1 files changed, 299 insertions, 0 deletions
diff --git a/lib/modes/cbc/cbc.cpp b/lib/modes/cbc/cbc.cpp
new file mode 100644
index 000000000..31834bade
--- /dev/null
+++ b/lib/modes/cbc/cbc.cpp
@@ -0,0 +1,299 @@
+/*
+* CBC Mode
+* (C) 1999-2007,2013 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+#include <botan/cbc.h>
+#include <botan/loadstor.h>
+#include <botan/internal/xor_buf.h>
+#include <botan/internal/rounding.h>
+
+namespace Botan {
+
+CBC_Mode::CBC_Mode(BlockCipher* cipher, BlockCipherModePaddingMethod* padding) :
+   m_cipher(cipher),
+   m_padding(padding),
+   m_state(m_cipher->block_size())
+   {
+   if(m_padding && !m_padding->valid_blocksize(cipher->block_size()))
+      throw std::invalid_argument("Padding " + m_padding->name() +
+                                  " cannot be used with " +
+                                  cipher->name() + "/CBC");
+   }
+
+void CBC_Mode::clear()
+   {
+   m_cipher->clear();
+   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 cipher().block_size();
+   }
+
+bool CBC_Mode::valid_nonce_length(size_t n) const
+   {
+   return (n == 0 || n == cipher().block_size());
+   }
+
+void CBC_Mode::key_schedule(const byte key[], size_t length)
+   {
+   m_cipher->set_key(key, length);
+   }
+
+secure_vector<byte> CBC_Mode::start(const byte 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);
+
+   return secure_vector<byte>();
+   }
+
+size_t CBC_Encryption::minimum_final_size() const
+   {
+   return 0;
+   }
+
+size_t CBC_Encryption::output_length(size_t input_length) const
+   {
+   return round_up(input_length, cipher().block_size());
+   }
+
+void CBC_Encryption::update(secure_vector<byte>& buffer, size_t offset)
+   {
+   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
+   const size_t sz = buffer.size() - offset;
+   byte* buf = &buffer[offset];
+
+   const size_t BS = cipher().block_size();
+
+   BOTAN_ASSERT(sz % BS == 0, "CBC input is full blocks");
+   const size_t blocks = sz / BS;
+
+   if(blocks)
+      {
+      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]);
+      }
+   }
+
+void CBC_Encryption::finish(secure_vector<byte>& buffer, size_t offset)
+   {
+   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
+
+   const size_t BS = cipher().block_size();
+
+   const size_t bytes_in_final_block = (buffer.size()-offset) % BS;
+
+   padding().add_padding(buffer, bytes_in_final_block, BS);
+
+   if((buffer.size()-offset) % BS)
+      throw std::runtime_error("Did not pad to full block size in " + name());
+
+   update(buffer, offset);
+   }
+
+bool CTS_Encryption::valid_nonce_length(size_t n) const
+   {
+   return (n == cipher().block_size());
+   }
+
+size_t CTS_Encryption::minimum_final_size() const
+   {
+   return cipher().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<byte>& buffer, size_t offset)
+   {
+   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
+   byte* buf = &buffer[offset];
+   const size_t sz = buffer.size() - offset;
+
+   const size_t BS = cipher().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<byte> last(buf + full_blocks, buf + full_blocks + final_bytes);
+      buffer.resize(full_blocks + offset);
+      update(buffer, offset);
+
+      xor_buf(&last[0], state_ptr(), BS);
+      cipher().encrypt(&last[0]);
+
+      for(size_t i = 0; i != final_bytes - BS; ++i)
+         {
+         std::swap(last[i], last[i + BS]);
+         last[i] ^= last[i + BS];
+         }
+
+      cipher().encrypt(&last[0]);
+
+      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 cipher().block_size();
+   }
+
+void CBC_Decryption::update(secure_vector<byte>& buffer, size_t offset)
+   {
+   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
+   const size_t sz = buffer.size() - offset;
+   byte* buf = &buffer[offset];
+
+   const size_t BS = cipher().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[0], to_proc / BS);
+
+      xor_buf(&m_tempbuf[0], 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[0], to_proc);
+
+      buf += to_proc;
+      blocks -= to_proc / BS;
+      }
+   }
+
+void CBC_Decryption::finish(secure_vector<byte>& buffer, size_t offset)
+   {
+   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
+   const size_t sz = buffer.size() - offset;
+
+   const size_t BS = cipher().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
+   }
+
+bool CTS_Decryption::valid_nonce_length(size_t n) const
+   {
+   return (n == cipher().block_size());
+   }
+
+size_t CTS_Decryption::minimum_final_size() const
+   {
+   return cipher().block_size() + 1;
+   }
+
+void CTS_Decryption::finish(secure_vector<byte>& buffer, size_t offset)
+   {
+   BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
+   const size_t sz = buffer.size() - offset;
+   byte* buf = &buffer[offset];
+
+   const size_t BS = cipher().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<byte> last(buf + full_blocks, buf + full_blocks + final_bytes);
+      buffer.resize(full_blocks + offset);
+      update(buffer, offset);
+
+      cipher().decrypt(&last[0]);
+      xor_buf(&last[0], &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[0]);
+      xor_buf(&last[0], state_ptr(), BS);
+
+      buffer += last;
+      }
+
+   }
+
+}