nblock's ~

Transparently edit Ansible Vault files with Vim

One way of storing secrets within Ansible is to use the built-in Vault and the respective command-line tool ansible-vault. A common use case is to have a key file available locally (a file containing the secret key information) and to use ansible-vault to encrypt/decrypt files as needed. The documentation on Ansible Vault should get you started.

Let's assume that there is an encrypted file in group_vars/mygroup/vault.yml. In order change the content of the file, one has to run:

$ ansible-vault edit group_vars/mygroup/vault.yml
$ # Your EDITOR of choice is spawned

The file gets decrypted and a fresh instance of your EDITOR of choice is loaded. On exit, the content of the buffer gets encrypted and saved back to the file.

There are some issues with this model:

  • A fresh instance of Vim is spawn with every change
  • Transparent editing is not possible
  • No use of nice editing features such as diffing with Fugitive
  • The interruption of the current workflow. For example, I need to background Vim or spawn a new shell, edit the encrypted file and get back to my previous Vim session.

One solution is to put the following snippet of Vim autocommands into your ~/.vimrc to handle Ansible Vault files transparently:

augroup ansible-vault
  autocmd BufReadPre,FileReadPre vault.yml setlocal viminfo=
  autocmd BufReadPre,FileReadPre vault.yml setlocal noswapfile noundofile nobackup
  autocmd BufReadPost,FileReadPost vault.yml silent %!ansible-vault decrypt
  autocmd BufWritePre,FileWritePre vault.yml silent %!ansible-vault encrypt
  autocmd BufWritePost,FileWritePost vault.yml silent undo
augroup END

The snippet above creates a new autocommand group named ansible-vault and resets any existing autocommands within this group. Before loading, a few settings are adjusted to avoid the leakage of secret data. After the file is loaded, it gets decrypted on the fly and the buffer content is replaced with the clear text representation of the encrypted file. The content of the buffer is encrypted before it is written back to disk. After writing, the undo command is executed once to keep the clear text representation in the buffer in case further edits are needed.

Note: This autocommand group only kicks in for files named vault.yml (that's how I name those files). If you have a different naming schema, you need to adjust this pattern to suit your needs.

Hint: Take a look at this Stack Overflow answer, if you want use git diff for Vault files.

Happy Vimming!

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tagged ansible and vim