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crypto: drbg - add FIPS 140-2 CTRNG for noise source

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FIPS 140-2 section 4.9.2 requires a continuous self test of the noise
source. Up to kernel 4.8 drivers/char/random.c provided this continuous
self test. Afterwards it was moved to a location that is inconsistent
with the FIPS 140-2 requirements. The relevant patch was
e192be9d9a .

Thus, the FIPS 140-2 CTRNG is added to the DRBG when it obtains the
seed. This patch resurrects the function drbg_fips_continous_test that
existed some time ago and applies it to the noise sources. The patch
that removed the drbg_fips_continous_test was
b361476305 .

The Jitter RNG implements its own FIPS 140-2 self test and thus does not
need to be subjected to the test in the DRBG.

The patch contains a tiny fix to ensure proper zeroization in case of an
error during the Jitter RNG data gathering.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Yann Droneaud <ydroneaud@opteya.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Stephan Mueller 2019-05-08 16:19:24 +02:00 committed by Herbert Xu
parent a7cd942bb6
commit db07cd26ac
2 changed files with 93 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

94
crypto/drbg.c
View File

@ -219,6 +219,57 @@ static inline unsigned short drbg_sec_strength(drbg_flag_t flags)
}
}
/*
* FIPS 140-2 continuous self test for the noise source
* The test is performed on the noise source input data. Thus, the function
* implicitly knows the size of the buffer to be equal to the security
* strength.
*
* Note, this function disregards the nonce trailing the entropy data during
* initial seeding.
*
* drbg->drbg_mutex must have been taken.
*
* @drbg DRBG handle
* @entropy buffer of seed data to be checked
*
* return:
* 0 on success
* -EAGAIN on when the CTRNG is not yet primed
* < 0 on error
*/
static int drbg_fips_continuous_test(struct drbg_state *drbg,
const unsigned char *entropy)
{
unsigned short entropylen = drbg_sec_strength(drbg->core->flags);
int ret = 0;
if (!IS_ENABLED(CONFIG_CRYPTO_FIPS))
return 0;
/* skip test if we test the overall system */
if (list_empty(&drbg->test_data.list))
return 0;
/* only perform test in FIPS mode */
if (!fips_enabled)
return 0;
if (!drbg->fips_primed) {
/* Priming of FIPS test */
memcpy(drbg->prev, entropy, entropylen);
drbg->fips_primed = true;
/* priming: another round is needed */
return -EAGAIN;
}
ret = memcmp(drbg->prev, entropy, entropylen);
if (!ret)
panic("DRBG continuous self test failed\n");
memcpy(drbg->prev, entropy, entropylen);
/* the test shall pass when the two values are not equal */
return 0;
}
/*
* Convert an integer into a byte representation of this integer.
* The byte representation is big-endian
@ -998,6 +1049,22 @@ static inline int __drbg_seed(struct drbg_state *drbg, struct list_head *seed,
return ret;
}
static inline int drbg_get_random_bytes(struct drbg_state *drbg,
unsigned char *entropy,
unsigned int entropylen)
{
int ret;
do {
get_random_bytes(entropy, entropylen);
ret = drbg_fips_continuous_test(drbg, entropy);
if (ret && ret != -EAGAIN)
return ret;
} while (ret);
return 0;
}
static void drbg_async_seed(struct work_struct *work)
{
struct drbg_string data;
@ -1006,16 +1073,20 @@ static void drbg_async_seed(struct work_struct *work)
seed_work);
unsigned int entropylen = drbg_sec_strength(drbg->core->flags);
unsigned char entropy[32];
int ret;
BUG_ON(!entropylen);
BUG_ON(entropylen > sizeof(entropy));
get_random_bytes(entropy, entropylen);
drbg_string_fill(&data, entropy, entropylen);
list_add_tail(&data.list, &seedlist);
mutex_lock(&drbg->drbg_mutex);
ret = drbg_get_random_bytes(drbg, entropy, entropylen);
if (ret)
goto unlock;
/* If nonblocking pool is initialized, deactivate Jitter RNG */
crypto_free_rng(drbg->jent);
drbg->jent = NULL;
@ -1030,6 +1101,7 @@ static void drbg_async_seed(struct work_struct *work)
if (drbg->seeded)
drbg->reseed_threshold = drbg_max_requests(drbg);
unlock:
mutex_unlock(&drbg->drbg_mutex);
memzero_explicit(entropy, entropylen);
@ -1081,7 +1153,9 @@ static int drbg_seed(struct drbg_state *drbg, struct drbg_string *pers,
BUG_ON((entropylen * 2) > sizeof(entropy));
/* Get seed from in-kernel /dev/urandom */
get_random_bytes(entropy, entropylen);
ret = drbg_get_random_bytes(drbg, entropy, entropylen);
if (ret)
goto out;
if (!drbg->jent) {
drbg_string_fill(&data1, entropy, entropylen);
@ -1094,7 +1168,7 @@ static int drbg_seed(struct drbg_state *drbg, struct drbg_string *pers,
entropylen);
if (ret) {
pr_devel("DRBG: jent failed with %d\n", ret);
return ret;
goto out;
}
drbg_string_fill(&data1, entropy, entropylen * 2);
@ -1121,6 +1195,7 @@ static int drbg_seed(struct drbg_state *drbg, struct drbg_string *pers,
ret = __drbg_seed(drbg, &seedlist, reseed);
out:
memzero_explicit(entropy, entropylen * 2);
return ret;
@ -1142,6 +1217,11 @@ static inline void drbg_dealloc_state(struct drbg_state *drbg)
drbg->reseed_ctr = 0;
drbg->d_ops = NULL;
drbg->core = NULL;
if (IS_ENABLED(CONFIG_CRYPTO_FIPS)) {
kzfree(drbg->prev);
drbg->prev = NULL;
drbg->fips_primed = false;
}
}
/*
@ -1211,6 +1291,14 @@ static inline int drbg_alloc_state(struct drbg_state *drbg)
drbg->scratchpad = PTR_ALIGN(drbg->scratchpadbuf, ret + 1);
}
if (IS_ENABLED(CONFIG_CRYPTO_FIPS)) {
drbg->prev = kzalloc(drbg_sec_strength(drbg->core->flags),
GFP_KERNEL);
if (!drbg->prev)
goto fini;
drbg->fips_primed = false;
}
return 0;
fini:

2
include/crypto/drbg.h
View File

@ -129,6 +129,8 @@ struct drbg_state {
bool seeded; /* DRBG fully seeded? */
bool pr; /* Prediction resistance enabled? */
bool fips_primed; /* Continuous test primed? */
unsigned char *prev; /* FIPS 140-2 continuous test value */
struct work_struct seed_work; /* asynchronous seeding support */
struct crypto_rng *jent;
const struct drbg_state_ops *d_ops;