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