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dm crypt: add ability to use keys from the kernel key retention service

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The kernel key service is a generic way to store keys for the use of
other subsystems. Currently there is no way to use kernel keys in dm-crypt.
This patch aims to fix that. Instead of key userspace may pass a key
description with preceding ':'. So message that constructs encryption
mapping now looks like this:

  <cipher> [<key>|:<key_string>] <iv_offset> <dev_path> <start> [<#opt_params> <opt_params>]

where <key_string> is in format: <key_size>:<key_type>:<key_description>

Currently we only support two elementary key types: 'user' and 'logon'.
Keys may be loaded in dm-crypt either via <key_string> or using
classical method and pass the key in hex representation directly.

dm-crypt device initialised with a key passed in hex representation may be
replaced with key passed in key_string format and vice versa.

(Based on original work by Andrey Ryabinin)

Signed-off-by: Ondrej Kozina <okozina@redhat.com>
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Ondrej Kozina
2016-11-21 15:58:51 +01:00
committed by Mike Snitzer
parent 0637018dff
commit c538f6ec9f
2 changed files with 170 additions and 14 deletions
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159
drivers/md/dm-crypt.c
View File

@@ -12,6 +12,7 @@
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/key.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/mempool.h>
@@ -29,6 +30,7 @@
#include <crypto/md5.h>
#include <crypto/algapi.h>
#include <crypto/skcipher.h>
#include <keys/user-type.h>
#include <linux/device-mapper.h>
@@ -140,6 +142,7 @@ struct crypt_config {
char *cipher;
char *cipher_string;
char *key_string;
const struct crypt_iv_operations *iv_gen_ops;
union {
@@ -1484,22 +1487,134 @@ static int crypt_setkey(struct crypt_config *cc)
return err;
}
#ifdef CONFIG_KEYS
static int crypt_set_keyring_key(struct crypt_config *cc, const char *key_string)
{
char *new_key_string, *key_desc;
int ret;
struct key *key;
const struct user_key_payload *ukp;
/* look for next ':' separating key_type from key_description */
key_desc = strpbrk(key_string, ":");
if (!key_desc || key_desc == key_string || !strlen(key_desc + 1))
return -EINVAL;
if (strncmp(key_string, "logon:", key_desc - key_string + 1) &&
strncmp(key_string, "user:", key_desc - key_string + 1))
return -EINVAL;
new_key_string = kstrdup(key_string, GFP_KERNEL);
if (!new_key_string)
return -ENOMEM;
key = request_key(key_string[0] == 'l' ? &key_type_logon : &key_type_user,
key_desc + 1, NULL);
if (IS_ERR(key)) {
kzfree(new_key_string);
return PTR_ERR(key);
}
rcu_read_lock();
ukp = user_key_payload(key);
if (!ukp) {
rcu_read_unlock();
key_put(key);
kzfree(new_key_string);
return -EKEYREVOKED;
}
if (cc->key_size != ukp->datalen) {
rcu_read_unlock();
key_put(key);
kzfree(new_key_string);
return -EINVAL;
}
memcpy(cc->key, ukp->data, cc->key_size);
rcu_read_unlock();
key_put(key);
/* clear the flag since following operations may invalidate previously valid key */
clear_bit(DM_CRYPT_KEY_VALID, &cc->flags);
ret = crypt_setkey(cc);
/* wipe the kernel key payload copy in each case */
memset(cc->key, 0, cc->key_size * sizeof(u8));
if (!ret) {
set_bit(DM_CRYPT_KEY_VALID, &cc->flags);
kzfree(cc->key_string);
cc->key_string = new_key_string;
} else
kzfree(new_key_string);
return ret;
}
static int get_key_size(char **key_string)
{
char *colon, dummy;
int ret;
if (*key_string[0] != ':')
return strlen(*key_string) >> 1;
/* look for next ':' in key string */
colon = strpbrk(*key_string + 1, ":");
if (!colon)
return -EINVAL;
if (sscanf(*key_string + 1, "%u%c", &ret, &dummy) != 2 || dummy != ':')
