2 * AES key unwrap (128-bit KEK, RFC3394)
4 * Copyright (c) 2003-2007, Jouni Malinen <j@w1.fi>
6 * This software may be distributed under the terms of the BSD license.
7 * See README for more details.
17 * aes_unwrap - Unwrap key with AES Key Wrap Algorithm (128-bit KEK) (RFC3394)
18 * @kek: Key encryption key (KEK)
19 * @n: Length of the plaintext key in 64-bit units; e.g., 2 = 128-bit = 16
21 * @cipher: Wrapped key to be unwrapped, (n + 1) * 64 bits
22 * @plain: Plaintext key, n * 64 bits
23 * Returns: 0 on success, -1 on failure (e.g., integrity verification failed)
25 int aes_unwrap(const u8 *kek, int n, const u8 *cipher, u8 *plain)
31 /* 1) Initialize variables. */
32 os_memcpy(a, cipher, 8);
34 os_memcpy(r, cipher + 8, 8 * n);
36 ctx = aes_decrypt_init(kek, 16);
40 /* 2) Compute intermediate values.
43 * B = AES-1(K, (A ^ t) | R[i]) where t = n*j+i
47 for (j = 5; j >= 0; j--) {
48 r = plain + (n - 1) * 8;
49 for (i = n; i >= 1; i--) {
53 os_memcpy(b + 8, r, 8);
54 aes_decrypt(ctx, b, b);
56 os_memcpy(r, b + 8, 8);
60 aes_decrypt_deinit(ctx);
64 * These are already in @plain due to the location of temporary
65 * variables. Just verify that the IV matches with the expected value.
67 for (i = 0; i < 8; i++) {