// Copyright 2010-2016 The OpenSSL Project Authors. All Rights Reserved.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#include <openssl/cmac.h>

#include <assert.h>

#include <limits.h>

#include <string.h>

#include <openssl/aes.h>

#include <openssl/cipher.h>

#include <openssl/mem.h>

#include "../../internal.h"

#include "../service_indicator/internal.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) {

    // WARNING: this code assumes that all supported key sizes are FIPS

    // Approved.

    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);

  // We have to verify that all the CMAC services actually succeed before

  // updating the indicator state, so we lock the state here.

  FIPS_service_indicator_lock_state();

  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);

  FIPS_service_indicator_unlock_state();

  if (ok) {

    FIPS_service_indicator_update_state();

  }

  CMAC_CTX_cleanup(&ctx);

  return ok;

}

CMAC_CTX *CMAC_CTX_new(void) {

  CMAC_CTX *ctx = reinterpret_cast<CMAC_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);

}

int CMAC_CTX_copy(CMAC_CTX *out, const CMAC_CTX *in) {

  if (!EVP_CIPHER_CTX_copy(&out->cipher_ctx, &in->cipher_ctx)) {

    return 0;

  }

  OPENSSL_memcpy(out->k1, in->k1, AES_BLOCK_SIZE);

  OPENSSL_memcpy(out->k2, in->k2, AES_BLOCK_SIZE);

  OPENSSL_memcpy(out->block, in->block, AES_BLOCK_SIZE);

  out->block_used = in->block_used;

  return 1;

}

// binary_field_mul_x_128 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_128(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);

}

// binary_field_mul_x_64 behaves like |binary_field_mul_x_128| but acts on an

// element of GF(2⁶⁴).

//

// See https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-38b.pdf

static void binary_field_mul_x_64(uint8_t out[8], const uint8_t in[8]) {

  unsigned i;

  // Shift |in| to left, including carry.

  for (i = 0; i < 7; 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) & 0x1b);

}

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) {

  int ret = 0;

  uint8_t scratch[AES_BLOCK_SIZE];

  // We have to avoid the underlying AES-CBC |EVP_CIPHER| services updating the

  // indicator state, so we lock the state here.

  FIPS_service_indicator_lock_state();

  size_t block_size = EVP_CIPHER_block_size(cipher);

  if ((block_size != AES_BLOCK_SIZE && block_size != 8 /* 3-DES */) ||

      EVP_CIPHER_key_length(cipher) != key_len ||

      !EVP_EncryptInit_ex(&ctx->cipher_ctx, cipher, NULL,

                          reinterpret_cast<const uint8_t *>(key), kZeroIV) ||

      !EVP_Cipher(&ctx->cipher_ctx, scratch, kZeroIV, block_size) ||

      // Reset context again ready for first data.

      !EVP_EncryptInit_ex(&ctx->cipher_ctx, NULL, NULL, NULL, kZeroIV)) {

    goto out;

  }

  if (block_size == AES_BLOCK_SIZE) {

    binary_field_mul_x_128(ctx->k1, scratch);

    binary_field_mul_x_128(ctx->k2, ctx->k1);

  } else {

    binary_field_mul_x_64(ctx->k1, scratch);

    binary_field_mul_x_64(ctx->k2, ctx->k1);

  }

  ctx->block_used = 0;

  ret = 1;

out:

  FIPS_service_indicator_unlock_state();

  return ret;

}

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) {

  int ret = 0;

  // We have to avoid the underlying AES-CBC |EVP_Cipher| services updating the

  // indicator state, so we lock the state here.

  FIPS_service_indicator_lock_state();

  size_t block_size = EVP_CIPHER_CTX_block_size(&ctx->cipher_ctx);

  assert(block_size <= AES_BLOCK_SIZE);

  uint8_t scratch[AES_BLOCK_SIZE];

  if (ctx->block_used > 0) {

    size_t todo = block_size - ctx->block_used;

    if (in_len < todo) {

      todo = in_len;

    }

    OPENSSL_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

    // |block_size|, in which case we can stop here, or |ctx->block_used| is

    // exactly |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) {

      ret = 1;

      goto out;

    }

    assert(ctx->block_used == block_size);

    if (!EVP_Cipher(&ctx->cipher_ctx, scratch, ctx->block, block_size)) {

      goto out;

    }

  }

  // Encrypt all but one of the remaining blocks.

  while (in_len > block_size) {

    if (!EVP_Cipher(&ctx->cipher_ctx, scratch, in, block_size)) {

      goto out;

    }

    in += block_size;

    in_len -= block_size;

  }

  OPENSSL_memcpy(ctx->block, in, in_len);

  // |in_len| is bounded by |block_size|, which fits in |unsigned|.

  static_assert(EVP_MAX_BLOCK_LENGTH < UINT_MAX,

                "EVP_MAX_BLOCK_LENGTH is too large");

  ctx->block_used = (unsigned)in_len;

  ret = 1;

out:

  FIPS_service_indicator_unlock_state();

  return ret;

}

int CMAC_Final(CMAC_CTX *ctx, uint8_t *out, size_t *out_len) {

  int ret = 0;

  size_t block_size = EVP_CIPHER_CTX_block_size(&ctx->cipher_ctx);

  assert(block_size <= AES_BLOCK_SIZE);

  // We have to avoid the underlying AES-CBC |EVP_Cipher| services updating the

  // indicator state, so we lock the state here.

  FIPS_service_indicator_lock_state();

  *out_len = block_size;

  const uint8_t *mask = ctx->k1;

  if (out == NULL) {

    ret = 1;

    goto out;

  }

  if (ctx->block_used != block_size) {

    // If the last block is incomplete, terminate it with a single 'one' bit

    // followed by zeros.

    ctx->block[ctx->block_used] = 0x80;

    OPENSSL_memset(ctx->block + ctx->block_used + 1, 0,

                   block_size - (ctx->block_used + 1));

    mask = ctx->k2;

  }

  for (unsigned i = 0; i < block_size; i++) {

    out[i] = ctx->block[i] ^ mask[i];

  }

  ret = EVP_Cipher(&ctx->cipher_ctx, out, out, block_size);

out:

  FIPS_service_indicator_unlock_state();

  if (ret) {

    FIPS_service_indicator_update_state();

  }

  return ret;

}