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      1 /* ====================================================================
      2  * Copyright (c) 2010 The OpenSSL Project.  All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  *
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  *
     11  * 2. Redistributions in binary form must reproduce the above copyright
     12  *    notice, this list of conditions and the following disclaimer in
     13  *    the documentation and/or other materials provided with the
     14  *    distribution.
     15  *
     16  * 3. All advertising materials mentioning features or use of this
     17  *    software must display the following acknowledgment:
     18  *    "This product includes software developed by the OpenSSL Project
     19  *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
     20  *
     21  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
     22  *    endorse or promote products derived from this software without
     23  *    prior written permission. For written permission, please contact
     24  *    licensing (at) OpenSSL.org.
     25  *
     26  * 5. Products derived from this software may not be called "OpenSSL"
     27  *    nor may "OpenSSL" appear in their names without prior written
     28  *    permission of the OpenSSL Project.
     29  *
     30  * 6. Redistributions of any form whatsoever must retain the following
     31  *    acknowledgment:
     32  *    "This product includes software developed by the OpenSSL Project
     33  *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
     34  *
     35  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
     36  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     37  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     38  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
     39  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     40  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     41  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     42  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     43  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
     44  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     45  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
     46  * OF THE POSSIBILITY OF SUCH DAMAGE.
     47  * ==================================================================== */
     48 
     49 #include <openssl/cmac.h>
     50 
     51 #include <assert.h>
     52 #include <string.h>
     53 
     54 #include <openssl/aes.h>
     55 #include <openssl/cipher.h>
     56 #include <openssl/mem.h>
     57 
     58 #include "../internal.h"
     59 
     60 
     61 struct cmac_ctx_st {
     62   EVP_CIPHER_CTX cipher_ctx;
     63   /* k1 and k2 are the CMAC subkeys. See
     64    * https://tools.ietf.org/html/rfc4493#section-2.3 */
     65   uint8_t k1[AES_BLOCK_SIZE];
     66   uint8_t k2[AES_BLOCK_SIZE];
     67   /* Last (possibly partial) scratch */
     68   uint8_t block[AES_BLOCK_SIZE];
     69   /* block_used contains the number of valid bytes in |block|. */
     70   unsigned block_used;
     71 };
     72 
     73 static void CMAC_CTX_init(CMAC_CTX *ctx) {
     74   EVP_CIPHER_CTX_init(&ctx->cipher_ctx);
     75 }
     76 
     77 static void CMAC_CTX_cleanup(CMAC_CTX *ctx) {
     78   EVP_CIPHER_CTX_cleanup(&ctx->cipher_ctx);
     79   OPENSSL_cleanse(ctx->k1, sizeof(ctx->k1));
     80   OPENSSL_cleanse(ctx->k2, sizeof(ctx->k2));
     81   OPENSSL_cleanse(ctx->block, sizeof(ctx->block));
     82 }
     83 
     84 int AES_CMAC(uint8_t out[16], const uint8_t *key, size_t key_len,
     85              const uint8_t *in, size_t in_len) {
     86   const EVP_CIPHER *cipher;
     87   switch (key_len) {
     88     case 16:
     89       cipher = EVP_aes_128_cbc();
     90       break;
     91     case 32:
     92       cipher = EVP_aes_256_cbc();
     93       break;
     94     default:
     95       return 0;
     96   }
     97 
     98   size_t scratch_out_len;
     99   CMAC_CTX ctx;
    100   CMAC_CTX_init(&ctx);
    101 
    102   const int ok = CMAC_Init(&ctx, key, key_len, cipher, NULL /* engine */) &&
    103                  CMAC_Update(&ctx, in, in_len) &&
    104                  CMAC_Final(&ctx, out, &scratch_out_len);
    105 
    106   CMAC_CTX_cleanup(&ctx);
    107   return ok;
    108 }
    109 
    110 CMAC_CTX *CMAC_CTX_new(void) {
    111   CMAC_CTX *ctx = OPENSSL_malloc(sizeof(*ctx));
    112   if (ctx != NULL) {
    113     CMAC_CTX_init(ctx);
    114   }
    115   return ctx;
    116 }
    117 
    118 void CMAC_CTX_free(CMAC_CTX *ctx) {
    119   if (ctx == NULL) {
    120     return;
    121   }
    122 
    123   CMAC_CTX_cleanup(ctx);
    124   OPENSSL_free(ctx);
    125 }
    126 
    127 /* binary_field_mul_x treats the 128 bits at |in| as an element of GF(2)
    128  * with a hard-coded reduction polynomial and sets |out| as x times the
    129  * input.
