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 ((1U << 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) > 1U)
  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         unsigned i;
 107         int r;
 108
 109         if (fseeko(rd, data_block * data_block_size, SEEK_SET)) {
 110                 log_dbg("Cannot seek to requested position in data device.");
 111                 return -EIO;
 112         }
 113
 114         if (wr && fseeko(wr, hash_block * hash_block_size, SEEK_SET)) {
 115                 log_dbg("Cannot seek to requested position in hash device.");
 116                 return -EIO;
 117         }
 118
 119         memset(left_block, 0, hash_block_size);
 120         while (blocks_to_write--) {
 121                 left_bytes = hash_block_size;
 122                 for (i = 0; i < hash_per_block; i++) {
 123                         if (!blocks)
 124                                 break;
 125                         blocks--;
 126                         if (fread(data_buffer, data_block_size, 1, rd) != 1) {
 127                                 log_dbg("Cannot read data device block.");
 128                                 return -EIO;
 129                         }
 130
 131                         if (verify_hash_block(hash_name, version,
 132                                         calculated_digest, digest_size,
 133                                         data_buffer, data_block_size,
 134                                         salt, salt_size))
 135                                 return -EINVAL;
 136
 137                         if (!wr)
 138                                 break;
 139                         if (verify) {
 140                                 if (fread(read_digest, digest_size, 1, wr) != 1) {
 141                                         log_dbg("Cannot read digest form hash device.");
 142                                         return -EIO;
 143                                 }
 144                                 if (memcmp(read_digest, calculated_digest, digest_size)) {
 145                                         log_err(cd, _("Verification failed at position %" PRIu64 ".\n"),
 146                                                 ftello(rd) - data_block_size);
 147                                         return -EPERM;
 148                                 }
 149                         } else {
 150                                 if (fwrite(calculated_digest, digest_size, 1, wr) != 1) {
 151                                         log_dbg("Cannot write digest to hash device.");
 152                                         return -EIO;
 153                                 }
 154                         }
 155                         if (version == 0) {
 156                                 left_bytes -= digest_size;
 157                         } else {
 158                                 if (digest_size_full - digest_size) {
 159                                         if (verify) {
 160                                                 r = verify_zero(cd, wr, digest_size_full - digest_size);
 161                                                 if (r)
 162                                                         return r;
 163                                         } else if (fwrite(left_block, digest_size_full - digest_size, 1, wr) != 1) {
 164                                                 log_dbg("Cannot write spare area to hash device.");
 165                                                 return -EIO;
 166                                         }
 167                                 }
 168                                 left_bytes -= digest_size_full;
 169                         }
 170                 }
 171                 if (wr && left_bytes) {
 172                         if (verify) {
 173                                 r = verify_zero(cd , wr, left_bytes);
 174                                 if (r)
 175                                         return r;
 176                         } else if (fwrite(left_block, left_bytes, 1, wr) != 1) {
 177                                 log_dbg("Cannot write remaining spare area to hash device.");
 178                                 return -EIO;
 179                         }
 180                 }
 181         }
 182
 183         return 0;
 184 }
 185
 186 static int VERITY_create_or_verify_hash(struct crypt_device *cd,
 187         int verify,
 188         int version,
 189         const char *hash_name,
 190         const char *hash_device,
 191         const char *data_device,
 192         size_t hash_block_size,
 193         size_t data_block_size,
 194         off_t data_blocks,
 195         off_t hash_position,
 196         char *root_hash,
 197         size_t digest_size,
