IO::Socket::Socks(3p)

NAME
IO::Socket::Socks - Provides a way to create socks client or server both 4 and 5 version.

SYNOPSIS

  Client
  use IO::Socket::Socks;

  my $socks_client = IO::Socket::Socks->new(
    ProxyAddr   => "proxy host",
    ProxyPort   => "proxy port",
    ConnectAddr => "remote host",
    ConnectPort => "remote port",
  ) or die $SOCKS_ERROR;

  print $socks_client "foo\n";
  $socks_client->close();

  Server
  use IO::Socket::Socks ':constants';

  my $socks_server = IO::Socket::Socks->new(
    ProxyAddr   => "localhost",
    ProxyPort   => 8000,
    Listen      => 1,
    UserAuth    => \&auth,
    RequireAuth => 1
  ) or die $SOCKS_ERROR;

  while(1) {
    my $client = $socks_server->accept();

    unless ($client) {
      print "ERROR: $SOCKS_ERROR\n";
      next;
    }

    my $command = $client->command();
    if ($command->[0] == CMD_CONNECT) {
       # Handle the CONNECT
       $client->command_reply(REPLY_SUCCESS, addr, port);
    }

    ...
    #read from the client and send to the CONNECT address
    ...

    $client->close();
  }

  sub auth {
    my ($user, $pass) = @_;

    return 1 if $user eq "foo" && $pass eq "bar";
    return 0;
  }

DESCRIPTION
"IO::Socket::Socks" connects to a SOCKS proxy, tells it to open a connection to a remote host/port when the object is created. The object you receive can be used directly as a socket (with "IO::Socket" interface) for sending and receiving data from the remote host. In addition to create socks client this module could be used to create socks server. See examples below.

EXAMPLES
For complete examples of socks 4/5 client and server see `examples' subdirectory in the distribution.

METHODS

  Socks Client
new( %cfg )

new_from_socket($socket, %cfg)

new_from_fd($socket, %cfg)

Creates a new IO::Socket::Socks client object. new_from_socket() is the same as new(), but allows one to create object from an existing and not connected socket (new_from_fd is new_from_socket alias). To make IO::Socket::Socks object from connected socket see "start_SOCKS"

Both takes the following config hash:

  SocksVersion => 4 or 5. Default is 5

  Timeout => connect/accept timeout

  Blocking => Since IO::Socket::Socks version 0.5 you can perform non-blocking connect/bind by
              passing false value for this option. Default is true - blocking. See ready()
              below for more details.

  SocksResolve => resolve host name to ip by proxy server or
                  not (will resolve by client). This
                  overrides value of $SOCKS4_RESOLVE or $SOCKS5_RESOLVE
                  variable. Boolean.

  SocksDebug => This will cause all of the SOCKS traffic to
                be presented on the command line in a form
                similar to the tables in the RFCs. This overrides value
                of $SOCKS_DEBUG variable. Boolean.

  ProxyAddr => Hostname of the proxy

  ProxyPort => Port of the proxy

  ConnectAddr => Hostname of the remote machine

  ConnectPort => Port of the remote machine

  BindAddr => Hostname of the remote machine which will
              connect to the proxy server after bind request

  BindPort => Port of the remote machine which will
              connect to the proxy server after bind request

  UdpAddr => Expected address where datagrams will be sent. Fill it with address
             of all zeros if address is not known at this moment.
             Proxy server may use this information to limit access to the association.

  UdpPort => Expected port where datagrams will be sent. Use zero port
             if port is not known at this moment. Proxy server may use this
             information to limit access to the association.

  AuthType => What kind of authentication to support:
              none       - no authentication (default)
              userpass  - Username/Password. For socks5
              proxy only.

  RequireAuth => Do not send ANON as a valid auth mechanism.
                 For socks5 proxy only

  Username => For socks5 if AuthType is set to userpass, then
              you must provide a username. For socks4 proxy with
              this option you can specify userid.

  Password => If AuthType is set to userpass, then you must
              provide a password. For socks5 proxy only.

