openssl/crypto/ffc/ffc_backend.c
Tomas Mraz ddb13b283b Use as small dh key size as possible to support the security
Longer private key sizes unnecessarily raise the cycles needed to
compute the shared secret without any increase of the real security.

We use minimum key sizes as defined in RFC7919.

For arbitrary parameters we cannot know whether they are safe
primes (we could test but that would be too inefficient) we have
to keep generating large keys.

However we now set a small dh->length when we are generating safe prime
parameters because we know it is safe to use small keys with them.

That means users need to regenerate the parameters if they
want to take the performance advantage of small private key.

Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/18480)
2022-07-18 08:06:17 +01:00

130 lines
4.1 KiB
C

/*
* Copyright 2020-2022 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <openssl/core_names.h>
#include "internal/ffc.h"
#include "internal/sizes.h"
/*
* The intention with the "backend" source file is to offer backend support
* for legacy backends (EVP_PKEY_ASN1_METHOD and EVP_PKEY_METHOD) and provider
* implementations alike.
*/
int ossl_ffc_params_fromdata(FFC_PARAMS *ffc, const OSSL_PARAM params[])
{
const OSSL_PARAM *prm;
const OSSL_PARAM *param_p, *param_q, *param_g;
BIGNUM *p = NULL, *q = NULL, *g = NULL, *j = NULL;
int i;
if (ffc == NULL)
return 0;
prm = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_GROUP_NAME);
if (prm != NULL) {
/*
* In a no-dh build we just go straight to err because we have no
* support for this.
*/
#ifndef OPENSSL_NO_DH
const DH_NAMED_GROUP *group = NULL;
if (prm->data_type != OSSL_PARAM_UTF8_STRING
|| prm->data == NULL
|| (group = ossl_ffc_name_to_dh_named_group(prm->data)) == NULL
|| !ossl_ffc_named_group_set(ffc, group))
#endif
goto err;
}
param_p = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_FFC_P);
param_g = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_FFC_G);
param_q = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_FFC_Q);
if ((param_p != NULL && !OSSL_PARAM_get_BN(param_p, &p))
|| (param_q != NULL && !OSSL_PARAM_get_BN(param_q, &q))
|| (param_g != NULL && !OSSL_PARAM_get_BN(param_g, &g)))
goto err;
prm = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_FFC_GINDEX);
if (prm != NULL) {
if (!OSSL_PARAM_get_int(prm, &i))
goto err;
ffc->gindex = i;
}
prm = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_FFC_PCOUNTER);
if (prm != NULL) {
if (!OSSL_PARAM_get_int(prm, &i))
goto err;
ffc->pcounter = i;
}
prm = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_FFC_COFACTOR);
if (prm != NULL && !OSSL_PARAM_get_BN(prm, &j))
goto err;
prm = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_FFC_H);
if (prm != NULL) {
if (!OSSL_PARAM_get_int(prm, &i))
goto err;
ffc->h = i;
}
prm = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_FFC_SEED);
if (prm != NULL) {
if (prm->data_type != OSSL_PARAM_OCTET_STRING)
goto err;
if (!ossl_ffc_params_set_seed(ffc, prm->data, prm->data_size))
goto err;
}
prm = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_FFC_VALIDATE_PQ);
if (prm != NULL) {
if (!OSSL_PARAM_get_int(prm, &i))
goto err;
ossl_ffc_params_enable_flags(ffc, FFC_PARAM_FLAG_VALIDATE_PQ, i);
}
prm = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_FFC_VALIDATE_G);
if (prm != NULL) {
if (!OSSL_PARAM_get_int(prm, &i))
goto err;
ossl_ffc_params_enable_flags(ffc, FFC_PARAM_FLAG_VALIDATE_G, i);
}
prm = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_FFC_VALIDATE_LEGACY);
if (prm != NULL) {
if (!OSSL_PARAM_get_int(prm, &i))
goto err;
ossl_ffc_params_enable_flags(ffc, FFC_PARAM_FLAG_VALIDATE_LEGACY, i);
}
prm = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_FFC_DIGEST);
if (prm != NULL) {
const OSSL_PARAM *p1;
const char *props = NULL;
if (prm->data_type != OSSL_PARAM_UTF8_STRING)
goto err;
p1 = OSSL_PARAM_locate_const(params, OSSL_PKEY_PARAM_FFC_DIGEST_PROPS);
if (p1 != NULL) {
if (p1->data_type != OSSL_PARAM_UTF8_STRING)
goto err;
}
if (!ossl_ffc_set_digest(ffc, prm->data, props))
goto err;
}
ossl_ffc_params_set0_pqg(ffc, p, q, g);
ossl_ffc_params_set0_j(ffc, j);
return 1;
err:
BN_free(j);
BN_free(p);
BN_free(q);
BN_free(g);
return 0;
}