 198         const char *salt,
 199         size_t salt_size)
 200 {
 201         char calculated_digest[digest_size];
 202         FILE *data_file = NULL;
 203         FILE *hash_file = NULL, *hash_file_2;
 204         off_t hash_level_block[VERITY_MAX_LEVELS];
 205         off_t hash_level_size[VERITY_MAX_LEVELS];
 206         off_t data_file_blocks, s;
 207         size_t hash_per_block, hash_per_block_bits;
 208         uint64_t data_device_size = 0, hash_device_size = 0;
 209         int levels, i, r;
 210
 211         log_dbg("Hash %s %s, data device %s, data blocks %" PRIu64
 212                 ", hash_device %s, offset %" PRIu64 ".",
 213                 verify ? "verification" : "creation", hash_name,
 214                 data_device, data_blocks, hash_device, hash_position);
 215
 216         if (!data_blocks) {
 217                 r = device_size(data_device, &data_device_size);
 218                 if (r < 0)
 219                         return r;
 220
 221                 data_file_blocks = data_device_size / data_block_size;
 222         } else {
 223                 data_device_size = data_blocks * data_block_size;
 224                 data_file_blocks = data_blocks;
 225         }
 226
 227         hash_per_block_bits = get_bits_down(hash_block_size / digest_size);
 228         hash_per_block = 1 << hash_per_block_bits;
 229         if (!hash_per_block_bits)
 230                 return -EINVAL;
 231
 232         levels = 0;
 233         if (data_file_blocks) {
 234                 while (hash_per_block_bits * levels < 64 &&
 235                        (data_file_blocks - 1) >> (hash_per_block_bits * levels))
 236                         levels++;
 237         }
 238         log_dbg("Using %d hash levels.", levels);
 239
 240         if (levels > VERITY_MAX_LEVELS) {
 241                 log_err(cd, _("Too many tree levels for verity volume.\n"));
 242                 return -EINVAL;
 243         }
 244
 245         for (i = levels - 1; i >= 0; i--) {
 246                 hash_level_block[i] = hash_position;
 247                 // verity position of block data_file_blocks at level i
 248                 s = data_file_blocks >> (i * hash_per_block_bits);
 249                 s = (s + hash_per_block - 1) / hash_per_block;
 250                 hash_level_size[i] = s;
 251                 if (hash_position + s < hash_position ||
 252                     (hash_position + s) < 0 ||
 253                     (hash_position + s) != hash_position + s) {
 254                         log_dbg("Hash device offset overflow.");
 255                         return -EINVAL;
 256                 }
 257                 hash_position += s;
 258         }
 259         hash_device_size = hash_position * hash_block_size;
 260
 261         log_dbg("Data device size required: %" PRIu64 " bytes.",
 262                 data_device_size);
 263         data_file = fopen(data_device, "r");
 264         if (!data_file) {
 265                 log_err(cd, _("Cannot open device %s.\n"), data_device);
 266                 r = -EIO;
 267                 goto out;
 268         }
 269
 270         log_dbg("Hash device size required: %" PRIu64 " bytes.",
 271                 hash_device_size);
 272         hash_file = fopen(hash_device, verify ? "r" : "r+");
 273         if (!hash_file) {
 274                 log_err(cd, _("Cannot open device %s.\n"), hash_device);
 275                 r = -EIO;
 276                 goto out;
 277         }
 278
 279         memset(calculated_digest, 0, digest_size);
 280
 281         for (i = 0; i < levels; i++) {
 282                 if (!i) {
 283                         r = create_or_verify(cd, data_file, hash_file,
 284                                                     0, data_block_size,
 285                                                     hash_level_block[i], hash_block_size,
 286                                                     data_file_blocks, version, hash_name, verify,
 287                                                     calculated_digest, digest_size, salt, salt_size);
 288                         if (r)
 289                                 goto out;
 290                 } else {
 291                         hash_file_2 = fopen(hash_device, "r");
 292                         if (!hash_file_2) {
 293                                 log_err(cd, _("Cannot open device %s.\n"), hash_device);
 294                                 r = -EIO;
 295                                 goto out;
 296                         }
 297                         r = create_or_verify(cd, hash_file_2, hash_file,
 298                                                     hash_level_block[i - 1], hash_block_size,
 299                                                     hash_level_block[i], hash_block_size,
