/*

 * XMSS Index Registry

 * A registry for XMSS private keys, keeps track of the leaf index for

 * independend copies of the same key.

 * (C) 2016 Matthias Gierlings

 *

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

 **/

#include <botan/xmss_index_registry.h>

#include <botan/hash.h>

#include <limits>

namespace Botan {

const std::string XMSS_Index_Registry::m_index_hash_function = "SHA-256";

uint64_t XMSS_Index_Registry::make_key_id(

   const secure_vector<uint8_t>& private_seed,

   const secure_vector<uint8_t>& prf) const

   {

   std::unique_ptr<HashFunction> hash =

      HashFunction::create(m_index_hash_function);

   BOTAN_ASSERT(hash != nullptr, "XMSS_Index_Registry requires SHA-256");

   hash->update(private_seed);

   hash->update(prf);

   secure_vector<uint8_t> result = hash->final();

   uint64_t key_id = 0;

   for(size_t i = 0; i < sizeof(key_id); i++)

      {

      key_id = ((key_id << 8) | result[i]);

      }

   return key_id;

   }

std::shared_ptr<Atomic<size_t>>

XMSS_Index_Registry::get(const secure_vector<uint8_t>& private_seed,

                         const secure_vector<uint8_t>& prf)

   {

   size_t pos = get(make_key_id(private_seed, prf));

   if(pos < std::numeric_limits<size_t>::max())

      {

      return m_leaf_indices[pos];

      }

   else

      {

      return m_leaf_indices[add(make_key_id(private_seed, prf))];

      }

   }

size_t XMSS_Index_Registry::get(uint64_t id) const

   {

   for(size_t i = 0; i < m_key_ids.size(); i++)

      {

      if(m_key_ids[i] == id)

         {

         return i;

         }

      }

   return std::numeric_limits<size_t>::max();

   }

size_t XMSS_Index_Registry::add(uint64_t id, size_t last_unused)

   {

   lock_guard_type<mutex_type> lock(m_mutex);

   size_t pos = get(id);

   if(pos < m_key_ids.size())

      {

      if(last_unused > *(m_leaf_indices[pos]))

         {

         m_leaf_indices[pos] = std::make_shared<Atomic<size_t>>(last_unused);

         }

      return pos;

      }

   m_key_ids.push_back(id);

   m_leaf_indices.push_back(std::make_shared<Atomic<size_t>>(last_unused));

   return m_key_ids.size() - 1;

   }

}