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https://github.com/cloudposse/bastion

đź”’Secure Bastion implemented as Docker Container running Alpine Linux with Google Authenticator & DUO MFA support
https://github.com/cloudposse/bastion

alpine bastion docker dockerfile duo google-authenticator linux mfa openssh slack

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đź”’Secure Bastion implemented as Docker Container running Alpine Linux with Google Authenticator & DUO MFA support

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README 

        



# bastion [![Latest Release](https://img.shields.io/github/release/cloudposse/bastion.svg)](https://github.com/cloudposse/bastion/releases/latest) [![Build & Test Status](https://github.com/cloudposse/bastion/actions/workflows/integration-tests.yml/badge.svg)](https://github.com/cloudposse/bastion/actions/workflows/integration-tests.yml) [![Slack Community](https://slack.cloudposse.com/badge.svg)](https://slack.cloudposse.com)



[![README Header][readme_header_img]][readme_header_link]



[![Cloud Posse][logo]](https://cpco.io/homepage)



This is a secure/locked-down bastion implemented as a Docker Container. It uses Alpine Linux as the base image and ships with support for Google Authenticator & DUO MFA support.



It was designed to be used on Kubernetes together with [GitHub Authorized Keys](https://github.com/cloudposse/github-authorized-keys) to provide secure remote access to production clusters.

### MFA Setup & Usage



Here's a demo of what a user experiences when setting up Google Authenticator for the first time.



![Demo 1](docs/demo.gif)



When using Duo as the MFA provider, this becomes even more magical because Duo supports automatic Push notifications to your mobile device.

Just approve the request on your mobile phone (e.g. with a thumb press on iOS) when prompted.



### Slack Notifications



Here's what it looks like when someone connects to the bastion if Slack notifications are enabled.



![Demo 2](docs/slack.png)



We recommend using Slack notifications for self-reporting.

* Any time a user accesses production systems, they should reply to the slack notification to justify their remote access.

* A "buddy" should approve the login by adding a reaction (e.g. âś…).

* If no one approves the login, it should trigger an *incident response* to track down the unauthorized access.



---



This project is part of our comprehensive ["SweetOps"](https://cpco.io/sweetops) approach towards DevOps.

[][share_email]

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It's 100% Open Source and licensed under the [APACHE2](LICENSE).



## Usage



### Running



Refer to the [Environment Variables](#environment-variables) section below to tune how the `bastion` operates.



```bash

$ docker run -p 1234:22 cloudposse/bastion:latest

```



### Building



```bash

$ git clone https://github.com/cloudposse/bastion.git

$ cd bastion

$ make docker:build

```



### Testing



Run basic connection tests



```bash

$ make test

```



### Configuration



## Recommendations



* Do not allow `root` (or `sudo`) access to this container as doing so would allow remote users to manipulate audit-logs in `/var/log/sudo-io`

* Use the bastion as a "jump host" for accessing other internal systems rather than installing a lot of unnecessary stuff, which increases the overall attack surface.

* Sync the contents of `/var/log/sudo-io` to a remote, offsite location. If using S3, we recommend enabling bucket-versioning.

* Use [`github-authorized-keys](https://github.com/cloudposse/github-authorized-keys/) to automatically provision users; or use the [Helm chart](https://github.com/cloudposse/charts/tree/master/incubator/bastion).

* Bind-mount `/etc/passwd`, `/etc/shadow` and `/etc/group` into the container as *read-only*

* Bind-mount `/home` into container; the bastion does not manage authorized keys



#### Environment Variables



The following tables lists the most relevant environment variables of the `bastion` image and their default values.



##### Duo Settings



Duo is a enterprise MFA provider that is very affordable. Details here: https://duo.com/pricing



| ENV               |      Description                                    |  Default |

|-------------------|:----------------------------------------------------|:--------:|

| `MFA_PROVIDER`    |  Enable the Duo MFA provider                        | duo      |

| `DUO_IKEY`        |  Duo Integration Key                                |          |

| `DUO_SKEY`        |  Duo Secret Key                                     |          |

| `DUO_HOST`        |  Duo Host Endpoint                                  |          |

| `DUO_FAILMODE`    |  How to fail if Duo cannot be reached               | secure   |

| `DUO_AUTOPUSH`    |  Automatically send a push notification             | yes      |

| `DUO_PROMPTS`     |  How many times to prompt for MFA                   | 1        |



##### Google Authenticator Settings



Google Authenticator is a free & open source MFA solution. It's less secure than Duo because tokens are stored on the server under each user account.



