/*
* Copyright (c) 2013-2026, The PurpleI2P Project
*
* This file is part of Purple i2pd project and licensed under BSD3
*
* See full license text in LICENSE file at top of project tree
*
*/

#include <memory>
#include <openssl/rand.h>
#include <openssl/sha.h>
#include "Log.h"
#include "Transports.h"
#include "Timestamp.h"
#include "I2PEndian.h"
#include "I2NPProtocol.h"
#include "util.h"
#include "TunnelConfig.h"

namespace i2p
{
namespace tunnel
{
	TunnelHopConfig::TunnelHopConfig (std::shared_ptr<const i2p::data::IdentityEx> r)
	{
		RAND_bytes ((uint8_t *)&tunnelID, 4);
		if (!tunnelID) tunnelID = 1; // tunnelID can't be zero
		isGateway = true;
		isEndpoint = true;
		ident = r;
		//nextRouter = nullptr;
		nextTunnelID = 0;

		next = nullptr;
		prev = nullptr;
	}

	void TunnelHopConfig::SetNextIdent (const i2p::data::IdentHash& ident)
	{
		nextIdent = ident;
		isEndpoint = false;
		RAND_bytes ((uint8_t *)&nextTunnelID, 4);
		if (!nextTunnelID) nextTunnelID = 1; // tunnelID can't be zero
	}

	void TunnelHopConfig::SetReplyHop (uint32_t replyTunnelID, const i2p::data::IdentHash& replyIdent)
	{
		nextIdent = replyIdent;
		nextTunnelID = replyTunnelID;
		isEndpoint = true;
	}

	void TunnelHopConfig::SetNext (TunnelHopConfig * n)
	{
		next = n;
		if (next)
		{
			next->prev = this;
			next->isGateway = false;
			isEndpoint = false;
			nextIdent = next->ident->GetIdentHash ();
			nextTunnelID = next->tunnelID;
		}
	}

	void TunnelHopConfig::SetPrev (TunnelHopConfig * p)
	{
		prev = p;
		if (prev)
		{
			prev->next = this;
			prev->isEndpoint = false;
			isGateway = false;
		}
	}

	void ShortECIESTunnelHopConfig::EncryptECIES (const uint8_t * plainText, uint8_t * encrypted)
	{
		if (!ident) return;
		i2p::crypto::InitNoiseNState (*this, ident->GetEncryptionPublicKey ());
		auto ephemeralKeys = i2p::transport::transports.GetNextX25519KeysPair ();
		memcpy (encrypted, ephemeralKeys->GetPublicKey (), 32);
		MixHash (encrypted, 32); // h = SHA256(h || sepk)
		encrypted += 32;
		uint8_t sharedSecret[32];
		ephemeralKeys->Agree (ident->GetEncryptionPublicKey (), sharedSecret); // x25519(sesk, hepk)
		MixKey (sharedSecret);
		if (!Encrypt (plainText, encrypted, SHORT_REQUEST_RECORD_CLEAR_TEXT_SIZE))
		{
			LogPrint (eLogWarning, "Tunnel: Plaintext AEAD encryption failed");
			return;
		}
		MixHash (encrypted, SHORT_REQUEST_RECORD_CLEAR_TEXT_SIZE + 16); // h = SHA256(h || ciphertext)
	}

	void ShortECIESTunnelHopConfig::CreateBuildRequestRecord (uint8_t * records, uint32_t replyMsgID)
	{
		// fill clear text
		uint8_t flag = 0;
		if (isGateway) flag |= TUNNEL_BUILD_RECORD_GATEWAY_FLAG;
		if (isEndpoint) flag |= TUNNEL_BUILD_RECORD_ENDPOINT_FLAG;
		uint8_t clearText[SHORT_REQUEST_RECORD_CLEAR_TEXT_SIZE ];
		htobe32buf (clearText + SHORT_REQUEST_RECORD_RECEIVE_TUNNEL_OFFSET, tunnelID);
		htobe32buf (clearText + SHORT_REQUEST_RECORD_NEXT_TUNNEL_OFFSET, nextTunnelID);
		memcpy (clearText + SHORT_REQUEST_RECORD_NEXT_IDENT_OFFSET, nextIdent, 32);
		clearText[SHORT_REQUEST_RECORD_FLAG_OFFSET] = flag;
		memset (clearText + SHORT_REQUEST_RECORD_MORE_FLAGS_OFFSET, 0, 2);
		clearText[SHORT_REQUEST_RECORD_LAYER_ENCRYPTION_TYPE] = 0; // AES
		htobe32buf (clearText + SHORT_REQUEST_RECORD_REQUEST_TIME_OFFSET, i2p::util::GetMinutesSinceEpoch ());
		htobe32buf (clearText + SHORT_REQUEST_RECORD_REQUEST_EXPIRATION_OFFSET , 600); // +10 minutes
		htobe32buf (clearText + SHORT_REQUEST_RECORD_SEND_MSG_ID_OFFSET, replyMsgID);
		i2p::util::Mapping options;
		auto optionsSize = options.ToBuffer (clearText + SHORT_REQUEST_RECORD_TUNNEL_BUILD_OPTIONS_OFFSET,
			SHORT_REQUEST_RECORD_CLEAR_TEXT_SIZE - SHORT_REQUEST_RECORD_TUNNEL_BUILD_OPTIONS_OFFSET);
		if (SHORT_REQUEST_RECORD_TUNNEL_BUILD_OPTIONS_OFFSET + optionsSize < SHORT_REQUEST_RECORD_CLEAR_TEXT_SIZE)
			memset (clearText + SHORT_REQUEST_RECORD_TUNNEL_BUILD_OPTIONS_OFFSET + optionsSize, 0,
				SHORT_REQUEST_RECORD_CLEAR_TEXT_SIZE - SHORT_REQUEST_RECORD_TUNNEL_BUILD_OPTIONS_OFFSET - optionsSize);
		// encrypt
		uint8_t * record = records + recordIndex*SHORT_TUNNEL_BUILD_RECORD_SIZE;
		EncryptECIES (clearText, record + SHORT_REQUEST_RECORD_ENCRYPTED_OFFSET);
		// derive keys
		i2p::crypto::HKDF (m_CK, nullptr, 0, "SMTunnelReplyKey", m_CK);
		memcpy (replyKey, m_CK + 32, 32);
		i2p::crypto::HKDF (m_CK, nullptr, 0, "SMTunnelLayerKey", m_CK);
		memcpy (layerKey, m_CK + 32, 32);
		if (isEndpoint)
		{
			i2p::crypto::HKDF (m_CK, nullptr, 0, "TunnelLayerIVKey", m_CK);
			memcpy (ivKey, m_CK + 32, 32);
			i2p::crypto::HKDF (m_CK, nullptr, 0, "RGarlicKeyAndTag", m_CK); // OTBRM garlic key m_CK + 32, tag first 8 bytes of m_CK
		}
		else
			memcpy (ivKey, m_CK, 32); // last HKDF
		memcpy (record + BUILD_REQUEST_RECORD_TO_PEER_OFFSET, (const uint8_t *)ident->GetIdentHash (), 16);
	}

