path: root/src/tls/rec_wri.cpp

/*
* TLS Record Writing
* (C) 2004-2012 Jack Lloyd
*
* Released under the terms of the Botan license
*/

#include <botan/tls_record.h>
#include <botan/internal/tls_messages.h>
#include <botan/internal/tls_session_key.h>
#include <botan/internal/tls_handshake_hash.h>
#include <botan/lookup.h>
#include <botan/internal/rounding.h>
#include <botan/internal/assert.h>
#include <botan/loadstor.h>
#include <botan/libstate.h>

namespace Botan {

namespace TLS {

/*
* Record_Writer Constructor
*/
Record_Writer::Record_Writer(std::function<void (const byte[], size_t)> out,
                             RandomNumberGenerator& rng) :
   m_output_fn(out),
   m_writebuf(TLS_HEADER_SIZE + MAX_CIPHERTEXT_SIZE),
   m_rng(rng)
   {
   reset();
   set_maximum_fragment_size(0);
   }

void Record_Writer::set_maximum_fragment_size(size_t max_fragment)
   {
   if(max_fragment == 0)
      m_max_fragment = MAX_PLAINTEXT_SIZE;
   else
      m_max_fragment = clamp(max_fragment, 128, MAX_PLAINTEXT_SIZE);
   }

/*
* Reset the state
*/
void Record_Writer::reset()
   {
   set_maximum_fragment_size(0);
   m_cipher.reset();

   m_mac.reset();

   m_version = Protocol_Version();
   m_block_size = 0;
   m_mac_size = 0;
   m_iv_size = 0;

   m_seq_no = 0;
   }

/*
* Set the version to use
*/
void Record_Writer::set_version(Protocol_Version version)
   {
   m_version = version;
   }

/*
* Set the keys for writing
*/
void Record_Writer::change_cipher_spec(Connection_Side side,
                                       const Ciphersuite& suite,
                                       const Session_Keys& keys,
                                       byte compression_method)
   {
   m_cipher.reset();
   m_mac.reset();

   if(compression_method != NO_COMPRESSION)
      throw Internal_Error("Negotiated unknown compression algorithm");

   /*
   RFC 4346:
     A sequence number is incremented after each record: specifically,
     the first record transmitted under a particular connection state
     MUST use sequence number 0
   */
   m_seq_no = 0;

   SymmetricKey mac_key, cipher_key;
   InitializationVector iv;

   if(side == CLIENT)
      {
      cipher_key = keys.client_cipher_key();
      iv = keys.client_iv();
      mac_key = keys.client_mac_key();
      }
   else
      {
      cipher_key = keys.server_cipher_key();
      iv = keys.server_iv();
      mac_key = keys.server_mac_key();
      }

   const std::string cipher_algo = suite.cipher_algo();
   const std::string mac_algo = suite.mac_algo();

   if(have_block_cipher(cipher_algo))
      {
      m_cipher.append(get_cipher(
                       cipher_algo + "/CBC/NoPadding",
                       cipher_key, iv, ENCRYPTION)
         );
      m_block_size = block_size_of(cipher_algo);

      if(m_version.supports_explicit_cbc_ivs())
         m_iv_size = m_block_size;
      else
         m_iv_size = 0;
      }
   else if(have_stream_cipher(cipher_algo))
      {
      m_cipher.append(get_cipher(cipher_algo, cipher_key, ENCRYPTION));
      m_block_size = 0;
      m_iv_size = 0;
      }
   else
      throw Invalid_Argument("Record_Writer: Unknown cipher " + cipher_algo);

   if(have_hash(mac_algo))
      {
      Algorithm_Factory& af = global_state().algorithm_factory();

      if(m_version == Protocol_Version::SSL_V3)
         m_mac.reset(af.make_mac("SSL3-MAC(" + mac_algo + ")"));
      else
         m_mac.reset(af.make_mac("HMAC(" + mac_algo + ")"));

      m_mac->set_key(mac_key);
      m_mac_size = m_mac->output_length();
      }
   else
      throw Invalid_Argument("Record_Writer: Unknown hash " + mac_algo);
   }

/*
* Send one or more records to the other side
*/
void Record_Writer::send_array(byte type, const byte input[], size_t length)
   {
   if(length == 0)
      return;

