)
  98 {
  99         char left_block[hash_block_size];
 100         char data_buffer[data_block_size];
 101         char read_digest[digest_size];
 102         size_t hash_per_block = 1 << get_bits_down(hash_block_size / digest_size);
 103         size_t digest_size_full = 1 << get_bits_up(digest_size);
 104         off_t blocks_to_write = (blocks + hash_per_block - 1) / hash_per_block;
 105         size_t left_bytes;
 106         int i, r;
 107
 108         if (fseeko(rd, data_block * data_block_size, SEEK_SET)) {
 109                 log_dbg("Cannot seek to requested position in data device.");
 110                 return -EIO;
 111         }
 112
 113         if (wr && fseeko(wr, hash_block * hash_block_size, SEEK_SET)) {
 114                 log_dbg("Cannot seek to requested position in hash device.");
 115                 return -EIO;
 116         }
 117
 118         memset(left_block, 0, hash_block_size);
 119         while (blocks_to_write--) {
 120                 left_bytes = hash_block_size;
 121                 for (i = 0; i < hash_per_block; i++) {
 122                         if (!blocks)
 123                                 break;
 124                         blocks--;
 125                         if (fread(data_buffer, data_block_size, 1, rd) != 1) {
 126                                 log_dbg("Cannot read data device block.");
 127                                 return -EIO;
 128                         }
 129
 130                         if (verify_hash_block(hash_name, version,
 131                                         calculated_digest, digest_size,
 132                                         data_buffer, data_block_size,
 133                                         salt, salt_size))
 134                                 return -EINVAL;
 135
 136                         if (!wr)
 137                                 break;
 138                         if (verify) {
 139                                 if (fread(read_digest, digest_size, 1, wr) != 1) {
 140                                         log_dbg("Cannot read digest form hash device.");
 141                                         return -EIO;
 142                                 }
 143                                 if (memcmp(read_digest, calculated_digest, digest_size)) {
 144                                         log_err(cd, _("Verification failed at position %" PRIu64 ".\n"),
 145                                                 ftello(rd) - data_block_size);
 146                                         return -EPERM;
 147                                 }
 148                         } else {
 149                                 if (fwrite(calculated_digest, digest_size, 1, wr) != 1) {
 150                                         log_dbg("Cannot write digest to hash device.");
 151                                         return -EIO;
 152                                 }
 153                         }
 154                         if (version == 0) {
 155                                 left_bytes -= digest_size;
 156                         } else {
 157                                 if (digest_size_full - digest_size) {
 158                                         if (verify) {
 159                                                 r = verify_zero(cd, wr, digest_size_full - digest_size);
 160                                                 if (r)
 161                                                         return r;
 162                                         } else if (fwrite(left_block, digest_size_full - digest_size, 1, wr) != 1) {
 163                                                 log_dbg("Cannot write spare area to hash device.");
 164                                                 return -EIO;
 165                                         }
 166                                 }
 167                                 left_bytes -= digest_size_full;
 168                         }
 169                 }
 170                 if (wr && left_bytes) {
 171                         if (verify) {
 172                                 r = verify_zero(cd , wr, left_bytes);
 173                                 if (r)
 174                                         return r;
 175                         } else if (fwrite(left_block, left_bytes, 1, wr) != 1) {
 176                                 log_dbg("Cannot write remaining spare area to hash device.");
 177                                 return -EIO;
 178                         }
 179                 }
 180         }
 181
 182         return 0;
 183 }
 184
 185 static int VERITY_create_or_verify_hash(struct crypt_device *cd,
 186         int verify,
 187         int version,
 188         const char *hash_name,
 189         const char *hash_device,
 190         const char *data_device,
 191         size_t hash_block_size,