The following options should be specified:

  (ProxyAddr and ProxyPort)
  (ConnectAddr and ConnectPort) or (BindAddr and BindPort) or (UdpAddr and UdpPort)

Other options are facultative.

start_SOCKS($socket, %cfg)

This is a class method to start socks handshake on already connected socket. This will bless passed $socket to IO::Socket::Socks class. %cfg is like hash in the constructor. Only options listed below makes sence:

  Timeout
  ConnectAddr
  ConnectPort
  BindAddr
  BindPort
  UdpAddr
  UdpPort
  SocksVersion
  SocksDebug
  SocksResolve
  AuthType
  RequireAuth
  Username
  Password
  AuthMethods

On success this method will return same $socket, but as IO::Socket::Socks object. On failure it will return undef (but socket will be still blessed to IO::Socket::Socks class). See example:

  use IO::Socket;
  use IO::Socket::Socks;

  my $sock = IO::Socket::INET->new("$proxy_host:$proxy_port") or die $@;
  $sock = IO::Socket::Socks->start_SOCKS($sock, ConnectAddr => "google.com", ConnectPort => 80) or die $SOCKS_ERROR;

version( )

Returns socks version for this socket

ready( )

Returns true when socket becomes ready to transfer data (socks handshake done), false otherwise. This is useful for non-blocking connect/bind. When this method returns false value you can determine what socks handshake need for with $SOCKS_ERROR variable. It may need for read, then $SOCKS_ERROR will be SOCKS_WANT_READ or need for write, then it will be SOCKS_WANT_WRITE.

Example:

    use IO::Socket::Socks;
    use IO::Select;

    my $sock = IO::Socket::Socks->new(
        ProxyAddr => 'localhost', ProxyPort => 1080, ConnectAddr => 'mail.com', ConnectPort => 80, Blocking => 0
    ) or die $SOCKS_ERROR;

    my $sel = IO::Select->new($sock);
    until ($sock->ready) {
        if ($SOCKS_ERROR == SOCKS_WANT_READ) {
            $sel->can_read();
        }
        elsif ($SOCKS_ERROR == SOCKS_WANT_WRITE) {
            $sel->can_write();
        }
        else {
            die $SOCKS_ERROR;
        }

        # NOTE: when base class ($IO::Socket::Socks::SOCKET_CLASS) is IO::Socket::IP
        # and you are using kqueue or epoll to check for readable/writable sockets
        # you need to readd $sock to kqueue/epoll after each call to ready() (actually until socket will be connected to proxy server),
        # because IO::Socket::IP may change internal socket of $sock for milti-homed hosts.
        # There is no such problem when you are using select/poll
    }

    # you may want to return socket to blocking state by $sock->blocking(1)
    $sock->syswrite("I am ready");

accept( )

Accept an incoming connection after bind request. On failed returns undef. On success returns socket. No new socket created, returned socket is same on which this method was called. Because accept(2) is not invoked on the client side, socks server calls accept(2) and proxify all traffic via socket opened by client bind request. You can call accept only once on IO::Socket::Socks client socket.

command( %cfg )

Allows one to execute socks command on already opened socket. Thus you can create socks chain. For example see "EXAMPLES" section.

%cfg is like hash in the constructor. Only options listed below makes sence:

  ConnectAddr
  ConnectPort
  BindAddr
  BindPort
  UdpAddr
  UdpPort
  SocksVersion
  SocksDebug
  SocksResolve
  AuthType
  RequireAuth
  Username
  Password
  AuthMethods

Values of the other options (Timeout for example) inherited from the constructor. Options like ProxyAddr and ProxyPort are not included.

dst( )

Return (host, port, address_type) of the remote host after connect/accept or socks server (host, port, address_type) after bind/udpassoc.

  Socks Server
new( %cfg )

new_from_socket($socket, %cfg)

new_from_fd($socket, %cfg)

Creates a new IO::Socket::Socks server object. new_from_socket() is the same as new(), but allows one to create object from an existing socket (new_from_fd is new_from_socket alias). Both takes the following config hash:

  SocksVersion => 4 for socks4, 5 for socks5 or [4,5] if you want accept both 4 and 5. Default is 5

  Timeout => Timeout value for various operations

  Blocking => Since IO::Socket::Socks version 0.6 you can perform non-blocking accept by
              passing false value for this option. Default is true - blocking. See ready()
              below for more details.

  SocksResolve => For socks v5: return destination address to the client
                  in form of 4 bytes if true, otherwise in form of host
                  length and host name.
                  For socks v4: allow use socks4a protocol extension if
                  true and not otherwise.
                  This overrides value of $SOCKS4_RESOLVE or $SOCKS5_RESOLVE.
                  See also command_reply().

  SocksDebug => This will cause all of the SOCKS traffic to
                be presented on the command line in a form
                similar to the tables in the RFCs. This overrides value
                of $SOCKS_DEBUG variable. Boolean.

