/*

* TLSv1.2 PRF

* (C) 2004-2010 Jack Lloyd

*

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

*/

#include <botan/internal/prf_tls.h>

#include <botan/exceptn.h>

namespace Botan {

namespace {

/*

* TLS PRF P_hash function

*/

void P_hash(uint8_t out[], size_t out_len,

            MessageAuthenticationCode& mac,

            const uint8_t secret[], size_t secret_len,

            const uint8_t salt[], size_t salt_len)

   {

   try

      {

      mac.set_key(secret, secret_len);

      }

   catch(Invalid_Key_Length&)

      {

      throw Internal_Error("The premaster secret of " +

                           std::to_string(secret_len) +

                           " bytes is too long for the PRF");

      }

   secure_vector<uint8_t> A(salt, salt + salt_len);

   secure_vector<uint8_t> h;

   size_t offset = 0;

   while(offset != out_len)

      {

      A = mac.process(A);

      mac.update(A);

      mac.update(salt, salt_len);

      mac.final(h);

      const size_t writing = std::min(h.size(), out_len - offset);

      xor_buf(&out[offset], h.data(), writing);

      offset += writing;

      }

   }

}

void TLS_12_PRF::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

   {

   secure_vector<uint8_t> msg;

   msg.reserve(label_len + salt_len);

   msg += std::make_pair(label, label_len);

   msg += std::make_pair(salt, salt_len);

   P_hash(key, key_len, *m_mac, secret, secret_len, msg.data(), msg.size());

   }

}