A Terraform module for creating resilient bastion host using auto-scaling group (min=max=desired=1) and populate its
~/.ssh/authorized_keys
with public keys fetched from S3 bucket.
This module can append public keys, setup cron to update them and run additional commands at the end of setup. Note that if it is set up to update the keys, removing a key from the bucket will also remove it from the bastion host.
Only SSH access is allowed to the bastion host.
name
- Name (default,bastion
)instance_type
- Instance type (default,t2.micro
)instance_volume_size_gb
- The root volume size, in gigabytes (default,8
)ami
- AMI ID of Ubuntu (seesamples/ami.tf
)region
- Region (default,eu-west-1
)iam_instance_profile
- IAM instance profile which is allowed to access S3 bucket (seesamples/iam_s3_readonly.tf
)enable_monitoring
- Whether to enable detailed monitoring (default,true
)s3_bucket_name
- S3 bucket name which contains public keys (seesamples/s3_ssh_public_keys.tf
)s3_bucket_uri
– S3 URI which contains the public keys. If specified,s3_bucket_name
will be ignoredvpc_id
- VPC where bastion host should be createdsubnet_ids
- List of subnet IDs where auto-scaling should create instanceskeys_update_frequency
- How often to update keys. A cron timespec or an empty string to turn off (default)additional_user_data_script
- Additional user-data script to run at the endassociate_public_ip_address
- Whether to auto-assign public IP to the instance (by default -false
)eip
- EIP to put into EC2 tag (can be used with scripts like https://github.com/skymill/aws-ec2-assign-elastic-ip, default - empty value)key_name
- Launch configuration key name to be applied to created instance(s).allowed_cidr
- A list of CIDR Networks to allow ssh access to. Defaults to "0.0.0.0/0"allowed_ipv6_cidr
- A list of IPv6 CIDR Networks to allow ssh access to. Defaults to "::/0"allowed_security_groups
- A list of Security Group ID's to allow access to the bastion host (useful if bastion is deployed internally) Defaults to empty listextra_tags
- Optional a list of Key/Values Tags to be associated to the bastion host (see Interpolated Tags)apply_changes_immediately
- Whether to applyaws_launch_configuration
and update instances in autoscaling group (by default -false
)
- ssh_user - SSH user to login to bastion
- security_group_id - ID of the security group the bastion host is launched in.
- asg_id - The ID of the AutoScalingGroup the bastion host is launched within.
Basic example - In your terraform code add something like this:
module "bastion" {
source = "github.com/terraform-community-modules/tf_aws_bastion_s3_keys"
instance_type = "t2.micro"
ami = "ami-123456"
region = "eu-west-1"
iam_instance_profile = "s3_readonly"
s3_bucket_name = "public-keys-demo-bucket"
vpc_id = "vpc-123456"
subnet_ids = ["subnet-123456", "subnet-6789123", "subnet-321321"]
keys_update_frequency = "5,20,35,50 * * * *"
additional_user_data_script = "date"
}
If you want to assign EIP to instance launched by auto-scaling group you can provide desired eip
as module input
and then execute additional_user_data_script
which sets EIP. This way you can use Route53 with EIP, which will always
point to existing bastion instance. You will also need to add allow_associateaddress permission to iam_instance_profile (see samples/iam_allow_associateaddress.tf
):
module "bastion" {
// see above
eip = "${aws_eip.bastion.public_ip}"
iam_instance_profile = "s3_readonly-allow_associateaddress"
additional_user_data_script = <<EOF
REGION=$(curl -s http://169.254.169.254/latest/dynamic/instance-identity/document | grep region | awk -F\" '{print $4}')
INSTANCE_ID=$(curl -s http://169.254.169.254/latest/meta-data/instance-id)
aws ec2 associate-address --region $REGION --instance-id $INSTANCE_ID --allocation-id ${aws_eip.bastion.id}
EOF
}
resource "aws_eip" "bastion" {
vpc = true
}
resource "aws_route53_record" "bastion" {
zone_id = "..."
name = "bastion.example.com"
type = "A"
ttl = "3600"
records = ["${aws_eip.bastion.public_ip}"]
}
After you run terraform apply
you should be able to login to your bastion host like:
$ ssh ${module.bastion.ssh_user}@${aws_eip.bastion.public_ip}
or even like this:
$ ssh ubuntu@bastion.example.com
PS: In some cases you may consider adding flag -A
to ssh command to enable forwarding of the authentication agent connection.
##Authors
Created and maintained by Anton Babenko. Heavily inspired by hashicorp/atlas-examples.
Apache 2 Licensed. See LICENSE for full details.