Encrypt AES in C++(OpenSSL), decrypt in C#

Question

I have a system consists of two parts - c++ and c# application. This parts have a shared file which both could read and write. To defend my file from regular user I use AES encryption. C++ application use openSSL ctypto library AES implementation and C# application uses .NET Framework System.Security.Cryptography. For encryption I use CBC mode. Encryption/Decryption within certain application works good, but when I try to encrypt in one application(C++) and decrypt in another(C#) I face exception:

padding is invalid and cannot be removed

My test is performed by encryption 32 bytes of plain data in C++ application, then writing it in file then reading and decryption attempt in C# application. I make decryption in following manner:

using (AesCryptoServiceProvider aesEncryptor = new AesCryptoServiceProvider())
{
    aesEncryptor.Mode = CipherMode.CBC;
    aesEncryptor.Key = entropy;

    // it's the same in C++ application too
    byte[] iv = { 0x46, 0xb6, 0x02, 0x6a,
                  0x99, 0x21, 0x90, 0xde,
                  0xfd, 0xf4, 0x5b, 0x42,
                  0x94, 0xde, 0xa6, 0x23 }; 
    aesEncryptor.IV = iv;

    using (ICryptoTransform decryptor = aesEncryptor.CreateDecryptor(aesEncryptor.Key,
                                                                     aesEncryptor.IV))
    {
        byte[] decrypted;
        // Create the streams used for decryption.
        using (MemoryStream msDecrypt = new MemoryStream(encryptedData))
        {
            using (CryptoStream csDecrypt = new CryptoStream(msDecrypt,
                                                             decryptor,
                                                             CryptoStreamMode.Read))
            {
                decrypted = new byte[encryptedData.Length];
                var byteCount = csDecrypt.Read(decrypted, 0, encryptedData.Length);
                return decrypted;

            }
        }
    }
}

I also provide full exception desciption:

$exception {System.Security.Cryptography.CryptographicException: padding is invalid and cannot be removed. in System.Security.Cryptography.CapiSymmetricAlgorithm.DepadBlock(Byte[] block, Int32 offset, Int32 count) in System.Security.Cryptography.CapiSymmetricAlgorithm.TransformFinalBlock(Byte[] inputBuffer, Int32 inputOffset, Int32 inputCount) in System.Security.Cryptography.CryptoStream.FlushFinalBlock() in System.Security.Cryptography.CryptoStream.Dispose(Boolean disposing)
в System.IO.Stream.Close() in System.IO.Stream.Dispose()

Answer 1

You don't give your encryption code, but the exception suggests that the padding mode used for encryption is not the same as the padding mode that is being used during decryption in C# (which will be the default padding mode: PaddingMode.PKCS7).

Check the padding mode being used when encrypting, and ensure that the same mode is used for decryption. The list of available modes in .NET is available here.