/*

* SM2 Signatures

* (C) 2017,2018 Ribose Inc

* (C) 2018 Jack Lloyd

*

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

*/

#include <botan/sm2.h>

#include <botan/internal/pk_ops_impl.h>

#include <botan/internal/point_mul.h>

#include <botan/internal/loadstor.h>

#include <botan/numthry.h>

#include <botan/internal/keypair.h>

#include <botan/hash.h>

#include <botan/internal/parsing.h>

namespace Botan {

std::string SM2_PublicKey::algo_name() const

   {

   return "SM2";

   }

std::unique_ptr<Public_Key> SM2_PrivateKey::public_key() const

   {

   return std::make_unique<SM2_Signature_PublicKey>(domain(), public_point());

   }

bool SM2_PrivateKey::check_key(RandomNumberGenerator& rng,

                               bool strong) const

   {

   if(!public_point().on_the_curve())

      return false;

   if(!strong)

      return true;

   return KeyPair::signature_consistency_check(rng, *this, "user@example.com,SM3");

   }

SM2_PrivateKey::SM2_PrivateKey(const AlgorithmIdentifier& alg_id,

                               std::span<const uint8_t> key_bits) :

   EC_PrivateKey(alg_id, key_bits)

   {

   m_da_inv = domain().inverse_mod_order(m_private_key + 1);

   }

Unexecuted instantiation: Botan::SM2_PrivateKey::SM2_PrivateKey(Botan::AlgorithmIdentifier const&, std::__1::span<unsigned char const, 18446744073709551615ul>)

Unexecuted instantiation: Botan::SM2_PrivateKey::SM2_PrivateKey(Botan::AlgorithmIdentifier const&, std::__1::span<unsigned char const, 18446744073709551615ul>)

SM2_PrivateKey::SM2_PrivateKey(RandomNumberGenerator& rng,

                               const EC_Group& domain,

                               const BigInt& x) :

   EC_PrivateKey(rng, domain, x)

   {

   m_da_inv = domain.inverse_mod_order(m_private_key + 1);

   }

Unexecuted instantiation: Botan::SM2_PrivateKey::SM2_PrivateKey(Botan::RandomNumberGenerator&, Botan::EC_Group const&, Botan::BigInt const&)

Unexecuted instantiation: Botan::SM2_PrivateKey::SM2_PrivateKey(Botan::RandomNumberGenerator&, Botan::EC_Group const&, Botan::BigInt const&)

std::vector<uint8_t> sm2_compute_za(HashFunction& hash,

                                    std::string_view user_id,

                                    const EC_Group& domain,

                                    const EC_Point& pubkey)

   {

   if(user_id.size() >= 8192)

      throw Invalid_Argument("SM2 user id too long to represent");

   const uint16_t uid_len = static_cast<uint16_t>(8 * user_id.size());

   hash.update(get_byte<0>(uid_len));

   hash.update(get_byte<1>(uid_len));

   hash.update(user_id);

   const size_t p_bytes = domain.get_p_bytes();

   hash.update(BigInt::encode_1363(domain.get_a(), p_bytes));

   hash.update(BigInt::encode_1363(domain.get_b(), p_bytes));

   hash.update(BigInt::encode_1363(domain.get_g_x(), p_bytes));

   hash.update(BigInt::encode_1363(domain.get_g_y(), p_bytes));

   hash.update(BigInt::encode_1363(pubkey.get_affine_x(), p_bytes));

   hash.update(BigInt::encode_1363(pubkey.get_affine_y(), p_bytes));

   std::vector<uint8_t> za(hash.output_length());

   hash.final(za.data());

   return za;

   }

namespace {

/**

* SM2 signature operation

*/

class SM2_Signature_Operation final : public PK_Ops::Signature

   {

   public:

      SM2_Signature_Operation(const SM2_PrivateKey& sm2,

                              std::string_view ident,

                              std::string_view hash) :

         m_group(sm2.domain()),

         m_x(sm2.private_value()),

         m_da_inv(sm2.get_da_inv())

         {

         if(hash == "Raw")

            {

            // m_hash is null, m_za is empty

            }

         else

            {

            m_hash = HashFunction::create_or_throw(hash);

            // ZA=H256(ENTLA || IDA || a || b || xG || yG || xA || yA)

            m_za = sm2_compute_za(*m_hash, ident, m_group, sm2.public_point());

            m_hash->update(m_za);

            }

         }

      size_t signature_length() const override { return 2*m_group.get_order_bytes(); }

      void update(const uint8_t msg[], size_t msg_len) override

         {

         if(m_hash)

            {

            m_hash->update(msg, msg_len);

            }

         else

            {

            m_digest.insert(m_digest.end(), msg, msg + msg_len);

            }

         }

      secure_vector<uint8_t> sign(RandomNumberGenerator& rng) override;

      std::string hash_function() const override { return m_hash->name(); }

   private:

      const EC_Group m_group;

      const BigInt& m_x;

      const BigInt& m_da_inv;

      std::vector<uint8_t> m_za;

      secure_vector<uint8_t> m_digest;

      std::unique_ptr<HashFunction> m_hash;

      std::vector<BigInt> m_ws;

