src/crypto/aes-wrap.c

   1 /*
   2  * AES Key Wrap Algorithm (128-bit KEK) (RFC3394)
   3  *
   4  * Copyright (c) 2003-2007, Jouni Malinen <j@w1.fi>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * Alternatively, this software may be distributed under the terms of BSD
  11  * license.
  12  *
  13  * See README and COPYING for more details.
  14  */
  15
  16 #include "includes.h"
  17
  18 #include "common.h"
  19 #include "aes.h"
  20 #include "aes_wrap.h"
  21
  22 /**
  23  * aes_wrap - Wrap keys with AES Key Wrap Algorithm (128-bit KEK) (RFC3394)
  24  * @kek: 16-octet Key encryption key (KEK)
  25  * @n: Length of the plaintext key in 64-bit units; e.g., 2 = 128-bit = 16
  26  * bytes
  27  * @plain: Plaintext key to be wrapped, n * 64 bits
  28  * @cipher: Wrapped key, (n + 1) * 64 bits
  29  * Returns: 0 on success, -1 on failure
  30  */
  31 int aes_wrap(const u8 *kek, int n, const u8 *plain, u8 *cipher)
  32 {
  33         u8 *a, *r, b[16];
  34         int i, j;
  35         void *ctx;
  36
  37         a = cipher;
  38         r = cipher + 8;
  39
  40         /* 1) Initialize variables. */
  41         os_memset(a, 0xa6, 8);
  42         os_memcpy(r, plain, 8 * n);
  43
  44         ctx = aes_encrypt_init(kek, 16);
  45         if (ctx == NULL)
  46                 return -1;
  47
  48         /* 2) Calculate intermediate values.
  49          * For j = 0 to 5
  50          *     For i=1 to n
  51          *         B = AES(K, A | R[i])
  52          *         A = MSB(64, B) ^ t where t = (n*j)+i
  53          *         R[i] = LSB(64, B)
  54          */
  55         for (j = 0; j <= 5; j++) {
  56                 r = cipher + 8;
  57                 for (i = 1; i <= n; i++) {
  58                         os_memcpy(b, a, 8);
  59                         os_memcpy(b + 8, r, 8);
  60                         aes_encrypt(ctx, b, b);
  61                         os_memcpy(a, b, 8);
  62                         a[7] ^= n * j + i;
  63                         os_memcpy(r, b + 8, 8);
  64                         r += 8;
  65                 }
  66         }
  67         aes_encrypt_deinit(ctx);
  68
  69         /* 3) Output the results.
  70          *
  71          * These are already in @cipher due to the location of temporary
  72          * variables.
  73          */
  74
  75         return 0;
  76 }