/*
* Cipher Modes via CommonCrypto
* (C) 2018 Jose Pereira
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/cipher_mode.h>
#include <botan/internal/rounding.h>
#include <botan/internal/commoncrypto.h>

#include "commoncrypto_utils.h"

#include <limits.h>

namespace Botan {

namespace {

class CommonCrypto_Cipher_Mode final : public Cipher_Mode
   {
   public:
      CommonCrypto_Cipher_Mode(const std::string& name,
                               Cipher_Dir direction,
                               const CommonCryptor_Opts& opts);

      ~CommonCrypto_Cipher_Mode();

      std::string provider() const override { return "commoncrypto"; }
      std::string name() const override { return m_mode_name; }

      void start_msg(const uint8_t nonce[], size_t nonce_len) override;
      size_t process(uint8_t msg[], size_t msg_len) override;
      void finish(secure_vector<uint8_t>& final_block, size_t offset0) override;
      size_t output_length(size_t input_length) const override;
      size_t update_granularity() const override;
      size_t minimum_final_size() const override;
      size_t default_nonce_length() const override;
      bool valid_nonce_length(size_t nonce_len) const override;
      void clear() override;
      void reset() override;
      Key_Length_Specification key_spec() const override;

   private:
      void key_schedule(const uint8_t key[], size_t length) override;

      const std::string m_mode_name;
      Cipher_Dir m_direction;
      CommonCryptor_Opts m_opts;
      CCCryptorRef m_cipher = nullptr;
      bool m_key_set;
      bool m_nonce_set;
   };

CommonCrypto_Cipher_Mode::CommonCrypto_Cipher_Mode(const std::string& name,
      Cipher_Dir direction, const CommonCryptor_Opts& opts) :
   m_mode_name(name),
   m_direction(direction),
   m_opts(opts),
   m_key_set(false),
   m_nonce_set(false)
   {
   }

CommonCrypto_Cipher_Mode::~CommonCrypto_Cipher_Mode()
   {
   if(m_cipher)
      {
      CCCryptorRelease(m_cipher);
      }
   }

void CommonCrypto_Cipher_Mode::start_msg(const uint8_t nonce[], size_t nonce_len)
   {
   verify_key_set(m_key_set);

   if(!valid_nonce_length(nonce_len))
      { throw Invalid_IV_Length(name(), nonce_len); }
   if(nonce_len)
      {
      CCCryptorStatus status = CCCryptorReset(m_cipher, nonce);
      if(status != kCCSuccess)
         {
         throw CommonCrypto_Error("CCCryptorReset on start_msg", status);
         }
      }
   m_nonce_set = true;
   }

size_t CommonCrypto_Cipher_Mode::process(uint8_t msg[], size_t msg_len)
   {
   verify_key_set(m_key_set);
   BOTAN_STATE_CHECK(m_nonce_set);

   if(msg_len == 0)
      { return 0; }
   if(msg_len > INT_MAX)
      { throw Internal_Error("msg_len overflow"); }
   size_t outl = CCCryptorGetOutputLength(m_cipher, msg_len, false);

   secure_vector<uint8_t> out(outl);

   if(m_opts.padding == ccNoPadding && msg_len % m_opts.block_size)
      {
      msg_len = outl;
      }

   CCCryptorStatus status = CCCryptorUpdate(m_cipher, msg, msg_len,
                            out.data(), outl, &outl);
   if(status != kCCSuccess)
      {
      throw CommonCrypto_Error("CCCryptorUpdate", status);
      }
   copy_mem(msg, out.data(), outl);

   return outl;
   }

void CommonCrypto_Cipher_Mode::finish(secure_vector<uint8_t>& buffer,
                                      size_t offset)
   {
   verify_key_set(m_key_set);
   BOTAN_STATE_CHECK(m_nonce_set);

   BOTAN_ASSERT(buffer.size() >= offset, "Offset ok");
   uint8_t* buf = buffer.data() + offset;
   const size_t buf_size = buffer.size() - offset;

   size_t written = process(buf, buf_size);

   size_t outl = CCCryptorGetOutputLength(m_cipher, buf_size - written, true);
   secure_vector<uint8_t> out(outl);

   CCCryptorStatus status = CCCryptorFinal(
                               m_cipher, out.data(), outl, &outl);
   if(status != kCCSuccess)
      {
      throw CommonCrypto_Error("CCCryptorFinal", status);
      }

   size_t new_len = offset + written + outl;
   if(m_opts.padding != ccNoPadding || buffer.size() < new_len)
      {
      buffer.resize(new_len);
      }
   copy_mem(buffer.data() - offset + written, out.data(), outl);
   written += outl;
   }

size_t CommonCrypto_Cipher_Mode::update_granularity() const
   {
   return m_opts.block_size * BOTAN_BLOCK_CIPHER_PAR_MULT;
   }

size_t CommonCrypto_Cipher_Mode::minimum_final_size() const
   {
   if(m_direction == ENCRYPTION)
      return 0;
   else
      return m_opts.block_size;
   }

size_t CommonCrypto_Cipher_Mode::default_nonce_length() const
   {
   return m_opts.block_size;
   }

bool CommonCrypto_Cipher_Mode::valid_nonce_length(size_t nonce_len) const
   {
   return (nonce_len == 0 || nonce_len == m_opts.block_size);
   }

size_t CommonCrypto_Cipher_Mode::output_length(size_t input_length) const
   {
   if(input_length == 0)
      { return m_opts.block_size; }
   else
      { return round_up(input_length, m_opts.block_size); }
   }

void CommonCrypto_Cipher_Mode::clear()
   {
   m_key_set = false;

   if(m_cipher == nullptr)
      {
      return;
      }

   if(m_cipher)
      {
      CCCryptorRelease(m_cipher);
      m_cipher = nullptr;
      }
   }

void CommonCrypto_Cipher_Mode::reset()
   {
   if(m_cipher == nullptr)
      {
      return;
      }

   m_nonce_set = false;

   CCCryptorStatus status = CCCryptorReset(m_cipher, nullptr);
   if(status != kCCSuccess)
      {
      throw CommonCrypto_Error("CCCryptorReset", status);
      }
   }

Key_Length_Specification CommonCrypto_Cipher_Mode::key_spec() const
   {
   return m_opts.key_spec;
   }

void CommonCrypto_Cipher_Mode::key_schedule(const uint8_t key[], size_t length)
   {
   CCCryptorStatus status;
   CCOperation op = m_direction == ENCRYPTION ? kCCEncrypt : kCCDecrypt;
   status = CCCryptorCreateWithMode(op, m_opts.mode, m_opts.algo, m_opts.padding,
                                    nullptr, key, length, nullptr, 0, 0, 0, &m_cipher);
   if(status != kCCSuccess)
      {
      throw CommonCrypto_Error("CCCryptorCreate", status);
      }

   m_key_set = true;
   m_nonce_set = false;
   }
}

Cipher_Mode*
make_commoncrypto_cipher_mode(const std::string& name, Cipher_Dir direction)
   {

   try
      {
      CommonCryptor_Opts opts = commoncrypto_opts_from_algo(name);
      return new CommonCrypto_Cipher_Mode(name, direction, opts);
      }
   catch(CommonCrypto_Error& e)
      {
      return nullptr;
      }
   }
}