   };

secure_vector<uint8_t>

SM2_Signature_Operation::sign(RandomNumberGenerator& rng)

   {

   BigInt e;

   if(m_hash)

      {

      e = BigInt::decode(m_hash->final());

      // prepend ZA for next signature if any

      m_hash->update(m_za);

      }

   else

      {

      e = BigInt::decode(m_digest);

      m_digest.clear();

      }

   const BigInt k = m_group.random_scalar(rng);

   const BigInt r = m_group.mod_order(

      m_group.blinded_base_point_multiply_x(k, rng, m_ws) + e);

   const BigInt s = m_group.multiply_mod_order(m_da_inv, m_group.mod_order(k - r*m_x));

   return BigInt::encode_fixed_length_int_pair(r, s, m_group.get_order().bytes());

   }

/**

* SM2 verification operation

*/

class SM2_Verification_Operation final : public PK_Ops::Verification

   {

   public:

      SM2_Verification_Operation(const SM2_PublicKey& sm2,

                                 std::string_view ident,

                                 std::string_view hash) :

         m_group(sm2.domain()),

         m_gy_mul(m_group.get_base_point(), sm2.public_point())

         {

         if(hash == "Raw")

            {

            // m_hash is null, m_za is empty

            }

         else

            {

            m_hash = HashFunction::create_or_throw(hash);

            // ZA=H256(ENTLA || IDA || a || b || xG || yG || xA || yA)

            m_za = sm2_compute_za(*m_hash, ident, m_group, sm2.public_point());

            m_hash->update(m_za);

            }

         }

      void update(const uint8_t msg[], size_t msg_len) override

         {

         if(m_hash)

            {

            m_hash->update(msg, msg_len);

            }

         else

            {

            m_digest.insert(m_digest.end(), msg, msg + msg_len);

            }

         }

      bool is_valid_signature(const uint8_t sig[], size_t sig_len) override;

      std::string hash_function() const override { return m_hash->name(); }

   private:

      const EC_Group m_group;

      const EC_Point_Multi_Point_Precompute m_gy_mul;

      secure_vector<uint8_t> m_digest;

      std::vector<uint8_t> m_za;

      std::unique_ptr<HashFunction> m_hash;

   };

bool SM2_Verification_Operation::is_valid_signature(const uint8_t sig[], size_t sig_len)

   {

   BigInt e;

   if(m_hash)

      {

      e = BigInt::decode(m_hash->final());

      // prepend ZA for next signature if any

      m_hash->update(m_za);

      }

   else

      {

      e = BigInt::decode(m_digest);

      m_digest.clear();

      }

   if(sig_len != m_group.get_order().bytes()*2)

      return false;

   const BigInt r(sig, sig_len / 2);

   const BigInt s(sig + sig_len / 2, sig_len / 2);

   if(r <= 0 || r >= m_group.get_order() || s <= 0 || s >= m_group.get_order())

      return false;

   const BigInt t = m_group.mod_order(r + s);

   if(t == 0)

      return false;

   const EC_Point R = m_gy_mul.multi_exp(s, t);

   // ???

   if(R.is_zero())

      return false;

   return (m_group.mod_order(R.get_affine_x() + e) == r);

   }

void parse_sm2_param_string(std::string_view params,

                            std::string& userid,

                            std::string& hash)

   {

   // GM/T 0009-2012 specifies this as the default userid

   const std::string default_userid = "1234567812345678";

   // defaults:

   userid = default_userid;

   hash = "SM3";

   /*

   * SM2 parameters have the following possible formats:

   * Ident [since 2.2.0]

   * Ident,Hash [since 2.3.0]

   */

   auto comma = params.find(',');

   if(comma == std::string::npos)

      {

      userid = params;

      }

   else

      {

      userid = params.substr(0, comma);

      hash = params.substr(comma+1, std::string::npos);

      }

   }

}

std::unique_ptr<PK_Ops::Verification>

SM2_PublicKey::create_verification_op(std::string_view params,

                                      std::string_view provider) const

   {

   if(provider == "base" || provider.empty())

      {

      std::string userid, hash;

      parse_sm2_param_string(params, userid, hash);

      return std::make_unique<SM2_Verification_Operation>(*this, userid, hash);

      }

   throw Provider_Not_Found(algo_name(), provider);

   }

std::unique_ptr<PK_Ops::Signature>

SM2_PrivateKey::create_signature_op(RandomNumberGenerator& /*rng*/,

                                    std::string_view params,

                                    std::string_view provider) const

   {

   if(provider == "base" || provider.empty())

      {

      std::string userid, hash;

      parse_sm2_param_string(params, userid, hash);

      return std::make_unique<SM2_Signature_Operation>(*this, userid, hash);

      }

   throw Provider_Not_Found(algo_name(), provider);

   }

}