ecfg

ecfg is a utility for managing a collection of secrets, generally with the intent of committing them to source control. The secrets are encrypted using public key, elliptic curve cryptography (NaCl Box: Curve25519 + Salsa20 + Poly1305-AES). Secrets are collected in a JSON, YAML, or TOML 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 or the process environment.

The main benefits provided by ecfg 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.

ecfg is written in lowercase, and normally pronounced "e-config", like "email".

Differences from EJSON 1.0

• Supports YAML and TOML
• Expected filename changes from *.ejson to *.ecfg.<format> (e.g. .ecfg.json)
• encrypt and decrypt can now both receive data on stdin, and will emit output to stdout in this case.
• Added --type/-t flag to encrypt and decrypt commands. If the filename is *{json,yaml,yml,toml}, this flag is optional, but when the type can't be inferred because of a different filename or when reading from stdin, it must be specified. (note that this recognizes *.ejson as json automatically)
• All references to EJSON have changed to ECFG, including ECFG_KEYDIR.
• Key lookup has been changed to allow a greater degree of control:
• ECFG_PRIVATE_KEY may be set as an environment variable. This can be used to preempt key selection logic during decrypt. If present, ecfg will blindly attempt to decrypt any encrypted values using this key, instead of trying to find the matching key in the keydir. This is useful for deploying to Heroku.
• Unless ECFG_KEYDIR is set, ecfg will now be look in four directories (in order of decreasing precedence):
  • $XDG_CONFIG_HOME/ecfg/keys (if set, and non-root)
  • $HOME/.ecfg/keys (if non-root)
  • /etc/ecfg/keys
  • /opt/ejson/keys
• If ECFG_KEYDIR is set, then ecfg will look in $ECFG_KEYDIR/keys
• Overhauled build process

Installation

You can download the .deb package from Github Releases.

On macOS, you can install ecfg using brew install shopify/shopify/ecfg.

You can also install ecfg as a gem using gem install ecfg or adding it to your Gemfile.

Workflow

1: Create the Keydir

By default, ecfg looks for keys in /etc/ecfg/keys. You can change this by setting ECFG_KEYDIR or passing the --keydir option.

$ mkdir -p /etc/ecfg/keys

2: Generate a keypair

When called with -w, ecfg 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.

ecfg keygen will write the keypair to the first directory on the keypath that's writable:

1. $XDG_CONFIG_HOME/ecfg/keys (if non-root and $XDG_CONFIG_HOME is set)
2. $HOME/.ecfg/keys (if non-root)
3. /etc/ecfg/keys
4. /opt/ejson/keys

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

$ ecfg keygen -w
53393332c6c7c474af603c078f5696c8fe16677a09a711bba299a6c1c1676a59
$ cat ~/.ecfg/keys/5339*
888a4291bef9135729357b8c70e5a62b0bbe104a679d829cdbe56d46a4481aaf

$ sudo ecfg keygen -w
53393332c6c7c474af603c078f5696c8fe16677a09a711bba299a6c1c1676a59
$ cat /etc/ecfg/keys/5339*
888a4291bef9135729357b8c70e5a62b0bbe104a679d829cdbe56d46a4481aaf

3: Create an ecfg 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.ecfg.json:

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

4: Encrypt the file

Running ecfg encrypt test.ecfg.json 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 ecfg encrypt test.ecfg.json 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 ecfg document. The contents of that file must be the similarly-encoded private key. If you used ecfg keygen -w, you've already got this covered.

Alternatively, in some environments, it may be easier to pass the private key via ECFG_PRIVATE_KEY, which preempts the keydir lookup.

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

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

Format

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

1. It's just JSON (or YAML or TOML, in the case of ecfg.yaml and ecfg.toml)
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 ecfg 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. Non-string data types aren't encrypted in json or toml, but are in yaml, simply because it makes the transformer code simpler.
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.

Building ecfg

If you work at Shopify, just run dev up && dev build; otherwise:

1. Install ruby (the system one will do on OS X, or you can brew install ruby. hpricot doesn't seem to want to build with 2.3.x)
2. Install bundler (gem install bundler)
3. bundle install
4. Install Go (brew install go)
5. Configure your $GOPATH and make sure this is on it at github.com/Shopify/ecfg.
6. make