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resolv.rb
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3508 lines (2876 loc) · 88.8 KB
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# frozen_string_literal: true
require 'socket'
require 'timeout'
require 'io/wait'
require 'securerandom'
require 'rbconfig'
# Resolv is a thread-aware DNS resolver library written in Ruby. Resolv can
# handle multiple DNS requests concurrently without blocking the entire Ruby
# interpreter.
#
# See also resolv-replace.rb to replace the libc resolver with Resolv.
#
# Resolv can look up various DNS resources using the DNS module directly.
#
# Examples:
#
# p Resolv.getaddress "www.ruby-lang.org"
# p Resolv.getname "210.251.121.214"
#
# Resolv::DNS.open do |dns|
# ress = dns.getresources "www.ruby-lang.org", Resolv::DNS::Resource::IN::A
# p ress.map(&:address)
# ress = dns.getresources "ruby-lang.org", Resolv::DNS::Resource::IN::MX
# p ress.map { |r| [r.exchange.to_s, r.preference] }
# end
#
#
# == Bugs
#
# * NIS is not supported.
# * /etc/nsswitch.conf is not supported.
class Resolv
# The version string
VERSION = "0.7.1"
##
# Looks up the first IP address for +name+.
def self.getaddress(name)
DefaultResolver.getaddress(name)
end
##
# Looks up all IP address for +name+.
def self.getaddresses(name)
DefaultResolver.getaddresses(name)
end
##
# Iterates over all IP addresses for +name+.
def self.each_address(name, &block)
DefaultResolver.each_address(name, &block)
end
##
# Looks up the hostname of +address+.
def self.getname(address)
DefaultResolver.getname(address)
end
##
# Looks up all hostnames for +address+.
def self.getnames(address)
DefaultResolver.getnames(address)
end
##
# Iterates over all hostnames for +address+.
def self.each_name(address, &proc)
DefaultResolver.each_name(address, &proc)
end
##
# Creates a new Resolv using +resolvers+.
#
# If +resolvers+ is not given, a hash, or +nil+, uses a Hosts resolver and
# and a DNS resolver. If +resolvers+ is a hash, uses the hash as
# configuration for the DNS resolver.
def initialize(resolvers=(arg_not_set = true; nil), use_ipv6: (keyword_not_set = true; nil))
if !keyword_not_set && !arg_not_set
warn "Support for separate use_ipv6 keyword is deprecated, as it is ignored if an argument is provided. Do not provide a positional argument if using the use_ipv6 keyword argument.", uplevel: 1
end
@resolvers = case resolvers
when Hash, nil
[Hosts.new, DNS.new(DNS::Config.default_config_hash.merge(resolvers || {}))]
else
resolvers
end
end
##
# Looks up the first IP address for +name+.
def getaddress(name)
each_address(name) {|address| return address}
raise ResolvError.new("no address for #{name}")
end
##
# Looks up all IP address for +name+.
def getaddresses(name)
ret = []
each_address(name) {|address| ret << address}
return ret
end
##
# Iterates over all IP addresses for +name+.
def each_address(name)
if AddressRegex =~ name
yield name
return
end
yielded = false
@resolvers.each {|r|
r.each_address(name) {|address|
yield address.to_s
yielded = true
}
return if yielded
}
end
##
# Looks up the hostname of +address+.
def getname(address)
each_name(address) {|name| return name}
raise ResolvError.new("no name for #{address}")
end
##
# Looks up all hostnames for +address+.
def getnames(address)
ret = []
each_name(address) {|name| ret << name}
return ret
end
##
# Iterates over all hostnames for +address+.
def each_name(address)
