/*

* CBC Mode

* (C) 1999-2007,2013,2017 Jack Lloyd

* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity

* (C) 2018 Ribose Inc

*

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

*/

#include <botan/internal/cbc.h>

#include <botan/internal/mode_pad.h>

#include <botan/internal/rounding.h>

namespace Botan {

CBC_Mode::CBC_Mode(BlockCipher* cipher, BlockCipherModePaddingMethod* padding) :

   m_cipher(cipher),

   m_padding(padding),

   m_block_size(cipher->block_size())

   {

   if(m_padding && !m_padding->valid_blocksize(m_block_size))

      throw Invalid_Argument("Padding " + m_padding->name() +

                             " cannot be used with " +

                             cipher->name() + "/CBC");

   }

void CBC_Mode::clear()

   {

   m_cipher->clear();

   reset();

   }

void CBC_Mode::reset()

   {

   m_state.clear();

   }

std::string CBC_Mode::name() const

   {

   if(m_padding)

      return cipher().name() + "/CBC/" + padding().name();

   else

      return cipher().name() + "/CBC/CTS";

   }

size_t CBC_Mode::update_granularity() const

   {

   return cipher().parallel_bytes();

   }

Key_Length_Specification CBC_Mode::key_spec() const

   {

   return cipher().key_spec();

   }

size_t CBC_Mode::default_nonce_length() const

   {

   return block_size();

   }

bool CBC_Mode::valid_nonce_length(size_t n) const

   {

   return (n == 0 || n == block_size());

   }

void CBC_Mode::key_schedule(const uint8_t key[], size_t length)

   {

   m_cipher->set_key(key, length);

   m_state.clear();

   }

void CBC_Mode::start_msg(const uint8_t nonce[], size_t nonce_len)

   {

   if(!valid_nonce_length(nonce_len))

      throw Invalid_IV_Length(name(), nonce_len);

   /*

   * A nonce of zero length means carry the last ciphertext value over

   * as the new IV, as unfortunately some protocols require this. If

   * this is the first message then we use an IV of all zeros.

   */

   if(nonce_len)

      m_state.assign(nonce, nonce + nonce_len);

   else if(m_state.empty())

      m_state.resize(m_cipher->block_size());

   // else leave the state alone

   }

size_t CBC_Encryption::minimum_final_size() const

   {

   return 0;

   }

size_t CBC_Encryption::output_length(size_t input_length) const

   {

   if(input_length == 0)

      return block_size();

   else

      return round_up(input_length, block_size());

   }

size_t CBC_Encryption::process(uint8_t buf[], size_t sz)

   {

   BOTAN_STATE_CHECK(state().empty() == false);

   const size_t BS = block_size();

   BOTAN_ASSERT(sz % BS == 0, "CBC input is full blocks");

   const size_t blocks = sz / BS;

   if(blocks > 0)

      {

      xor_buf(&buf[0], state_ptr(), BS);

      cipher().encrypt(&buf[0]);

      for(size_t i = 1; i != blocks; ++i)

         {

         xor_buf(&buf[BS*i], &buf[BS*(i-1)], BS);

         cipher().encrypt(&buf[BS*i]);

         }

      state().assign(&buf[BS*(blocks-1)], &buf[BS*blocks]);

      }

   return sz;

   }

void CBC_Encryption::finish(secure_vector<uint8_t>& buffer, size_t offset)

   {

   BOTAN_STATE_CHECK(state().empty() == false);

   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");

   const size_t BS = block_size();

   const size_t bytes_in_final_block = (buffer.size()-offset) % BS;

   padding().add_padding(buffer, bytes_in_final_block, BS);

   BOTAN_ASSERT_EQUAL(buffer.size() % BS, offset % BS, "Padded to block boundary");

   update(buffer, offset);

   }

bool CTS_Encryption::valid_nonce_length(size_t n) const

   {

   return (n == block_size());

   }

size_t CTS_Encryption::minimum_final_size() const

   {

   return block_size() + 1;

   }

size_t CTS_Encryption::output_length(size_t input_length) const

   {

   return input_length; // no ciphertext expansion in CTS

   }

void CTS_Encryption::finish(secure_vector<uint8_t>& buffer, size_t offset)

   {

   BOTAN_STATE_CHECK(state().empty() == false);

   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");

   uint8_t* buf = buffer.data() + offset;

   const size_t sz = buffer.size() - offset;

   const size_t BS = block_size();

   if(sz < BS + 1)

      throw Encoding_Error(name() + ": insufficient data to encrypt");

   if(sz % BS == 0)

      {

      update(buffer, offset);

