/*

* TLSv1.2 PRF

* (C) 2004-2010 Jack Lloyd

* (C) 2024      René Meusel, Rohde & Schwarz Cybersecurity

*

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

*/

#include <botan/internal/prf_tls.h>

#include <botan/exceptn.h>

#include <botan/mem_ops.h>

#include <botan/internal/fmt.h>

#include <botan/internal/stl_util.h>

namespace Botan {

/*

* TLS PRF P_hash function

*/

void TLS_12_PRF::perform_kdf(std::span<uint8_t> key,

                             std::span<const uint8_t> secret,

                             std::span<const uint8_t> salt,

                             std::span<const uint8_t> label) const {

   try {

      m_mac->set_key(secret);

   } catch(Invalid_Key_Length&) {

      throw Internal_Error(fmt("The premaster secret of {} bytes is too long for TLS-PRF", secret.size()));

   }

   auto A = concat<secure_vector<uint8_t>>(label, salt);

   secure_vector<uint8_t> h;

   BufferStuffer o(key);

   while(!o.full()) {

      A = m_mac->process(A);

      m_mac->update(A);

      m_mac->update(label);

      m_mac->update(salt);

      m_mac->final(h);

      const size_t writing = std::min(h.size(), o.remaining_capacity());

      xor_buf(o.next(writing), std::span{h}.first(writing));

   }

}

std::string TLS_12_PRF::name() const {

   return fmt("TLS-12-PRF({})", m_mac->name());

}

std::unique_ptr<KDF> TLS_12_PRF::new_object() const {

   return std::make_unique<TLS_12_PRF>(m_mac->new_object());

}

}  // namespace Botan