git.distorted.org.uk Git - u/mdw/catacomb/blob - dsa-check.c

   1 /* -*-c-*-
   2  *
   3  * $Id: dsa-check.c,v 1.2 2004/04/08 01:36:15 mdw Exp $
   4  *
   5  * Consistency checking for DSA keys
   6  *
   7  * (c) 2001 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Header files ------------------------------------------------------*/
  31
  32 #include "dh.h"
  33 #include "dsa.h"
  34 #include "dsarand.h"
  35 #include "grand.h"
  36 #include "keycheck.h"
  37 #include "mp.h"
  38 #include "mprand.h"
  39
  40 /*----- Main code ---------------------------------------------------------*/
  41
  42 /* --- @dsa_checkparam@ --- *
  43  *
  44  * Arguments:   @keycheck *kc@ = keycheck state
  45  *              @const dsa_param *dp@ = pointer to the parameter set
  46  *              @const dsa_seed *ds@ = pointer to seed information
  47  *
  48  * Returns:     Zero if all OK, or return status from function.
  49  *
  50  * Use:         Checks a set of DSA parameters for consistency and security.
  51  */
  52
  53 int dsa_checkparam(keycheck *kc, const dsa_param *dp, const dsa_seed *ds)
  54 {
  55   if (ds) {
  56     grand *r = dsarand_create(ds->p, ds->sz);
  57     mp *p = MP_NEW, *q = MP_NEW;
  58     int rc = 0;
  59     unsigned i;
  60     unsigned long n;
  61
  62     r->ops->misc(r, DSARAND_PASSES, 2);
  63     q = mprand(q, mp_bits(dp->q), r, 1);
  64     if (!mp_eq(q, dp->q) &&
  65         keycheck_report(kc, KCSEV_ERR, "q doesn't match seed provided"))
  66       rc = -1;
  67     else {
  68       n = mp_bits(dp->p);
  69       r->ops->misc(r, DSARAND_PASSES, 1);
  70       for (i = 0; i <= ds->count; i++)
  71         p = mprand(p, n, r, 0);
  72       q = mp_lsl(q, q, 1);
  73       mp_div(0, &q, p, q);
  74       p = mp_sub(p, p, q);
  75       p->v[0] |= 1;
  76       if (!mp_eq(p, dp->p) &&
  77           keycheck_report(kc, KCSEV_ERR, "p doesn't match seed provided"))
  78         rc = -1;
  79     }
  80     mp_drop(p);
  81     mp_drop(q);
  82     r->ops->destroy(r);
  83     if (rc)
  84       return (rc);
  85   }
  86   return (dh_checkparam(kc, dp, 0, 0));
  87 }
  88
  89 /*----- That's all, folks -------------------------------------------------*/