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ssm-tool

SSM toolkit. Designed to compliment ssh-over-ssm.

Info, requirements and installation

It's been a while since I uploaded and started using ssh-over-ssm and it's really simplified AWS EC2 access for myself and colleagues. Over time I've updated ssm-tool (which began as a script to simply list/update SSM instances) to further simplify setup and configuration of SSH access over SSM, requiring only AWS credentials.

Demo

ssm-tool installation and usage

Quick setup guide for the impatient.

Requirements

  • python3 with some pip modules (see requirements.txt)
  • awscli
  • session-manager-plugin
  • ssh-ssm.sh from ssh-over-ssm
  • a config snippet added to the end of your SSH config (~/.ssh/config)
  • ssh-ssm.sh and ssm-tool in your $PATH
  • ssm-agent installed and updated on remote instances
  • necessary AWS IAM permissions for your user and the remote host (instance profile)

Installation and usage

  1. Clone this repository and ssh-over-ssm
  2. Place scripts in a familiar local directory (e.g. ~/bin/)
  3. Make executable and add to PATH -> chmod +x ~/bin/{ssm-tool,ssh-ssm.sh} and echo "export PATH="$HOME/bin${PATH:+:${PATH}}""| tee -a ~/.bashrc (or ~/.bash_profile)
  4. Install required python modules -> pip3 install --user -r /path/to/ssm-tool-repo/requirements.txt
  5. Add snippet to SSH config (see below)
  6. macOS users may need to update bash and openssh with brew install

SSH config

To make use of the functionality provided by ssh-over-ssm and ssm-tool you will need to place the following snippet (example config provided in repo) at the end of your SSH config file (~/.ssh/config) and remove any other config which matches against i-*:

Match exec "grep -qs '^Host.*%n' %d/.ssh/ssmtool-*"
  Include ssmtool-*

Match host i-*
  ProxyCommand ssh-ssm.sh %h %r
  IdentityFile ~/.ssh/ssm-ssh-tmp
  StrictHostKeyChecking no
  PasswordAuthentication no
  ChallengeResponseAuthentication no

How it works

ssh-over-ssm

ssh-over-ssm is simply a small bash script wrapper which performs some checks on execution and then runs two AWS commands:

  • ssm send-command (with ssm document AWS-RunShellScript)
  • ssm start-session (with document AWS-StartSSHSession).

The difference between this and the ProxyCommand provided by AWS in their documentation is that ssh-over-ssm automates placing your local SSH key (and generating one if need) on the remote server prior to starting the SSH session and connecting. The public key is removed after 15 seconds. Without this your SSH public key must exist on the instance, under the correct user's directory before you attempt to connect.

ssm-tool

ssm-tool is a python script which acts as a toolkit for SSM. It was created and designed to work in conjunction with ssh-over-ssm. Its' main functionality is:

  • list/search SSM instances (filter by windows/linux, output as formatted table, plain text or only instance id)
  • update SSM agent on instances
  • access instances via SSM session or SSH
  • generate SSH config fragments to simplify SSH access over SSM (usernames are configured in line with the default OS user by default)

why both?

I'd prefer to keep ssh-over-ssm as a small bash wrapper script which can continue to be used without ssm-tool if preferred. If you wish to make use of ssm-tool to generate SSH config for you or access instances directly using SSH, ssh-over-ssm knows to check for ssm-tool configuration when it is executed.

NOTE: If your SSH public key does not exist on the remote server you must use ssh-over-ssm for seamless SSH access.

Example usage

The following is true for the below examples:

  • I am assuming role to accounts using AWS CLI profiles configured in ~/.aws/{config,credentials}.
  • I have configured a region for my default and other configured awscli profiles.
  • I am using the example SSH configuration file from this repo.
  • I do not have a SSH key on my machine locally (and obviously there's no public key on the remote server).

Listing instances and filtering results

Default list (no arguments/flags):

[elpy@testbox ~]$ ssm-tool --profile home-dev
+--------------------------+---------------------+---------------+------------+--------------+
| tag[name]                | instance            | ip address    | ssm-agent* | platform     |
+--------------------------+---------------------+---------------+------------+--------------+
| home-dev-jumpbox-01      | i-0xxxxxxxxxxxx79d6 | 10.xxx.24.9   | True       | Amazon Linux |
| home-dev-confluenceasg   | i-0xxxxxxxxxxxx9007 | 10.xxx.24.1xx | True       | CentOS Linux |
| home-dev-bambooasg       | i-0xxxxxxxxxxxx29b9 | 10.xxx.24.2xx | True       | CentOS Linux |
| home-dev-jiraasg         | i-0xxxxxxxxxxxxc331 | 10.xxx.24.2xx | True       | CentOS Linux |
+--------------------------+---------------------+---------------+------------+--------------+
 * ssm-agent column refers to whether the agent is up-to-date

Use a search term to display only amazon linux hosts (filters results based on platform):

[elpy@testbox ~]$ ssm-tool --profile home-dev amazon
+-----------------------+---------------------+-------------+------------+--------------+
| tag[name]             | instance            | ip address  | ssm-agent* | platform     |
+-----------------------+---------------------+-------------+------------+--------------+
| home-dev-jumpbox-01   | i-0xxxxxxxxxxxx79d6 | 10.xxx.24.9 | True       | Amazon Linux |
+-----------------------+---------------------+-------------+------------+--------------+

Use a search term to filter by part of the IP address:

