/*
* PKCS#11 ECDH
* (C) 2016 Daniel Neus, Sirrix AG
* (C) 2016 Philipp Weber, Sirrix AG
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/p11_ecdh.h>

#if defined(BOTAN_HAS_ECDH)

#include <botan/internal/p11_mechanism.h>
#include <botan/der_enc.h>
#include <botan/pk_ops.h>
#include <botan/rng.h>

namespace Botan {

namespace PKCS11 {

ECDH_PublicKey PKCS11_ECDH_PublicKey::export_key() const
   {
   return ECDH_PublicKey(domain(), public_point());
   }

ECDH_PrivateKey PKCS11_ECDH_PrivateKey::export_key() const
   {
   auto priv_key = get_attribute_value(AttributeType::Value);

   Null_RNG rng;
   return ECDH_PrivateKey(rng, domain(), BigInt::decode(priv_key));
   }

secure_vector<uint8_t> PKCS11_ECDH_PrivateKey::private_key_bits() const
   {
   return export_key().private_key_bits();
   }

namespace {
class PKCS11_ECDH_KA_Operation final : public PK_Ops::Key_Agreement
   {
   public:
      PKCS11_ECDH_KA_Operation(const PKCS11_EC_PrivateKey& key, const std::string& params)
         : PK_Ops::Key_Agreement(), m_key(key), m_mechanism(MechanismWrapper::create_ecdh_mechanism(params))
         {}

      size_t agreed_value_size() const override { return m_key.domain().get_p_bytes(); }

      /// The encoding in V2.20 was not specified and resulted in different implementations choosing different encodings.
      /// Applications relying only on a V2.20 encoding (e.g. the DER variant) other than the one specified now (raw) may not work with all V2.30 compliant tokens.
      secure_vector<uint8_t> agree(size_t key_len, const uint8_t other_key[], size_t other_key_len, const uint8_t salt[],
                                size_t salt_len) override
         {
         std::vector<uint8_t> der_encoded_other_key;
         if(m_key.point_encoding() == PublicPointEncoding::Der)
            {
            der_encoded_other_key = DER_Encoder().encode(other_key, other_key_len, OCTET_STRING).get_contents_unlocked();
            m_mechanism.set_ecdh_other_key(der_encoded_other_key.data(), der_encoded_other_key.size());
            }
         else
            {
            m_mechanism.set_ecdh_other_key(other_key, other_key_len);
            }

         if(salt != nullptr && salt_len > 0)
            {
            m_mechanism.set_ecdh_salt(salt, salt_len);
            }

         ObjectHandle secret_handle = 0;
         AttributeContainer attributes;
         attributes.add_bool(AttributeType::Sensitive, false);
         attributes.add_bool(AttributeType::Extractable, true);
         attributes.add_numeric(AttributeType::Class, static_cast< CK_OBJECT_CLASS >(ObjectClass::SecretKey));
         attributes.add_numeric(AttributeType::KeyType, static_cast< CK_KEY_TYPE >(KeyType::GenericSecret));
         attributes.add_numeric(AttributeType::ValueLen, static_cast< CK_ULONG >(key_len));
         m_key.module()->C_DeriveKey(m_key.session().handle(), m_mechanism.data(), m_key.handle(), attributes.data(),
                                     attributes.count(), &secret_handle);

         Object secret_object(m_key.session(), secret_handle);
         secure_vector<uint8_t> secret = secret_object.get_attribute_value(AttributeType::Value);
         if(secret.size() < key_len)
            {
            throw PKCS11_Error("ECDH key derivation secret length is too short");
            }
         secret.resize(key_len);
         return secret;
         }

   private:
      const PKCS11_EC_PrivateKey& m_key;
      MechanismWrapper m_mechanism;
   };

}

std::unique_ptr<PK_Ops::Key_Agreement>
PKCS11_ECDH_PrivateKey::create_key_agreement_op(RandomNumberGenerator&,
                                                const std::string& params,
                                                const std::string& /*provider*/) const
   {
   return std::unique_ptr<PK_Ops::Key_Agreement>(new PKCS11_ECDH_KA_Operation(*this, params));
   }

PKCS11_ECDH_KeyPair generate_ecdh_keypair(Session& session, const EC_PublicKeyGenerationProperties& pub_props,
      const EC_PrivateKeyGenerationProperties& priv_props)
   {
   ObjectHandle pub_key_handle = 0;
   ObjectHandle priv_key_handle = 0;

   Mechanism mechanism = { static_cast< CK_MECHANISM_TYPE >(MechanismType::EcKeyPairGen), nullptr, 0 };

   session.module()->C_GenerateKeyPair(session.handle(), &mechanism,
                                       pub_props.data(), pub_props.count(), priv_props.data(), priv_props.count(),
                                       &pub_key_handle, &priv_key_handle);

   return std::make_pair(PKCS11_ECDH_PublicKey(session, pub_key_handle), PKCS11_ECDH_PrivateKey(session, priv_key_handle));
   }

}
}

#endif
