/*

WhatsAppWeb plugin for Miranda NG
Copyright © 2019-21 George Hazan

*/

#include "stdafx.h"

bool WhatsAppProto::getBlob(const char *szSetting, MBinBuffer &buf)
{
	DBVARIANT dbv = { DBVT_BLOB };
	if (db_get(0, m_szModuleName, szSetting, &dbv))
		return false;

	buf.assign(dbv.pbVal, dbv.cpbVal);
	db_free(&dbv);
	return true;
}

/////////////////////////////////////////////////////////////////////////////////////////
// sends a piece of JSON to a server via a websocket, masked

int WhatsAppProto::WSSend(const CMStringA &str, WA_PKT_HANDLER pHandler)
{
	if (m_hServerConn == nullptr)
		return -1;

	int pktId = ++m_iPktNumber;

	CMStringA buf;
	buf.Format("%d.--%d,", (int)m_iLoginTime, pktId);
	if (!str.IsEmpty()) {
		buf.AppendChar(',');
		buf += str;
	}

	if (pHandler != nullptr) {
		auto *pReq = new WARequest;
		pReq->issued = time(0);
		pReq->pHandler = pHandler;
		pReq->pktId = pktId;

		mir_cslock lck(m_csPacketQueue);
		m_arPacketQueue.insert(pReq);
	}

	debugLogA("Sending packet #%d: %s", pktId, buf.c_str());
	WebSocket_Send(m_hServerConn, buf.c_str(), buf.GetLength());
	return pktId;
}

void WhatsAppProto::OnLoggedIn()
{
	debugLogA("CDiscordProto::OnLoggedIn");
	m_bOnline = true;

	ProtoBroadcastAck(0, ACKTYPE_STATUS, ACKRESULT_SUCCESS, (HANDLE)m_iStatus, m_iDesiredStatus);
	m_iStatus = m_iDesiredStatus;
}

void WhatsAppProto::OnLoggedOut(void)
{
	debugLogA("CDiscordProto::OnLoggedOut");
	m_bOnline = false;
	m_bTerminated = true;
	m_iPktNumber = 0;

	ProtoBroadcastAck(0, ACKTYPE_STATUS, ACKRESULT_SUCCESS, (HANDLE)m_iStatus, ID_STATUS_OFFLINE);
	m_iStatus = m_iDesiredStatus = ID_STATUS_OFFLINE;

	setAllContactStatuses(ID_STATUS_OFFLINE, false);
}

/////////////////////////////////////////////////////////////////////////////////////////

bool WhatsAppProto::ProcessChallenge(const CMStringA &szChallenge)
{
	if (szChallenge.IsEmpty() || mac_key.isEmpty())
		return false;

	size_t cbLen;
	void *pChallenge = mir_base64_decode(szChallenge, &cbLen);

	BYTE digest[32];
	unsigned cbResult = sizeof(digest);
	HMAC(EVP_sha256(), mac_key.data(), (int)mac_key.length(), (BYTE*)pChallenge, (int)cbLen, digest, &cbResult);

	ptrA szServer(getStringA(DBKEY_SERVER_TOKEN));
	CMStringA payload(FORMAT, "[\"admin\",\"challenge\",\"%s\",\"%s\",\"%s\"]",
		ptrA(mir_base64_encode(digest, cbResult)).get(), szServer.get(), m_szClientId.c_str());
	WSSend(payload);
	return true;
}

/////////////////////////////////////////////////////////////////////////////////////////

bool WhatsAppProto::ProcessSecret(const CMStringA &szSecret)
{
	if (szSecret.IsEmpty())
		return false;

	size_t secretLen = 0;
	mir_ptr<BYTE> pSecret((BYTE *)mir_base64_decode(szSecret, &secretLen));
	if (pSecret == nullptr || secretLen != 144) {
		debugLogA("Invalid secret key, dropping session (secret len = %u", (unsigned)secretLen);
		return false;
	}

	ec_public_key pPeerPublic;
	memcpy(pPeerPublic.data, pSecret, 32);

	MBinBuffer privKey;
	if (!getBlob(DBKEY_PRIVATE_KEY, privKey))
		return false;

	ec_private_key pMyPrivate;
	memcpy(pMyPrivate.data, privKey.data(), 32);

	uint8_t *pSharedKey, *pSharedExpanded;
	int sharedLen = curve_calculate_agreement(&pSharedKey, &pPeerPublic, &pMyPrivate);
	{
		BYTE salt[32], md[32];
		unsigned int md_len = 32;
		memset(salt, 0, sizeof(salt));
		HMAC(EVP_sha256(), salt, sizeof(salt), pSharedKey, sharedLen, md, &md_len);

		hkdf_context *pHKDF;
		hkdf_create(&pHKDF, 3, g_plugin.pCtx);
		hkdf_expand(pHKDF, &pSharedExpanded, md, sizeof(md), 0, 0, 80);
		hkdf_destroy(pHKDF);
	}

