/*  vim:expandtab:shiftwidth=2:tabstop=2:smarttab:
 * 
 *  Libhashkit library
 *
 *  Copyright (C) 2012 Data Differential, http://datadifferential.com/
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are
 *  met:
 *
 *      * Redistributions of source code must retain the above copyright
 *  notice, this list of conditions and the following disclaimer.
 *
 *      * 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.
 *
 *      * The names of its contributors may not be used to endorse or
 *  promote products derived from this software without specific prior
 *  written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 *  "AS IS" AND ANY EXPRESS 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 COPYRIGHT
 *  OWNER OR 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 "libhashkit/common.h"

#include "libhashkit/rijndael.hpp"

#include <cstring>

#define AES_KEY_LENGTH 256               /* 128, 192, 256 */
#define AES_BLOCK_SIZE 16

enum encrypt_t
{
  AES_ENCRYPT,
  AES_DECRYPT
};

struct _key_t {
  int nr;
  uint32_t rk[4*(AES_MAXNR +1)];
};

struct aes_key_t {
  _key_t encode_key;
  _key_t decode_key;
};

aes_key_t* aes_create_key(const char *key, const size_t key_length)
{
  aes_key_t* _aes_key= (aes_key_t*)calloc(1, sizeof(aes_key_t));
  if (_aes_key)
  {
    uint8_t rkey[AES_KEY_LENGTH/8];
    uint8_t *rkey_end= rkey +AES_KEY_LENGTH/8;
    const char *key_end= key +key_length;

    memset(rkey, 0, sizeof(rkey));      /* Set initial key  */

    uint8_t *ptr= rkey;
    const char* sptr= key;
    for (; sptr < key_end; ptr++,sptr++)
    {
      if (ptr == rkey_end)
      {
        ptr= rkey;  /*  Just loop over tmp_key until we used all key */
      }
      *ptr^= (uint8_t) *sptr;
    }

    _aes_key->decode_key.nr= rijndaelKeySetupDec(_aes_key->decode_key.rk, rkey, AES_KEY_LENGTH);
    _aes_key->encode_key.nr= rijndaelKeySetupEnc(_aes_key->encode_key.rk, rkey, AES_KEY_LENGTH);
  }

  return _aes_key;
}

aes_key_t* aes_clone_key(aes_key_t *_aes_key)
{
  if (_aes_key == NULL)
  {
    return NULL;
  }

  aes_key_t* _aes_clone_key= (aes_key_t*)calloc(1, sizeof(aes_key_t));
  if (_aes_clone_key)
  {
    memcpy(_aes_clone_key, _aes_key, sizeof(aes_key_t));
  }

  return _aes_clone_key;
}

hashkit_string_st* aes_encrypt(aes_key_t *_aes_key,
                               const char* source, size_t source_length)
{
  if (_aes_key == NULL)
  {
    return NULL;
  }

  size_t num_blocks= source_length/AES_BLOCK_SIZE;

  hashkit_string_st* destination= hashkit_string_create(source_length);
  if (destination)
  {
    char *dest= hashkit_string_c_str_mutable(destination);

    for (size_t x= num_blocks; x > 0; x--)   /* Encode complete blocks */
    { 
      rijndaelEncrypt(_aes_key->encode_key.rk, _aes_key->encode_key.nr, (const uint8_t*) source,
                      (uint8_t*) dest);
      source+= AES_BLOCK_SIZE;
      dest+= AES_BLOCK_SIZE;
    }

    uint8_t block[AES_BLOCK_SIZE];
    char pad_len= AES_BLOCK_SIZE - (source_length - AES_BLOCK_SIZE*num_blocks);
    memcpy(block, source, 16 -pad_len);
    memset(block + AES_BLOCK_SIZE -pad_len, pad_len, pad_len);
    rijndaelEncrypt(_aes_key->encode_key.rk, _aes_key->encode_key.nr, block, (uint8_t*) dest);
    hashkit_string_set_length(destination, AES_BLOCK_SIZE*(num_blocks + 1));
  }

  return destination;
}

hashkit_string_st* aes_decrypt(aes_key_t *_aes_key,
                               const char* source, size_t source_length)
{
  if (_aes_key == NULL)
  {
    return NULL;
  }

  size_t num_blocks= source_length/AES_BLOCK_SIZE;
  if ((source_length != num_blocks*AES_BLOCK_SIZE) or num_blocks ==0 )
  {
    return NULL;
  }

  hashkit_string_st* destination= hashkit_string_create(source_length);
  if (destination)
  {
    char *dest= hashkit_string_c_str_mutable(destination);

    for (size_t x = num_blocks-1; x > 0; x--)
    {
      rijndaelDecrypt(_aes_key->decode_key.rk, _aes_key->decode_key.nr, (const uint8_t*) source, (uint8_t*) dest);
      source+= AES_BLOCK_SIZE;
      dest+= AES_BLOCK_SIZE;
    }

    uint8_t block[AES_BLOCK_SIZE];
    rijndaelDecrypt(_aes_key->decode_key.rk, _aes_key->decode_key.nr, (const uint8_t*) source, block);
    /* Use last char in the block as size */
    unsigned int pad_len= (unsigned int) (unsigned char) block[AES_BLOCK_SIZE-1];
    if (pad_len > AES_BLOCK_SIZE)
    {
      hashkit_string_free(destination);
      return NULL;
    }

    /* We could also check whole padding but we do not really need this */

    memcpy(dest, block, AES_BLOCK_SIZE - pad_len);
    hashkit_string_set_length(destination, AES_BLOCK_SIZE*num_blocks - pad_len);
  }

  return destination;
}
