Coverage Report

Created: 2020-02-14 15:38

/src/botan/src/lib/modes/cbc/cbc.cpp
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/*
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* CBC Mode
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* (C) 1999-2007,2013,2017 Jack Lloyd
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* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
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* (C) 2018 Ribose Inc
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*
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* Botan is released under the Simplified BSD License (see license.txt)
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*/
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#include <botan/cbc.h>
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#include <botan/mode_pad.h>
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#include <botan/internal/rounding.h>
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namespace Botan {
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CBC_Mode::CBC_Mode(BlockCipher* cipher, BlockCipherModePaddingMethod* padding) :
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   m_cipher(cipher),
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   m_padding(padding),
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   m_block_size(cipher->block_size())
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   {
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   if(m_padding && !m_padding->valid_blocksize(m_block_size))
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      throw Invalid_Argument("Padding " + m_padding->name() +
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                             " cannot be used with " +
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                             cipher->name() + "/CBC");
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   }
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void CBC_Mode::clear()
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   {
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   m_cipher->clear();
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   reset();
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   }
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void CBC_Mode::reset()
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   {
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   m_state.clear();
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   }
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std::string CBC_Mode::name() const
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   {
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   if(m_padding)
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      return cipher().name() + "/CBC/" + padding().name();
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   else
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      return cipher().name() + "/CBC/CTS";
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   }
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size_t CBC_Mode::update_granularity() const
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   {
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   return cipher().parallel_bytes();
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   }
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Key_Length_Specification CBC_Mode::key_spec() const
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   {
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   return cipher().key_spec();
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   }
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size_t CBC_Mode::default_nonce_length() const
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   {
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   return block_size();
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   }
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bool CBC_Mode::valid_nonce_length(size_t n) const
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   {
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   return (n == 0 || n == block_size());
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   }
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void CBC_Mode::key_schedule(const uint8_t key[], size_t length)
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   {
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   m_cipher->set_key(key, length);
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   m_state.clear();
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   }
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void CBC_Mode::start_msg(const uint8_t nonce[], size_t nonce_len)
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   {
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   if(!valid_nonce_length(nonce_len))
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      throw Invalid_IV_Length(name(), nonce_len);
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   /*
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   * A nonce of zero length means carry the last ciphertext value over
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   * as the new IV, as unfortunately some protocols require this. If
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   * this is the first message then we use an IV of all zeros.
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   */
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   if(nonce_len)
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      m_state.assign(nonce, nonce + nonce_len);
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   else if(m_state.empty())
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      m_state.resize(m_cipher->block_size());
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   // else leave the state alone
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   }
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size_t CBC_Encryption::minimum_final_size() const
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   {
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   return 0;
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   }
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size_t CBC_Encryption::output_length(size_t input_length) const
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   {
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   if(input_length == 0)
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      return block_size();
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   else
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      return round_up(input_length, block_size());
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   }
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size_t CBC_Encryption::process(uint8_t buf[], size_t sz)
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   {
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   BOTAN_STATE_CHECK(state().empty() == false);
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   const size_t BS = block_size();
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   BOTAN_ASSERT(sz % BS == 0, "CBC input is full blocks");
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   const size_t blocks = sz / BS;
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   if(blocks > 0)
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      {
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      xor_buf(&buf[0], state_ptr(), BS);
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      cipher().encrypt(&buf[0]);
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      for(size_t i = 1; i != blocks; ++i)
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         {
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         xor_buf(&buf[BS*i], &buf[BS*(i-1)], BS);
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         cipher().encrypt(&buf[BS*i]);
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         }
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      state().assign(&buf[BS*(blocks-1)], &buf[BS*blocks]);
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      }
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   return sz;
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   }
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void CBC_Encryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
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   {
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   BOTAN_STATE_CHECK(state().empty() == false);
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   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
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   const size_t BS = block_size();
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   const size_t bytes_in_final_block = (buffer.size()-offset) % BS;
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   padding().add_padding(buffer, bytes_in_final_block, BS);
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   if((buffer.size()-offset) % BS)
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      throw Internal_Error("Did not pad to full block size in " + name());
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   update(buffer, offset);
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   }
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bool CTS_Encryption::valid_nonce_length(size_t n) const
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   {
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   return (n == block_size());
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   }
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size_t CTS_Encryption::minimum_final_size() const
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   {
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   return block_size() + 1;
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   }
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size_t CTS_Encryption::output_length(size_t input_length) const
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   {
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   return input_length; // no ciphertext expansion in CTS
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   }
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void CTS_Encryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
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   {
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   BOTAN_STATE_CHECK(state().empty() == false);
