lib/verity/verity.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 #include <sys/types.h>
  26 #include <sys/stat.h>
  27 #include <fcntl.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 /* http://code.google.com/p/cryptsetup/wiki/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                    const char *device,
  56                    uint64_t sb_offset,
  57                    char **uuid_string,
  58                    struct crypt_params_verity *params)
  59 {
  60         struct verity_sb sb = {};
  61         ssize_t hdr_size = sizeof(struct verity_sb);
  62         int devfd = 0, sb_version;
  63
  64         log_dbg("Reading VERITY header of size %u on device %s, offset %" PRIu64 ".",
  65                 sizeof(struct verity_sb), device, sb_offset);
  66
  67         if (params->flags & CRYPT_VERITY_NO_HEADER) {
  68                 log_err(cd, _("Verity device doesn't use on-disk header.\n"), device);
  69                 return -EINVAL;
  70         }
  71
  72         if (sb_offset % 512) {
  73                 log_err(cd, _("Unsupported VERITY hash offset.\n"));
  74                 return -EINVAL;
  75         }
  76
  77         devfd = open(device ,O_RDONLY | O_DIRECT);
  78         if(devfd == -1) {
  79                 log_err(cd, _("Cannot open device %s.\n"), device);
  80                 return -EINVAL;
  81         }
  82
  83         if(lseek(devfd, sb_offset, SEEK_SET) < 0 ||
  84            read_blockwise(devfd, &sb, hdr_size) < hdr_size) {
  85                 close(devfd);
  86                 return -EIO;
  87         }
  88         close(devfd);
  89
  90         if (memcmp(sb.signature, VERITY_SIGNATURE, sizeof(sb.signature))) {
  91                 log_err(cd, _("Device %s is not a valid VERITY device.\n"), 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.\n"), 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.\n"), 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.\n"));
 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.\n"),
 120                         params->hash_name);
 121                 free(CONST_CAST(char*)params->hash_name);
 122                 return -EINVAL;
 123         }
 124
 125         params->salt_size = le16_to_cpu(sb.salt_size);
 126         if (params->salt_size > sizeof(sb.salt)) {
 127                 log_err(cd, _("VERITY header corrupted.\n"));
 128                 free(CONST_CAST(char*)params->hash_name);
 129                 return -EINVAL;
 130         }
 131         params->salt = malloc(params->salt_size);
 132         if (!params->salt) {
 133                 free(CONST_CAST(char*)params->hash_name);
 134                 return -ENOMEM;
 135         }
 136         memcpy(CONST_CAST(char*)params->salt, sb.salt, params->salt_size);
 137
 138         if ((*uuid_string = malloc(40)))
 139                 uuid_unparse(sb.uuid, *uuid_string);
 140
 141         params->hash_area_offset = sb_offset;
 142         return 0;
 143 }
 144
 145 /* Write verity superblock to disk */
 146 int VERITY_write_sb(struct crypt_device *cd,
 147                    const char *device,
 148                    uint64_t sb_offset,
 149                    const char *uuid_string,
 150                    struct crypt_params_verity *params)
 151 {
 152         struct verity_sb sb = {};
 153         ssize_t hdr_size = sizeof(struct verity_sb);
 154         uuid_t uuid;
 155         int r, devfd = 0;
 156
 157         log_dbg("Updating VERITY header of size %u on device %s, offset %" PRIu64 ".",
 158                 sizeof(struct verity_sb), device, sb_offset);
 159
 160         if (!uuid_string || uuid_parse(uuid_string, uuid) == -1) {
 161                 log_err(cd, _("Wrong VERITY UUID format provided.\n"), device);
 162                 return -EINVAL;
 163         }
 164
 165         if (params->flags & CRYPT_VERITY_NO_HEADER) {
 166                 log_err(cd, _("Verity device doesn't use on-disk header.\n"), device);
 167                 return -EINVAL;
 168         }
 169
 170         devfd = open(device, O_RDWR | O_DIRECT);
 171         if(devfd == -1) {
 172                 log_err(cd, _("Cannot open device %s.\n"), device);
 173                 return -EINVAL;
 174         }
 175