 192         size_t data_block_size,
 193         off_t data_blocks,
 194         off_t hash_position,
 195         char *root_hash,
 196         size_t digest_size,
 197         const char *salt,
 198         size_t salt_size)
 199 {
 200         char calculated_digest[digest_size];
 201         FILE *data_file = NULL;
 202         FILE *hash_file = NULL, *hash_file_2;
 203         off_t hash_level_block[VERITY_MAX_LEVELS];
 204         off_t hash_level_size[VERITY_MAX_LEVELS];
 205         off_t data_file_blocks, s;
 206         size_t hash_per_block, hash_per_block_bits;
 207         uint64_t data_device_size = 0, hash_device_size = 0;
 208         int levels, i, r;
 209
 210         log_dbg("Hash %s %s, data device %s, data blocks %" PRIu64
 211                 ", hash_device %s, offset %" PRIu64 ".",
 212                 verify ? "verification" : "creation", hash_name,
 213                 data_device, data_blocks, hash_device, hash_position);
 214
 215         if (!data_blocks) {
 216                 r = device_size(data_device, &data_device_size);
 217                 if (r < 0)
 218                         return r;
 219
 220                 data_file_blocks = data_device_size / data_block_size;
 221         } else {
 222                 data_device_size = data_blocks * data_block_size;
 223                 data_file_blocks = data_blocks;
 224         }
 225
 226         hash_per_block_bits = get_bits_down(hash_block_size / digest_size);
 227         hash_per_block = 1 << hash_per_block_bits;
 228         if (!hash_per_block_bits)
 229                 return -EINVAL;
 230
 231         levels = 0;
 232         if (data_file_blocks) {
 233                 while (hash_per_block_bits * levels < 64 &&
 234                        (data_file_blocks - 1) >> (hash_per_block_bits * levels))
 235                         levels++;
 236         }
 237         log_dbg("Using %d hash levels.", levels);
 238
 239         if (levels > VERITY_MAX_LEVELS) {
 240                 log_err(cd, _("Too many tree levels for verity volume.\n"));
 241                 return -EINVAL;
 242         }
 243
 244         for (i = levels - 1; i >= 0; i--) {
 245                 hash_level_block[i] = hash_position;
 246                 // verity position of block data_file_blocks at level i
 247                 s = data_file_blocks >> (i * hash_per_block_bits);
 248                 s = (s + hash_per_block - 1) / hash_per_block;
 249                 hash_level_size[i] = s;
 250                 if (hash_position + s < hash_position ||
 251                     (hash_position + s) < 0 ||
 252                     (hash_position + s) != hash_position + s) {
 253                         log_dbg("Hash device offset overflow.");
 254                         return -EINVAL;
 255                 }
 256                 hash_position += s;
 257         }
 258         hash_device_size = hash_position * hash_block_size;
 259
 260         log_dbg("Data device size required: %" PRIu64 " bytes.",
 261                 data_device_size);
 262         data_file = fopen(data_device, "r");
 263         if (!data_file) {
 264                 log_err(cd, _("Cannot open device %s.\n"), data_device);
 265                 r = -EIO;
 266                 goto out;
 267         }
 268
 269         log_dbg("Hash device size required: %" PRIu64 " bytes.",
 270                 hash_device_size);
 271         hash_file = fopen(hash_device, verify ? "r" : "r+");
 272         if (!hash_file) {
 273                 log_err(cd, _("Cannot open device %s.\n"), hash_device);
 274                 r = -EIO;
 275                 goto out;
 276         }
 277
 278         memset(calculated_digest, 0, digest_size);
 279
 280         for (i = 0; i < levels; i++) {
 281                 if (!i) {
 282                         r = create_or_verify(cd, data_file, hash_file,
 283                                                     0, data_block_size,
 284                                                     hash_level_block[i], hash_block_size,
 285                                                     data_file_blocks, version, hash_name, verify,
 286                                                     calculated_digest, digest_size, salt, salt_size);
 287                         if (r)
 288                                 goto out;
 289                 } else {
 290                         hash_file_2 = fopen(hash_device, "r");
 291                         if (!hash_file_2) {
 292                                 log_err(cd, _("Cannot open device %s.\n"), hash_device);
 293                                 r = -EIO;
 294                                 goto out;
 295                         }
 296                         r = create_or_verify(cd, hash_file_2, hash_file,
 297                                                     hash_level_block[i - 1], hash_block_size,
