deco

README

deco

deco is short for Docker Environment Control

Command Usage

deco has three options currently, validate, show, and run.

deco gets your app ready to run when a container
starts.  For example: the filters allow you to specify
individual files to filter and key/value pairs to use when
filtering.  By default, it works from the current directory and
will filter files in place.

Usage:
  deco [command]

Available Commands:
  encryption  Manage encryption
  help        Help about any command
  run         Run executes the tasks in the given control file
  show        Reads and displays a control file on STDOUT
  validate    Validates the control file
  version     Displays version information

Flags:
      --config string   deco config file -- _not_ the control file (default is $HOME/.deco.yaml)
  -d, --dir string      Base directory for filtered files/templates
  -h, --help            help for deco
      --key string      256bit encryption key

Use "deco [command] --help" for more information about a command.

Control File

deco takes a JSON file, the control file, as input and defaults to /var/run/secrets/deco.json. This allows it to work out of the box in docker swarm with swarm secrets. The control file can be base64 encoded (standard encoding) using the --encoded flag

The JSON control file has the format:

{
    "filters": {
        "path/to/file1": {
            "replace": "withThis",
            "doThis": "true"
        },
        "path/to/file2": {
            "base64encodedstuff": "IMKvXF8o44OEKV8vwq8="
        }
    }
}

It's possible it could do more than just filter in the future.

deco can currently source its JSON control file from:

• /var/run/secrets/deco.json (default)
• a local filesystem with an absolute or relative path
• an http(s) endpoint
• AWS SSM parameter store

deco also supports passing custom headers for doing things like basic auth to the http(s) endpoint

deco show http://127.0.0.1:8888/v1/deco.json -H 'Authorization=Basic YWRtaW46cGFzc3dvcmQ='

Control File Modifiers

The deco control file has basic support value modifiers. Instead of a string value, the value can be a JSON object referencing the type of modification and the value to be modified. The type will be the same as the filters in the template described in the Templates Section. Using modifiers will modify the value before the template is processed. Using template functions will modify the values during template processing.

{
    "filters": {
        "path/to/file1": {
            "decryptThis": {
              "type": "decrypt",
              "value": "wengoiwengoiwengoiwegnoewing"
            },
        },
        "path/to/file2": {
            "base64decodethis": {
              "type": "b64dec",
              "value": "IMKvXF8o44OEKV8vwq8="
            }
        }
    }
}

Templates

Templates are the file paths referenced as the key for the filters object in the control file. They should exist in place as templates before deco is run. They use standard Go template expansion.

Deco also supports a few custom functions in the template file:

b64enc	base64 encode the value
b64dec	base64 decode the value
decrypt	decrypt the value

These can be used by piping the value through the functions. ie.

{{ .foobarVariableToEncode | b64enc }}
{{ .foobarVariableToDecode | b64dec }}
{{ .foobarVariableToDecrypt | decrypt }}

Encryption

Values are encrypted using symmetric authenticated encryption using 256-bit AES-GCM with a random nonce. The key can be passed to deco on the command line using the --key flag or by setting the DECO_ENCRYPTION_KEY environment variable. During the validate, show and run steps, we recommend providing the key to the environment at runtime through a secrets manager.

The examples use the following key: d11bff052877151ef88e68374a509f38b91ff756d43757e5827bb30ba2b11aec.

The encryption subcommand provides management facilities to generate new encryption keys, decrypt values and encrypt values.

Manage encryption mechanisms for deco values.

Usage:
  deco encryption [command]

Available Commands:
  decrypt     Decrypt a value
  encrypt     Encrypt a value
  genkey      Generate a new encryption key

Flags:
  -h, --help   help for encryption

Global Flags:
      --config string   deco config file -- _not_ the control file (default is $HOME/.deco.yaml)
  -d, --dir string      Base directory for filtered files/templates
      --key string      256bit encryption key

Use "deco encryption [command] --help" for more information about a command.

Examples

Note: the examples directory has several working cases, including base64 encoding/decoding.

Basic usage with local filesystem

The most basic usage is a control file in the default location and simply running deco run.

deco run
[INFO] Using control from file /var/run/secrets/deco.json
...

Referencing a control file and setting a base directory

deco allows you to set a base directory for filtering. This directory will be prepended to the filter paths in the control file.

With the following params.json file:

{
    "filters": {
        "configdir/configfile.yaml": {
            "bar": "bar-app",
            "host01": "host01.example.org",
            "path01": "/tmp"
        }
    }
}

running

deco run params.json -d /app

If the template file /app/configdir/configfile.yaml exists, it will be written over in place, replacing {{ .bar }} with bar-app, {{ .host01 }} with host01.example.org, and {{ .path01 }} with /tmp.

Use AWS SSM parameter store to get control file

if [ -n "$SSMPATH" ]; then
  echo "Getting config file from SSM Parameter Store (${SSMPATH}) ..."
  deco version
  if [[ $? -ne 0 ]]; then
    echo "ERROR: deco not found!"
    exit 1
  fi
  deco validate -e ssm://${SSMPATH} || exit 1
  deco run -e ssm://${SSMPATH}
else
  echo "ERROR: SSMPATH variable not set!"
  exit 1
fi

Author

E Camden Fisher camden.fisher@yale.edu

License

The MIT License (MIT)

Copyright (c) 2022 Yale University

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.