 176         memcpy(&sb.signature, VERITY_SIGNATURE, sizeof(sb.signature));
 177         sb.version         = cpu_to_le32(1);
 178         sb.hash_type       = cpu_to_le32(params->hash_type);
 179         sb.data_block_size = cpu_to_le32(params->data_block_size);
 180         sb.hash_block_size = cpu_to_le32(params->hash_block_size);
 181         sb.salt_size       = cpu_to_le16(params->salt_size);
 182         sb.data_blocks     = cpu_to_le64(params->data_size);
 183         strncpy((char *)sb.algorithm, params->hash_name, sizeof(sb.algorithm));
 184         memcpy(sb.salt, params->salt, params->salt_size);
 185         memcpy(sb.uuid, uuid, sizeof(sb.uuid));
 186
 187         r = write_lseek_blockwise(devfd, (char*)&sb, hdr_size, sb_offset) < hdr_size ? -EIO : 0;
 188         if (r)
 189                 log_err(cd, _("Error during update of verity header on device %s.\n"), device);
 190         close(devfd);
 191
 192         return r;
 193 }
 194
 195 /* Calculate hash offset in hash blocks */
 196 uint64_t VERITY_hash_offset_block(struct crypt_params_verity *params)
 197 {
 198         uint64_t hash_offset = params->hash_area_offset;
 199
 200         if (params->flags & CRYPT_VERITY_NO_HEADER)
 201                 return hash_offset / params->hash_block_size;
 202
 203         hash_offset += sizeof(struct verity_sb);
 204         hash_offset += params->hash_block_size - 1;
 205
 206         return hash_offset / params->hash_block_size;
 207 }
 208
 209 int VERITY_UUID_generate(struct crypt_device *cd, char **uuid_string)
 210 {
 211         uuid_t uuid;
 212
 213         if (!(*uuid_string = malloc(40)))
 214                 return -ENOMEM;
 215         uuid_generate(uuid);
 216         uuid_unparse(uuid, *uuid_string);
 217         return 0;
 218 }
 219
 220 /* Activate verity device in kernel device-mapper */
 221 int VERITY_activate(struct crypt_device *cd,
 222                      const char *name,
 223                      const char *hash_device,
 224                      const char *root_hash,
 225                      size_t root_hash_size,
 226                      struct crypt_params_verity *verity_hdr,
 227                      uint32_t activation_flags)
 228 {
 229         struct crypt_dm_active_device dmd;
 230         uint64_t offset = 0;
 231         int r;
 232
 233         log_dbg("Trying to activate VERITY device %s using hash %s.",
 234                 name ?: "[none]", verity_hdr->hash_name);
 235
 236         if (verity_hdr->flags & CRYPT_VERITY_CHECK_HASH) {
 237                 log_dbg("Verification of data in userspace required.");
 238                 r = VERITY_verify(cd, verity_hdr,
 239                                   crypt_get_device_name(cd), hash_device,
 240                                   root_hash, root_hash_size);
 241                 if (r < 0)
 242                         return r;
 243         }
 244
 245         if (!name)
 246                 return 0;
 247
 248         dmd.target = DM_VERITY;
 249         dmd.data_device = crypt_get_device_name(cd);
 250         dmd.u.verity.hash_device = hash_device;
 251         dmd.u.verity.root_hash = root_hash;
 252         dmd.u.verity.root_hash_size = root_hash_size;
 253         dmd.u.verity.hash_offset = VERITY_hash_offset_block(verity_hdr),
 254         dmd.flags = activation_flags;
 255         dmd.size = verity_hdr->data_size * verity_hdr->data_block_size / 512;
 256         dmd.uuid = crypt_get_uuid(cd);
 257         dmd.u.verity.vp = verity_hdr;
 258
 259         r = device_check_and_adjust(cd, dmd.data_device, DEV_EXCL,
 260                                     &dmd.size, &offset, &dmd.flags);
 261         if (r)
 262                 return r;
 263
 264         r = dm_create_device(name, CRYPT_VERITY, &dmd, 0);
 265         if (!r && !(dm_flags() & DM_VERITY_SUPPORTED)) {
 266                 log_err(cd, _("Kernel doesn't support dm-verity mapping.\n"));
 267                 return -ENOTSUP;
 268         }
 269         if (r < 0)
 270                 return r;
 271
 272         r = dm_status_verity_ok(name);
 273         if (r < 0)
 274                 return r;
 275
 276         if (!r)
 277                 log_err(cd, _("Verity device detected corruption after activation.\n"));
 278         return 0;
 279 }