text: /* ====================================================================
   * 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>
  
  #include "../../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) {
      case 16:
        cipher = EVP_aes_128_cbc();
        break;
      case 32:
        cipher = EVP_aes_256_cbc();
        break;
      default:
        return 0;
    }
  
    // 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();
    
    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);
  
    FIPS_service_indicator_unlock_state();
    if(ok) {
      AES_CMAC_verify_service_indicator(&ctx);
    }
    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);
  }
  
  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) {
    // 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();
    int ret = 0;
    uint8_t scratch[AES_BLOCK_SIZE];
  
    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, 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 end;
    }
  
    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;
  
  end:
    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) {
    // We have to avoid the underlying AES-CBC |EVP_Cipher| services updating the
    // indicator state, so we lock the state here.
    int ret = 0;
    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 end;
      }
  
      assert(ctx->block_used == block_size);
  
      if (!EVP_Cipher(&ctx->cipher_ctx, scratch, ctx->block, block_size)) {
        goto end;
      }
    }
  
    // Encrypt all but one of the remaining blocks.
    while (in_len > block_size) {
      if (!EVP_Cipher(&ctx->cipher_ctx, scratch, in, block_size)) {
        goto end;
      }
      in += block_size;
      in_len -= block_size;
    }
  
    OPENSSL_memcpy(ctx->block, in, in_len);
    ctx->block_used = in_len;
  
    ret = 1;
  end:
    FIPS_service_indicator_unlock_state();
    return ret;
  }
  
  int CMAC_Final(CMAC_CTX *ctx, uint8_t *out, size_t *out_len) {
    // 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();
    int ret = 0;
    size_t block_size = EVP_CIPHER_CTX_block_size(&ctx->cipher_ctx);
    assert(block_size <= AES_BLOCK_SIZE);
  
    *out_len = block_size;
    if (out == NULL) {
      ret = 1;
      goto end;
    }
  
    const uint8_t *mask = ctx->k1;
  
    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);
  
  end:
    FIPS_service_indicator_unlock_state();
    if(ret) {
      AES_CMAC_verify_service_indicator(ctx);
    }
    return ret;
  }
  