lib/verity/verity_hash.c

   1 /*
   2  * dm-verity volume handling
   3  *
   4  * Copyright (C) 2012-2020 Red Hat, Inc. All rights reserved.
   5  *
   6  * This file is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This file is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this file; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19  */
  20
  21 #include <errno.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <stdint.h>
  26
  27 #include "verity.h"
  28 #include "internal.h"
  29
  30 #define VERITY_MAX_LEVELS       63
  31
  32 static unsigned get_bits_up(size_t u)
  33 {
  34         unsigned i = 0;
  35         while ((1U << i) < u)
  36                 i++;
  37         return i;
  38 }
  39
  40 static unsigned get_bits_down(size_t u)
  41 {
  42         unsigned i = 0;
  43         while ((u >> i) > 1U)
  44                 i++;
  45         return i;
  46 }
  47
  48 static int verify_zero(struct crypt_device *cd, FILE *wr, size_t bytes)
  49 {
  50         char block[bytes];
  51         size_t i;
  52
  53         if (fread(block, bytes, 1, wr) != 1) {
  54                 log_dbg(cd, "EIO while reading spare area.");
  55                 return -EIO;
  56         }
  57         for (i = 0; i < bytes; i++)
  58                 if (block[i]) {
  59                         log_err(cd, _("Spare area is not zeroed at position %" PRIu64 "."),
  60                                 ftello(wr) - bytes);
  61                         return -EPERM;
  62                 }
  63         return 0;
  64 }
  65
  66 static int verify_hash_block(const char *hash_name, int version,
  67                               char *hash, size_t hash_size,
  68                               const char *data, size_t data_size,
  69                               const char *salt, size_t salt_size)
  70 {
  71         struct crypt_hash *ctx = NULL;
  72         int r;
  73
  74         if (crypt_hash_init(&ctx, hash_name))
  75                 return -EINVAL;
  76
  77         if (version == 1 && (r = crypt_hash_write(ctx, salt, salt_size)))
  78                 goto out;
  79
  80         if ((r = crypt_hash_write(ctx, data, data_size)))
  81                 goto out;
  82
  83         if (version == 0 && (r = crypt_hash_write(ctx, salt, salt_size)))
  84                 goto out;
  85
  86         r = crypt_hash_final(ctx, hash, hash_size);
  87 out:
  88         crypt_hash_destroy(ctx);
  89         return r;
  90 }
  91
  92 static int mult_overflow(off_t *u, off_t b, size_t size)
  93 {
  94         *u = (uint64_t)b * size;
  95         if ((off_t)(*u / size) != b || (off_t)*u < 0)
  96                 return 1;
  97         return 0;
  98 }
  99
 100 static int hash_levels(size_t hash_block_size, size_t digest_size,
 101                        off_t data_file_blocks, off_t *hash_position, int *levels,
 102                        off_t *hash_level_block, off_t *hash_level_size)
 103 {
 104         size_t hash_per_block_bits;
 105         off_t s, s_shift;
 106         int i;
 107
 108         if (!digest_size)
 109                 return -EINVAL;
 110
 111         hash_per_block_bits = get_bits_down(hash_block_size / digest_size);
 112         if (!hash_per_block_bits)
 113                 return -EINVAL;
 114
 115         *levels = 0;
 116         while (hash_per_block_bits * *levels < 64 &&
 117                (data_file_blocks - 1) >> (hash_per_block_bits * *levels))
 118                 (*levels)++;
 119
 120         if (*levels > VERITY_MAX_LEVELS)
 121                 return -EINVAL;
 122
 123         for (i = *levels - 1; i >= 0; i--) {
 124                 if (hash_level_block)
 125                         hash_level_block[i] = *hash_position;
 126                 // verity position of block data_file_blocks at level i
 127                 s_shift = (i + 1) * hash_per_block_bits;
 128                 if (s_shift > 63)
 129                         return -EINVAL;
 130                 s = (data_file_blocks + ((off_t)1 << s_shift) - 1) >> ((i + 1) * hash_per_block_bits);
 131                 if (hash_level_size)
 132                         hash_level_size[i] = s;
 133                 if ((*hash_position + s) < *hash_position ||
 134                     (*hash_position + s) < 0)
 135                         return -EINVAL;
 136                 *hash_position += s;
 137         }
 138
 139         return 0;
 140 }
 141
 142 static int create_or_verify(struct crypt_device *cd, FILE *rd, FILE *wr,
 143                                    off_t data_block, size_t data_block_size,
 144                                    off_t hash_block, size_t hash_block_size,
 145                                    off_t blocks, int version,
 146                                    const char *hash_name, int verify,
 147                                    char *calculated_digest, size_t digest_size,
 148                                    const char *salt, size_t salt_size)
