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# frozen_string_literal: true
require 'resolv'
require 'ipaddress'
module Gitlab
class UrlBlocker
BlockedUrlError = Class.new(StandardError)
class << self
# Validates the given url according to the constraints specified by arguments.
#
# ports - Raises error if the given URL port does is not between given ports.
# allow_localhost - Raises error if URL resolves to a localhost IP address and argument is true.
# allow_local_network - Raises error if URL resolves to a link-local address and argument is true.
# ascii_only - Raises error if URL has unicode characters and argument is true.
# enforce_user - Raises error if URL user doesn't start with alphanumeric characters and argument is true.
# enforce_sanitization - Raises error if URL includes any HTML/CSS/JS tags and argument is true.
#
# Returns an array with [<uri>, <original-hostname>].
# rubocop:disable Metrics/CyclomaticComplexity
# rubocop:disable Metrics/ParameterLists
def validate!(
url,
ports: [],
schemes: [],
allow_localhost: false,
allow_local_network: true,
ascii_only: false,
enforce_user: false,
enforce_sanitization: false,
dns_rebind_protection: true)
# rubocop:enable Metrics/CyclomaticComplexity
# rubocop:enable Metrics/ParameterLists
return [nil, nil] if url.nil?
# Param url can be a string, URI or Addressable::URI
uri = parse_url(url)
validate_html_tags!(uri) if enforce_sanitization
hostname = uri.hostname
port = get_port(uri)
unless internal?(uri)
validate_scheme!(uri.scheme, schemes)
validate_port!(port, ports) if ports.any?
validate_user!(uri.user) if enforce_user
validate_hostname!(hostname)
validate_unicode_restriction!(uri) if ascii_only
end
begin
addrs_info = Addrinfo.getaddrinfo(hostname, port, nil, :STREAM).map do |addr|
addr.ipv6_v4mapped? ? addr.ipv6_to_ipv4 : addr
end
rescue SocketError
return [uri, nil]
end
protected_uri_with_hostname = enforce_uri_hostname(addrs_info, uri, hostname, dns_rebind_protection)
# Allow url from the GitLab instance itself but only for the configured hostname and ports
return protected_uri_with_hostname if internal?(uri)
validate_localhost!(addrs_info) unless allow_localhost
validate_loopback!(addrs_info) unless allow_localhost
validate_local_network!(addrs_info) unless allow_local_network
validate_link_local!(addrs_info) unless allow_local_network
protected_uri_with_hostname
end
def blocked_url?(*args)
validate!(*args)
false
rescue BlockedUrlError
true
end
private
# Returns the given URI with IP address as hostname and the original hostname respectively
# in an Array.
#
# It checks whether the resolved IP address matches with the hostname. If not, it changes
# the hostname to the resolved IP address.
#
# The original hostname is used to validate the SSL, given in that scenario
# we'll be making the request to the IP address, instead of using the hostname.
def enforce_uri_hostname(addrs_info, uri, hostname, dns_rebind_protection)
address = addrs_info.first
ip_address = address&.ip_address
return [uri, nil] unless dns_rebind_protection && ip_address && ip_address != hostname
uri = uri.dup
uri.hostname = ip_address
[uri, hostname]
end
def get_port(uri)
uri.port || uri.default_port
end
def validate_html_tags!(uri)
uri_str = uri.to_s
sanitized_uri = ActionController::Base.helpers.sanitize(uri_str, tags: [])
if sanitized_uri != uri_str
raise BlockedUrlError, 'HTML/CSS/JS tags are not allowed'
end
end
def parse_url(url)
raise Addressable::URI::InvalidURIError if multiline?(url)
Addressable::URI.parse(url)
rescue Addressable::URI::InvalidURIError, URI::InvalidURIError
raise BlockedUrlError, 'URI is invalid'
end
def multiline?(url)
CGI.unescape(url.to_s) =~ /\n|\r/
end
def validate_port!(port, ports)
return if port.blank?
# Only ports under 1024 are restricted
return if port >= 1024
return if ports.include?(port)
raise BlockedUrlError, "Only allowed ports are #{ports.join(', ')}, and any over 1024"
end
def validate_scheme!(scheme, schemes)
if scheme.blank? || (schemes.any? && !schemes.include?(scheme))
raise BlockedUrlError, "Only allowed schemes are #{schemes.join(', ')}"
end
end
def validate_user!(value)
return if value.blank?
return if value =~ /\A\p{Alnum}/
raise BlockedUrlError, "Username needs to start with an alphanumeric character"
end
def validate_hostname!(value)
return if value.blank?
return if IPAddress.valid?(value)
return if value =~ /\A\p{Alnum}/
raise BlockedUrlError, "Hostname or IP address invalid"
end
def validate_unicode_restriction!(uri)
return if uri.to_s.ascii_only?
raise BlockedUrlError, "URI must be ascii only #{uri.to_s.dump}"
end
def validate_localhost!(addrs_info)
local_ips = ["::", "0.0.0.0"]
local_ips.concat(Socket.ip_address_list.map(&:ip_address))
return if (local_ips & addrs_info.map(&:ip_address)).empty?
raise BlockedUrlError, "Requests to localhost are not allowed"
end
def validate_loopback!(addrs_info)
return unless addrs_info.any? { |addr| addr.ipv4_loopback? || addr.ipv6_loopback? }
raise BlockedUrlError, "Requests to loopback addresses are not allowed"
end
def validate_local_network!(addrs_info)
return unless addrs_info.any? { |addr| addr.ipv4_private? || addr.ipv6_sitelocal? || addr.ipv6_unique_local? }
raise BlockedUrlError, "Requests to the local network are not allowed"
end
def validate_link_local!(addrs_info)
netmask = IPAddr.new('169.254.0.0/16')
return unless addrs_info.any? { |addr| addr.ipv6_linklocal? || netmask.include?(addr.ip_address) }
raise BlockedUrlError, "Requests to the link local network are not allowed"
end
def internal?(uri)
internal_web?(uri) || internal_shell?(uri)
end
def internal_web?(uri)
uri.scheme == config.gitlab.protocol &&
uri.hostname == config.gitlab.host &&
(uri.port.blank? || uri.port == config.gitlab.port)
end
def internal_shell?(uri)
uri.scheme == 'ssh' &&
uri.hostname == config.gitlab_shell.ssh_host &&
(uri.port.blank? || uri.port == config.gitlab_shell.ssh_port)
end
def config
Gitlab.config
end
end
end
end
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