ervin's blog

From Zero to Encyrpted Secrets in 2 Minutes with SOPS and GPG

  • Dec 05, 2020

You probably heard about mozilla/sops, but even if the readme is amazingly detailed, a from-scratch example is always nice to have.

sops, in a nutshell, bridges the gap between various key management services (PGP, AWS KMS, GCP KMS, Azure Key Vault) and you. This post will attempt to get you on your feet as fast as possible, in 3 simple steps: from “I have no idea what to do with my hands” to “No way it’s that easy!”.

Install the dependencies:

$ brew install sops gnupg

And run these 3-ish commands to convince yourself:

# Clone the example repository
$ git clone https://github.com/ervinb/sops-gpg-example.git
$ cd sops-gpg-example

# Import the encryption key
$ gpg --import <(curl -L https://gist.githubusercontent.com/ervinb/288c44a45cf2614a0684bea333b3aa36/raw/sops-gpg-example.asc)

# Decrypt and open the file
$ sops secrets/mysecrets.dev.enc.yaml

Your day-to-day interaction with this would be only the last line.

gpg --import has to be executed only once, after which the key will be part of the local keychain (persists reboots as well). That’s literally all there is to it, after following the below steps.

Do it yourself

Start the stopwatch - we have 2 minutes.

  1. Generate a PGP key 
    $  gpg --batch --generate-key <<EOF
  %no-protection
  Key-Type: default
  Subkey-Type: default
  Name-Real: Foo Bar
  Expire-Date: 0
EOF

    The key is created without a passphrase because of the %no-protection option. Otherwise a Passphrase: <pass> would be required.

  2. Create a sops configuration file with the key’s fingeprint. This is the ✨ magic ✨ ingredient, which makes the onboarding so frictionless. 
    $ gpg --list-keys
pub   rsa2048 2020-12-06 [SC]
      7E6DC556C66C43D928A95EA3715A56B718EAF0B6
uid           [ultimate] Foo Bar
sub   rsa2048 2020-12-06 [E]
   
$ cat .sops.yaml
creation_rules:
  - path_regex: secrets/.*\.dev\.enc\.yaml$
    pgp: 7E6DC556C66C43D928A95EA3715A56B718EAF0B6

    This is also perfect if you want more control over the secrets, like using different keys for different environments. For example secrets/*.dev.enc.yaml could use one key, and secrets/*.prod.enc.yaml another one. More details on this here.

  3. Use sops to edit and create new secrets 
    $ sops secrets/mysecrets.dev.enc.yaml

    Then it just a question of distributing the keys to the right people and/or environment. Which brings us to Keybase.

Note for Linux users

I’ve found that both on Fedora and Ubuntu, for whatever reason, creating a new file with sops throws the following cryptic error:

$ sops secrets/new.dev.enc.yaml
<save the file in the editor>
File has not changed, exiting.

The solution is to create the file first and encrypt it in-place afterwards:

$ vi secrets/new.dev.enc.yaml
$ sops -i -e secrets/new.dev.enc.yaml

Distributing the key to firends and family

To extract the PGP key from your local keychain, use:

$ gpg --list-keys
-------------------------------
pub   rsa2048 2020-12-06 [SC]
      7E6DC556C66C43D928A95EA3715A56B718EAF0B6
uid           [ultimate] Foo Bar
sub   rsa2048 2020-12-06 [E]

$ gpg --armor --export-secret-keys 7E6DC556C66C43D928A95EA3715A56B718EAF0B6 > key.asc

--armor makes it so that the output is ASCII (.asc) formatted, and not in binary (default).

One of the most seamless ways to distribute keys and other sensitive files is Keybase. It has a low barrier of entry, and you can control the granularity of access with “teams”. It also integrates nicely with the filesystem.

  1. Install Keybase 
    $ brew install keybase
  2. Create an account
  3. Create a new team and store the secret key under the team’s folder

After that, you grab the universal path and import the key to anywhere with gpg installed. Your peers can also grab the key after they join your team.

The command below imports the same PGP key we used at the beginning of the post. The sopsgpg team is open, so you can join if you want to test it out.

## The path is Keybase specific and it will work on any platform - no need to use your local filesystem path.
## Join the 'sopsgpg' team in Keybase first.
$ gpg --import <(keybase fs read /keybase/team/sopsgpg/pgp/key.asc)

Use it in your applications

To use the decrypted values in your application, you can just add a line to your setup scripts to run

sops -d secrets/mysecret.dev.enc.yaml > configuration.yaml

(make sure to add the decrypted files to .gitignore)

For Terraform projects use terraform-sops, and if you’re into Terragrunt, it has a built-in sops_decrypt_file function.

You will be running sops only to create or edit secrets, otherwise, it will be invisible (and incredible).

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