cbc.c

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/* ====================================================================
 * 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"
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 * 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
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#include <assert.h>
#include <string.h>
 
#include <openssl/type_check.h>
 
#include "internal.h"
#include "../../internal.h"
 
 
void CRYPTO_cbc128_encrypt(const uint8_t *in, uint8_t *out, size_t len,
                           const AES_KEY *key, uint8_t ivec[16],
                           block128_f block) {
  assert(key != NULL && ivec != NULL);
  if (len == 0) {
    // Avoid |ivec| == |iv| in the |memcpy| below, which is not legal in C.
    return;
  }
 
  assert(in != NULL && out != NULL);
  size_t n;
  const uint8_t *iv = ivec;
  while (len >= 16) {
    for (n = 0; n < 16; n += sizeof(crypto_word_t)) {
      CRYPTO_store_word_le(
          out + n, CRYPTO_load_word_le(in + n) ^ CRYPTO_load_word_le(iv + n));
    }
    (*block)(out, out, key);
    iv = out;
    len -= 16;
    in += 16;
    out += 16;
  }
 
  while (len) {
    for (n = 0; n < 16 && n < len; ++n) {
      out[n] = in[n] ^ iv[n];
    }
    for (; n < 16; ++n) {
      out[n] = iv[n];
    }
    (*block)(out, out, key);
    iv = out;
    if (len <= 16) {
      break;
    }
    len -= 16;
    in += 16;
    out += 16;
  }
 
  OPENSSL_memcpy(ivec, iv, 16);
}
 
void CRYPTO_cbc128_decrypt(const uint8_t *in, uint8_t *out, size_t len,
                           const AES_KEY *key, uint8_t ivec[16],
                           block128_f block) {
  assert(key != NULL && ivec != NULL);
  if (len == 0) {
    // Avoid |ivec| == |iv| in the |memcpy| below, which is not legal in C.
    return;
  }
 
  assert(in != NULL && out != NULL);
 
  const uintptr_t inptr = (uintptr_t) in;
  const uintptr_t outptr = (uintptr_t) out;
  // If |in| and |out| alias, |in| must be ahead.
  assert(inptr >= outptr || inptr + len <= outptr);
 
  size_t n;
  union {
    crypto_word_t t[16 / sizeof(crypto_word_t)];
    uint8_t c[16];
  } tmp;
 
  if ((inptr >= 32 && outptr <= inptr - 32) || inptr < outptr) {
    // If |out| is at least two blocks behind |in| or completely disjoint, there
    // is no need to decrypt to a temporary block.
    OPENSSL_STATIC_ASSERT(16 % sizeof(crypto_word_t) == 0,
                          "block cannot be evenly divided into words");
    const uint8_t *iv = ivec;
    while (len >= 16) {
      (*block)(in, out, key);
      for (n = 0; n < 16; n += sizeof(crypto_word_t)) {
        CRYPTO_store_word_le(out + n, CRYPTO_load_word_le(out + n) ^
                                          CRYPTO_load_word_le(iv + n));
      }
      iv = in;
      len -= 16;
      in += 16;
      out += 16;
    }
    OPENSSL_memcpy(ivec, iv, 16);
  } else {
    OPENSSL_STATIC_ASSERT(16 % sizeof(crypto_word_t) == 0,
                          "block cannot be evenly divided into words");
 
    while (len >= 16) {
      (*block)(in, tmp.c, key);
      for (n = 0; n < 16; n += sizeof(crypto_word_t)) {
        crypto_word_t c = CRYPTO_load_word_le(in + n);
        CRYPTO_store_word_le(out + n, tmp.t[n / sizeof(crypto_word_t)] ^
                                          CRYPTO_load_word_le(ivec + n));
        CRYPTO_store_word_le(ivec + n, c);
      }
      len -= 16;
      in += 16;
      out += 16;
    }
  }
 
  while (len) {
    uint8_t c;
    (*block)(in, tmp.c, key);
    for (n = 0; n < 16 && n < len; ++n) {
      c = in[n];
      out[n] = tmp.c[n] ^ ivec[n];
      ivec[n] = c;
    }
    if (len <= 16) {
      for (; n < 16; ++n) {
        ivec[n] = in[n];
      }
      break;
    }
    len -= 16;
    in += 16;
    out += 16;
  }
}