crypto/modes/cts128.c

   1 /*
   2  * Copyright 2008-2016 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (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 <string.h>
  11 #include <openssl/crypto.h>
  12 #include "internal/modes_int.h"
  13
  14 /*
  15  * Trouble with Ciphertext Stealing, CTS, mode is that there is no
  16  * common official specification, but couple of cipher/application
  17  * specific ones: RFC2040 and RFC3962. Then there is 'Proposal to
  18  * Extend CBC Mode By "Ciphertext Stealing"' at NIST site, which
  19  * deviates from mentioned RFCs. Most notably it allows input to be
  20  * of block length and it doesn't flip the order of the last two
  21  * blocks. CTS is being discussed even in ECB context, but it's not
  22  * adopted for any known application. This implementation provides
  23  * two interfaces: one compliant with above mentioned RFCs and one
  24  * compliant with the NIST proposal, both extending CBC mode.
  25  */
  26
  27 size_t CRYPTO_cts128_encrypt_block(const unsigned char *in,
  28                                    unsigned char *out, size_t len,
  29                                    const void *key, unsigned char ivec[16],
  30                                    block128_f block)
  31 {
  32     size_t residue, n;
  33
  34     if (len <= 16)
  35         return 0;
  36
  37     if ((residue = len % 16) == 0)
  38         residue = 16;
  39
  40     len -= residue;
  41
  42     CRYPTO_cbc128_encrypt(in, out, len, key, ivec, block);
  43
  44     in += len;
  45     out += len;
  46
  47     for (n = 0; n < residue; ++n)
  48         ivec[n] ^= in[n];
  49     (*block) (ivec, ivec, key);
  50     memcpy(out, out - 16, residue);
  51     memcpy(out - 16, ivec, 16);
  52
  53     return len + residue;
  54 }
  55
  56 size_t CRYPTO_nistcts128_encrypt_block(const unsigned char *in,
  57                                        unsigned char *out, size_t len,
  58                                        const void *key,
  59                                        unsigned char ivec[16],
  60                                        block128_f block)
  61 {
  62     size_t residue, n;
  63
  64     if (len < 16)
  65         return 0;
  66
  67     residue = len % 16;
  68
  69     len -= residue;
  70
  71     CRYPTO_cbc128_encrypt(in, out, len, key, ivec, block);
  72
  73     if (residue == 0)
  74         return len;
  75
  76     in += len;
  77     out += len;
  78
  79     for (n = 0; n < residue; ++n)
  80         ivec[n] ^= in[n];
  81     (*block) (ivec, ivec, key);
  82     memcpy(out - 16 + residue, ivec, 16);
  83
  84     return len + residue;
  85 }
  86
  87 size_t CRYPTO_cts128_encrypt(const unsigned char *in, unsigned char *out,
  88                              size_t len, const void *key,
  89                              unsigned char ivec[16], cbc128_f cbc)
  90 {
  91     size_t residue;
  92     union {
  93         size_t align;
  94         unsigned char c[16];
  95     } tmp;
  96
  97     if (len <= 16)
  98         return 0;
  99
 100     if ((residue = len % 16) == 0)
 101         residue = 16;
 102
 103     len -= residue;
 104
 105     (*cbc) (in, out, len, key, ivec, 1);
 106
 107     in += len;
 108     out += len;
 109
 110 #if defined(CBC_HANDLES_TRUNCATED_IO)
 111     memcpy(tmp.c, out - 16, 16);
 112     (*cbc) (in, out - 16, residue, key, ivec, 1);
 113     memcpy(out, tmp.c, residue);
 114 #else
 115     memset(tmp.c, 0, sizeof(tmp));
 116     memcpy(tmp.c, in, residue);
 117     memcpy(out, out - 16, residue);
 118     (*cbc) (tmp.c, out - 16, 16, key, ivec, 1);
 119 #endif
 120     return len + residue;
 121 }
 122
 123 size_t CRYPTO_nistcts128_encrypt(const unsigned char *in, unsigned char *out,
 124                                  size_t len, const void *key,
 125                                  unsigned char ivec[16], cbc128_f cbc)
 126 {
 127     size_t residue;
 128     union {
 129         size_t align;
 130         unsigned char c[16];
 131     } tmp;
 132
 133     if (len < 16)
 134         return 0;
 135
 136     residue = len % 16;
 137
 138     len -= residue;
 139
 140     (*cbc) (in, out, len, key, ivec, 1);
 141
 142     if (residue == 0)
 143         return len;
 144
 145     in += len;
 146     out += len;
 147
 148 #if defined(CBC_HANDLES_TRUNCATED_IO)
 149     (*cbc) (in, out - 16 + residue, residue, key, ivec, 1);
 150 #else
 151     memset(tmp.c, 0, sizeof(tmp));
 152     memcpy(tmp.c, in, residue);
 153     (*cbc) (tmp.c, out - 16 + residue, 16, key, ivec, 1);
 154 #endif
 155     return len + residue;
 156 }
 157
 158 size_t CRYPTO_cts128_decrypt_block(const unsigned char *in,
 159                                    unsigned char *out, size_t len,
 160                                    const void *key, unsigned char ivec[16],
