/*

* OpenPGP S2K

* (C) 1999-2007,2017 Jack Lloyd

* (C) 2018 Ribose Inc

*

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

*/

#include <botan/pgp_s2k.h>

#include <botan/exceptn.h>

#include <botan/internal/timer.h>

#include <algorithm>

namespace Botan {

namespace {

void pgp_s2k(HashFunction& hash,

             uint8_t output_buf[], size_t output_len,

             const char* password, const size_t password_size,

             const uint8_t salt[], size_t salt_len,

             size_t iterations)

   {

   if(iterations > 1 && salt_len == 0)

      throw Invalid_Argument("OpenPGP S2K requires a salt in iterated mode");

   secure_vector<uint8_t> input_buf(salt_len + password_size);

   if(salt_len > 0)

      {

      copy_mem(&input_buf[0], salt, salt_len);

      }

   if(password_size > 0)

      {

      copy_mem(&input_buf[salt_len],

               cast_char_ptr_to_uint8(password),

               password_size);

      }

   secure_vector<uint8_t> hash_buf(hash.output_length());

   size_t pass = 0;

   size_t generated = 0;

   while(generated != output_len)

      {

      const size_t output_this_pass =

         std::min(hash_buf.size(), output_len - generated);

      // Preload some number of zero bytes (empty first iteration)

      std::vector<uint8_t> zero_padding(pass);

      hash.update(zero_padding);

      // The input is always fully processed even if iterations is very small

      if(input_buf.empty() == false)

         {

         size_t left = std::max(iterations, input_buf.size());

         while(left > 0)

            {

            const size_t input_to_take = std::min(left, input_buf.size());

            hash.update(input_buf.data(), input_to_take);

            left -= input_to_take;

            }

         }

      hash.final(hash_buf.data());

      copy_mem(output_buf + generated, hash_buf.data(), output_this_pass);

      generated += output_this_pass;

      ++pass;

      }

   }

}

size_t OpenPGP_S2K::pbkdf(uint8_t output_buf[], size_t output_len,

                          const std::string& password,

                          const uint8_t salt[], size_t salt_len,

                          size_t iterations,

                          std::chrono::milliseconds msec) const

   {

   std::unique_ptr<PasswordHash> pwdhash;

   if(iterations == 0)

      {

      RFC4880_S2K_Family s2k_params(m_hash->clone());

      iterations = s2k_params.tune(output_len, msec, 0)->iterations();

      }

   pgp_s2k(*m_hash, output_buf, output_len,

           password.c_str(), password.size(),

           salt, salt_len,

           iterations);

   return iterations;

   }

std::string RFC4880_S2K_Family::name() const

   {

   return "OpenPGP-S2K(" + m_hash->name() + ")";

   }

std::unique_ptr<PasswordHash> RFC4880_S2K_Family::tune(size_t output_len, std::chrono::milliseconds msec, size_t) const

   {

   const auto tune_time = BOTAN_PBKDF_TUNING_TIME;

   const size_t buf_size = 1024;

   std::vector<uint8_t> buffer(buf_size);

   Timer timer("RFC4880_S2K", buf_size);

   timer.run_until_elapsed(tune_time, [&]() {

      m_hash->update(buffer);

      });

   const double hash_bytes_per_second = timer.bytes_per_second();

   const uint64_t desired_nsec = msec.count() * 1000000;

   const size_t hash_size = m_hash->output_length();

   const size_t blocks_required = (output_len <= hash_size ? 1 : (output_len + hash_size - 1) / hash_size);

   const double bytes_to_be_hashed = (hash_bytes_per_second * (desired_nsec / 1000000000.0)) / blocks_required;

   const size_t iterations = RFC4880_round_iterations(static_cast<size_t>(bytes_to_be_hashed));

   return std::make_unique<RFC4880_S2K>(m_hash->clone(), iterations);

   }

std::unique_ptr<PasswordHash> RFC4880_S2K_Family::from_params(size_t iter, size_t, size_t) const

   {

   return std::make_unique<RFC4880_S2K>(m_hash->clone(), iter);

   }

std::unique_ptr<PasswordHash> RFC4880_S2K_Family::default_params() const

   {

   return std::make_unique<RFC4880_S2K>(m_hash->clone(), 50331648);

   }

std::unique_ptr<PasswordHash> RFC4880_S2K_Family::from_iterations(size_t iter) const

   {

   return std::make_unique<RFC4880_S2K>(m_hash->clone(), iter);

   }

RFC4880_S2K::RFC4880_S2K(HashFunction* hash, size_t iterations) :

   m_hash(hash),

   m_iterations(iterations)

   {

   }

std::string RFC4880_S2K::to_string() const

   {

   return "OpenPGP-S2K(" + m_hash->name() + "," + std::to_string(m_iterations) + ")";

   }

void RFC4880_S2K::derive_key(uint8_t out[], size_t out_len,

                             const char* password, const size_t password_len,

                             const uint8_t salt[], size_t salt_len) const

   {

   pgp_s2k(*m_hash, out, out_len,

           password, password_len,

           salt, salt_len,

           m_iterations);

   }

}