yielded = false
@resolvers.each {|r|
r.each_name(address) {|name|
yield name.to_s
yielded = true
}
return if yielded
}
end
##
# Indicates a failure to resolve a name or address.
class ResolvError < StandardError; end
##
# Indicates a timeout resolving a name or address.
class ResolvTimeout < Timeout::Error; end
##
# Resolv::Hosts is a hostname resolver that uses the system hosts file.
class Hosts
if /mswin|cygwin|mingw|bccwin/ =~ RUBY_PLATFORM || ::RbConfig::CONFIG['host_os'] =~ /mswin/
begin
require 'win32/resolv' unless defined?(Win32::Resolv)
hosts = Win32::Resolv.get_hosts_path || IO::NULL
rescue LoadError
end
end
# The default file name for host names
DefaultFileName = hosts || '/etc/hosts'
##
# Creates a new Resolv::Hosts, using +filename+ for its data source.
def initialize(filename = DefaultFileName)
@filename = filename
@mutex = Thread::Mutex.new
@initialized = nil
end
def lazy_initialize # :nodoc:
@mutex.synchronize {
unless @initialized
@name2addr = {}
@addr2name = {}
File.open(@filename, 'rb') {|f|
f.each {|line|
line.sub!(/#.*/, '')
addr, *hostnames = line.split(/\s+/)
next unless addr
(@addr2name[addr] ||= []).concat(hostnames)
hostnames.each {|hostname| (@name2addr[hostname] ||= []) << addr}
}
}
@name2addr.each {|name, arr| arr.reverse!}
@initialized = true
end
}
self
end
##
# Gets the IP address of +name+ from the hosts file.
def getaddress(name)
each_address(name) {|address| return address}
raise ResolvError.new("#{@filename} has no name: #{name}")
end
##
# Gets all IP addresses for +name+ from the hosts file.
def getaddresses(name)
ret = []
each_address(name) {|address| ret << address}
return ret
end
##
# Iterates over all IP addresses for +name+ retrieved from the hosts file.
def each_address(name, &proc)
lazy_initialize
@name2addr[name]&.each(&proc)
end
##
# Gets the hostname of +address+ from the hosts file.
def getname(address)
each_name(address) {|name| return name}
raise ResolvError.new("#{@filename} has no address: #{address}")
end
##
# Gets all hostnames for +address+ from the hosts file.
def getnames(address)
ret = []
each_name(address) {|name| ret << name}
return ret
end
##
# Iterates over all hostnames for +address+ retrieved from the hosts file.
def each_name(address, &proc)
lazy_initialize
@addr2name[address]&.each(&proc)
end
end
##
# Resolv::DNS is a DNS stub resolver.
#
# Information taken from the following places:
#
# * STD0013
# * RFC 1035
# * ftp://ftp.isi.edu/in-notes/iana/assignments/dns-parameters
# * etc.
class DNS
##
# Default DNS Port
Port = 53
##
# Default DNS UDP packet size
UDPSize = 512
##
# Creates a new DNS resolver. See Resolv::DNS.new for argument details.
#
# Yields the created DNS resolver to the block, if given, otherwise
# returns it.
def self.open(*args)
dns = new(*args)
return dns unless block_given?
begin
yield dns
ensure
dns.close
end
end
##
# Creates a new DNS resolver.
#
# +config_info+ can be:
#
# nil:: Uses /etc/resolv.conf.
# String:: Path to a file using /etc/resolv.conf's format.
# Hash:: Must contain :nameserver, :search and :ndots keys.
# :nameserver_port can be used to specify port number of nameserver address.
# :raise_timeout_errors can be used to raise timeout errors
# as exceptions instead of treating the same as an NXDOMAIN response.
#
# The value of :nameserver should be an address string or
# an array of address strings.
# - :nameserver => '8.8.8.8'
# - :nameserver => ['8.8.8.8', '8.8.4.4']
#
# The value of :nameserver_port should be an array of
# pair of nameserver address and port number.
# - :nameserver_port => [['8.8.8.8', 53], ['8.8.4.4', 53]]
#
# Example:
#
# Resolv::DNS.new(:nameserver => ['210.251.121.21'],
# :search => ['ruby-lang.org'],
# :ndots => 1)
def initialize(config_info=nil)
@mutex = Thread::Mutex.new
@config = Config.new(config_info)
