/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 *
 * (c) ZeroTier, Inc.
 * https://www.zerotier.com/
 */

#include "WinDNSHelper.hpp"

#include <WbemIdl.h>
#include <comdef.h>
#include <sstream>
#include <string>
#include <strsafe.h>
#include <vector>

#define MAX_KEY_LENGTH 255
#define MAX_VALUE_NAME 16383

namespace ZeroTier {

BOOL RegDelnodeRecurse(HKEY hKeyRoot, LPTSTR lpSubKey)
{
	LPTSTR lpEnd;
	LONG lResult;
	DWORD dwSize;
	TCHAR szName[MAX_PATH];
	HKEY hKey;
	FILETIME ftWrite;

	// First, see if we can delete the key without having
	// to recurse.

	lResult = RegDeleteKey(hKeyRoot, lpSubKey);

	if (lResult == ERROR_SUCCESS)
		return TRUE;

	lResult = RegOpenKeyEx(hKeyRoot, lpSubKey, 0, KEY_READ, &hKey);

	if (lResult != ERROR_SUCCESS) {
		if (lResult == ERROR_FILE_NOT_FOUND) {
			return TRUE;
		}
		else {
			return FALSE;
		}
	}

	// Check for an ending slash and add one if it is missing.

	lpEnd = lpSubKey + lstrlen(lpSubKey);

	if (*(lpEnd - 1) != TEXT('\\')) {
		*lpEnd = TEXT('\\');
		lpEnd++;
		*lpEnd = TEXT('\0');
	}

	// Enumerate the keys

	dwSize = MAX_PATH;
	lResult = RegEnumKeyEx(hKey, 0, szName, &dwSize, NULL, NULL, NULL, &ftWrite);

	if (lResult == ERROR_SUCCESS) {
		do {
			*lpEnd = TEXT('\0');
			StringCchCat(lpSubKey, MAX_PATH * 2, szName);

			if (! RegDelnodeRecurse(hKeyRoot, lpSubKey)) {
				break;
			}

			dwSize = MAX_PATH;

			lResult = RegEnumKeyEx(hKey, 0, szName, &dwSize, NULL, NULL, NULL, &ftWrite);

		} while (lResult == ERROR_SUCCESS);
	}

	lpEnd--;
	*lpEnd = TEXT('\0');

	RegCloseKey(hKey);

	// Try again to delete the key.

	lResult = RegDeleteKey(hKeyRoot, lpSubKey);

	if (lResult == ERROR_SUCCESS)
		return TRUE;

	return FALSE;
}

//*************************************************************
//
//  RegDelnode()
//
//  Purpose:    Deletes a registry key and all its subkeys / values.
//
//  Parameters: hKeyRoot    -   Root key
//              lpSubKey    -   SubKey to delete
//
//  Return:     TRUE if successful.
//              FALSE if an error occurs.
//
//*************************************************************

BOOL RegDelnode(HKEY hKeyRoot, LPCTSTR lpSubKey)
{
	TCHAR szDelKey[MAX_PATH * 2];

	StringCchCopy(szDelKey, MAX_PATH * 2, lpSubKey);
	return RegDelnodeRecurse(hKeyRoot, szDelKey);
}
std::vector<std::string> getSubKeys(const char* key)
{
	std::vector<std::string> subkeys;
	HKEY hKey;
	if (RegOpenKeyExA(HKEY_LOCAL_MACHINE, key, 0, KEY_READ, &hKey) == ERROR_SUCCESS) {
		TCHAR achKey[MAX_KEY_LENGTH];		   // buffer for subkey name
		DWORD cbName;						   // size of name string
		TCHAR achClass[MAX_PATH] = TEXT("");   // buffer for class name
		DWORD cchClassName = MAX_PATH;		   // size of class string
		DWORD cSubKeys = 0;					   // number of subkeys
		DWORD cbMaxSubKey;					   // longest subkey size
		DWORD cchMaxClass;					   // longest class string
		DWORD cValues;						   // number of values for key
		DWORD cchMaxValue;					   // longest value name
		DWORD cbMaxValueData;				   // longest value data
		DWORD cbSecurityDescriptor;			   // size of security descriptor
		FILETIME ftLastWriteTime;			   // last write time

