/*
* GnuMP PK operations
* (C) 1999-2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/

#include <botan/internal/gnump_engine.h>
#include <botan/internal/gmp_wrap.h>
#include <gmp.h>

/* GnuMP 5.0 and later have a side-channel resistent powm */
#if defined(HAVE_MPZ_POWM_SEC)
   #undef mpz_powm
   #define mpz_powm mpz_powm_sec
#endif

#if defined(BOTAN_HAS_RSA)
  #include <botan/rsa.h>
#endif

#if defined(BOTAN_HAS_DSA)
  #include <botan/dsa.h>
#endif

#if defined(BOTAN_HAS_DIFFIE_HELLMAN)
  #include <botan/dh.h>
#endif

namespace Botan {

namespace {

#if defined(BOTAN_HAS_DIFFIE_HELLMAN)
class GMP_DH_KA_Operation : public PK_Ops::Key_Agreement
   {
   public:
      GMP_DH_KA_Operation(const DH_PrivateKey& dh) :
         x(dh.get_x()), p(dh.group_p()) {}

      secure_vector<byte> agree(const byte w[], size_t w_len)
         {
         GMP_MPZ z(w, w_len);
         mpz_powm(z.value, z.value, x.value, p.value);
         return z.to_bytes();
         }

   private:
      GMP_MPZ x, p;
   };
#endif

#if defined(BOTAN_HAS_DSA)

class GMP_DSA_Signature_Operation : public PK_Ops::Signature
   {
   public:
      GMP_DSA_Signature_Operation(const DSA_PrivateKey& dsa) :
         x(dsa.get_x()),
         p(dsa.group_p()),
         q(dsa.group_q()),
         g(dsa.group_g()),
         q_bits(dsa.group_q().bits()) {}

      size_t message_parts() const { return 2; }
      size_t message_part_size() const { return (q_bits + 7) / 8; }
      size_t max_input_bits() const { return q_bits; }

      secure_vector<byte> sign(const byte msg[], size_t msg_len,
                              RandomNumberGenerator& rng);
   private:
      const GMP_MPZ x, p, q, g;
      size_t q_bits;
   };

secure_vector<byte>
GMP_DSA_Signature_Operation::sign(const byte msg[], size_t msg_len,
                                  RandomNumberGenerator& rng)
   {
   const size_t q_bytes = (q_bits + 7) / 8;

   rng.add_entropy(msg, msg_len);

   BigInt k_bn;
   do
      k_bn.randomize(rng, q_bits);
   while(k_bn >= q.to_bigint());

   GMP_MPZ i(msg, msg_len);
   GMP_MPZ k(k_bn);

   GMP_MPZ r;
   mpz_powm(r.value, g.value, k.value, p.value);
   mpz_mod(r.value, r.value, q.value);

   mpz_invert(k.value, k.value, q.value);

   GMP_MPZ s;
   mpz_mul(s.value, x.value, r.value);
   mpz_add(s.value, s.value, i.value);
   mpz_mul(s.value, s.value, k.value);
   mpz_mod(s.value, s.value, q.value);

   if(mpz_cmp_ui(r.value, 0) == 0 || mpz_cmp_ui(s.value, 0) == 0)
      throw Internal_Error("GMP_DSA_Op::sign: r or s was zero");

   secure_vector<byte> output(2*q_bytes);
   r.encode(&output[0], q_bytes);
   s.encode(&output[q_bytes], q_bytes);
   return output;
   }

class GMP_DSA_Verification_Operation : public PK_Ops::Verification
   {
   public:
      GMP_DSA_Verification_Operation(const DSA_PublicKey& dsa) :
         y(dsa.get_y()),
         p(dsa.group_p()),
         q(dsa.group_q()),
         g(dsa.group_g()),
         q_bits(dsa.group_q().bits()) {}

      size_t message_parts() const { return 2; }
      size_t message_part_size() const { return (q_bits + 7) / 8; }
      size_t max_input_bits() const { return q_bits; }

      bool with_recovery() const { return false; }

      bool verify(const byte msg[], size_t msg_len,
                  const byte sig[], size_t sig_len);
   private:
      const GMP_MPZ y, p, q, g;
      size_t q_bits;
   };

bool GMP_DSA_Verification_Operation::verify(const byte msg[], size_t msg_len,
                                            const byte sig[], size_t sig_len)
   {
   const size_t q_bytes = q.bytes();

   if(sig_len != 2*q_bytes || msg_len > q_bytes)
      return false;

   GMP_MPZ r(sig, q_bytes);
   GMP_MPZ s(sig + q_bytes, q_bytes);
   GMP_MPZ i(msg, msg_len);

   if(mpz_cmp_ui(r.value, 0) <= 0 || mpz_cmp(r.value, q.value) >= 0)
      return false;
   if(mpz_cmp_ui(s.value, 0) <= 0 || mpz_cmp(s.value, q.value) >= 0)
      return false;

   if(mpz_invert(s.value, s.value, q.value) == 0)
      return false;

   GMP_MPZ si;
   mpz_mul(si.value, s.value, i.value);
   mpz_mod(si.value, si.value, q.value);
   mpz_powm(si.value, g.value, si.value, p.value);

