/**
 * dot11decrypt_rijndael.c
 *
 * @version 3.0 (December 2000)
 *
 * Optimised ANSI C code for the Rijndael cipher (now AES)
 *
 * @author Vincent Rijmen <vincent.rijmen@esat.kuleuven.ac.be>
 * @author Antoon Bosselaers <antoon.bosselaers@esat.kuleuven.ac.be>
 * @author Paulo Barreto <paulo.barreto@terra.com.br>
 *
 * This code is hereby placed in the public domain.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ''AS IS'' AND ANY EXPRESS
 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#include "config.h"
#include "dot11decrypt_rijndael.h"

#include "dot11decrypt_debug.h"
#include <glib.h>
#include <wsutil/wsgcrypt.h>

/* Based on RFC 3394 and NIST AES Key Wrap Specification pseudo-code.

This function is used to unwrap an encrypted AES key.  One example of its use is
in the WPA-2 protocol to get the group key.
*/
UCHAR *
AES_unwrap(const UCHAR *kek, UINT16 key_len, const UCHAR *cipher_text, UINT16 cipher_len)
{
	UCHAR *output;
	UCHAR a[8], b[16];
	UCHAR *r;
	gint16 i, j, n;
	gcry_cipher_hd_t rijndael_handle;

	if (kek == NULL || cipher_len < 16 || cipher_text == NULL) {
		return NULL; /* "should not happen" */
	}

	/* Allocate buffer for the unwrapped key */

	output = (guint8 *) g_malloc0(cipher_len);

	/* Initialize variables */

	n = (cipher_len/8)-1;  /* the algorithm works on 64-bits at a time */
	memcpy(a, cipher_text, 8);
	r = output;
	memcpy(r, cipher_text+8, cipher_len - 8);

	/* Compute intermediate values */

	if (gcry_cipher_open(&rijndael_handle, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_ECB, 0)) {
		return output;
	}
	if (gcry_cipher_setkey(rijndael_handle, kek, key_len)) {
		gcry_cipher_close(rijndael_handle);
		return output;
	}
	for (j=5; j >= 0; --j){
		r = output + (n - 1) * 8;
		/* DEBUG_DUMP("r1", (r-8), 8); */
		/* DEBUG_DUMP("r2", r, 8); */
		for (i = n; i >= 1; --i){
			UINT16 t = (n*j) + i;
			/* DEBUG_DUMP("a", a, 8); */
			memcpy(b, a, 8);
			b[7] ^= t;
			/* DEBUG_DUMP("a plus t", b, 8); */
			memcpy(b+8, r, 8);
			gcry_cipher_decrypt(rijndael_handle, b, 16, NULL, 0);
			/* DEBUG_DUMP("aes decrypt", b, 16) */
			memcpy(a,b,8);
			memcpy(r, b+8, 8);
			r -= 8;
		}
	}
	gcry_cipher_close(rijndael_handle);

	/* DEBUG_DUMP("a", a, 8); */
	/* DEBUG_DUMP("output", output, cipher_len - 8); */

	return output;
}

/*																										*/
/******************************************************************************/