 149 {
 150         char left_block[hash_block_size];
 151         char data_buffer[data_block_size];
 152         char read_digest[digest_size];
 153         size_t hash_per_block = 1 << get_bits_down(hash_block_size / digest_size);
 154         size_t digest_size_full = 1 << get_bits_up(digest_size);
 155         off_t blocks_to_write = (blocks + hash_per_block - 1) / hash_per_block;
 156         off_t seek_rd, seek_wr;
 157         size_t left_bytes;
 158         unsigned i;
 159         int r;
 160
 161         if (mult_overflow(&seek_rd, data_block, data_block_size) ||
 162             mult_overflow(&seek_wr, hash_block, hash_block_size)) {
 163                 log_err(cd, _("Device offset overflow."));
 164                 return -EINVAL;
 165         }
 166
 167         if (fseeko(rd, seek_rd, SEEK_SET)) {
 168                 log_dbg(cd, "Cannot seek to requested position in data device.");
 169                 return -EIO;
 170         }
 171
 172         if (wr && fseeko(wr, seek_wr, SEEK_SET)) {
 173                 log_dbg(cd, "Cannot seek to requested position in hash device.");
 174                 return -EIO;
 175         }
 176
 177         memset(left_block, 0, hash_block_size);
 178         while (blocks_to_write--) {
 179                 left_bytes = hash_block_size;
 180                 for (i = 0; i < hash_per_block; i++) {
 181                         if (!blocks)
 182                                 break;
 183                         blocks--;
 184                         if (fread(data_buffer, data_block_size, 1, rd) != 1) {
 185                                 log_dbg(cd, "Cannot read data device block.");
 186                                 return -EIO;
 187                         }
 188
 189                         if (verify_hash_block(hash_name, version,
 190                                         calculated_digest, digest_size,
 191                                         data_buffer, data_block_size,
 192                                         salt, salt_size))
 193                                 return -EINVAL;
 194
 195                         if (!wr)
 196                                 break;
 197                         if (verify) {
 198                                 if (fread(read_digest, digest_size, 1, wr) != 1) {
 199                                         log_dbg(cd, "Cannot read digest form hash device.");
 200                                         return -EIO;
 201                                 }
 202                                 if (memcmp(read_digest, calculated_digest, digest_size)) {
 203                                         log_err(cd, _("Verification failed at position %" PRIu64 "."),
 204                                                 ftello(rd) - data_block_size);
 205                                         return -EPERM;
 206                                 }
 207                         } else {
 208                                 if (fwrite(calculated_digest, digest_size, 1, wr) != 1) {
 209                                         log_dbg(cd, "Cannot write digest to hash device.");
 210                                         return -EIO;
 211                                 }
 212                         }
 213                         if (version == 0) {
 214                                 left_bytes -= digest_size;
 215                         } else {
 216                                 if (digest_size_full - digest_size) {
 217                                         if (verify) {
 218                                                 r = verify_zero(cd, wr, digest_size_full - digest_size);
 219                                                 if (r)
 220                                                         return r;
 221                                         } else if (fwrite(left_block, digest_size_full - digest_size, 1, wr) != 1) {
 222                                                 log_dbg(cd, "Cannot write spare area to hash device.");
 223                                                 return -EIO;
 224                                         }
 225                                 }
 226                                 left_bytes -= digest_size_full;
 227                         }
 228                 }
 229                 if (wr && left_bytes) {
 230                         if (verify) {
 231                                 r = verify_zero(cd , wr, left_bytes);
 232                                 if (r)
 233                                         return r;
 234                         } else if (fwrite(left_block, left_bytes, 1, wr) != 1) {
 235                                 log_dbg(cd, "Cannot write remaining spare area to hash device.");
 236                                 return -EIO;
 237                         }
 238                 }
 239         }
 240
 241         return 0;
 242 }
 243
