ejson

ejson is a utility for managing a collection of secrets in source control. The
secrets are encrypted using public
key, elliptic
curve cryptography
(NaCl Box:
Curve25519 +
Salsa20 +
Poly1305-AES). Secrets are
collected in a JSON file, in which all the string values are encrypted. Public
keys are embedded in the file, and the decrypter looks up the corresponding
private key from its local filesystem.

The main benefits provided by ejson are:

• Secrets can be safely stored in a git repo.
• Changes to secrets are auditable on a line-by-line basis with git blame.
• Anyone with git commit access has access to write new secrets.
• Decryption access can easily be locked down to production servers only.
• Secrets change synchronously with application source (as opposed to secrets
  provisioned by Configuration Management).
• Simple, well-tested, easily-auditable source.

See the manpages for more technical documentation.

See ejson2env for a useful tool to help with exporting
a portion of secrets as environment variables for environments/tools that require this pattern.

Installation

You can download the .deb package from Github Releases.

On development machines (64-bit linux or OS X), the recommended installation
method is via Homebrew:

brew tap shopify/shopify
brew install ejson

Workflow

1: Create the Keydir

By default, EJSON looks for keys in /opt/ejson/keys. You can change this by
setting EJSON_KEYDIR or passing the -keydir option.

$ mkdir -p /opt/ejson/keys

2: Generate a keypair

When called with -w, ejson keygen will write the keypair into the keydir
and print the public key. Without -w, it will print both keys to stdout. This
is useful if you have to distribute the key to multiple servers via
configuration management, etc.

$ ejson keygen
Public Key:
63ccf05a9492e68e12eeb1c705888aebdcc0080af7e594fc402beb24cce9d14f
Private Key:
75b80b4a693156eb435f4ed2fe397e583f461f09fd99ec2bd1bdef0a56cf6e64

$ ejson keygen -w
53393332c6c7c474af603c078f5696c8fe16677a09a711bba299a6c1c1676a59
$ cat /opt/ejson/keys/5339*
888a4291bef9135729357b8c70e5a62b0bbe104a679d829cdbe56d46a4481aaf

3: Create an ejson file

The format is described in more detail later on. For now, create a
file that looks something like this. Fill in the <key> with whatever you got
back in step 2.

Create this file as test.ejson:

{
  "_public_key": "<key>",
  "database_password": "1234password"
}

4: Encrypt the file

Running ejson encrypt test.ejson will encrypt any new plaintext keys in the
file, and leave any existing encrypted keys untouched:

{
  "_public_key": "63ccf05a9492e68e12eeb1c705888aebdcc0080af7e594fc402beb24cce9d14f",
  "database_password": "EJ[1:WGj2t4znULHT1IRveMEdvvNXqZzNBNMsJ5iZVy6Dvxs=:kA6ekF8ViYR5ZLeSmMXWsdLfWr7wn9qS:fcHQtdt6nqcNOXa97/M278RX6w==]"
}

Try adding another plaintext secret to the file and run ejson encrypt test.ejson again. The database_password field will not be changed, but the
new secret will be encrypted.

5: Decrypt the file

To decrypt the file, you must have a file present in the keydir whose name is
the 64-byte hex-encoded public key exactly as embedded in the ejson document.
The contents of that file must be the similarly-encoded private key. If you used
ejson keygen -w, you’ve already got this covered.

Unlike ejson encrypt, which overwrites the specified files, ejson decrypt
only takes one file parameter, and prints the output to stdout:

$ ejson decrypt foo.ejson
{
  "_public_key": "63ccf05a9492e68e12eeb1c705888aebdcc0080af7e594fc402beb24cce9d14f",
  "database_password": "1234password"
}

Format

The ejson document format is simple, but there are a few points to be aware
of:

1. It’s just JSON.
2. There must be a key at the top level named _public_key, whose value is a
   32-byte hex-encoded (i.e. 64 ASCII byte) public key as generated by ejson keygen.
3. Any string literal that isn’t an object key will be encrypted by default (ie.
   in {"a": "b"}, "b" will be encrypted, but "a" will not.
4. Numbers, booleans, and nulls aren’t encrypted.
5. If a key begins with an underscore, its corresponding value will not be
   encrypted. This is used to prevent the _public_key field from being
   encrypted, and is useful for implementing metadata schemes.
6. Underscores do not propagate downward. For example, in {"_a": {"b": "c"}},
   "c" will be encrypted.

See also

• If you use Capistrano for deployment you can use capistrano-ejson to automatically decrypt the secrets on deploy.
• If you use pre-commit, you can use it to automatically encrypt secrets on commit.