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class ActionMailbox::Ingresses::Mailgun::InboundEmailsController < ActionMailbox::BaseController
before_action :authenticate
def create
ActionMailbox::InboundEmail.create_and_extract_message_id! params.require("body-mime")
end
private
def authenticate
head :unauthorized unless authenticated?
end
def authenticated?
if key.present?
Authenticator.new(
key: key,
timestamp: params.require(:timestamp),
token: params.require(:token),
signature: params.require(:signature)
).authenticated?
else
raise ArgumentError, <<~MESSAGE.squish
Missing required Mailgun API key. Set action_mailbox.mailgun_api_key in your application's
encrypted credentials or provide the MAILGUN_INGRESS_API_KEY environment variable.
MESSAGE
end
end
def key
Rails.application.credentials.dig(:action_mailbox, :mailgun_api_key) || ENV["MAILGUN_INGRESS_API_KEY"]
end
class Authenticator
attr_reader :key, :timestamp, :token, :signature
def initialize(key:, timestamp:, token:, signature:)
@key, @timestamp, @token, @signature = key, Integer(timestamp), token, signature
end
def authenticated?
signed? && recent?
end
private
def signed?
ActiveSupport::SecurityUtils.secure_compare signature, expected_signature
end
# Allow for 2 minutes of drift between Mailgun time and local server time.
def recent?
Time.at(timestamp) >= 2.minutes.ago
end
def expected_signature
OpenSSL::HMAC.hexdigest OpenSSL::Digest::SHA256.new, key, "#{timestamp}#{token}"
end
end
end
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