path: root/doc/en/README

AF - Active Port Forwarder 0.6 - README
Copyright (C) 2003,2004,2005 jeremian - <jeremian [at] poczta.fm>
=================================================================

================================================================================

GRAY-WORLD.NET / Active Port Forwarder
======================================

  The Active Port Forwarder program is  part  of  the  Gray-World.net  projects.

  Our Gray-World Team presents on the http://gray-world.net website the projects
  and publications we are working on which are  related  to  the  NACS  (Network
  Access Control System) bypassing  research  field  and  to  the  computer  and
  network security topics.

================================================================================

=======
SUMMARY
=======

INTRO

1. INSTALLATION
  1.1 Instructions
  1.2 Required libs
  1.3 Tested platforms
2. USAGE
  2.1 afserver
  2.2 afclient
3. REMOTE ADMINISTRATION
4. MODULES
5. EXAMPLES
  5.1 tcp mode
  5.2 reverse udp mode
6. BUGS/PROBLEMS

NOTES

THANKS

================================================================================

=====
INTRO
=====

Active  port  forwarder  is  a  software  tool  for  secure   port   forwarding.
It uses ssl to increase security of communication between a server and a client.
Originally, it was developed to forward data point to point.  However, the  need
for bypassing firewalls in order to  connect  to  internally  located  computers
influenced the further development of the project.

AF is dedicated for people, who don't have an external ip  number  and  want  to
make some services available across the net.

Moreover, zlib is used to compress the transferred data.

Using one, permanent data/control channel with flow control /  packet  buffering
provides good performance and reasonably small latency.

Multiple clients allow to create more sophisticated tunneling scheme.

================================================================================

===============
1. INSTALLATION
===============

  1.1 Instructions
  ----------------

1. Download the compressed sources from http://www.gray-world.net/pr_af.shtml
2. Unpack them with tar zxvf
3. Type "./configure"
4. Type "make"
5. Type "make install" while logged as root
6. If something goes wrong - mail the author or post a message on
   http://gray-world.net/board/

  1.2 Required libs
  -----------------

1. openssl   -   http://www.openssl.org/
2. zlib      -   http://www.gzip.org/zlib/

  1.3 Tested platforms
  --------------------
  
1. Linux:
  Gentoo, Slackware, Mandrake - built without any problems
2. Windows:
  win32 - cygwin version is available on the project homepage
  
================================================================================

========
2. USAGE
========

  2.1 afserver
  ------------

 Basic options:

  -n, --hostname      - it's used when creating listening sockets
                        (default: '')
  -l, --listenport    - listening port number - users connect
                        to it (default: 50127)
  -m, --manageport    - manage port number - second part of the active
                        port forwarder connects to it (default: 50126)
  -h, --help          - prints this help

 Authorization:

  --pass              - set the password used for client identification
                        (default: no password)

 Configuration:

  -c, --cerfile       - the name of the file with certificate
                        (default: cacert.pem)
  -k, --keyfile       - the name of the file with RSA key (default: server.rsa)
  -f, --cfgfile       - the name of the file with the configuration for the
                        active forwarder (server)
  -D, --dateformat    - format of the date printed in logs (see 'man strftime'
                        for details) (default: %d.%m.%Y %H:%M:%S)

  -t, --timeout       - the timeout value for the client's connection
                        (default: 5)
  -u, --users         - the amount of users allowed to use this server
                        (default: 5)
  -C, --clients       - the number of allowed clients to use this server
                        (default: 1)
  -r, --realm         - set the realm name (default: none)
  -R, --raclients     - the number of allowed clients in remote administration
                        mode to use this server (default: 1)
  -U, --usrpcli       - the number of allowed users per client (default: $users)
  -M, --climode       - strategy used for connecting users with clients
                        (default: 1)
                      Available strategies:
                        1. fill first client before go to next

  -p, --proto         - type of server (tcp|udp) - for which protocol it will
                        be operating (default: tcp)
  -b, --baseport      - listenports are temporary and differ for each client
  --nossl             - ssl is not used for transferring data (but it's still
                        used to establish a connection) (default: ssl is used)
  --nozlib            - zlib is not used for compressing data (default:
                        zlib is used)
  --dnslookups        - try to obtain dns names of the computers rather than
                        their numeric IP

 Logging:

