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Bastion servers (Jump hosts)

Overview

  • Bastion server is a simple virtual machine used for accessing resources that are only accessible from within your VPC (private network, not accessible from the internet). Some resources, such as relational databases, redis clusters, might not have public endpoint, but you still need to access them from your scripts or to perform management tasks.
  • The connection from your system to the bastion server is securely established using SSM session manager, leveraging your IAM permissions. This means that your bastion does NOT expose any ports resulting in high security.

Usage

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resources:
myBastion:
type: bastion

Example config with bastion

Connecting to bastion (interactive session)

You can connect to bastion server and start a shell session using command bastion:session.

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stacktape bastion:session --stage <<stage>> --region <<region>> --bastionResource <<bastionResourceName>>

The connection from your system to the bastion server is securely established using SSM session manager, leveraging your IAM permissions. This means that your bastion does NOT expose any ports resulting in high security.

Creating bastion tunnel

Some resources, such as relational databases, redis clusters, might not have public endpoint, but you still might want to access them from your local workstation.

With bastion:tunnel command, you can start a tunneling session to access resources protected in the VPC through your bastion.

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stacktape bastion:tunnel --stage <<stage>> --region <<region>> --bastionResource <<bastionResourceName>> --resourceName <<nameOfTargetResource>>

Tunneling, is a technique that allows network traffic to be redirected from one network port to another. It establishes a secure pathway between a source and destination port, facilitating the transmission of data across networks.


When using Stacktape, pathway is created between target resource port (for example a port of your database) and local port on the local host (where Stacktape is running). Bastion resource is used as an intermediary between your local host and the target resource.


After tunnel is created, Stacktape prints the tunneled endpoint (which you can use for connecting to the resource) into terminal.

Tunnel example

Graphical overview of tunneling
Graphical overview of tunneling

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resources:
myBastion:
type: bastion
myDatabase:
type: relational-database
properties:
# database is only accessible from withing VPC
accessibility:
accessibilityMode: vpc
engine:
type: postgres
properties:
primaryInstance:
instanceSize: db.t3.micro
credentials:
masterUserName: my_user_name
masterUserPassword: my_secret_pass

Bastion with database accessible only in VPC

Considering the config above, following command creates tunnel to the database:

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stacktape bastion:tunnel --stage <<stage>> --bastionResource myBastion --resourceName myDatabase

After tunnel is created, Stacktape prints the tunneled endpoint (which you can use for connecting to the resource) into terminal.

Terminal output after starting tunnel
Terminal output after starting tunnel

Bastion tunneling is supported for following resource types:

  • relational-database
  • redis-cluster
  • application-load-balancer
  • private-service (with loadBalancing type application-load-balancer)

Using bastion with scripts

You can use bastion with the scripts specified in scripts section of your config.

For more information refer to following doc pages:

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scripts:
migrateDb:
type: local-script-with-bastion-tunneling
properties:
executeScript: migrate.ts
connectTo:
- myDatabase
hooks:
afterDeploy:
- scriptName: migrateDb
resources:
myBastion:
type: bastion
myDatabase:
type: relational-database
properties:
# database is only accessible from withing VPC
accessibility:
accessibilityMode: vpc
engine:
type: postgres
properties:
primaryInstance:
instanceSize: db.t3.micro
credentials:
masterUserName: my_user_name
masterUserPassword: my_secret_pass

Stacktape config using the migration script with tunneling

Instance size

  • Optionally, you can specify instance size of your bastion host. By default, t3.micro instance is used (free tier eligible).

  • If you wish to use bigger instance for your bastion, you can specify instanceSize property.

  • To see full list of available instance sizes, refer to AWS docs.

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resources:
myBastion:
type: bastion
properties:
instanceSize: c5.large

Custom commands on bastion launch

You can use runCommandsAtLaunch property to run custom set of commands when the bastion is launched.


Running custom commands can be useful for installing dependencies or setting up your bastion in any other way:

  • Commands are run as the root user (do not use sudo).
  • Modifying this list after bastion was already created will force replacement of the bastion instance. This means that any data that was manually created on the old bastion instance will be lost.

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resources:
myBastion:
type: bastion
properties:
runCommandsAtLaunch:
- yum update
- yum install postgresql.x86_64 -y

All bastion hosts are using latest Amazon Linux 2 operating system.

SSM sessions

With Stacktape, bastion hosts leverage SSM session manager.


SSM Session Manager is a service provided by AWS that enables secure and centralized management of instances without the need for direct access. Compared to traditional SSH, SSM Session Manager establishes a secure channel using AWS Systems Manager which eliminates the need for managing SSH keys, opening additional network ports, and dealing with potential security risks associated with SSH access - making it more secure.

Pricing

Price of the bastion depends on the instance size used for your bastion.

By default (if you do not specify instance size), t3.micro instance is used. This instance is free tier eligible. If you are not in a free tier, monthly cost of this instance is ~$7.5.

API reference

Bastion  API reference
type
Required
properties.instanceSize
Default: t3.micro
properties.runCommandsAtLaunch
properties.logging
overrides
BastionLogging  API reference
disabled
retentionDays
logForwarding

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