/*

* Discrete Logarithm Parameters

* (C) 1999-2008,2015,2018 Jack Lloyd

*

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

*/

#include <botan/dl_group.h>

#include <botan/numthry.h>

#include <botan/reducer.h>

#include <botan/internal/primality.h>

#include <botan/internal/monty.h>

#include <botan/internal/divide.h>

#include <botan/der_enc.h>

#include <botan/ber_dec.h>

#include <botan/pem.h>

#include <botan/internal/workfactor.h>

#include <botan/internal/monty_exp.h>

namespace Botan {

class DL_Group_Data final

   {

   public:

      DL_Group_Data(const BigInt& p, const BigInt& q, const BigInt& g, DL_Group_Source source) :

         m_p(p), m_q(q), m_g(g),

         m_mod_p(p),

         m_mod_q(q),

         m_monty_params(std::make_shared<Montgomery_Params>(m_p, m_mod_p)),

         m_monty(monty_precompute(m_monty_params, m_g, /*window bits=*/4)),

         m_p_bits(p.bits()),

         m_q_bits(q.bits()),

         m_estimated_strength(dl_work_factor(m_p_bits)),

         m_exponent_bits(dl_exponent_size(m_p_bits)),

         m_source(source)

         {

         }

      ~DL_Group_Data() = default;

      DL_Group_Data(const DL_Group_Data& other) = delete;

      DL_Group_Data& operator=(const DL_Group_Data& other) = delete;

      const BigInt& p() const { return m_p; }

      const BigInt& q() const { return m_q; }

      const BigInt& g() const { return m_g; }

      BigInt mod_p(const BigInt& x) const { return m_mod_p.reduce(x); }

      BigInt multiply_mod_p(const BigInt& x, const BigInt& y) const

         {

         return m_mod_p.multiply(x, y);

         }

      BigInt mod_q(const BigInt& x) const { return m_mod_q.reduce(x); }

      BigInt multiply_mod_q(const BigInt& x, const BigInt& y) const

         {

         return m_mod_q.multiply(x, y);

         }

      BigInt square_mod_q(const BigInt& x) const

         {

         return m_mod_q.square(x);

         }

      std::shared_ptr<const Montgomery_Params> monty_params_p() const

         { return m_monty_params; }

      size_t p_bits() const { return m_p_bits; }

      size_t q_bits() const { return m_q_bits; }

      size_t p_bytes() const { return (m_p_bits + 7) / 8; }

      size_t q_bytes() const { return (m_q_bits + 7) / 8; }

      size_t estimated_strength() const { return m_estimated_strength; }

      size_t exponent_bits() const { return m_exponent_bits; }

      BigInt power_g_p(const BigInt& k, size_t max_k_bits) const

         {

         return monty_execute(*m_monty, k, max_k_bits);

         }

      BigInt power_g_p_vartime(const BigInt& k) const

         {

         return monty_execute_vartime(*m_monty, k);

         }

      BigInt power_b_p(const BigInt& b, const BigInt& k, size_t max_k_bits) const

         {

         return monty_exp(m_monty_params, b, k, max_k_bits);

         }

      BigInt power_b_p_vartime(const BigInt& b, const BigInt& k) const

         {

         return monty_exp_vartime(m_monty_params, b, k);

         }

      bool q_is_set() const { return m_q_bits > 0; }

      void assert_q_is_set(const std::string& function) const

         {

         if(q_is_set() == false)

            throw Invalid_State("DL_Group::" + function + " q is not set for this group");

         }

      DL_Group_Source source() const { return m_source; }

   private:

      BigInt m_p;

      BigInt m_q;

      BigInt m_g;

      Modular_Reducer m_mod_p;

      Modular_Reducer m_mod_q;

      std::shared_ptr<const Montgomery_Params> m_monty_params;

      std::shared_ptr<const Montgomery_Exponentation_State> m_monty;

      size_t m_p_bits;

      size_t m_q_bits;

      size_t m_estimated_strength;

      size_t m_exponent_bits;

      DL_Group_Source m_source;

   };

//static

std::shared_ptr<DL_Group_Data> DL_Group::BER_decode_DL_group(const uint8_t data[], size_t data_len,

                                                             DL_Group_Format format,

                                                             DL_Group_Source source)

   {

   BigInt p, q, g;

   BER_Decoder decoder(data, data_len);

   BER_Decoder ber = decoder.start_sequence();

   if(format == DL_Group_Format::ANSI_X9_57)

      {

      ber.decode(p)

         .decode(q)

         .decode(g)

         .verify_end();

      }

   else if(format == DL_Group_Format::ANSI_X9_42)

      {

      ber.decode(p)

         .decode(g)

         .decode(q)

         .discard_remaining();

      }

   else if(format == DL_Group_Format::PKCS_3)