  -O, --heavylog      - logging everything to a logfile
  -o, --lightlog      - logging some data to a logfile
  -S, --heavysocklog  - logging everything to a localport
  -s, --lightsocklog  - logging some data to a localport
  -v, --verbose       - to be verbose - program won't enter the daemon mode
                        (use several times for greater effect)

 IP family:

  -4, --ipv4          - use ipv4 only
  -6, --ipv6          - use ipv6 only

  2.2 afclient
  ------------

 Basic options:

  -n, --servername    - where the second part of the active
                        port forwarder is running (required)
  -m, --manageport    - manage port number - server must be
                        listening on it (default: 50126)
  -d, --hostname      - the name of this host/remote host - the final
                        destination of the packets (default: the name
                        returned by hostname function)
  -p, --portnum       - the port we are forwarding connection to (required)
  -h, --help          - prints this help

 Authorization:

  -i, --id            - send the id string to afserver
  --pass              - set the password used for client identification
                        (default: no password)

 Configuration:

  -k, --keyfile       - the name of the file with RSA key (default: client.rsa)
  -D, --dateformat    - format of the date printed in logs (see 'man strftime'
                        for details) (default: %d.%m.%Y %H:%M:%S)

 Modes:

  -u, --udpmode       - udp mode - client will use udp protocol to
                        communicate with the hostname
  -U, --reverseudp    - reverse udp forwarding. Udp packets will be forwarded
                        from hostname:portnum (-p) to the server name:portnum
                        (-m)
  -r, --remoteadmin   - remote administration mode. (using '-p #port' will
                        force afclient to use port rather then stdin-stdout)

 Logging:

  -O, --heavylog      - logging everything to a logfile
  -o, --lightlog      - logging some data to a logfile
  -S, --heavysocklog  - logging everything to a localport
  -s, --lightsocklog  - logging some data to a localport
  -v, --verbose       - to be verbose - program won't enter the daemon mode
                        (use several times for greater effect)

 IP family:

  -4, --ipv4          - use ipv4 only
  -6, --ipv6          - use ipv6 only

 Modules:

  -l, --load          - load a module for user's packets filtering
  -L, --Load          - load a module for service's packets filtering

================================================================================

========================
3. REMOTE ADMINISTRATION
========================

Afclient can be started in remote administration  mode  by  '-r,  --remoteadmin'
option. Required option: '-n, --servername NAME'.

After successful authorization stdin/stdout is used to  communicate  with  user.
All the commands parsing is done by afserver.

Currently available commands are:

       help
         display help

       lcmd
         lists available commands

       info
         prints info about server

       rshow
         display realms

       cshow X
         display clients in X realm

       ushow X
         display users in X realm

       quit
         quit connection

Afclient with '-p, --portnum PORT' option listens for connection  from  user  at
NAME:PORT.  NAME is set by '-d, --hostname' option or hostname() function,  when
the option is missing.

When user quits (close the connection or send 'quit' command),  afclient  exits.

================================================================================

==========
4. MODULES
==========

Afclient can use external modules for user's packets  filtering  ('-l,  --load')
and service's packets filtering ('-L, --Load'). Module file has to declare three
functions:

char* info(void);
  
  info() return values:
  - info about module

  Example:

  char*
  info(void)
  {
    return "Module tester v0.1";
  }

int allow(char* host, char* port);

  allow() return values:
  0 - allow to connect
  !0 - drop the connection

  Example:

  int
  allow(char* host, char* port)
  {
    return 0; /* allow to connect */
  }

int filter(char* host, unsigned char* message, int* length);

  filter() return values:
  0 - allow to transfer
  1 - drop the packet
  2 - drop the connection
  3 - release the module
  4 - drop the packet and release the module
  5 - drop the connection and release the module

  Example:

  int
  filter(char* host, unsigned char* message, int* length)
  {
    int i;
    for (i = 1; i < *length; ++i) {
      if (message[i-1] == 'M') {
        if (message[i] == '1') {
          return 1; /* ignored */
        }
        if (message[i] == '2') {
          return 2; /* dropped */
        }
        if (message[i] == '3') {
          return 3; /* release */
        }
        if (message[i] == '4') {
          return 4; /* ignored + release */
        }
        if (message[i] == '5') {
          return 5; /* dropped + release */
        }
      }
    }
    return 0; /* allow to transfer */
  }

Modules have to be compiled with '-fPIC -shared' options.