	bool ShortECIESTunnelHopConfig::DecryptBuildResponseRecord (uint8_t * records) const
	{
		uint8_t * record = records + recordIndex*SHORT_TUNNEL_BUILD_RECORD_SIZE;
		uint8_t nonce[12];
		memset (nonce, 0, 12);
		nonce[4] = recordIndex; // nonce is record index
		if (!i2p::crypto::AEADChaCha20Poly1305 (record, SHORT_TUNNEL_BUILD_RECORD_SIZE - 16,
			m_H, 32, replyKey, nonce, record, SHORT_TUNNEL_BUILD_RECORD_SIZE - 16, false)) // decrypt
		{
			LogPrint (eLogWarning, "Tunnel: Response AEAD decryption failed");
			return false;
		}
		return true;
	}

	void ShortECIESTunnelHopConfig::DecryptRecord (uint8_t * records, int index) const
	{
		uint8_t * record = records + index*SHORT_TUNNEL_BUILD_RECORD_SIZE;
		uint8_t nonce[12];
		memset (nonce, 0, 12);
		nonce[4] = index; // nonce is index
		i2p::crypto::ChaCha20 (record, SHORT_TUNNEL_BUILD_RECORD_SIZE, replyKey, nonce, record);
	}

	std::pair<const uint8_t *, uint64_t> ShortECIESTunnelHopConfig::GetGarlicKey () const
	{
		return { m_CK + 32, buf64toh (m_CK) };
	}

	void ShortPhonyTunnelHopConfig::CreateBuildRequestRecord (uint8_t * records, uint32_t replyMsgID)
	{
		uint8_t * record = records + recordIndex*SHORT_TUNNEL_BUILD_RECORD_SIZE;
		memcpy (record + BUILD_REQUEST_RECORD_TO_PEER_OFFSET, (const uint8_t *)i2p::context.GetIdentHash (), 16);
		memcpy (record + SHORT_REQUEST_RECORD_ENCRYPTED_OFFSET, i2p::transport::transports.GetNextX25519KeysPair ()->GetPublicKey (), 32);
		RAND_bytes (record + 48, SHORT_TUNNEL_BUILD_RECORD_SIZE - 48);
	}

	TunnelConfig::TunnelConfig (const std::vector<std::shared_ptr<const i2p::data::IdentityEx> >& peers,
		i2p::data::RouterInfo::CompatibleTransports farEndTransports):
		m_FarEndTransports (farEndTransports)
	{
		// inbound
		CreatePeers (peers);
		m_LastHop->SetNextIdent (i2p::context.GetIdentHash ());
	}

	TunnelConfig::TunnelConfig (const std::vector<std::shared_ptr<const i2p::data::IdentityEx> >& peers,
		uint32_t replyTunnelID, const i2p::data::IdentHash& replyIdent,
		i2p::data::RouterInfo::CompatibleTransports farEndTransports):
		m_FarEndTransports (farEndTransports)
	{
		// outbound
		CreatePeers (peers);
		m_FirstHop->isGateway = false;
		m_LastHop->SetReplyHop (replyTunnelID, replyIdent);
	}

	void TunnelConfig::CreatePeers (const std::vector<std::shared_ptr<const i2p::data::IdentityEx> >& peers)
	{
		TunnelHopConfig * prev = nullptr;
		for (const auto& it: peers)
		{
			TunnelHopConfig * hop = new ShortECIESTunnelHopConfig (it);
			if (prev)
				prev->SetNext (hop);
			else
				m_FirstHop = hop;
			prev = hop;
		}
		m_LastHop = prev;
	}

	void TunnelConfig::CreatePhonyHop ()
	{
		if (m_LastHop && m_LastHop->ident)
		{
			TunnelHopConfig * hop = new ShortPhonyTunnelHopConfig ();
			hop->prev = m_LastHop;
			m_LastHop->next = hop;
			m_LastHop = hop;
		}
	}

	void TunnelConfig::DeletePhonyHop ()
	{
		if (m_LastHop && !m_LastHop->ident)
		{
			if (m_LastHop->prev) m_LastHop->prev->next = nullptr;
			else m_FirstHop = nullptr;
			auto tmp = m_LastHop;
			m_LastHop = m_LastHop->prev;
			delete tmp;
		}
	}
}
}
