release/src/router/nettle/ctr.c

   1 /* ctr.c
   2  *
   3  * Cipher counter mode.
   4  */
   5
   6 /* nettle, low-level cryptographics library
   7  *
   8  * Copyright (C) 2005 Niels Möller
   9  *
  10  * The nettle library is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU Lesser General Public License as published by
  12  * the Free Software Foundation; either version 2.1 of the License, or (at your
  13  * option) any later version.
  14  *
  15  * The nettle library is distributed in the hope that it will be useful, but
  16  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  17  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
  18  * License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public License
  21  * along with the nettle library; see the file COPYING.LIB.  If not, write to
  22  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
  23  * MA 02111-1301, USA.
  24  */
  25
  26 #if HAVE_CONFIG_H
  27 # include "config.h"
  28 #endif
  29
  30 #include <assert.h>
  31 #include <stdlib.h>
  32 #include <string.h>
  33
  34 #include "ctr.h"
  35
  36 #include "macros.h"
  37 #include "memxor.h"
  38 #include "nettle-internal.h"
  39
  40 #define NBLOCKS 4
  41
  42 void
  43 ctr_crypt(void *ctx, nettle_crypt_func *f,
  44           unsigned block_size, uint8_t *ctr,
  45           unsigned length, uint8_t *dst,
  46           const uint8_t *src)
  47 {
  48   if (src != dst)
  49     {
  50       if (length == block_size)
  51         {
  52           f(ctx, block_size, dst, ctr);
  53           INCREMENT(block_size, ctr);
  54           memxor(dst, src, block_size);
  55         }
  56       else
  57         {
  58           unsigned left;
  59           uint8_t *p;
  60
  61           for (p = dst, left = length;
  62                left >= block_size;
  63                left -= block_size, p += block_size)
  64             {
  65               memcpy (p, ctr, block_size);
  66               INCREMENT(block_size, ctr);
  67             }
  68
  69           f(ctx, length - left, dst, dst);
  70           memxor(dst, src, length - left);
  71
  72           if (left)
  73             {
  74               TMP_DECL(buffer, uint8_t, NETTLE_MAX_CIPHER_BLOCK_SIZE);
  75               TMP_ALLOC(buffer, block_size);
  76
  77               f(ctx, block_size, buffer, ctr);
  78               INCREMENT(block_size, ctr);
  79               memxor3(dst + length - left, src + length - left, buffer, left);
  80             }
  81         }
  82     }
  83   else
  84     {
  85       if (length > block_size)
  86         {
  87           TMP_DECL(buffer, uint8_t, NBLOCKS * NETTLE_MAX_CIPHER_BLOCK_SIZE);
  88           unsigned chunk = NBLOCKS * block_size;
  89
  90           TMP_ALLOC(buffer, chunk);
  91
  92           for (; length >= chunk;
  93                length -= chunk, src += chunk, dst += chunk)
  94             {
  95               unsigned n;
  96               uint8_t *p;
  97               for (n = 0, p = buffer; n < NBLOCKS; n++, p += block_size)
  98                 {
  99                   memcpy (p, ctr, block_size);
 100                   INCREMENT(block_size, ctr);
 101                 }
 102               f(ctx, chunk, buffer, buffer);
 103               memxor(dst, buffer, chunk);
 104             }
 105
 106           if (length > 0)
 107             {
 108               /* Final, possibly partial, blocks */
 109               for (chunk = 0; chunk < length; chunk += block_size)
 110                 {
 111                   memcpy (buffer + chunk, ctr, block_size);
 112                   INCREMENT(block_size, ctr);
 113                 }
 114               f(ctx, chunk, buffer, buffer);
 115               memxor3(dst, src, buffer, length);
 116             }
 117         }
 118       else if (length > 0)
 119         {
 120           TMP_DECL(buffer, uint8_t, NETTLE_MAX_CIPHER_BLOCK_SIZE);
 121           TMP_ALLOC(buffer, block_size);
 122
 123           f(ctx, block_size, buffer, ctr);
 124           INCREMENT(block_size, ctr);
 125           memxor3(dst, src, buffer, length);
 126         }
 127     }
 128 }