@initialized = nil
end
# Sets the resolver timeouts. This may be a single positive number
# or an array of positive numbers representing timeouts in seconds.
# If an array is specified, a DNS request will retry and wait for
# each successive interval in the array until a successful response
# is received. Specifying +nil+ reverts to the default timeouts:
# [ 5, second = 5 * 2 / nameserver_count, 2 * second, 4 * second ]
#
# Example:
#
# dns.timeouts = 3
#
def timeouts=(values)
@config.timeouts = values
end
def lazy_initialize # :nodoc:
@mutex.synchronize {
unless @initialized
@config.lazy_initialize
@initialized = true
end
}
self
end
##
# Closes the DNS resolver.
def close
@mutex.synchronize {
if @initialized
@initialized = false
end
}
end
##
# Gets the IP address of +name+ from the DNS resolver.
#
# +name+ can be a Resolv::DNS::Name or a String. Retrieved address will
# be a Resolv::IPv4 or Resolv::IPv6
def getaddress(name)
each_address(name) {|address| return address}
raise ResolvError.new("DNS result has no information for #{name}")
end
##
# Gets all IP addresses for +name+ from the DNS resolver.
#
# +name+ can be a Resolv::DNS::Name or a String. Retrieved addresses will
# be a Resolv::IPv4 or Resolv::IPv6
def getaddresses(name)
ret = []
each_address(name) {|address| ret << address}
return ret
end
##
# Iterates over all IP addresses for +name+ retrieved from the DNS
# resolver.
#
# +name+ can be a Resolv::DNS::Name or a String. Retrieved addresses will
# be a Resolv::IPv4 or Resolv::IPv6
def each_address(name)
if use_ipv6?
each_resource(name, Resource::IN::AAAA) {|resource| yield resource.address}
end
each_resource(name, Resource::IN::A) {|resource| yield resource.address}
end
def use_ipv6? # :nodoc:
@config.lazy_initialize unless @config.instance_variable_get(:@initialized)
use_ipv6 = @config.use_ipv6?
unless use_ipv6.nil?
return use_ipv6
end
begin
list = Socket.ip_address_list
rescue NotImplementedError
return true
end
list.any? {|a| a.ipv6? && !a.ipv6_loopback? && !a.ipv6_linklocal? }
end
private :use_ipv6?
##
# Gets the hostname for +address+ from the DNS resolver.
#
# +address+ must be a Resolv::IPv4, Resolv::IPv6 or a String. Retrieved
# name will be a Resolv::DNS::Name.
def getname(address)
each_name(address) {|name| return name}
raise ResolvError.new("DNS result has no information for #{address}")
end
##
# Gets all hostnames for +address+ from the DNS resolver.
#
# +address+ must be a Resolv::IPv4, Resolv::IPv6 or a String. Retrieved
# names will be Resolv::DNS::Name instances.
def getnames(address)
ret = []
each_name(address) {|name| ret << name}
return ret
end
##
# Iterates over all hostnames for +address+ retrieved from the DNS
# resolver.
#
# +address+ must be a Resolv::IPv4, Resolv::IPv6 or a String. Retrieved
# names will be Resolv::DNS::Name instances.
def each_name(address)
case address
when Name
ptr = address
when IPv4, IPv6
ptr = address.to_name
when IPv4::Regex
ptr = IPv4.create(address).to_name
when IPv6::Regex
ptr = IPv6.create(address).to_name
else
raise ResolvError.new("cannot interpret as address: #{address}")
