Azure Application Gateway connection

For my client a new infrastructure is created in Azure portal. An IaaC (Infrastructure as a Code) approach is used for this via Terraform. This infrastructure contains vNets, subnets, securities and lots more of the azure artefacts and all of them created via Terraform. During this setup we had to deal with extra policies what we had to follow enforced by the Azure cloud admins. To test the Terraform securities among the subnets we decided to create an Application Gateway in a public subnet and a Linux Virtual Machine (VM) in a private subnet. The securities should allow the Application Gateway to set a connection to the VM. One of the policies that is set by the Azure cloud admins is that all the traffic should be encrypted. Also, the traffic inside Azure itself. Therefore, the Application Gateway can only call the VM via SSH over port 443.