 244 static int VERITY_create_or_verify_hash(struct crypt_device *cd,
 245         int verify,
 246         int version,
 247         const char *hash_name,
 248         struct device *hash_device,
 249         struct device *data_device,
 250         size_t hash_block_size,
 251         size_t data_block_size,
 252         off_t data_blocks,
 253         off_t hash_position,
 254         char *root_hash,
 255         size_t digest_size,
 256         const char *salt,
 257         size_t salt_size)
 258 {
 259         char calculated_digest[digest_size];
 260         FILE *data_file = NULL;
 261         FILE *hash_file = NULL, *hash_file_2;
 262         off_t hash_level_block[VERITY_MAX_LEVELS];
 263         off_t hash_level_size[VERITY_MAX_LEVELS];
 264         off_t data_file_blocks;
 265         off_t data_device_size = 0, hash_device_size = 0;
 266         uint64_t dev_size;
 267         int levels, i, r;
 268
 269         log_dbg(cd, "Hash %s %s, data device %s, data blocks %" PRIu64
 270                 ", hash_device %s, offset %" PRIu64 ".",
 271                 verify ? "verification" : "creation", hash_name,
 272                 device_path(data_device), data_blocks,
 273                 device_path(hash_device), hash_position);
 274
 275         if (data_blocks < 0 || hash_position < 0) {
 276                 log_err(cd, _("Invalid size parameters for verity device."));
 277                 return -EINVAL;
 278         }
 279
 280         if (!data_blocks) {
 281                 r = device_size(data_device, &dev_size);
 282                 if (r < 0)
 283                         return r;
 284
 285                 data_file_blocks = dev_size / data_block_size;
 286         } else
 287                 data_file_blocks = data_blocks;
 288
 289         if (mult_overflow(&data_device_size, data_blocks, data_block_size)) {
 290                 log_err(cd, _("Device offset overflow."));
 291                 return -EINVAL;
 292         }
 293
 294         if (hash_levels(hash_block_size, digest_size, data_file_blocks, &hash_position,
 295                 &levels, &hash_level_block[0], &hash_level_size[0])) {
 296                 log_err(cd, _("Hash area overflow."));
 297                 return -EINVAL;
 298         }
 299
 300         log_dbg(cd, "Using %d hash levels.", levels);
 301
 302         if (mult_overflow(&hash_device_size, hash_position, hash_block_size)) {
 303                 log_err(cd, _("Device offset overflow."));
 304                 return -EINVAL;
 305         }
 306
 307         log_dbg(cd, "Data device size required: %" PRIu64 " bytes.",
 308                 data_device_size);
 309         data_file = fopen(device_path(data_device), "r");
 310         if (!data_file) {
 311                 log_err(cd, _("Cannot open device %s."),
 312                         device_path(data_device)
 313                 );
 314                 r = -EIO;
 315                 goto out;
 316         }
 317
 318         log_dbg(cd, "Hash device size required: %" PRIu64 " bytes.",
 319                 hash_device_size);
 320         hash_file = fopen(device_path(hash_device), verify ? "r" : "r+");
 321         if (!hash_file) {
 322                 log_err(cd, _("Cannot open device %s."),
 323                         device_path(hash_device));
 324                 r = -EIO;
 325                 goto out;
 326         }
 327
 328         memset(calculated_digest, 0, digest_size);
 329
 330         for (i = 0; i < levels; i++) {
 331                 if (!i) {
 332                         r = create_or_verify(cd, data_file, hash_file,
 333                                                     0, data_block_size,
 334                                                     hash_level_block[i], hash_block_size,
 335                                                     data_file_blocks, version, hash_name, verify,
 336                                                     calculated_digest, digest_size, salt, salt_size);
 337                         if (r)
 338                                 goto out;
 339                 } else {
 340                         hash_file_2 = fopen(device_path(hash_device), "r");
 341                         if (!hash_file_2) {
 342                                 log_err(cd, _("Cannot open device %s."),
 343                                         device_path(hash_device));
 344                                 r = -EIO;
 345                                 goto out;
 346                         }
 347                         r = create_or_verify(cd, hash_file_2, hash_file,
 348                                                     hash_level_block[i - 1], hash_block_size,
 349                                                     hash_level_block[i], hash_block_size,
 350                                                     hash_level_size[i - 1], version, hash_name, verify,
