| Message ID | 20211209090358.28231-19-nstange@suse.de |
|---|---|
| State | New |
| Headers | show |
| Series | crypto: dh - infrastructure for NVM in-band auth and FIPS conformance | expand |
On 12/9/21 10:03 AM, Nicolai Stange wrote: > SP800-56Arev3, sec. 5.5.2 ("Assurance of Domain-Parameter Validity") > asserts that an implementation needs to verify domain paramtere validity, > which boils down to either > - the domain parameters corresponding to some known safe-prime group > explicitly listed to be approved in the document or > - for parameters conforming to a "FIPS 186-type parameter-size set", > that the implementation needs to perform an explicit domain parameter > verification, which would require access to the "seed" and "counter" > values used in their generation. > > The latter is not easily feasible and moreover, SP800-56Arev3 states that > safe-prime groups are preferred and that FIPS 186-type parameter sets > should only be supported for backward compatibility, if it all. > > Make the dh implementations reject any domain parameters which don't > correspond to any of the approved safe-prime groups in FIPS mode. The > approved safe-prime groups are the ones specified in RFC 7919 and RFC 3526, > and given that all possible values of enum dh_group_id correspond to > either groups from these RFCs or to DH_GROUP_ID_UNKNOWN, it suffices to > make crypto_dh_decode_key() to reject any parameter set where > ->group_id == DH_GROUP_ID_UNKNOWN. > > As this change will effectively render the dh implementation unusable in > FIPS mode if neither of the CRYPTO_DH_GROUPS_RFC7919 or > CRYPTO_DH_GROUPS_RFC3526 Kconfig options enabled, make CRYPTO_DH imply > these two if CRYPTO_FIPS is set. > > Signed-off-by: Nicolai Stange <nstange@suse.de> > --- > crypto/Kconfig | 2 ++ > crypto/dh_helper.c | 4 ++++ > 2 files changed, 6 insertions(+) > Reviewed-by: Hannes Reinecke <hare@suse.de> Cheers, Hannes
diff --git a/crypto/Kconfig b/crypto/Kconfig index 578711b02bb3..571f2271ad2e 100644 --- a/crypto/Kconfig +++ b/crypto/Kconfig @@ -229,6 +229,8 @@ menuconfig CRYPTO_DH select CRYPTO_KPP select MPILIB select CRYPTO_RNG_DEFAULT + imply CRYPTO_DH_GROUPS_RFC7919 if CRYPTO_FIPS + imply CRYPTO_DH_GROUPS_RFC3526 if CRYPTO_FIPS help Generic implementation of the Diffie-Hellman algorithm. diff --git a/crypto/dh_helper.c b/crypto/dh_helper.c index b8a726b610a2..fafaf3c30bb1 100644 --- a/crypto/dh_helper.c +++ b/crypto/dh_helper.c @@ -7,6 +7,7 @@ #include <linux/export.h> #include <linux/err.h> #include <linux/string.h> +#include <linux/fips.h> #include <crypto/dh.h> #include <crypto/kpp.h> #include <crypto/rng.h> @@ -624,6 +625,9 @@ int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params) params->g_size > params->p_size) return -EINVAL; + /* Only safe-prime groups are allowed in FIPS mode. */ + if (fips_enabled && params->group_id == DH_GROUP_ID_UNKNOWN) + return -EINVAL; return 0; }
SP800-56Arev3, sec. 5.5.2 ("Assurance of Domain-Parameter Validity") asserts that an implementation needs to verify domain paramtere validity, which boils down to either - the domain parameters corresponding to some known safe-prime group explicitly listed to be approved in the document or - for parameters conforming to a "FIPS 186-type parameter-size set", that the implementation needs to perform an explicit domain parameter verification, which would require access to the "seed" and "counter" values used in their generation. The latter is not easily feasible and moreover, SP800-56Arev3 states that safe-prime groups are preferred and that FIPS 186-type parameter sets should only be supported for backward compatibility, if it all. Make the dh implementations reject any domain parameters which don't correspond to any of the approved safe-prime groups in FIPS mode. The approved safe-prime groups are the ones specified in RFC 7919 and RFC 3526, and given that all possible values of enum dh_group_id correspond to either groups from these RFCs or to DH_GROUP_ID_UNKNOWN, it suffices to make crypto_dh_decode_key() to reject any parameter set where ->group_id == DH_GROUP_ID_UNKNOWN. As this change will effectively render the dh implementation unusable in FIPS mode if neither of the CRYPTO_DH_GROUPS_RFC7919 or CRYPTO_DH_GROUPS_RFC3526 Kconfig options enabled, make CRYPTO_DH imply these two if CRYPTO_FIPS is set. Signed-off-by: Nicolai Stange <nstange@suse.de> --- crypto/Kconfig | 2 ++ crypto/dh_helper.c | 4 ++++ 2 files changed, 6 insertions(+)