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Check the parent DRBG's strength

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We currently don't support the algorithm from NIST SP 800-90C
10.1.2 to use a weaker DRBG as source

Reviewed-by: Dr. Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
GH: #5506
This commit is contained in:
Kurt Roeckx 2018-03-04 13:23:05 +01:00
parent 3bc0ab06b0
commit 35503b7cdc
5 changed files with 28 additions and 1 deletions
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2
crypto/err/openssl.txt
View file

@ -907,6 +907,7 @@ RAND_F_GET_ENTROPY:106:get_entropy
RAND_F_RAND_BYTES:100:RAND_bytes
RAND_F_RAND_DRBG_ENABLE_LOCKING:119:rand_drbg_enable_locking
RAND_F_RAND_DRBG_GENERATE:107:RAND_DRBG_generate
RAND_F_RAND_DRBG_GET_ENTROPY:120:rand_drbg_get_entropy
RAND_F_RAND_DRBG_INSTANTIATE:108:RAND_DRBG_instantiate
RAND_F_RAND_DRBG_NEW:109:RAND_DRBG_new
RAND_F_RAND_DRBG_RESEED:110:RAND_DRBG_reseed
@ -2300,6 +2301,7 @@ RAND_R_NOT_A_REGULAR_FILE:122:Not a regular file
RAND_R_NOT_INSTANTIATED:115:not instantiated
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_PRNG_NOT_SEEDED:100:PRNG not seeded
RAND_R_RANDOM_POOL_OVERFLOW:125:random pool overflow

9
crypto/rand/drbg_lib.c
View file

@ -178,6 +178,15 @@ static RAND_DRBG *rand_drbg_new(int secure,
if (RAND_DRBG_set(drbg, type, flags) == 0)
goto err;
if (parent != NULL && drbg->strength > parent->strength) {
/*
* We currently don't support the algorithm from NIST SP 800-90C
* 10.1.2 to use a weaker DRBG as source
*/
RANDerr(RAND_F_RAND_DRBG_NEW, RAND_R_PARENT_STRENGTH_TOO_WEAK);
goto err;
}
if (!RAND_DRBG_set_callbacks(drbg, rand_drbg_get_entropy,
rand_drbg_cleanup_entropy,
NULL, NULL))

4
crypto/rand/rand_err.c
View file

@ -23,6 +23,8 @@ static const ERR_STRING_DATA RAND_str_functs[] = {
"rand_drbg_enable_locking"},
{ERR_PACK(ERR_LIB_RAND, RAND_F_RAND_DRBG_GENERATE, 0),
"RAND_DRBG_generate"},
{ERR_PACK(ERR_LIB_RAND, RAND_F_RAND_DRBG_GET_ENTROPY, 0),
"rand_drbg_get_entropy"},
{ERR_PACK(ERR_LIB_RAND, RAND_F_RAND_DRBG_INSTANTIATE, 0),
"RAND_DRBG_instantiate"},
{ERR_PACK(ERR_LIB_RAND, RAND_F_RAND_DRBG_NEW, 0), "RAND_DRBG_new"},
@ -86,6 +88,8 @@ static const ERR_STRING_DATA RAND_str_reasons[] = {
"no drbg implementation selected"},
{ERR_PACK(ERR_LIB_RAND, 0, RAND_R_PARENT_LOCKING_NOT_ENABLED),
"parent locking not enabled"},
{ERR_PACK(ERR_LIB_RAND, 0, RAND_R_PARENT_STRENGTH_TOO_WEAK),
"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_PRNG_NOT_SEEDED), "PRNG not seeded"},

12
crypto/rand/rand_lib.c
View file

@ -176,8 +176,18 @@ size_t rand_drbg_get_entropy(RAND_DRBG *drbg,
{
size_t ret = 0;
size_t entropy_available = 0;
RAND_POOL *pool = RAND_POOL_new(entropy, min_len, max_len);
RAND_POOL *pool;
if (drbg->parent && drbg->strength > drbg->parent->strength) {
/*
* We currently don't support the algorithm from NIST SP 800-90C
* 10.1.2 to use a weaker DRBG as source
*/
RANDerr(RAND_F_RAND_DRBG_GET_ENTROPY, RAND_R_PARENT_STRENGTH_TOO_WEAK);
return 0;
}
pool = RAND_POOL_new(entropy, min_len, max_len);
if (pool == NULL)
return 0;

2
include/openssl/randerr.h
View file

@ -26,6 +26,7 @@ int ERR_load_RAND_strings(void);
# define RAND_F_RAND_BYTES 100
# define RAND_F_RAND_DRBG_ENABLE_LOCKING 119
# define RAND_F_RAND_DRBG_GENERATE 107
# define RAND_F_RAND_DRBG_GET_ENTROPY 120
# define RAND_F_RAND_DRBG_INSTANTIATE 108
# define RAND_F_RAND_DRBG_NEW 109
# define RAND_F_RAND_DRBG_RESEED 110
@ -67,6 +68,7 @@ int ERR_load_RAND_strings(void);
# define RAND_R_NOT_INSTANTIATED 115
# define RAND_R_NO_DRBG_IMPLEMENTATION_SELECTED 128
# 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_PRNG_NOT_SEEDED 100
# define RAND_R_RANDOM_POOL_OVERFLOW 125