lib/verity/verity.c

   1 /*
   2  * dm-verity volume handling
   3  *
   4  * Copyright (C) 2012, 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 <fcntl.h>
  29 #include <netinet/in.h>
  30 #include <uuid/uuid.h>
  31
  32 #include "libcryptsetup.h"
  33 #include "verity.h"
  34 #include "internal.h"
  35
  36 #define VERITY_SIGNATURE "verity\0\0"
  37
  38 /* http://code.google.com/p/cryptsetup/wiki/DMVerity#Verity_superblock_format */
  39 struct verity_sb {
  40         uint8_t  signature[8];  /* "verity\0\0" */
  41         uint32_t version;       /* superblock version */
  42         uint32_t hash_type;     /* 0 - Chrome OS, 1 - normal */
  43         uint8_t  uuid[16];      /* UUID of hash device */
  44         uint8_t  algorithm[32];/* hash algorithm name */
  45         uint32_t data_block_size; /* data block in bytes */
  46         uint32_t hash_block_size; /* hash block in bytes */
  47         uint64_t data_blocks;   /* number of data blocks */
  48         uint16_t salt_size;     /* salt size */
  49         uint8_t  _pad1[6];
  50         uint8_t  salt[256];     /* salt */
  51         uint8_t  _pad2[168];
  52 } __attribute__((packed));
  53
  54 /* Read verity superblock from disk */
  55 int VERITY_read_sb(struct crypt_device *cd,
  56                    uint64_t sb_offset,
  57                    char **uuid_string,
  58                    struct crypt_params_verity *params)
  59 {
  60         const char *device = device_path(crypt_metadata_device(cd));
  61         int bsize = device_block_size(crypt_metadata_device(cd));
  62         struct verity_sb sb = {};
  63         ssize_t hdr_size = sizeof(struct verity_sb);
  64         int devfd = 0, sb_version;
  65
  66         log_dbg("Reading VERITY header of size %u on device %s, offset %" PRIu64 ".",
  67                 sizeof(struct verity_sb), device, sb_offset);
  68
  69         if (params->flags & CRYPT_VERITY_NO_HEADER) {
  70                 log_err(cd, _("Verity device doesn't use on-disk header.\n"), device);
  71                 return -EINVAL;
  72         }
  73
  74         if (sb_offset % 512) {
  75                 log_err(cd, _("Unsupported VERITY hash offset.\n"));
  76                 return -EINVAL;
  77         }
  78
  79         devfd = open(device ,O_RDONLY | O_DIRECT);
  80         if(devfd == -1) {
  81                 log_err(cd, _("Cannot open device %s.\n"), device);
  82                 return -EINVAL;
  83         }
  84
  85         if(lseek(devfd, sb_offset, SEEK_SET) < 0 ||
  86            read_blockwise(devfd, bsize, &sb, hdr_size) < hdr_size) {
  87                 close(devfd);
  88                 return -EIO;
  89         }
  90         close(devfd);
  91
  92         if (memcmp(sb.signature, VERITY_SIGNATURE, sizeof(sb.signature))) {
  93                 log_err(cd, _("Device %s is not a valid VERITY device.\n"), device);
  94                 return -EINVAL;
  95         }
  96
  97         sb_version = le32_to_cpu(sb.version);
  98         if (sb_version != 1) {
  99                 log_err(cd, _("Unsupported VERITY version %d.\n"), sb_version);
 100                 return -EINVAL;
 101         }
 102         params->hash_type = le32_to_cpu(sb.hash_type);
 103         if (params->hash_type > VERITY_MAX_HASH_TYPE) {
 104                 log_err(cd, _("Unsupported VERITY hash type %d.\n"), params->hash_type);
 105                 return -EINVAL;
 106         }
 107
 108         params->data_block_size = le32_to_cpu(sb.data_block_size);
 109         params->hash_block_size = le32_to_cpu(sb.hash_block_size);
 110         if (VERITY_BLOCK_SIZE_OK(params->data_block_size) ||
 111             VERITY_BLOCK_SIZE_OK(params->hash_block_size)) {
 112                 log_err(cd, _("Unsupported VERITY block size.\n"));
 113                 return -EINVAL;
 114         }
 115         params->data_size = le64_to_cpu(sb.data_blocks);
 116
 117         params->hash_name = strndup((const char*)sb.algorithm, sizeof(sb.algorithm));
 118         if (!params->hash_name)
 119                 return -ENOMEM;
 120         if (crypt_hash_size(params->hash_name) <= 0) {
 121                 log_err(cd, _("Hash algorithm %s not supported.\n"),
 122                         params->hash_name);
 123                 free(CONST_CAST(char*)params->hash_name);
 124                 return -EINVAL;
 125         }
 126
 127         params->salt_size = le16_to_cpu(sb.salt_size);
 128         if (params->salt_size > sizeof(sb.salt)) {
 129                 log_err(cd, _("VERITY header corrupted.\n"));
 130                 free(CONST_CAST(char*)params->hash_name);
 131                 return -EINVAL;
 132         }
 133         params->salt = malloc(params->salt_size);
 134         if (!params->salt) {
 135                 free(CONST_CAST(char*)params->hash_name);
 136                 return -ENOMEM;
 137         }
 138         memcpy(CONST_CAST(char*)params->salt, sb.salt, params->salt_size);
 139
 140         if ((*uuid_string = malloc(40)))
 141                 uuid_unparse(sb.uuid, *uuid_string);
 142
 143         params->hash_area_offset = sb_offset;
