2 * AES key unwrap (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 (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
22 * @cipher: Wrapped key to be unwrapped, (n + 1) * 64 bits
23 * @plain: Plaintext key, n * 64 bits
24 * Returns: 0 on success, -1 on failure (e.g., integrity verification failed)
26 int aes_unwrap(const u8 *kek, size_t kek_len, int n, const u8 *cipher,
29 u8 a[8], *r, b[AES_BLOCK_SIZE];
34 /* 1) Initialize variables. */
35 os_memcpy(a, cipher, 8);
37 os_memcpy(r, cipher + 8, 8 * n);
39 ctx = aes_decrypt_init(kek, kek_len);
43 /* 2) Compute intermediate values.
46 * B = AES-1(K, (A ^ t) | R[i]) where t = n*j+i
50 for (j = 5; j >= 0; j--) {
51 r = plain + (n - 1) * 8;
52 for (i = n; i >= 1; i--) {
60 os_memcpy(b + 8, r, 8);
61 aes_decrypt(ctx, b, b);
63 os_memcpy(r, b + 8, 8);
67 aes_decrypt_deinit(ctx);
71 * These are already in @plain due to the location of temporary
72 * variables. Just verify that the IV matches with the expected value.
74 for (i = 0; i < 8; i++) {