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class ActionMailbox::Ingresses::Mailgun::InboundEmailsController < ActionMailbox::BaseController
before_action :ensure_authenticated
def create
ActionMailbox::InboundEmail.create_and_extract_message_id! raw_email
head :ok
end
private
def raw_email
StringIO.new params.require("body-mime")
end
def ensure_authenticated
head :unauthorized unless authenticated?
end
def authenticated?
Authenticator.new(authentication_params).authenticated?
rescue ArgumentError
false
end
def authentication_params
params.permit(:timestamp, :token, :signature).to_h.symbolize_keys
end
class Authenticator
cattr_accessor :key
attr_reader :timestamp, :token, :signature
def initialize(timestamp:, token:, signature:)
@timestamp, @token, @signature = timestamp, token, signature
end
def authenticated?
signed? && recent?
end
private
def signed?
ActiveSupport::SecurityUtils.secure_compare signature, expected_signature
end
# Allow for 10 minutes of drift between Mailgun time and local server time.
def recent?
time >= 10.minutes.ago
end
def expected_signature
OpenSSL::HMAC.hexdigest OpenSSL::Digest::SHA256.new, key, "#{timestamp}#{token}"
end
def time
Time.at Integer(timestamp)
end
end
end
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