From: Stephan Mueller smueller@chronox.de
commit db07cd26ac6a418dc2823187958edcfdb415fa83 upstream.
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 e192be9d9a30555aae2ca1dc3aad37cba484cd4a .
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 b3614763059b82c26bdd02ffcb1c016c1132aad0 .
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 Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- crypto/drbg.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++-- include/crypto/drbg.h | 2 + 2 files changed, 93 insertions(+), 3 deletions(-)
--- a/crypto/drbg.c +++ b/crypto/drbg.c @@ -220,6 +220,57 @@ static inline unsigned short drbg_sec_st }
/* + * 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 * @@ -1000,6 +1051,22 @@ static inline int __drbg_seed(struct drb 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; @@ -1008,16 +1075,20 @@ static void drbg_async_seed(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; @@ -1032,6 +1103,7 @@ static void drbg_async_seed(struct work_ if (drbg->seeded) drbg->reseed_threshold = drbg_max_requests(drbg);
+unlock: mutex_unlock(&drbg->drbg_mutex);
memzero_explicit(entropy, entropylen); @@ -1083,7 +1155,9 @@ static int drbg_seed(struct drbg_state * 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); @@ -1096,7 +1170,7 @@ static int drbg_seed(struct drbg_state * entropylen); if (ret) { pr_devel("DRBG: jent failed with %d\n", ret); - return ret; + goto out; }
drbg_string_fill(&data1, entropy, entropylen * 2); @@ -1123,6 +1197,7 @@ static int drbg_seed(struct drbg_state *
ret = __drbg_seed(drbg, &seedlist, reseed);
+out: memzero_explicit(entropy, entropylen * 2);
return ret; @@ -1144,6 +1219,11 @@ static inline void drbg_dealloc_state(st 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; + } }
/* @@ -1213,6 +1293,14 @@ static inline int drbg_alloc_state(struc 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: --- a/include/crypto/drbg.h +++ b/include/crypto/drbg.h @@ -131,6 +131,8 @@ 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;