/*
* 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>

namespace Botan {

/*
* Update a HMAC Calculation
*/
void HMAC::add_data(const uint8_t input[], size_t length)
   {
   verify_key_set(m_ikey.empty() == false);
   m_hash->update(input, length);
   }

/*
* Finalize a HMAC Calculation
*/
void HMAC::final_result(uint8_t mac[])
   {
   verify_key_set(m_okey.empty() == false);
   m_hash->final(mac);
   m_hash->update(m_okey);
   m_hash->update(mac, output_length());
   m_hash->final(mac);
   m_hash->update(m_ikey);
   }

Key_Length_Specification HMAC::key_spec() const
   {
   // Support very long lengths for things like PBKDF2 and the TLS PRF
   return Key_Length_Specification(0, 4096);
   }

/*
* HMAC Key Schedule
*/
void HMAC::key_schedule(const uint8_t key[], size_t length)
   {
   m_hash->clear();

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

   const uint8_t ipad = 0x36;
   const uint8_t opad = 0x5C;

   std::fill(m_ikey.begin(), m_ikey.end(), ipad);
   std::fill(m_okey.begin(), m_okey.end(), opad);

   if(length > m_hash->hash_block_size())
      {
      secure_vector<uint8_t> 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());
   }

}