mdw@git.distorted.org.uk Git - catacomb/blob - pub/pkcs1.c

   1 /* -*-c-*-
   2  *
   3  * PKCS#1 1.5 packing
   4  *
   5  * (c) 2000 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 <string.h>
  31
  32 #include <mLib/bits.h>
  33 #include <mLib/dstr.h>
  34 #include <mLib/macros.h>
  35
  36 #include "ct.h"
  37 #include "grand.h"
  38 #include "rsa.h"
  39
  40 /*----- Main code ---------------------------------------------------------*/
  41
  42 /* --- @pkcs1_cryptencode@ --- *
  43  *
  44  * Arguments:   @mp *d@ = where to put the answer
  45  *              @const void *m@ = pointer to message data
  46  *              @size_t msz@ = size of message data
  47  *              @octet *b@ = spare buffer
  48  *              @size_t sz@ = size of the buffer (big enough)
  49  *              @unsigned long nbits@ = length of bits of @n@
  50  *              @void *p@ = pointer to PKCS1 parameter block
  51  *
  52  * Returns:     The encoded result, or null.
  53  *
  54  * Use:         Implements the operation @EME-PKCS1-V1_5-ENCODE@, as defined
  55  *              in PKCS#1 v. 2.0 (RFC2437).
  56  */
  57
  58 mp *pkcs1_cryptencode(mp *d, const void *m, size_t msz, octet *b, size_t sz,
  59                       unsigned long nbits, void *p)
  60 {
  61   pkcs1 *pp = p;
  62   grand *r = pp->r;
  63   octet *q;
  64   size_t i, n;
  65
  66   /* --- Ensure that the buffer is sensibly sized --- */
  67
  68   if (pp->epsz + msz + 11 > sz)
  69     return (0);
  70
  71   /* --- Allocate the buffer and fill it in --- */
  72
  73   q = b;
  74   *q++ = 0x00;
  75   *q++ = 0x02;
  76   n = sz - msz - pp->epsz - 3;
  77   GR_FILL(r, q, n);
  78   for (i = 0; i < n; i++) {
  79     if (*q == 0)
  80       *q = r->ops->range(r, 255) + 1;
  81     q++;
  82   }
  83   *q++ = 0;
  84   if (pp->ep) {
  85     memcpy(q, pp->ep, pp->epsz);
  86     q += pp->epsz;
  87   }
  88   memcpy(q, m, msz);
  89   q += msz;
  90   assert(q == b + sz);
  91
  92   /* --- Collect the result --- */
  93
  94   return (mp_loadb(d, b, sz));
  95 }
  96
  97 /* --- @pkcs1_cryptdecode@ --- *
  98  *
  99  * Arguments:   @mp *m@ = the decrypted message
 100  *              @octet *b@ = pointer to a buffer to work in
 101  *              @size_t sz@ = the size of the buffer (big enough)
 102  *              @unsigned long nbits@ = the number of bits in @n@
 103  *              @void *p@ = pointer to PKCS1 parameter block
 104  *
 105  * Returns:     The length of the output string if successful, negative on
 106  *              failure.
 107  *
 108  * Use:         Implements the operation @EME-PKCS1-V1_5-DECODE@, as defined
 109  *              in PKCS#1 v. 2.0 (RFC2437).
 110  */
 111
 112 int pkcs1_cryptdecode(mp *m, octet *b, size_t sz,
 113                       unsigned long nbits, void *p)
 114 {
 115   pkcs1 *pp = p;
 116   const octet *q, *qq;
 117   size_t n, i;
 118   uint32 goodp = 1;
 119
 120   /* --- Check the size of the block looks sane --- */
 121
 122   if (pp->epsz + 11 > sz)               /* OK: independent of ciphertext */
 123     return (-1);
 124   mp_storeb(m, b, sz);
 125   q = b;
 126   qq = q + sz;
 127
 128   /* --- Ensure that the block looks OK --- */
 129
 130   goodp &= ct_inteq(*q++, 0);
 131   goodp &= ct_inteq(*q++, 2);
 132
 133   /* --- Check the nonzero padding --- */
 134
 135   i = 0;
 136   while (*q != 0 && q < qq)
 137     i++, q++;
 138   goodp &= ct_intle(8, i);
 139   goodp &= ~ct_intle(qq - q, pp->epsz + 1);
 140   q++;
 141
 142   /* --- Check the encoding parameters --- */
 143
 144   if (pp->ep)
 145     goodp &= ct_memeq(b + ct_pick(goodp, 0, q - b), pp->ep, pp->epsz);
 146   q += pp->epsz;
 147
 148   /* --- Done --- */
 149
 150   n = qq - q;
 151   memmove(b, b + ct_pick(goodp, 1, q - b), n);
 152   return (goodp ? n : -1);
 153 }
 154
 155 /* --- @pkcs1_sigencode@ --- *
 156  *
 157  * Arguments:   @mp *d@ = where to put the answer
 158  *              @const void *m@ = pointer to message data
 159  *              @size_t msz@ = size of message data
 160  *              @octet *b@ = spare buffer
 161  *              @size_t sz@ = size of the buffer (big enough)
 162  *              @unsigned long nbits@ = length of bits of @n@
 163  *              @void *p@ = pointer to PKCS1 parameter block
 164  *
 165  * Returns:     The encoded message representative, or null.
