text: /*
  * 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(std::unique_ptr<BlockCipher> cipher,
                     std::unique_ptr<BlockCipherModePaddingMethod> padding) :
     m_cipher(std::move(cipher)),
     m_padding(std::move(padding)),
     m_block_size(m_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;
        }
     }
  
  }
  