How to find out the used Key pair name via AWS CLI?

Question

I'm aware of get-password-data command which can display PasswordData data like:

$ aws ec2 get-password-data --instance-id i-0123456789
{
    "InstanceId": "i-0123456789",
    "PasswordData": "\r\nAOh...xg==\r\n",
    "Timestamp": "2018-03-27T16:52:04.000Z"
}

however I'd like to know which Key pair name was used to launch the instance, so I can pass it using --priv-launch-key in order to decrypt the password.

Answer 1

For a given instance, you would first use aws ec2 describe-instances to get the information JSON for your instance.

The information also contains the keypair name used to create that instance.

E.g. for an instance i-0e2x8xd7xxx (Note: I use the awesome tool jq to do JSON parsing but you can use any other solution)

aws ec2 describe-instances --instance-ids i-0e2x8xd7xxx | jq '.Reservations[].Instances[].KeyName'

Output:

"my_key_name"

You can store that in a variable, say $keypair_name and then pass it into your aws ec2 get-password-data command.

You would also need to pass in the path on your machine where your keypairs are located e.g. $keypair_path.

For example:

aws ec2 get-password-data --priv-launch-key $keypair_path/$keypair_name .....

Answer 2

Based on @Vish answer, I've created the following shell script:

#/usr/bin/env bash
# Script to show password data of the EC2 instance.
[ $# -eq 0 ] && { echo "Usage: $0 instance_id ..."; exit; }
keyname=$(aws ec2 describe-instances --query 'Reservations[].Instances[].KeyName' --output text --instance-ids $1)
pemfile=$(find ~/.ssh -name "*$keyname*.pem" -print -quit)
if [ -z "$pemfile" ]; then
  aws ec2 get-password-data --instance-id $1
else
  aws ec2 get-password-data --instance-id $1 --priv-launch-key $pemfile
fi

which aims to decrypt the password based on the key pair name. By default it's looking for the PEM file in user's ~/.ssh folder.

Usage:

./show_ec2_password_data.sh i-instance_id