      // swap last two blocks

      for(size_t i = 0; i != BS; ++i)

         std::swap(buffer[buffer.size()-BS+i], buffer[buffer.size()-2*BS+i]);

      }

   else

      {

      const size_t full_blocks = ((sz / BS) - 1) * BS;

      const size_t final_bytes = sz - full_blocks;

      BOTAN_ASSERT(final_bytes > BS && final_bytes < 2*BS, "Left over size in expected range");

      secure_vector<uint8_t> last(buf + full_blocks, buf + full_blocks + final_bytes);

      buffer.resize(full_blocks + offset);

      update(buffer, offset);

      xor_buf(last.data(), state_ptr(), BS);

      cipher().encrypt(last.data());

      for(size_t i = 0; i != final_bytes - BS; ++i)

         {

         last[i] ^= last[i + BS];

         last[i + BS] ^= last[i];

         }

      cipher().encrypt(last.data());

      buffer += last;

      }

   }

size_t CBC_Decryption::output_length(size_t input_length) const

   {

   return input_length; // precise for CTS, worst case otherwise

   }

size_t CBC_Decryption::minimum_final_size() const

   {

   return block_size();

   }

size_t CBC_Decryption::process(uint8_t buf[], size_t sz)

   {

   BOTAN_STATE_CHECK(state().empty() == false);

   const size_t BS = block_size();

   BOTAN_ASSERT(sz % BS == 0, "Input is full blocks");

   size_t blocks = sz / BS;

   while(blocks)

      {

      const size_t to_proc = std::min(BS * blocks, m_tempbuf.size());

      cipher().decrypt_n(buf, m_tempbuf.data(), to_proc / BS);

      xor_buf(m_tempbuf.data(), state_ptr(), BS);

      xor_buf(&m_tempbuf[BS], buf, to_proc - BS);

      copy_mem(state_ptr(), buf + (to_proc - BS), BS);

      copy_mem(buf, m_tempbuf.data(), to_proc);

      buf += to_proc;

      blocks -= to_proc / BS;

      }

   return sz;

   }

void CBC_Decryption::finish(secure_vector<uint8_t>& buffer, size_t offset)

   {

   BOTAN_STATE_CHECK(state().empty() == false);

   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");

   const size_t sz = buffer.size() - offset;

   const size_t BS = block_size();

   if(sz == 0 || sz % BS)

      throw Decoding_Error(name() + ": Ciphertext not a multiple of block size");

   update(buffer, offset);

   const size_t pad_bytes = BS - padding().unpad(&buffer[buffer.size()-BS], BS);

   buffer.resize(buffer.size() - pad_bytes); // remove padding

   if(pad_bytes == 0 && padding().name() != "NoPadding")

      {

      throw Decoding_Error("Invalid CBC padding");

      }

   }

void CBC_Decryption::reset()

   {

   CBC_Mode::reset();

   zeroise(m_tempbuf);

   }

bool CTS_Decryption::valid_nonce_length(size_t n) const

   {

   return (n == block_size());

   }

size_t CTS_Decryption::minimum_final_size() const

   {

   return block_size() + 1;

   }

void CTS_Decryption::finish(secure_vector<uint8_t>& buffer, size_t offset)

   {

   BOTAN_STATE_CHECK(state().empty() == false);

   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");

   const size_t sz = buffer.size() - offset;

   uint8_t* buf = buffer.data() + offset;

   const size_t BS = block_size();

   if(sz < BS + 1)

      throw Encoding_Error(name() + ": insufficient data to decrypt");

   if(sz % BS == 0)

      {

      // swap last two blocks

      for(size_t i = 0; i != BS; ++i)

         std::swap(buffer[buffer.size()-BS+i], buffer[buffer.size()-2*BS+i]);

      update(buffer, offset);

      }

   else

      {

      const size_t full_blocks = ((sz / BS) - 1) * BS;

      const size_t final_bytes = sz - full_blocks;

      BOTAN_ASSERT(final_bytes > BS && final_bytes < 2*BS, "Left over size in expected range");

      secure_vector<uint8_t> last(buf + full_blocks, buf + full_blocks + final_bytes);

      buffer.resize(full_blocks + offset);

      update(buffer, offset);

      cipher().decrypt(last.data());

      xor_buf(last.data(), &last[BS], final_bytes - BS);

      for(size_t i = 0; i != final_bytes - BS; ++i)

         std::swap(last[i], last[i + BS]);

      cipher().decrypt(last.data());

      xor_buf(last.data(), state_ptr(), BS);

      buffer += last;

      }

   }

}