PyCL Ransomware decryptor (Need decryption key, read: http://5kyc1ad.tistory.com/331)

PyCLDecryptor.cpp

/*
The MIT License (MIT)

Copyright (C) 2018 5kyc1ad

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/

#include <stdio.h>
#include <string>
#include <iostream>

#include <io.h>
#include <stdio.h>
#include <fcntl.h>
#include <Shlwapi.h>
#include <Windows.h>
#include <wincrypt.h>

#include "picosha256.h"

#define BLOCK_SIZE 65536

typedef struct _AES256KEYBLOB
{
	BLOBHEADER header;
	DWORD keySize;
	BYTE keyData[32];
} AES256KEYBLOB;

BOOL PyCLDecryptFile(const BYTE decryptKey[picosha2::k_digest_size], const std::wstring encryptFilePath);
unsigned int PyCLRecursivelyDecryptFiles(const BYTE decryptKey[picosha2::k_digest_size], std::wstring currentPath);

inline bool endswith(std::wstring const & value, std::wstring const & ending)
{
	if (ending.size() > value.size()) return false;
	return std::equal(ending.rbegin(), ending.rend(), value.rbegin());
}

int main()
{
	_setmode(_fileno(stdout), _O_U16TEXT);

	std::wstring encryptedPath;
	std::wcout << L"[*] Input path for Decryption : ";
	std::wcin >> encryptedPath;

	if (encryptedPath[encryptedPath.size() - 1] == L'\\')
		encryptedPath = encryptedPath.substr(0, encryptedPath.size() - 1);

	std::string inputKey;
	std::wcout << L"[*] Input Key : ";
	std::cin >> inputKey;

	BYTE decryptKey[picosha2::k_digest_size] = { 0, };
	picosha2::hash256(inputKey, decryptKey, decryptKey + picosha2::k_digest_size);
	std::wcout << L"[*] Decrypt Key : ";
	for (int i = 0; i < picosha2::k_digest_size; i++)
		wprintf(L"%02x ", decryptKey[i]);
	std::wcout << std::endl;

	DWORD dwAttribute = GetFileAttributes(encryptedPath.c_str());
	if (dwAttribute == INVALID_FILE_ATTRIBUTES) // Path not exists
	{
		std::wcerr << L"[-] Target path not found : " << encryptedPath << std::endl;
		return -1;
	}
	else if ((dwAttribute | FILE_ATTRIBUTE_DIRECTORY)) // Path is a directory
	{
		unsigned int decryptedCount = PyCLRecursivelyDecryptFiles(decryptKey, encryptedPath);
		std::wcout << L"[*] Successfully Decrypted File Count : " << decryptedCount << std::endl;
	}
	else // Path is a file
	{
		if(PyCLDecryptFile(decryptKey, encryptedPath))
			std::wcout << L"[+] Success : " << encryptedPath << std::endl;
		else
			std::wcout << L"[-] Failed  : " << encryptedPath << std::endl;
	}

	return 0;
}

BOOL PyCLDecryptFile(const BYTE decryptKey[picosha2::k_digest_size], const std::wstring encryptedFilePath)
{
	if (PathFileExists(encryptedFilePath.c_str()) == FALSE)
	{
		std::wcerr << L"[-] Target file not found : " << encryptedFilePath << std::endl;
		return FALSE;
	}

	std::wstring decryptFilePath = encryptedFilePath.substr(0, encryptedFilePath.find_last_of(L'.'));
	HANDLE hDecryptFile;
	if ((hDecryptFile = CreateFile(decryptFilePath.c_str(), GENERIC_ALL, FILE_SHARE_READ, NULL, CREATE_ALWAYS, NULL, NULL)) == INVALID_HANDLE_VALUE)
	{
		std::wcerr << L"[-] Can't get decrypt file handle : " << GetLastError() << L", " << decryptFilePath << std::endl;
		return FALSE;
	}

	const size_t chunkSize = BLOCK_SIZE;
	BYTE chunk[chunkSize] = { 0, };
	DWORD outLen = 0;
	HANDLE hEncryptFile;
	if ((hEncryptFile = CreateFile(encryptedFilePath.c_str(), GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, NULL, NULL)) == INVALID_HANDLE_VALUE)
	{
		std::wcerr << L"[-] Can't get encrypt file handle : " << GetLastError() << L", " << encryptedFilePath << std::endl;
		CloseHandle(hDecryptFile);
		DeleteFile(decryptFilePath.c_str());
		return FALSE;
	}

	BOOL bResult = FALSE;
	BYTE fileSize[16] = { 0, };
	if ((bResult = ReadFile(hEncryptFile, fileSize, 16, &outLen, NULL)) == FALSE)
	{
		std::wcerr << L"[-] Can't get filesize : " << GetLastError() << L", " << encryptedFilePath << std::endl;
		CloseHandle(hEncryptFile);
		CloseHandle(hDecryptFile);
		DeleteFile(decryptFilePath.c_str());
		return FALSE;
	}

	BYTE IV[16] = { 0, };
	if ((bResult = ReadFile(hEncryptFile, IV, 16, &outLen, NULL)) == FALSE)
	{
		std::wcerr << L"[-] Can't get IV : " << GetLastError() << L", " << encryptedFilePath << std::endl;
		CloseHandle(hEncryptFile);
		CloseHandle(hDecryptFile);
		DeleteFile(decryptFilePath.c_str());
		return FALSE;
	}

