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grub/grub-core/disk/luks.c

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/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2003,2007,2010,2011 Free Software Foundation, Inc.
*
* GRUB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GRUB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
*/
#include <grub/types.h>
#include <grub/misc.h>
#include <grub/mm.h>
#include <grub/dl.h>
#include <grub/err.h>
#include <grub/disk.h>
#include <grub/crypto.h>
#include <grub/extcmd.h>
#include <grub/i18n.h>
GRUB_MOD_LICENSE ("GPLv3+");
#define MAX_PASSPHRASE 256
#define LUKS_KEY_ENABLED 0x00AC71F3
#define LUKS_STRIPES 4000
/* On disk LUKS header */
struct grub_luks_phdr
{
grub_uint8_t magic[6];
#define LUKS_MAGIC "LUKS\xBA\xBE"
grub_uint16_t version;
char cipherName[32];
char cipherMode[32];
char hashSpec[32];
grub_uint32_t payloadOffset;
grub_uint32_t keyBytes;
grub_uint8_t mkDigest[20];
grub_uint8_t mkDigestSalt[32];
grub_uint32_t mkDigestIterations;
char uuid[40];
struct
{
grub_uint32_t active;
grub_uint32_t passwordIterations;
grub_uint8_t passwordSalt[32];
grub_uint32_t keyMaterialOffset;
grub_uint32_t stripes;
} keyblock[8];
} __attribute__ ((packed));
typedef struct grub_luks_phdr *grub_luks_phdr_t;
typedef enum
{
GRUB_LUKS_MODE_ECB,
GRUB_LUKS_MODE_CBC_PLAIN,
GRUB_LUKS_MODE_CBC_ESSIV
} luks_mode_t;
struct grub_luks
{
char *source;
grub_uint32_t offset;
grub_disk_t source_disk;
int ref;
grub_crypto_cipher_handle_t cipher;
grub_crypto_cipher_handle_t essiv_cipher;
const gcry_md_spec_t *essiv_hash, *hash;
luks_mode_t mode;
unsigned long id, source_id;
enum grub_disk_dev_id source_dev_id;
char uuid[sizeof (((struct grub_luks_phdr *) 0)->uuid) + 1];
struct grub_luks *next;
};
typedef struct grub_luks *grub_luks_t;
static grub_luks_t luks_list = NULL;
static grub_uint8_t n = 0;
gcry_err_code_t AF_merge (const gcry_md_spec_t * hash, grub_uint8_t * src,
grub_uint8_t * dst, grub_size_t blocksize,
grub_size_t blocknumbers);
static const struct grub_arg_option options[] =
{
{"uuid", 'u', 0, N_("Mount by UUID."), 0, 0},
{0, 0, 0, 0, 0, 0}
};
static gcry_err_code_t
luks_decrypt (grub_crypto_cipher_handle_t cipher, luks_mode_t mode,
grub_uint8_t * data, grub_size_t len,
grub_size_t sector, grub_crypto_cipher_handle_t essiv_cipher)
{
grub_size_t i;
gcry_err_code_t err;
switch (mode)
{
case GRUB_LUKS_MODE_ECB:
return grub_crypto_ecb_decrypt (cipher, data, data, len);
case GRUB_LUKS_MODE_CBC_PLAIN:
for (i = 0; i < len; i += GRUB_DISK_SECTOR_SIZE)
{
grub_uint32_t iv[(cipher->cipher->blocksize
+ sizeof (grub_uint32_t) - 1)
/ sizeof (grub_uint32_t)];
grub_memset (iv, 0, cipher->cipher->blocksize);
iv[0] = grub_cpu_to_le32 (sector & 0xFFFFFFFF);
err = grub_crypto_cbc_decrypt (cipher, data + i, data + i,
GRUB_DISK_SECTOR_SIZE, iv);
if (err)
return err;
sector++;
}
return GPG_ERR_NO_ERROR;
case GRUB_LUKS_MODE_CBC_ESSIV:
for (i = 0; i < len; i += GRUB_DISK_SECTOR_SIZE)
{
grub_uint32_t iv[(cipher->cipher->blocksize
+ sizeof (grub_uint32_t) - 1)
/ sizeof (grub_uint32_t)];
grub_memset (iv, 0, cipher->cipher->blocksize);
iv[0] = grub_cpu_to_le32 (sector & 0xFFFFFFFF);
err =
grub_crypto_ecb_encrypt (essiv_cipher, iv, iv,
cipher->cipher->blocksize);
if (err)
return err;
err = grub_crypto_cbc_decrypt (cipher, data + i, data + i,
GRUB_DISK_SECTOR_SIZE, iv);
if (err)
return err;
sector++;
}
return GPG_ERR_NO_ERROR;
default:
