/*

* 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, m_hash_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);

   }

size_t HMAC::output_length() const

   {

   return m_hash_output_length;

   }

/*

* HMAC Key Schedule

*/

void HMAC::key_schedule(const uint8_t key[], size_t length)

   {

   const uint8_t ipad = 0x36;

   const uint8_t opad = 0x5C;

   m_hash->clear();

   m_ikey.resize(m_hash_block_size);

   set_mem(m_ikey.data(), m_hash_block_size, ipad);

   m_okey.resize(m_hash_block_size);

   set_mem(m_okey.data(), m_hash_block_size, opad);

   if(length > m_hash_block_size)

      {

      m_hash->update(key, length);

      m_hash->final(m_ikey.data());

      xor_buf(m_okey.data(), m_ikey.data(), m_hash_output_length);

      for(size_t i = 0; i != m_hash_output_length; ++i)

         {

         m_ikey[i] ^= ipad;

         }

      }

   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),

   m_hash_output_length(m_hash->output_length()),

   m_hash_block_size(m_hash->hash_block_size())

   {

   BOTAN_ARG_CHECK(m_hash_block_size >= m_hash_output_length,

                   "HMAC is not compatible with this hash function");

   }

}