Is there a way to build ebs by packer for LDAP restricted ssh login

I want to build the ebs ami from source ami which restricted by LDAP.
So when I build with packer, I got ssh handshake failed error.
I try to ssh login to packer builder instance, but I got password prompt because of ldap restriction and can't login.
How can I build and provision with ssh login with packer?

{
  "builders": [{
    "type": "amazon-ebs",
    "access_key": "{key}",
    "secret_key": "{key}",
    "region": "{region}",
    "source_ami": "{myami}",
    "instance_type": "m3.medium",
    "ssh_username": "ec2-user",
    "ssh_timeout": "10m",
    "ami_name": "ami_from_packer {{timestamp}}",
    "iam_instance_profile": "packer"
  }]
}