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

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