blob: 9dd51602f35824bf18922ace7b5da909f61fcfea [file] [log] [blame]
 /* * AES key unwrap (128-bit KEK, RFC3394) * * Copyright (c) 2003-2007, Jouni Malinen * * This software may be distributed under the terms of the BSD license. * See README for more details. */ #include "includes.h" #include "common.h" #include "aes.h" #include "aes_wrap.h" /** * aes_unwrap - Unwrap key with AES Key Wrap Algorithm (128-bit KEK) (RFC3394) * @kek: Key encryption key (KEK) * @n: Length of the plaintext key in 64-bit units; e.g., 2 = 128-bit = 16 * bytes * @cipher: Wrapped key to be unwrapped, (n + 1) * 64 bits * @plain: Plaintext key, n * 64 bits * Returns: 0 on success, -1 on failure (e.g., integrity verification failed) */ int aes_unwrap(const u8 *kek, int n, const u8 *cipher, u8 *plain) { u8 a[8], *r, b[16]; int i, j; void *ctx; /* 1) Initialize variables. */ os_memcpy(a, cipher, 8); r = plain; os_memcpy(r, cipher + 8, 8 * n); ctx = aes_decrypt_init(kek, 16); if (ctx == NULL) return -1; /* 2) Compute intermediate values. * For j = 5 to 0 * For i = n to 1 * B = AES-1(K, (A ^ t) | R[i]) where t = n*j+i * A = MSB(64, B) * R[i] = LSB(64, B) */ for (j = 5; j >= 0; j--) { r = plain + (n - 1) * 8; for (i = n; i >= 1; i--) { os_memcpy(b, a, 8); b[7] ^= n * j + i; os_memcpy(b + 8, r, 8); aes_decrypt(ctx, b, b); os_memcpy(a, b, 8); os_memcpy(r, b + 8, 8); r -= 8; } } aes_decrypt_deinit(ctx); /* 3) Output results. * * These are already in @plain due to the location of temporary * variables. Just verify that the IV matches with the expected value. */ for (i = 0; i < 8; i++) { if (a[i] != 0xa6) return -1; } return 0; }