  ProxyAddr => Local host bind address

  ProxyPort => Local host bind port

  UserAuth => Reference to a function that returns 1 if client
              allowed to use socks server, 0 otherwise. For
              socks5 proxy it takes login and password as
              arguments. For socks4 argument is userid.

  RequireAuth => Not allow anonymous access for socks5 proxy.

  Listen => Same as IO::Socket::INET listen option. Should be
            specified as number > 0.

The following options should be specified:

  Listen
  ProxyAddr
  ProxyPort

Other options are facultative.

accept( )

Accept an incoming connection and return a new IO::Socket::Socks object that represents that connection. You must call command() on this to find out what the incoming connection wants you to do, and then call command_reply() to send back the reply.

version( )

Returns socks version for socket. It is useful when your server accepts both 4 and 5 version. Then you should know socks version to make proper response. Just call version() on socket received after accept().

ready( )

After non-blocking accept you will get new client socket object, which may be not ready to transfer data (if socks handshake is not done yet). ready() will return true value when handshake will be done successfully and false otherwise. Note, socket returned by accept() call will be always in blocking mode. So if your program can't block you should set non-blocking mode for this socket before ready() call: $socket->blocking(0). When ready() returns false value you can determine what socks handshake needs for with $SOCKS_ERROR variable. It may need for read, then $SOCKS_ERROR will be SOCKS_WANT_READ or need for write, then it will be SOCKS_WANT_WRITE.

Example:

  use IO::Socket::Socks;
  use IO::Select;

  my $server = IO::Socket::Socks->new(ProxyAddr => 'localhost', ProxyPort => 1080, Blocking => 0)
      or die $@;
  my $select = IO::Select->new($server);
  $select->can_read(); # wait for client

  my $client = $server->accept()
    or die "accept(): $! ($SOCKS_ERROR)";
  $client->blocking(0); # !!!
  $select->add($client);
  $select->remove($server); # no more connections

  while (1) {
      if ($client->ready) {
          my $command = $client->command;

          ... # do client command

          $client->command_reply(IO::Socket::Socks::REPLY_SUCCESS, $command->[1], $command->[2]);

          ... # transfer traffic

          last;
      }
      elsif ($SOCKS_ERROR == SOCKS_WANT_READ) {
          $select->can_read();
      }
      elsif ($SOCKS_ERROR == SOCKS_WANT_WRITE) {
          $select->can_write();
      }
      else {
          die "Unexpected error: $SOCKS_ERROR";
      }
  }

command( )

After you call accept() the client has sent the command they want you to process. This function should be called on the socket returned by accept(). It returns a reference to an array with the following format:

  [ COMMAND, ADDRESS, PORT, ADDRESS TYPE ]

command_reply( REPLY CODE, ADDRESS, PORT )

After you call command() the client needs to be told what the result is. The REPLY CODE is one of the constants as follows (integer value):

  For socks v4
  REQUEST_GRANTED(90): request granted
  REQUEST_FAILED(91): request rejected or failed
  REQUEST_REJECTED_IDENTD(92): request rejected because SOCKS server cannot connect to identd on the client
  REQUEST_REJECTED_USERID(93): request rejected because the client program and identd report different user-ids

  For socks v5
  REPLY_SUCCESS(0): Success
  REPLY_GENERAL_FAILURE(1): General Failure
  REPLY_CONN_NOT_ALLOWED(2): Connection Not Allowed
  REPLY_NETWORK_UNREACHABLE(3): Network Unreachable
  REPLY_HOST_UNREACHABLE(4): Host Unreachable
  REPLY_CONN_REFUSED(5): Connection Refused
  REPLY_TTL_EXPIRED(6): TTL Expired
  REPLY_CMD_NOT_SUPPORTED(7): Command Not Supported
  REPLY_ADDR_NOT_SUPPORTED(8): Address Not Supported

HOST and PORT are the resulting host and port (where server socket responsible for this command bound).

Note: for 5 version "command_reply" will try to resolve passed address if "SocksResolve" has true value and passed address is domain name. To avoid this just pass ip address ("$socket->sockhost") instead of host name or turn off "SocksResolve" for this server. For version 4 passed host name will always be resolved to ip address even if "SocksResolve" has false value. Because this version doesn't support "ADDRESS" as domain name.

VARIABLES

  $SOCKS_ERROR
This scalar behaves like $! in that if undef is returned. $SOCKS_ERROR is IO::Socket::Socks::Error object with some overloaded operators. In string context this variable should contain a string reason for the error. In numeric context it contains error code.

