crypto/aes/key_wrap.c

/* ====================================================================
 * Copyright (c) 2001-2011 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:
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    distribution.
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 * 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/)"
 *
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 *    openssl-core@openssl.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
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 *    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
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 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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 * ==================================================================== */

#include <openssl/aes.h>

#include <limits.h>
#include <string.h>

#include <openssl/mem.h>


/* kDefaultIV is the default IV value given in RFC 3394, 2.2.3.1. */
static const uint8_t kDefaultIV[] = {
    0xa6, 0xa6, 0xa6, 0xa6, 0xa6, 0xa6, 0xa6, 0xa6,
};

static const unsigned kBound = 6;

int AES_wrap_key(const AES_KEY *key, const uint8_t *iv, uint8_t *out,
                 const uint8_t *in, size_t in_len) {
  /* See RFC 3394, section 2.2.1. */

  if (in_len > INT_MAX - 8 || in_len < 8 || in_len % 8 != 0) {
    return -1;
  }

  if (iv == NULL) {
    iv = kDefaultIV;
  }

  memmove(out + 8, in, in_len);
  uint8_t A[AES_BLOCK_SIZE];
  memcpy(A, iv, 8);

  size_t n = in_len / 8;

  for (unsigned j = 0; j < kBound; j++) {
    for (size_t i = 1; i <= n; i++) {
      memcpy(A + 8, out + 8 * i, 8);
      AES_encrypt(A, A, key);

      uint32_t t = (uint32_t)(n * j + i);
      A[7] ^= t & 0xff;
      A[6] ^= (t >> 8) & 0xff;
      A[5] ^= (t >> 16) & 0xff;
      A[4] ^= (t >> 24) & 0xff;
      memcpy(out + 8 * i, A + 8, 8);
    }
  }

  memcpy(out, A, 8);
  return (int)in_len + 8;
}

int AES_unwrap_key(const AES_KEY *key, const uint8_t *iv, uint8_t *out,
                   const uint8_t *in, size_t in_len) {
  /* See RFC 3394, section 2.2.2. */

  if (in_len > INT_MAX || in_len < 16 || in_len % 8 != 0) {
    return -1;
  }

  if (iv == NULL) {
    iv = kDefaultIV;
  }

  uint8_t A[AES_BLOCK_SIZE];
  memcpy(A, in, 8);
  memmove(out, in + 8, in_len - 8);

  size_t n = (in_len / 8) - 1;

  for (unsigned j = kBound - 1; j < kBound; j--) {
    for (size_t i = n; i > 0; i--) {
      uint32_t t = (uint32_t)(n * j + i);
      A[7] ^= t & 0xff;
      A[6] ^= (t >> 8) & 0xff;
      A[5] ^= (t >> 16) & 0xff;
      A[4] ^= (t >> 24) & 0xff;
      memcpy(A + 8, out + 8 * (i - 1), 8);
      AES_decrypt(A, A, key);
      memcpy(out + 8 * (i - 1), A + 8, 8);
    }
  }

  if (CRYPTO_memcmp(A, iv, 8) != 0) {
    return -1;
  }

  return (int)in_len - 8;
}