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/* $OpenBSD: key_wrap.c,v 1.3 2011/01/11 15:42:05 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;
ovbcopy(P, C + 8, 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] */
ovbcopy(C + 8, P, 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;
}
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