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  */
aes_wrap(const u8 * kek,size_t kek_len,int n,const u8 * plain,u8 * cipher)26 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 	a = cipher;
34 	r = cipher + 8;
35 
36 	/* 1) Initialize variables. */
37 	os_memset(a, 0xa6, 8);
38 	os_memcpy(r, plain, 8 * n);
39 
40 	ctx = aes_encrypt_init(kek, kek_len);
41 	if (ctx == NULL)
42 		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 	for (j = 0; j <= 5; j++) {
52 		r = cipher + 8;
53 		for (i = 1; i <= n; i++) {
54 			os_memcpy(b, a, 8);
55 			os_memcpy(b + 8, r, 8);
56 			aes_encrypt(ctx, b, b);
57 			os_memcpy(a, b, 8);
58 			t = n * j + i;
59 			a[7] ^= t;
60 			a[6] ^= t >> 8;
61 			a[5] ^= t >> 16;
62 			a[4] ^= t >> 24;
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