aws-ssh-config

Description

A very simple script that queries the AWS EC2 API with boto and generates a SSH config file ready to use. There are a few similar scripts around but I couldn't find one that would satisfy all my wish list:

Connect to all regions at once
Do AMI -> user lookup (regexp-based)
Support public/private IP addresses (for VPNs and VPCs)
Support multiple instances with same tags (e.g. autoscaling groups) and provide an incremental count for duplicates based on instance launch time
Support multiple customizable tags concatenations in a user-provided order
Support region (with AZ) in the host name concatenation
Properly leverage tab completion

Usage

This assumes boto is installed and configured. Also, private ssh keys must be copied under ~/.ssh/

Supported arguments:

usage: aws-ssh-config.py [-h] [--default-user DEFAULT_USER] [--keydir KEYDIR]
                         [--no-identities-only] [--prefix PREFIX] [--private]
                         [--profile PROFILE] [--region]
                         [--strict-hostkey-checking] [--tags TAGS]
                         [--user USER]
                         [--white-list-region WHITE_LIST_REGION [WHITE_LIST_REGION ...]]

optional arguments:
  -h, --help            show this help message and exit
  --default-user DEFAULT_USER
                        Default ssh username to use if it can't be detected
                        from AMI name
  --keydir KEYDIR       Location of private keys
  --no-identities-only  Do not include IdentitiesOnly=yes in ssh config; may
                        cause connection refused if using ssh-agent
  --prefix PREFIX       Specify a prefix to prepend to all host names
  --private             Use private IP addresses (public are used by default)
  --profile PROFILE     Specify AWS credential profile to use
  --region              Append the region name at the end of the concatenation
  --ssh-key-name        Override the ssh key to use
  --strict-hostkey-checking
                        Do not include StrictHostKeyChecking=no in ssh config
  --tags TAGS           A comma-separated list of tag names to be considered
                        for concatenation. If omitted, all tags will be used
  --user USER           Override the ssh username for all hosts
  --white-list-region WHITE_LIST_REGION [WHITE_LIST_REGION ...]
                        Which regions must be included. If omitted, all
                        regions are considered

By default, it will name hosts by concatenating all tags:

gianluca@sid:~$ python aws-ssh-config.py > ~/.ssh/config
gianluca@sid:~$ cat ~/.ssh/config
Host dev-worker-1
    HostName 54.173.109.173
    User ec2-user
    IdentityFile ~/.ssh/dev.pem
    IdentitiesOnly yes
    StrictHostKeyChecking no

Host dev-worker-2
    HostName 54.173.190.141
    User ec2-user
    IdentityFile ~/.ssh/dev.pem
    IdentitiesOnly yes
    StrictHostKeyChecking no

Host prod-worker-1
    HostName 54.164.168.30
    User ec2-user
    IdentityFile ~/.ssh/prod.pem
    IdentitiesOnly yes
    StrictHostKeyChecking no

Host prod-worker-2
    HostName 54.174.115.242
    User ubuntu
    IdentityFile ~/.ssh/prod.pem
    IdentitiesOnly yes
    StrictHostKeyChecking no

ssh completion will immediately work:

gianluca@sid:~$ ssh d[TAB]
dev-worker-1
dev-worker-2

If the ssh completion will not immediately work you should add the following script to your .bash_profile

_complete_ssh_hosts ()
{
        COMPREPLY=()
        cur="${COMP_WORDS[COMP_CWORD]}"
        comp_ssh_hosts=`cat ~/.ssh/known_hosts | \
                        cut -f 1 -d ' ' | \
                        sed -e s/,.*//g | \
                        grep -v ^# | \
                        uniq | \
                        grep -v "\[" ;
                cat ~/.ssh/config | \
                        grep "^Host " | \
                        awk '{print $2}'
                `
        COMPREPLY=( $(compgen -W "${comp_ssh_hosts}" -- $cur))
        return 0
}
complete -F _complete_ssh_hosts ssh

and run gianluca@sid:~$ source .bash_profile

It's possible to customize which tags one is interested in, as well as the order used for concatenation:

gianluca@sid:~$ python aws-ssh-config.py --tags Name > ~/.ssh/config
gianluca@sid:~$ cat ~/.ssh/config
Host worker-1
    HostName 54.173.109.173
    User ec2-user
    IdentityFile ~/.ssh/dev.pem
    IdentitiesOnly yes
    StrictHostKeyChecking no

Host worker-2
    HostName 54.173.190.141
    User ec2-user
    IdentityFile ~/.ssh/dev.pem
    IdentitiesOnly yes
    StrictHostKeyChecking no

Host worker-3
    HostName 54.164.168.30
    User ec2-user
    IdentityFile ~/.ssh/prod.pem
    IdentitiesOnly yes
    StrictHostKeyChecking no

Host worker-4
    HostName 54.174.115.242
    User ubuntu
    IdentityFile ~/.ssh/prod.pem
    IdentitiesOnly yes
    StrictHostKeyChecking no

gianluca@sid:~$ python aws-ssh-config.py --tags Name,Infrastructure > ~/.ssh/config
gianluca@sid:~$ cat ~/.ssh/config
Host worker-dev-1
    HostName 54.173.109.173
    User ec2-user
    IdentityFile ~/.ssh/dev.pem
    IdentitiesOnly yes
    StrictHostKeyChecking no

Host worker-dev-2
    HostName 54.173.190.141
    User ec2-user
    IdentityFile ~/.ssh/dev.pem
    IdentitiesOnly yes
    StrictHostKeyChecking no

Host worker-prod-1
    HostName 54.164.168.30
    User ec2-user
    IdentityFile ~/.ssh/prod.pem
    IdentitiesOnly yes
    StrictHostKeyChecking no

Host worker-prod-2
    HostName 54.174.115.242
    User ubuntu
    IdentityFile ~/.ssh/prod.pem
    IdentitiesOnly yes
    StrictHostKeyChecking no

By default, the ssh user is calculated from a regular expression based on the AMI name. A default user can be set with --default-user to use if no matches are found, otherwise a warning is printed on standard error and one can edit the script and add the rule to the AMIS_TO_USER dictionary:

gianluca@sid:~$ python aws-ssh-config.py > ~/.ssh/config
Can't lookup user for AMI 'ubuntu/images/hvm-ssd/ubuntu-trusty-14.04-amd64-server-20140926', add a rule to the script

The --user param can also be used to use a single username for all hosts.

mbreitung/aws-ssh-config

aws-ssh-config

Description

Usage