crypto/openssl/crypto/modes/ctr128.c

   1 /* ====================================================================
   2  * Copyright (c) 2008 The OpenSSL Project.  All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  *
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  *
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in
  13  *    the documentation and/or other materials provided with the
  14  *    distribution.
  15  *
  16  * 3. All advertising materials mentioning features or use of this
  17  *    software must display the following acknowledgment:
  18  *    "This product includes software developed by the OpenSSL Project
  19  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
  20  *
  21  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  22  *    endorse or promote products derived from this software without
  23  *    prior written permission. For written permission, please contact
  24  *    openssl-core@openssl.org.
  25  *
  26  * 5. Products derived from this software may not be called "OpenSSL"
  27  *    nor may "OpenSSL" appear in their names without prior written
  28  *    permission of the OpenSSL Project.
  29  *
  30  * 6. Redistributions of any form whatsoever must retain the following
  31  *    acknowledgment:
  32  *    "This product includes software developed by the OpenSSL Project
  33  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
  34  *
  35  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  36  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  37  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  38  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  39  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  40  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  41  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  42  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  43  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  44  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  45  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  46  * OF THE POSSIBILITY OF SUCH DAMAGE.
  47  * ====================================================================
  48  *
  49  */
  50
  51 #include <openssl/crypto.h>
  52 #include "modes_lcl.h"
  53 #include <string.h>
  54
  55 #ifndef MODES_DEBUG
  56 # ifndef NDEBUG
  57 #  define NDEBUG
  58 # endif
  59 #endif
  60 #include <assert.h>
  61
  62 /*
  63  * NOTE: the IV/counter CTR mode is big-endian.  The code itself is
  64  * endian-neutral.
  65  */
  66
  67 /* increment counter (128-bit int) by 1 */
  68 static void ctr128_inc(unsigned char *counter)
  69 {
  70     u32 n = 16, c = 1;
  71
  72     do {
  73         --n;
  74         c += counter[n];
  75         counter[n] = (u8)c;
  76         c >>= 8;
  77     } while (n);
  78 }
  79
  80 #if !defined(OPENSSL_SMALL_FOOTPRINT)
  81 static void ctr128_inc_aligned(unsigned char *counter)
  82 {
  83     size_t *data, c, d, n;
  84     const union {
  85         long one;
  86         char little;
  87     } is_endian = {
  88         1
  89     };
  90
  91     if (is_endian.little || ((size_t)counter % sizeof(size_t)) != 0) {
  92         ctr128_inc(counter);
  93         return;
  94     }
  95
  96     data = (size_t *)counter;
  97     c = 1;
  98     n = 16 / sizeof(size_t);
  99     do {
 100         --n;
 101         d = data[n] += c;
 102         /* did addition carry? */
 103         c = ((d - c) ^ d) >> (sizeof(size_t) * 8 - 1);
 104     } while (n);
 105 }
 106 #endif
 107
 108 /*
 109  * The input encrypted as though 128bit counter mode is being used.  The
 110  * extra state information to record how much of the 128bit block we have
 111  * used is contained in *num, and the encrypted counter is kept in
 112  * ecount_buf.  Both *num and ecount_buf must be initialised with zeros
 113  * before the first call to CRYPTO_ctr128_encrypt(). This algorithm assumes
 114  * that the counter is in the x lower bits of the IV (ivec), and that the
 115  * application has full control over overflow and the rest of the IV.  This
 116  * implementation takes NO responsability for checking that the counter
 117  * doesn't overflow into the rest of the IV when incremented.
