lib/libcrypto/modes/ctr128.c

   1 /* $OpenBSD: ctr128.c,v 1.7 2017/08/13 17:46:24 bcook Exp $ */
   2 /* ====================================================================
   3  * Copyright (c) 2008 The OpenSSL Project.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  *
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  *
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in
  14  *    the documentation and/or other materials provided with the
  15  *    distribution.
  16  *
  17  * 3. All advertising materials mentioning features or use of this
  18  *    software must display the following acknowledgment:
  19  *    "This product includes software developed by the OpenSSL Project
  20  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
  21  *
  22  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  23  *    endorse or promote products derived from this software without
  24  *    prior written permission. For written permission, please contact
  25  *    openssl-core@openssl.org.
  26  *
  27  * 5. Products derived from this software may not be called "OpenSSL"
  28  *    nor may "OpenSSL" appear in their names without prior written
  29  *    permission of the OpenSSL Project.
  30  *
  31  * 6. Redistributions of any form whatsoever must retain the following
  32  *    acknowledgment:
  33  *    "This product includes software developed by the OpenSSL Project
  34  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
  35  *
  36  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  37  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  38  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  39  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  40  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  41  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  42  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  43  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  44  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  45  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  46  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  47  * OF THE POSSIBILITY OF SUCH DAMAGE.
  48  * ====================================================================
  49  *
  50  */
  51
  52 #include <openssl/crypto.h>
  53 #include "modes_lcl.h"
  54 #include <string.h>
  55
  56 #ifndef MODES_DEBUG
  57 # ifndef NDEBUG
  58 #  define NDEBUG
  59 # endif
  60 #endif
  61 #include <assert.h>
  62
  63 /* NOTE: the IV/counter CTR mode is big-endian.  The code itself
  64  * is endian-neutral. */
  65
  66 /* increment counter (128-bit int) by 1 */
  67 static void ctr128_inc(unsigned char *counter) {
  68         u32 n=16;
  69         u8  c;
  70
  71         do {
  72                 --n;
  73                 c = counter[n];
  74                 ++c;
  75                 counter[n] = c;
  76                 if (c) return;
  77         } while (n);
  78 }
  79
  80 #if !defined(OPENSSL_SMALL_FOOTPRINT)
  81 static void
  82 ctr128_inc_aligned(unsigned char *counter)
  83 {
  84 #if BYTE_ORDER == LITTLE_ENDIAN
  85         ctr128_inc(counter);
  86 #else
  87         size_t *data, c, n;
  88         data = (size_t *)counter;
  89         n = 16 / sizeof(size_t);
  90         do {
  91                 --n;
  92                 c = data[n];
  93                 ++c;
  94                 data[n] = c;
  95                 if (c)
  96                         return;
  97         } while (n);
  98 #endif
  99 }
 100 #endif
 101
 102 /* The input encrypted as though 128bit counter mode is being
 103  * used.  The extra state information to record how much of the
 104  * 128bit block we have used is contained in *num, and the
 105  * encrypted counter is kept in ecount_buf.  Both *num and
 106  * ecount_buf must be initialised with zeros before the first
 107  * call to CRYPTO_ctr128_encrypt().
 108  *
 109  * This algorithm assumes that the counter is in the x lower bits
 110  * of the IV (ivec), and that the application has full control over
 111  * overflow and the rest of the IV.  This implementation takes NO
 112  * responsability for checking that the counter doesn't overflow
 113  * into the rest of the IV when incremented.
