Line data    Source code

       1             : /*
       2             :  * AES Key Wrap Algorithm (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 (RFC3394)
      18             :  * @kek: Key encryption key (KEK)
      19             :  * @kek_len: Length of KEK in octets
      20             :  * @n: Length of the plaintext key in 64-bit units; e.g., 2 = 128-bit = 16
      21             :  * bytes
      22             :  * @plain: Plaintext key to be wrapped, n * 64 bits
      23             :  * @cipher: Wrapped key, (n + 1) * 64 bits
      24             :  * Returns: 0 on success, -1 on failure
      25             :  */
      26         809 : int aes_wrap(const u8 *kek, size_t kek_len, int n, const u8 *plain, u8 *cipher)
      27             : {
      28             :         u8 *a, *r, b[AES_BLOCK_SIZE];
      29             :         int i, j;
      30             :         void *ctx;
      31             :         unsigned int t;
      32             : 
      33         809 :         a = cipher;
      34         809 :         r = cipher + 8;
      35             : 
      36             :         /* 1) Initialize variables. */
      37         809 :         os_memset(a, 0xa6, 8);
      38         809 :         os_memcpy(r, plain, 8 * n);
      39             : 
      40         809 :         ctx = aes_encrypt_init(kek, kek_len);
      41         809 :         if (ctx == NULL)
      42           0 :                 return -1;
      43             : 
      44             :         /* 2) Calculate intermediate values.
      45             :          * For j = 0 to 5
      46             :          *     For i=1 to n
      47             :          *         B = AES(K, A | R[i])
      48             :          *         A = MSB(64, B) ^ t where t = (n*j)+i
      49             :          *         R[i] = LSB(64, B)
      50             :          */
      51        5663 :         for (j = 0; j <= 5; j++) {
      52        4854 :                 r = cipher + 8;
      53       32850 :                 for (i = 1; i <= n; i++) {
      54       27996 :                         os_memcpy(b, a, 8);
      55       27996 :                         os_memcpy(b + 8, r, 8);
      56       27996 :                         aes_encrypt(ctx, b, b);
      57       27996 :                         os_memcpy(a, b, 8);
      58       27996 :                         t = n * j + i;
      59       27996 :                         a[7] ^= t;
      60       27996 :                         a[6] ^= t >> 8;
      61       27996 :                         a[5] ^= t >> 16;
      62       27996 :                         a[4] ^= t >> 24;
      63       27996 :                         os_memcpy(r, b + 8, 8);
      64       27996 :                         r += 8;
      65             :                 }
      66             :         }
      67         809 :         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         809 :         return 0;
      76             : }