/* * 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 #include 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; }; class Stream_Sequence_Numbers final : public Connection_Sequence_Numbers { public: 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 = 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++; } 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(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 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; m_window_bits |= (static_cast(1) << offset); } } private: std::map 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