 166  *
 167  * Use:         Implements the operation @EMSA-PKCS1-V1_5-ENCODE@, as defined
 168  *              in PKCS#1 v. 2.0 (RFC2437).
 169  */
 170
 171 mp *pkcs1_sigencode(mp *d, const void *m, size_t msz, octet *b, size_t sz,
 172                     unsigned long nbits, void *p)
 173 {
 174   pkcs1 *pp = p;
 175   octet *q;
 176   size_t n;
 177
 178   /* --- Ensure that the buffer is sensibly sized --- */
 179
 180   if (pp->epsz + msz + 11 > sz)
 181     return (0);
 182
 183   /* --- Fill in the buffer --- */
 184
 185   q = b;
 186   *q++ = 0x00;
 187   *q++ = 0x01;
 188   n = sz - msz - pp->epsz - 3;
 189   memset(q, 0xff, n);
 190   q += n;
 191   *q++ = 0;
 192   if (pp->ep) {
 193     memcpy(q, pp->ep, pp->epsz);
 194     q += pp->epsz;
 195   }
 196   memcpy(q, m, msz);
 197   q += msz;
 198   assert(q == b + sz);
 199   return (mp_loadb(d, b, sz));
 200 }
 201
 202 /* --- @pkcs1_sigdecode@ --- *
 203  *
 204  * Arguments:   @mp *s@ = the message representative
 205  *              @const void *m@ = the original message, or null (ignored)
 206  *              @size_t msz@ = the message size (ignored)
 207  *              @octet *b@ = a scratch buffer
 208  *              @size_t sz@ = size of the buffer (large enough)
 209  *              @unsigned long nbits@ = number of bits in @n@
 210  *              @void *p@ = pointer to PKCS1 parameters
 211  *
 212  * Returns:     The length of the output string if successful, negative on
 213  *              failure.
 214  *
 215  * Use:         Implements the operation @EMSA-PKCS1-V1_5-DECODE@, as defined
 216  *              in PKCS#1 v. 2.0 (RFC2437).
 217  */
 218
 219 int pkcs1_sigdecode(mp *s, const void *m, size_t msz, octet *b, size_t sz,
 220                     unsigned long nbits, void *p)
 221 {
 222   pkcs1 *pp = p;
 223   const octet *q, *qq;
 224   size_t i, n;
 225
 226   /* --- Check the size of the block looks sane --- */
 227
 228   if (pp->epsz + 10 > sz)
 229     return (-1);
 230   mp_storeb(s, b, sz);
 231   q = b;
 232   qq = q + sz;
 233
 234   /* --- Ensure that the block looks OK --- */
 235
 236   if (*q++ != 0x00 || *q++ != 0x01)
 237     return (-1);
 238
 239   /* --- Check the padding --- */
 240
 241   i = 0;
 242   while (*q == 0xff && q < qq)
 243     i++, q++;
 244   if (i < 8 || qq - q < pp->epsz + 1 || *q++ != 0)
 245     return (-1);
 246
 247   /* --- Check the encoding parameters --- */
 248
 249   if (pp->ep && MEMCMP(q, !=, pp->ep, pp->epsz))
 250     return (-1);
 251   q += pp->epsz;
 252
 253   /* --- Done --- */
 254
 255   n = qq - q;
 256   memmove(b, q, n);
 257   return (n);
 258 }
 259
 260 /*----- That's all, folks -------------------------------------------------*/