| ENV               |      Description                                    |  Default              |

|-------------------|:----------------------------------------------------|:---------------------:|

| `MFA_PROVIDER`    |  Enable the Google Authenticator provider           | google-authenticator  |



##### Enforcer Settings



The enforcer ensures certain conditions are satisfied. Currently, these options are supported.



| ENV                           |  Description                                                 |  Default |

|-------------------------------|:-------------------------------------------------------------|:--------:|

| `ENFORCER_ENABLED`            |  Enable general enforcement                                  | `true`   |

| `ENFORCER_CLEAN_HOME_ENABLED` |  Erase dot files in home directory before starting session   | `true`   |



##### Slack Notifications



The enforcer is able to send notifications to a slack channel anytime there is an SSH login.



| ENV                        |      Description                                    |  Default  |

|----------------------------|:----------------------------------------------------|:---------:|

| `SLACK_ENABLED`            | Enabled Slack integration                           | `false`   |

| `SLACK_HOOK`               | Slack integration method (e.g. `pam`, `sshrc`)      | `sshrc`   |

| `SLACK_WEBHOOK_URL`        | Webhook URL                                         |           |

| `SLACK_USERNAME`           | Slack handle of bot (defaults to short-dns name)    |           |

| `SLACK_TIMEOUT`            | Request timeout                                     | `2`       |

| `SLACK_FATAL_ERRORS`       | Deny logins if slack notification fails             | `true`    |



##### SSH Auditor



The SSH auditor uses [`sudosh`](https://github.com/cloudposse/sudosh/) to record entire SSH sessions (`stdin`, `stdout`, and `stderr`).



| ENV                   |      Description                                    |  Default     |

|-----------------------|:----------------------------------------------------|:------------:|

| `SSH_AUDIT_ENABLED`   |  Enable the SSH Audit facility                      | `true`       |



This will require that users login with the `/usr/bin/sudosh` shell.



Update user's default shell by running the command: `usermod -s /usr/bin/sudosh $username`. By default, `root` will automatically be updated to use `sudosh`.



Use the `sudoreplay` command to audit/replay sessions.



#### User Accounts & SSH Keys



The `bastion` does not attempt to manage user accounts. We suggest using [GitHub Authorized Keys](https://github.com/cloudposse/github-authorized-keys) to provision user accounts and SSH keys. We provide a [chart](https://github.com/cloudposse/charts/tree/master/incubator/bastion) of how we recommend doing it.



### Extending



The `bastion` was written to be easily extensible.



You can extend the enforcement policies by adding shell scripts to `etc/enforce.d`. Any scripts that are `+x` (e.g. `chmod 755`) will be executed at runtime.



## Thanks



- [@neochrome](https://github.com/neochrome/docker-bastion), for providing a great basic bastion built on top of Alpine Linux

- [@aws](https://aws.amazon.com/blogs/security/how-to-record-ssh-sessions-established-through-a-bastion-host/), for providing detailed instructions on how to do SSH session logging.

- [@duo](https://duo.com/docs/duounix), for providing excellent documentation

- [@google](https://github.com/google/google-authenticator-libpam) for contributing Google Authenticator to the Open Source community



## Quick Start



Here's how you can quickly demo the `bastion`. We assume you have `~/.ssh/authorized_keys` properly configured and your SSH key (e.g. `~/.ssh/id_rsa`) added to your SSH agent.



```bash

$ docker run -it -p 1234:22 \

     -e MFA_PROVIDER=google-authenticator \

     -v ~/.ssh/authorized_keys:/root/.ssh/authorized_keys \

     cloudposse/bastion

```



Now, in another terminal you should be able to run:

```bash

$ ssh root@localhost -p 1234

```



The first time you connect, you'll be asked to setup your MFA device. Subsequently, each time you connect, you'll be prompted to enter your MFA token.



## Help



**Got a question?** We got answers.



File a GitHub [issue](https://github.com/cloudposse/bastion/issues), send us an [email][email] or join our [Slack Community][slack].



[![README Commercial Support][readme_commercial_support_img]][readme_commercial_support_link]



## DevOps Accelerator for Startups



We are a [**DevOps Accelerator**][commercial_support]. We'll help you build your cloud infrastructure from the ground up so you can own it. Then we'll show you how to operate it and stick around for as long as you need us.



[![Learn More](https://img.shields.io/badge/learn%20more-success.svg?style=for-the-badge)][commercial_support]



Work directly with our team of DevOps experts via email, slack, and video conferencing.



We deliver 10x the value for a fraction of the cost of a full-time engineer. Our track record is not even funny. If you want things done right and you need it done FAST, then we're your best bet.



