Method SendSessionConfirmed

libi2pd/SSU2Session.cpp:1119–1198

	}

	void SSU2Session::SendSessionConfirmed (const uint8_t * Y)
	{
		// we are Alice
		m_SentHandshakePacket.reset (new HandshakePacket);
		m_SentHandshakePacket->sendTime = i2p::util::GetMillisecondsSinceEpoch ();

		uint8_t kh2[32];
		i2p::crypto::HKDF (m_NoiseState->m_CK, nullptr, 0, "SessionConfirmed", kh2, 32); // k_header_2 = HKDF(chainKey, ZEROLEN, "SessionConfirmed", 32)
		// fill packet
		Header& header = m_SentHandshakePacket->header;
		header.h.connID = m_DestConnID; // dest id
		header.h.packetNum = 0; // always zero
		header.h.type = eSSU2SessionConfirmed;
		memset (header.h.flags, 0, 3);
		header.h.flags[0] = 1; // frag, total fragments always 1
		// payload
		size_t maxPayloadSize = m_MaxPayloadSize - 48; // for part 2, 48 is part1
		uint8_t * payload = m_SentHandshakePacket->payload;
		size_t payloadSize = CreateRouterInfoBlock (payload, maxPayloadSize, i2p::context.CopyRouterInfoBuffer ());
		if (!payloadSize)
		{
			// split by two fragments
			maxPayloadSize += m_MaxPayloadSize;
			payloadSize = CreateRouterInfoBlock (payload, maxPayloadSize, i2p::context.CopyRouterInfoBuffer ());
			header.h.flags[0] = 0x02; // frag 0, total fragments 2
			// TODO: check if we need more fragments
		}
		if (payloadSize < maxPayloadSize)
			payloadSize += CreatePaddingBlock (payload + payloadSize, maxPayloadSize - payloadSize);
		// KDF for Session Confirmed part 1
		m_NoiseState->MixHash (header.buf, 16); // h = SHA256(h || header)
		// Encrypt part 1
		uint8_t * part1 = m_SentHandshakePacket->headerX;
		m_NoiseState->Encrypt (i2p::context.GetSSU2StaticPublicKey (), part1, 32);
		m_NoiseState->MixHash (part1, 48); // h = SHA256(h || ciphertext);
		// KDF for Session Confirmed part 2
		uint8_t sharedSecret[32];
		i2p::context.GetSSU2StaticKeys ().Agree (Y, sharedSecret);
		m_NoiseState->MixKey (sharedSecret);
		// Encrypt part2
		m_NoiseState->Encrypt (payload, payload, payloadSize);
		payloadSize += 16;
		m_NoiseState->MixHash (payload, payloadSize); // h = SHA256(h || ciphertext);
		m_SentHandshakePacket->payloadSize = payloadSize;
		if (header.h.flags[0] > 1)
		{
			if (payloadSize > m_MaxPayloadSize - 48)
			{
				payloadSize = m_MaxPayloadSize - 48 - (m_Server.GetRng ()() % 16);
				if (m_SentHandshakePacket->payloadSize - payloadSize < 24)
					payloadSize -= 24;
			}
			else
				header.h.flags[0] = 1;
		}
		// Encrypt header
		header.ll[0] ^= CreateHeaderMask (m_Address->i, payload + (payloadSize - 24));
		header.ll[1] ^= CreateHeaderMask (kh2, payload + (payloadSize - 12));