      {

      // q is left as zero

      ber.decode(p)

         .decode(g)

         .discard_remaining();

      }

   else

      throw Invalid_Argument("Unknown DL_Group encoding");

   return std::make_shared<DL_Group_Data>(p, q, g, source);

   }

//static

std::shared_ptr<DL_Group_Data>

DL_Group::load_DL_group_info(const char* p_str,

                             const char* q_str,

                             const char* g_str)

   {

   const BigInt p(p_str);

   const BigInt q(q_str);

   const BigInt g(g_str);

   return std::make_shared<DL_Group_Data>(p, q, g, DL_Group_Source::Builtin);

   }

//static

std::shared_ptr<DL_Group_Data>

DL_Group::load_DL_group_info(const char* p_str,

                             const char* g_str)

   {

   const BigInt p(p_str);

   const BigInt q = (p - 1) / 2;

   const BigInt g(g_str);

   return std::make_shared<DL_Group_Data>(p, q, g, DL_Group_Source::Builtin);

   }

namespace {

DL_Group_Format pem_label_to_dl_format(const std::string& label)

   {

   if(label == "DH PARAMETERS")

      return DL_Group_Format::PKCS_3;

   else if(label == "DSA PARAMETERS")

      return DL_Group_Format::ANSI_X9_57;

   else if(label == "X942 DH PARAMETERS" || label == "X9.42 DH PARAMETERS")

      return DL_Group_Format::ANSI_X9_42;

   else

      throw Decoding_Error("DL_Group: Invalid PEM label " + label);

   }

}

/*

* DL_Group Constructor

*/

DL_Group::DL_Group(const std::string& str)

   {

   // Either a name or a PEM block, try name first

   m_data = DL_group_info(str);

   if(m_data == nullptr)

      {

      try

         {

         std::string label;

         const std::vector<uint8_t> ber = unlock(PEM_Code::decode(str, label));

         DL_Group_Format format = pem_label_to_dl_format(label);

         m_data = BER_decode_DL_group(ber.data(), ber.size(), format, DL_Group_Source::ExternalSource);

         }

      catch(...) {}

      }

   if(m_data == nullptr)

      throw Invalid_Argument("DL_Group: Unknown group " + str);

   }

namespace {

/*

* Create generator of the q-sized subgroup (DSA style generator)

*/

BigInt make_dsa_generator(const BigInt& p, const BigInt& q)

   {

   BigInt e, r;

   vartime_divide(p - 1, q, e, r);

   if(e == 0 || r > 0)

      throw Invalid_Argument("make_dsa_generator q does not divide p-1");

   for(size_t i = 0; i != PRIME_TABLE_SIZE; ++i)

      {

      // TODO precompute!

      BigInt g = power_mod(BigInt::from_word(PRIMES[i]), e, p);

      if(g > 1)

         return g;

      }

   throw Internal_Error("DL_Group: Couldn't create a suitable generator");

   }

}

/*

* DL_Group Constructor

*/

DL_Group::DL_Group(RandomNumberGenerator& rng,

                   PrimeType type, size_t pbits, size_t qbits)

   {

   if(pbits < 1024)

      throw Invalid_Argument("DL_Group: prime size " + std::to_string(pbits) + " is too small");

   if(type == Strong)

      {

      if(qbits != 0 && qbits != pbits - 1)

         throw Invalid_Argument("Cannot create strong-prime DL_Group with specified q bits");

      const BigInt p = random_safe_prime(rng, pbits);

      const BigInt q = (p - 1) / 2;

      /*

      Always choose a generator that is quadratic reside mod p,

      this forces g to be a generator of the subgroup of size q.

      */

      BigInt g = BigInt::from_word(2);

      if(jacobi(g, p) != 1)

         {

         // prime table does not contain 2

         for(size_t i = 0; i < PRIME_TABLE_SIZE; ++i)

            {

            g = BigInt::from_word(PRIMES[i]);

            if(jacobi(g, p) == 1)

               break;

            }

         }

      m_data = std::make_shared<DL_Group_Data>(p, q, g, DL_Group_Source::RandomlyGenerated);

      }

   else if(type == Prime_Subgroup)

      {

      if(qbits == 0)

         qbits = dl_exponent_size(pbits);

      const BigInt q = random_prime(rng, qbits);

      Modular_Reducer mod_2q(2*q);

      BigInt X;

      BigInt p;

      while(p.bits() != pbits || !is_prime(p, rng, 128, true))

         {

         X.randomize(rng, pbits);

         p = X - mod_2q.reduce(X) + 1;

         }

      const BigInt g = make_dsa_generator(p, q);

      m_data = std::make_shared<DL_Group_Data>(p, q, g, DL_Group_Source::RandomlyGenerated);

