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dm crypt: add multi key capability
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This patch adds generic multikey handling to be used
in following patch for Loop-AES mode compatibility.

This patch extends mapping table to optional keycount and
implements generic multi-key capability.

With more keys defined the <key> string is divided into
several <keycount> sections and these are used for tfms.

The tfm is used according to sector offset
(sector 0->tfm[0], sector 1->tfm[1], sector N->tfm[N modulo keycount])
(only power of two values supported for keycount here).

Because of tfms per-cpu allocation, this mode can be take
a lot of memory on large smp systems.

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: Max Vozeler <max@hinterhof.net>
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@kergon
Milan Broz authored and kergon committed Jan 13, 2011
1 parent 2dc5327 commit d1f9642
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Showing 2 changed files with 70 additions and 22 deletions.
7 changes: 6 additions & 1 deletion Documentation/device-mapper/dm-crypt.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@ Parameters: <cipher> <key> <iv_offset> <device path> <offset>

<cipher>
Encryption cipher and an optional IV generation mode.
(In format cipher-chainmode-ivopts:ivmode).
(In format cipher[:keycount]-chainmode-ivopts:ivmode).
Examples:
des
aes-cbc-essiv:sha256
Expand All @@ -20,6 +20,11 @@ Parameters: <cipher> <key> <iv_offset> <device path> <offset>
Key used for encryption. It is encoded as a hexadecimal number.
You can only use key sizes that are valid for the selected cipher.

<keycount>
Multi-key compatibility mode. You can define <keycount> keys and
then sectors are encrypted according to their offsets (sector 0 uses key0;
sector 1 uses key1 etc.). <keycount> must be a power of two.

<iv_offset>
The IV offset is a sector count that is added to the sector number
before creating the IV.
Expand Down
85 changes: 64 additions & 21 deletions drivers/md/dm-crypt.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -101,10 +101,9 @@ enum flags { DM_CRYPT_SUSPENDED, DM_CRYPT_KEY_VALID };
*/
struct crypt_cpu {
struct ablkcipher_request *req;
struct crypto_ablkcipher *tfm;

/* ESSIV: struct crypto_cipher *essiv_tfm */
void *iv_private;
struct crypto_ablkcipher *tfms[0];
};

/*
Expand Down Expand Up @@ -143,6 +142,7 @@ struct crypt_config {
* per_cpu_ptr() only.
*/
struct crypt_cpu __percpu *cpu;
unsigned tfms_count;

/*
* Layout of each crypto request:
Expand All @@ -161,6 +161,7 @@ struct crypt_config {

unsigned long flags;
unsigned int key_size;
unsigned int key_parts;
u8 key[0];
};

Expand All @@ -184,7 +185,7 @@ static struct crypt_cpu *this_crypt_config(struct crypt_config *cc)
*/
static struct crypto_ablkcipher *any_tfm(struct crypt_config *cc)
{
return __this_cpu_ptr(cc->cpu)->tfm;
return __this_cpu_ptr(cc->cpu)->tfms[0];
}

/*
Expand Down Expand Up @@ -567,11 +568,12 @@ static void crypt_alloc_req(struct crypt_config *cc,
struct convert_context *ctx)
{
struct crypt_cpu *this_cc = this_crypt_config(cc);
unsigned key_index = ctx->sector & (cc->tfms_count - 1);

if (!this_cc->req)
this_cc->req = mempool_alloc(cc->req_pool, GFP_NOIO);

ablkcipher_request_set_tfm(this_cc->req, this_cc->tfm);
ablkcipher_request_set_tfm(this_cc->req, this_cc->tfms[key_index]);
ablkcipher_request_set_callback(this_cc->req,
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
kcryptd_async_done, dmreq_of_req(cc, this_cc->req));
Expand Down Expand Up @@ -1097,15 +1099,48 @@ static void crypt_encode_key(char *hex, u8 *key, unsigned int size)
}
}

static void crypt_free_tfms(struct crypt_config *cc, int cpu)
{
struct crypt_cpu *cpu_cc = per_cpu_ptr(cc->cpu, cpu);
unsigned i;

for (i = 0; i < cc->tfms_count; i++)
if (cpu_cc->tfms[i] && !IS_ERR(cpu_cc->tfms[i])) {
crypto_free_ablkcipher(cpu_cc->tfms[i]);
cpu_cc->tfms[i] = NULL;
}
}

static int crypt_alloc_tfms(struct crypt_config *cc, int cpu, char *ciphermode)
{
struct crypt_cpu *cpu_cc = per_cpu_ptr(cc->cpu, cpu);
unsigned i;
int err;

