aes-wrap.c revision 8d520ff1dc2da35cdca849e982051b86468016d8 
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 */
31int 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}
77