end
each_resource(ptr, Resource::IN::PTR) {|resource| yield resource.name}
end
##
# Look up the +typeclass+ DNS resource of +name+.
#
# +name+ must be a Resolv::DNS::Name or a String.
#
# +typeclass+ should be one of the following:
#
# * Resolv::DNS::Resource::IN::A
# * Resolv::DNS::Resource::IN::AAAA
# * Resolv::DNS::Resource::IN::ANY
# * Resolv::DNS::Resource::IN::CAA
# * Resolv::DNS::Resource::IN::CNAME
# * Resolv::DNS::Resource::IN::HINFO
# * Resolv::DNS::Resource::IN::HTTPS
# * Resolv::DNS::Resource::IN::LOC
# * Resolv::DNS::Resource::IN::MINFO
# * Resolv::DNS::Resource::IN::MX
# * Resolv::DNS::Resource::IN::NS
# * Resolv::DNS::Resource::IN::PTR
# * Resolv::DNS::Resource::IN::SOA
# * Resolv::DNS::Resource::IN::SRV
# * Resolv::DNS::Resource::IN::SVCB
# * Resolv::DNS::Resource::IN::TXT
# * Resolv::DNS::Resource::IN::WKS
#
# Returned resource is represented as a Resolv::DNS::Resource instance,
# i.e. Resolv::DNS::Resource::IN::A.
def getresource(name, typeclass)
each_resource(name, typeclass) {|resource| return resource}
raise ResolvError.new("DNS result has no information for #{name}")
end
##
# Looks up all +typeclass+ DNS resources for +name+. See #getresource for
# argument details.
def getresources(name, typeclass)
ret = []
each_resource(name, typeclass) {|resource| ret << resource}
return ret
end
##
# Iterates over all +typeclass+ DNS resources for +name+. See
# #getresource for argument details.
def each_resource(name, typeclass, &proc)
fetch_resource(name, typeclass) {|reply, reply_name|
extract_resources(reply, reply_name, typeclass, &proc)
}
end
# :stopdoc:
def fetch_resource(name, typeclass)
lazy_initialize
truncated = {}
requesters = {}
udp_requester = begin
make_udp_requester
rescue Errno::EACCES
# fall back to TCP
end
senders = {}
begin
@config.resolv(name) do |candidate, tout, nameserver, port|
msg = Message.new
msg.rd = 1
msg.add_question(candidate, typeclass)
requester = requesters.fetch([nameserver, port]) do
if !truncated[candidate] && udp_requester
udp_requester
else
requesters[[nameserver, port]] = make_tcp_requester(nameserver, port)
end
end
unless sender = senders[[candidate, requester, nameserver, port]]
sender = requester.sender(msg, candidate, nameserver, port)
next if !sender
senders[[candidate, requester, nameserver, port]] = sender
end
reply, reply_name = requester.request(sender, tout)
case reply.rcode
when RCode::NoError
if reply.tc == 1 and not Requester::TCP === requester
# Retry via TCP:
truncated[candidate] = true
redo
else
yield(reply, reply_name)
end
return
when RCode::NXDomain
raise Config::NXDomain.new(reply_name.to_s)
else
raise Config::OtherResolvError.new(reply_name.to_s)
end
end
ensure
udp_requester&.close
requesters.each_value { |requester| requester&.close }
end
end
def make_udp_requester # :nodoc:
nameserver_port = @config.nameserver_port
if nameserver_port.length == 1
Requester::ConnectedUDP.new(*nameserver_port[0])
else
Requester::UnconnectedUDP.new(*nameserver_port)
end
end
def make_tcp_requester(host, port) # :nodoc:
return Requester::TCP.new(host, port)
rescue Errno::ECONNREFUSED
# Treat a refused TCP connection attempt to a nameserver like a timeout,
# as Resolv::DNS::Config#resolv considers ResolvTimeout exceptions as a
# hint to try the next nameserver:
raise ResolvTimeout
end
def extract_resources(msg, name, typeclass) # :nodoc:
if typeclass < Resource::ANY
n0 = Name.create(name)
msg.each_resource {|n, ttl, data|
yield data if n0 == n
}
end
yielded = false
n0 = Name.create(name)
msg.each_resource {|n, ttl, data|
if n0 == n
case data
when typeclass
yield data
yielded = true
when Resource::CNAME
n0 = data.name
end
end
}
return if yielded
msg.each_resource {|n, ttl, data|
if n0 == n
case data
when typeclass
yield data
end
end
}
end
def self.random(arg) # :nodoc:
begin
SecureRandom.random_number(arg)
rescue NotImplementedError
rand(arg)
end
end
RequestID = {} # :nodoc:
RequestIDMutex = Thread::Mutex.new # :nodoc:
def self.allocate_request_id(host, port) # :nodoc:
id = nil
RequestIDMutex.synchronize {
h = (RequestID[[host, port]] ||= {})
begin
id = random(0x0000..0xffff)
end while h[id]
h[id] = true
}
id
end
def self.free_request_id(host, port, id) # :nodoc:
RequestIDMutex.synchronize {
key = [host, port]
if h = RequestID[key]
h.delete id
if h.empty?
