I'm using Vagrant with apache2 and specifically the command
vagrant share --https 443
It all starts fine and provides a URL. When I access that URL I'm presented with a 400 error:
Bad Request
Your browser sent a request that this server could not understand. Apache/2.4.12 (Ubuntu) Server at *.vagrantshare.com Port 443
I have been accessing the vagrant machine using https just fine, but it doesn't seem to like to work with vagrant share.
This is a known Vagrant Share bug: https://github.com/webdevops/vagrant-docker-vm/issues/51
The only workarounds I've seen discussed are to use a custom domain or to use another product entirely (e.g. ngrok) to create the share. See the bug discussion here: https://github.com/mitchellh/vagrant/issues/5493#issuecomment-159792794
Vagrant Share docs for custom domains are here: https://atlas.hashicorp.com/help/vagrant/shares/custom-domains