lib/verity/verity.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 #include <sys/types.h>
  27 #include <sys/stat.h>
  28 #include <netinet/in.h>
  29 #include <uuid/uuid.h>
  30
  31 #include "libcryptsetup.h"
  32 #include "verity.h"
  33 #include "internal.h"
  34
  35 #define VERITY_SIGNATURE "verity\0\0"
  36
  37 /* https://gitlab.com/cryptsetup/cryptsetup/wikis/DMVerity#verity-superblock-format */
  38 struct verity_sb {
  39         uint8_t  signature[8];  /* "verity\0\0" */
  40         uint32_t version;       /* superblock version */
  41         uint32_t hash_type;     /* 0 - Chrome OS, 1 - normal */
  42         uint8_t  uuid[16];      /* UUID of hash device */
  43         uint8_t  algorithm[32];/* hash algorithm name */
  44         uint32_t data_block_size; /* data block in bytes */
  45         uint32_t hash_block_size; /* hash block in bytes */
  46         uint64_t data_blocks;   /* number of data blocks */
  47         uint16_t salt_size;     /* salt size */
  48         uint8_t  _pad1[6];
  49         uint8_t  salt[256];     /* salt */
  50         uint8_t  _pad2[168];
  51 } __attribute__((packed));
  52
  53 /* Read verity superblock from disk */
  54 int VERITY_read_sb(struct crypt_device *cd,
  55                    uint64_t sb_offset,
  56                    char **uuid_string,
  57                    struct crypt_params_verity *params)
  58 {
  59         struct device *device = crypt_metadata_device(cd);
  60         struct verity_sb sb = {};
  61         ssize_t hdr_size = sizeof(struct verity_sb);
  62         int devfd, sb_version;
  63
  64         log_dbg(cd, "Reading VERITY header of size %zu on device %s, offset %" PRIu64 ".",
  65                 sizeof(struct verity_sb), device_path(device), sb_offset);
  66
  67         if (params->flags & CRYPT_VERITY_NO_HEADER) {
  68                 log_err(cd, _("Verity device %s does not use on-disk header."),
  69                         device_path(device));
  70                 return -EINVAL;
  71         }
  72
  73         if (MISALIGNED_512(sb_offset)) {
  74                 log_err(cd, _("Unsupported VERITY hash offset."));
  75                 return -EINVAL;
  76         }
  77
  78         devfd = device_open(cd, device, O_RDONLY);
  79         if (devfd < 0) {
  80                 log_err(cd, _("Cannot open device %s."), device_path(device));
  81                 return -EINVAL;
  82         }
  83
  84         if (read_lseek_blockwise(devfd, device_block_size(cd, device),
  85                                  device_alignment(device), &sb, hdr_size,
  86                                  sb_offset) < hdr_size)
  87                 return -EIO;
  88
  89         if (memcmp(sb.signature, VERITY_SIGNATURE, sizeof(sb.signature))) {
  90                 log_err(cd, _("Device %s is not a valid VERITY device."),
  91                         device_path(device));
  92                 return -EINVAL;
  93         }
  94
  95         sb_version = le32_to_cpu(sb.version);
  96         if (sb_version != 1) {
  97                 log_err(cd, _("Unsupported VERITY version %d."), sb_version);
  98                 return -EINVAL;
  99         }
 100         params->hash_type = le32_to_cpu(sb.hash_type);
 101         if (params->hash_type > VERITY_MAX_HASH_TYPE) {
 102                 log_err(cd, _("Unsupported VERITY hash type %d."), params->hash_type);
 103                 return -EINVAL;
 104         }
 105
 106         params->data_block_size = le32_to_cpu(sb.data_block_size);
 107         params->hash_block_size = le32_to_cpu(sb.hash_block_size);
 108         if (VERITY_BLOCK_SIZE_OK(params->data_block_size) ||
 109             VERITY_BLOCK_SIZE_OK(params->hash_block_size)) {
 110                 log_err(cd, _("Unsupported VERITY block size."));
 111                 return -EINVAL;
 112         }
 113         params->data_size = le64_to_cpu(sb.data_blocks);
 114
 115         params->hash_name = strndup((const char*)sb.algorithm, sizeof(sb.algorithm));
 116         if (!params->hash_name)
 117                 return -ENOMEM;
 118         if (crypt_hash_size(params->hash_name) <= 0) {
 119                 log_err(cd, _("Hash algorithm %s not supported."),
 120                         params->hash_name);
 121                 free(CONST_CAST(char*)params->hash_name);
