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ddb13b283b
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)
100 lines
2.5 KiB
C
100 lines
2.5 KiB
C
/*
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* Copyright 2017-2022 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the Apache License 2.0 (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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/* DH parameters from RFC7919 and RFC3526 */
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/*
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* DH low level APIs are deprecated for public use, but still ok for
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* internal use.
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*/
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#include "internal/deprecated.h"
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#include <stdio.h>
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#include "internal/cryptlib.h"
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#include "internal/ffc.h"
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#include "dh_local.h"
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#include <openssl/bn.h>
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#include <openssl/objects.h>
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#include "internal/nelem.h"
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#include "crypto/dh.h"
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static DH *dh_param_init(OSSL_LIB_CTX *libctx, const DH_NAMED_GROUP *group)
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{
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DH *dh = ossl_dh_new_ex(libctx);
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if (dh == NULL)
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return NULL;
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ossl_ffc_named_group_set(&dh->params, group);
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dh->params.nid = ossl_ffc_named_group_get_uid(group);
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dh->dirty_cnt++;
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return dh;
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}
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DH *ossl_dh_new_by_nid_ex(OSSL_LIB_CTX *libctx, int nid)
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{
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const DH_NAMED_GROUP *group;
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if ((group = ossl_ffc_uid_to_dh_named_group(nid)) != NULL)
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return dh_param_init(libctx, group);
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ERR_raise(ERR_LIB_DH, DH_R_INVALID_PARAMETER_NID);
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return NULL;
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}
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DH *DH_new_by_nid(int nid)
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{
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return ossl_dh_new_by_nid_ex(NULL, nid);
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}
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void ossl_dh_cache_named_group(DH *dh)
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{
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const DH_NAMED_GROUP *group;
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if (dh == NULL)
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return;
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dh->params.nid = NID_undef; /* flush cached value */
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/* Exit if p or g is not set */
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if (dh->params.p == NULL
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|| dh->params.g == NULL)
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return;
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if ((group = ossl_ffc_numbers_to_dh_named_group(dh->params.p,
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dh->params.q,
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dh->params.g)) != NULL) {
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if (dh->params.q == NULL)
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dh->params.q = (BIGNUM *)ossl_ffc_named_group_get_q(group);
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/* cache the nid and default key length */
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dh->params.nid = ossl_ffc_named_group_get_uid(group);
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dh->params.keylength = ossl_ffc_named_group_get_keylength(group);
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dh->dirty_cnt++;
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}
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}
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int ossl_dh_is_named_safe_prime_group(const DH *dh)
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{
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int id = DH_get_nid(dh);
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/*
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* Exclude RFC5114 groups (id = 1..3) since they do not have
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* q = (p - 1) / 2
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*/
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return (id > 3);
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}
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int DH_get_nid(const DH *dh)
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{
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if (dh == NULL)
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return NID_undef;
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return dh->params.nid;
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}
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