class Rack::Protection::HostAuthorization

Prevented attack

DNS rebinding and other Host header attacks

Supported browsers

all

More infos

en.wikipedia.org/wiki/DNS_rebinding portswigger.net/web-security/host-header

Blocks HTTP requests with an unrecognized hostname in any of the following HTTP headers: Host, X-Forwarded-Host, Forwarded

If you want to permit a specific hostname, you can pass in as the ‘:permitted_hosts` option:

use Rack::Protection::HostAuthorization, permitted_hosts: ["www.example.org", "sinatrarb.com"]

The ‘:allow_if` option can also be set to a proc to use custom allow/deny logic.

Constants

DOT
PORT_REGEXP
SUBDOMAINS

Public Class Methods

new(*) click to toggle source
Calls superclass method Rack::Protection::Base::new
# File lib/rack/protection/host_authorization.rb, line 33
def initialize(*)
  super
  @permitted_hosts = []
  @domain_hosts = []
  @ip_hosts = []
  @all_permitted_hosts = Array(options[:permitted_hosts])

  @all_permitted_hosts.each do |host|
    case host
    when String
      if host.start_with?(DOT)
        domain = host[1..-1]
        @permitted_hosts << domain.downcase
        @domain_hosts << /\A#{SUBDOMAINS}#{Regexp.escape(domain)}\z/i
      else
        @permitted_hosts << host.downcase
      end
    when IPAddr then @ip_hosts << host
    end
  end
end

Public Instance Methods

accepts?(env) click to toggle source
# File lib/rack/protection/host_authorization.rb, line 55
def accepts?(env)
  return true if options[:allow_if]&.call(env)
  return true if @all_permitted_hosts.empty?

  request = Request.new(env)
  origin_host = extract_host(request.host_authority)
  forwarded_host = extract_host(request.forwarded_authority)

  debug env, "#{self.class} " \
             "@all_permitted_hosts=#{@all_permitted_hosts.inspect} " \
             "@permitted_hosts=#{@permitted_hosts.inspect} " \
             "@domain_hosts=#{@domain_hosts.inspect} " \
             "@ip_hosts=#{@ip_hosts.inspect} " \
             "origin_host=#{origin_host.inspect} " \
             "forwarded_host=#{forwarded_host.inspect}"

  if host_permitted?(origin_host)
    if forwarded_host.nil?
      true
    else
      host_permitted?(forwarded_host)
    end
  else
    false
  end
end

Private Instance Methods

domain_match?(host) click to toggle source
# File lib/rack/protection/host_authorization.rb, line 96
def domain_match?(host)
  return false if host.nil?
  return false if host.start_with?(DOT)

  @domain_hosts.any? { |domain_host| host.match?(domain_host) }
end
exact_match?(host) click to toggle source
# File lib/rack/protection/host_authorization.rb, line 92
def exact_match?(host)
  @permitted_hosts.include?(host)
end
extract_host(authority) click to toggle source
# File lib/rack/protection/host_authorization.rb, line 84
def extract_host(authority)
  authority.to_s.split(PORT_REGEXP).first&.downcase
end
host_permitted?(host) click to toggle source
# File lib/rack/protection/host_authorization.rb, line 88
def host_permitted?(host)
  exact_match?(host) || domain_match?(host) || ip_match?(host)
end
ip_match?(host) click to toggle source
# File lib/rack/protection/host_authorization.rb, line 103
def ip_match?(host)
  @ip_hosts.any? { |ip_host| ip_host.include?(host) }
rescue IPAddr::InvalidAddressError
  false
end