RequestID.delete key
end
end
}
end
case RUBY_PLATFORM
when *[
# https://www.rfc-editor.org/rfc/rfc6056.txt
# Appendix A. Survey of the Algorithms in Use by Some Popular Implementations
/freebsd/, /linux/, /netbsd/, /openbsd/, /solaris/,
/darwin/, # the same as FreeBSD
] then
def self.bind_random_port(udpsock, bind_host="0.0.0.0") # :nodoc:
udpsock.bind(bind_host, 0)
end
else
# Sequential port assignment
def self.bind_random_port(udpsock, bind_host="0.0.0.0") # :nodoc:
# Ephemeral port number range recommended by RFC 6056
port = random(1024..65535)
udpsock.bind(bind_host, port)
rescue Errno::EADDRINUSE, # POSIX
Errno::EACCES, # SunOS: See PRIV_SYS_NFS in privileges(5)
Errno::EPERM # FreeBSD: security.mac.portacl.port_high is configurable. See mac_portacl(4).
retry
end
end
class Requester # :nodoc:
def initialize
@senders = {}
@socks = nil
end
def request(sender, tout)
start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
timelimit = start + tout
begin
sender.send
rescue Errno::EHOSTUNREACH, # multi-homed IPv6 may generate this
Errno::ENETUNREACH
raise ResolvTimeout
end
while true
before_select = Process.clock_gettime(Process::CLOCK_MONOTONIC)
timeout = timelimit - before_select
if timeout <= 0
raise ResolvTimeout
end
if @socks.size == 1
select_result = @socks[0].wait_readable(timeout) ? [ @socks ] : nil
else
select_result = IO.select(@socks, nil, nil, timeout)
end
if !select_result
after_select = Process.clock_gettime(Process::CLOCK_MONOTONIC)
next if after_select < timelimit
raise ResolvTimeout
end
begin
reply, from = recv_reply(select_result[0])
rescue Errno::ECONNREFUSED, # GNU/Linux, FreeBSD
Errno::ECONNRESET, # Windows
EOFError
# No name server running on the server?
# Don't wait anymore.
raise ResolvTimeout
end
begin
msg = Message.decode(reply)
rescue DecodeError
next # broken DNS message ignored
end
if sender == sender_for(from, msg)
break
else
# unexpected DNS message ignored
end
end
return msg, sender.data
end
def sender_for(addr, msg)
@senders[[addr,msg.id]]
end
def close
socks = @socks
@socks = nil
socks&.each(&:close)
end
class Sender # :nodoc:
def initialize(msg, data, sock)
@msg = msg
@data = data
@sock = sock
end
end
class UnconnectedUDP < Requester # :nodoc:
def initialize(*nameserver_port)
super()
@nameserver_port = nameserver_port
@initialized = false
@mutex = Thread::Mutex.new
end
def lazy_initialize
@mutex.synchronize {
next if @initialized
@initialized = true
@socks_hash = {}
@socks = []
@nameserver_port.each {|host, port|
if host.index(':')
bind_host = "::"
af = Socket::AF_INET6
else
bind_host = "0.0.0.0"
af = Socket::AF_INET
end
next if @socks_hash[bind_host]
begin
sock = UDPSocket.new(af)
rescue Errno::EAFNOSUPPORT, Errno::EPROTONOSUPPORT
next # The kernel doesn't support the address family.
end
@socks << sock
@socks_hash[bind_host] = sock
sock.do_not_reverse_lookup = true
DNS.bind_random_port(sock, bind_host)
}
}
self
end
def recv_reply(readable_socks)
lazy_initialize
reply, from = readable_socks[0].recvfrom(UDPSize)
return reply, [from[3],from[1]]
end
def sender(msg, data, host, port=Port)
host = Addrinfo.ip(host).ip_address
lazy_initialize
sock = @socks_hash[host.index(':') ? "::" : "0.0.0.0"]
return nil if !sock
service = [host, port]
id = DNS.allocate_request_id(host, port)
request = msg.encode
request[0,2] = [id].pack('n')
return @senders[[service, id]] =
Sender.new(request, data, sock, host, port)
end
def close
@mutex.synchronize {
if @initialized
super
@senders.each_key {|service, id|
DNS.free_request_id(service[0], service[1], id)
}
@initialized = false
end
}
end
class Sender < Requester::Sender # :nodoc:
def initialize(msg, data, sock, host, port)
super(msg, data, sock)
@host = host
@port = port
end
attr_reader :data
def send
raise "@sock is nil." if @sock.nil?
