crypto/aes/aes_ctr.c

   1 /* crypto/aes/aes_ctr.c -*- mode:C; c-file-style: "eay" -*- */
   2 /* ====================================================================
   3  * Copyright (c) 1998-2002 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 #ifndef AES_DEBUG
  53 # ifndef NDEBUG
  54 #  define NDEBUG
  55 # endif
  56 #endif
  57 #include <assert.h>
  58
  59 #include <openssl/aes.h>
  60 #include "aes_locl.h"
  61
  62 /* NOTE: CTR mode is big-endian.  The rest of the AES code
  63  * is endian-neutral. */
  64
  65 /* increment counter (128-bit int) by 1 */
  66 static void AES_ctr128_inc(unsigned char *counter) {
  67         unsigned long c;
  68
  69         /* Grab bottom dword of counter and increment */
  70 #ifdef L_ENDIAN
  71         c = GETU32(counter +  0);
  72         c++;
  73         PUTU32(counter +  0, c);
  74 #else
  75         c = GETU32(counter + 12);
  76         c++;
  77         PUTU32(counter + 12, c);
  78 #endif
  79
  80         /* if no overflow, we're done */
  81         if (c)
  82                 return;
  83
  84         /* Grab 1st dword of counter and increment */
  85 #ifdef L_ENDIAN
  86         c = GETU32(counter +  4);
  87         c++;
  88         PUTU32(counter +  4, c);
  89 #else
  90         c = GETU32(counter +  8);
  91         c++;
  92         PUTU32(counter +  8, c);
  93 #endif
  94
  95         /* if no overflow, we're done */
  96         if (c)
  97                 return;
  98
  99         /* Grab 2nd dword of counter and increment */
 100 #ifdef L_ENDIAN
 101         c = GETU32(counter +  8);
 102         c++;
 103         PUTU32(counter +  8, c);
 104 #else
 105         c = GETU32(counter +  4);
 106         c++;
 107         PUTU32(counter +  4, c);
 108 #endif
 109
 110         /* if no overflow, we're done */
 111         if (c)
 112                 return;
 113
 114         /* Grab top dword of counter and increment */
 115 #ifdef L_ENDIAN
 116         c = GETU32(counter + 12);
 117         c++;
 118         PUTU32(counter + 12, c);
 119 #else
 120         c = GETU32(counter +  0);
 121         c++;
 122         PUTU32(counter +  0, c);
 123 #endif
 124
 125 }
 126
 127 /* The input encrypted as though 128bit counter mode is being
 128  * used.  The extra state information to record how much of the
 129  * 128bit block we have used is contained in *num, and the
 130  * encrypted counter is kept in ecount_buf.  Both *num and
 131  * ecount_buf must be initialised with zeros before the first
 132  * call to AES_ctr128_encrypt().
 133  *
 134  * This algorithm assumes that the counter is in the x lower bits
 135  * of the IV (ivec), and that the application has full control over
 136  * overflow and the rest of the IV.  This implementation takes NO
 137  * responsability for checking that the counter doesn't overflow
 138  * into the rest of the IV when incremented.
 139  */
 140 void AES_ctr128_encrypt(const unsigned char *in, unsigned char *out,
 141         const unsigned long length, const AES_KEY *key,
 142         unsigned char ivec[AES_BLOCK_SIZE],
 143         unsigned char ecount_buf[AES_BLOCK_SIZE],
 144         unsigned int *num) {
 145
 146         unsigned int n;
 147         unsigned long l=length;
 148
 149         assert(in && out && key && counter && num);
 150         assert(*num < AES_BLOCK_SIZE);
 151
 152         n = *num;
 153
 154         while (l--) {
 155                 if (n == 0) {
 156                         AES_encrypt(counter, ecount_buf, key);
 157                         AES_ctr128_inc(counter);
 158                 }
 159                 *(out++) = *(in++) ^ ecount_buf[n];
 160                 n = (n+1) % AES_BLOCK_SIZE;
 161         }
 162
 163         *num=n;
 164 }