lib/mpi/mpicoder.c

   1 /* mpicoder.c  -  Coder for the external representation of MPIs
   2  * Copyright (C) 1998, 1999 Free Software Foundation, Inc.
   3  *
   4  * This file is part of GnuPG.
   5  *
   6  * GnuPG is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * GnuPG is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  19  */
  20
  21 #include "mpi-internal.h"
  22
  23 #define MAX_EXTERN_MPI_BITS 16384
  24
  25 MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
  26 {
  27         const uint8_t *buffer = xbuffer;
  28         int i, j;
  29         unsigned nbits, nbytes, nlimbs, nread = 0;
  30         mpi_limb_t a;
  31         MPI val = NULL;
  32
  33         if (*ret_nread < 2)
  34                 goto leave;
  35         nbits = buffer[0] << 8 | buffer[1];
  36
  37         if (nbits > MAX_EXTERN_MPI_BITS) {
  38                 pr_info("MPI: mpi too large (%u bits)\n", nbits);
  39                 goto leave;
  40         }
  41         buffer += 2;
  42         nread = 2;
  43
  44         nbytes = (nbits + 7) / 8;
  45         nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
  46         val = mpi_alloc(nlimbs);
  47         if (!val)
  48                 return NULL;
  49         i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
  50         i %= BYTES_PER_MPI_LIMB;
  51         val->nbits = nbits;
  52         j = val->nlimbs = nlimbs;
  53         val->sign = 0;
  54         for (; j > 0; j--) {
  55                 a = 0;
  56                 for (; i < BYTES_PER_MPI_LIMB; i++) {
  57                         if (++nread > *ret_nread) {
  58                                 printk
  59                                     ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
  60                                      nread, *ret_nread);
  61                                 goto leave;
  62                         }
  63                         a <<= 8;
  64                         a |= *buffer++;
  65                 }
  66                 i = 0;
  67                 val->d[j - 1] = a;
  68         }
  69
  70 leave:
  71         *ret_nread = nread;
  72         return val;
  73 }
  74 EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
  75
  76 /****************
  77  * Make an mpi from a character string.
  78  */
  79 int mpi_fromstr(MPI val, const char *str)
  80 {
  81         int hexmode = 0, sign = 0, prepend_zero = 0, i, j, c, c1, c2;
  82         unsigned nbits, nbytes, nlimbs;
  83         mpi_limb_t a;
  84
  85         if (*str == '-') {
  86                 sign = 1;
  87                 str++;
  88         }
  89         if (*str == '0' && str[1] == 'x')
  90                 hexmode = 1;
  91         else
  92                 return -EINVAL; /* other bases are not yet supported */
  93         str += 2;
  94
  95         nbits = strlen(str) * 4;
  96         if (nbits % 8)
  97                 prepend_zero = 1;
  98         nbytes = (nbits + 7) / 8;
  99         nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
 100         if (val->alloced < nlimbs)
 101                 if (!mpi_resize(val, nlimbs))
 102                         return -ENOMEM;
 103         i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
 104         i %= BYTES_PER_MPI_LIMB;
 105         j = val->nlimbs = nlimbs;
 106         val->sign = sign;
 107         for (; j > 0; j--) {
 108                 a = 0;
 109                 for (; i < BYTES_PER_MPI_LIMB; i++) {
 110                         if (prepend_zero) {
 111                                 c1 = '0';
 112                                 prepend_zero = 0;
 113                         } else
 114                                 c1 = *str++;
 115                         assert(c1);
 116                         c2 = *str++;
 117                         assert(c2);
 118                         if (c1 >= '0' && c1 <= '9')
 119                                 c = c1 - '0';
 120                         else if (c1 >= 'a' && c1 <= 'f')
 121                                 c = c1 - 'a' + 10;
 122                         else if (c1 >= 'A' && c1 <= 'F')
 123                                 c = c1 - 'A' + 10;
 124                         else {
 125                                 mpi_clear(val);
 126                                 return 1;
 127                         }
 128                         c <<= 4;
 129                         if (c2 >= '0' && c2 <= '9')
 130                                 c |= c2 - '0';
 131                         else if (c2 >= 'a' && c2 <= 'f')
 132                                 c |= c2 - 'a' + 10;
 133                         else if (c2 >= 'A' && c2 <= 'F')
 134                                 c |= c2 - 'A' + 10;
 135                         else {
 136                                 mpi_clear(val);
 137                                 return 1;
 138                         }
 139                         a <<= 8;
 140                         a |= c;
 141                 }
 142                 i = 0;
 143
 144                 val->d[j - 1] = a;
 145         }
 146
 147         return 0;
 148 }
 149 EXPORT_SYMBOL_GPL(mpi_fromstr);
 150
 151 /****************
 152  * Return an allocated buffer with the MPI (msb first).
 153  * NBYTES receives the length of this buffer. Caller must free the
 154  * return string (This function does return a 0 byte buffer with NBYTES
 155  * set to zero if the value of A is zero. If sign is not NULL, it will
 156  * be set to the sign of the A.
