crypto/modes/cfb128.c

   1 /*
   2  * Copyright 2008-2016 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the OpenSSL license (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 #include <openssl/crypto.h>
  11 #include "modes_lcl.h"
  12 #include <string.h>
  13
  14 /*
  15  * The input and output encrypted as though 128bit cfb mode is being used.
  16  * The extra state information to record how much of the 128bit block we have
  17  * used is contained in *num;
  18  */
  19 void CRYPTO_cfb128_encrypt(const unsigned char *in, unsigned char *out,
  20                            size_t len, const void *key,
  21                            unsigned char ivec[16], int *num,
  22                            int enc, block128_f block)
  23 {
  24     unsigned int n;
  25     size_t l = 0;
  26
  27     n = *num;
  28
  29     if (enc) {
  30 #if !defined(OPENSSL_SMALL_FOOTPRINT)
  31         if (16 % sizeof(size_t) == 0) { /* always true actually */
  32             do {
  33                 while (n && len) {
  34                     *(out++) = ivec[n] ^= *(in++);
  35                     --len;
  36                     n = (n + 1) % 16;
  37                 }
  38 # if defined(STRICT_ALIGNMENT)
  39                 if (((size_t)in | (size_t)out | (size_t)ivec) %
  40                     sizeof(size_t) != 0)
  41                     break;
  42 # endif
  43                 while (len >= 16) {
  44                     (*block) (ivec, ivec, key);
  45                     for (; n < 16; n += sizeof(size_t)) {
  46                         *(size_t *)(out + n) =
  47                             *(size_t *)(ivec + n) ^= *(size_t *)(in + n);
  48                     }
  49                     len -= 16;
  50                     out += 16;
  51                     in += 16;
  52                     n = 0;
  53                 }
  54                 if (len) {
  55                     (*block) (ivec, ivec, key);
  56                     while (len--) {
  57                         out[n] = ivec[n] ^= in[n];
  58                         ++n;
  59                     }
  60                 }
  61                 *num = n;
  62                 return;
  63             } while (0);
  64         }
  65         /* the rest would be commonly eliminated by x86* compiler */
  66 #endif
  67         while (l < len) {
  68             if (n == 0) {
  69                 (*block) (ivec, ivec, key);
  70             }
  71             out[l] = ivec[n] ^= in[l];
  72             ++l;
  73             n = (n + 1) % 16;
  74         }
  75         *num = n;
  76     } else {
  77 #if !defined(OPENSSL_SMALL_FOOTPRINT)
  78         if (16 % sizeof(size_t) == 0) { /* always true actually */
  79             do {
  80                 while (n && len) {
  81                     unsigned char c;
  82                     *(out++) = ivec[n] ^ (c = *(in++));
  83                     ivec[n] = c;
  84                     --len;
  85                     n = (n + 1) % 16;
  86                 }
  87 # if defined(STRICT_ALIGNMENT)
  88                 if (((size_t)in | (size_t)out | (size_t)ivec) %
  89                     sizeof(size_t) != 0)
  90                     break;
  91 # endif
  92                 while (len >= 16) {
  93                     (*block) (ivec, ivec, key);
  94                     for (; n < 16; n += sizeof(size_t)) {
  95                         size_t t = *(size_t *)(in + n);
  96                         *(size_t *)(out + n) = *(size_t *)(ivec + n) ^ t;
  97                         *(size_t *)(ivec + n) = t;
  98                     }
  99                     len -= 16;
 100                     out += 16;
 101                     in += 16;
 102                     n = 0;
 103                 }
 104                 if (len) {
 105                     (*block) (ivec, ivec, key);
 106                     while (len--) {
 107                         unsigned char c;
 108                         out[n] = ivec[n] ^ (c = in[n]);
 109                         ivec[n] = c;
 110                         ++n;
 111                     }
 112                 }
 113                 *num = n;
 114                 return;
 115             } while (0);
 116         }
 117         /* the rest would be commonly eliminated by x86* compiler */
 118 #endif
 119         while (l < len) {
 120             unsigned char c;
 121             if (n == 0) {
 122                 (*block) (ivec, ivec, key);
 123             }
 124             out[l] = ivec[n] ^ (c = in[l]);
 125             ivec[n] = c;
 126             ++l;
 127             n = (n + 1) % 16;
 128         }
 129         *num = n;
 130     }
 131 }
 132
 133 /*
 134  * This expects a single block of size nbits for both in and out. Note that
 135  * it corrupts any extra bits in the last byte of out
 136  */
 137 static void cfbr_encrypt_block(const unsigned char *in, unsigned char *out,
 138                                int nbits, const void *key,
 139                                unsigned char ivec[16], int enc,
 140                                block128_f block)
 141 {
 142     int n, rem, num;
 143     unsigned char ovec[16 * 2 + 1]; /* +1 because we dereference (but don't
 144                                      * use) one byte off the end */
 145
 146     if (nbits <= 0 || nbits > 128)
 147         return;
 148
 149     /* fill in the first half of the new IV with the current IV */
 150     memcpy(ovec, ivec, 16);
 151     /* construct the new IV */
 152     (*block) (ivec, ivec, key);
 153     num = (nbits + 7) / 8;
 154     if (enc)                    /* encrypt the input */
 155         for (n = 0; n < num; ++n)
 156             out[n] = (ovec[16 + n] = in[n] ^ ivec[n]);
 157     else                        /* decrypt the input */
 158         for (n = 0; n < num; ++n)
 159             out[n] = (ovec[16 + n] = in[n]) ^ ivec[n];
 160     /* shift ovec left... */
 161     rem = nbits % 8;
 162     num = nbits / 8;
 163     if (rem == 0)
 164         memcpy(ivec, ovec + num, 16);
 165     else
 166         for (n = 0; n < 16; ++n)
 167             ivec[n] = ovec[n + num] << rem | ovec[n + num + 1] >> (8 - rem);
 168
 169     /* it is not necessary to cleanse ovec, since the IV is not secret */
 170 }
 171
 172 /* N.B. This expects the input to be packed, MS bit first */
 173 void CRYPTO_cfb128_1_encrypt(const unsigned char *in, unsigned char *out,
 174                              size_t bits, const void *key,
 175                              unsigned char ivec[16], int *num,
 176                              int enc, block128_f block)
 177 {
 178     size_t n;
 179     unsigned char c[1], d[1];
 180
 181     for (n = 0; n < bits; ++n) {
 182         c[0] = (in[n / 8] & (1 << (7 - n % 8))) ? 0x80 : 0;
 183         cfbr_encrypt_block(c, d, 1, key, ivec, enc, block);
 184         out[n / 8] = (out[n / 8] & ~(1 << (unsigned int)(7 - n % 8))) |
 185             ((d[0] & 0x80) >> (unsigned int)(n % 8));
 186     }
 187 }
 188
 189 void CRYPTO_cfb128_8_encrypt(const unsigned char *in, unsigned char *out,
 190                              size_t length, const void *key,
 191                              unsigned char ivec[16], int *num,
 192                              int enc, block128_f block)
 193 {
 194     size_t n;
 195
 196     for (n = 0; n < length; ++n)
 197         cfbr_encrypt_block(&in[n], &out[n], 8, key, ivec, enc, block);
 198 }