Greeting C# programmer! I try to build a DLL using C# to crypt and decrypt by VBS script a VBS file.
My code is this:
using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Security.Cryptography;
using System.IO;
namespace DELTAGE
{
[System.Runtime.InteropServices.ComVisible(true)]
[System.Runtime.InteropServices.ProgId("DELTAGE.DLL")]
[System.Runtime.InteropServices.Guid("aaaaaaaa-0000-bbbb-1111-cccccccccccccc")]
public class DeltaGeIO
{
// This constant string is used as a "salt" value for the PasswordDeriveBytes function calls.
// This size of the IV (in bytes) must = (keysize / 8). Default keysize is 256, so the IV must be
// 32 bytes long. Using a 16 character string here gives us 32 bytes when converted to a byte array.
private const string initVector = "aa00bb11cc22dd33";
// This constant is used to determine the keysize of the encryption algorithm.
private const int keysize = 256;
private string debug;
public string cryptDecryptScript(string nameFileToCrypt)
{
try
{
string prova = writeVBScriptEncrypt(nameFileToCrypt, "");
prova = writeVBScriptDecrypt("testCrypt.txt");
return prova;
}
catch
{
return debug;
}
}
public string writeVBScriptEncrypt(string nameFile, string nameScript)
{
byte[] bytes = System.IO.File.ReadAllBytes(nameFile);
string[] lines = new string[1];
lines[0] = this.EncryptBytes(bytes, "test");
try
{
System.IO.File.Delete("testCrypt.txt");
}
catch
{
debug = "WVBSSE - i cannot delete testCrypt.txt file";
}
System.IO.File.WriteAllLines("testCrypt.txt", lines);
return "OK file Encrypted";
}
public string writeVBScriptDecrypt(string nameFile)
{
byte[] bytes = System.IO.File.ReadAllBytes(nameFile);
string[] lines = new string[1];
lines[0] = this.DecryptBytes(bytes, "test");
System.IO.File.WriteAllLines("testDecrypt.vbs", lines);
try
{
System.IO.File.Delete("testCrypt.txt");
}
catch
{
debug = "WVBSSD - i cannot delete testCrypt.txt file";
}
return "OK file Decrypted";
}
private string Encrypt(string plainText, string passPhrase)
{
byte[] initVectorBytes = Encoding.UTF8.GetBytes(initVector);
byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);
PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null);
byte[] keyBytes = password.GetBytes(keysize / 8);
RijndaelManaged symmetricKey = new RijndaelManaged();
symmetricKey.Mode = CipherMode.CBC;
ICryptoTransform encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes);
MemoryStream memoryStream = new MemoryStream();
CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write);
cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
cryptoStream.FlushFinalBlock();
byte[] cipherTextBytes = memoryStream.ToArray();
memoryStream.Close();
cryptoStream.Close();
return Convert.ToBase64String(cipherTextBytes);
}
private string Decrypt(string cipherText, string passPhrase)
{
byte[] initVectorBytes = Encoding.ASCII.GetBytes(initVector);
byte[] cipherTextBytes = Convert.FromBase64String(cipherText);
PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null);
byte[] keyBytes = password.GetBytes(keysize / 8);
RijndaelManaged symmetricKey = new RijndaelManaged();
symmetricKey.Mode = CipherMode.CBC;
ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes);
MemoryStream memoryStream = new MemoryStream(cipherTextBytes);
CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);
byte[] plainTextBytes = new byte[cipherTextBytes.Length];
int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
memoryStream.Close();
cryptoStream.Close();
return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
}
private string EncryptBytes(byte[] plainText, string passPhrase)
{
byte[] initVectorBytes = Encoding.UTF8.GetBytes(initVector);
byte[] plainTextBytes = plainText;
PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null);
byte[] keyBytes = password.GetBytes(keysize / 8);
RijndaelManaged symmetricKey = new RijndaelManaged();
symmetricKey.Mode = CipherMode.CBC;
ICryptoTransform encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes);
MemoryStream memoryStream = new MemoryStream();
CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write);
cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
cryptoStream.FlushFinalBlock();
byte[] cipherTextBytes = memoryStream.ToArray();
memoryStream.Close();
cryptoStream.Close();
return Convert.ToBase64String(cipherTextBytes);
}
private string DecryptBytes(byte[] cipherText, string passPhrase)
{
byte[] initVectorBytes = Encoding.ASCII.GetBytes(initVector);
byte[] cipherTextBytes = cipherText;
PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null);
byte[] keyBytes = password.GetBytes(keysize / 8);
RijndaelManaged symmetricKey = new RijndaelManaged();
symmetricKey.Mode = CipherMode.CBC;
ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes);
MemoryStream memoryStream = new MemoryStream(cipherTextBytes);
CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);
byte[] plainTextBytes = new byte[cipherTextBytes.Length];
debug = "here 1";
int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
debug = "here 1";
memoryStream.Close();
debug = "here 3" + decryptedByteCount.ToString();
cryptoStream.Close();
debug = "here 4";
return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
}
}
}
So, if i try to econde and decode a string using Encrypt and Decrypt it work fine.
