/*
* OpenSSL RSA interface
* (C) 2015 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/rsa.h>
#include <botan/internal/pk_utils.h>
#include <functional>
#include <memory>

#include <openssl/rsa.h>
#include <openssl/x509.h>
#include <openssl/err.h>

namespace Botan {

namespace {

std::pair<int, size_t> get_openssl_enc_pad(const std::string& eme)
   {
   if(eme == "Raw")
      return std::make_pair(RSA_NO_PADDING, 0);
   else if(eme == "EME-PKCS1-v1_5")
      return std::make_pair(RSA_PKCS1_PADDING, 11);
   else if(eme == "EME1(SHA-1)")
      return std::make_pair(RSA_PKCS1_OAEP_PADDING, 41);
   else
      throw Lookup_Error("OpenSSL RSA does not support EME " + eme);
   }

class OpenSSL_Error : public Exception
   {
   public:
      OpenSSL_Error(const std::string& what) :
         Exception(what + " failed: " + ERR_error_string(ERR_get_error(), nullptr)) {}
   };

class OpenSSL_RSA_Encryption_Operation : public PK_Ops::Encryption
   {
   public:
      typedef RSA_PublicKey Key_Type;

      static OpenSSL_RSA_Encryption_Operation* make(const Spec& spec)
         {
         try
            {
            if(auto* key = dynamic_cast<const RSA_PublicKey*>(&spec.key()))
               {
               auto pad_info = get_openssl_enc_pad(spec.padding());
               return new OpenSSL_RSA_Encryption_Operation(*key, pad_info.first, pad_info.second);
               }
            }
         catch(...) {}

         return nullptr;
         }

      OpenSSL_RSA_Encryption_Operation(const RSA_PublicKey& rsa, int pad, size_t pad_overhead) :
         m_openssl_rsa(nullptr, ::RSA_free), m_padding(pad)
         {
         const std::vector<byte> der = rsa.x509_subject_public_key();
         const byte* der_ptr = &der[0];
         m_openssl_rsa.reset(d2i_RSAPublicKey(nullptr, &der_ptr, der.size()));
         if(!m_openssl_rsa)
            throw OpenSSL_Error("d2i_RSAPublicKey");

         m_bits = 8 * (RSA_size(m_openssl_rsa.get()) - pad_overhead);
         }

      size_t max_input_bits() const override { return m_bits; };

      secure_vector<byte> encrypt(const byte msg[], size_t msg_len,
                                  RandomNumberGenerator&) override
         {

         secure_vector<byte> buf(::RSA_size(m_openssl_rsa.get()));
         int rc = ::RSA_public_encrypt(msg_len, msg, &buf[0], m_openssl_rsa.get(), m_padding);
         if(rc < 0)
            throw OpenSSL_Error("RSA_public_encrypt");
         return buf;
         }

   private:
      std::unique_ptr<RSA, std::function<void (RSA*)>> m_openssl_rsa;
      size_t m_bits = 0;
      int m_padding = 0;
   };

class OpenSSL_RSA_Decryption_Operation : public PK_Ops::Decryption
   {
   public:
      typedef RSA_PrivateKey Key_Type;

      static OpenSSL_RSA_Decryption_Operation* make(const Spec& spec)
         {
         try
            {
            if(auto* key = dynamic_cast<const RSA_PrivateKey*>(&spec.key()))
               {
               auto pad_info = get_openssl_enc_pad(spec.padding());
               return new OpenSSL_RSA_Decryption_Operation(*key, pad_info.first);
               }
            }
         catch(...) {}

         return nullptr;
         }

      OpenSSL_RSA_Decryption_Operation(const RSA_PrivateKey& rsa, int pad) :
         m_openssl_rsa(nullptr, ::RSA_free), m_padding(pad)
         {
         const secure_vector<byte> der = rsa.pkcs8_private_key();
         const byte* der_ptr = &der[0];
         m_openssl_rsa.reset(d2i_RSAPrivateKey(nullptr, &der_ptr, der.size()));
         if(!m_openssl_rsa)
            throw OpenSSL_Error("d2i_RSAPrivateKey");

         m_bits = 8 * RSA_size(m_openssl_rsa.get());
         }

      size_t max_input_bits() const override { return m_bits; };

      secure_vector<byte> decrypt(const byte msg[], size_t msg_len) override
         {
         secure_vector<byte> buf(::RSA_size(m_openssl_rsa.get()));
         int rc = ::RSA_private_decrypt(msg_len, msg, &buf[0], m_openssl_rsa.get(), m_padding);
         if(rc < 0 || static_cast<size_t>(rc) > buf.size())
            throw OpenSSL_Error("RSA_private_decrypt");
         buf.resize(rc);
         return buf;
         }

   private:
      std::unique_ptr<RSA, std::function<void (RSA*)>> m_openssl_rsa;
      size_t m_bits = 0;
      int m_padding = 0;
   };

BOTAN_REGISTER_TYPE(PK_Ops::Encryption, OpenSSL_RSA_Encryption_Operation, "RSA",
                    OpenSSL_RSA_Encryption_Operation::make, "openssl", 255);
BOTAN_REGISTER_TYPE(PK_Ops::Decryption, OpenSSL_RSA_Decryption_Operation, "RSA",
                    OpenSSL_RSA_Decryption_Operation::make, "openssl", 255);

}

}