der2dsa.c

   1 /* der2dsa.c
   2  *
   3  * Decoding of DSA keys in OpenSSL and X509.1 format.
   4  */
   5
   6 /* nettle, low-level cryptographics library
   7  *
   8  * Copyright (C) 2005, 2009 Niels Möller, Magnus Holmgren
   9  *
  10  * The nettle library is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU Lesser General Public License as published by
  12  * the Free Software Foundation; either version 2.1 of the License, or (at your
  13  * option) any later version.
  14  *
  15  * The nettle library is distributed in the hope that it will be useful, but
  16  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  17  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  18  * License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public License
  21  * along with the nettle library; see the file COPYING.LIB.  If not, write to
  22  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  23  * MA 02111-1301, USA.
  24  */
  25
  26 #if HAVE_CONFIG_H
  27 # include "config.h"
  28 #endif
  29
  30 #include "dsa.h"
  31
  32 #include "bignum.h"
  33 #include "asn1.h"
  34
  35 #define GET(i, x, l)                                    \
  36 (asn1_der_iterator_next((i)) == ASN1_ITERATOR_PRIMITIVE \
  37  && (i)->type == ASN1_INTEGER                           \
  38  && asn1_der_get_bignum((i), (x), (l))                  \
  39  && mpz_sgn((x)) > 0)
  40
  41 int
  42 dsa_params_from_der_iterator(struct dsa_public_key *pub,
  43                              unsigned p_max_bits,
  44                              struct asn1_der_iterator *i)
  45 {
  46   /* Dss-Parms ::= SEQUENCE {
  47          p  INTEGER,
  48          q  INTEGER,
  49          g  INTEGER
  50      }
  51   */
  52   return (i->type == ASN1_INTEGER
  53           && asn1_der_get_bignum(i, pub->p, p_max_bits)
  54           && mpz_sgn(pub->p) > 0
  55           && GET(i, pub->q, DSA_SHA1_Q_BITS)
  56           && GET(i, pub->g, p_max_bits)
  57           && asn1_der_iterator_next(i) == ASN1_ITERATOR_END);
  58 }
  59
  60 int
  61 dsa_public_key_from_der_iterator(struct dsa_public_key *pub,
  62                                  unsigned p_max_bits,
  63                                  struct asn1_der_iterator *i)
  64 {
  65   /* DSAPublicKey ::= INTEGER
  66   */
  67
  68   return (i->type == ASN1_INTEGER
  69           && asn1_der_get_bignum(i, pub->y, p_max_bits)
  70           && mpz_sgn(pub->y) > 0);
  71 }
  72
  73 int
  74 dsa_openssl_private_key_from_der_iterator(struct dsa_public_key *pub,
  75                                           struct dsa_private_key *priv,
  76                                           unsigned p_max_bits,
  77                                           struct asn1_der_iterator *i)
  78 {
  79   /* DSAPrivateKey ::= SEQUENCE {
  80          version           Version,
  81          p                 INTEGER,
  82          q                 INTEGER,
  83          g                 INTEGER,
  84          pub_key           INTEGER,  -- y
  85          priv_key          INTEGER,  -- x
  86     }
  87   */
  88
  89   uint32_t version;
  90
  91   return (i->type == ASN1_SEQUENCE
  92           && asn1_der_decode_constructed_last(i) == ASN1_ITERATOR_PRIMITIVE
  93           && i->type == ASN1_INTEGER
  94           && asn1_der_get_uint32(i, &version)
  95           && version == 0
  96           && GET(i, pub->p, p_max_bits)
  97           && GET(i, pub->q, DSA_SHA1_Q_BITS)
  98           && GET(i, pub->g, p_max_bits)
  99           && GET(i, pub->y, p_max_bits)
 100           && GET(i, priv->x, DSA_SHA1_Q_BITS)
 101           && asn1_der_iterator_next(i) == ASN1_ITERATOR_END);
 102 }
 103
 104 int
 105 dsa_openssl_private_key_from_der(struct dsa_public_key *pub,
 106                      struct dsa_private_key *priv,
 107                      unsigned p_max_bits,
 108                      unsigned length, const uint8_t *data)
 109 {
 110   struct asn1_der_iterator i;
 111   enum asn1_iterator_result res;
 112
 113   res = asn1_der_iterator_first(&i, length, data);
 114
 115   return (res == ASN1_ITERATOR_CONSTRUCTED
 116           && dsa_openssl_private_key_from_der_iterator(pub, priv, p_max_bits, &i));
 117 }