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      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 (at) 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 #include <openssl/type_check.h>
     50 
     51 #include <assert.h>
     52 #include <string.h>
     53 
     54 #include "internal.h"
     55 
     56 
     57 /* NOTE: the IV/counter CTR mode is big-endian.  The code itself
     58  * is endian-neutral. */
     59 
     60 /* increment counter (128-bit int) by 1 */
     61 static void ctr128_inc(uint8_t *counter) {
     62   uint32_t n = 16;
     63   uint8_t c;
     64 
     65   do {
     66     --n;
     67     c = counter[n];
     68     ++c;
     69     counter[n] = c;
     70     if (c) {
     71       return;
     72     }
     73   } while (n);
     74 }
     75 
     76 OPENSSL_COMPILE_ASSERT((16 % sizeof(size_t)) == 0, bad_size_t_size);
     77 
     78 /* The input encrypted as though 128bit counter mode is being used.  The extra
     79  * state information to record how much of the 128bit block we have used is
     80  * contained in *num, and the encrypted counter is kept in ecount_buf.  Both
     81  * *num and ecount_buf must be initialised with zeros before the first call to
     82  * CRYPTO_ctr128_encrypt().
     83  *
     84  * This algorithm assumes that the counter is in the x lower bits of the IV
     85  * (ivec), and that the application has full control over overflow and the rest
     86  * of the IV.  This implementation takes NO responsibility for checking that
     87  * the counter doesn't overflow into the rest of the IV when incremented. */
     88 void CRYPTO_ctr128_encrypt(const uint8_t *in, uint8_t *out, size_t len,
     89                            const void *key, uint8_t ivec[16],
     90                            uint8_t ecount_buf[16], unsigned int *num,
     91                            block128_f block) {
     92   unsigned int n;
     93 
     94   assert(key && ecount_buf && num);
     95   assert(len == 0 || (in && out));
     96   assert(*num < 16);
     97 
     98   n = *num;
     99 
    100   while (n && len) {
    101     *(out++) = *(in++) ^ ecount_buf[n];
    102     --len;
    103     n = (n + 1) % 16;
    104   }
    105 
    106 #if STRICT_ALIGNMENT
    107   if (((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) != 0) {
    108     size_t l = 0;
    109     while (l < len) {
    110       if (n == 0) {
    111         (*block)(ivec, ecount_buf, key);
    112         ctr128_inc(ivec);
    113       }
    114       out[l] = in[l] ^ ecount_buf[n];
    115       ++l;
    116       n = (n + 1) % 16;
    117     }
    118 
    119     *num = n;
    120     return;
    121   }
    122 #endif
    123 
    124   while (len >= 16) {
    125     (*block)(ivec, ecount_buf, key);
    126     ctr128_inc(ivec);
    127     for (; n < 16; n += sizeof(size_t)) {
    128       *(size_t *)(out + n) = *(size_t *)(in + n) ^ *(size_t *)(ecount_buf + n);
    129     }
    130     len -= 16;
    131     out += 16;
    132     in += 16;
    133     n = 0;
    134   }
    135   if (len) {
    136     (*block)(ivec, ecount_buf, key);
    137     ctr128_inc(ivec);
    138     while (len--) {
    139       out[n] = in[n] ^ ecount_buf[n];
    140       ++n;
    141     }
    142   }
    143   *num = n;
    144 }
    145 
    146 /* increment upper 96 bits of 128-bit counter by 1 */
    147 static void ctr96_inc(uint8_t *counter) {
    148   uint32_t n = 12;
    149   uint8_t c;
    150 
    151   do {
    152     --n;
    153     c = counter[n];
    154     ++c;
    155     counter[n] = c;
    156     if (c) {
    157       return;
    158     }
    159   } while (n);
    160 }
    161 
    162 void CRYPTO_ctr128_encrypt_ctr32(const uint8_t *in, uint8_t *out,
    163                                  size_t len, const void *key,
    164                                  uint8_t ivec[16],
    165                                  uint8_t ecount_buf[16],
    166                                  unsigned int *num, ctr128_f func) {
    167   unsigned int n, ctr32;
    168 
    169   assert(key && ecount_buf && num);
    170   assert(len == 0 || (in && out));
    171   assert(*num < 16);
    172 
    173   n = *num;
    174 
    175   while (n && len) {
    176     *(out++) = *(in++) ^ ecount_buf[n];
    177     --len;
    178     n = (n + 1) % 16;
    179   }
    180 
    181   ctr32 = GETU32(ivec + 12);
    182   while (len >= 16) {
    183     size_t blocks = len / 16;
    184     /* 1<<28 is just a not-so-small yet not-so-large number...
    185      * Below condition is practically never met, but it has to
    186      * be checked for code correctness. */
    187     if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28)) {
    188       blocks = (1U << 28);
    189     }
    190     /* As (*func) operates on 32-bit counter, caller
    191      * has to handle overflow. 'if' below detects the
    192      * overflow, which is then handled by limiting the
    193      * amount of blocks to the exact overflow point... */
    194     ctr32 += (uint32_t)blocks;
    195     if (ctr32 < blocks) {
    196       blocks -= ctr32;
    197       ctr32 = 0;
    198     }
    199     (*func)(in, out, blocks, key, ivec);
    200     /* (*func) does not update ivec, caller does: */
    201     PUTU32(ivec + 12, ctr32);
    202     /* ... overflow was detected, propogate carry. */
    203     if (ctr32 == 0) {
    204       ctr96_inc(ivec);
    205     }
    206     blocks *= 16;
    207     len -= blocks;
    208     out += blocks;
    209     in += blocks;
    210   }
    211   if (len) {
    212     memset(ecount_buf, 0, 16);
    213     (*func)(ecount_buf, ecount_buf, 1, key, ivec);
    214     ++ctr32;
    215     PUTU32(ivec + 12, ctr32);
    216     if (ctr32 == 0) {
    217       ctr96_inc(ivec);
    218     }
    219     while (len--) {
    220       out[n] = in[n] ^ ecount_buf[n];
    221       ++n;
    222     }
    223   }
    224 
    225   *num = n;
    226 }
    227