terraform-aws-ssm-agent

A Terraform Module to create a simple, autoscaled SSM Agent EC2 instance along with its corresponding IAM instance profile. This is intended to be used with SSM Session Manager and other SSM functionality to replace the need for a Bastion host and further secure your cloud environment. This includes an SSM document to enable session logging to S3 and CloudWatch for auditing purposes.

Big shout out to the following projects which this project uses/depends on/mentions:

1. gjbae1212/gossm
2. cloudposse/terraform-null-label
3. cloudposse/terraform-aws-vpc
4. cloudposse/terraform-aws-dynamic-subnets
5. cloudposse/terraform-aws-kms-key
6. cloudposse/terraform-aws-s3-bucket
7. Cloud Posse's Terratest Setup.

Usage

Module Usage:

module "ssm_agent" {
  source     = "masterpointio/ssm-agent/aws"
  version    = "0.15.1"
  stage      = var.stage
  namespace  = var.namespace
  vpc_id     = module.vpc.vpc_id
  subnet_ids = module.subnets.private_subnet_ids
}

module "vpc" {
  source  = "cloudposse/vpc/aws"
  version = "2.1.0"

  namespace = var.namespace
  stage     = var.stage
  name      = var.name

  ipv4_primary_cidr_block          = "10.0.0.0/16"
  assign_generated_ipv6_cidr_block = true
}

module "subnets" {
  source    = "cloudposse/dynamic-subnets/aws"
  version   = "2.3.0"
  namespace = var.namespace
  stage     = var.stage

  availability_zones = var.availability_zones
  vpc_id             = module.vpc.vpc_id
  igw_id             = [module.vpc.igw_id]
  ipv4_cidr_block    = [module.vpc.vpc_cidr_block]
  ipv6_enabled       = var.ipv6_enabled
}

Connecting to your new SSM Agent:

INSTANCE_ID=$(aws autoscaling describe-auto-scaling-instances | jq --raw-output ".AutoScalingInstances | .[0] | .InstanceId")
aws ssm start-session --target $INSTANCE_ID

OR

Use the awesome gossm project.

Requirements

Name	Version
terraform	>= 1.0
aws	>= 5.0
time	>= 0.7

Providers

Name	Version
aws	5.37.0

Modules

Name	Source	Version
kms_key	cloudposse/kms-key/aws	0.12.1
logs_bucket	cloudposse/s3-bucket/aws	3.1.2
logs_label	cloudposse/label/null	0.25.0
role_label	cloudposse/label/null	0.25.0
this	cloudposse/label/null	0.25.0

Resources

Name	Type
aws_autoscaling_group.default	resource
aws_cloudwatch_log_group.session_logging	resource
aws_iam_instance_profile.default	resource
aws_iam_role.default	resource
aws_iam_role_policy.session_logging	resource
aws_iam_role_policy_attachment.default	resource
aws_launch_template.default	resource
aws_security_group.default	resource
aws_security_group_rule.allow_all_egress	resource
aws_ssm_document.session_logging	resource
aws_ami.amazon_linux_2	data source
aws_caller_identity.current	data source
aws_iam_policy_document.default	data source
aws_iam_policy_document.session_logging	data source
aws_region.current	data source
aws_s3_bucket.logs_bucket	data source