 351                                                     calculated_digest, digest_size, salt, salt_size);
 352                         fclose(hash_file_2);
 353                         if (r)
 354                                 goto out;
 355                 }
 356         }
 357
 358         if (levels)
 359                 r = create_or_verify(cd, hash_file, NULL,
 360                                             hash_level_block[levels - 1], hash_block_size,
 361                                             0, hash_block_size,
 362                                             1, version, hash_name, verify,
 363                                             calculated_digest, digest_size, salt, salt_size);
 364         else
 365                 r = create_or_verify(cd, data_file, NULL,
 366                                             0, data_block_size,
 367                                             0, hash_block_size,
 368                                             data_file_blocks, version, hash_name, verify,
 369                                             calculated_digest, digest_size, salt, salt_size);
 370 out:
 371         if (verify) {
 372                 if (r)
 373                         log_err(cd, _("Verification of data area failed."));
 374                 else {
 375                         log_dbg(cd, "Verification of data area succeeded.");
 376                         r = memcmp(root_hash, calculated_digest, digest_size) ? -EPERM : 0;
 377                         if (r)
 378                                 log_err(cd, _("Verification of root hash failed."));
 379                         else
 380                                 log_dbg(cd, "Verification of root hash succeeded.");
 381                 }
 382         } else {
 383                 if (r == -EIO)
 384                         log_err(cd, _("Input/output error while creating hash area."));
 385                 else if (r)
 386                         log_err(cd, _("Creation of hash area failed."));
 387                 else {
 388                         fsync(fileno(hash_file));
 389                         memcpy(root_hash, calculated_digest, digest_size);
 390                 }
 391         }
 392
 393         if (data_file)
 394                 fclose(data_file);
 395         if (hash_file)
 396                 fclose(hash_file);
 397         return r;
 398 }
 399
 400 /* Verify verity device using userspace crypto backend */
 401 int VERITY_verify(struct crypt_device *cd,
 402                   struct crypt_params_verity *verity_hdr,
 403                   const char *root_hash,
 404                   size_t root_hash_size)
 405 {
 406         return VERITY_create_or_verify_hash(cd, 1,
 407                 verity_hdr->hash_type,
 408                 verity_hdr->hash_name,
 409                 crypt_metadata_device(cd),
 410                 crypt_data_device(cd),
 411                 verity_hdr->hash_block_size,
 412                 verity_hdr->data_block_size,
 413                 verity_hdr->data_size,
 414                 VERITY_hash_offset_block(verity_hdr),
 415                 CONST_CAST(char*)root_hash,
 416                 root_hash_size,
 417                 verity_hdr->salt,
 418                 verity_hdr->salt_size);
 419 }
 420
 421 /* Create verity hash */
 422 int VERITY_create(struct crypt_device *cd,
 423                   struct crypt_params_verity *verity_hdr,
 424                   const char *root_hash,
 425                   size_t root_hash_size)
 426 {
 427         unsigned pgsize = (unsigned)crypt_getpagesize();
 428
 429         if (verity_hdr->salt_size > 256)
 430                 return -EINVAL;
 431
 432         if (verity_hdr->data_block_size > pgsize)
 433                 log_err(cd, _("WARNING: Kernel cannot activate device if data "
 434                               "block size exceeds page size (%u)."), pgsize);
 435
 436         return VERITY_create_or_verify_hash(cd, 0,
 437                 verity_hdr->hash_type,
 438                 verity_hdr->hash_name,
 439                 crypt_metadata_device(cd),
 440                 crypt_data_device(cd),
 441                 verity_hdr->hash_block_size,
 442                 verity_hdr->data_block_size,
 443                 verity_hdr->data_size,
 444                 VERITY_hash_offset_block(verity_hdr),
 445                 CONST_CAST(char*)root_hash,
 446                 root_hash_size,
 447                 verity_hdr->salt,
 448                 verity_hdr->salt_size);
 449 }
 450
 451 uint64_t VERITY_hash_blocks(struct crypt_device *cd, struct crypt_params_verity *params)
 452 {
 453         off_t hash_position = 0;
 454         int levels = 0;
 455
 456         if (hash_levels(params->hash_block_size, crypt_get_volume_key_size(cd),
 457                 params->data_size, &hash_position, &levels, NULL, NULL))
 458                 return 0;
 459
 460         return (uint64_t)hash_position;
 461 }