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# frozen_string_literal: true
require 'resolv'
class EmailMxValidator < ActiveModel::Validator
def validate(user)
user.errors.add(:email, I18n.t('users.invalid_email')) if invalid_mx?(user.email)
end
private
def invalid_mx?(value)
_, domain = value.split('@', 2)
return true if domain.nil?
hostnames = []
ips = []
Resolv::DNS.open do |dns|
dns.timeouts = 1
hostnames = dns.getresources(domain, Resolv::DNS::Resource::IN::MX).to_a.map { |e| e.exchange.to_s }
([domain] + hostnames).uniq.each do |hostname|
ips.concat(dns.getresources(hostname, Resolv::DNS::Resource::IN::A).to_a.map { |e| e.address.to_s })
ips.concat(dns.getresources(hostname, Resolv::DNS::Resource::IN::AAAA).to_a.map { |e| e.address.to_s })
end
end
ips.empty? || on_blacklist?(hostnames + ips)
end
def on_blacklist?(values)
EmailDomainBlock.where(domain: values.uniq).any?
end
end