/*

* Merkle-Damgard Hash Function

* (C) 1999-2008,2018 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/mdx_hash.h>

#include <botan/exceptn.h>

#include <botan/loadstor.h>

#include <botan/internal/bit_ops.h>

namespace Botan {

/*

* MDx_HashFunction Constructor

*/

MDx_HashFunction::MDx_HashFunction(size_t block_len,

                                   bool byte_big_endian,

                                   bool bit_big_endian,

                                   uint8_t cnt_size) :

   m_pad_char(bit_big_endian == true ? 0x80 : 0x01),

   m_counter_size(cnt_size),

   m_block_bits(ceil_log2(block_len)),

   m_count_big_endian(byte_big_endian),

   m_count(0),

   m_buffer(block_len),

   m_position(0)

   {

   if(!is_power_of_2(block_len))

      throw Invalid_Argument("MDx_HashFunction block length must be a power of 2");

   if(m_block_bits < 3 || m_block_bits > 16)

      throw Invalid_Argument("MDx_HashFunction block size too large or too small");

   if(m_counter_size < 8 || m_counter_size > block_len)

      throw Invalid_State("MDx_HashFunction invalid counter length");

   }

/*

* Clear memory of sensitive data

*/

void MDx_HashFunction::clear()

   {

   zeroise(m_buffer);

   m_count = m_position = 0;

   }

/*

* Update the hash

*/

void MDx_HashFunction::add_data(const uint8_t input[], size_t length)

   {

   const size_t block_len = static_cast<size_t>(1) << m_block_bits;

   m_count += length;

   if(m_position)

      {

      buffer_insert(m_buffer, m_position, input, length);

      if(m_position + length >= block_len)

         {

         compress_n(m_buffer.data(), 1);

         input += (block_len - m_position);

         length -= (block_len - m_position);

         m_position = 0;

         }

      }

   // Just in case the compiler can't figure out block_len is a power of 2

   const size_t full_blocks = length >> m_block_bits;

   const size_t remaining   = length & (block_len - 1);

   if(full_blocks > 0)

      {

      compress_n(input, full_blocks);

      }

   buffer_insert(m_buffer, m_position, input + full_blocks * block_len, remaining);

   m_position += remaining;

   }

/*

* Finalize a hash

*/

void MDx_HashFunction::final_result(uint8_t output[])

   {

   const size_t block_len = static_cast<size_t>(1) << m_block_bits;

   clear_mem(&m_buffer[m_position], block_len - m_position);

   m_buffer[m_position] = m_pad_char;

   if(m_position >= block_len - m_counter_size)

      {

      compress_n(m_buffer.data(), 1);

      zeroise(m_buffer);

      }

   write_count(&m_buffer[block_len - m_counter_size]);

   compress_n(m_buffer.data(), 1);

   copy_out(output);

   clear();

   }

/*

* Write the count bits to the buffer

*/

void MDx_HashFunction::write_count(uint8_t out[])

   {

   BOTAN_ASSERT_NOMSG(m_counter_size <= output_length());

   BOTAN_ASSERT_NOMSG(m_counter_size >= 8);

   const uint64_t bit_count = m_count * 8;

   if(m_count_big_endian)

      store_be(bit_count, out + m_counter_size - 8);

   else

      store_le(bit_count, out + m_counter_size - 8);

   }

}