crypto/modes/cfb.c

/* ====================================================================
 * Copyright (c) 2008 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    openssl-core@openssl.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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 * ==================================================================== */

#include <openssl/type_check.h>

#include <assert.h>
#include <string.h>

#include "internal.h"


OPENSSL_COMPILE_ASSERT((16 % sizeof(size_t)) == 0, bad_size_t_size);

void CRYPTO_cfb128_encrypt(const uint8_t *in, uint8_t *out, size_t len,
                           const void *key, uint8_t ivec[16], int *num, int enc,
                           block128_f block) {
  unsigned int n;
  size_t l = 0;

  assert(in && out && key && ivec && num);

  n = *num;

  if (enc) {
    while (n && len) {
      *(out++) = ivec[n] ^= *(in++);
      --len;
      n = (n + 1) % 16;
    }
#if STRICT_ALIGNMENT
    if (((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) != 0) {
      while (l < len) {
        if (n == 0) {
          (*block)(ivec, ivec, key);
        }
        out[l] = ivec[n] ^= in[l];
        ++l;
        n = (n + 1) % 16;
      }
      *num = n;
      return;
    }
#endif
    while (len >= 16) {
      (*block)(ivec, ivec, key);
      for (; n < 16; n += sizeof(size_t)) {
        *(size_t *)(out + n) = *(size_t *)(ivec + n) ^= *(size_t *)(in + n);
      }
      len -= 16;
      out += 16;
      in += 16;
      n = 0;
    }
    if (len) {
      (*block)(ivec, ivec, key);
      while (len--) {
        out[n] = ivec[n] ^= in[n];
        ++n;
      }
    }
    *num = n;
    return;
  } else {
    while (n && len) {
      uint8_t c;
      *(out++) = ivec[n] ^ (c = *(in++));
      ivec[n] = c;
      --len;
      n = (n + 1) % 16;
    }
    if (STRICT_ALIGNMENT && ((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) != 0) {
      while (l < len) {
        unsigned char c;
        if (n == 0) {
          (*block)(ivec, ivec, key);
        }
        out[l] = ivec[n] ^ (c = in[l]);
        ivec[n] = c;
        ++l;
        n = (n + 1) % 16;
      }
      *num = n;
      return;
    }
    while (len >= 16) {
      (*block)(ivec, ivec, key);
      for (; n < 16; n += sizeof(size_t)) {
        size_t t = *(size_t *)(in + n);
        *(size_t *)(out + n) = *(size_t *)(ivec + n) ^ t;
        *(size_t *)(ivec + n) = t;
      }
      len -= 16;
      out += 16;
      in += 16;
      n = 0;
    }
    if (len) {
      (*block)(ivec, ivec, key);
      while (len--) {
        uint8_t c;
        out[n] = ivec[n] ^ (c = in[n]);
        ivec[n] = c;
        ++n;
      }
    }
    *num = n;
    return;
  }
}


/* This expects a single block of size nbits for both in and out. Note that
   it corrupts any extra bits in the last byte of out */
static void cfbr_encrypt_block(const uint8_t *in, uint8_t *out, unsigned nbits,
                               const void *key, uint8_t ivec[16], int enc,
                               block128_f block) {
  int n, rem, num;
  uint8_t ovec[16 * 2 + 1]; /* +1 because we dererefence (but don't use) one
                               byte off the end */

  if (nbits <= 0 || nbits > 128) {
    return;
  }

  /* fill in the first half of the new IV with the current IV */
  memcpy(ovec, ivec, 16);
  /* construct the new IV */
  (*block)(ivec, ivec, key);
  num = (nbits + 7) / 8;
  if (enc) {
    /* encrypt the input */
    for (n = 0; n < num; ++n) {
      out[n] = (ovec[16 + n] = in[n] ^ ivec[n]);
    }
  } else {
    /* decrypt the input */
    for (n = 0; n < num; ++n) {
      out[n] = (ovec[16 + n] = in[n]) ^ ivec[n];
    }
  }
  /* shift ovec left... */
  rem = nbits % 8;
  num = nbits / 8;
  if (rem == 0) {
    memcpy(ivec, ovec + num, 16);
  } else {
    for (n = 0; n < 16; ++n) {
      ivec[n] = ovec[n + num] << rem | ovec[n + num + 1] >> (8 - rem);
    }
  }

  /* it is not necessary to cleanse ovec, since the IV is not secret */
}

/* N.B. This expects the input to be packed, MS bit first */
void CRYPTO_cfb128_1_encrypt(const uint8_t *in, uint8_t *out, size_t bits,
                             const void *key, uint8_t ivec[16], int *num,
                             int enc, block128_f block) {
  size_t n;
  uint8_t c[1], d[1];

  assert(in && out && key && ivec && num);
  assert(*num == 0);

  for (n = 0; n < bits; ++n) {
    c[0] = (in[n / 8] & (1 << (7 - n % 8))) ? 0x80 : 0;
    cfbr_encrypt_block(c, d, 1, key, ivec, enc, block);
    out[n / 8] = (out[n / 8] & ~(1 << (unsigned int)(7 - n % 8))) |
                 ((d[0] & 0x80) >> (unsigned int)(n % 8));
  }
}

void CRYPTO_cfb128_8_encrypt(const unsigned char *in, unsigned char *out,
                             size_t length, const void *key,
                             unsigned char ivec[16], int *num, int enc,
                             block128_f block) {
  size_t n;

  assert(in && out && key && ivec && num);
  assert(*num == 0);

  for (n = 0; n < length; ++n) {
    cfbr_encrypt_block(&in[n], &out[n], 8, key, ivec, enc, block);
  }
}