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crypto: drbg - set HMAC key only when altered
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The HMAC implementation allows setting the HMAC key independently from
the hashing operation. Therefore, the key only needs to be set when a
new key is generated.

This patch increases the speed of the HMAC DRBG by at least 35% depending
on the use case.

The patch is fully CAVS tested.

Signed-off-by: Stephan Mueller <[email protected]>
Signed-off-by: Herbert Xu <[email protected]>
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@smuellerDD @herbertx
smuellerDD authored and herbertx committed Apr 5, 2016
1 parent bdb6cf9 commit 4218ebe
Showing 1 changed file with 25 additions and 14 deletions.
39 changes: 25 additions & 14 deletions crypto/drbg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -592,8 +592,10 @@ static const struct drbg_state_ops drbg_ctr_ops = {
******************************************************************/

#if defined(CONFIG_CRYPTO_DRBG_HASH) || defined(CONFIG_CRYPTO_DRBG_HMAC)
static int drbg_kcapi_hash(struct drbg_state *drbg, const unsigned char *key,
unsigned char *outval, const struct list_head *in);
static int drbg_kcapi_hash(struct drbg_state *drbg, unsigned char *outval,
const struct list_head *in);
static void drbg_kcapi_hmacsetkey(struct drbg_state *drbg,
const unsigned char *key);
static int drbg_init_hash_kernel(struct drbg_state *drbg);
static int drbg_fini_hash_kernel(struct drbg_state *drbg);
#endif /* (CONFIG_CRYPTO_DRBG_HASH || CONFIG_CRYPTO_DRBG_HMAC) */
Expand All @@ -619,9 +621,11 @@ static int drbg_hmac_update(struct drbg_state *drbg, struct list_head *seed,
LIST_HEAD(seedlist);
LIST_HEAD(vdatalist);

if (!reseed)
if (!reseed) {
/* 10.1.2.3 step 2 -- memset(0) of C is implicit with kzalloc */
memset(drbg->V, 1, drbg_statelen(drbg));
drbg_kcapi_hmacsetkey(drbg, drbg->C);
}

drbg_string_fill(&seed1, drbg->V, drbg_statelen(drbg));
list_add_tail(&seed1.list, &seedlist);
Expand All @@ -641,12 +645,13 @@ static int drbg_hmac_update(struct drbg_state *drbg, struct list_head *seed,
prefix = DRBG_PREFIX1;
/* 10.1.2.2 step 1 and 4 -- concatenation and HMAC for key */
seed2.buf = &prefix;
ret = drbg_kcapi_hash(drbg, drbg->C, drbg->C, &seedlist);
ret = drbg_kcapi_hash(drbg, drbg->C, &seedlist);
if (ret)
return ret;
drbg_kcapi_hmacsetkey(drbg, drbg->C);

/* 10.1.2.2 step 2 and 5 -- HMAC for V */
ret = drbg_kcapi_hash(drbg, drbg->C, drbg->V, &vdatalist);
ret = drbg_kcapi_hash(drbg, drbg->V, &vdatalist);
if (ret)
return ret;

Expand Down Expand Up @@ -681,7 +686,7 @@ static int drbg_hmac_generate(struct drbg_state *drbg,
while (len < buflen) {
unsigned int outlen = 0;
/* 10.1.2.5 step 4.1 */
ret = drbg_kcapi_hash(drbg, drbg->C, drbg->V, &datalist);
ret = drbg_kcapi_hash(drbg, drbg->V, &datalist);
if (ret)
return ret;
outlen = (drbg_blocklen(drbg) < (buflen - len)) ?
Expand Down Expand Up @@ -796,7 +801,7 @@ static int drbg_hash_df(struct drbg_state *drbg,
while (len < outlen) {
short blocklen = 0;
/* 10.4.1 step 4.1 */
ret = drbg_kcapi_hash(drbg, NULL, tmp, entropylist);
ret = drbg_kcapi_hash(drbg, tmp, entropylist);
if (ret)
goto out;
/* 10.4.1 step 4.2 */
Expand Down Expand Up @@ -874,7 +879,7 @@ static int drbg_hash_process_addtl(struct drbg_state *drbg,
list_add_tail(&data1.list, &datalist);
list_add_tail(&data2.list, &datalist);
list_splice_tail(addtl, &datalist);
ret = drbg_kcapi_hash(drbg, NULL, drbg->scratchpad, &datalist);
ret = drbg_kcapi_hash(drbg, drbg->scratchpad, &datalist);
if (ret)
goto out;

Expand Down Expand Up @@ -907,7 +912,7 @@ static int drbg_hash_hashgen(struct drbg_state *drbg,
while (len < buflen) {
unsigned int outlen = 0;
/* 10.1.1.4 step hashgen 4.1 */
ret = drbg_kcapi_hash(drbg, NULL, dst, &datalist);
ret = drbg_kcapi_hash(drbg, dst, &datalist);
if (ret) {
len = ret;
goto out;
Expand Down Expand Up @@ -956,7 +961,7 @@ static int drbg_hash_generate(struct drbg_state *drbg,
list_add_tail(&data1.list, &datalist);
drbg_string_fill(&data2, drbg->V, drbg_statelen(drbg));
list_add_tail(&data2.list, &datalist);
ret = drbg_kcapi_hash(drbg, NULL, drbg->scratchpad, &datalist);
ret = drbg_kcapi_hash(drbg, drbg->scratchpad, &datalist);
if (ret) {
len = ret;
goto out;
Expand Down Expand Up @@ -1600,14 +1605,20 @@ static int drbg_fini_hash_kernel(struct drbg_state *drbg)
return 0;
}

static int drbg_kcapi_hash(struct drbg_state *drbg, const unsigned char *key,
unsigned char *outval, const struct list_head *in)
static void drbg_kcapi_hmacsetkey(struct drbg_state *drbg,
const unsigned char *key)
{
struct sdesc *sdesc = (struct sdesc *)drbg->priv_data;

crypto_shash_setkey(sdesc->shash.tfm, key, drbg_statelen(drbg));
}

static int drbg_kcapi_hash(struct drbg_state *drbg, unsigned char *outval,
const struct list_head *in)
{
struct sdesc *sdesc = (struct sdesc *)drbg->priv_data;
struct drbg_string *input = NULL;

if (key)
crypto_shash_setkey(sdesc->shash.tfm, key, drbg_statelen(drbg));
crypto_shash_init(&sdesc->shash);
list_for_each_entry(input, in, list)
crypto_shash_update(&sdesc->shash, input->buf, input->len);
Expand Down

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