 118  */
 119 void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out,
 120                            size_t len, const void *key,
 121                            unsigned char ivec[16],
 122                            unsigned char ecount_buf[16], unsigned int *num,
 123                            block128_f block)
 124 {
 125     unsigned int n;
 126     size_t l = 0;
 127
 128     assert(in && out && key && ecount_buf && num);
 129     assert(*num < 16);
 130
 131     n = *num;
 132
 133 #if !defined(OPENSSL_SMALL_FOOTPRINT)
 134     if (16 % sizeof(size_t) == 0) { /* always true actually */
 135         do {
 136             while (n && len) {
 137                 *(out++) = *(in++) ^ ecount_buf[n];
 138                 --len;
 139                 n = (n + 1) % 16;
 140             }
 141
 142 # if defined(STRICT_ALIGNMENT)
 143             if (((size_t)in | (size_t)out | (size_t)ecount_buf)
 144                 % sizeof(size_t) != 0)
 145                 break;
 146 # endif
 147             while (len >= 16) {
 148                 (*block) (ivec, ecount_buf, key);
 149                 ctr128_inc_aligned(ivec);
 150                 for (n = 0; n < 16; n += sizeof(size_t))
 151                     *(size_t *)(out + n) =
 152                         *(size_t *)(in + n) ^ *(size_t *)(ecount_buf + n);
 153                 len -= 16;
 154                 out += 16;
 155                 in += 16;
 156                 n = 0;
 157             }
 158             if (len) {
 159                 (*block) (ivec, ecount_buf, key);
 160                 ctr128_inc_aligned(ivec);
 161                 while (len--) {
 162                     out[n] = in[n] ^ ecount_buf[n];
 163                     ++n;
 164                 }
 165             }
 166             *num = n;
 167             return;
 168         } while (0);
 169     }
 170     /* the rest would be commonly eliminated by x86* compiler */
 171 #endif
 172     while (l < len) {
 173         if (n == 0) {
 174             (*block) (ivec, ecount_buf, key);
 175             ctr128_inc(ivec);
 176         }
 177         out[l] = in[l] ^ ecount_buf[n];
 178         ++l;
 179         n = (n + 1) % 16;
 180     }
 181
 182     *num = n;
 183 }
 184
 185 /* increment upper 96 bits of 128-bit counter by 1 */
 186 static void ctr96_inc(unsigned char *counter)
 187 {
 188     u32 n = 12, c = 1;
 189
 190     do {
 191         --n;
 192         c += counter[n];
 193         counter[n] = (u8)c;
 194         c >>= 8;
 195     } while (n);
 196 }
 197
 198 void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out,
 199                                  size_t len, const void *key,
 200                                  unsigned char ivec[16],
 201                                  unsigned char ecount_buf[16],
 202                                  unsigned int *num, ctr128_f func)
 203 {
 204     unsigned int n, ctr32;
 205
 206     assert(in && out && key && ecount_buf && num);
 207     assert(*num < 16);
 208
 209     n = *num;
 210
 211     while (n && len) {
 212         *(out++) = *(in++) ^ ecount_buf[n];
 213         --len;
 214         n = (n + 1) % 16;
 215     }
 216
 217     ctr32 = GETU32(ivec + 12);
 218     while (len >= 16) {
 219         size_t blocks = len / 16;
 220         /*
 221          * 1<<28 is just a not-so-small yet not-so-large number...
 222          * Below condition is practically never met, but it has to
 223          * be checked for code correctness.
 224          */
 225         if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28))
 226             blocks = (1U << 28);
 227         /*
 228          * As (*func) operates on 32-bit counter, caller
 229          * has to handle overflow. 'if' below detects the
 230          * overflow, which is then handled by limiting the
 231          * amount of blocks to the exact overflow point...
 232          */
 233         ctr32 += (u32)blocks;
 234         if (ctr32 < blocks) {
 235             blocks -= ctr32;
 236             ctr32 = 0;
 237         }
 238         (*func) (in, out, blocks, key, ivec);
 239         /* (*ctr) does not update ivec, caller does: */
 240         PUTU32(ivec + 12, ctr32);
 241         /* ... overflow was detected, propogate carry. */
 242         if (ctr32 == 0)
 243             ctr96_inc(ivec);
 244         blocks *= 16;
 245         len -= blocks;
 246         out += blocks;
 247         in += blocks;
 248     }
 249     if (len) {
 250         memset(ecount_buf, 0, 16);
 251         (*func) (ecount_buf, ecount_buf, 1, key, ivec);
 252         ++ctr32;
 253         PUTU32(ivec + 12, ctr32);
 254         if (ctr32 == 0)
 255             ctr96_inc(ivec);
 256         while (len--) {
 257             out[n] = in[n] ^ ecount_buf[n];
 258             ++n;
 259         }
 260     }
 261
 262     *num = n;
 263 }