Configure Vagrant to ignore SSL certificate behind corporate proxy.

The first case

The first case is to download Vagrant box.

$ vagrant box add --provider virtualbox debian/buster64

The box 'debian/buster64' could not be found or
could not be accessed in the remote catalog. If this is a private
box on HashiCorp's Vagrant Cloud, please verify you're logged in via
'vagrant login'. Also, please double-check the name. The expanded
URL and error message are shown below:
URL: ["https://vagrantcloud.com/debian/buster64"]
Error: SSL certificate problem: self signed certificate in certificate chain

The solution is to add --insecure parameter.

$ vagrant box add --provider virtualbox --insecure debian/buster64

==> box: Loading metadata for box 'debian/buster64'
    box: URL: https://vagrantcloud.com/debian/buster64
==> box: Adding box 'debian/buster64' (v10.4.0) for provider: virtualbox
    box: Downloading: https://vagrantcloud.com/debian/boxes/buster64/versions/10.4.0/providers/virtualbox.box
    box: Download redirected to host: vagrantcloud-files-production.s3.amazonaws.com
==> box: Successfully added box 'debian/buster64' (v10.4.0) for 'virtualbox'!

The second case

The second case is to download Vagrant plugin.

$ vagrant plugin install vagrant-proxyconf

Installing the 'vagrant-proxyconf' plugin. This can take a few minutes...
ERROR: SSL verification error at depth 1: self signed certificate in certificate chain (19)
ERROR: Root certificate is not trusted (/O=sleeplessbeastie.eu/CN=*.sleeplessbeastie.eu)
Vagrant failed to load a configured plugin source. This can be caused
by a variety of issues including: transient connectivity issues, proxy
filtering rejecting access to a configured plugin source, or a configured
plugin source not responding correctly. Please review the error message
below to help resolve the issue:
  SSL_connect returned=1 errno=0 state=error: certificate verify failed (https://api.rubygems.org/specs.4.8.gz)
Source: https://rubygems.org/

Bypass these SSL certificate checks.

$ echo :ssl_verify_mode: 0 | tee ~/.gemrc

:ssl_verify_mode: 0

Bypass these SSL certificate checks.

$ vagrant plugin install vagrant-proxyconf

Installing the 'vagrant-proxyconf' plugin. This can take a few minutes...
ERROR: SSL verification error at depth 1: self signed certificate in certificate chain (19)
ERROR: Root certificate is not trusted (/O=sleeplessbeastie.eu/CN=*.sleeplessbeastie.eu)
ERROR: SSL verification error at depth 1: self signed certificate in certificate chain (19)
ERROR: Root certificate is not trusted (/O=sleeplessbeastie.eu/CN=*.sleeplessbeastie.eu)
Fetching vagrant-libvirt-0.1.2.gem
Fetching vagrant-proxyconf-2.0.10.gem
Successfully installed 'vagrant=proxyconf (2.0.10)'!