 300                                                     hash_level_size[i - 1], version, hash_name, verify,
 301                                                     calculated_digest, digest_size, salt, salt_size);
 302                         fclose(hash_file_2);
 303                         if (r)
 304                                 goto out;
 305                 }
 306         }
 307
 308         if (levels)
 309                 r = create_or_verify(cd, hash_file, NULL,
 310                                             hash_level_block[levels - 1], hash_block_size,
 311                                             0, hash_block_size,
 312                                             1, version, hash_name, verify,
 313                                             calculated_digest, digest_size, salt, salt_size);
 314         else
 315                 r = create_or_verify(cd, data_file, NULL,
 316                                             0, data_block_size,
 317                                             0, hash_block_size,
 318                                             data_file_blocks, version, hash_name, verify,
 319                                             calculated_digest, digest_size, salt, salt_size);
 320 out:
 321         if (verify) {
 322                 if (r)
 323                         log_err(cd, _("Verification of data area failed.\n"));
 324                 else {
 325                         log_dbg("Verification of data area succeeded.");
 326                         r = memcmp(root_hash, calculated_digest, digest_size) ? -EPERM : 0;
 327                         if (r)
 328                                 log_err(cd, _("Verification of root hash failed.\n"));
 329                         else
 330                                 log_dbg("Verification of root hash succeeded.");
 331                 }
 332         } else {
 333                 if (r == -EIO)
 334                         log_err(cd, _("Input/output error while creating hash area.\n"));
 335                 else if (r)
 336                         log_err(cd, _("Creation of hash area failed.\n"));
 337                 else {
 338                         fsync(fileno(hash_file));
 339                         memcpy(root_hash, calculated_digest, digest_size);
 340                 }
 341         }
 342
 343         if (data_file)
 344                 fclose(data_file);
 345         if (hash_file)
 346                 fclose(hash_file);
 347         return r;
 348 }
 349
 350 /* Verify verity device using userspace crypto backend */
 351 int VERITY_verify(struct crypt_device *cd,
 352                   struct crypt_params_verity *verity_hdr,
 353                   const char *data_device,
 354                   const char *hash_device,
 355                   const char *root_hash,
 356                   size_t root_hash_size)
 357 {
 358         return VERITY_create_or_verify_hash(cd, 1,
 359                 verity_hdr->hash_type,
 360                 verity_hdr->hash_name,
 361                 hash_device,
 362                 data_device,
 363                 verity_hdr->hash_block_size,
 364                 verity_hdr->data_block_size,
 365                 verity_hdr->data_size,
 366                 VERITY_hash_offset_block(verity_hdr),
 367                 CONST_CAST(char*)root_hash,
 368                 root_hash_size,
 369                 verity_hdr->salt,
 370                 verity_hdr->salt_size);
 371 }
 372
 373 /* Create verity hash */
 374 int VERITY_create(struct crypt_device *cd,
 375                   struct crypt_params_verity *verity_hdr,
 376                   const char *data_device,
 377                   const char *hash_device,
 378                   char *root_hash,
 379                   size_t root_hash_size)
 380 {
 381         unsigned pgsize = crypt_getpagesize();
 382
 383         if (verity_hdr->salt_size > 256)
 384                 return -EINVAL;
 385
 386         if (verity_hdr->hash_block_size > pgsize ||
 387             verity_hdr->data_block_size > pgsize)
 388                 log_err(cd, _("WARNING: Kernel cannot activate device if block "
 389                               "size exceeds page size (%u).\n"), pgsize);
 390
 391         return VERITY_create_or_verify_hash(cd, 0,
 392                 verity_hdr->hash_type,
 393                 verity_hdr->hash_name,
 394                 hash_device,
 395                 data_device,
 396                 verity_hdr->hash_block_size,
 397                 verity_hdr->data_block_size,
 398                 verity_hdr->data_size,
 399                 VERITY_hash_offset_block(verity_hdr),
 400                 root_hash,
 401                 root_hash_size,
 402                 verity_hdr->salt,
 403                 verity_hdr->salt_size);
 404 }