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

   1 /* -*-c-*-
   2  *
   3  * $Id: rsa-pub.c,v 1.3 2004/04/08 01:36:15 mdw Exp $
   4  *
   5  * [RSA encryption with padding *
   6  * (c) 2000 Straylight/Edgeware
   7  */
   8
   9 /*----- Licensing notice --------------------------------------------------*
  10  *
  11  * This file is part of Catacomb.
  12  *
  13  * Catacomb is free software; you can redistribute it and/or modify
  14  * it under the terms of the GNU Library General Public License as
  15  * published by the Free Software Foundation; either version 2 of the
  16  * License, or (at your option) any later version.
  17  *
  18  * Catacomb is distributed in the hope that it will be useful,
  19  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21  * GNU Library General Public License for more details.
  22  *
  23  * You should have received a copy of the GNU Library General Public
  24  * License along with Catacomb; if not, write to the Free
  25  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  26  * MA 02111-1307, USA.
  27  */
  28
  29 /*----- Header files ------------------------------------------------------*/
  30
  31 #include <mLib/alloc.h>
  32 #include <mLib/bits.h>
  33 #include <mLib/dstr.h>
  34
  35 #include "mp.h"
  36 #include "mpmont.h"
  37 #include "rsa.h"
  38
  39 /*----- Public key operations ---------------------------------------------*/
  40
  41 /* --- @rsa_pubcreate@ --- *
  42  *
  43  * Arguments:   @rsa_pubctx *rd@ = pointer to an RSA public key context
  44  *              @rsa_pub *rp@ = pointer to RSA public key
  45  *
  46  * Returns:     ---
  47  *
  48  * Use:         Initializes an RSA public-key context.
  49  */
  50
  51 void rsa_pubcreate(rsa_pubctx *rd, rsa_pub *rp)
  52 {
  53   rd->rp = rp;
  54   mpmont_create(&rd->mm, rp->n);
  55 }
  56
  57 /* --- @rsa_pubdestroy@ --- *
  58  *
  59  * Arguments:   @rsa_pubctx *rd@ = pointer to an RSA public key context
  60  *
  61  * Returns:     ---
  62  *
  63  * Use:         Destroys an RSA public-key context.
  64  */
  65
  66 void rsa_pubdestroy(rsa_pubctx *rd)
  67 {
  68   mpmont_destroy(&rd->mm);
  69 }
  70
  71 /* --- @rsa_pubop@ --- *
  72  *
  73  * Arguments:   @rsa_pubctx *rd@ = pointer to an RSA public key context
  74  *              @mp *d@ = destination
  75  *              @mp *p@ = input message
  76  *
  77  * Returns:     The transformed output message.
  78  *
  79  * Use:         Performs an RSA public key operation.
  80  */
  81
  82 mp *rsa_pubop(rsa_pubctx *rd, mp *d, mp *p)
  83 {
  84   return (mpmont_exp(&rd->mm, d, p, rd->rp->e));
  85 }
  86
  87 /* --- @rsa_qpubop@ --- *
  88  *
  89  * Arguments:   @rsa_pub *rp@ = pointer to RSA parameters
  90  *              @mp *d@ = destination
  91  *              @mp *p@ = input message
  92  *
  93  * Returns:     Correctly transformed output message.
  94  *
  95  * Use:         Performs an RSA public key operation.
  96  */
  97
  98 mp *rsa_qpubop(rsa_pub *rp, mp *d, mp *c)
  99 {
 100   rsa_pubctx rd;
 101   rsa_pubcreate(&rd, rp);
 102   d = rsa_pubop(&rd, d, c);
 103   rsa_pubdestroy(&rd);
 104   return (d);
 105 }
 106
 107 /*----- Operations with padding -------------------------------------------*/
 108
 109 /* --- @rsa_encrypt@ --- *
 110  *
 111  * Arguments:   @rsa_pubctx *rp@ = pointer to an RSA public key context
 112  *              @mp *d@ = proposed destination integer
 113  *              @const void *m@ = pointer to input message
 114  *              @size_t msz@ = size of input message
 115  *              @rsa_pad *e@ = encoding procedure
 116  *              @void *earg@ = argument pointer for encoding procedure
 117  *
 118  * Returns:     The encrypted message, as a multiprecision integer, or null
 119  *              on failure.
 120  *
 121  * Use:         Does RSA encryption.
 122  */
 123
 124 mp *rsa_encrypt(rsa_pubctx *rp, mp *d, const void *m, size_t msz,
 125                 rsa_pad *e, void *earg)
 126 {
 127   octet *p;
 128   unsigned long nb = mp_bits(rp->rp->n);
 129   size_t n = (nb + 7)/8;
 130   arena *a = d && d->a ? d->a->a : arena_global;
 131
 132   p = x_alloc(a, n);
 133   d = e(d, m, msz, p, n, nb, earg);
 134   x_free(a, p);
 135   return (d ? rsa_pubop(rp, d, d) : 0);
 136 }
 137
 138 /* --- @rsa_verify@ --- *
 139  *
 140  * Arguments:   @rsa_pubctx *rp@ = pointer to an RSA public key contxt
 141  *              @mp *s@ = the signature, as a multiprecision integer
 142  *              @const void *m@ = pointer to message to verify, or null
 143  *              @size_t msz@ = size of input message
 144  *              @dstr *d@ = pointer to output string, or null
 145  *              @rsa_vfrunpad *e@ = decoding procedure
 146  *              @void *earg@ = argument pointer for decoding procedure
 147  *
 148  * Returns:     The length of the output string if successful (0 if no output
 149  *              was wanted); negative on failure.
 150  *
 151  * Use:         Does RSA signature verification.  To use a signature scheme
 152  *              with recovery, pass in @m == 0@ and @d != 0@: the recovered
 153  *              message should appear in @d@.  To use a signature scheme with
 154  *              appendix, provide @m != 0@ and @d == 0@; the result should be
 155  *              zero for success.
 156  */
 157
 158 int rsa_verify(rsa_pubctx *rp, mp *s, const void *m, size_t msz,
 159                dstr *d, rsa_vrfunpad *e, void *earg)
 160 {
 161   mp *p = rsa_pubop(rp, MP_NEW, s);
 162   unsigned long nb = mp_bits(rp->rp->n);
 163   size_t n = (nb + 7)/8;
 164   dstr dd = DSTR_INIT;
 165   int rc;
 166
 167   /* --- Decoder protocol --- *
 168    *
 169    * We deal with two kinds of decoders: ones with message recovery and ones
 170    * with appendix.  A decoder with recovery will leave a message in the
 171    * buffer and exit nonzero: we'll check that against @m@ if provided and
 172    * just leave it otherwise.  A decoder with appendix will inspect @m@ and
 173    * return zero or @-1@ itself.
 174    */
 175
 176   if (!d) d = &dd;
 177   dstr_ensure(d, n);
 178   rc = e(p, m, msz, (octet *)d->buf + d->len, n, nb, earg);
 179   if (rc > 0 && m) {
 180     if (rc != msz || memcmp(d->buf + d->len, m, msz) != 0)
 181       rc = -1;
 182     else
 183       rc = 0;
 184   }
 185   if (rc > 0)
 186     d->len += rc;
 187   mp_drop(p);
 188   dstr_destroy(&dd);
 189   return (rc);
 190 }
 191
 192 /*----- That's all, folks -------------------------------------------------*/