Method ProcessSessionRequestMessage

libi2pd/NTCP2.cpp:327–426

	}

	bool NTCP2Establisher::ProcessSessionRequestMessage (uint16_t& paddingLen, bool& clockSkew, bool& pq, bool decryptX)
	{
		clockSkew = false;
		pq = false;
		size_t offset = 0;
		if (decryptX)
		{
            // decrypt X
            auto x = GetRemotePub ();
            i2p::crypto::CBCDecryption decryption;
            decryption.SetKey (i2p::context.GetIdentHash ());
            decryption.Decrypt (m_Buffer, 32, i2p::context.GetNTCP2IV (), x);
            memcpy (m_IV, m_Buffer + 16, 16); // save last block as IV for SessionCreated
            if (x[31] & 0x80)
            {
#if OPENSSL_PQ
                if (m_CryptoType > i2p::data::CRYPTO_KEY_TYPE_ECIES_X25519_AEAD)
                {
                    pq = true;
                    x[31] &= 0x7F;
                }
#endif
                if (!pq)
                {
                    LogPrint (eLogWarning, "NTCP2: SessionRequest ML-KEM requested but not supported");
                    return false;
                }
            }
            else
                SetVersion (2); // regular x25519 requested
            // decryption key for next block
            if (!KDF1Bob ())
            {
                LogPrint (eLogWarning, "NTCP2: SessionRequest KDF failed");
                return false;
            }
		}
		offset += 32;
#if OPENSSL_PQ
        if (pq) return true; // we need to read extra ML-KEM block first
        if (m_CryptoType > i2p::data::CRYPTO_KEY_TYPE_ECIES_X25519_AEAD)
        {
            auto keyLen = i2p::crypto::GetMLKEMPublicKeyLen (m_CryptoType);
            std::vector<uint8_t> encapsKey(keyLen);
            if (Decrypt (m_Buffer + offset, encapsKey.data (), keyLen))
            {
                MixHash (m_Buffer + offset, keyLen + 16);
                offset += keyLen + 16;
                m_PQKeys = i2p::crypto::CreateMLKEMKeys (m_CryptoType);
                m_PQKeys->SetPublicKey (encapsKey.data ());
            }
        }
#endif
		// verify MAC and decrypt options block (32 bytes)
		uint8_t options[16];
		if (Decrypt (m_Buffer + offset, options, 16))
		{
            MixHash (m_Buffer + offset, 32);