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/*
* TLS Record Reading
* (C) 2004-2012 Jack Lloyd
*
* Released under the terms of the Botan license
*/
#include <botan/tls_record.h>
#include <botan/lookup.h>
#include <botan/loadstor.h>
#include <botan/internal/tls_session_key.h>
#include <botan/internal/rounding.h>
#include <botan/internal/assert.h>
namespace Botan {
namespace TLS {
Record_Reader::Record_Reader() :
m_readbuf(TLS_HEADER_SIZE + MAX_CIPHERTEXT_SIZE),
m_mac(0)
{
reset();
set_maximum_fragment_size(0);
}
/*
* Reset the state
*/
void Record_Reader::reset()
{
m_macbuf.clear();
zeroise(m_readbuf);
m_readbuf_pos = 0;
m_cipher.reset();
delete m_mac;
m_mac = 0;
m_block_size = 0;
m_iv_size = 0;
m_version = Protocol_Version();
m_seq_no = 0;
set_maximum_fragment_size(0);
}
void Record_Reader::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);
}
/*
* Set the version to use
*/
void Record_Reader::set_version(Protocol_Version version)
{
m_version = version;
}
/*
* Set the keys for reading
*/
void Record_Reader::activate(const Ciphersuite& suite,
const Session_Keys& keys,
Connection_Side side)
{
m_cipher.reset();
delete m_mac;
m_mac = 0;
m_seq_no = 0;
SymmetricKey mac_key, cipher_key;
InitializationVector iv;
if(side == CLIENT)
{
cipher_key = keys.server_cipher_key();
iv = keys.server_iv();
mac_key = keys.server_mac_key();
}
else
{
cipher_key = keys.client_cipher_key();
iv = keys.client_iv();
mac_key = keys.client_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, DECRYPTION)
);
m_block_size = block_size_of(cipher_algo);
if(m_version >= Protocol_Version::TLS_V11)
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, DECRYPTION));
m_block_size = 0;
m_iv_size = 0;
}
else
throw Invalid_Argument("Record_Reader: 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 = af.make_mac("SSL3-MAC(" + mac_algo + ")");
else
m_mac = af.make_mac("HMAC(" + mac_algo + ")");
m_mac->set_key(mac_key);
m_macbuf.resize(m_mac->output_length());
}
else
throw Invalid_Argument("Record_Reader: Unknown hash " + mac_algo);
}
size_t Record_Reader::fill_buffer_to(const byte*& input,
size_t& input_size,
size_t& input_consumed,
size_t desired)
{
if(desired <= m_readbuf_pos)
return 0; // already have it
const size_t space_available = (m_readbuf.size() - m_readbuf_pos);
const size_t taken = std::min(input_size, desired - m_readbuf_pos);
if(taken > space_available)
throw TLS_Exception(RECORD_OVERFLOW,
"Record is larger than allowed maximum size");
copy_mem(&m_readbuf[m_readbuf_pos], input, taken);
m_readbuf_pos += taken;
input_consumed += taken;
input_size -= taken;
input += taken;
return (desired - m_readbuf_pos); // how many bytes do we still need?
}
/*
* Retrieve the next record
*/
size_t Record_Reader::add_input(const byte input_array[], size_t input_sz,
size_t& consumed,
byte& msg_type,
MemoryVector<byte>& msg)
{
const byte* input = &input_array[0];
consumed = 0;
if(m_readbuf_pos < TLS_HEADER_SIZE) // header incomplete?
{
if(size_t needed = fill_buffer_to(input, input_sz, consumed, TLS_HEADER_SIZE))
return needed;
BOTAN_ASSERT_EQUAL(m_readbuf_pos, TLS_HEADER_SIZE,
"Have an entire header");
}
// Possible SSLv2 format client hello
if((!m_mac) && (m_readbuf[0] & 0x80) && (m_readbuf[2] == 1))
{
if(m_readbuf[3] == 0 && m_readbuf[4] == 2)
throw TLS_Exception(PROTOCOL_VERSION,
"Client claims to only support SSLv2, rejecting");
if(m_readbuf[3] >= 3) // SSLv2 mapped TLS hello, then?