	// validation
	{
		unsigned int md_len = 32;
		BYTE sum[32], md[32], enc[112], *key = pSharedExpanded + 32;
		memcpy(enc, pSecret, 32);
		memcpy(enc + 32, (BYTE *)pSecret + 64, 80);
		memcpy(sum, (BYTE *)pSecret + 32, 32);
		HMAC(EVP_sha256(), key, 32, enc, sizeof(enc), md, &md_len);
		if (memcmp(md, sum, 32)) {
			debugLogA("Secret key validation failed, exiting");
			return false;
		}
	}

	// woohoo, everything is ok, decrypt keys
	{
		BYTE enc[80], dec[112], key[32], iv[16];
		memcpy(key, pSharedExpanded, sizeof(key));
		memcpy(key, pSharedExpanded+64, sizeof(iv));
		memcpy(enc, pSecret.get() + 64, sizeof(enc));

		int dec_len = 0, final_len = 0;
		EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
		EVP_DecryptInit_ex(ctx, EVP_aes_256_cbc(), NULL, key, iv);
		EVP_DecryptUpdate(ctx, dec, &dec_len, enc, sizeof(enc));
		EVP_DecryptFinal_ex(ctx, dec + dec_len, &final_len);
		dec_len += final_len;
		EVP_CIPHER_CTX_free(ctx);

		enc_key.assign(dec, 32);
		mac_key.assign(dec + 32, 32);

		db_set_blob(0, m_szModuleName, DBKEY_ENC_KEY, enc_key.data(), (int)enc_key.length());
		db_set_blob(0, m_szModuleName, DBKEY_MAC_KEY, mac_key.data(), (int)mac_key.length());
	}

	return true;
}

/////////////////////////////////////////////////////////////////////////////////////////

void WhatsAppProto::RestoreSession()
{
	ptrA szClient(getStringA(DBKEY_CLIENT_TOKEN)), szServer(getStringA(DBKEY_SERVER_TOKEN));
	if (szClient == nullptr || szServer == nullptr) {
		ShutdownSession();
		return;
	}

	CMStringA payload(FORMAT, "[\"admin\",\"login\",\"%s\",\"%s\",\"%s\",\"takeover\"]", szClient.get(), szServer.get(), m_szClientId.c_str());
	WSSend(payload, &WhatsAppProto::OnRestoreSession);
}

void WhatsAppProto::OnRestoreSession(const JSONNode &root)
{
	int status = root["status"].as_int();
	if (status != 200) {
		debugLogA("Attempt to restore session failed with error %d", status);
		ShutdownSession();
		return;
	}
}

/////////////////////////////////////////////////////////////////////////////////////////

void WhatsAppProto::ShutdownSession()
{
	if (m_bTerminated)
		return;

	debugLogA("WhatsAppProto::ShutdownSession");

	// shutdown all resources
	if (m_hServerConn)
		Netlib_Shutdown(m_hServerConn);

	OnLoggedOut();
}

/////////////////////////////////////////////////////////////////////////////////////////

void WhatsAppProto::StartSession()
{
	CMStringA payload(FORMAT, "[\"admin\",\"init\",[0,3,4940],[\"Windows\",\"Chrome\",\"10\"],\"%s\",true]", m_szClientId.c_str());
	WSSend(payload, &WhatsAppProto::OnStartSession);
}

void WhatsAppProto::OnStartSession(const JSONNode &root)
{
	int status = root["status"].as_int();
	if (status != 200) {
		debugLogA("Session start failed with error %d", status);
		ShutdownSession();
		return;
	}

	CMStringA ref = root["ref"].as_mstring();
	ShowQrCode(ref);
}

/////////////////////////////////////////////////////////////////////////////////////////
// gateway worker thread

void WhatsAppProto::ServerThread(void *)
{
	while (ServerThreadWorker())
		;
	ShutdownSession();
}

bool WhatsAppProto::ServerThreadWorker()
{
	NETLIBHTTPHEADER hdrs[] =
	{
		{ "Origin", "https://web.whatsapp.com" },
		{ 0, 0 }
	};

	NLHR_PTR pReply(WebSocket_Connect(m_hNetlibUser, "web.whatsapp.com/ws", hdrs));
	if (pReply == nullptr) {
		debugLogA("Server connection failed, exiting");
		return false;
	}

	if (pReply->resultCode != 101)
		return false;

	debugLogA("Server connection succeeded");
	m_hServerConn = pReply->nlc;
	m_iLoginTime = time(0);
	m_szClientToken = getMStringA(DBKEY_CLIENT_TOKEN);
	getBlob(DBKEY_ENC_KEY, enc_key);
	getBlob(DBKEY_MAC_KEY, mac_key);

	if (m_szClientToken.IsEmpty() || mac_key.isEmpty() || enc_key.isEmpty())
		StartSession();
	else
		RestoreSession();

	bool bExit = false;
	int offset = 0;
	MBinBuffer netbuf;

	while (!bExit) {
		if (m_bTerminated)
			break;

		unsigned char buf[2048];
		int bufSize = Netlib_Recv(m_hServerConn, (char *)buf + offset, _countof(buf) - offset, MSG_NODUMP);
		if (bufSize == 0) {
			debugLogA("Gateway connection gracefully closed");
			bExit = !m_bTerminated;
			break;
		}
		if (bufSize < 0) {
			debugLogA("Gateway connection error, exiting");
			break;
		}

