/*
* HMAC
* (C) 1999-2007,2014 Jack Lloyd
*     2007 Yves Jerschow
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/hmac.h>
#include <botan/lookup.h>

namespace Botan {

HMAC* HMAC::make(const Spec& spec)
   {
   if(spec.arg_count() == 1)
      {
      if(HashFunction* h = get_hash_function(spec.arg(0)))
         return new HMAC(h);
      }
   return nullptr;
   }

/*
* Update a HMAC Calculation
*/
void HMAC::add_data(const byte input[], size_t length)
   {
   m_hash->update(input, length);
   }

/*
* Finalize a HMAC Calculation
*/
void HMAC::final_result(byte mac[])
   {
   m_hash->final(mac);
   m_hash->update(m_okey);
   m_hash->update(mac, output_length());
   m_hash->final(mac);
   m_hash->update(m_ikey);
   }

/*
* HMAC Key Schedule
*/
void HMAC::key_schedule(const byte key[], size_t length)
   {
   m_hash->clear();

   m_ikey.resize(m_hash->hash_block_size());
   m_okey.resize(m_hash->hash_block_size());

   std::fill(m_ikey.begin(), m_ikey.end(), 0x36);
   std::fill(m_okey.begin(), m_okey.end(), 0x5C);

   if(length > m_hash->hash_block_size())
      {
      secure_vector<byte> hmac_key = m_hash->process(key, length);
      xor_buf(m_ikey, hmac_key, hmac_key.size());
      xor_buf(m_okey, hmac_key, hmac_key.size());
      }
   else
      {
      xor_buf(m_ikey, key, length);
      xor_buf(m_okey, key, length);
      }

   m_hash->update(m_ikey);
   }

/*
* Clear memory of sensitive data
*/
void HMAC::clear()
   {
   m_hash->clear();
   zap(m_ikey);
   zap(m_okey);
   }

/*
* Return the name of this type
*/
std::string HMAC::name() const
   {
   return "HMAC(" + m_hash->name() + ")";
   }

/*
* Return a clone of this object
*/
MessageAuthenticationCode* HMAC::clone() const
   {
   return new HMAC(m_hash->clone());
   }

/*
* HMAC Constructor
*/
HMAC::HMAC(HashFunction* hash) : m_hash(hash)
   {
   if(m_hash->hash_block_size() == 0)
      throw Invalid_Argument("HMAC cannot be used with " + m_hash->name());
   }

}