Ansible Vault for an open source project: adventures in simplified indirection

“How can we publish our server configuration scripts as open source code without exposing our secrets to the world?”

It seemed like a simple enough mission. There are untold numbers of open source projects publishing directly to github.com; most large projects have secrets of one form or another. Someone must have figured out a pattern for keeping the secrets *near* the code without actually publishing them (or a key leading to them) as plaintext *in* the code, yes?

However, a cursory examination of tutorials on Ansible Vault left me with an uneasy feeling. It appears that a typical pattern for this kind of setup is to partition your secrets as variables in an Ansible Role, encrypt the variables, and unlock them at runtime with reference to a password file (~/.vault_pass.txt) [or an interactive prompt at each Ansible run *shudder*]. The encrypted content is available as an AES256 blob, and the password file… well, here’s where I get the heebie-jeebies:

  1. While AES256 is a solid algorithm, it still feels…weird to publish such files to the WORLD. Distributed password cracking is quite a thing; how ridiculous of a password would we need to have to withstand an army of bots grinding away at a static password, used to unlock the encrypted secrets? Certainly not a password that anyone would feel comfortable typing by hand every time it’s prompted.
  2. Password files need to be managed, stored, backed up and distributed/distributable among project participants. Have you ever seen the docs for PGP re: handling the master passphrase? Last time I remember looking with a friend, he showed me four places where the docs said “DON’T FORGET THE PASSPHRASE”. [Worst case, what happens if the project lead gets hit by a bus?]

I guess I was expecting some kind of secured, daemon-based query-and-response RPC server, the way Jan-Piet Mens envisioned here.

Challenges

  • We have a distributed, all-volunteer team – hit-by-a-bus scenarios must be part of the plan
  • (AFAIK) We have no permanent “off-the-grid” servers – no place to stash a secret that isn’t itself backed up on the Internet – so there will have to be at least periodic bootstrapping, and multiple locations where the vault password will live

Concerns re: Lifecycle of Ansible Vault secrets:

  1. Who should be in possession of the master secret? Can this be abstracted or does anyone using it have to know its value?
  2. What about editing encrypted files? Do you have to decrypt them each time and re-encrypt, or does “ansible-vault edit” hand-wave all that for you?
    • Answer: no, “ansible-vault edit” doesn’t persist the decrypted contents to disk, just sends them to your editor and transparently re-encrypts on save.
  3. Does Ansible Vault use per-file AES keys or a single AES key for all operations with the same password (that is, is the vault password a seed for the key or does it encrypt the key)?
    • Answer: not confirmed, but perusing the source code and the docs never mention per-file encryption, and the encrypted contents do not appear to store an encrypted AES key, so it looks like one AES key per vault password.
  4. Where to store the vault password if you want to integrate it into a CD pipeline?
    • Answer: –vault-password-file ~/.vault_pass.txt OR EVEN –vault-password-file ~/.vault_pass.py, where the script sends the password to stdout]
  5. Does anyone have a viable scheme that doesn’t require a privileged operator to be present during every deployment (–ask-vault-pass)?
    • i.e. doesn’t that mean you’re in danger of including ~/.vault_pass.txt in your git commit at some point? If not, where does that secret live?
  6. If you incorporate LastPass into your workflow to keep a protected copy of the vault password, can *that* be incorporated into the CD pipeline somehow?
  7. Are there any prominent OSS projects that have published their infrastructure and used Ansible Vault to publish encrypted versions of their secrets?

Based on my reading of the docs and blogs, it seems like this is the proferred solution for maximum automation and maintainability:

  • Divvy up all your secrets as variables and use pseudo-leaf indirection (var files referencing prefixed variables in a separate file) as documented here.
  • Encrypt the leaf-node file(s) using a super-complex vault password
  • Store the vault password in ~/.vault_pass.txt
  • Call all ansible and ansible-playbook commands using the –vault-password-file option
  • Smart: wire up a pre-commit step in git to make sure the right files are always encrypted as documented here.
  • Backup the vault password in a password manager like LastPass (so that only necessary participants get access to that section)
  • Manually deploy the ,vault_pass.txt file to your Jenkins server or other CI/CD master and give no one else access to that server/root/file.
  • Limit the number of individuals who need to edit the encrypted file(s), and make sure they list.vault_pass.txt in their .gitignore file.

P.S. Next up – look into the use of Hashicorp’s Vault project.

Reading List

Ansible Vault Docs:
http://docs.ansible.com/ansible/playbooks_vault.html

This is an incredibly useful article of good practices for using Ansible (and Ansible Vault) in a reasonably productive way:
https://www.reinteractive.net/posts/167-ansible-real-life-good-practices

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