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/* ====================================================================
* Copyright (c) 2010 The OpenSSL Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. All advertising materials mentioning features or use of this
* software must display the following acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
*
* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
* endorse or promote products derived from this software without
* prior written permission. For written permission, please contact
* licensing@OpenSSL.org.
*
* 5. Products derived from this software may not be called "OpenSSL"
* nor may "OpenSSL" appear in their names without prior written
* permission of the OpenSSL Project.
*
* 6. Redistributions of any form whatsoever must retain the following
* acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
*
* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
* EXPRESSED 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 OpenSSL PROJECT OR
* ITS 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 <openssl/cmac.h>
#include <assert.h>
#include <string.h>
#include <openssl/aes.h>
#include <openssl/cipher.h>
#include <openssl/mem.h>
struct cmac_ctx_st {
EVP_CIPHER_CTX cipher_ctx;
/* k1 and k2 are the CMAC subkeys. See
* https://tools.ietf.org/html/rfc4493#section-2.3 */
uint8_t k1[AES_BLOCK_SIZE];
uint8_t k2[AES_BLOCK_SIZE];
/* Last (possibly partial) scratch */
uint8_t block[AES_BLOCK_SIZE];
/* block_used contains the number of valid bytes in |block|. */
unsigned block_used;
};
static void CMAC_CTX_init(CMAC_CTX *ctx) {
EVP_CIPHER_CTX_init(&ctx->cipher_ctx);
}
static void CMAC_CTX_cleanup(CMAC_CTX *ctx) {
EVP_CIPHER_CTX_cleanup(&ctx->cipher_ctx);
OPENSSL_cleanse(ctx->k1, sizeof(ctx->k1));
OPENSSL_cleanse(ctx->k2, sizeof(ctx->k2));
OPENSSL_cleanse(ctx->block, sizeof(ctx->block));
}
int AES_CMAC(uint8_t out[16], const uint8_t *key, size_t key_len,
const uint8_t *in, size_t in_len) {
const EVP_CIPHER *cipher;
switch (key_len) {
case 16:
cipher = EVP_aes_128_cbc();
break;
case 32:
cipher = EVP_aes_256_cbc();
break;
default:
return 0;
}
size_t scratch_out_len;
CMAC_CTX ctx;
CMAC_CTX_init(&ctx);
const int ok = CMAC_Init(&ctx, key, key_len, cipher, NULL /* engine */) &&
CMAC_Update(&ctx, in, in_len) &&
CMAC_Final(&ctx, out, &scratch_out_len);
CMAC_CTX_cleanup(&ctx);
return ok;
}
CMAC_CTX *CMAC_CTX_new(void) {
CMAC_CTX *ctx = OPENSSL_malloc(sizeof(*ctx));
if (ctx != NULL) {
CMAC_CTX_init(ctx);
}
return ctx;
}
void CMAC_CTX_free(CMAC_CTX *ctx) {
if (ctx == NULL) {
return;
}
CMAC_CTX_cleanup(ctx);
OPENSSL_free(ctx);
}
/* binary_field_mul_x treats the 128 bits at |in| as an element of GF(2¹²⁸)
* with a hard-coded reduction polynomial and sets |out| as x times the
* input.
*
* See https://tools.ietf.org/html/rfc4493#section-2.3 */
static void binary_field_mul_x(uint8_t out[16], const uint8_t in[16]) {
unsigned i;
/* Shift |in| to left, including carry. */
for (i = 0; i < 15; i++) {
out[i] = (in[i] << 1) | (in[i+1] >> 7);
}
/* If MSB set fixup with R. */
const uint8_t carry = in[0] >> 7;
out[i] = (in[i] << 1) ^ ((0 - carry) & 0x87);
}
static const uint8_t kZeroIV[AES_BLOCK_SIZE] = {0};
int CMAC_Init(CMAC_CTX *ctx, const void *key, size_t key_len,
const EVP_CIPHER *cipher, ENGINE *engine) {
uint8_t scratch[AES_BLOCK_SIZE];
if (EVP_CIPHER_block_size(cipher) != AES_BLOCK_SIZE ||
EVP_CIPHER_key_length(cipher) != key_len ||
!EVP_EncryptInit_ex(&ctx->cipher_ctx, cipher, NULL, key, kZeroIV) ||
!EVP_Cipher(&ctx->cipher_ctx, scratch, kZeroIV, AES_BLOCK_SIZE) ||
/* Reset context again ready for first data. */
!EVP_EncryptInit_ex(&ctx->cipher_ctx, NULL, NULL, NULL, kZeroIV)) {
return 0;
}
binary_field_mul_x(ctx->k1, scratch);
binary_field_mul_x(ctx->k2, ctx->k1);
ctx->block_used = 0;
return 1;
}
int CMAC_Reset(CMAC_CTX *ctx) {
ctx->block_used = 0;
return EVP_EncryptInit_ex(&ctx->cipher_ctx, NULL, NULL, NULL, kZeroIV);
}
int CMAC_Update(CMAC_CTX *ctx, const uint8_t *in, size_t in_len) {
uint8_t scratch[AES_BLOCK_SIZE];
if (ctx->block_used > 0) {
size_t todo = AES_BLOCK_SIZE - ctx->block_used;
if (in_len < todo) {
todo = in_len;
}
memcpy(ctx->block + ctx->block_used, in, todo);
in += todo;
in_len -= todo;
ctx->block_used += todo;
/* If |in_len| is zero then either |ctx->block_used| is less than
* |AES_BLOCK_SIZE|, in which case we can stop here, or |ctx->block_used|
* is exactly |AES_BLOCK_SIZE| but there's no more data to process. In the
* latter case we don't want to process this block now because it might be
* the last block and that block is treated specially. */
if (in_len == 0) {
return 1;
}
assert(ctx->block_used == AES_BLOCK_SIZE);
if (!EVP_Cipher(&ctx->cipher_ctx, scratch, ctx->block, AES_BLOCK_SIZE)) {
return 0;
}
}
/* Encrypt all but one of the remaining blocks. */
while (in_len > AES_BLOCK_SIZE) {
if (!EVP_Cipher(&ctx->cipher_ctx, scratch, in, AES_BLOCK_SIZE)) {
return 0;
}
in += AES_BLOCK_SIZE;
in_len -= AES_BLOCK_SIZE;
}
memcpy(ctx->block, in, in_len);
ctx->block_used = in_len;
return 1;
}
int CMAC_Final(CMAC_CTX *ctx, uint8_t *out, size_t *out_len) {
*out_len = AES_BLOCK_SIZE;
if (out == NULL) {
return 1;
}
const uint8_t *mask = ctx->k1;
if (ctx->block_used != AES_BLOCK_SIZE) {
/* If the last block is incomplete, terminate it with a single 'one' bit
* followed by zeros. */
ctx->block[ctx->block_used] = 0x80;
memset(ctx->block + ctx->block_used + 1, 0,
AES_BLOCK_SIZE - (ctx->block_used + 1));
mask = ctx->k2;
}
unsigned i;
for (i = 0; i < AES_BLOCK_SIZE; i++) {
out[i] = ctx->block[i] ^ mask[i];
}
return EVP_Cipher(&ctx->cipher_ctx, out, out, AES_BLOCK_SIZE);
}