   GMP_MPZ sr;
   mpz_mul(sr.value, s.value, r.value);
   mpz_mod(sr.value, sr.value, q.value);
   mpz_powm(sr.value, y.value, sr.value, p.value);

   mpz_mul(si.value, si.value, sr.value);
   mpz_mod(si.value, si.value, p.value);
   mpz_mod(si.value, si.value, q.value);

   if(mpz_cmp(si.value, r.value) == 0)
      return true;
   return false;
   }

#endif

#if defined(BOTAN_HAS_RSA)

class GMP_RSA_Private_Operation : public PK_Ops::Signature,
                                  public PK_Ops::Decryption
   {
   public:
      GMP_RSA_Private_Operation(const RSA_PrivateKey& rsa) :
         mod(rsa.get_n()),
         p(rsa.get_p()),
         q(rsa.get_q()),
         d1(rsa.get_d1()),
         d2(rsa.get_d2()),
         c(rsa.get_c()),
         n_bits(rsa.get_n().bits())
         {}

      size_t max_input_bits() const { return (n_bits - 1); }

      secure_vector<byte> sign(const byte msg[], size_t msg_len,
                              RandomNumberGenerator&)
         {
         BigInt m(msg, msg_len);
         BigInt x = private_op(m);
         return BigInt::encode_1363(x, (n_bits + 7) / 8);
         }

      secure_vector<byte> decrypt(const byte msg[], size_t msg_len)
         {
         BigInt m(msg, msg_len);
         return BigInt::encode_locked(private_op(m));
         }

   private:
      BigInt private_op(const BigInt& m) const;

      GMP_MPZ mod, p, q, d1, d2, c;
      size_t n_bits;
   };

BigInt GMP_RSA_Private_Operation::private_op(const BigInt& m) const
   {
   GMP_MPZ j1, j2, h(m);

   mpz_powm(j1.value, h.value, d1.value, p.value);
   mpz_powm(j2.value, h.value, d2.value, q.value);
   mpz_sub(h.value, j1.value, j2.value);
   mpz_mul(h.value, h.value, c.value);
   mpz_mod(h.value, h.value, p.value);
   mpz_mul(h.value, h.value, q.value);
   mpz_add(h.value, h.value, j2.value);
   return h.to_bigint();
   }

class GMP_RSA_Public_Operation : public PK_Ops::Verification,
                                 public PK_Ops::Encryption
   {
   public:
      GMP_RSA_Public_Operation(const RSA_PublicKey& rsa) :
         n(rsa.get_n()), e(rsa.get_e()), mod(rsa.get_n())
         {}

      size_t max_input_bits() const { return (n.bits() - 1); }
      bool with_recovery() const { return true; }

      secure_vector<byte> encrypt(const byte msg[], size_t msg_len,
                                 RandomNumberGenerator&)
         {
         BigInt m(msg, msg_len);
         return BigInt::encode_1363(public_op(m), n.bytes());
         }

      secure_vector<byte> verify_mr(const byte msg[], size_t msg_len)
         {
         BigInt m(msg, msg_len);
         return BigInt::encode_locked(public_op(m));
         }

   private:
      BigInt public_op(const BigInt& m) const
         {
         if(m >= n)
            throw Invalid_Argument("RSA public op - input is too large");

         GMP_MPZ m_gmp(m);
         mpz_powm(m_gmp.value, m_gmp.value, e.value, mod.value);
         return m_gmp.to_bigint();
         }

      const BigInt& n;
      const GMP_MPZ e, mod;
   };

#endif

}

PK_Ops::Key_Agreement*
GMP_Engine::get_key_agreement_op(const Private_Key& key, RandomNumberGenerator&) const
   {
#if defined(BOTAN_HAS_DIFFIE_HELLMAN)
   if(const DH_PrivateKey* dh = dynamic_cast<const DH_PrivateKey*>(&key))
      return new GMP_DH_KA_Operation(*dh);
#endif

   return nullptr;
   }

PK_Ops::Signature*
GMP_Engine::get_signature_op(const Private_Key& key, RandomNumberGenerator&) const
   {
#if defined(BOTAN_HAS_RSA)
   if(const RSA_PrivateKey* s = dynamic_cast<const RSA_PrivateKey*>(&key))
      return new GMP_RSA_Private_Operation(*s);
#endif

#if defined(BOTAN_HAS_DSA)
   if(const DSA_PrivateKey* s = dynamic_cast<const DSA_PrivateKey*>(&key))
      return new GMP_DSA_Signature_Operation(*s);
#endif

   return nullptr;
   }

PK_Ops::Verification*
GMP_Engine::get_verify_op(const Public_Key& key, RandomNumberGenerator&) const
   {
#if defined(BOTAN_HAS_RSA)
   if(const RSA_PublicKey* s = dynamic_cast<const RSA_PublicKey*>(&key))
      return new GMP_RSA_Public_Operation(*s);
#endif

#if defined(BOTAN_HAS_DSA)
   if(const DSA_PublicKey* s = dynamic_cast<const DSA_PublicKey*>(&key))
      return new GMP_DSA_Verification_Operation(*s);
#endif

   return nullptr;
   }

PK_Ops::Encryption*
GMP_Engine::get_encryption_op(const Public_Key& key, RandomNumberGenerator&) const
   {
#if defined(BOTAN_HAS_RSA)
   if(const RSA_PublicKey* s = dynamic_cast<const RSA_PublicKey*>(&key))
      return new GMP_RSA_Public_Operation(*s);
#endif

   return nullptr;
   }

PK_Ops::Decryption*
GMP_Engine::get_decryption_op(const Private_Key& key, RandomNumberGenerator&) const
   {
#if defined(BOTAN_HAS_RSA)
   if(const RSA_PrivateKey* s = dynamic_cast<const RSA_PrivateKey*>(&key))
      return new GMP_RSA_Private_Operation(*s);
#endif

   return nullptr;
   }

}