OK, dug in some more... I've eventually managed to get it sort of working. in src/future/http/HTTPSFuture.php, you have this code:

Looking further, google auth works up until this URL is requested in my browser: https://phabricator.tvsquared.com/auth/login/google:google.com/?state=STATE&code=CODE

Here's another...

Also just seen this:

Hi, I've accidentally fixed it. I needed to copy some tickets across from the defunct system to our new live system, so I did:

Ok, I've reverted our prod system to last night's snapshots of mysql + root disk and it is back to working again (with zero changes in AWS).

We had to downgrade libphutil+phabricator to get it working again, so they're currently on the commit immediately prior to the v4 stuff.

Oh, we're authenticating using an accesskey/secretkey for an IAM user, if that makes a difference.

Hi, here you go: