skein_512.cpp

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/*
* The Skein-512 hash function
* (C) 2009,2010,2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#include <botan/internal/skein_512.h>
 
#include <botan/exceptn.h>
#include <botan/internal/fmt.h>
#include <botan/internal/loadstor.h>
#include <botan/internal/mem_utils.h>
#include <algorithm>
 
namespace Botan {
 
Skein_512::Skein_512(size_t arg_output_bits, std::string_view arg_personalization) :
      m_personalization(arg_personalization),
      m_output_bits(arg_output_bits),
      m_threefish(std::make_unique<Threefish_512>()),
      m_T(2) {
   if(m_output_bits == 0 || m_output_bits % 8 != 0 || m_output_bits > 512) {
      throw Invalid_Argument("Bad output bits size for Skein-512");
   }
 
   initial_block();
}
 
std::string Skein_512::name() const {
   if(m_personalization.empty()) {
      return fmt("Skein-512({})", m_output_bits);
   } else {
      return fmt("Skein-512({},{})", m_output_bits, m_personalization);
   }
}
 
std::unique_ptr<HashFunction> Skein_512::new_object() const {
   return std::make_unique<Skein_512>(m_output_bits, m_personalization);
}
 
std::unique_ptr<HashFunction> Skein_512::copy_state() const {
   auto copy = std::make_unique<Skein_512>(m_output_bits, m_personalization);
   copy->m_threefish->m_K = this->m_threefish->m_K;
   copy->m_T = this->m_T;
   copy->m_buffer = this->m_buffer;
   return copy;
}
 
void Skein_512::clear() {
   m_buffer.clear();
 
   initial_block();
}
 
void Skein_512::reset_tweak(type_code type, bool is_final) {
   m_T[0] = 0;
 
   m_T[1] =
      (static_cast<uint64_t>(type) << 56) | (static_cast<uint64_t>(1) << 62) | (static_cast<uint64_t>(is_final) << 63);
}
 
void Skein_512::initial_block() {
   const uint8_t zeros[64] = {0};
 
   m_threefish->set_key(zeros, sizeof(zeros));
 
   // ASCII("SHA3") followed by version (0x0001) code
   uint8_t config_str[32] = {0x53, 0x48, 0x41, 0x33, 0x01, 0x00, 0};
   store_le(uint32_t(m_output_bits), config_str + 8);
 
   reset_tweak(SKEIN_CONFIG, true);
   ubi_512(std::span{config_str});
 
   if(!m_personalization.empty()) {
      /*
        This is a limitation of this implementation, and not of the
        algorithm specification. Could be fixed relatively easily, but
        doesn't seem worth the trouble.
      */
      if(m_personalization.length() > 64) {
         throw Invalid_Argument("Skein personalization must be less than 64 bytes");
      }
 
      reset_tweak(SKEIN_PERSONALIZATION, true);
      ubi_512(as_span_of_bytes(m_personalization));
   }
 
   reset_tweak(SKEIN_MSG, false);
}
 
void Skein_512::ubi_512(std::span<const uint8_t> msg) {
   secure_vector<uint64_t> M(8);
 
   /* NOLINTNEXTLINE(*-avoid-do-while) */
   do {
      const size_t to_proc = std::min<size_t>(msg.size(), 64);
      m_T[0] += to_proc;
 
      load_le(M.data(), msg.data(), to_proc / 8);
 
      if(to_proc % 8 > 0) {
         for(size_t j = 0; j != to_proc % 8; ++j) {
            M[to_proc / 8] |= static_cast<uint64_t>(msg[8 * (to_proc / 8) + j]) << (8 * j);
         }
      }
 
      m_threefish->skein_feedfwd(M, m_T);
 
      // clear first flag if set
      m_T[1] &= ~(static_cast<uint64_t>(1) << 62);
 
      msg = msg.subspan(to_proc);
   } while(!msg.empty());
}
 
void Skein_512::add_data(std::span<const uint8_t> input) {
   BufferSlicer in(input);
 
   while(!in.empty()) {
      if(const auto one_block = m_buffer.handle_unaligned_data(in)) {
         ubi_512(one_block->data(), one_block->size());
      }
 
      if(m_buffer.in_alignment()) {
         const auto [aligned_data, full_blocks] = m_buffer.aligned_data_to_process(in);
         if(full_blocks > 0) {
            ubi_512(aligned_data.data(), aligned_data.size());
         }
      }
   }
}
 
void Skein_512::final_result(std::span<uint8_t> out) {
   m_T[1] |= (static_cast<uint64_t>(1) << 63);  // final block flag
 
   const auto pos = m_buffer.elements_in_buffer();
   m_buffer.fill_up_with_zeros();
   ubi_512(m_buffer.consume().data(), pos);
 
   std::array<uint8_t, 8> counter{};  // all zero
 
   reset_tweak(SKEIN_OUTPUT, true);
   ubi_512(counter);
 
   copy_out_le(out.first(m_output_bits / 8), m_threefish->m_K);
 
   initial_block();
}
 
}  // namespace Botan