{
size_t record_len = make_u16bit(m_readbuf[0], m_readbuf[1]) & 0x7FFF;
if(size_t needed = fill_buffer_to(input, input_sz, consumed, record_len + 2))
return needed;
BOTAN_ASSERT_EQUAL(m_readbuf_pos, (record_len + 2),
"Have the entire SSLv2 hello");
msg_type = HANDSHAKE;
msg.resize(record_len + 4);
// Fake v3-style handshake message wrapper
msg[0] = CLIENT_HELLO_SSLV2;
msg[1] = 0;
msg[2] = m_readbuf[0] & 0x7F;
msg[3] = m_readbuf[1];
copy_mem(&msg[4], &m_readbuf[2], m_readbuf_pos - 2);
m_readbuf_pos = 0;
return 0;
}
}
if(m_readbuf[0] != CHANGE_CIPHER_SPEC &&
m_readbuf[0] != ALERT &&
m_readbuf[0] != HANDSHAKE &&
m_readbuf[0] != APPLICATION_DATA)
{
throw TLS_Exception(UNEXPECTED_MESSAGE,
"Unknown record type " + to_string(m_readbuf[0]) +
" from counterparty");
}
const size_t record_len = make_u16bit(m_readbuf[3], m_readbuf[4]);
if(m_version.major_version())
{
if(m_readbuf[1] != m_version.major_version() ||
m_readbuf[2] != m_version.minor_version())
{
throw TLS_Exception(PROTOCOL_VERSION,
"Got unexpected version from counterparty");
}
}
if(record_len > MAX_CIPHERTEXT_SIZE)
throw TLS_Exception(RECORD_OVERFLOW,
"Got message that exceeds maximum size");
if(size_t needed = fill_buffer_to(input, input_sz, consumed,
TLS_HEADER_SIZE + record_len))
return needed;
BOTAN_ASSERT_EQUAL(static_cast<size_t>(TLS_HEADER_SIZE) + record_len,
m_readbuf_pos,
"Have the full record");
// Null mac means no encryption either, only valid during handshake
if(!m_mac)
{
if(m_readbuf[0] != CHANGE_CIPHER_SPEC &&
m_readbuf[0] != ALERT &&
m_readbuf[0] != HANDSHAKE)
{
throw TLS_Exception(DECODE_ERROR, "Invalid msg type received during handshake");
}
msg_type = m_readbuf[0];
msg.resize(record_len);
copy_mem(&msg[0], &m_readbuf[TLS_HEADER_SIZE], record_len);
m_readbuf_pos = 0;
return 0; // got a full record
}
// Otherwise, decrypt, check MAC, return plaintext
// FIXME: avoid memory allocation by processing in place
m_cipher.process_msg(&m_readbuf[TLS_HEADER_SIZE], record_len);
size_t got_back = m_cipher.read(&m_readbuf[TLS_HEADER_SIZE], record_len, Pipe::LAST_MESSAGE);
BOTAN_ASSERT_EQUAL(got_back, record_len, "Cipher encrypted full amount");
BOTAN_ASSERT_EQUAL(m_cipher.remaining(Pipe::LAST_MESSAGE), 0,
"Cipher had no remaining inputs");
size_t pad_size = 0;
if(m_block_size)
{
byte pad_value = m_readbuf[TLS_HEADER_SIZE + (record_len-1)];
pad_size = pad_value + 1;
/*
* Check the padding; if it is wrong, then say we have 0 bytes of
* padding, which should ensure that the MAC check below does not
* succeed. This hides a timing channel.
*
* This particular countermeasure is recommended in the TLS 1.2
* spec (RFC 5246) in section 6.2.3.2
*/
if(m_version == Protocol_Version::SSL_V3)
{
if(pad_value > m_block_size)
pad_size = 0;
}
else
{
bool padding_good = true;
for(size_t i = 0; i != pad_size; ++i)
if(m_readbuf[TLS_HEADER_SIZE + (record_len-i-1)] != pad_value)
padding_good = false;
if(!padding_good)
pad_size = 0;
}
}
const size_t mac_pad_iv_size = m_macbuf.size() + pad_size + m_iv_size;
if(record_len < mac_pad_iv_size)
throw Decoding_Error("Record sent with invalid length");
const u16bit plain_length = record_len - mac_pad_iv_size;
if(plain_length > m_max_fragment)
throw TLS_Exception(RECORD_OVERFLOW, "Plaintext record is too large");
m_mac->update_be(m_seq_no);
m_mac->update(m_readbuf[0]); // msg_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_be(plain_length);
m_mac->update(&m_readbuf[TLS_HEADER_SIZE + m_iv_size], plain_length);
++m_seq_no;
m_mac->final(m_macbuf);
const size_t mac_offset = record_len - (m_macbuf.size() + pad_size);
if(!same_mem(&m_readbuf[TLS_HEADER_SIZE + mac_offset], &m_macbuf[0], m_macbuf.size()))
throw TLS_Exception(BAD_RECORD_MAC, "Message authentication failure");
msg_type = m_readbuf[0];
msg.resize(plain_length);
copy_mem(&msg[0], &m_readbuf[TLS_HEADER_SIZE + m_iv_size], plain_length);
m_readbuf_pos = 0;
return 0;
}
}
}
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