Inputs

Name	Description	Type	Default	Required
additional_security_group_ids	Security groups that will be attached to the app instances	list(string)	[]	no
additional_tag_map	Additional key-value pairs to add to each map in tags_as_list_of_maps. Not added to tags or id. This is for some rare cases where resources want additional configuration of tags and therefore take a list of maps with tag key, value, and additional configuration.	map(string)	{}	no
ami	The AMI to use for the SSM Agent EC2 Instance. If not provided, the latest Amazon Linux 2023 AMI will be used. Note: This will update periodically as AWS releases updates to their AL2023 AMI. Pin to a specific AMI if you would like to avoid these updates.	string	""	no
associate_public_ip_address	Associate public IP address	bool	null	no
attributes	ID element. Additional attributes (e.g. workers or cluster) to add to id, in the order they appear in the list. New attributes are appended to the end of the list. The elements of the list are joined by the delimiter and treated as a single ID element.	list(string)	[]	no
cloudwatch_retention_in_days	The number of days to retain session logs in CloudWatch. This is only relevant if the session_logging_enabled variable is true.	number	365	no
context	Single object for setting entire context at once. See description of individual variables for details. Leave string and numeric variables as null to use default value. Individual variable settings (non-null) override settings in context object, except for attributes, tags, and additional_tag_map, which are merged.	any	{ "additional_tag_map": {}, "attributes": [], "delimiter": null, "descriptor_formats": {}, "enabled": true, "environment": null, "id_length_limit": null, "label_key_case": null, "label_order": [], "label_value_case": null, "labels_as_tags": [ "unset" ], "name": null, "namespace": null, "regex_replace_chars": null, "stage": null, "tags": {}, "tenant": null }	no
create_run_shell_document	Whether or not to create the SSM-SessionManagerRunShell SSM Document.	bool	true	no
delimiter	Delimiter to be used between ID elements. Defaults to - (hyphen). Set to "" to use no delimiter at all.	string	null	no
descriptor_formats	Describe additional descriptors to be output in the descriptors output map. Map of maps. Keys are names of descriptors. Values are maps of the form {<br> format = string<br> labels = list(string)<br>} (Type is any so the map values can later be enhanced to provide additional options.) format is a Terraform format string to be passed to the format() function. labels is a list of labels, in order, to pass to format() function. Label values will be normalized before being passed to format() so they will be identical to how they appear in id. Default is {} (descriptors output will be empty).	any	{}	no
desired_capacity	Desired number of instances in the Auto Scaling Group	number	1	no
enabled	Set to false to prevent the module from creating any resources	bool	null	no
environment	ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT'	string	null	no
id_length_limit	Limit id to this many characters (minimum 6). Set to 0 for unlimited length. Set to null for keep the existing setting, which defaults to 0. Does not affect id_full.	number	null	no
instance_type	The instance type to use for the SSM Agent EC2 instance.	string	"t4g.nano"	no
key_pair_name	The name of the key-pair to associate with the SSM Agent instances. This can be (and probably should) left empty unless you specifically plan to use AWS-StartSSHSession.	string	null	no
label_key_case	Controls the letter case of the tags keys (label names) for tags generated by this module. Does not affect keys of tags passed in via the tags input. Possible values: lower, title, upper. Default value: title.	string	null	no
label_order	The order in which the labels (ID elements) appear in the id. Defaults to ["namespace", "environment", "stage", "name", "attributes"]. You can omit any of the 6 labels ("tenant" is the 6th), but at least one must be present.	list(string)	null	no
label_value_case	Controls the letter case of ID elements (labels) as included in id, set as tag values, and output by this module individually. Does not affect values of tags passed in via the tags input. Possible values: lower, title, upper and none (no transformation). Set this to title and set delimiter to "" to yield Pascal Case IDs. Default value: lower.	string	null	no
labels_as_tags	Set of labels (ID elements) to include as tags in the tags output. Default is to include all labels. Tags with empty values will not be included in the tags output. Set to [] to suppress all generated tags. Notes: The value of the name tag, if included, will be the id, not the name. Unlike other null-label inputs, the initial setting of labels_as_tags cannot be changed in later chained modules. Attempts to change it will be silently ignored.	set(string)	[ "default" ]	no
