github-token

#!/usr/bin/env ruby

# This script is used to generate GitHub app access token
# used by Danger.
#
# Required env vars:
#
# GITHUB_APP_PRIVATE_KEY_PATH or GITHUB_APP_PRIVATE_KEY - path to the app's private key or the key itself
# GITHUB_APP_ID – the app's ID (you can find it on the app's page)
# GITHUB_APP_INSTALLATION_ID – the installation's ID (the instance of the app for the repo/organization).
#
# You can find the installation ID on the Project -> Settings -> Integrations & Services page:
# under "Installed GitHub Apps" find the app and click "Configure".
# The resulting URL will contain the installation ID, e.g. /organizations/myorg/settings/installations/12345.
#
# See https://developer.github.com/apps/building-github-apps/authenticating-with-github-apps/

require "openssl"
require "net/http"
require "json"

# Make this script work both as a standalone executable
# and as a part of the bundle
begin
  require "jwt"
rescue LoadError
  require "bundler/inline"

  gemfile do
    source "https://rubygems.org"
    gem "jwt"
  end

  require "jwt"
end

begin
  # Private key contents
  private_pem =
    if ENV["GITHUB_APP_PRIVATE_KEY_PATH"]
      File.read(ENV["GITHUB_APP_PRIVATE_KEY_PATH"])
    else
      ENV.fetch("GITHUB_APP_PRIVATE_KEY").gsub(/\\n/, "\n")
    end

  private_key = OpenSSL::PKey::RSA.new(private_pem)

  payload = {
    iat: Time.now.to_i,
    # JWT expiration time (10 minute maximum)
    exp: Time.now.to_i + (10 * 60),
    iss: ENV.fetch("GITHUB_APP_ID")
  }

  jwt = JWT.encode(payload, private_key, "RS256")

  uri = URI("https://api.github.com/app/installations/#{ENV.fetch("GITHUB_APP_INSTALLATION_ID")}/access_tokens")

  req = Net::HTTP::Post.new(uri)
  req["Authorization"] = "Bearer #{jwt}"
  req["Accept"] = "application/vnd.github.machine-man-preview+json"

  res = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) do |http|
    http.request(req)
  end

  case res
  when Net::HTTPSuccess, Net::HTTPRedirection
    puts JSON.parse(res.body).fetch("token")
  else
    warn res.value
    warn res.body
  end
rescue => e
  warn "Failed to generate GitHub token!"
  warn e.message

  exit(1)
end