How to add multiple keys for elastic beanstalk instance?

Question

There is a very good question on [How to] SSH to Elastic [an] Beanstalk instance, but one thing I noticed is that, through this method, it is only possible to add one SSH ke

Answer 1

Following on from Jim Flanagan's answer, you could get the keys added to every instance by creating .ebextensions/app.config in your application source directory with contents:

commands:
  copy_ssh_key_userA: 
    command: echo "ssh-rsa AAAB3N...QcGskx userA" >> /home/ec2-user/.ssh/authorized_keys
  copy_ssh_key_userB: 
    command: echo "ssh-rsa BBRdt5...LguTtp userB" >> /home/ec2-user/.ssh/authorized_keys

Answer 2

instead of running echo and storing your keys on Git, you can upload your public keys to IAM user's on AWS and than do:

commands:
  copy_ssh_key_userA: 
    command: rm -f /home/ec2-user/.ssh/authorized_keys;aws iam list-users --query "Users[].[UserName]" --output text | while read User; do aws iam list-ssh-public-keys --user-name "$User" --query "SSHPublicKeys[?Status == 'Active'].[SSHPublicKeyId]" --output text | while read KeyId; do aws iam get-ssh-public-key --user-name "$User" --ssh-public-key-id "$KeyId" --encoding SSH --query "SSHPublicKey.SSHPublicKeyBody" --output text >> /home/ec2-user/.ssh/authorized_keys; done; done;

Answer 3

The most dynamic way to add multiple SSH keys to Elastic Beanstalk EC2 instances

Step 1

Create a group in IAM. Call it something like beanstalk-access. Add the users who need SSH access to that group in IAM. Also add their public ssh key(s) to their IAM Security credentials.

Step 2

The deployment script below will be parsing JSON data from AWS CLI using a handy Linux tool called jq (jq official tutorial), so we need to add it in .ebextensions:

  packages:
    yum:
      jq: []

Step 3

Add the following BASH deployment script to .ebextensions:

  files:
    "/opt/elasticbeanstalk/hooks/appdeploy/post/980_beanstalk_ssh.sh":
      mode: "000755"
      owner: ec2-user
      group: ec2-user
      content: |
        #!/bin/bash
        rm -f /home/ec2-user/.ssh/authorized_keys
        users=$(aws iam get-group --group-name beanstalk-access | jq '.["Users"] | [.[].UserName]')
        readarray -t users_array < <(jq -r '.[]' <<<"$users")
        declare -p users_array
        for i in "${users_array[@]}"
        do
        user_keys=$(aws iam list-ssh-public-keys --user-name $i)
        keys=$(echo $user_keys | jq '.["SSHPublicKeys"] | [.[].SSHPublicKeyId]')
        readarray -t keys_array < <(jq -r '.[]' <<<"$keys")
        declare -p keys_array
        for j in "${keys_array[@]}"
        do
        ssh_public_key=$(aws iam get-ssh-public-key --encoding SSH --user-name $i --ssh-public-key-id $j | jq '.["SSHPublicKey"] .SSHPublicKeyBody' | tr -d \")
        echo $ssh_public_key >> /home/ec2-user/.ssh/authorized_keys
        done
        done
        chmod 600 /home/ec2-user/.ssh/authorized_keys
        chown ec2-user:ec2-user /home/ec2-user/.ssh/authorized_keys

Unfortunately, because this is YAML, you can't indent the code to make it more easily readable. But let's break down what's happening:

• (In the code snippet directly below) We're removing the default SSH key file to give full control of that list to this deployment script.

    rm -f /home/ec2-user/.ssh/authorized_keys
  

• (In the code snippet directly below) Using AWS CLI, we're getting the list of users in the beanstalk-access group, and then we're piping that JSON list into jq to extract only that list of `$users.

    users=$(aws iam get-group --group-name beanstalk-access | jq '.["Users"] | [.[].UserName]')
  

• (In the code snippet directly below) Here, we're converting that JSON $users list into a BASH array and calling it $users_array.