return GPG_ERR_NOT_IMPLEMENTED;
}
}
static int check_uuid, have_it;
static char *search_uuid;
static grub_luks_t
configure_ciphers (const struct grub_luks_phdr *header)
{
grub_luks_t newdev;
const char *iptr;
char *optr;
char uuid[sizeof (header->uuid) + 1];
char ciphername[sizeof (header->cipherName) + 1];
char ciphermode[sizeof (header->cipherMode) + 1];
char hashspec[sizeof (header->hashSpec) + 1];
grub_crypto_cipher_handle_t cipher = NULL, essiv_cipher = NULL;
const gcry_md_spec_t *hash = NULL, *essiv_hash = NULL;
const struct gcry_cipher_spec *ciph;
luks_mode_t mode;
/* Look for LUKS magic sequence. */
if (grub_memcmp (header->magic, LUKS_MAGIC, sizeof (header->magic))
|| grub_be_to_cpu16 (header->version) != 1)
return NULL;
optr = uuid;
for (iptr = header->uuid; iptr < &header->uuid[ARRAY_SIZE (header->uuid)];
iptr++)
{
if (*iptr != '-')
*optr++ = *iptr;
}
*optr = 0;
if (check_uuid && grub_strcasecmp (search_uuid, uuid) != 0)
{
grub_dprintf ("luks", "%s != %s", uuid, search_uuid);
return NULL;
}
/* Make sure that strings are null terminated. */
grub_memcpy (ciphername, header->cipherName, sizeof (header->cipherName));
ciphername[sizeof (header->cipherName)] = 0;
grub_memcpy (ciphermode, header->cipherMode, sizeof (header->cipherMode));
ciphermode[sizeof (header->cipherMode)] = 0;
grub_memcpy (hashspec, header->hashSpec, sizeof (header->hashSpec));
hashspec[sizeof (header->hashSpec)] = 0;
ciph = grub_crypto_lookup_cipher_by_name (ciphername);
if (!ciph)
{
grub_error (GRUB_ERR_FILE_NOT_FOUND, "Cipher %s isn't available",
ciphername);
return NULL;
}
/* Configure the cipher used for the bulk data. */
cipher = grub_crypto_cipher_open (ciph);
if (!cipher)
return NULL;
if (grub_be_to_cpu32 (header->keyBytes) > 1024)
{
grub_error (GRUB_ERR_BAD_ARGUMENT, "invalid keysize %d",
grub_be_to_cpu32 (header->keyBytes));
return NULL;
}
/* Configure the cipher mode. */
if (grub_strncmp (ciphermode, "ecb", 3) == 0)
mode = GRUB_LUKS_MODE_ECB;
else if (grub_strncmp (ciphermode, "cbc-plain", 9) == 0
|| grub_strncmp (ciphermode, "plain", 5) == 0)
mode = GRUB_LUKS_MODE_CBC_PLAIN;
else if (grub_strncmp (ciphermode, "cbc-essiv", 9) == 0)
{
mode = GRUB_LUKS_MODE_CBC_ESSIV;
char *hash_str = ciphermode + 10;
/* Configure the hash and cipher used for ESSIV. */
essiv_hash = grub_crypto_lookup_md_by_name (hash_str);
if (!essiv_hash)
{
grub_crypto_cipher_close (cipher);
grub_error (GRUB_ERR_FILE_NOT_FOUND,
"Couldn't load %s hash", hash_str);
return NULL;
}
essiv_cipher = grub_crypto_cipher_open (ciph);
if (!cipher)
{
grub_crypto_cipher_close (cipher);
return NULL;
}
}
else
{
grub_crypto_cipher_close (cipher);
grub_error (GRUB_ERR_BAD_ARGUMENT, "Unknown cipher mode: %s",
ciphermode);
return NULL;
}
/* Configure the hash used for the AF splitter and HMAC. */
hash = grub_crypto_lookup_md_by_name (hashspec);
if (!hash)
{
grub_crypto_cipher_close (cipher);
grub_crypto_cipher_close (essiv_cipher);
grub_error (GRUB_ERR_FILE_NOT_FOUND, "Couldn't load %s hash",
hashspec);
return NULL;
}
newdev = grub_zalloc (sizeof (struct grub_luks));
if (!newdev)
return NULL;
newdev->cipher = cipher;
newdev->offset = grub_be_to_cpu32 (header->payloadOffset);
newdev->source_disk = NULL;
newdev->mode = mode;
newdev->essiv_cipher = essiv_cipher;
newdev->essiv_hash = essiv_hash;
newdev->hash = hash;
newdev->id = n++;
grub_memcpy (newdev->uuid, uuid, sizeof (newdev->uuid));
return newdev;
}
static grub_err_t
