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Return error when trying to use prediction resistance

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There is a requirements of having access to a live entropy source
which we can't do with the default callbacks. If you need prediction
resistance you need to set up your own callbacks that follow the
requirements of NIST SP 800-90C.

Reviewed-by: Dr. Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
GH: #5402
This commit is contained in:
Kurt Roeckx 2018-02-18 20:55:28 +01:00
parent eb238134e0
commit 311276ffe3
4 changed files with 17 additions and 1 deletions
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2
crypto/err/openssl.txt
View file

@ -2310,6 +2310,8 @@ RAND_R_NO_DRBG_IMPLEMENTATION_SELECTED:128:no drbg implementation selected
RAND_R_PARENT_LOCKING_NOT_ENABLED:130:parent locking not enabled
RAND_R_PARENT_STRENGTH_TOO_WEAK:131:parent strength too weak
RAND_R_PERSONALISATION_STRING_TOO_LONG:116:personalisation string too long
RAND_R_PREDICTION_RESISTANCE_NOT_SUPPORTED:133:\
prediction resistance not supported
RAND_R_PRNG_NOT_SEEDED:100:PRNG not seeded
RAND_R_RANDOM_POOL_OVERFLOW:125:random pool overflow
RAND_R_REQUEST_TOO_LARGE_FOR_DRBG:117:request too large for drbg

2
crypto/rand/rand_err.c
View file

@ -94,6 +94,8 @@ static const ERR_STRING_DATA RAND_str_reasons[] = {
"parent strength too weak"},
{ERR_PACK(ERR_LIB_RAND, 0, RAND_R_PERSONALISATION_STRING_TOO_LONG),
"personalisation string too long"},
{ERR_PACK(ERR_LIB_RAND, 0, RAND_R_PREDICTION_RESISTANCE_NOT_SUPPORTED),
"prediction resistance not supported"},
{ERR_PACK(ERR_LIB_RAND, 0, RAND_R_PRNG_NOT_SEEDED), "PRNG not seeded"},
{ERR_PACK(ERR_LIB_RAND, 0, RAND_R_RANDOM_POOL_OVERFLOW),
"random pool overflow"},

13
crypto/rand/rand_lib.c
View file

@ -217,7 +217,7 @@ size_t rand_drbg_get_entropy(RAND_DRBG *drbg,
rand_drbg_lock(drbg->parent);
if (RAND_DRBG_generate(drbg->parent,
buffer, bytes_needed,
0,
prediction_resistance,
(unsigned char *)drbg, sizeof(*drbg)) != 0)
bytes = bytes_needed;
rand_drbg_unlock(drbg->parent);
@ -226,6 +226,17 @@ size_t rand_drbg_get_entropy(RAND_DRBG *drbg,
}
} else {
if (prediction_resistance) {
/*
* We don't have any entropy sources that comply with the NIST
* standard to provide prediction resistance (see NIST SP 800-90C,
* Section 5.4).
*/
RANDerr(RAND_F_RAND_DRBG_GET_ENTROPY,
RAND_R_PREDICTION_RESISTANCE_NOT_SUPPORTED);
return 0;
}
/* Get entropy by polling system entropy sources. */
entropy_available = rand_pool_acquire_entropy(pool);
}

1
include/openssl/randerr.h
View file

@ -71,6 +71,7 @@ int ERR_load_RAND_strings(void);
# define RAND_R_PARENT_LOCKING_NOT_ENABLED 130
# define RAND_R_PARENT_STRENGTH_TOO_WEAK 131
# define RAND_R_PERSONALISATION_STRING_TOO_LONG 116
# define RAND_R_PREDICTION_RESISTANCE_NOT_SUPPORTED 133
# define RAND_R_PRNG_NOT_SEEDED 100
# define RAND_R_RANDOM_POOL_OVERFLOW 125
# define RAND_R_REQUEST_TOO_LARGE_FOR_DRBG 117