strongbox

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Encryption for git users.

Strongbox makes it easy to encrypt and decrypt files stored in git, with minimal divergence from a typical git workflow. Once installed, strongbox enables normal use of commands such as git diff etc. and all of the files that should be encrypted in the repository remain decrypted on your working copy.

It supports use of different keys per directory if wanted. It can cover as many or as few files as you wish based on .gitattributes

• Installation
• Usage
• Existing project
• Verification
• Key rotation
• Security
• Testing
• Known issues
  • Clone file ordering
    • Workaround

Installation

You can obtain a binary from https://github.com/uw-labs/strongbox/releases

Alternatively, assuming you have a working Go installation, you can install via the following command:

go install github.com/uw-labs/[email protected]

Usage

1. As a one time action, install the plugin by running strongbox -git-config. This will edit global git config to enable strongbox filter and diff configuration.

2. In each repository you want to use strongbox, create .gitattributes file containing the patterns to be managed by strongbox.

   For example:

   secrets/* filter=strongbox diff=strongbox
   

3. Generate a key to use for the encryption, for example:

   strongbox -gen-key my-key
   

   This will add a new key to your .strongbox_keyring. By default, the keyring is created in the $HOME directory, but this location can be changed by setting the $STRONGBOX_HOME environmental variable.

4. Include a .strongbox-keyid file in your repository containing public key you want to use (typically by copying a public key from $HOME/.strongbox_keyring ) This can be in the same directory as the protected resource(s) or any parent directory. When searching for .strongbox-keyid for a given resource, strongbox will recurse up the directory structure until it finds the file. This allows using different keys for different subdirectories within a repository.

Existing project

Strongbox uses clean and smudge filters to encrypt and decrypt files.

If you are cloning a project that uses strongbox, you will need to place the key into your keyring file prior to cloning (checkout). Otherwise that filter will fail and not decrypt files on checkout.

If you already have the project locally and added the keys, you can remove and checkout the files to force the filter:

rm <files> && git checkout -- <files>

Verification

Following a git add, you can verify the file is encrypted in the index:

git show :/path/to/file

Verify a file is encrypted in the commit:

git show HEAD:/path/to/file

What you should see is a Strongbox encrypted resource, and this is what would be pushed to the remote.

Compare an entire branch (as it would appear on the remote) to master:

git diff-index -p master

Key rotation

To rotate keys, update the .strongbox-keyid with the new key id, then touch all files/directories covered by .gitattributes. All affected files should now show up as "changed".

Security

Strongbox uses SIV-AES as defined in rfc5297 in order to achieve authenticated deterministic encryption.

Testing

Run integration tests:

make test

Known issues

Clone file ordering

Given a .strongbox-keyid in the root of the repository and an encrypted file in the same directory,and alphabetically it comes before the key-id file.

Git checks out files alphanumerically, so if the strongboxed file is being checked out before the .strongbox-keyid is present on disk, strongbox will fail to find the decryption key.

Order of files being cloned is dictated by the index.

Workaround

Clone repository, let the descryption fail. Delete encrypted files and do git checkout on the deleted files.