luks_recover_key (grub_luks_t dev, const struct grub_luks_phdr *header,
const char *name, grub_disk_t source)
{
grub_size_t keysize = grub_be_to_cpu32 (header->keyBytes);
grub_uint8_t candidate_key[keysize];
grub_uint8_t digest[keysize];
grub_uint8_t *hashed_key = NULL;
grub_uint8_t *split_key = NULL;
char passphrase[MAX_PASSPHRASE] = "";
grub_uint8_t candidate_digest[sizeof (header->mkDigest)];
unsigned i;
grub_size_t essiv_keysize = 0;
grub_size_t length;
grub_err_t err;
if (dev->mode == GRUB_LUKS_MODE_CBC_ESSIV)
essiv_keysize = dev->essiv_hash->mdlen;
hashed_key = grub_malloc (dev->essiv_hash->mdlen);
if (!hashed_key)
{
return grub_errno;
}
grub_printf ("Attempting to decrypt master key...\n");
split_key = grub_malloc (keysize * LUKS_STRIPES);
if (!split_key)
{
grub_free (hashed_key);
return grub_errno;
}
/* Get the passphrase from the user. */
grub_printf ("Enter passphrase for %s (%s): ", name, dev->uuid);
if (!grub_password_get (passphrase, MAX_PASSPHRASE))
{
grub_free (hashed_key);
grub_free (split_key);
return grub_error (GRUB_ERR_BAD_ARGUMENT, "Passphrase not supplied");
}
/* Try to recover master key from each active keyslot. */
for (i = 0; i < ARRAY_SIZE (header->keyblock); i++)
{
gcry_err_code_t gcry_err;
/* Check if keyslot is enabled. */
if (grub_be_to_cpu32 (header->keyblock[i].active) != LUKS_KEY_ENABLED)
continue;
grub_dprintf ("luks", "Trying keyslot %d\n", i);
/* Calculate the PBKDF2 of the user supplied passphrase. */
gcry_err = grub_crypto_pbkdf2 (dev->hash, (grub_uint8_t *) passphrase,
grub_strlen (passphrase),
header->keyblock[i].passwordSalt,
sizeof (header->
keyblock[i].passwordSalt),
grub_be_to_cpu32 (header->keyblock[i].
passwordIterations),
digest, keysize);
if (gcry_err)
{
grub_free (hashed_key);
grub_free (split_key);
return grub_crypto_gcry_error (gcry_err);
}
grub_dprintf ("luks", "PBKDF2 done\n");
/* Set the PBKDF2 output as the cipher key. */
gcry_err = grub_crypto_cipher_set_key (dev->cipher, digest, keysize);
if (gcry_err)
{
grub_free (hashed_key);
grub_free (split_key);
return grub_crypto_gcry_error (gcry_err);
}
/* Configure ESSIV if necessary. */
if (dev->mode == GRUB_LUKS_MODE_CBC_ESSIV)
{
grub_crypto_hash (dev->essiv_hash, hashed_key, digest, keysize);
grub_crypto_cipher_set_key (dev->essiv_cipher, hashed_key,
essiv_keysize);
}
length =
grub_be_to_cpu32 (header->keyBytes) *
grub_be_to_cpu32 (header->keyblock[i].stripes);
/* Read and decrypt the key material from the disk. */
err = grub_disk_read (source,
grub_be_to_cpu32 (header->keyblock
[i].keyMaterialOffset), 0,
length, split_key);
if (err)
{
grub_free (hashed_key);
grub_free (split_key);
return err;
}
gcry_err = luks_decrypt (dev->cipher, dev->mode, split_key,
length, 0, dev->essiv_cipher);
if (gcry_err)
{
grub_free (hashed_key);
grub_free (split_key);
return grub_crypto_gcry_error (gcry_err);
}
/* Merge the decrypted key material to get the candidate master key. */
gcry_err = AF_merge (dev->hash, split_key, candidate_key, keysize,
grub_be_to_cpu32 (header->keyblock[i].stripes));
if (gcry_err)
{
grub_free (hashed_key);
grub_free (split_key);
return grub_crypto_gcry_error (gcry_err);
}
grub_dprintf ("luks", "candidate key recovered\n");
/* Calculate the PBKDF2 of the candidate master key. */
gcry_err = grub_crypto_pbkdf2 (dev->hash, candidate_key,
grub_be_to_cpu32 (header->keyBytes),
header->mkDigestSalt,
sizeof (header->mkDigestSalt),
grub_be_to_cpu32
(header->mkDigestIterations),
candidate_digest,