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   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
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   uint8_t* buf = buffer.data() + offset;
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   const size_t sz = buffer.size() - offset;
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   const size_t BS = block_size();
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   if(sz < BS + 1)
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      throw Encoding_Error(name() + ": insufficient data to encrypt");
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   if(sz % BS == 0)
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      {
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      update(buffer, offset);
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      // swap last two blocks
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      for(size_t i = 0; i != BS; ++i)
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         std::swap(buffer[buffer.size()-BS+i], buffer[buffer.size()-2*BS+i]);
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      }
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   else
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      {
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      const size_t full_blocks = ((sz / BS) - 1) * BS;
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      const size_t final_bytes = sz - full_blocks;
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      BOTAN_ASSERT(final_bytes > BS && final_bytes < 2*BS, "Left over size in expected range");
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      secure_vector<uint8_t> last(buf + full_blocks, buf + full_blocks + final_bytes);
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      buffer.resize(full_blocks + offset);
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      update(buffer, offset);
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      xor_buf(last.data(), state_ptr(), BS);
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      cipher().encrypt(last.data());
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      for(size_t i = 0; i != final_bytes - BS; ++i)
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         {
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         last[i] ^= last[i + BS];
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         last[i + BS] ^= last[i];
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         }
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      cipher().encrypt(last.data());
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      buffer += last;
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      }
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   }
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size_t CBC_Decryption::output_length(size_t input_length) const
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   {
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   return input_length; // precise for CTS, worst case otherwise
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   }
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size_t CBC_Decryption::minimum_final_size() const
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   {
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   return block_size();
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   }
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size_t CBC_Decryption::process(uint8_t buf[], size_t sz)
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   {
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   BOTAN_STATE_CHECK(state().empty() == false);
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   const size_t BS = block_size();
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   BOTAN_ASSERT(sz % BS == 0, "Input is full blocks");
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   size_t blocks = sz / BS;
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   while(blocks)
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      {
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      const size_t to_proc = std::min(BS * blocks, m_tempbuf.size());
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      cipher().decrypt_n(buf, m_tempbuf.data(), to_proc / BS);
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      xor_buf(m_tempbuf.data(), state_ptr(), BS);
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      xor_buf(&m_tempbuf[BS], buf, to_proc - BS);
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      copy_mem(state_ptr(), buf + (to_proc - BS), BS);
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      copy_mem(buf, m_tempbuf.data(), to_proc);
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      buf += to_proc;
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      blocks -= to_proc / BS;
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      }
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   return sz;
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   }
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void CBC_Decryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
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   {
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   BOTAN_STATE_CHECK(state().empty() == false);
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   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
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   const size_t sz = buffer.size() - offset;
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   const size_t BS = block_size();
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   if(sz == 0 || sz % BS)
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      throw Decoding_Error(name() + ": Ciphertext not a multiple of block size");
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   update(buffer, offset);
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   const size_t pad_bytes = BS - padding().unpad(&buffer[buffer.size()-BS], BS);
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   buffer.resize(buffer.size() - pad_bytes); // remove padding
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   if(pad_bytes == 0 && padding().name() != "NoPadding")
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      {
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      throw Decoding_Error("Invalid CBC padding");
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      }
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   }
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void CBC_Decryption::reset()
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   {
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   CBC_Mode::reset();
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   zeroise(m_tempbuf);
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   }
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bool CTS_Decryption::valid_nonce_length(size_t n) const
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   {
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   return (n == block_size());
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   }
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size_t CTS_Decryption::minimum_final_size() const
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   {
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   return block_size() + 1;
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   }
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void CTS_Decryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
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   {
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   BOTAN_STATE_CHECK(state().empty() == false);
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   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
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   const size_t sz = buffer.size() - offset;
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   uint8_t* buf = buffer.data() + offset;
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   const size_t BS = block_size();
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   if(sz < BS + 1)
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      throw Encoding_Error(name() + ": insufficient data to decrypt");
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   if(sz % BS == 0)
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      {
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      // swap last two blocks
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      for(size_t i = 0; i != BS; ++i)
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         std::swap(buffer[buffer.size()-BS+i], buffer[buffer.size()-2*BS+i]);
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      update(buffer, offset);
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      }
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   else
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      {
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      const size_t full_blocks = ((sz / BS) - 1) * BS;
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      const size_t final_bytes = sz - full_blocks;
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      BOTAN_ASSERT(final_bytes > BS && final_bytes < 2*BS, "Left over size in expected range");
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      secure_vector<uint8_t> last(buf + full_blocks, buf + full_blocks + final_bytes);
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      buffer.resize(full_blocks + offset);
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      update(buffer, offset);
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      cipher().decrypt(last.data());
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      xor_buf(last.data(), &last[BS], final_bytes - BS);
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      for(size_t i = 0; i != final_bytes - BS; ++i)
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         std::swap(last[i], last[i + BS]);
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      cipher().decrypt(last.data());
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      xor_buf(last.data(), state_ptr(), BS);
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      buffer += last;
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      }
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   }
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}