 122                 params->hash_name = NULL;
 123                 return -EINVAL;
 124         }
 125
 126         params->salt_size = le16_to_cpu(sb.salt_size);
 127         if (params->salt_size > sizeof(sb.salt)) {
 128                 log_err(cd, _("VERITY header corrupted."));
 129                 free(CONST_CAST(char*)params->hash_name);
 130                 params->hash_name = NULL;
 131                 return -EINVAL;
 132         }
 133         params->salt = malloc(params->salt_size);
 134         if (!params->salt) {
 135                 free(CONST_CAST(char*)params->hash_name);
 136                 params->hash_name = NULL;
 137                 return -ENOMEM;
 138         }
 139         memcpy(CONST_CAST(char*)params->salt, sb.salt, params->salt_size);
 140
 141         if ((*uuid_string = malloc(40)))
 142                 uuid_unparse(sb.uuid, *uuid_string);
 143
 144         params->hash_area_offset = sb_offset;
 145         return 0;
 146 }
 147
 148 /* Write verity superblock to disk */
 149 int VERITY_write_sb(struct crypt_device *cd,
 150                    uint64_t sb_offset,
 151                    const char *uuid_string,
 152                    struct crypt_params_verity *params)
 153 {
 154         struct device *device = crypt_metadata_device(cd);
 155         struct verity_sb sb = {};
 156         ssize_t hdr_size = sizeof(struct verity_sb);
 157         char *algorithm;
 158         uuid_t uuid;
 159         int r, devfd;
 160
 161         log_dbg(cd, "Updating VERITY header of size %zu on device %s, offset %" PRIu64 ".",
 162                 sizeof(struct verity_sb), device_path(device), sb_offset);
 163
 164         if (!uuid_string || uuid_parse(uuid_string, uuid) == -1) {
 165                 log_err(cd, _("Wrong VERITY UUID format provided on device %s."),
 166                         device_path(device));
 167                 return -EINVAL;
 168         }
 169
 170         if (params->flags & CRYPT_VERITY_NO_HEADER) {
 171                 log_err(cd, _("Verity device %s does not use on-disk header."),
 172                         device_path(device));
 173                 return -EINVAL;
 174         }
 175
 176         devfd = device_open(cd, device, O_RDWR);
 177         if (devfd < 0) {
 178                 log_err(cd, _("Cannot open device %s."), device_path(device));
 179                 return -EINVAL;
 180         }
 181
 182         memcpy(&sb.signature, VERITY_SIGNATURE, sizeof(sb.signature));
 183         sb.version         = cpu_to_le32(1);
 184         sb.hash_type       = cpu_to_le32(params->hash_type);
 185         sb.data_block_size = cpu_to_le32(params->data_block_size);
 186         sb.hash_block_size = cpu_to_le32(params->hash_block_size);
 187         sb.salt_size       = cpu_to_le16(params->salt_size);
 188         sb.data_blocks     = cpu_to_le64(params->data_size);
 189         algorithm = (char *)sb.algorithm;
 190         algorithm[sizeof(sb.algorithm)-1] = '\0';
 191         strncpy(algorithm, params->hash_name, sizeof(sb.algorithm)-1);
 192         memcpy(sb.salt, params->salt, params->salt_size);
 193         memcpy(sb.uuid, uuid, sizeof(sb.uuid));
 194
 195         r = write_lseek_blockwise(devfd, device_block_size(cd, device), device_alignment(device),
 196                                   (char*)&sb, hdr_size, sb_offset) < hdr_size ? -EIO : 0;
 197         if (r)
 198                 log_err(cd, _("Error during update of verity header on device %s."),
 199                         device_path(device));
 200
 201         device_sync(cd, device);
 202
 203         return r;
 204 }
 205
 206 /* Calculate hash offset in hash blocks */
 207 uint64_t VERITY_hash_offset_block(struct crypt_params_verity *params)
 208 {
 209         uint64_t hash_offset = params->hash_area_offset;
 210
 211         if (params->flags & CRYPT_VERITY_NO_HEADER)
 212                 return hash_offset / params->hash_block_size;
 213
 214         hash_offset += sizeof(struct verity_sb);
 215         hash_offset += params->hash_block_size - 1;
 216
 217         return hash_offset / params->hash_block_size;
 218 }
 219
 220 int VERITY_UUID_generate(struct crypt_device *cd, char **uuid_string)
 221 {
 222         uuid_t uuid;
 223
 224         *uuid_string = malloc(40);
 225         if (!*uuid_string)
 226                 return -ENOMEM;