  readarray -t users_array < <(jq -r '.[]' <<<"$users") declare -p users_array

• (In the code snippet directly below) We begin looping through the array of users.

    for i in "${users_array[@]}"
    do
  

• (In the code snippet directly below) This can probably be done in one line, but it's grabbing the list of SSH keys associated to each user in the beanstalk-access group. It has not yet turned it into a BASH array, it's still a JSON list.

    user_keys=$(aws iam list-ssh-public-keys --user-name $i)
    keys=$(echo $user_keys | jq '.["SSHPublicKeys"] | [.[].SSHPublicKeyId]')
  

• (In the code snippet directly below) Now it's converting that JSON list of each users' SSH keys into a BASH array.

   readarray -t keys_array < <(jq -r '.[]' <<<"$keys")
   declare -p keys_array
  

• (In the code snippet directly below) Now it's converting that JSON list into a BASH array.

   readarray -t keys_array < <(jq -r '.[]' <<<"$keys")
   declare -p keys_array
  

• (In the code snippet directly below) Now we loop through each user's array of SSH keys.

   for j in "${keys_array[@]}"
   do
  

• (In the code snippet directly below) We're adding each SSH key for each user to the authorized_keys file.

  ssh_public_key=$(aws iam get-ssh-public-key --encoding SSH --user-name $i --ssh-public-key-id $j | jq '.["SSHPublicKey"] .SSHPublicKeyBody' | tr -d \")
  echo $ssh_public_key >> /home/ec2-user/.ssh/authorized_keys
  

• (In the code snippet directly below) Close out both the $users_array loop and $users_keys loop.

  done
  done
  

• (In the code snippet directly below) Give the authorized_keys file the same permissions it originally had.

  chmod 600 /home/ec2-user/.ssh/authorized_keys
  chown ec2-user:ec2-user /home/ec2-user/.ssh/authorized_keys
  

Step 4

If your Elastic Beanstalk EC2 instance is in a public subnet, you can just ssh into it using:

ssh ec2-user@ip-address -i /path/to/private/key

If your Elastic Beanstalk EC2 instance is in a private subnet (as it should be for cloud security best practices), then you will need to have a "bastion server" EC2 instance which will act as the gateway for tunneling all SSH access to EC2 instances. Look up ssh agent forwarding or ssh proxy commands to get an idea of how to accomplish SSH tunneling.

Adding new users

All you do is add them to your IAM beanstalk-access group and run a deployment, and that script will add them to your Elastic Beanstalk instances.

Answer 4

To create a file named .ebextensions/authorized_keys.config is another way to do it.

files:
  /home/ec2-user/.ssh/authorized_keys:
    mode: "000400"
    owner: ec2-user
    group: ec2-user
    content: |
      ssh-rsa AAAB3N...QcGskx keyname
      ssh-rsa BBRdt5...LguTtp another-key

The name of file authorized_keys.config is arbitrary.

Answer 5

One way you could accomplish this is to create a user data script which appends the public keys of the additional key-pairs you want to use to ~ec2-user/.ssh/authorized_keys, and launch the instance with that user data, for example:

#!
echo ssh-rsa AAAB3N...QcGskx keyname >> ~ec2-user/.ssh/authorized_keys
echo ssh-rsa BBRdt5...LguTtp another-key >> ~ec2-user/.ssh/authorized_keys

Answer 6

Combining rhunwicks's and rch850's answers, here's a clean way to add additional SSH keys, while preserving the one set through the AWS console:

files:
  /home/ec2-user/.ssh/extra_authorized_keys:
    mode: "000400"
    owner: ec2-user
    group: ec2-user
    content: |
      ssh-rsa AAAB3N...QcGskx keyname
      ssh-rsa BBRdt5...LguTtp another-key
commands:
  01_append_keys:
    cwd: /home/ec2-user/.ssh/
    command: sort -u extra_authorized_keys authorized_keys -o authorized_keys
  99_rm_extra_keys:
    cwd: /home/ec2-user/.ssh/
    command: rm extra_authorized_keys

Note that eb ssh will work only if the private key file has the same name as the private key defined in the AWS console.