	HCRYPTPROV hProv;
	if (CryptAcquireContextW(&hProv, NULL, MS_ENH_RSA_AES_PROV, PROV_RSA_AES, CRYPT_VERIFYCONTEXT) == FALSE)
	{
		std::wcerr << L"[-] CryptAcquireContextW Error : " << GetLastError() << std::endl;
		CloseHandle(hEncryptFile);
		CloseHandle(hDecryptFile);
		DeleteFile(decryptFilePath.c_str());
		return FALSE;
	}

	AES256KEYBLOB blob;
	blob.header.bType = PLAINTEXTKEYBLOB;
	blob.header.bVersion = CUR_BLOB_VERSION;
	blob.header.reserved = 0;
	blob.header.aiKeyAlg = CALG_AES_256;
	blob.keySize = 32;
	memcpy(blob.keyData, decryptKey, picosha2::k_digest_size);

	HCRYPTKEY hKey;
	if (CryptImportKey(hProv, (BYTE*)&blob, sizeof(AES256KEYBLOB), NULL, 0, &hKey) == FALSE)
	{
		std::wcerr << L"[-] CryptImportKey Error : " << GetLastError() << std::endl;
		CryptReleaseContext(hProv, 0);
		CryptDestroyKey(hKey);
		CloseHandle(hEncryptFile);
		CloseHandle(hDecryptFile);
		DeleteFile(decryptFilePath.c_str());
		return FALSE;
	}
	
	DWORD dwMode = CRYPT_MODE_CBC;
	if (CryptSetKeyParam(hKey, KP_MODE, (BYTE*)&dwMode, 0) == FALSE)
	{
		std::wcerr << L"[-] CryptSetKeyParam Mode Error : " << GetLastError() << std::endl;
		CryptReleaseContext(hProv, 0);
		CryptDestroyKey(hKey);
		CloseHandle(hEncryptFile);
		CloseHandle(hDecryptFile);
		DeleteFile(decryptFilePath.c_str());
		return FALSE;
	}

	if (CryptSetKeyParam(hKey, KP_IV, IV, 0) == FALSE)
	{
		std::wcerr << L"[-] CryptSetKeyParam IV Error : " << GetLastError() << std::endl;
		CryptReleaseContext(hProv, 0);
		CryptDestroyKey(hKey);
		CloseHandle(hEncryptFile);
		CloseHandle(hDecryptFile);
		DeleteFile(decryptFilePath.c_str());
		return FALSE;
	}

	DWORD orgFileSize = GetFileSize(hEncryptFile, NULL) - 32;
	DWORD readTotalSize = 0;
	BOOL isFinal = FALSE;
	BOOL isSuccess = FALSE;
	while (bResult = ReadFile(hEncryptFile, chunk, chunkSize, &outLen, NULL))
	{
		if (outLen == 0)
			break;

		readTotalSize += outLen;
		if (readTotalSize == orgFileSize)
			isFinal = TRUE;

		// Custom Padding used, param Final must not be TRUE
		if (CryptDecrypt(hKey, NULL, FALSE, NULL, chunk, &outLen) == FALSE)
		{
			std::wcerr << L"[-] CryptDecrypt Error : " << GetLastError() << std::endl;
			break;
		}

		// Remove Padding
		for (outLen; chunk[outLen - 1] == '\x20'; outLen--);

		DWORD outWritten;
		if (WriteFile(hDecryptFile, chunk, outLen, &outWritten, NULL) == FALSE)
		{
			std::wcerr << L"[-] WriteFile Error : " << GetLastError() << std::endl;
			break;
		}

		if (isFinal)
		{
			isSuccess = TRUE;
			break;
		}
	}

	CryptDestroyKey(hKey);
	CryptReleaseContext(hProv, 0);
	CloseHandle(hEncryptFile);
	CloseHandle(hDecryptFile);

	if (isSuccess == FALSE)
		DeleteFile(decryptFilePath.c_str());

	return isSuccess;
}

unsigned int PyCLRecursivelyDecryptFiles(const BYTE decryptKey[picosha2::k_digest_size], std::wstring currentPath)
{
	std::wstring tmpCurrentPath = currentPath + L"\\*";
	std::wcout << L"[*] Finding target : " << currentPath << std::endl;
	unsigned int decryptedCount = 0;
	WIN32_FIND_DATA findData;
	HANDLE hFile = FindFirstFileEx(tmpCurrentPath.c_str(), FindExInfoMaxInfoLevel, &findData, FINDEX_SEARCH_OPS::FindExSearchNameMatch, NULL, FIND_FIRST_EX_LARGE_FETCH);
	if (hFile == INVALID_HANDLE_VALUE)
		hFile = FindFirstFile(tmpCurrentPath.c_str(), &findData);
	if (hFile == INVALID_HANDLE_VALUE)
	{
		std::wcout << L"[*] Can't search directory : " << GetLastError() << L", " << tmpCurrentPath << std::endl;
		return 0;
	}
	do
	{
		if (!wcscmp(findData.cFileName, L".") || !wcscmp(findData.cFileName, L".."))
			continue;
		if (findData.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
		{
			std::wstring targetPath = currentPath + L"\\" + findData.cFileName;
			decryptedCount += PyCLRecursivelyDecryptFiles(decryptKey, targetPath);
		}
		else if (endswith(findData.cFileName, L".impect"))
		{
			std::wstring targetPath = currentPath + L"\\" + findData.cFileName;
			BOOL isSuccess = PyCLDecryptFile(decryptKey, targetPath);
			if(isSuccess)
			{
				// std::wcout << L"[+] Success : " << targetPath << std::endl;
				decryptedCount++;
			}
			//else
			//	std::wcout << L"[-] Failed  : " << targetPath << std::endl;
		}
	} while (FindNextFile(hFile, &findData));
	FindClose(hFile);
	return decryptedCount;
}