Is there a way to authenticate with DirectoryServices to LDAP using MD5?

Question

I'm using VS 2012, C#.NET and creating a form to authenticate through LDAP.

I have this code, and it's working well:

root = new DirectoryEntry(
                "LDAP://192.168.116.20:389",
                username,
                password
            );

Both username and password are plain-text.

But I want to create a "Remember password?" checkbox where I can save the username and password md5-hashed in a file.

So, how can I authenticate using the md5-hash with DirectoryEntry and LDAP?! Is it possible?

Answer 1

If you chose to encrypt the data to a a file, you should use the System.Security.ProtectedData class.

The data you encrypt can be bounded to the current user or the current machine that the encoding/decoding is taking place on.

There are two simple method you should use:

• Protect - Takes a byte array and encrypt the data.
• Unprotect - Takes an encrypted data and returns a byte array.

Examples:

private static void EncryptData(string data, Stream stream)
{
    if (stream.CanWrite == false)
            throw new IOException("Cannot write to stream.");
    var bytes = Encoding.UTF8.GetBytes(data);
    var encryptedBytes = ProtectedData.Protect(bytes, null, DataProtectionScope.CurrentUser);
    stream.Write(encryptedBytes , 0, encryptedBytes .Length);
}

private static string DecryptData(Stream stream)
{
    if (stream.CanRead == false)
            throw new IOException("Cannot read fromstream.");

    using (MemoryStream memoryStream = new MemoryStream())
    {
        stream.CopyTo(memoryStream);
        var encryptedBytes = memoryStream.ToArray();
        var decryptedBytes = ProtectedData.Unprotect(encryptedBytes, null, DataProtectionScope.CurrentUser)
        return Encoding.UTF8.GetString(decryptedBytes);
    }
}

Now in order to use these with a FileStream simply:

public static void Encrypt(string password)
{
    using (var fileStream = new FileStream(@"MyFile.dat", FileMode.Create))
    {
        EncryptData(password, fileStream);
        fileStream.Close();
    }
}

public static string Decrypt()
{
    string password;
    using (var fileStream = new FileStream(@"MyFile.dat", FileMode.Open))
    {
        password = DecryptData(fileStream);
        fileStream.Close();
    }
    return password;
}

By the way, if you want to increase the complexity of the encryption you can pass an Entropy to the Protect and Unprotect methods. For more information see: http://msdn.microsoft.com/en-us/library/system.security.cryptography.protecteddata.protect(v=vs.110).aspx