/*
* KDFs defined in NIST SP 800-108
* (C) 2016 Kai Michaelis
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/sp800_108.h>
#include <botan/loadstor.h>
#include <botan/exceptn.h>
#include <iterator>

namespace Botan {

size_t SP800_108_Counter::kdf(uint8_t key[], size_t key_len,
                              const uint8_t secret[], size_t secret_len,
                              const uint8_t salt[], size_t salt_len,
                              const uint8_t label[], size_t label_len) const
   {
   const std::size_t prf_len =  m_prf->output_length();

   const uint64_t blocks_required = (key_len + prf_len - 1) / prf_len;

   if(blocks_required > 0xFFFFFFFF)
      throw Invalid_Argument("SP800_108_Counter output size too large");

   const uint8_t delim = 0;
   const uint32_t length = static_cast<uint32_t>(key_len * 8);

   uint8_t *p = key;
   uint32_t counter = 1;
   uint8_t be_len[4] = { 0 };
   secure_vector<uint8_t> tmp;

   store_be(length, be_len);
   m_prf->set_key(secret, secret_len);

   while(p < key + key_len)
      {
      const std::size_t to_copy = std::min< std::size_t >(key + key_len - p, prf_len);
      uint8_t be_cnt[4] = { 0 };

      store_be(counter, be_cnt);

      m_prf->update(be_cnt,4);
      m_prf->update(label,label_len);
      m_prf->update(delim);
      m_prf->update(salt,salt_len);
      m_prf->update(be_len,4);
      m_prf->final(tmp);

      copy_mem(p, tmp.data(), to_copy);
      p += to_copy;

      ++counter;
      BOTAN_ASSERT(counter != 0, "No counter overflow");
      }

   return key_len;
   }

size_t SP800_108_Feedback::kdf(uint8_t key[], size_t key_len,
                               const uint8_t secret[], size_t secret_len,
                               const uint8_t salt[], size_t salt_len,
                               const uint8_t label[], size_t label_len) const
   {
   const uint32_t length = static_cast<uint32_t>(key_len * 8);
   const std::size_t prf_len =  m_prf->output_length();
   const std::size_t iv_len = (salt_len >= prf_len ? prf_len : 0);
   const uint8_t delim = 0;

   const uint64_t blocks_required = (key_len + prf_len - 1) / prf_len;

   if(blocks_required > 0xFFFFFFFF)
      throw Invalid_Argument("SP800_108_Feedback output size too large");

   uint8_t *p = key;
   uint32_t counter = 1;
   uint8_t be_len[4] = { 0 };
   secure_vector< uint8_t > prev(salt, salt + iv_len);
   secure_vector< uint8_t > ctx(salt + iv_len, salt + salt_len);

   store_be(length, be_len);
   m_prf->set_key(secret, secret_len);

   while(p < key + key_len)
      {
      const std::size_t to_copy = std::min< std::size_t >(key + key_len - p, prf_len);
      uint8_t be_cnt[4] = { 0 };

      store_be(counter, be_cnt);

      m_prf->update(prev);
      m_prf->update(be_cnt,4);
      m_prf->update(label,label_len);
      m_prf->update(delim);
      m_prf->update(ctx);
      m_prf->update(be_len,4);
      m_prf->final(prev);

      copy_mem(p, prev.data(), to_copy);
      p += to_copy;

      ++counter;

      BOTAN_ASSERT(counter != 0, "No overflow");
      }

   return key_len;
   }

size_t SP800_108_Pipeline::kdf(uint8_t key[], size_t key_len,
                               const uint8_t secret[], size_t secret_len,
                               const uint8_t salt[], size_t salt_len,
                               const uint8_t label[], size_t label_len) const
   {
   const uint32_t length = static_cast<uint32_t>(key_len * 8);
   const std::size_t prf_len =  m_prf->output_length();
   const uint8_t delim = 0;

   const uint64_t blocks_required = (key_len + prf_len - 1) / prf_len;

   if(blocks_required > 0xFFFFFFFF)
      throw Invalid_Argument("SP800_108_Feedback output size too large");

   uint8_t *p = key;
   uint32_t counter = 1;
   uint8_t be_len[4] = { 0 };
   secure_vector<uint8_t> ai, ki;

   store_be(length, be_len);
   m_prf->set_key(secret,secret_len);

   // A(0)
   std::copy(label,label + label_len,std::back_inserter(ai));
   ai.emplace_back(delim);
   std::copy(salt,salt + salt_len,std::back_inserter(ai));
   std::copy(be_len,be_len + 4,std::back_inserter(ai));

   while(p < key + key_len)
      {
      // A(i)
      m_prf->update(ai);
      m_prf->final(ai);

      // K(i)
      const std::size_t to_copy = std::min< std::size_t >(key + key_len - p, prf_len);
      uint8_t be_cnt[4] = { 0 };

      store_be(counter, be_cnt);

      m_prf->update(ai);
      m_prf->update(be_cnt,4);
      m_prf->update(label, label_len);
      m_prf->update(delim);
      m_prf->update(salt, salt_len);
      m_prf->update(be_len,4);
      m_prf->final(ki);

      copy_mem(p, ki.data(), to_copy);
      p += to_copy;

      ++counter;

      BOTAN_ASSERT(counter != 0, "No overflow");
      }

   return key_len;
   }
}