 161                                    block128_f block)
 162 {
 163     size_t residue, n;
 164     union {
 165         size_t align;
 166         unsigned char c[32];
 167     } tmp;
 168
 169     if (len <= 16)
 170         return 0;
 171
 172     if ((residue = len % 16) == 0)
 173         residue = 16;
 174
 175     len -= 16 + residue;
 176
 177     if (len) {
 178         CRYPTO_cbc128_decrypt(in, out, len, key, ivec, block);
 179         in += len;
 180         out += len;
 181     }
 182
 183     (*block) (in, tmp.c + 16, key);
 184
 185     memcpy(tmp.c, tmp.c + 16, 16);
 186     memcpy(tmp.c, in + 16, residue);
 187     (*block) (tmp.c, tmp.c, key);
 188
 189     for (n = 0; n < 16; ++n) {
 190         unsigned char c = in[n];
 191         out[n] = tmp.c[n] ^ ivec[n];
 192         ivec[n] = c;
 193     }
 194     for (residue += 16; n < residue; ++n)
 195         out[n] = tmp.c[n] ^ in[n];
 196
 197     return 16 + len + residue;
 198 }
 199
 200 size_t CRYPTO_nistcts128_decrypt_block(const unsigned char *in,
 201                                        unsigned char *out, size_t len,
 202                                        const void *key,
 203                                        unsigned char ivec[16],
 204                                        block128_f block)
 205 {
 206     size_t residue, n;
 207     union {
 208         size_t align;
 209         unsigned char c[32];
 210     } tmp;
 211
 212     if (len < 16)
 213         return 0;
 214
 215     residue = len % 16;
 216
 217     if (residue == 0) {
 218         CRYPTO_cbc128_decrypt(in, out, len, key, ivec, block);
 219         return len;
 220     }
 221
 222     len -= 16 + residue;
 223
 224     if (len) {
 225         CRYPTO_cbc128_decrypt(in, out, len, key, ivec, block);
 226         in += len;
 227         out += len;
 228     }
 229
 230     (*block) (in + residue, tmp.c + 16, key);
 231
 232     memcpy(tmp.c, tmp.c + 16, 16);
 233     memcpy(tmp.c, in, residue);
 234     (*block) (tmp.c, tmp.c, key);
 235
 236     for (n = 0; n < 16; ++n) {
 237         unsigned char c = in[n];
 238         out[n] = tmp.c[n] ^ ivec[n];
 239         ivec[n] = in[n + residue];
 240         tmp.c[n] = c;
 241     }
 242     for (residue += 16; n < residue; ++n)
 243         out[n] = tmp.c[n] ^ tmp.c[n - 16];
 244
 245     return 16 + len + residue;
 246 }
 247
 248 size_t CRYPTO_cts128_decrypt(const unsigned char *in, unsigned char *out,
 249                              size_t len, const void *key,
 250                              unsigned char ivec[16], cbc128_f cbc)
 251 {
 252     size_t residue;
 253     union {
 254         size_t align;
 255         unsigned char c[32];
 256     } tmp;
 257
 258     if (len <= 16)
 259         return 0;
 260
 261     if ((residue = len % 16) == 0)
 262         residue = 16;
 263
 264     len -= 16 + residue;
 265
 266     if (len) {
 267         (*cbc) (in, out, len, key, ivec, 0);
 268         in += len;
 269         out += len;
 270     }
 271
 272     memset(tmp.c, 0, sizeof(tmp));
 273     /*
 274      * this places in[16] at &tmp.c[16] and decrypted block at &tmp.c[0]
 275      */
 276     (*cbc) (in, tmp.c, 16, key, tmp.c + 16, 0);
 277
 278     memcpy(tmp.c, in + 16, residue);
 279 #if defined(CBC_HANDLES_TRUNCATED_IO)
 280     (*cbc) (tmp.c, out, 16 + residue, key, ivec, 0);
 281 #else
 282     (*cbc) (tmp.c, tmp.c, 32, key, ivec, 0);
 283     memcpy(out, tmp.c, 16 + residue);
 284 #endif
 285     return 16 + len + residue;
 286 }
 287
 288 size_t CRYPTO_nistcts128_decrypt(const unsigned char *in, unsigned char *out,
 289                                  size_t len, const void *key,
 290                                  unsigned char ivec[16], cbc128_f cbc)
 291 {
 292     size_t residue;
 293     union {
 294         size_t align;
 295         unsigned char c[32];
 296     } tmp;
 297
 298     if (len < 16)
 299         return 0;
 300
 301     residue = len % 16;
 302
 303     if (residue == 0) {
 304         (*cbc) (in, out, len, key, ivec, 0);
 305         return len;
 306     }
 307
 308     len -= 16 + residue;
 309
 310     if (len) {
 311         (*cbc) (in, out, len, key, ivec, 0);
 312         in += len;
 313         out += len;
 314     }
 315
 316     memset(tmp.c, 0, sizeof(tmp));
 317     /*
 318      * this places in[16] at &tmp.c[16] and decrypted block at &tmp.c[0]
 319      */
 320     (*cbc) (in + residue, tmp.c, 16, key, tmp.c + 16, 0);
 321
 322     memcpy(tmp.c, in, residue);
 323 #if defined(CBC_HANDLES_TRUNCATED_IO)
 324     (*cbc) (tmp.c, out, 16 + residue, key, ivec, 0);
 325 #else
 326     (*cbc) (tmp.c, tmp.c, 32, key, ivec, 0);
 327     memcpy(out, tmp.c, 16 + residue);
 328 #endif
 329     return 16 + len + residue;
 330 }