C＃解密AES256加密文件

Question

I'm trying to decrypt a AES256 coded file but I'm getting a corrupted file output.

I have a 256bit (64 chars) hex AES key and a 128bit (32 chars) hex IV key that I'm converting to byte arrays with the following code.

public byte[] StringToByteArray(String hex)
{
    int NumberChars = hex.Length / 2;
    byte[] bytes = new byte[NumberChars];

    using (var sr = new StringReader(hex))
    {
        for (int i = 0; i < NumberChars; i++)
            bytes[i] =
              Convert.ToByte(new string(new char[2] { (char)sr.Read(), (char)sr.Read() }), 16);
    }

    return bytes;
}

The actual code I'm using for decryption is as follows.

public string DecryptCrypt7(byte[] data, string keyString, string ivString)
{
    byte[] aesHash = StringToByteArray(keyString);
    byte[] ivHash = StringToByteArray(ivString);

    try
    {
        using (var rijndaelManaged = new RijndaelManaged
        {
            Key = aesHash,
            IV = ivHash,
            Mode = CipherMode.CBC,
            Padding = PaddingMode.None,
            BlockSize = 128,
            KeySize = 256
        })
        {
            using (var memoryStream = new MemoryStream(data))
            {
                using (var cryptoStream = new CryptoStream(memoryStream, rijndaelManaged.CreateDecryptor(aesHash, ivHash), CryptoStreamMode.Read))
                {
                    return new StreamReader(cryptoStream).ReadToEnd();
                }
            }
        }
    }
    catch (CryptographicException e)
    {
        Console.WriteLine("A Cryptographic error occurred: {0}", e.Message);
        return null;
    }
}

It does decrypt the file, but it's clearly corrupted as I can't open it with an sqlite db viewer and see the tables, etc.

Decrypting it via CygWin using OpenSSL with the following command decrypts it properly and I can view all the tables in the file using a viewer.

openssl enc -aes-256-cbc -d -nosalt -nopad -bufsize 16384 -in file.crypt7 -K $(cat aes.txt) -iv $(cat iv.txt) > file.db

Answer 1

The problem is that your original data is binary data, but you're converting it to a string after you've decrypted it. So you just need to change your method to return a byte[] , then change the end of your decryption method to:

using (Stream encrypted = new MemoryStream(data),
       decrypted = new CryptoStream(encrypted, 
           rijndaelManaged.CreateDecryptor(aesHash, ivHash), CryptoStreamMode.Read),
       copy = new MemoryStream())
{
    decrypted.CopyTo(copy);
    return copy.ToArray();
}