sizeof (candidate_digest));
if (gcry_err)
{
grub_free (hashed_key);
grub_free (split_key);
return grub_crypto_gcry_error (gcry_err);
}
/* Compare the calculated PBKDF2 to the digest stored
in the header to see if it's correct. */
if (grub_memcmp (candidate_digest, header->mkDigest,
sizeof (header->mkDigest)) != 0)
continue;
grub_printf ("Slot %d opened\n", i);
/* Set the master key. */
gcry_err = grub_crypto_cipher_set_key (dev->cipher,
candidate_key, keysize);
if (gcry_err)
{
grub_free (hashed_key);
grub_free (split_key);
return grub_crypto_gcry_error (gcry_err);
}
/* Configure ESSIV if necessary. */
if (dev->mode == GRUB_LUKS_MODE_CBC_ESSIV)
{
grub_crypto_hash (dev->essiv_hash, hashed_key,
candidate_key, keysize);
gcry_err =
grub_crypto_cipher_set_key (dev->essiv_cipher, hashed_key,
essiv_keysize);
if (gcry_err)
{
grub_free (hashed_key);
grub_free (split_key);
return grub_crypto_gcry_error (gcry_err);
}
}
grub_free (split_key);
grub_free (hashed_key);
return GRUB_ERR_NONE;
}
return GRUB_ACCESS_DENIED;
}
static void
luks_close (grub_luks_t luks)
{
grub_crypto_cipher_close (luks->cipher);
grub_crypto_cipher_close (luks->essiv_cipher);
grub_free (luks);
}
static grub_err_t
grub_luks_scan_device_real (const char *name, grub_disk_t source)
{
grub_err_t err;
struct grub_luks_phdr header;
grub_luks_t newdev;
/* Read the LUKS header. */
err = grub_disk_read (source, 0, 0, sizeof (header), &header);
if (err)
return err;
newdev = configure_ciphers (&header);
if (!newdev)
return grub_errno;
err = luks_recover_key (newdev, &header, name, source);
if (err)
{
luks_close (newdev);
return err;
}
newdev->source = grub_strdup (name);
newdev->source_id = source->id;
newdev->source_dev_id = source->dev->id;
newdev->next = luks_list;
luks_list = newdev;
have_it = 1;
return GRUB_ERR_NONE;
}
static int
grub_luks_scan_device (const char *name)
{
grub_err_t err;
grub_disk_t source;
/* Try to open disk. */
source = grub_disk_open (name);
if (!source)
return grub_errno;
err = grub_luks_scan_device_real (name, source);
grub_disk_close (source);
if (err)
grub_print_error ();
return have_it && check_uuid ? 0 : 1;
}
static int
grub_luks_iterate (int (*hook) (const char *name),
grub_disk_pull_t pull)
{
grub_luks_t i;
if (pull != GRUB_DISK_PULL_NONE)
return 0;
for (i = luks_list; i != NULL; i = i->next)
{
char buf[30];
grub_snprintf (buf, sizeof (buf), "luks%lu", i->id);
if (hook (buf))
return 1;
}
return GRUB_ERR_NONE;
}
static grub_err_t
grub_luks_open (const char *name, grub_disk_t disk,
grub_disk_pull_t pull __attribute__ ((unused)))
{
grub_luks_t dev;
if (grub_memcmp (name, "luks", sizeof ("luks") - 1) != 0)
return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "No such device");
if (grub_memcmp (name, "luksuuid/", sizeof ("luksuuid/") - 1) == 0)
{
for (dev = luks_list; dev != NULL; dev = dev->next)
if (grub_strcasecmp (name + sizeof ("luksuuid/") - 1, dev->uuid) == 0)
break;
}
else
{
unsigned long id = grub_strtoul (name + sizeof ("luks") - 1, 0, 0);
if (grub_errno)
return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "No such device");
/* Search for requested device in the list of LUKS devices. */
for (dev = luks_list; dev != NULL; dev = dev->next)
if (dev->id == id)
break;
}
if (!dev)
return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "No such device");
if (!dev->source_disk)
{
grub_dprintf ("luks", "Opening device %s\n", name);
/* Try to open the source disk and populate the requested disk. */