But if i try to encrypt a file and decrypt crypted file using EncryptBytes and DecryptBytes i have an error to this code line:
int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
Any Ideas? Thanks
P.s. VBS code to call dll is this:
Dim mObj, strResult
set mObj = CreateObject("DELTAGE.DLL")
strResult = mObj.cryptDecryptScript("file.vbs")
MsgBox "Result: " + strResult
Before you create your file, you convert the "encrypted" bytes to a base64 string. When you read this file, you don't convert back the base64 string to the "encrypted" bytes.
To solve your problem you could update your WriteVBScriptDecrypt method like this:
public string writeVBScriptDecrypt(string nameFile)
{
var base64EncryptedBytes = File.ReadAllText(nameFile);
byte[] bytes = Convert.FromBase64String(base64EncryptedBytes);
...
}
A better way is to get rid of the Base64 conversion, you can write the bytes directly to a file instead of converting it to a base64 string first.
You should also consider the using {} statement to make sure that everything is disposed nicely.
public class DeltaGeIO
{
// This constant string is used as a "salt" value for the PasswordDeriveBytes function calls.
// This size of the IV (in bytes) must = (keysize / 8). Default keysize is 256, so the IV must be
// 32 bytes long. Using a 16 character string here gives us 32 bytes when converted to a byte array.
private const string initVector = "aa00bb11cc22dd33";
// This constant is used to determine the keysize of the encryption algorithm.
private const int keysize = 256;
private string debug;
public string cryptDecryptScript(string nameFileToCrypt)
{
try
{
string prova = writeVBScriptEncrypt(nameFileToCrypt, "");
prova = writeVBScriptDecrypt("testCrypt.txt");
return prova;
}
catch
{
return debug;
}
}
public string writeVBScriptEncrypt(string nameFile, string nameScript)
{
byte[] bytes = System.IO.File.ReadAllBytes(nameFile);
byte[] encryptedBytes = this.EncryptBytes(bytes, "test");
try
{
File.Delete("testCrypt.txt");
}
catch
{
debug = "WVBSSE - i cannot delete testCrypt.txt file";
}
File.WriteAllBytes("testCrypt.txt", encryptedBytes);
return "OK file Encrypted";
}
public string writeVBScriptDecrypt(string nameFile)
{
var encryptedBytes = File.ReadAllBytes(nameFile);
byte[] decryptedBytes = this.DecryptBytes(encryptedBytes, "test");
System.IO.File.WriteAllBytes("testDecrypt.vbs", decryptedBytes);
try
{
System.IO.File.Delete("testCrypt.txt");
}
catch
{
debug = "WVBSSD - i cannot delete testCrypt.txt file";
}
return "OK file Decrypted";
}
private byte[] EncryptBytes(byte[] plainText, string passPhrase)
{
byte[] initVectorBytes = Encoding.UTF8.GetBytes(initVector);
byte[] plainTextBytes = plainText;
PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null);
byte[] keyBytes = password.GetBytes(keysize / 8);
using (RijndaelManaged symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC})
{
using (ICryptoTransform encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes))
using (MemoryStream memoryStream = new MemoryStream())
using (CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
{
cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
cryptoStream.FlushFinalBlock();
byte[] cipherTextBytes = memoryStream.ToArray();
return cipherTextBytes;
}
}
}
private byte[] DecryptBytes(byte[] cipherText, string passPhrase)
{
byte[] initVectorBytes = Encoding.UTF8.GetBytes(initVector);
byte[] cipherTextBytes = cipherText;
PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null);
byte[] keyBytes = password.GetBytes(keysize / 8);
using (RijndaelManaged symmetricKey = new RijndaelManaged(){Mode = CipherMode.CBC})
using (ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, initVectorBytes))
using (MemoryStream memoryStream = new MemoryStream(cipherTextBytes))
using (CryptoStream cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read))
{
byte[] buffer = new byte[cipherTextBytes.Length];
int decryptedByteCount = cryptoStream.Read(buffer, 0, buffer.Length);
byte[] copy = new byte[decryptedByteCount];
Array.Copy(buffer, copy, decryptedByteCount);
return copy;
}
}
}