      }

   else if(type == DSA_Kosherizer)

      {

      if(qbits == 0)

         qbits = ((pbits <= 1024) ? 160 : 256);

      BigInt p, q;

      generate_dsa_primes(rng, p, q, pbits, qbits);

      const BigInt g = make_dsa_generator(p, q);

      m_data = std::make_shared<DL_Group_Data>(p, q, g, DL_Group_Source::RandomlyGenerated);

      }

   else

      {

      throw Invalid_Argument("DL_Group unknown PrimeType");

      }

   }

/*

* DL_Group Constructor

*/

DL_Group::DL_Group(RandomNumberGenerator& rng,

                   const std::vector<uint8_t>& seed,

                   size_t pbits, size_t qbits)

   {

   BigInt p, q;

   if(!generate_dsa_primes(rng, p, q, pbits, qbits, seed))

      throw Invalid_Argument("DL_Group: The seed given does not generate a DSA group");

   BigInt g = make_dsa_generator(p, q);

   m_data = std::make_shared<DL_Group_Data>(p, q, g, DL_Group_Source::RandomlyGenerated);

   }

/*

* DL_Group Constructor

*/

DL_Group::DL_Group(const BigInt& p, const BigInt& g)

   {

   m_data = std::make_shared<DL_Group_Data>(p, BigInt::zero(), g, DL_Group_Source::ExternalSource);

   }

/*

* DL_Group Constructor

*/

DL_Group::DL_Group(const BigInt& p, const BigInt& q, const BigInt& g)

   {

   m_data = std::make_shared<DL_Group_Data>(p, q, g, DL_Group_Source::ExternalSource);

   }

const DL_Group_Data& DL_Group::data() const

   {

   if(m_data)

      return *m_data;

   throw Invalid_State("DL_Group uninitialized");

   }

bool DL_Group::verify_public_element(const BigInt& y) const

   {

   const BigInt& p = get_p();

   const BigInt& q = get_q();

   if(y <= 1 || y >= p)

      return false;

   if(q.is_zero() == false)

      {

      if(data().power_b_p_vartime(y, q) != 1)

         return false;

      }

   return true;

   }

bool DL_Group::verify_element_pair(const BigInt& y, const BigInt& x) const

   {

   const BigInt& p = get_p();

   if(y <= 1 || y >= p || x <= 1 || x >= p)

      return false;

   if(y != this->power_g_p(x))

      return false;

   return true;

   }

/*

* Verify the parameters

*/

bool DL_Group::verify_group(RandomNumberGenerator& rng,

                            bool strong) const

   {

   const bool from_builtin = (source() == DL_Group_Source::Builtin);

   if(!strong && from_builtin)

      return true;

   const BigInt& p = get_p();

   const BigInt& q = get_q();

   const BigInt& g = get_g();

   if(g < 2 || p < 3 || q < 0)

      return false;

   const size_t test_prob = 128;

   const bool is_randomly_generated = (source() != DL_Group_Source::ExternalSource);

   if(!is_prime(p, rng, test_prob, is_randomly_generated))

      {

      return false;

      }

   if(q != 0)

      {

      if((p - 1) % q != 0)

         {

         return false;

         }

      if(data().power_g_p_vartime(q) != 1)

         {

         return false;

         }

      if(!is_prime(q, rng, test_prob, is_randomly_generated))

         {

         return false;

         }

      }

   else

      {

      if(!from_builtin && !is_randomly_generated)

         {

         // If we got this p,g from some unknown source, try to verify

         // that the group order is not too absurdly small.

         const size_t upper_bound = strong ? 1000 : 100;

         for(size_t i = 2; i != upper_bound; ++i)

            {

            if(data().power_g_p_vartime(BigInt::from_word(i)) == 1)

               {

               return false;

               }

            }

         }

      }

   return true;

   }

/*

* Return the prime

*/

const BigInt& DL_Group::get_p() const

   {

   return data().p();

   }

/*

* Return the generator

*/

const BigInt& DL_Group::get_g() const

   {

   return data().g();

   }

/*

* Return the subgroup

*/

const BigInt& DL_Group::get_q() const

   {

   return data().q();

   }

std::shared_ptr<const Montgomery_Params> DL_Group::monty_params_p() const

   {

   return data().monty_params_p();

   }

size_t DL_Group::p_bits() const

   {

   return data().p_bits();

   }

size_t DL_Group::p_bytes() const

   {

   return data().p_bytes();

   }

size_t DL_Group::q_bits() const

   {

   data().assert_q_is_set("q_bits");

   return data().q_bits();

   }

size_t DL_Group::q_bytes() const

   {

   data().assert_q_is_set("q_bytes");

   return data().q_bytes();

   }

size_t DL_Group::estimated_strength() const

   {

   return data().estimated_strength();

