kdf2.cpp

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/*
* KDF2
* (C) 1999-2007 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#include <botan/internal/kdf2.h>
#include <botan/internal/fmt.h>
#include <botan/exceptn.h>
 
namespace Botan {
 
std::string KDF2::name() const
   {
   return fmt("KDF2({})", m_hash->name());
   }
 
std::unique_ptr<KDF> KDF2::new_object() const
   {
   return std::make_unique<KDF2>(m_hash->new_object());
   }
 
void KDF2::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
   {
   if(key_len == 0)
      return;
 
   const size_t blocks_required = key_len / m_hash->output_length();
 
   if(blocks_required >= 0xFFFFFFFE)
      throw Invalid_Argument("KDF2 maximum output length exceeeded");
 
   uint32_t counter = 1;
   secure_vector<uint8_t> h;
 
   size_t offset = 0;
   while(offset != key_len)
      {
      m_hash->update(secret, secret_len);
      m_hash->update_be(counter);
      m_hash->update(label, label_len);
      m_hash->update(salt, salt_len);
      m_hash->final(h);
 
      const size_t added = std::min(h.size(), key_len - offset);
      copy_mem(&key[offset], h.data(), added);
      offset += added;
 
      counter += 1;
      BOTAN_ASSERT_NOMSG(counter != 0); // no overflow
      }
   }
 
}