hmac_authentication RubyGem

Signs and authenticates HTTP requests based on a shared-secret HMAC signature.

Developed in parallel with the following packages for other languages:

• Go: github.com/18F/hmacauth
• Node.js: hmac-authentication

Warning: Repeated HTTP headers will cause an authentication failure! Because of the way that Ruby's Net::HTTPHeader.initialize_http_header method is implemented, it will discard all but the last of a series of repeated headers. The packages for other languages will combine repeated headers into one. Therefore, if your Ruby service receives an signed request from a server using one of these other modules, and the request has repeated headers, authentication of the request will fail.

Installation

If you're using Bundler in your project, add the following to your Gemfile:

gem 'hmac_authentication'

If you're not using Bundler, start.

Authenticating incoming requests

Inject something resembling the following code fragment into your request handling logic as the first thing that happens before the request body is parsed, where headers is a list of headers factored into the signature and secret_key is the shared secret between your application and the service making the request:

require 'hmac_authentication'

# When only used for authentication, it doesn't matter what the first argument
# is, because the hash algorithm used for authentication will be parsed from
# the incoming request signature header.
auth = HmacAuthentication::HmacAuth.new(
  'sha1', secret_key, signature_header, headers)

def request_handler(request)
  result, header_sig, computed_sig = auth.authenticate_request request
  if result != HmacAuthentication::HmacAuth::MATCH
    # Cancel the request, optionally logging the values above.
  end
end

Signing outgoing requests

Do something similar to the following.

digest_name = 'sha1' # Or any other available Hash algorithm.
auth = HmacAuthentication::HmacAuth.new(
  digest_name, secret_key, signature_header, headers)

def make_request(request)
  // Prepare request...
  auth.sign_request request
end

Public domain

This project is in the worldwide public domain. As stated in CONTRIBUTING:

This project is in the public domain within the United States, and copyright and related rights in the work worldwide are waived through the CC0 1.0 Universal public domain dedication.

All contributions to this project will be released under the CC0 dedication. By submitting a pull request, you are agreeing to comply with this waiver of copyright interest.