   }

size_t DL_Group::exponent_bits() const

   {

   return data().exponent_bits();

   }

BigInt DL_Group::inverse_mod_p(const BigInt& x) const

   {

   // precompute??

   return inverse_mod(x, get_p());

   }

BigInt DL_Group::mod_p(const BigInt& x) const

   {

   return data().mod_p(x);

   }

BigInt DL_Group::multiply_mod_p(const BigInt& x, const BigInt& y) const

   {

   return data().multiply_mod_p(x, y);

   }

BigInt DL_Group::inverse_mod_q(const BigInt& x) const

   {

   data().assert_q_is_set("inverse_mod_q");

   // precompute??

   return inverse_mod(x, get_q());

   }

BigInt DL_Group::mod_q(const BigInt& x) const

   {

   data().assert_q_is_set("mod_q");

   return data().mod_q(x);

   }

BigInt DL_Group::multiply_mod_q(const BigInt& x, const BigInt& y) const

   {

   data().assert_q_is_set("multiply_mod_q");

   return data().multiply_mod_q(x, y);

   }

BigInt DL_Group::multiply_mod_q(const BigInt& x, const BigInt& y, const BigInt& z) const

   {

   data().assert_q_is_set("multiply_mod_q");

   return data().multiply_mod_q(data().multiply_mod_q(x, y), z);

   }

BigInt DL_Group::square_mod_q(const BigInt& x) const

   {

   data().assert_q_is_set("square_mod_q");

   return data().square_mod_q(x);

   }

BigInt DL_Group::multi_exponentiate(const BigInt& x, const BigInt& y, const BigInt& z) const

   {

   return monty_multi_exp(data().monty_params_p(), get_g(), x, y, z);

   }

BigInt DL_Group::power_g_p(const BigInt& x) const

   {

   return data().power_g_p(x, x.bits());

   }

BigInt DL_Group::power_g_p(const BigInt& x, size_t max_x_bits) const

   {

   return data().power_g_p(x, max_x_bits);

   }

BigInt DL_Group::power_b_p(const BigInt& b, const BigInt& x, size_t max_x_bits) const

   {

   return data().power_b_p(b, x, max_x_bits);

   }

DL_Group_Source DL_Group::source() const

   {

   return data().source();

   }

/*

* DER encode the parameters

*/

std::vector<uint8_t> DL_Group::DER_encode(DL_Group_Format format) const

   {

   if(get_q().is_zero() && (format != DL_Group_Format::PKCS_3))

      throw Encoding_Error("Cannot encode DL_Group in ANSI formats when q param is missing");

   std::vector<uint8_t> output;

   DER_Encoder der(output);

   if(format == DL_Group_Format::ANSI_X9_57)

      {

      der.start_sequence()

            .encode(get_p())

            .encode(get_q())

            .encode(get_g())

         .end_cons();

      }

   else if(format == DL_Group_Format::ANSI_X9_42)

      {

      der.start_sequence()

            .encode(get_p())

            .encode(get_g())

            .encode(get_q())

         .end_cons();

      }

   else if(format == DL_Group_Format::PKCS_3)

      {

      der.start_sequence()

            .encode(get_p())

            .encode(get_g())

         .end_cons();

      }

   else

      throw Invalid_Argument("Unknown DL_Group encoding");

   return output;

   }

/*

* PEM encode the parameters

*/

std::string DL_Group::PEM_encode(DL_Group_Format format) const

   {

   const std::vector<uint8_t> encoding = DER_encode(format);

   if(format == DL_Group_Format::PKCS_3)

      return PEM_Code::encode(encoding, "DH PARAMETERS");

   else if(format == DL_Group_Format::ANSI_X9_57)

      return PEM_Code::encode(encoding, "DSA PARAMETERS");

   else if(format == DL_Group_Format::ANSI_X9_42)

      return PEM_Code::encode(encoding, "X9.42 DH PARAMETERS");

   else

      throw Invalid_Argument("Unknown DL_Group encoding");

   }

DL_Group::DL_Group(const uint8_t ber[], size_t ber_len, DL_Group_Format format)

   {

   m_data = BER_decode_DL_group(ber, ber_len, format, DL_Group_Source::ExternalSource);

   }

void DL_Group::BER_decode(const std::vector<uint8_t>& ber, DL_Group_Format format)

   {

   m_data = BER_decode_DL_group(ber.data(), ber.size(), format, DL_Group_Source::ExternalSource);

   }

//static

DL_Group DL_Group::DL_Group_from_PEM(const std::string& pem)

   {

   std::string label;

   const std::vector<uint8_t> ber = unlock(PEM_Code::decode(pem, label));

   DL_Group_Format format = pem_label_to_dl_format(label);

   return DL_Group(ber, format);

   }

}