 144         return 0;
 145 }
 146
 147 /* Write verity superblock to disk */
 148 int VERITY_write_sb(struct crypt_device *cd,
 149                    uint64_t sb_offset,
 150                    const char *uuid_string,
 151                    struct crypt_params_verity *params)
 152 {
 153         const char *device = device_path(crypt_metadata_device(cd));
 154         int bsize = device_block_size(crypt_metadata_device(cd));
 155         struct verity_sb sb = {};
 156         ssize_t hdr_size = sizeof(struct verity_sb);
 157         uuid_t uuid;
 158         int r, devfd = 0;
 159
 160         log_dbg("Updating VERITY header of size %u on device %s, offset %" PRIu64 ".",
 161                 sizeof(struct verity_sb), device, sb_offset);
 162
 163         if (!uuid_string || uuid_parse(uuid_string, uuid) == -1) {
 164                 log_err(cd, _("Wrong VERITY UUID format provided.\n"), device);
 165                 return -EINVAL;
 166         }
 167
 168         if (params->flags & CRYPT_VERITY_NO_HEADER) {
 169                 log_err(cd, _("Verity device doesn't use on-disk header.\n"), device);
 170                 return -EINVAL;
 171         }
 172
 173         devfd = open(device, O_RDWR | O_DIRECT);
 174         if(devfd == -1) {
 175                 log_err(cd, _("Cannot open device %s.\n"), device);
 176                 return -EINVAL;
 177         }
 178
 179         memcpy(&sb.signature, VERITY_SIGNATURE, sizeof(sb.signature));
 180         sb.version         = cpu_to_le32(1);
 181         sb.hash_type       = cpu_to_le32(params->hash_type);
 182         sb.data_block_size = cpu_to_le32(params->data_block_size);
 183         sb.hash_block_size = cpu_to_le32(params->hash_block_size);
 184         sb.salt_size       = cpu_to_le16(params->salt_size);
 185         sb.data_blocks     = cpu_to_le64(params->data_size);
 186         strncpy((char *)sb.algorithm, params->hash_name, sizeof(sb.algorithm));
 187         memcpy(sb.salt, params->salt, params->salt_size);
 188         memcpy(sb.uuid, uuid, sizeof(sb.uuid));
 189
 190         r = write_lseek_blockwise(devfd, bsize, (char*)&sb, hdr_size, sb_offset) < hdr_size ? -EIO : 0;
 191         if (r)
 192                 log_err(cd, _("Error during update of verity header on device %s.\n"), device);
 193         close(devfd);
 194
 195         return r;
 196 }
 197
 198 /* Calculate hash offset in hash blocks */
 199 uint64_t VERITY_hash_offset_block(struct crypt_params_verity *params)
 200 {
 201         uint64_t hash_offset = params->hash_area_offset;
 202
 203         if (params->flags & CRYPT_VERITY_NO_HEADER)
 204                 return hash_offset / params->hash_block_size;
 205
 206         hash_offset += sizeof(struct verity_sb);
 207         hash_offset += params->hash_block_size - 1;
 208
 209         return hash_offset / params->hash_block_size;
 210 }
 211
 212 int VERITY_UUID_generate(struct crypt_device *cd, char **uuid_string)
 213 {
 214         uuid_t uuid;
 215
 216         if (!(*uuid_string = malloc(40)))
 217                 return -ENOMEM;
 218         uuid_generate(uuid);
 219         uuid_unparse(uuid, *uuid_string);
 220         return 0;
 221 }
 222
 223 /* Activate verity device in kernel device-mapper */
 224 int VERITY_activate(struct crypt_device *cd,
 225                      const char *name,
 226                      const char *root_hash,
 227                      size_t root_hash_size,
 228                      struct crypt_params_verity *verity_hdr,
 229                      uint32_t activation_flags)
 230 {
 231         struct crypt_dm_active_device dmd;
 232         int r;
 233
 234         log_dbg("Trying to activate VERITY device %s using hash %s.",
 235                 name ?: "[none]", verity_hdr->hash_name);
 236
 237         if (verity_hdr->flags & CRYPT_VERITY_CHECK_HASH) {
 238                 log_dbg("Verification of data in userspace required.");
 239                 r = VERITY_verify(cd, verity_hdr,
 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_data_device(cd);
 250         dmd.u.verity.hash_device = crypt_metadata_device(cd);
 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_block_adjust(cd, dmd.u.verity.hash_device, DEV_OK,
 260                                 0, NULL, NULL);
 261         if (r)
 262                 return r;
 263
 264         r = device_block_adjust(cd, dmd.data_device, DEV_EXCL,
 265                                 0, &dmd.size, &dmd.flags);
 266         if (r)
 267                 return r;
 268
 269         r = dm_create_device(cd, name, CRYPT_VERITY, &dmd, 0);
 270         if (!r && !(dm_flags() & DM_VERITY_SUPPORTED)) {
 271                 log_err(cd, _("Kernel doesn't support dm-verity mapping.\n"));
 272                 return -ENOTSUP;
 273         }
 274         if (r < 0)
 275                 return r;
 276
 277         r = dm_status_verity_ok(cd, name);
 278         if (r < 0)
 279                 return r;
 280
 281         if (!r)
 282                 log_err(cd, _("Verity device detected corruption after activation.\n"));
 283         return 0;
 284 }