 157  */
 158 void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
 159 {
 160         uint8_t *p, *buffer;
 161         mpi_limb_t alimb;
 162         int i;
 163         unsigned int n;
 164
 165         if (sign)
 166                 *sign = a->sign;
 167         *nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;
 168         if (!n)
 169                 n++;            /* avoid zero length allocation */
 170         p = buffer = kmalloc(n, GFP_KERNEL);
 171         if (!p)
 172                 return NULL;
 173
 174         for (i = a->nlimbs - 1; i >= 0; i--) {
 175                 alimb = a->d[i];
 176 #if BYTES_PER_MPI_LIMB == 4
 177                 *p++ = alimb >> 24;
 178                 *p++ = alimb >> 16;
 179                 *p++ = alimb >> 8;
 180                 *p++ = alimb;
 181 #elif BYTES_PER_MPI_LIMB == 8
 182                 *p++ = alimb >> 56;
 183                 *p++ = alimb >> 48;
 184                 *p++ = alimb >> 40;
 185                 *p++ = alimb >> 32;
 186                 *p++ = alimb >> 24;
 187                 *p++ = alimb >> 16;
 188                 *p++ = alimb >> 8;
 189                 *p++ = alimb;
 190 #else
 191 #error please implement for this limb size.
 192 #endif
 193         }
 194
 195         /* this is sub-optimal but we need to do the shift operation
 196          * because the caller has to free the returned buffer */
 197         for (p = buffer; !*p && *nbytes; p++, --*nbytes)
 198                 ;
 199         if (p != buffer)
 200                 memmove(buffer, p, *nbytes);
 201
 202         return buffer;
 203 }
 204 EXPORT_SYMBOL_GPL(mpi_get_buffer);
 205
 206 /****************
 207  * Use BUFFER to update MPI.
 208  */
 209 int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
 210 {
 211         const uint8_t *buffer = xbuffer, *p;
 212         mpi_limb_t alimb;
 213         int nlimbs;
 214         int i;
 215
 216         nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
 217         if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
 218                 return -ENOMEM;
 219         a->sign = sign;
 220
 221         for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
 222 #if BYTES_PER_MPI_LIMB == 4
 223                 alimb = (mpi_limb_t) *p--;
 224                 alimb |= (mpi_limb_t) *p-- << 8;
 225                 alimb |= (mpi_limb_t) *p-- << 16;
 226                 alimb |= (mpi_limb_t) *p-- << 24;
 227 #elif BYTES_PER_MPI_LIMB == 8
 228                 alimb = (mpi_limb_t) *p--;
 229                 alimb |= (mpi_limb_t) *p-- << 8;
 230                 alimb |= (mpi_limb_t) *p-- << 16;
 231                 alimb |= (mpi_limb_t) *p-- << 24;
 232                 alimb |= (mpi_limb_t) *p-- << 32;
 233                 alimb |= (mpi_limb_t) *p-- << 40;
 234                 alimb |= (mpi_limb_t) *p-- << 48;
 235                 alimb |= (mpi_limb_t) *p-- << 56;
 236 #else
 237 #error please implement for this limb size.
 238 #endif
 239                 a->d[i++] = alimb;
 240         }
 241         if (p >= buffer) {
 242 #if BYTES_PER_MPI_LIMB == 4
 243                 alimb = *p--;
 244                 if (p >= buffer)
 245                         alimb |= (mpi_limb_t) *p-- << 8;
 246                 if (p >= buffer)
 247                         alimb |= (mpi_limb_t) *p-- << 16;
 248                 if (p >= buffer)
 249                         alimb |= (mpi_limb_t) *p-- << 24;
 250 #elif BYTES_PER_MPI_LIMB == 8
 251                 alimb = (mpi_limb_t) *p--;
 252                 if (p >= buffer)
 253                         alimb |= (mpi_limb_t) *p-- << 8;
 254                 if (p >= buffer)
 255                         alimb |= (mpi_limb_t) *p-- << 16;
 256                 if (p >= buffer)
 257                         alimb |= (mpi_limb_t) *p-- << 24;
 258                 if (p >= buffer)
 259                         alimb |= (mpi_limb_t) *p-- << 32;
 260                 if (p >= buffer)
 261                         alimb |= (mpi_limb_t) *p-- << 40;
 262                 if (p >= buffer)
 263                         alimb |= (mpi_limb_t) *p-- << 48;
 264                 if (p >= buffer)
 265                         alimb |= (mpi_limb_t) *p-- << 56;
 266 #else
 267 #error please implement for this limb size.
 268 #endif
 269                 a->d[i++] = alimb;
 270         }
 271         a->nlimbs = i;
 272
 273         if (i != nlimbs) {
 274                 pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
 275                        nlimbs);
 276                 BUG();
 277         }
 278         return 0;
 279 }
 280 EXPORT_SYMBOL_GPL(mpi_set_buffer);