aws ec2.py companion script to generate sshconfigs with auto bastion host discovery

Last update: Sep 11, 2022

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Overview

ec2-bastion-sshconfig

This script will interate over instances found by ec2.py and if those instances are not publically accessible it will search the associated VPC for any public instance that can be used as a bastion. Additionally it will create host aliases for any DNS records found in route53 that match the instance's IP(s) and CNAME records. The resulting output can be added to your ~/.ssh/config.

Requirements

This scipt depends on the ec2.py script and ec2.ini configuration file to work. You also need a working AWS_PROFILE as expected by the boto module.

Assumptions

ec2.py and ec2.ini are installed.
group_by_vpc_id = True in ec2.ini
SSH keys are named on your filesystem to the value of ec2_key_name. (You can use symlinks)

Setup environment

Create a python environment for testing

# python3 -m venv ec2-bastion-sshconfig

Enter the environment

# source ec2-bastion-sshconfig/bin/activate

Install required python modules

# pip install -r requirements.txt

Set ENV vars

# export AWS_PROFILE=default
# export EC2_INI_PATH=/usr/local/etc/ec2.ini

Run

# ./ec2-bastion-sshconfig.py -h
usage: ec2-bastion-sshconfig.py [-h] [--profile PROFILE] [--ec2Py EC2PY]
                                [--ec2PyINI EC2PYINI] [--sshUser SSHUSER]
                                [--sshKeyPATH SSHKEYPATH] [--sshPort SSHPORT]
                                [--debug DEBUG] [--awsDNSProfile AWSDNSPROFILE]
                                [--tld TLD]

optional arguments:
  -h, --help            show this help message and exit
  --profile PROFILE     Specify AWS credential profile to use.
  --ec2Py EC2PY         inventory script to use.
  --ec2PyINI EC2PYINI   inventory config file to use
  --sshUser SSHUSER     SSH username
  --sshKeyPATH SSHKEYPATH
                        PATH to SSH keys
  --sshPort SSHPORT     Alternate SSH port
  --debug DEBUG         Set to True to enable debug msgs
  --awsDNSProfile AWSDNSPROFILE
                        The AWS profile used to interact with route53
  --tld TLD             tld to append to hostnames

Option	Description	Default
`--profile`	`AWS_PROFILE` used to run ec2.py	`$AWS_PROFILE`
`--ec2Py`	Full path to the `ec2.py` script	`$PATH`
`--ec2PyINI`	Full path to the `ec2.ini` configuration file	`$EC2_INI_PATH`
`--sshUser`	Username to populate the `User` parameter in `~/.ssh/config`. If set the `IdentityFile` parameter will be set to the value of `ec2_key_name` found by `ec2.py`. (requires `--sshKeyPATH`)	`$USER`
`--sshKeyPATH`	Full path to local folder containing ssh key files.	`None`
`--sshPort`	Alternate port to try in addition to the default SSH port	"22"
`--debug`	Show debug messages	`False`
`awsDNSProfile`	`AWS_PROFILE` used to read from `route53`	"default"
`--tld`	DNS zone for which your instances belong	"example.com"

Example

# python ./ec2-bastion-sshconfig.py \
  --profile test \
  --ec2Py /usr/local/bin/ec2.py \
  --ec2PyINI /usr/local/etc/ec2.ini \
  --sshUser ec2_user \
  --sshKeyPATH ~/.ssh/ec2_keys \
  --sshPort 2222 \
  --awsDNSProfile default \
  --tld example.com | tee -a ~/.ssh/conf.d/example.com

##################################################
####   vpc-99999999999999999   ###################
##################################################

# <--
Host bastion bastion.example.com i-99999999999999999
  ForwardAgent yes
  StrictHostKeyChecking no
  Hostname 1.2.3.257
  Port 2222
  User ec2_user
  IdentityFile /data/home/username/.ssh/ec2_keys/test.pem
# -->

# <--
Host web-1 web-1.example.com i-99999999999999991
  ForwardAgent yes
  StrictHostKeyChecking no
  Hostname 10.0.0.4
  User ec2_user
  IdentityFile /data/home/username/.ssh/ec2_keys/test.pem
  ProxyJump bastion
# -->

# <--
Host web-2 web-2.example.com i-99999999999999992
  ForwardAgent yes
  StrictHostKeyChecking no
  Hostname 10.0.0.5
  User ec2_user
  IdentityFile /data/home/username/.ssh/ec2_keys/test.pem
  ProxyJump bastion
# -->

aws ec2.py companion script to generate sshconfigs with auto bastion host discovery

Related tags

Overview

ec2-bastion-sshconfig

Requirements

Assumptions

Setup environment

Create a python environment for testing

Enter the environment

Install required python modules

Set ENV vars

Run

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