		DWORD i, retCode;

		TCHAR achValue[MAX_VALUE_NAME];
		DWORD cchValue = MAX_VALUE_NAME;

		retCode = RegQueryInfoKey(
			hKey,					 // key handle
			achClass,				 // buffer for class name
			&cchClassName,			 // size of class string
			NULL,					 // reserved
			&cSubKeys,				 // number of subkeys
			&cbMaxSubKey,			 // longest subkey size
			&cchMaxClass,			 // longest class string
			&cValues,				 // number of values for this key
			&cchMaxValue,			 // longest value name
			&cbMaxValueData,		 // longest value data
			&cbSecurityDescriptor,	 // security descriptor
			&ftLastWriteTime);		 // last write time

		for (i = 0; i < cSubKeys; ++i) {
			cbName = MAX_KEY_LENGTH;
			retCode = RegEnumKeyEx(hKey, i, achKey, &cbName, NULL, NULL, NULL, &ftLastWriteTime);
			if (retCode == ERROR_SUCCESS) {
				subkeys.push_back(achKey);
			}
		}
	}
	RegCloseKey(hKey);
	return subkeys;
}

std::vector<std::string> getValueList(const char* key)
{
	std::vector<std::string> values;
	HKEY hKey;
	if (RegOpenKeyExA(HKEY_LOCAL_MACHINE, key, 0, KEY_READ, &hKey) == ERROR_SUCCESS) {
		TCHAR achKey[MAX_KEY_LENGTH];		   // buffer for subkey name
		DWORD cbName;						   // size of name string
		TCHAR achClass[MAX_PATH] = TEXT("");   // buffer for class name
		DWORD cchClassName = MAX_PATH;		   // size of class string
		DWORD cSubKeys = 0;					   // number of subkeys
		DWORD cbMaxSubKey;					   // longest subkey size
		DWORD cchMaxClass;					   // longest class string
		DWORD cValues;						   // number of values for key
		DWORD cchMaxValue;					   // longest value name
		DWORD cbMaxValueData;				   // longest value data
		DWORD cbSecurityDescriptor;			   // size of security descriptor
		FILETIME ftLastWriteTime;			   // last write time

		DWORD i, retCode;

		TCHAR achValue[MAX_VALUE_NAME];
		DWORD cchValue = MAX_VALUE_NAME;

		retCode = RegQueryInfoKey(
			hKey,					 // key handle
			achClass,				 // buffer for class name
			&cchClassName,			 // size of class string
			NULL,					 // reserved
			&cSubKeys,				 // number of subkeys
			&cbMaxSubKey,			 // longest subkey size
			&cchMaxClass,			 // longest class string
			&cValues,				 // number of values for this key
			&cchMaxValue,			 // longest value name
			&cbMaxValueData,		 // longest value data
			&cbSecurityDescriptor,	 // security descriptor
			&ftLastWriteTime);		 // last write time

		for (i = 0, retCode = ERROR_SUCCESS; i < cValues; ++i) {
			cchValue = MAX_VALUE_NAME;
			achValue[0] = '\0';
			retCode = RegEnumValue(hKey, i, achValue, &cchValue, NULL, NULL, NULL, NULL);
			if (retCode == ERROR_SUCCESS) {
				values.push_back(achValue);
			}
		}
	}
	RegCloseKey(hKey);
	return values;
}

std::pair<bool, std::string> WinDNSHelper::hasDNSConfig(uint64_t nwid)
{
	char networkStr[20] = { 0 };
	sprintf(networkStr, "%.16llx", nwid);