for (i = 0; i < cc->tfms_count; i++) {
cpu_cc->tfms[i] = crypto_alloc_ablkcipher(ciphermode, 0, 0);
if (IS_ERR(cpu_cc->tfms[i])) {
err = PTR_ERR(cpu_cc->tfms[i]);
crypt_free_tfms(cc, cpu);
return err;
}
}

return 0;
}

static int crypt_setkey_allcpus(struct crypt_config *cc)
{
int cpu, err = 0, r;
unsigned subkey_size = cc->key_size >> ilog2(cc->tfms_count);
int cpu, err = 0, i, r;

for_each_possible_cpu(cpu) {
r = crypto_ablkcipher_setkey(per_cpu_ptr(cc->cpu, cpu)->tfm,
cc->key, cc->key_size);
if (r)
err = r;
for (i = 0; i < cc->tfms_count; i++) {
r = crypto_ablkcipher_setkey(per_cpu_ptr(cc->cpu, cpu)->tfms[i],
cc->key + (i * subkey_size), subkey_size);
if (r)
err = r;
}
}

return err;
Expand Down Expand Up @@ -1158,8 +1193,7 @@ static void crypt_dtr(struct dm_target *ti)
cpu_cc = per_cpu_ptr(cc->cpu, cpu);
if (cpu_cc->req)
mempool_free(cpu_cc->req, cc->req_pool);
if (cpu_cc->tfm)
crypto_free_ablkcipher(cpu_cc->tfm);
crypt_free_tfms(cc, cpu);
}

if (cc->bs)
Expand Down Expand Up @@ -1192,8 +1226,7 @@ static int crypt_ctr_cipher(struct dm_target *ti,
char *cipher_in, char *key)
{
struct crypt_config *cc = ti->private;
struct crypto_ablkcipher *tfm;
char *tmp, *cipher, *chainmode, *ivmode, *ivopts;
char *tmp, *cipher, *chainmode, *ivmode, *ivopts, *keycount;
char *cipher_api = NULL;
int cpu, ret = -EINVAL;

Expand All @@ -1209,10 +1242,20 @@ static int crypt_ctr_cipher(struct dm_target *ti,

/*
* Legacy dm-crypt cipher specification
* cipher-mode-iv:ivopts
* cipher[:keycount]-mode-iv:ivopts
*/
tmp = cipher_in;
cipher = strsep(&tmp, "-");
keycount = strsep(&tmp, "-");
cipher = strsep(&keycount, ":");

if (!keycount)
cc->tfms_count = 1;
else if (sscanf(keycount, "%u", &cc->tfms_count) != 1 ||
!is_power_of_2(cc->tfms_count)) {
ti->error = "Bad cipher key count specification";
return -EINVAL;
}
cc->key_parts = cc->tfms_count;

cc->cipher = kstrdup(cipher, GFP_KERNEL);
if (!cc->cipher)
Expand All @@ -1225,7 +1268,9 @@ static int crypt_ctr_cipher(struct dm_target *ti,
if (tmp)
DMWARN("Ignoring unexpected additional cipher options");

cc->cpu = alloc_percpu(struct crypt_cpu);
cc->cpu = __alloc_percpu(sizeof(*(cc->cpu)) +
cc->tfms_count * sizeof(*(cc->cpu->tfms)),
__alignof__(struct crypt_cpu));
if (!cc->cpu) {
ti->error = "Cannot allocate per cpu state";
goto bad_mem;
Expand Down Expand Up @@ -1258,13 +1303,11 @@ static int crypt_ctr_cipher(struct dm_target *ti,

/* Allocate cipher */
for_each_possible_cpu(cpu) {
tfm = crypto_alloc_ablkcipher(cipher_api, 0, 0);
if (IS_ERR(tfm)) {
ret = PTR_ERR(tfm);
ret = crypt_alloc_tfms(cc, cpu, cipher_api);
if (ret < 0) {
ti->error = "Error allocating crypto tfm";
goto bad;
}
per_cpu_ptr(cc->cpu, cpu)->tfm = tfm;
}

/* Initialize and set key */
Expand Down Expand Up @@ -1587,7 +1630,7 @@ static int crypt_iterate_devices(struct dm_target *ti,

static struct target_type crypt_target = {
.name = "crypt",
.version = {1, 9, 0},
.version = {1, 10, 0},
.module = THIS_MODULE,
.ctr = crypt_ctr,
.dtr = crypt_dtr,
Expand Down

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