		WSHeader hdr;
		if (!WebSocket_InitHeader(hdr, buf, bufSize)) {
			offset += bufSize;
			continue;
		}
		offset = 0;

		debugLogA("Got packet: buffer = %d, opcode = %d, headerSize = %d, final = %d, masked = %d", bufSize, hdr.opCode, hdr.headerSize, hdr.bIsFinal, hdr.bIsMasked);

		// we have some additional data, not only opcode
		if ((size_t)bufSize > hdr.headerSize) {
			size_t currPacketSize = bufSize - hdr.headerSize;
			netbuf.append(buf, bufSize);
			while (currPacketSize < hdr.payloadSize) {
				int result = Netlib_Recv(m_hServerConn, (char *)buf, _countof(buf), MSG_NODUMP);
				if (result == 0) {
					debugLogA("Gateway connection gracefully closed");
					bExit = !m_bTerminated;
					break;
				}
				if (result < 0) {
					debugLogA("Gateway connection error, exiting");
					break;
				}
				currPacketSize += result;
				netbuf.append(buf, result);
			}
		}

		// read all payloads from the current buffer, one by one
		size_t prevSize = 0;
		while (true) {
			switch (hdr.opCode) {
			case 1: // json packet
				if (hdr.bIsFinal) {
					// process a packet here
					CMStringA szJson(netbuf.data() + hdr.headerSize, (int)hdr.payloadSize);
					debugLogA("JSON received:\n%s", szJson.c_str());

					int pos = szJson.Find(',');
					if (pos != -1) {
						CMStringA szPrefix = szJson.Left(pos);
						szJson.Delete(0, pos+1);

						JSONNode root = JSONNode::parse(szJson);
						if (root) {
							int sessId, pktId;
							if (sscanf(szPrefix, "%d.--%d,", &sessId, &pktId) == 2) {
								auto *pReq = m_arPacketQueue.find((WARequest *)&pktId);
								if (pReq != nullptr) {
									(this->*pReq->pHandler)(root);
								}
							}
							else ProcessPacket(root);
						}
					}
				}
				break;

			case 2: // binary packet
				break;

			case 8: // close
				debugLogA("server required to exit");
				bExit = true; // simply reconnect, don't exit
				break;

			case 9: // ping
				debugLogA("ping received");
				Netlib_Send(m_hServerConn, (char *)buf + hdr.headerSize, bufSize - int(hdr.headerSize), 0);
				break;
			}

			if (hdr.bIsFinal)
				netbuf.remove(hdr.headerSize + hdr.payloadSize);

			if (netbuf.length() == 0)
				break;

			// if we have not enough data for header, continue reading
			if (!WebSocket_InitHeader(hdr, netbuf.data(), netbuf.length()))
				break;

			// if we have not enough data for data, continue reading
			if (hdr.headerSize + hdr.payloadSize > netbuf.length())
				break;

			debugLogA("Got inner packet: buffer = %d, opcode = %d, headerSize = %d, payloadSize = %d, final = %d, masked = %d", netbuf.length(), hdr.opCode, hdr.headerSize, hdr.payloadSize, hdr.bIsFinal, hdr.bIsMasked);
			if (prevSize == netbuf.length()) {
				netbuf.remove(prevSize);
				debugLogA("dropping current packet, exiting");
				break;
			}

			prevSize = netbuf.length();
		}
	}

	Netlib_CloseHandle(m_hServerConn);
	m_hServerConn = nullptr;
	return bExit;
}

void WhatsAppProto::ProcessPacket(const JSONNode &root)
{
	CMStringA szType = root[(size_t)0].as_mstring();
	const JSONNode &content = root[1];

	if (szType == "Conn")
		ProcessConn(content);
	else if (szType == "Cmd")
		ProcessCmd(content);
}

void WhatsAppProto::ProcessCmd(const JSONNode &root)
{
	CMStringW wszType(root["type"].as_mstring());
	if (wszType == L"challenge") {
		CMStringA szChallenge(root["challenge"].as_mstring());
		if (!ProcessChallenge(szChallenge)) {
			ShutdownSession();
			return;
		}
	}
}

void WhatsAppProto::ProcessConn(const JSONNode &root)
{
	CloseQrDialog();

	m_szJid = root["wid"].as_mstring();
	setString(DBKEY_ID, m_szJid);

	CMStringA szSecret(root["secret"].as_mstring());
	if (!ProcessSecret(szSecret)) {
		ShutdownSession();
		return;
	}

	setWString(DBKEY_NICK, root["pushname"].as_mstring());
	setWString(DBKEY_CLIENT_TOKEN, root["clientToken"].as_mstring());
	setWString(DBKEY_SERVER_TOKEN, root["serverToken"].as_mstring());
	setWString(DBKEY_BROWSER_TOKEN, root["browserToken"].as_mstring());

	OnLoggedIn();
}