 227         uuid_generate(uuid);
 228         uuid_unparse(uuid, *uuid_string);
 229         return 0;
 230 }
 231
 232 /* Activate verity device in kernel device-mapper */
 233 int VERITY_activate(struct crypt_device *cd,
 234                      const char *name,
 235                      const char *root_hash,
 236                      size_t root_hash_size,
 237                      const char *signature_description,
 238                      struct device *fec_device,
 239                      struct crypt_params_verity *verity_hdr,
 240                      uint32_t activation_flags)
 241 {
 242         uint32_t dmv_flags;
 243         unsigned int fec_errors = 0;
 244         int r;
 245         struct crypt_dm_active_device dmd = {
 246                 .size = verity_hdr->data_size * verity_hdr->data_block_size / 512,
 247                 .flags = activation_flags,
 248                 .uuid = crypt_get_uuid(cd),
 249         };
 250
 251         log_dbg(cd, "Trying to activate VERITY device %s using hash %s.",
 252                 name ?: "[none]", verity_hdr->hash_name);
 253
 254         if (verity_hdr->flags & CRYPT_VERITY_CHECK_HASH) {
 255                 if (signature_description) {
 256                         log_err(cd, _("Root hash signature verification is not supported."));
 257                         return -EINVAL;
 258                 }
 259
 260                 log_dbg(cd, "Verification of data in userspace required.");
 261                 r = VERITY_verify(cd, verity_hdr, root_hash, root_hash_size);
 262
 263                 if (r == -EPERM && fec_device) {
 264                         log_dbg(cd, "Verification failed, trying to repair with FEC device.");
 265                         r = VERITY_FEC_process(cd, verity_hdr, fec_device, 1, &fec_errors);
 266                         if (r < 0)
 267                                 log_err(cd, _("Errors cannot be repaired with FEC device."));
 268                         else if (fec_errors)
 269                                 log_err(cd, _("Found %u repairable errors with FEC device."),
 270                                         fec_errors);
 271                 }
 272
 273                 if (r < 0)
 274                         return r;
 275         }
 276
 277         if (!name)
 278                 return 0;
 279
 280         r = device_block_adjust(cd, crypt_metadata_device(cd), DEV_OK,
 281                                 0, NULL, NULL);
 282         if (r)
 283                 return r;
 284
 285         r = device_block_adjust(cd, crypt_data_device(cd), DEV_EXCL,
 286                                 0, &dmd.size, &dmd.flags);
 287         if (r)
 288                 return r;
 289
 290         if (fec_device) {
 291                 r = device_block_adjust(cd, fec_device, DEV_OK,
 292                                         0, NULL, NULL);
 293                 if (r)
 294                         return r;
 295         }
 296
 297         r = dm_verity_target_set(&dmd.segment, 0, dmd.size, crypt_data_device(cd),
 298                         crypt_metadata_device(cd), fec_device, root_hash,
 299                         root_hash_size, signature_description,
 300                         VERITY_hash_offset_block(verity_hdr),
 301                         VERITY_hash_blocks(cd, verity_hdr), verity_hdr);
 302
 303         if (r)
 304                 return r;
 305
 306         r = dm_create_device(cd, name, CRYPT_VERITY, &dmd);
 307         if (r < 0 && (dm_flags(cd, DM_VERITY, &dmv_flags) || !(dmv_flags & DM_VERITY_SUPPORTED))) {
 308                 log_err(cd, _("Kernel does not support dm-verity mapping."));
 309                 r = -ENOTSUP;
 310         }
 311         if (r < 0 && signature_description && !(dmv_flags & DM_VERITY_SIGNATURE_SUPPORTED)) {
 312                 log_err(cd, _("Kernel does not support dm-verity signature option."));
 313                 r = -ENOTSUP;
 314         }
 315         if (r < 0)
 316                 goto out;
 317
 318         r = dm_status_verity_ok(cd, name);
 319         if (r < 0)
 320                 goto out;
 321
 322         if (!r)
 323                 log_err(cd, _("Verity device detected corruption after activation."));
 324
 325         r = 0;
 326 out:
 327         dm_targets_free(cd, &dmd);
 328         return r;
 329 }