/*	$OpenBSD: key_wrap.c,v 1.4 2013/06/11 18:45:08 deraadt Exp $	*/

/*-
 * Copyright (c) 2008 Damien Bergamini <damien.bergamini@free.fr>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * This code implements the AES Key Wrap algorithm described in RFC 3394.
 */

#include <sys/param.h>
#include <sys/systm.h>

#include <crypto/rijndael.h>
#include <crypto/key_wrap.h>

static const u_int8_t IV[8] =
	{ 0xa6, 0xa6, 0xa6, 0xa6, 0xa6, 0xa6, 0xa6, 0xa6 };

void
aes_key_wrap_set_key(aes_key_wrap_ctx *ctx, const u_int8_t *K, size_t K_len)
{
	rijndael_set_key(&ctx->ctx, K, K_len * NBBY);
}

void
aes_key_wrap_set_key_wrap_only(aes_key_wrap_ctx *ctx, const u_int8_t *K,
    size_t K_len)
{
	rijndael_set_key_enc_only(&ctx->ctx, K, K_len * NBBY);
}

void
aes_key_wrap(aes_key_wrap_ctx *ctx, const u_int8_t *P, size_t n, u_int8_t *C)
{
	u_int64_t B[2], t;
	u_int8_t *A, *R;
	size_t i;
	int j;

	memmove(C + 8, P, n * 8);	/* P and C may overlap */
	A = C;				/* A points to C[0] */
	memcpy(A, IV, 8);		/* A = IV, an initial value */

	for (j = 0, t = 1; j <= 5; j++) {
		R = C + 8;
		for (i = 1; i <= n; i++, t++) {
			/* B = A | R[i] */
			memcpy(&B[0], A, 8);
			memcpy(&B[1], R, 8);
			/* B = AES(K, B) */
			rijndael_encrypt(&ctx->ctx, (caddr_t)B, (caddr_t)B);
			/* MSB(64, B) = MSB(64, B) ^ t */
			B[0] ^= htobe64(t);
			/* A = MSB(64, B) */
			memcpy(A, &B[0], 8);
			/* R[i] = LSB(64, B) */
			memcpy(R, &B[1], 8);

			R += 8;
		}
	}
	explicit_bzero(B, sizeof B);
}

int
aes_key_unwrap(aes_key_wrap_ctx *ctx, const u_int8_t *C, u_int8_t *P, size_t n)
{
	u_int64_t B[2], t;
	u_int8_t A[8], *R;
	size_t i;
	int j;

	memcpy(A, C, 8);		/* A = C[0] */
	memmove(P, C + 8, n * 8);	/* P and C may overlap */

	for (j = 5, t = 6 * n; j >= 0; j--) {
		R = P + (n - 1) * 8;
		for (i = n; i >= 1; i--, t--) {
			/* MSB(64, B) = A */
			memcpy(&B[0], A, 8);
			/* MSB(64, B) = MSB(64, B) ^ t */
			B[0] ^= htobe64(t);
			/* B = MSB(64, B) | R[i] */
			memcpy(&B[1], R, 8);
			/* B = AES-1(K, B) */
			rijndael_decrypt(&ctx->ctx, (caddr_t)B, (caddr_t)B);
			/* A = MSB(64, B) */
			memcpy(A, &B[0], 8);
			/* R[i] = LSB(64, B) */
			memcpy(R, &B[1], 8);

			R -= 8;
		}
	}
	explicit_bzero(B, sizeof B);

	/* check that A is an appropriate initial value */
	return timingsafe_bcmp(A, IV, 8) != 0;
}
