KMS Encrypt and Decrypt filters in Ansible

ansible_kms_encrypt_decrypt.md

KMS Encrypt and Decrypt Filters for Ansible

This Gist shows how you can encrypt/decrypt variables with KMS during your Ansible playbook execution. While google searching I couldn't find anything useful on the subject.

Let's say your project has a folder of playbooks called plays.

In that folder, create a folder called filter_plugins and insert kms_filters.py (included in this gist)

plays/
├── filter_plugins
│   └── kms_filters.py
├── play1.yml
├── play2.yml

Ansible automatically imports any plugins found and makes them available to your playbooks. The example below shows how you can use the filters.

# play.yml
---
- hosts: localhost
  connection: local
  vars:
    kms_key: arn:aws:kms:us-east-1:xxxxxxxxxxxx:key/c21ca336-c9ed-5765-ad5f-fc941a5192ca
  tasks:
    - name: kms encrypt
      debug:
        msg: "{{ 'hello' | kms_encrypt(kms_key) }}"
    - name: kms encrypt
      debug:
        msg: "{{ 'Some base64 encoded Ciphertext Blob' | kms_decrypt }}"

Assumptions

For this to work you must have either one of the following:

• The awscli is configured on your machine (so boto can automatically pick up your AWS credentials)
• OR you're running this on an EC2 instance that has the appropriate permissions to access KMS

kms_filters.py

import boto3
import base64

kms = boto3.client('kms')

def kms_decrypt(ciphertext):
    return kms.decrypt(CiphertextBlob=base64.b64decode(ciphertext)).get('Plaintext')

def kms_encrypt(plaintext, key):
    return base64.b64encode(kms.encrypt(KeyId=key,Plaintext=plaintext).get('CiphertextBlob'))

class FilterModule(object): 
    def filters(self):
        return { 'kms_encrypt': kms_encrypt, 'kms_decrypt': kms_decrypt } 

play.yml

---
- hosts: localhost
  connection: local
  vars:
    kms_key: arn:aws:kms:us-east-1:xxxxxxxxxxxx:key/c21ca336-c9ed-5765-ad5f-fc941a5192ca
  tasks:
    - name: kms encrypt
      debug:
        msg: "{{ 'hello' | kms_encrypt(kms_key) }}"
    - name: kms encrypt
      debug:
        msg: "{{ 'Some base64 encoded Ciphertext Blob' | kms_decrypt }}"