	const char* baseKey = "SYSTEM\\CurrentControlSet\\Services\\Dnscache\\Parameters\\DnsPolicyConfig";
	auto subkeys = getSubKeys(baseKey);
	for (auto it = subkeys.begin(); it != subkeys.end(); ++it) {
		char sub[MAX_KEY_LENGTH] = { 0 };
		sprintf(sub, "%s\\%s", baseKey, it->c_str());
		auto dnsRecords = getValueList(sub);
		for (auto it2 = dnsRecords.begin(); it2 != dnsRecords.end(); ++it2) {
			if ((*it2) == "Comment") {
				HKEY hKey;
				if (RegOpenKeyExA(HKEY_LOCAL_MACHINE, sub, 0, KEY_READ, &hKey) == ERROR_SUCCESS) {
					char buf[16384] = { 0 };
					DWORD size = sizeof(buf);
					DWORD retCode = RegGetValueA(HKEY_LOCAL_MACHINE, sub, it2->c_str(), RRF_RT_REG_SZ, NULL, &buf, &size);
					if (retCode == ERROR_SUCCESS) {
						if (std::string(networkStr) == std::string(buf)) {
							RegCloseKey(hKey);
							return std::make_pair(true, std::string(sub));
						}
					}
					else {
					}
				}
				RegCloseKey(hKey);
			}
		}
	}

	return std::make_pair(false, std::string());
}

void WinDNSHelper::setDNS(uint64_t nwid, const char* domain, const std::vector<InetAddress>& servers)
{
	auto hasConfig = hasDNSConfig(nwid);

	std::stringstream ss;
	for (auto it = servers.begin(); it != servers.end(); ++it) {
		char ipaddr[256] = { 0 };
		ss << it->toIpString(ipaddr);
		if ((it + 1) != servers.end()) {
			ss << ";";
		}
	}
	std::string serverValue = ss.str();

	if (hasConfig.first) {
		// update existing config
		HKEY dnsKey;
		if (RegOpenKeyExA(HKEY_LOCAL_MACHINE, hasConfig.second.c_str(), 0, KEY_READ | KEY_WRITE, &dnsKey) == ERROR_SUCCESS) {
			auto retCode = RegSetKeyValueA(dnsKey, NULL, "GenericDNSServers", REG_SZ, serverValue.data(), (DWORD)serverValue.length());
			if (retCode != ERROR_SUCCESS) {
				fprintf(stderr, "Error writing dns servers: %d\n", retCode);
			}
		}
	}
	else {
		// add new config
		const char* baseKey = "SYSTEM\\CurrentControlSet\\Services\\Dnscache\\Parameters\\DnsPolicyConfig";
		GUID guid;
		CoCreateGuid(&guid);
		wchar_t guidTmp[128] = { 0 };
		char guidStr[128] = { 0 };
		StringFromGUID2(guid, guidTmp, 128);
		wcstombs(guidStr, guidTmp, 128);
		char fullKey[MAX_KEY_LENGTH] = { 0 };
		sprintf(fullKey, "%s\\%s", baseKey, guidStr);
		HKEY dnsKey;
		RegCreateKeyA(HKEY_LOCAL_MACHINE, fullKey, &dnsKey);
		if (RegOpenKeyExA(HKEY_LOCAL_MACHINE, fullKey, 0, KEY_READ | KEY_WRITE, &dnsKey) == ERROR_SUCCESS) {
			char nwString[32] = { 0 };
			sprintf(nwString, "%.16llx", nwid);
			RegSetKeyValueA(dnsKey, NULL, "Comment", REG_SZ, nwString, strlen(nwString));

			DWORD configOpts = 8;
			RegSetKeyValueA(dnsKey, NULL, "ConfigOptions", REG_DWORD, &configOpts, sizeof(DWORD));
			RegSetKeyValueA(dnsKey, NULL, "DisplayName", REG_SZ, "", 0);
			RegSetKeyValueA(dnsKey, NULL, "GenericDNSServers", REG_SZ, serverValue.data(), serverValue.length());
			RegSetKeyValueA(dnsKey, NULL, "IPSECCARestriction", REG_SZ, "", 0);
			std::string d = "." + std::string(domain);
			RegSetKeyValueA(dnsKey, NULL, "Name", REG_MULTI_SZ, d.data(), d.length());
			DWORD version = 2;
			RegSetKeyValueA(dnsKey, NULL, "Version", REG_DWORD, &version, sizeof(DWORD));
		}
	}
}

void WinDNSHelper::removeDNS(uint64_t nwid)
{
	auto hasConfig = hasDNSConfig(nwid);
	if (hasConfig.first) {
		RegDelnode(HKEY_LOCAL_MACHINE, hasConfig.second.c_str());
	}
}

}	// namespace ZeroTier