 298                                                     hash_level_block[i], hash_block_size,
 299                                                     hash_level_size[i - 1], version, hash_name, verify,
 300                                                     calculated_digest, digest_size, salt, salt_size);
 301                         fclose(hash_file_2);
 302                         if (r)
 303                                 goto out;
 304                 }
 305         }
 306
 307         if (levels)
 308                 r = create_or_verify(cd, hash_file, NULL,
 309                                             hash_level_block[levels - 1], hash_block_size,
 310                                             0, 0,
 311                                             1, version, hash_name, verify,
 312                                             calculated_digest, digest_size, salt, salt_size);
 313         else
 314                 r = create_or_verify(cd, data_file, NULL,
 315                                             0, data_block_size,
 316                                             0, 0,
 317                                             data_file_blocks, version, hash_name, verify,
 318                                             calculated_digest, digest_size, salt, salt_size);
 319 out:
 320         if (verify) {
 321                 if (r)
 322                         log_err(cd, _("Verification of data area failed.\n"));
 323                 else {
 324                         log_dbg("Verification of data area succeeded.");
 325                         r = memcmp(root_hash, calculated_digest, digest_size) ? -EPERM : 0;
 326                         if (r)
 327                                 log_err(cd, _("Verification of root hash failed.\n"));
 328                         else
 329                                 log_dbg("Verification of root hash succeeded.");
 330                 }
 331         } else {
 332                 if (r == -EIO)
 333                         log_err(cd, _("Input/output error while creating hash area.\n"));
 334                 else if (r)
 335                         log_err(cd, _("Creation of hash area failed.\n"));
 336                 else {
 337                         fsync(fileno(hash_file));
 338                         memcpy(root_hash, calculated_digest, digest_size);
 339                 }
 340         }
 341
 342         if (data_file)
 343                 fclose(data_file);
 344         if (hash_file)
 345                 fclose(hash_file);
 346         return r;
 347 }
 348
 349 /* Verify verity device using userspace crypto backend */
 350 int VERITY_verify(struct crypt_device *cd,
 351                   struct crypt_params_verity *verity_hdr,
 352                   const char *data_device,
 353                   const char *hash_device,
 354                   const char *root_hash,
 355                   size_t root_hash_size)
 356 {
 357         return VERITY_create_or_verify_hash(cd, 1,
 358                 verity_hdr->hash_type,
 359                 verity_hdr->hash_name,
 360                 hash_device,
 361                 data_device,
 362                 verity_hdr->hash_block_size,
 363                 verity_hdr->data_block_size,
 364                 verity_hdr->data_size,
 365                 VERITY_hash_offset_block(verity_hdr),
 366                 CONST_CAST(char*)root_hash,
 367                 root_hash_size,
 368                 verity_hdr->salt,
 369                 verity_hdr->salt_size);
 370 }
 371
 372 /* Create verity hash */
 373 int VERITY_create(struct crypt_device *cd,
 374                   struct crypt_params_verity *verity_hdr,
 375                   const char *data_device,
 376                   const char *hash_device,
 377                   char *root_hash,
 378                   size_t root_hash_size)
 379 {
 380         int pgsize = crypt_getpagesize();
 381
 382         if (verity_hdr->salt_size > 256)
 383                 return -EINVAL;
 384
 385         if (verity_hdr->hash_block_size > pgsize ||
 386             verity_hdr->data_block_size > pgsize)
 387                 log_err(cd, _("WARNING: Kernel cannot activate device if block "
 388                               "size exceeds page size (%u).\n"), pgsize);
 389
 390         return VERITY_create_or_verify_hash(cd, 0,
 391                 verity_hdr->hash_type,
 392                 verity_hdr->hash_name,
 393                 hash_device,
 394                 data_device,
 395                 verity_hdr->hash_block_size,
 396                 verity_hdr->data_block_size,
 397                 verity_hdr->data_size,
 398                 VERITY_hash_offset_block(verity_hdr),
 399                 root_hash,
 400                 root_hash_size,
 401                 verity_hdr->salt,
 402                 verity_hdr->salt_size);
 403 }