  $SOCKS4_RESOLVE
If this variable has true value resolving of host names will be done by proxy server, otherwise resolving will be done locally. Resolving host by socks proxy version 4 is extension to the protocol also known as socks4a. So, only socks4a proxy supports resolving of hostnames. Default value of this variable is false. This variable is not importable. See also `SocksResolve' parameter in the constructor.

  $SOCKS5_RESOLVE
If this variable has true value resolving of host names will be done by proxy server, otherwise resolving will be done locally. Note: some bugous socks5 servers doesn't support resolving of host names. Default value is true. This variable is not importable. See also `SocksResolve' parameter in the constructor.

  $SOCKS_DEBUG
Default value is $ENV{SOCKS_DEBUG}. If this variable has true value and no SocksDebug option in the constructor specified, then SocksDebug will has true value. This variable is not importable.

  $SOCKET_CLASS
With this variable you can get/set base socket class for "IO::Socket::Socks". By default it tries to use "IO::Socket::IP" 0.36+ as socket class. And falls back to "IO::Socket::INET" if not available. You can set $IO::Socket::Socks::SOCKET_CLASS before loading of "IO::Socket::Socks" and then it will not try to detect proper base class itself. You can also set it after loading of "IO::Socket::Socks" and this will automatically update @ISA, so you shouldn't worry about inheritance.

CONSTANTS
The following constants could be imported manually or using `:constants' tag:

  SOCKS5_VER
  SOCKS4_VER
  ADDR_IPV4
  ADDR_DOMAINNAME
  ADDR_IPV6
  CMD_CONNECT
  CMD_BIND
  CMD_UDPASSOC
  AUTHMECH_ANON
  AUTHMECH_USERPASS
  AUTHMECH_INVALID
  AUTHREPLY_SUCCESS
  AUTHREPLY_FAILURE
  ISS_UNKNOWN_ADDRESS # address type sent by client/server not supported by I::S::S
  ISS_BAD_VERSION     # socks version sent by client/server != specified version
  ISS_CANT_RESOLVE    # I::S::S failed to resolve some host
  REPLY_SUCCESS
  REPLY_GENERAL_FAILURE
  REPLY_CONN_NOT_ALLOWED
  REPLY_NETWORK_UNREACHABLE
  REPLY_HOST_UNREACHABLE
  REPLY_CONN_REFUSED
  REPLY_TTL_EXPIRED
  REPLY_CMD_NOT_SUPPORTED
  REPLY_ADDR_NOT_SUPPORTED
  REQUEST_GRANTED
  REQUEST_FAILED
  REQUEST_REJECTED_IDENTD
  REQUEST_REJECTED_USERID
  SOCKS_WANT_READ
  SOCKS_WANT_WRITE
  ESOCKSPROTO

SOCKS_WANT_READ, SOCKS_WANT_WRITE and ESOCKSPROTO are imported by default.

IPv6
Since version 0.66 "IO::Socket::Socks" supports IPv6 with help of IO::Socket::IP 0.36+. And will use "IO::Socket::IP" as base class if available. However you can force set "$SOCKET_CLASS = "IO::Socket::INET"" to use IPv4 only. See also "$SOCKET_CLASS"

FAQ

How to determine is connection to socks server (client accept) failed or some protocol error occurred?
    You can check $! variable. If $! == ESOCKSPROTO constant, then it was error in the protocol. Error description could be found in $SOCKS_ERROR.

How to determine which error in the protocol occurred?
    You should compare $SOCKS_ERROR with constants below:

      AUTHMECH_INVALID
      AUTHREPLY_FAILURE
      ISS_UNKNOWN_ADDRESS
      ISS_BAD_VERSION
      REPLY_GENERAL_FAILURE
      REPLY_CONN_NOT_ALLOWED
      REPLY_NETWORK_UNREACHABLE
      REPLY_HOST_UNREACHABLE
      REPLY_CONN_REFUSED
      REPLY_TTL_EXPIRED
      REPLY_CMD_NOT_SUPPORTED
      REPLY_ADDR_NOT_SUPPORTED
      REQUEST_FAILED
      REQUEST_REJECTED_IDENTD
      REQUEST_REJECTED_USERID

BUGS
The following options are not implemented:

GSSAPI authentication
UDP server side support

Patches are welcome.

SEE ALSO
IO::Socket::Socks::Wrapper

AUTHOR
Original author is Ryan Eatmon

Now maintained by Oleg G <oleg@cpan.org>

COPYRIGHT
This module is free software, you can redistribute it and/or modify it under the terms of LGPL.