return -EINVAL;
*key_string = colon;
/* remaining key string should be :<logon|user>:<key_desc> */
return ret;
}
#else
static int crypt_set_keyring_key(struct crypt_config *cc, const char *key_string)
{
return -EINVAL;
}
static int get_key_size(char **key_string)
{
return (*key_string[0] == ':') ? -EINVAL : strlen(*key_string) >> 1;
}
#endif
static int crypt_set_key(struct crypt_config *cc, char *key)
{
int r = -EINVAL;
int key_string_len = strlen(key);
/* The key size may not be changed. */
if (cc->key_size != (key_string_len >> 1))
goto out;
/* Hyphen (which gives a key_size of zero) means there is no key. */
if (!cc->key_size && strcmp(key, "-"))
goto out;
/* ':' means the key is in kernel keyring, short-circuit normal key processing */
if (key[0] == ':') {
r = crypt_set_keyring_key(cc, key + 1);
goto out;
}
/* clear the flag since following operations may invalidate previously valid key */
clear_bit(DM_CRYPT_KEY_VALID, &cc->flags);
/* wipe references to any kernel keyring key */
kzfree(cc->key_string);
cc->key_string = NULL;
if (cc->key_size && crypt_decode_key(cc->key, key, cc->key_size) < 0)
goto out;
@@ -1518,6 +1633,8 @@ static int crypt_wipe_key(struct crypt_config *cc)
{
clear_bit(DM_CRYPT_KEY_VALID, &cc->flags);
memset(&cc->key, 0, cc->key_size * sizeof(u8));
kzfree(cc->key_string);
cc->key_string = NULL;
return crypt_setkey(cc);
}
@@ -1555,6 +1672,7 @@ static void crypt_dtr(struct dm_target *ti)
kzfree(cc->cipher);
kzfree(cc->cipher_string);
kzfree(cc->key_string);
/* Must zero key material before freeing */
kzfree(cc);
@@ -1723,12 +1841,13 @@ bad_mem:
/*
* Construct an encryption mapping:
* <cipher> <key> <iv_offset> <dev_path> <start>
* <cipher> [<key>|:<key_size>:<user|logon>:<key_description>] <iv_offset> <dev_path> <start>
*/
static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
struct crypt_config *cc;
unsigned int key_size, opt_params;
int key_size;
unsigned int opt_params;
unsigned long long tmpll;
int ret;
size_t iv_size_padding;
@@ -1745,7 +1864,11 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
return -EINVAL;
}
key_size = strlen(argv[1]) >> 1;
key_size = get_key_size(&argv[1]);
if (key_size < 0) {
ti->error = "Cannot parse key size";
return -EINVAL;
}
cc = kzalloc(sizeof(*cc) + key_size * sizeof(u8), GFP_KERNEL);
if (!cc) {
@@ -1952,10 +2075,13 @@ static void crypt_status(struct dm_target *ti, status_type_t type,
case STATUSTYPE_TABLE:
DMEMIT("%s ", cc->cipher_string);
if (cc->key_size > 0)
for (i = 0; i < cc->key_size; i++)
DMEMIT("%02x", cc->key[i]);
else
if (cc->key_size > 0) {
if (cc->key_string)
DMEMIT(":%u:%s", cc->key_size, cc->key_string);
else
for (i = 0; i < cc->key_size; i++)
DMEMIT("%02x", cc->key[i]);
} else
DMEMIT("-");
DMEMIT(" %llu %s %llu", (unsigned long long)cc->iv_offset,
@@ -2011,7 +2137,7 @@ static void crypt_resume(struct dm_target *ti)
static int crypt_message(struct dm_target *ti, unsigned argc, char **argv)
{
struct crypt_config *cc = ti->private;
int ret = -EINVAL;
int key_size, ret = -EINVAL;
if (argc < 2)
goto error;
@@ -2022,6 +2148,13 @@ static int crypt_message(struct dm_target *ti, unsigned argc, char **argv)
return -EINVAL;
}
if (argc == 3 && !strcasecmp(argv[1], "set")) {
/* The key size may not be changed. */
key_size = get_key_size(&argv[2]);
if (key_size < 0 || cc->key_size != key_size) {
memset(argv[2], '0', strlen(argv[2]));
return -EINVAL;
}
ret = crypt_set_key(cc, argv[2]);
if (ret)
return ret;
@@ -2065,7 +2198,7 @@ static void crypt_io_hints(struct dm_target *ti, struct queue_limits *limits)
static struct target_type crypt_target = {
.name = "crypt",
.version = {1, 14, 1},
.version = {1, 15, 0},
.module = THIS_MODULE,
.ctr = crypt_ctr,
.dtr = crypt_dtr,