[elpy@testbox ~]$ ssm-tool --profile home-dev 24.2
+----------------------+---------------------+---------------+------------+--------------+
| tag[name]            | instance            | ip address    | ssm-agent* | platform     |
+----------------------+---------------------+---------------+------------+--------------+
| home-dev-bambooasg   | i-0xxxxxxxxxxxx29b9 | 10.xxx.24.2xx | True       | CentOS Linux |
| home-dev-jiraasg     | i-0xxxxxxxxxxxxc331 | 10.xxx.24.2xx | True       | CentOS Linux |
+----------------------+---------------------+---------------+------------+--------------+

Search term to filter by name[tag]:

[elpy@testbox ~]$ ssm-tool --profile home-dev jira
+-------------------+---------------------+---------------+------------+--------------+
| tag[name]         | instance            | ip address    | ssm-agent* | platform     |
+-------------------+---------------------+---------------+------------+--------------+
| home-dev-jiraasg  | i-0xxxxxxxxxxxxc331 | 10.xxx.24.2xx | True       | CentOS Linux |
+-------------------+---------------------+---------------+------------+--------------+

Other list options:

  • For plain text output (no pretty formatted table) add the --text flag.
  • To filter results by linux/windows use -x --linux or -w --windows flags.
  • To return only instance IDs use the --iid flag.

Connecting to an instance using a SSM session

[elpy@testbox ~]$ ssm-tool --profile home-dev --session i-0xxxxxxxxxxxx29b9

Starting session with SessionId: example123-0e467c6bf9f9ae39d
sh-4.2$ sudo -i
[root@ip-10-xxx-24-2xx ~]# logout
sh-4.2$ exit

Exiting session with sessionId: example123-0e467c6bf9f9ae39d.

NOTE: You will connect as the ssm-user

Connecting to an instance over SSH using ssm-tool and instance id:

SSH from ssm-tool without any pre-configuration:

[elpy@testbox ~]$ ssm-tool --profile home-dev --ssh centos@i-0xxxxxxxxxxxx29b9
Last login: Fri May  8 10:54:38 2020 from localhost
[centos@ip-10-xxx-24-2xx ~]$ sudo -i
[root@ip-10-xxx-24-2xx ~]#
[root@ip-10-xxx-24-2xx ~]# logout
[centos@ip-10-xxx-24-2xx ~]$ logout
Connection to i-0xxxxxxxxxxxx29b9 closed.

NOTE: input to this argument is treated as if it were the arguments to ssh on the CLI

Using ssm-tool to generate SSH config and then using ssh directly to connect

Generate config:

[elpy@testbox ~]$ ssm-tool --profile home-dev --ssh-conf

ssh config fragment generated and saved to -> /home/elpy/.ssh/ssmtool-home-dev

Connect over SSH to the jumpbox host using name[tag]:

[elpy@testbox ~]$ ssh home-dev-jumpbox-01
Last login: Sun May 10 07:15:35 2020 from localhost

       __|  __|_  )
       _|  (     /   Amazon Linux 2 AMI
      ___|\___|___|

https://aws.amazon.com/amazon-linux-2/
74 package(s) needed for security, out of 154 available
Run "sudo yum update" to apply all updates.
[ec2-user@ip-10-xxx-24-9 ~]$ logout
Connection to i-0xxxxxxxxxxxx79d6 closed.

Connect over SSH to the confluence host using IP address:

[elpy@testbox ~]$ ssh 10.xxx.24.1xx
Last login: Sun May 10 07:18:48 2020 from localhost
[centos@ip-10-xxx-24-1xx ~]$ logout
Connection to i-0xxxxxxxxxxxx9007 closed.

Connect over SSH to the bamboo host using short hostname:

[elpy@testbox ~]$ ssh ip-10-xxx-24-2xx.ap-southeast-2
Last login: Sun May 10 12:44:19 2020 from localhost
[centos@ip-10-xxx-24-2xx ~]$ logout
Connection to i-0xxxxxxxxxxxx29b9 closed.

Note: Feel free to add other names or change the username in the generated SSH config fragment

If you don't use AWS profiles

For example, if you use some form of tooling to export required env vars for you. ssm-tool will still work, however you will need to ensure you export the required environment variables each time you run ssh. Example below.

Find jira instance and generate config (config fragment is no longer attached to profile):

[elpy@testbox ~]$ awsenv home-dev -- ssm-tool jira
+-------------------+---------------------+---------------+------------+--------------+
| tag[name]         | instance            | ip address    | ssm-agent* | platform     |
+-------------------+---------------------+---------------+------------+--------------+
| home-dev-jiraasg  | i-0xxxxxxxxxxxxc331 | 10.xxx.24.2xx | True       | Amazon Linux |
+-------------------+---------------------+---------------+------------+--------------+
  
  
[elpy@testbox ~]$ awsenv home-dev -- ssm-tool --ssh-conf

ssh config fragment generated and saved to -> /home/elpy/.ssh/ssmtool-env
  
  
[elpy@testbox ~]$ cat ~/.ssh/ssmtool-env 
# config created without AWS profile set (must have appropriate env vars set when connecting)
Host home-dev-jiraasg 10.xxx.24.2xx ip-10-xxx-24-2xx.ap-southeast-2
  Hostname i-0xxxxxxxxxxxxc331
  User ec2-user

Connect over SSH to the instance:

[elpy@testbox ~]$ awsenv home-dev -- ssh home-dev-jiraasg
Last login: Sun May 21 04:11:54 2020 from localhost

       __|  __|_  )
       _|  (     /   Amazon Linux 2 AMI
      ___|\___|___|

https://aws.amazon.com/amazon-linux-2/
6 package(s) needed for security, out of 20 available
Run "sudo yum update" to apply all updates.
[ec2-user@ip-10-xxx-24-2xx ~]$ logout
Connection to i-0xxxxxxxxxxxxc331 closed.