dev->source_disk = grub_disk_open (dev->source);
if (!dev->source_disk)
return grub_errno;
}
disk->data = dev;
disk->total_sectors = grub_disk_get_size (dev->source_disk) - dev->offset;
disk->id = dev->id;
dev->ref++;
return GRUB_ERR_NONE;
}
static void
grub_luks_close (grub_disk_t disk)
{
grub_luks_t dev = (grub_luks_t) disk->data;
grub_dprintf ("luks", "Closing disk\n");
dev->ref--;
if (dev->ref == 0)
{
grub_disk_close (dev->source_disk);
dev->source_disk = NULL;
}
}
static grub_err_t
grub_luks_read (grub_disk_t disk, grub_disk_addr_t sector,
grub_size_t size, char *buf)
{
grub_luks_t dev = (grub_luks_t) disk->data;
grub_err_t err;
grub_dprintf ("luks",
"Reading %" PRIuGRUB_SIZE " sectors from sector 0x%"
PRIxGRUB_UINT64_T " with offset of %" PRIuGRUB_UINT32_T "\n",
size, sector, dev->offset);
err = grub_disk_read (dev->source_disk, sector + dev->offset, 0,
size << GRUB_DISK_SECTOR_BITS, buf);
if (err)
{
grub_dprintf ("luks", "grub_disk_read failed with error %d\n", err);
return err;
}
return grub_crypto_gcry_error (luks_decrypt (dev->cipher,
dev->mode,
(grub_uint8_t *) buf,
size << GRUB_DISK_SECTOR_BITS,
sector, dev->essiv_cipher));
}
static grub_err_t
grub_luks_write (grub_disk_t disk __attribute ((unused)),
grub_disk_addr_t sector __attribute ((unused)),
grub_size_t size __attribute ((unused)),
const char *buf __attribute ((unused)))
{
return GRUB_ERR_NOT_IMPLEMENTED_YET;
}
static void
luks_cleanup (void)
{
grub_luks_t dev = luks_list;
grub_luks_t tmp;
while (dev != NULL)
{
grub_free (dev->source);
grub_free (dev->cipher);
grub_free (dev->essiv_cipher);
tmp = dev->next;
grub_free (dev);
dev = tmp;
}
}
static grub_err_t
grub_cmd_luksmount (grub_extcmd_context_t ctxt, int argc, char **args)
{
struct grub_arg_list *state = ctxt->state;
if (argc < 1)
return grub_error (GRUB_ERR_BAD_ARGUMENT, "device name required");
have_it = 0;
if (state[0].set)
{
grub_luks_t dev;
for (dev = luks_list; dev != NULL; dev = dev->next)
if (grub_strcasecmp (dev->uuid, args[0]) == 0)
{
grub_dprintf ("luks", "already mounted as luks%lu\n", dev->id);
return GRUB_ERR_NONE;
}
check_uuid = 1;
search_uuid = args[0];
grub_device_iterate (&grub_luks_scan_device);
search_uuid = NULL;
if (!have_it)
return grub_error (GRUB_ERR_BAD_ARGUMENT, "no such luks found");
return GRUB_ERR_NONE;
}
else
{
grub_err_t err;
grub_disk_t disk;
grub_luks_t dev;
check_uuid = 0;
search_uuid = NULL;
disk = grub_disk_open (args[0]);
if (!disk)
return grub_errno;
for (dev = luks_list; dev != NULL; dev = dev->next)
if (dev->source_id == disk->id && dev->source_dev_id == disk->dev->id)
{
grub_dprintf ("luks", "already mounted as luks%lu\n", dev->id);
grub_disk_close (disk);
return GRUB_ERR_NONE;
}
err = grub_luks_scan_device_real (args[0], disk);
grub_disk_close (disk);
return err;
}
}
static struct grub_disk_dev grub_luks_dev = {
.name = "luks",
.id = GRUB_DISK_DEVICE_LUKS_ID,
.iterate = grub_luks_iterate,
.open = grub_luks_open,
.close = grub_luks_close,
.read = grub_luks_read,
.write = grub_luks_write,
.next = 0
};
static grub_extcmd_t cmd;
GRUB_MOD_INIT (luks)
{
cmd = grub_register_extcmd ("luksmount", grub_cmd_luksmount, 0,
N_("SOURCE|-u UUID"),
N_("Mount a LUKS device."), options);
grub_disk_dev_register (&grub_luks_dev);
}
GRUB_MOD_FINI (luks)
{
grub_unregister_extcmd (cmd);
grub_disk_dev_unregister (&grub_luks_dev);
luks_cleanup ();
}
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