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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>
namespace Botan {
namespace TLS {
class Connection_Sequence_Numbers
{
public:
virtual ~Connection_Sequence_Numbers() {}
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;
};
class Stream_Sequence_Numbers final : public Connection_Sequence_Numbers
{
public:
void new_read_cipher_state() override { m_read_seq_no = 0; m_read_epoch += 1; }
void new_write_cipher_state() override { m_write_seq_no = 0; m_write_epoch += 1; }
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 = 0;
uint64_t m_read_seq_no = 0;
uint16_t m_read_epoch = 0;
uint16_t m_write_epoch = 0;
};
class Datagram_Sequence_Numbers final : public Connection_Sequence_Numbers
{
public:
Datagram_Sequence_Numbers() { m_write_seqs[0] = 0; }
void new_read_cipher_state() override { m_read_epoch += 1; }
void new_write_cipher_state() override
{
m_write_epoch += 1;
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 Exception("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)
{
const size_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;
m_window_bits |= (static_cast<uint64_t>(1) << offset);
}
}
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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