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-rw-r--r--src/crypto/aes-unwrap.c78
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diff --git a/src/crypto/aes-unwrap.c b/src/crypto/aes-unwrap.c
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+/*
+ * AES key unwrap (128-bit KEK, RFC3394)
+ *
+ * Copyright (c) 2003-2007, Jouni Malinen <j@w1.fi>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Alternatively, this software may be distributed under the terms of BSD
+ * license.
+ *
+ * See README and COPYING for more details.
+ */
+
+#include "includes.h"
+
+#include "common.h"
+#include "aes_i.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;
+}