Smart Edge Code Challenge Result

By Ethan Stein

Overview

The purpose of this project is to demonstrate the coding challenge involved in taking an email address with a public/private keypair and generating a json string result in the format:

{
   "message":"[EMAIL_ADDRESS]",
   "signature":"[RFC 4648 compliant Base64 encoded cryptographic signature of the input]",
   "pubkey":"[Base64 encoded string (PEM format) of the public key]"
}

The program has been built using Ruby and leverages the OpenSSL, Base64, and Json libraries.

Usage

The program can either called directly, via:

./signed_identifier.rb <EMAIL_ADDRESS>

where <EMAIL_ADDRESS> is a simple string, or by building an image from the Dockerfile accompanying this README:

docker build . -t codechallenge
docker run codechallenge "[email protected]"

In either case, the public and private key-pairs must be in the same location as the program/dockerfile, or the program will not run.

Testing

A serverspec test suite has been created to verify the following:

1. The private and public keys are available in the current directory (as well as the Dockerfile for good measure)
2. The program's input email address is of a valid format and not null/empty
3. Docker creates a valid json response using the email, defined by the format above
4. The json message field is the same as the provided email
5. The json signature field successfully verifies against the email address and private key.

To run the test suite execute the following commands:

bundle install
export CHALLANGE_EMAIL="[email protected]"
rspec spec/unit/signed_identifier_spec.rb

The result should be similar to

Using bundler 1.16.4
...
Using serverspec 2.41.3
Bundle complete! 3 Gemfile dependencies, 18 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.

Smart Edge Challenge Test Suite
  verify necessary files exist in current location
    File "./private_key.pem"
      should exist
      should be file
    File "./public_key.pem"
      should exist
      should be file
    File "Dockerfile"
      should exist
      should be file
  verify provided email
    should be formatted correctly
  verify email encryption with docker run
    should generate a json response
    json response should be valid
    json signature should verify successfully

Finished in 5.06 seconds (files took 0.8341 seconds to load)
10 examples, 0 failures

Simply update the CHALLANGE_EMAIL environment variable and run the rspec command again to test a different email address.

Note: the test suite will take care of building the Docker image, creating the container, and cleaning up the image and container after. No manual cleanup should be required.

Regarding CI Integration

For ease of straight rspec testing, I have exposed an environment variable in my rspec file to allow command-line testing. If I was going to use this inside a CI system like chef, I would instead leverage attribute files or environment variables.

Rspec could then be called via chef rspec spec/unit/signed_identifier_spec.rb

Also, note, that my solution demonstrates how one could use a Docker container to both build and test the solution. However, a real-world scenario would be incorporating the ruby solution/tests as custom resources inside another cookbook/recipe. It would most likely not be an isolated component.