text: /* dsa_asn1.c */
  /*
   * Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL project
   * 2000.
   */
  /* ====================================================================
   * Copyright (c) 2000-2005 The OpenSSL Project.  All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. All advertising materials mentioning features or use of this
   *    software must display the following acknowledgment:
   *    "This product includes software developed by the OpenSSL Project
   *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
   *
   * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
   *    endorse or promote products derived from this software without
   *    prior written permission. For written permission, please contact
   *    licensing@OpenSSL.org.
   *
   * 5. Products derived from this software may not be called "OpenSSL"
   *    nor may "OpenSSL" appear in their names without prior written
   *    permission of the OpenSSL Project.
   *
   * 6. Redistributions of any form whatsoever must retain the following
   *    acknowledgment:
   *    "This product includes software developed by the OpenSSL Project
   *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
   *
   * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
   * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
   * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
   * OF THE POSSIBILITY OF SUCH DAMAGE.
   * ====================================================================
   *
   * This product includes cryptographic software written by Eric Young
   * (eay@cryptsoft.com).  This product includes software written by Tim
   * Hudson (tjh@cryptsoft.com).
   *
   */
  
  #include <stdio.h>
  #include "cryptlib.h"
  #include <openssl/dsa.h>
  #include <openssl/asn1.h>
  #include <openssl/asn1t.h>
  #include <openssl/rand.h>
  
  /* Override the default new methods */
  static int sig_cb(int operation, ASN1_VALUE **pval, const ASN1_ITEM *it,
                    void *exarg)
  {
      if (operation == ASN1_OP_NEW_PRE) {
          DSA_SIG *sig;
          sig = OPENSSL_malloc(sizeof(*sig));
          if (!sig) {
              DSAerr(DSA_F_SIG_CB, ERR_R_MALLOC_FAILURE);
              return 0;
          }
          sig->r = NULL;
          sig->s = NULL;
          *pval = (ASN1_VALUE *)sig;
          return 2;
      }
      return 1;
  }
  
  ASN1_SEQUENCE_cb(DSA_SIG, sig_cb) = {
          ASN1_SIMPLE(DSA_SIG, r, CBIGNUM),
          ASN1_SIMPLE(DSA_SIG, s, CBIGNUM)
  } ASN1_SEQUENCE_END_cb(DSA_SIG, DSA_SIG)
  
  IMPLEMENT_ASN1_FUNCTIONS_const(DSA_SIG)
  
  /* Override the default free and new methods */
  static int dsa_cb(int operation, ASN1_VALUE **pval, const ASN1_ITEM *it,
                    void *exarg)
  {
      if (operation == ASN1_OP_NEW_PRE) {
          *pval = (ASN1_VALUE *)DSA_new();
          if (*pval)
              return 2;
          return 0;
      } else if (operation == ASN1_OP_FREE_PRE) {
          DSA_free((DSA *)*pval);
          *pval = NULL;
          return 2;
      }
      return 1;
  }
  
  ASN1_SEQUENCE_cb(DSAPrivateKey, dsa_cb) = {
          ASN1_SIMPLE(DSA, version, LONG),
          ASN1_SIMPLE(DSA, p, BIGNUM),
          ASN1_SIMPLE(DSA, q, BIGNUM),
          ASN1_SIMPLE(DSA, g, BIGNUM),
          ASN1_SIMPLE(DSA, pub_key, BIGNUM),
          ASN1_SIMPLE(DSA, priv_key, BIGNUM)
  } ASN1_SEQUENCE_END_cb(DSA, DSAPrivateKey)
  
  IMPLEMENT_ASN1_ENCODE_FUNCTIONS_const_fname(DSA, DSAPrivateKey, DSAPrivateKey)
  
  ASN1_SEQUENCE_cb(DSAparams, dsa_cb) = {
          ASN1_SIMPLE(DSA, p, BIGNUM),
          ASN1_SIMPLE(DSA, q, BIGNUM),
          ASN1_SIMPLE(DSA, g, BIGNUM),
  } ASN1_SEQUENCE_END_cb(DSA, DSAparams)
  
  IMPLEMENT_ASN1_ENCODE_FUNCTIONS_const_fname(DSA, DSAparams, DSAparams)
  
  /*
   * DSA public key is a bit trickier... its effectively a CHOICE type decided
   * by a field called write_params which can either write out just the public
   * key as an INTEGER or the parameters and public key in a SEQUENCE
   */
  
  ASN1_SEQUENCE(DSAPublicKey) = {
          ASN1_SIMPLE(DSA, pub_key, BIGNUM),
          ASN1_SIMPLE(DSA, p, BIGNUM),
          ASN1_SIMPLE(DSA, q, BIGNUM),
          ASN1_SIMPLE(DSA, g, BIGNUM)
  } ASN1_SEQUENCE_END_name(DSA, DSAPublicKey)
  
  IMPLEMENT_ASN1_ENCODE_FUNCTIONS_const_fname(DSA, DSAPublicKey, DSAPublicKey)
  
  DSA *DSAparams_dup(DSA *dsa)
  {
      return ASN1_item_dup(ASN1_ITEM_rptr(DSAparams), dsa);
  }
  
  int DSA_sign(int type, const unsigned char *dgst, int dlen,
               unsigned char *sig, unsigned int *siglen, DSA *dsa)
  {
      DSA_SIG *s;
      RAND_seed(dgst, dlen);
      s = DSA_do_sign(dgst, dlen, dsa);
      if (s == NULL) {
          *siglen = 0;
          return (0);
      }
      *siglen = i2d_DSA_SIG(s, &sig);
      DSA_SIG_free(s);
      return (1);
  }
  
  /* data has already been hashed (probably with SHA or SHA-1). */
  /*-
   * returns
   *      1: correct signature
   *      0: incorrect signature
   *     -1: error
   */
  int DSA_verify(int type, const unsigned char *dgst, int dgst_len,
                 const unsigned char *sigbuf, int siglen, DSA *dsa)
  {
      DSA_SIG *s;
      const unsigned char *p = sigbuf;
      unsigned char *der = NULL;
      int derlen = -1;
      int ret = -1;
  
      s = DSA_SIG_new();
      if (s == NULL)
          return (ret);
      if (d2i_DSA_SIG(&s, &p, siglen) == NULL)
          goto err;
      /* Ensure signature uses DER and doesn't have trailing garbage */
      derlen = i2d_DSA_SIG(s, &der);
      if (derlen != siglen || memcmp(sigbuf, der, derlen))
          goto err;
      ret = DSA_do_verify(dgst, dgst_len, s, dsa);
   err:
      OPENSSL_clear_free(der, derlen);
      DSA_SIG_free(s);
      return (ret);
  }
  