113 lines
2.9 KiB
C
113 lines
2.9 KiB
C
/* $OpenBSD: key_wrap.c,v 1.5 2017/05/02 17:07:06 mikeb Exp $ */
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/*-
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* Copyright (c) 2008 Damien Bergamini <damien.bergamini@free.fr>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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/*
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* This code implements the AES Key Wrap algorithm described in RFC 3394.
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <crypto/aes.h>
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#include <crypto/key_wrap.h>
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static const u_int8_t IV[8] =
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{ 0xa6, 0xa6, 0xa6, 0xa6, 0xa6, 0xa6, 0xa6, 0xa6 };
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void
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aes_key_wrap_set_key(aes_key_wrap_ctx *ctx, const u_int8_t *K, size_t K_len)
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{
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AES_Setkey(&ctx->ctx, K, K_len);
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}
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void
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aes_key_wrap_set_key_wrap_only(aes_key_wrap_ctx *ctx, const u_int8_t *K,
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size_t K_len)
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{
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AES_Setkey(&ctx->ctx, K, K_len);
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}
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void
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aes_key_wrap(aes_key_wrap_ctx *ctx, const u_int8_t *P, size_t n, u_int8_t *C)
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{
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u_int64_t B[2], t;
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u_int8_t *A, *R;
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size_t i;
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int j;
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memmove(C + 8, P, n * 8); /* P and C may overlap */
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A = C; /* A points to C[0] */
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memcpy(A, IV, 8); /* A = IV, an initial value */
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for (j = 0, t = 1; j <= 5; j++) {
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R = C + 8;
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for (i = 1; i <= n; i++, t++) {
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/* B = A | R[i] */
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memcpy(&B[0], A, 8);
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memcpy(&B[1], R, 8);
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/* B = AES(K, B) */
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AES_Encrypt(&ctx->ctx, (caddr_t)B, (caddr_t)B);
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/* MSB(64, B) = MSB(64, B) ^ t */
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B[0] ^= htobe64(t);
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/* A = MSB(64, B) */
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memcpy(A, &B[0], 8);
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/* R[i] = LSB(64, B) */
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memcpy(R, &B[1], 8);
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R += 8;
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}
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}
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explicit_bzero(B, sizeof B);
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}
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int
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aes_key_unwrap(aes_key_wrap_ctx *ctx, const u_int8_t *C, u_int8_t *P, size_t n)
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{
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u_int64_t B[2], t;
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u_int8_t A[8], *R;
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size_t i;
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int j;
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memcpy(A, C, 8); /* A = C[0] */
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memmove(P, C + 8, n * 8); /* P and C may overlap */
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for (j = 5, t = 6 * n; j >= 0; j--) {
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R = P + (n - 1) * 8;
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for (i = n; i >= 1; i--, t--) {
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/* MSB(64, B) = A */
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memcpy(&B[0], A, 8);
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/* MSB(64, B) = MSB(64, B) ^ t */
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B[0] ^= htobe64(t);
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/* B = MSB(64, B) | R[i] */
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memcpy(&B[1], R, 8);
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/* B = AES-1(K, B) */
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AES_Decrypt(&ctx->ctx, (caddr_t)B, (caddr_t)B);
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/* A = MSB(64, B) */
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memcpy(A, &B[0], 8);
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/* R[i] = LSB(64, B) */
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memcpy(R, &B[1], 8);
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R -= 8;
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}
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}
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explicit_bzero(B, sizeof B);
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/* check that A is an appropriate initial value */
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return timingsafe_bcmp(A, IV, 8) != 0;
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}
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