    130  *
    131  * See https://tools.ietf.org/html/rfc4493#section-2.3 */
    132 static void binary_field_mul_x(uint8_t out[16], const uint8_t in[16]) {
    133   unsigned i;
    134 
    135   /* Shift |in| to left, including carry. */
    136   for (i = 0; i < 15; i++) {
    137     out[i] = (in[i] << 1) | (in[i+1] >> 7);
    138   }
    139 
    140   /* If MSB set fixup with R. */
    141   const uint8_t carry = in[0] >> 7;
    142   out[i] = (in[i] << 1) ^ ((0 - carry) & 0x87);
    143 }
    144 
    145 static const uint8_t kZeroIV[AES_BLOCK_SIZE] = {0};
    146 
    147 int CMAC_Init(CMAC_CTX *ctx, const void *key, size_t key_len,
    148               const EVP_CIPHER *cipher, ENGINE *engine) {
    149   uint8_t scratch[AES_BLOCK_SIZE];
    150 
    151   if (EVP_CIPHER_block_size(cipher) != AES_BLOCK_SIZE ||
    152       EVP_CIPHER_key_length(cipher) != key_len ||
    153       !EVP_EncryptInit_ex(&ctx->cipher_ctx, cipher, NULL, key, kZeroIV) ||
    154       !EVP_Cipher(&ctx->cipher_ctx, scratch, kZeroIV, AES_BLOCK_SIZE) ||
    155       /* Reset context again ready for first data. */
    156       !EVP_EncryptInit_ex(&ctx->cipher_ctx, NULL, NULL, NULL, kZeroIV)) {
    157     return 0;
    158   }
    159 
    160   binary_field_mul_x(ctx->k1, scratch);
    161   binary_field_mul_x(ctx->k2, ctx->k1);
    162   ctx->block_used = 0;
    163 
    164   return 1;
    165 }
    166 
    167 int CMAC_Reset(CMAC_CTX *ctx) {
    168   ctx->block_used = 0;
    169   return EVP_EncryptInit_ex(&ctx->cipher_ctx, NULL, NULL, NULL, kZeroIV);
    170 }
    171 
    172 int CMAC_Update(CMAC_CTX *ctx, const uint8_t *in, size_t in_len) {
    173   uint8_t scratch[AES_BLOCK_SIZE];
    174 
    175   if (ctx->block_used > 0) {
    176     size_t todo = AES_BLOCK_SIZE - ctx->block_used;
    177     if (in_len < todo) {
    178       todo = in_len;
    179     }
    180 
    181     OPENSSL_memcpy(ctx->block + ctx->block_used, in, todo);
    182     in += todo;
    183     in_len -= todo;
    184     ctx->block_used += todo;
    185 
    186     /* If |in_len| is zero then either |ctx->block_used| is less than
    187      * |AES_BLOCK_SIZE|, in which case we can stop here, or |ctx->block_used|
    188      * is exactly |AES_BLOCK_SIZE| but there's no more data to process. In the
    189      * latter case we don't want to process this block now because it might be
    190      * the last block and that block is treated specially. */
    191     if (in_len == 0) {
    192       return 1;
    193     }
    194 
    195     assert(ctx->block_used == AES_BLOCK_SIZE);
    196 
    197     if (!EVP_Cipher(&ctx->cipher_ctx, scratch, ctx->block, AES_BLOCK_SIZE)) {
    198       return 0;
    199     }
    200   }
    201 
    202   /* Encrypt all but one of the remaining blocks. */
    203   while (in_len > AES_BLOCK_SIZE) {
    204     if (!EVP_Cipher(&ctx->cipher_ctx, scratch, in, AES_BLOCK_SIZE)) {
    205       return 0;
    206     }
    207     in += AES_BLOCK_SIZE;
    208     in_len -= AES_BLOCK_SIZE;
    209   }
    210 
    211   OPENSSL_memcpy(ctx->block, in, in_len);
    212   ctx->block_used = in_len;
    213 
    214   return 1;
    215 }
    216 
    217 int CMAC_Final(CMAC_CTX *ctx, uint8_t *out, size_t *out_len) {
    218   *out_len = AES_BLOCK_SIZE;
    219   if (out == NULL) {
    220     return 1;
    221   }
    222 
    223   const uint8_t *mask = ctx->k1;
    224 
    225   if (ctx->block_used != AES_BLOCK_SIZE) {
    226     /* If the last block is incomplete, terminate it with a single 'one' bit
    227      * followed by zeros. */
    228     ctx->block[ctx->block_used] = 0x80;
    229     OPENSSL_memset(ctx->block + ctx->block_used + 1, 0,
    230                    AES_BLOCK_SIZE - (ctx->block_used + 1));
    231 
    232     mask = ctx->k2;
    233   }
    234 
    235   unsigned i;
    236   for (i = 0; i < AES_BLOCK_SIZE; i++) {
    237     out[i] = ctx->block[i] ^ mask[i];
    238   }
    239 
    240   return EVP_Cipher(&ctx->cipher_ctx, out, out, AES_BLOCK_SIZE);
    241 }
    242