max_size	Maximum number of instances in the Auto Scaling Group	number	2	no
metadata_http_endpoint_enabled	Whether or not to enable the metadata http endpoint	bool	true	no
metadata_http_protocol_ipv6_enabled	Enable IPv6 metadata endpoint	bool	false	no
metadata_imdsv2_enabled	Whether or not the metadata service requires session tokens, also referred to as Instance Metadata Service Version 2 (IMDSv2).	bool	true	no
min_size	Minimum number of instances in the Auto Scaling Group	number	1	no
monitoring_enabled	Enable detailed monitoring of instance	bool	true	no
name	ID element. Usually the component or solution name, e.g. 'app' or 'jenkins'. This is the only ID element not also included as a tag. The "name" tag is set to the full id string. There is no tag with the value of the name input.	string	null	no
namespace	ID element. Usually an abbreviation of your organization name, e.g. 'eg' or 'cp', to help ensure generated IDs are globally unique	string	null	no
permissions_boundary	The ARN of the permissions boundary that will be applied to the SSM Agent role.	string	""	no
protect_from_scale_in	Allows setting instance protection for scale in actions on the ASG.	bool	false	no
regex_replace_chars	Terraform regular expression (regex) string. Characters matching the regex will be removed from the ID elements. If not set, "/[^a-zA-Z0-9-]/" is used to remove all characters other than hyphens, letters and digits.	string	null	no
region	The region to deploy the S3 bucket for session logs. If not supplied, the module will use the current region.	string	""	no
scale_in_protected_instances	Behavior when encountering instances protected from scale in are found. Available behaviors are Refresh, Ignore, and Wait. Default is Ignore.	string	"Ignore"	no
session_logging_bucket_name	The name of the S3 Bucket to ship session logs to. This will remove creation of an independent session logging bucket. This is only relevant if the session_logging_enabled variable is true.	string	""	no
session_logging_enabled	To enable CloudWatch and S3 session logging or not. Note this does not apply to SSH sessions as AWS cannot log those sessions.	bool	true	no
session_logging_encryption_enabled	To enable CloudWatch and S3 session logging encryption or not.	bool	true	no
session_logging_kms_key_alias	Alias name for session_logging KMS Key. This is only applied if 2 conditions are met: (1) session_logging_kms_key_arn is unset, (2) session_logging_encryption_enabled = true.	string	"alias/session_logging"	no
session_logging_kms_key_arn	BYO KMS Key instead of using the created KMS Key. The session_logging_encryption_enabled variable must still be true for this to be applied.	string	""	no
session_logging_ssm_document_name	Name for session_logging SSM document. This is only applied if 2 conditions are met: (1) session_logging_enabled = true, (2) create_run_shell_document = true.	string	"SSM-SessionManagerRunShell"	no
stage	ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release'	string	null	no
subnet_ids	The Subnet IDs which the SSM Agent will run in. These should be private subnets.	list(string)	n/a	yes
tags	Additional tags (e.g. {'BusinessUnit': 'XYZ'}). Neither the tag keys nor the tag values will be modified by this module.	map(string)	{}	no
tenant	ID element _(Rarely used, not included by default)_. A customer identifier, indicating who this instance of a resource is for	string	null	no
user_data	The user_data to use for the SSM Agent EC2 instance. You can use this to automate installation of psql or other required command line tools.	string	"#!/bin/bash\n# NOTE: Since we're using a latest Amazon Linux AMI, we shouldn't need this,\n# but we'll update it to be sure.\ncd /tmp\nsudo yum install -y https://s3.amazonaws.com/ec2-downloads-windows/SSMAgent/latest/linux_amd64/amazon-ssm-agent.rpmnsudo systemctl enable amazon-ssm-agent\nsudo systemctl start amazon-ssm-agent\n"	no
vpc_id	The ID of the VPC which the EC2 Instance will run in.	string	n/a	yes

Outputs

Name	Description
autoscaling_group_id	The ID of the SSM Agent Autoscaling Group.
instance_name	The name tag value of the Bastion instance.
launch_template_id	The ID of the SSM Agent Launch Template.
role_id	The ID of the SSM Agent Role.
security_group_id	The ID of the SSM Agent Security Group.
session_logging_bucket_arn	The ARN of the SSM Agent Session Logging S3 Bucket.
session_logging_bucket_id	The ID of the SSM Agent Session Logging S3 Bucket.