How to access local apt repository behind https?

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http://stackoverflow.com – I have a couple of local apt repositories which are setup using reprepro. I want to make them available on the local network and I've got next to everything setup. However the repos are sitting behind https (this is out of my control) so when I try to pull from them from another server the request just hangs and I think it's because it is waiting for the username / password to be supplied. I'm not sure how to supply these. Do they go in the sources.list file on the pulling server? What would the format be? Cheers (HowTos)