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/*
* TLS Sequence Number Handling
* (C) 2012 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#ifndef BOTAN_TLS_SEQ_NUMBERS_H_
#define BOTAN_TLS_SEQ_NUMBERS_H_
#include <botan/types.h>
#include <map>
namespace Botan {
namespace TLS {
class Connection_Sequence_Numbers
{
public:
virtual ~Connection_Sequence_Numbers() = default;
virtual void new_read_cipher_state() = 0;
virtual void new_write_cipher_state() = 0;
virtual uint16_t current_read_epoch() const = 0;
virtual uint16_t current_write_epoch() const = 0;
virtual uint64_t next_write_sequence(uint16_t) = 0;
virtual uint64_t next_read_sequence() = 0;
virtual bool already_seen(uint64_t seq) const = 0;
virtual void read_accept(uint64_t seq) = 0;
virtual void reset() = 0;
};
class Stream_Sequence_Numbers final : public Connection_Sequence_Numbers
{
public:
Stream_Sequence_Numbers() { Stream_Sequence_Numbers::reset(); }
void reset() override
{
m_write_seq_no = 0;
m_read_seq_no = 0;
m_read_epoch = 0;
m_write_epoch = 0;
}
void new_read_cipher_state() override { m_read_seq_no = 0; m_read_epoch++; }
void new_write_cipher_state() override { m_write_seq_no = 0; m_write_epoch++; }
uint16_t current_read_epoch() const override { return m_read_epoch; }
uint16_t current_write_epoch() const override { return m_write_epoch; }
uint64_t next_write_sequence(uint16_t) override { return m_write_seq_no++; }
uint64_t next_read_sequence() override { return m_read_seq_no; }
bool already_seen(uint64_t) const override { return false; }
void read_accept(uint64_t) override { m_read_seq_no++; }
private:
uint64_t m_write_seq_no;
uint64_t m_read_seq_no;
uint16_t m_read_epoch;
uint16_t m_write_epoch;
};
class Datagram_Sequence_Numbers final : public Connection_Sequence_Numbers
{
public:
Datagram_Sequence_Numbers() { Datagram_Sequence_Numbers::reset(); }
void reset() override
{
m_write_seqs.clear();
m_write_seqs[0] = 0;
m_write_epoch = 0;
m_read_epoch = 0;
m_window_highest = 0;
m_window_bits = 0;
}
void new_read_cipher_state() override { m_read_epoch++; }
void new_write_cipher_state() override
{
m_write_epoch++;
m_write_seqs[m_write_epoch] = 0;
}
uint16_t current_read_epoch() const override { return m_read_epoch; }
uint16_t current_write_epoch() const override { return m_write_epoch; }
uint64_t next_write_sequence(uint16_t epoch) override
{
auto i = m_write_seqs.find(epoch);
BOTAN_ASSERT(i != m_write_seqs.end(), "Found epoch");
return (static_cast<uint64_t>(epoch) << 48) | i->second++;
}
uint64_t next_read_sequence() override
{
throw Invalid_State("DTLS uses explicit sequence numbers");
}
bool already_seen(uint64_t sequence) const override
{
const size_t window_size = sizeof(m_window_bits) * 8;
if(sequence > m_window_highest)
{
return false;
}
const uint64_t offset = m_window_highest - sequence;
if(offset >= window_size)
{
return true; // really old?
}
return (((m_window_bits >> offset) & 1) == 1);
}
void read_accept(uint64_t sequence) override
{
const size_t window_size = sizeof(m_window_bits) * 8;
if(sequence > m_window_highest)
{
// We've received a later sequence which advances our window
const uint64_t offset = sequence - m_window_highest;
m_window_highest += offset;
if(offset >= window_size)
m_window_bits = 0;
else
m_window_bits <<= offset;
m_window_bits |= 0x01;
}
else
{
const uint64_t offset = m_window_highest - sequence;
if(offset < window_size)
{
// We've received an old sequence but still within our window
m_window_bits |= (static_cast<uint64_t>(1) << offset);
}
else
{
// This occurs only if we have reset state (DTLS reconnection case)
m_window_highest = sequence;
m_window_bits = 0;
}
}
}
private:
std::map<uint16_t, uint64_t> m_write_seqs;
uint16_t m_write_epoch = 0;
uint16_t m_read_epoch = 0;
uint64_t m_window_highest = 0;
uint64_t m_window_bits = 0;
};
}
}
#endif
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