   /*
   * If using CBC mode in SSLv3/TLS v1.0, send a single byte of
   * plaintext to randomize the (implicit) IV of the following main
   * block. If using a stream cipher, or TLS v1.1, this isn't
   * necessary.
   *
   * An empty record also works but apparently some implementations do
   * not like this (https://bugzilla.mozilla.org/show_bug.cgi?id=665814)
   *
   * See http://www.openssl.org/~bodo/tls-cbc.txt for background.
   */
   if((type == APPLICATION) && (m_block_size > 0) && (m_iv_size == 0))
      {
      send_record(type, &input[0], 1);
      input += 1;
      length -= 1;
      }

   while(length)
      {
      const size_t sending = std::min(length, m_max_fragment);
      send_record(type, &input[0], sending);

      input += sending;
      length -= sending;
      }
   }

/*
* Encrypt and send the record
*/
void Record_Writer::send_record(byte type, const byte input[], size_t length)
   {
   if(length >= MAX_PLAINTEXT_SIZE)
      throw Internal_Error("Record_Writer: Compressed packet is too big");

   if(m_mac_size == 0) // initial unencrypted handshake records
      {
      m_writebuf[0] = type;
      m_writebuf[1] = m_version.major_version();
      m_writebuf[2] = m_version.minor_version();
      m_writebuf[3] = get_byte<u16bit>(0, length);
      m_writebuf[4] = get_byte<u16bit>(1, length);

      copy_mem(&m_writebuf[TLS_HEADER_SIZE], input, length);

      m_output_fn(&m_writebuf[0], TLS_HEADER_SIZE + length);
      return;
      }

   m_mac->update_be(m_seq_no);
   m_mac->update(type);

   if(m_version != Protocol_Version::SSL_V3)
      {
      m_mac->update(m_version.major_version());
      m_mac->update(m_version.minor_version());
      }

   m_mac->update(get_byte<u16bit>(0, length));
   m_mac->update(get_byte<u16bit>(1, length));
   m_mac->update(input, length);

   const size_t buf_size = round_up(m_iv_size + length +
                                    m_mac->output_length() +
                                    (m_block_size ? 1 : 0),
                                    m_block_size);

   if(buf_size >= MAX_CIPHERTEXT_SIZE)
      throw Internal_Error("Record_Writer: Record is too big");

   BOTAN_ASSERT(m_writebuf.size() >= TLS_HEADER_SIZE + MAX_CIPHERTEXT_SIZE,
                "Write buffer is big enough");

   // TLS record header
   m_writebuf[0] = type;
   m_writebuf[1] = m_version.major_version();
   m_writebuf[2] = m_version.minor_version();
   m_writebuf[3] = get_byte<u16bit>(0, buf_size);
   m_writebuf[4] = get_byte<u16bit>(1, buf_size);

   byte* buf_write_ptr = &m_writebuf[TLS_HEADER_SIZE];

   if(m_iv_size)
      {
      m_rng.randomize(buf_write_ptr, m_iv_size);
      buf_write_ptr += m_iv_size;
      }

   copy_mem(buf_write_ptr, input, length);
   buf_write_ptr += length;

   m_mac->final(buf_write_ptr);
   buf_write_ptr += m_mac->output_length();

   if(m_block_size)
      {
      const size_t pad_val =
         buf_size - (m_iv_size + length + m_mac->output_length() + 1);

      for(size_t i = 0; i != pad_val + 1; ++i)
         {
         *buf_write_ptr = pad_val;
         buf_write_ptr += 1;
         }
      }

   // FIXME: this could be done in-place without copying
   m_cipher.process_msg(&m_writebuf[TLS_HEADER_SIZE], buf_size);

   const size_t ctext_size = m_cipher.remaining(Pipe::LAST_MESSAGE);

   BOTAN_ASSERT_EQUAL(ctext_size, buf_size, "Cipher encrypted full amount");

   if(ctext_size > MAX_CIPHERTEXT_SIZE)
      throw Internal_Error("Produced ciphertext larger than protocol allows");

   m_cipher.read(&m_writebuf[TLS_HEADER_SIZE], ctext_size, Pipe::LAST_MESSAGE);

   BOTAN_ASSERT_EQUAL(m_cipher.remaining(Pipe::LAST_MESSAGE), 0,
                      "No data remains in pipe");

   m_output_fn(&m_writebuf[0], TLS_HEADER_SIZE + buf_size);

   m_seq_no++;
   }

}

}