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/*
* TLS Record Handling
* (C) 2012 Jack Lloyd
*
* Released under the terms of the Botan license
*/
#include <botan/tls_record.h>
#include <botan/internal/tls_session_key.h>
#include <botan/libstate.h>
#include <botan/internal/rounding.h>
#include <botan/internal/assert.h>
#include <botan/internal/xor_buf.h>
namespace Botan {
namespace TLS {
Connection_Cipher_State::Connection_Cipher_State(
Protocol_Version version,
Connection_Side side,
const Ciphersuite& suite,
const Session_Keys& keys)
{
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();
Algorithm_Factory& af = global_state().algorithm_factory();
if(const BlockCipher* bc = af.prototype_block_cipher(cipher_algo))
{
m_block_cipher.reset(bc->clone());
m_block_cipher->set_key(cipher_key);
m_block_cipher_cbc_state = iv.bits_of();
m_block_size = bc->block_size();
if(version.supports_explicit_cbc_ivs())
m_iv_size = m_block_size;
else
m_iv_size = 0;
}
else if(const StreamCipher* sc = af.prototype_stream_cipher(cipher_algo))
{
m_stream_cipher.reset(sc->clone());
m_stream_cipher->set_key(cipher_key);
m_block_size = 0;
m_iv_size = 0;
}
else
throw Invalid_Argument("Unknown TLS cipher " + cipher_algo);
if(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);
}
size_t write_record(std::vector<byte>& output,
byte msg_type, const byte msg[], size_t msg_length,
u64bit msg_sequence_number,
Protocol_Version version,
Connection_Cipher_State* cipherstate,
RandomNumberGenerator& rng)
{
BOTAN_ASSERT(output.size() >= TLS_HEADER_SIZE + msg_length,
"Write buffer is big enough");
output[0] = msg_type;
output[1] = version.major_version();
output[2] = version.minor_version();
if(!cipherstate) // initial unencrypted handshake records
{
output[3] = get_byte<u16bit>(0, msg_length);
output[4] = get_byte<u16bit>(1, msg_length);
copy_mem(&output[TLS_HEADER_SIZE], msg, msg_length);
return (TLS_HEADER_SIZE + msg_length);
}
cipherstate->mac()->update_be(msg_sequence_number);
cipherstate->mac()->update(msg_type);
if(version != Protocol_Version::SSL_V3)
{
cipherstate->mac()->update(version.major_version());
cipherstate->mac()->update(version.minor_version());
}
cipherstate->mac()->update(get_byte<u16bit>(0, msg_length));
cipherstate->mac()->update(get_byte<u16bit>(1, msg_length));
cipherstate->mac()->update(msg, msg_length);
const size_t block_size = cipherstate->block_size();
const size_t iv_size = cipherstate->iv_size();
const size_t mac_size = cipherstate->mac_size();
const size_t buf_size = round_up(
iv_size + msg_length + mac_size + (block_size ? 1 : 0),
block_size);
if(buf_size >= MAX_CIPHERTEXT_SIZE)
throw Internal_Error("Record_Writer: Record is too big");
BOTAN_ASSERT(output.size() >= TLS_HEADER_SIZE + MAX_CIPHERTEXT_SIZE,
"Write buffer is big enough");
output[3] = get_byte<u16bit>(0, buf_size);
output[4] = get_byte<u16bit>(1, buf_size);
byte* buf_write_ptr = &output[TLS_HEADER_SIZE];
if(iv_size)
{
rng.randomize(buf_write_ptr, iv_size);
buf_write_ptr += iv_size;
}
copy_mem(buf_write_ptr, msg, msg_length);
buf_write_ptr += msg_length;
cipherstate->mac()->final(buf_write_ptr);
buf_write_ptr += mac_size;
if(block_size)
{
const size_t pad_val =
buf_size - (iv_size + msg_length + mac_size + 1);
for(size_t i = 0; i != pad_val + 1; ++i)
{
*buf_write_ptr = pad_val;
buf_write_ptr += 1;
}
}
if(buf_size > MAX_CIPHERTEXT_SIZE)
throw Internal_Error("Produced ciphertext larger than protocol allows");
if(StreamCipher* sc = cipherstate->stream_cipher())
{
sc->cipher1(&output[TLS_HEADER_SIZE], buf_size);
}
else if(BlockCipher* bc = cipherstate->block_cipher())
{
secure_vector<byte>& cbc_state = cipherstate->cbc_state();
BOTAN_ASSERT(buf_size % block_size == 0,
"Buffer is an even multiple of block size");
byte* buf = &output[TLS_HEADER_SIZE];
const size_t blocks = buf_size / block_size;
xor_buf(&buf[0], &cbc_state[0], block_size);
bc->encrypt(&buf[0]);
for(size_t i = 1; i <= blocks; ++i)
{
xor_buf(&buf[block_size*i], &buf[block_size*(i-1)], block_size);
bc->encrypt(&buf[block_size*i]);
}
cbc_state.assign(&buf[block_size*(blocks-1)],
&buf[block_size*blocks]);
}
else
throw Internal_Error("NULL cipher not supported");
return (TLS_HEADER_SIZE + buf_size);
}
}
}
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