context

Context

Context securly stores and conveniently retrieves environment variables in etcd or Redis.

##Using the CLI.

Generating a key.

Context uses a single binary file to store both the symetric encryption key and the HMAC secret. This file can be generated using the key command. Correct permissions will be set for the resulting file before any data is written to it.

$ context key -k /path/to/key

The default key location for all commands is /etc/context/key.

Setting and removing values.

Values can be set from the command line using the set command. The prompt is password-style, and will not echo your input. Each value is encrypted and stored before input for the next is accepted.

$ context set -g myGroup A B C
A=
B=
C=

Retrieving values for execution in context.

Using the exec command, you can overwrite values in the current environment with values from the group environment for the execution of a single specified command.

Bellow is non-functional example of attempting to run a debian docker image with Context.

$ context exec -g myGroup docker run debian env | sort
HOME=/root
HOSTNAME=b9f394a118f2
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

Docker requires that environment variables that are to be passed from the execution environment to the container environment be specified individually. This can be a pain if you have a lot of them.

Context provides a templating mechanism to solve this problem. Using the -t flag you can specify that you would like the template token, {}, to be replaced in the specified command with a pattern that is resolved for every variable in the group environment.

$ context exec -g myGroup -t '-e {}' docker run {} debian env | sort
A=1
B=2
C=3
HOME=/root
HOSTNAME=d1b8361cc93c
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

Context will not provide the environment variable's value as a substitution for the template token, only its name.

##Design and comparison to other software.

• No external dependencies. Key generation and use is handled by Context itself, rather than using PGP or mandating setup using a utility such as openssl, etc.
• Strong, symetric key encryption by default. In standard mode, Context uses AES-256 (+ SHA-512 HMAC) to encrypt (and sign) values.
• Templated command execution. To make it easier to wrap underlying commands with information from the environment, Context allows the use of simple templates.

###Backends and crypters are simple interfaces.

Context makes as few assumptions about the chosen backend as possible, essentially assuming that what's provided is a basic, binary-safe key/value store. If a given backend requires content encodings (such as base-64, etc.), the backend-specific package handles any necessary conversions for both reading and writing. Encryption methods are handled much the same way.

There's a straight forward way to add both new backends and crypters that will be user-selectable at run time. We can garauntee that the std crypter will remain useable over time by allowing additions of new crypter packages down the line.

To-dos.

This is by no means complete, but there are a few things that should be added right out of the gate.

• Add a backend for Consul.
• Use a more robust parsing mechanism for templates.
• Add the ability to specify a user for the exec command.

Definitely contribute if you are so inclined! We'll follow git flow with pull requests.