@sock.send(@msg, 0, @host, @port)
end
end
end
class ConnectedUDP < Requester # :nodoc:
def initialize(host, port=Port)
super()
@host = host
@port = port
@mutex = Thread::Mutex.new
@initialized = false
end
def lazy_initialize
@mutex.synchronize {
next if @initialized
@initialized = true
is_ipv6 = @host.index(':')
sock = UDPSocket.new(is_ipv6 ? Socket::AF_INET6 : Socket::AF_INET)
@socks = [sock]
sock.do_not_reverse_lookup = true
DNS.bind_random_port(sock, is_ipv6 ? "::" : "0.0.0.0")
sock.connect(@host, @port)
}
self
end
def recv_reply(readable_socks)
lazy_initialize
reply = readable_socks[0].recv(UDPSize)
return reply, nil
end
def sender(msg, data, host=@host, port=@port)
lazy_initialize
unless host == @host && port == @port
raise RequestError.new("host/port don't match: #{host}:#{port}")
end
id = DNS.allocate_request_id(@host, @port)
request = msg.encode
request[0,2] = [id].pack('n')
return @senders[[nil,id]] = Sender.new(request, data, @socks[0])
end
def close
@mutex.synchronize do
if @initialized
super
@senders.each_key {|from, id|
DNS.free_request_id(@host, @port, id)
}
@initialized = false
end
end
end
class Sender < Requester::Sender # :nodoc:
def send
raise "@sock is nil." if @sock.nil?
@sock.send(@msg, 0)
end
attr_reader :data
end
end
class MDNSOneShot < UnconnectedUDP # :nodoc:
def sender(msg, data, host, port=Port)
lazy_initialize
id = DNS.allocate_request_id(host, port)
request = msg.encode
request[0,2] = [id].pack('n')
sock = @socks_hash[host.index(':') ? "::" : "0.0.0.0"]
return @senders[id] =
UnconnectedUDP::Sender.new(request, data, sock, host, port)
end
def sender_for(addr, msg)
lazy_initialize
@senders[msg.id]
end
end
class TCP < Requester # :nodoc:
def initialize(host, port=Port)
super()
@host = host
@port = port
sock = TCPSocket.new(@host, @port)
@socks = [sock]
@senders = {}
end
def recv_reply(readable_socks)
len_data = readable_socks[0].read(2)
raise EOFError if len_data.nil? || len_data.bytesize != 2
len = len_data.unpack('n')[0]
reply = @socks[0].read(len)
raise EOFError if reply.nil? || reply.bytesize != len
return reply, nil
end
def sender(msg, data, host=@host, port=@port)
unless host == @host && port == @port
raise RequestError.new("host/port don't match: #{host}:#{port}")
end
id = DNS.allocate_request_id(@host, @port)
request = msg.encode
request[0,2] = [request.length, id].pack('nn')
return @senders[[nil,id]] = Sender.new(request, data, @socks[0])
end
class Sender < Requester::Sender # :nodoc:
def send
@sock.print(@msg)
@sock.flush
end
attr_reader :data
end
def close
super
@senders.each_key {|from,id|
DNS.free_request_id(@host, @port, id)
}
end
end
##
# Indicates a problem with the DNS request.
class RequestError < StandardError
end
end
class Config # :nodoc:
def initialize(config_info=nil)
@mutex = Thread::Mutex.new
@config_info = config_info
@initialized = nil
@timeouts = nil
end
def timeouts=(values)
if values
values = Array(values)
values.each do |t|
Numeric === t or raise ArgumentError, "#{t.inspect} is not numeric"
t > 0.0 or raise ArgumentError, "timeout=#{t} must be positive"
end
@timeouts = values
else
@timeouts = nil
end
end