 114  */
 115 void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out,
 116                         size_t len, const void *key,
 117                         unsigned char ivec[16], unsigned char ecount_buf[16],
 118                         unsigned int *num, block128_f block)
 119 {
 120         unsigned int n;
 121         size_t l=0;
 122
 123         assert(*num < 16);
 124
 125         n = *num;
 126
 127 #if !defined(OPENSSL_SMALL_FOOTPRINT)
 128         if (16%sizeof(size_t) == 0) do { /* always true actually */
 129                 while (n && len) {
 130                         *(out++) = *(in++) ^ ecount_buf[n];
 131                         --len;
 132                         n = (n+1) % 16;
 133                 }
 134
 135 #ifdef __STRICT_ALIGNMENT
 136                 if (((size_t)in|(size_t)out|(size_t)ivec)%sizeof(size_t) != 0)
 137                         break;
 138 #endif
 139                 while (len>=16) {
 140                         (*block)(ivec, ecount_buf, key);
 141                         ctr128_inc_aligned(ivec);
 142                         for (; n<16; n+=sizeof(size_t))
 143                                 *(size_t *)(out+n) =
 144                                 *(size_t *)(in+n) ^ *(size_t *)(ecount_buf+n);
 145                         len -= 16;
 146                         out += 16;
 147                         in  += 16;
 148                         n = 0;
 149                 }
 150                 if (len) {
 151                         (*block)(ivec, ecount_buf, key);
 152                         ctr128_inc_aligned(ivec);
 153                         while (len--) {
 154                                 out[n] = in[n] ^ ecount_buf[n];
 155                                 ++n;
 156                         }
 157                 }
 158                 *num = n;
 159                 return;
 160         } while(0);
 161         /* the rest would be commonly eliminated by x86* compiler */
 162 #endif
 163         while (l<len) {
 164                 if (n==0) {
 165                         (*block)(ivec, ecount_buf, key);
 166                         ctr128_inc(ivec);
 167                 }
 168                 out[l] = in[l] ^ ecount_buf[n];
 169                 ++l;
 170                 n = (n+1) % 16;
 171         }
 172
 173         *num=n;
 174 }
 175
 176 /* increment upper 96 bits of 128-bit counter by 1 */
 177 static void ctr96_inc(unsigned char *counter) {
 178         u32 n=12;
 179         u8  c;
 180
 181         do {
 182                 --n;
 183                 c = counter[n];
 184                 ++c;
 185                 counter[n] = c;
 186                 if (c) return;
 187         } while (n);
 188 }
 189
 190 void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out,
 191                         size_t len, const void *key,
 192                         unsigned char ivec[16], unsigned char ecount_buf[16],
 193                         unsigned int *num, ctr128_f func)
 194 {
 195         unsigned int n,ctr32;
 196
 197         assert(*num < 16);
 198
 199         n = *num;
 200
 201         while (n && len) {
 202                 *(out++) = *(in++) ^ ecount_buf[n];
 203                 --len;
 204                 n = (n+1) % 16;
 205         }
 206
 207         ctr32 = GETU32(ivec+12);
 208         while (len>=16) {
 209                 size_t blocks = len/16;
 210                 /*
 211                  * 1<<28 is just a not-so-small yet not-so-large number...
 212                  * Below condition is practically never met, but it has to
 213                  * be checked for code correctness.
 214                  */
 215                 if (sizeof(size_t)>sizeof(unsigned int) && blocks>(1U<<28))
 216                         blocks = (1U<<28);
 217                 /*
 218                  * As (*func) operates on 32-bit counter, caller
 219                  * has to handle overflow. 'if' below detects the
 220                  * overflow, which is then handled by limiting the
 221                  * amount of blocks to the exact overflow point...
 222                  */
 223                 ctr32 += (u32)blocks;
 224                 if (ctr32 < blocks) {
 225                         blocks -= ctr32;
 226                         ctr32   = 0;
 227                 }
 228                 (*func)(in,out,blocks,key,ivec);
 229                 /* (*ctr) does not update ivec, caller does: */
 230                 PUTU32(ivec+12,ctr32);
 231                 /* ... overflow was detected, propogate carry. */
 232                 if (ctr32 == 0) ctr96_inc(ivec);
 233                 blocks *= 16;
 234                 len -= blocks;
 235                 out += blocks;
 236                 in  += blocks;
 237         }
 238         if (len) {
 239                 memset(ecount_buf,0,16);
 240                 (*func)(ecount_buf,ecount_buf,1,key,ivec);
 241                 ++ctr32;
 242                 PUTU32(ivec+12,ctr32);
 243                 if (ctr32 == 0) ctr96_inc(ivec);
 244                 while (len--) {
 245                         out[n] = in[n] ^ ecount_buf[n];
 246                         ++n;
 247                 }
 248         }
 249
 250         *num=n;
 251 }