================================================================================

===========
5. EXAMPLES
===========

  5.1 tcp mode
  ------------

                    local network   |FireWall|   Internet
                                        ||
                                        ||                           User 1
                                        ||                           /(tcp)
             AF Client <---Encrypted/Compressed channel---> AF Server
             /                          ||                    |      \(tcp)
            /(tcp)                      ||               (tcp)|       User 2
           /                            ||                     \
    Http server                         ||                      User 3
                                        ||


The use of it is extremely simple. Let's suppose we want to create a http server
on our computer and we are behind a masquerade or a firewall:

1) We have to find some machine on the net with  an  external  ip  and  a  shell
   account.
   
2) Use "make" to compile everything on that machine. (you can freely remove the
   afclient and client.rsa files)

3) You can edit the config file or just type from the console (to use the config
   type -f <cfgfile>) :
        $ ./afserver
   This will work, if you want to use default values:
   - hostname will be taken from hostname function  (it  would  be  ideally,  if
     there is appropriate registration in /etc/hosts)
   - server will be listening for users on port 50127
   - server will be listening for client on port 50126
   - server will be for maximum 5 users
   - server will forward tcp packets
   - there will be no logging and no verbose messages
   - there will be no password identification
   - ip protocol family will be unspecified

4) We use "make" on our machine (we can delete everything apart from afclient
   and client.rsa)

5) We are typing from the console:
        $ ./afclient -n <name of the server> -p 80
   Where <name of the server>  is  a  string  like  :  'bastion.univ.gda.pl'  or
   '153.19.7.200'

6) We can now enter with a web-browser to: <name of  the  server>:50127  and  we
   will enter to our computer in the fact.

  5.2 reverse udp mode
  --------------------

                    local network   |FireWall|   Internet
                                        ||                     (udp)
                                        ||              User 1-------AF Client
                                        ||                           /(tcp)
             AF Client <---Encrypted/Compressed channel---> AF Server
             /                          ||                    |      
            /(udp)                      ||               (tcp)|       
           /                            ||                   /
    Game server                         ||               AF Client-------User 2
                                        ||                         (udp)


Let's see how to use af to forward udp packets. Suppose we want to create a game
server on our computer (udp port 27960 on our machine):

1) - 4)  is  the  same  like  in  example  1.  (but  we  add  option:  -p  udp)

5) We are typing from the console:
  $ ./afclient -u -n <name of the server> -p 27960
   Where <name of the server> is a name (or ip) of a host where  our  server  is
   running.

6) Connecting to our game is more complicated. The user must use afclient to do
   this.  He has to specify the server he is connecting to and the  port,  which
   his program will be listening on:
       $ ./afclient -U -d <hostname> -p <portnum> -n <name of the server>  \
         -m <server port>
   Where <hostname> is the name of the user machine (who wants to connect to our
   game). <portnum> is the port he will be connecting to. <name of the server>
   is the name of the host where our server is running.  <server  port>  is  the
   port on which the server is listening for users.  In order to connect to  our
   game, the user has to connect to <hostname>:<portnum>.

================================================================================

================
6. BUGS/PROBLEMS
================

There are no known/open bugs at the moment.

================================================================================

=====
NOTES
=====

Active port forwarder is still under development, so please sent  any  comments,
bugs notices and suggestions about it to <jeremian [at] poczta.fm>

If you have some problems or want to share your opinions with others, feel  free
to post a message at http://gray-world.net/board/

================================================================================

======
THANKS
======

 Big thanks to the GW Team:

 to Alex <alex [at] gray-world.net>
 and Simon <scastro [at] entreelibre.com> for testing AF and a lot of advices.

 Thanks to Ilia Perevezentsev <iliaper [at] mail.ru> who read and corrected the
README file.

 Thanks to Marco Solari <marco.solari [at] koinesistemi.it> for a lot of
requests, suggestions and ideas.

 And thanks for using this software!

LICENSE
-------

  Active Port Forwarder is distributed  under  the  terms  of  the  GNU  General
  Public License v2.0  and is copyright (C)  2003,2004,2005  jeremian  <jeremian
  [at] poczta.fm>. See the file COPYING for details.