- **Reference Architecture.** You'll get everything you need from the ground up built using 100% infrastructure as code.

- **Release Engineering.** You'll have end-to-end CI/CD with unlimited staging environments.

- **Site Reliability Engineering.** You'll have total visibility into your apps and microservices.

- **Security Baseline.** You'll have built-in governance with accountability and audit logs for all changes.

- **GitOps.** You'll be able to operate your infrastructure via Pull Requests.

- **Training.** You'll receive hands-on training so your team can operate what we build.

- **Questions.** You'll have a direct line of communication between our teams via a Shared Slack channel.

- **Troubleshooting.** You'll get help to triage when things aren't working.

- **Code Reviews.** You'll receive constructive feedback on Pull Requests.

- **Bug Fixes.** We'll rapidly work with you to fix any bugs in our projects.



## Slack Community



Join our [Open Source Community][slack] on Slack. It's **FREE** for everyone! Our "SweetOps" community is where you get to talk with others who share a similar vision for how to rollout and manage infrastructure. This is the best place to talk shop, ask questions, solicit feedback, and work together as a community to build totally *sweet* infrastructure.



## Discourse Forums



Participate in our [Discourse Forums][discourse]. Here you'll find answers to commonly asked questions. Most questions will be related to the enormous number of projects we support on our GitHub. Come here to collaborate on answers, find solutions, and get ideas about the products and services we value. It only takes a minute to get started! Just sign in with SSO using your GitHub account.



## Newsletter



Sign up for [our newsletter][newsletter] that covers everything on our technology radar.  Receive updates on what we're up to on GitHub as well as awesome new projects we discover.



## Office Hours



[Join us every Wednesday via Zoom][office_hours] for our weekly "Lunch & Learn" sessions. It's **FREE** for everyone!



[![zoom](https://img.cloudposse.com/fit-in/200x200/https://cloudposse.com/wp-content/uploads/2019/08/Powered-by-Zoom.png")][office_hours]



## Contributing



### Bug Reports & Feature Requests



Please use the [issue tracker](https://github.com/cloudposse/bastion/issues) to report any bugs or file feature requests.



### Developing



If you are interested in being a contributor and want to get involved in developing this project or [help out](https://cpco.io/help-out) with our other projects, we would love to hear from you! Shoot us an [email][email].



In general, PRs are welcome. We follow the typical "fork-and-pull" Git workflow.



 1. **Fork** the repo on GitHub

 2. **Clone** the project to your own machine

 3. **Commit** changes to your own branch

 4. **Push** your work back up to your fork

 5. Submit a **Pull Request** so that we can review your changes



**NOTE:** Be sure to merge the latest changes from "upstream" before making a pull request!



## Copyright



Copyright © 2017-2023 [Cloud Posse, LLC](https://cpco.io/copyright)



## License



[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)



See [LICENSE](LICENSE) for full details.



```text

Licensed to the Apache Software Foundation (ASF) under one

or more contributor license agreements.  See the NOTICE file

distributed with this work for additional information

regarding copyright ownership.  The ASF licenses this file

to you under the Apache License, Version 2.0 (the

"License"); you may not use this file except in compliance

with the License.  You may obtain a copy of the License at



  https://www.apache.org/licenses/LICENSE-2.0



Unless required by applicable law or agreed to in writing,

software distributed under the License is distributed on an

"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

KIND, either express or implied.  See the License for the

specific language governing permissions and limitations

under the License.

```



## Trademarks



All other trademarks referenced herein are the property of their respective owners.



## About



This project is maintained and funded by [Cloud Posse, LLC][website]. Like it? Please let us know by [leaving a testimonial][testimonial]!



[![Cloud Posse][logo]][website]



We're a [DevOps Professional Services][hire] company based in Los Angeles, CA. We ❤️  [Open Source Software][we_love_open_source].



We offer [paid support][commercial_support] on all of our projects.



Check out [our other projects][github], [follow us on twitter][twitter], [apply for a job][jobs], or [hire us][hire] to help with your cloud strategy and implementation.



### Contributors



|  [![Erik Osterman][osterman_avatar]][osterman_homepage]
[Erik Osterman][osterman_homepage] | [![Marji Cermak][marji_avatar]][marji_homepage]
[Marji Cermak][marji_homepage] |

|---|---|



  [osterman_homepage]: https://github.com/osterman

  [osterman_avatar]: https://img.cloudposse.com/150x150/https://github.com/osterman.png

  [marji_homepage]: https://github.com/marji

  [marji_avatar]: https://img.cloudposse.com/150x150/https://github.com/marji.png



[![README Footer][readme_footer_img]][readme_footer_link]

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