Migrating C# Membership Users To Django Without Resetting Passwords?

I've got a system that was partially written by someone else and is a complete maintenance nightmare for such a small app. I've finally been given changes which justifies just rewriting the horrible mess so I am moving it to Django.

Before I take the plunge, I've been trying to move over the password hash and salt into the Django auth tables [sha1]$[salt]$[hash] but can't get it to hash properly (resetting passwords isn't really an option).

Here is what I've been able to find out so far:

ASP.NET stores the hash as base64 string and uses a base64 salt (before hash) I can obviously reverse the base64 hash to a byte array Django uses a hexdigest, I tried BitConverter.ToString but they hash differently