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/* der2dsa.c
*
* Decoding of DSA keys in OpenSSL and X509.1 format.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2005, 2009 Niels Möller, Magnus Holmgren
* Copyright (C) 2014 Niels Möller
*
* The nettle library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The nettle library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
* MA 02111-1301, USA.
*/
#if HAVE_CONFIG_H
# include "config.h"
#endif
#include "dsa.h"
#include "bignum.h"
#include "asn1.h"
#define GET(i, x, l) \
(asn1_der_iterator_next((i)) == ASN1_ITERATOR_PRIMITIVE \
&& (i)->type == ASN1_INTEGER \
&& asn1_der_get_bignum((i), (x), (l)) \
&& mpz_sgn((x)) > 0)
/* If q_bits > 0, q is required to be of exactly this size. */
int
dsa_params_from_der_iterator(struct dsa_params *params,
unsigned max_bits, unsigned q_bits,
struct asn1_der_iterator *i)
{
/* Dss-Parms ::= SEQUENCE {
p INTEGER,
q INTEGER,
g INTEGER
}
*/
if (i->type == ASN1_INTEGER
&& asn1_der_get_bignum(i, params->p, max_bits)
&& mpz_sgn(params->p) > 0)
{
unsigned p_bits = mpz_sizeinbase (params->p, 2);
return (GET(i, params->q, q_bits ? q_bits : p_bits)
&& (q_bits == 0 || mpz_sizeinbase(params->q, 2) == q_bits)
&& mpz_cmp (params->q, params->p) < 0
&& GET(i, params->g, p_bits)
&& mpz_cmp (params->g, params->p) < 0
&& asn1_der_iterator_next(i) == ASN1_ITERATOR_END);
}
else
return 0;
}
int
dsa_public_key_from_der_iterator(const struct dsa_params *params,
mpz_t pub,
struct asn1_der_iterator *i)
{
/* DSAPublicKey ::= INTEGER
*/
return (i->type == ASN1_INTEGER
&& asn1_der_get_bignum(i, pub,
mpz_sizeinbase (params->p, 2))
&& mpz_sgn(pub) > 0
&& mpz_cmp(pub, params->p) < 0);
}
int
dsa_openssl_private_key_from_der_iterator(struct dsa_params *params,
mpz_t pub,
mpz_t priv,
unsigned p_max_bits,
struct asn1_der_iterator *i)
{
/* DSAPrivateKey ::= SEQUENCE {
version Version,
p INTEGER,
q INTEGER,
g INTEGER,
pub_key INTEGER, -- y
priv_key INTEGER, -- x
}
*/
uint32_t version;
if (i->type == ASN1_SEQUENCE
&& asn1_der_decode_constructed_last(i) == ASN1_ITERATOR_PRIMITIVE
&& i->type == ASN1_INTEGER
&& asn1_der_get_uint32(i, &version)
&& version == 0
&& GET(i, params->p, p_max_bits))
{
unsigned p_bits = mpz_sizeinbase (params->p, 2);
return (GET(i, params->q, DSA_SHA1_Q_BITS)
&& GET(i, params->g, p_bits)
&& mpz_cmp (params->g, params->p) < 0
&& GET(i, pub, p_bits)
&& mpz_cmp (pub, params->p) < 0
&& GET(i, priv, DSA_SHA1_Q_BITS)
&& asn1_der_iterator_next(i) == ASN1_ITERATOR_END);
}
else
return 0;
}
int
dsa_openssl_private_key_from_der(struct dsa_params *params,
mpz_t pub,
mpz_t priv,
unsigned p_max_bits,
size_t length, const uint8_t *data)
{
struct asn1_der_iterator i;
enum asn1_iterator_result res;
res = asn1_der_iterator_first(&i, length, data);
return (res == ASN1_ITERATOR_CONSTRUCTED
&& dsa_openssl_private_key_from_der_iterator(params, pub, priv,
p_max_bits, &i));
}
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