Ubuntu Manpage: ocat - OnionCat creates a transparent IPv6 layer on top of Tor's hidden services.

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Provided by: onioncat_0.2.2+svn569-1_amd64

NAME

       ocat - OnionCat creates a transparent IPv6 layer on top of Tor's hidden services.
       gcat - GarliCat is like OnionCat but it works with I2P instead of Tor.

SYNOPSIS

       ocat -i onion_id                      (1st form)
       ocat -o IPv6_address                  (2nd form)
       ocat [OPTION] onion_id                (3rd form)
       ocat -R [OPTION]                      (4th form)
       gcat [OPTION] i2p_id                  (5th form)

DESCRIPTION

OnionCat creates a transparent IPv6 layer on top of Tor's hidden services or I2P's tunnels. It transmits
any kind of IP-based data transparently through the Tor/I2P network on a location hidden basis. You can
think of it as a peer-to-peer VPN between hidden services.

OnionCat is a stand-alone application which runs in userland and is a connector between Tor/I2P and the
local OS. Any protocol which is based on IP can be transmitted. Of course, UDP and TCP (and probably
ICMP) are the most important ones but all other protocols can also be forwarded through it.

OnionCat opens a TUN device and assigns an IPv6 address to it. All packets forwarded to the TUN device by
the kernel are forwarded by OnionCat to other OnionCats listening on Tor's hidden service ports or I2P's
server tunnels. The IPv6 address depends on the onion_id or the i2p_id, respectively. The onion_id is the
hostname of the locally configured hidden service (see tor(8)). Depending on the configuration of Tor the
onion_id usually can be found at /var/lib/tor/hidden_service/hostname or similar location. The i2p_id is
the 80 bit long Base32 encoded hostname of the I2P server tunnel.

OPTIONS
-4 Enable IPv4 forwarding. See http://www.cypherpunk.at/onioncat/wiki/IPv4 for further information on
IPv4.
Native IPv4 forwarding is deprecated. The recommended solution for IPv4 forwarding is to build a
IPv4-through-IPv6 tunnel through OnionCat.

-a OnionCat creates a log file at $HOME/.ocat/connect_log. All incoming connects are logged to that
file. $HOME is determined from the user under which OnionCat runs (see option -u).

-b Run OnionCat in background. This is default. OnionCat will detach from a running shell and close
standard IO if no log file is given with option -L.

-B Run OnionCat in foreground. OnionCat will log to stderr by default.

-C Disable the local controller interface. The controller interfaces listens on localhost (127.0.0.1
and ::1 port 8066) for incoming connections. It's currently used for debugging purpose and not
thread-safe and does not have any kind of authentication or authorization mechanism. Hence, it
should not be used in production environments.

-d n Set debug level to n. Default = 7 which is maximum. Debug output will only be created if OnionCat
was compiled with option DEBUG (i.e. configure was run with option --enable-debug).

-f config file
Read initial configuration from config file.

-h Display short usage message and shows options.

-i Convert onion_id to IPv6 address and exit.

-I Run OnionCat in GarliCat mode. Using this option is identical to running OnionCat with the command
name gcat.

-l [ip:]port
Bind Onioncat to specific ip and/or port number for incoming connections. It defaults to
127.0.0.1:8060. This option could be set multiple times. IPv6 addresses must be given in square
brackets.
The parameter "none" deactivates the listener completely. This is for special purpose only and
shall not be used in regular operation.

-L log_file
Log output to log_file. If option is omitted, OnionCat logs to syslog if running in background or
to stderr if running in foreground. If syslogging is desired while running in foreground, specify
the special file name "syslog" as log file.

-o IPv6 address
Convert IPv6 address to onion_id and exit program.

-p Use TAP device instead of TUN device. There are a view differences. See TAP DEVICE later.

-P [pid file]
Create pid file at pid_file. If the option parameter is omitted OC will create a pid file at
/var/run/ocat.pid. In the latter case it MUST NOT be the last option in the list of options.

-r Run OnionCat as root and do not change user id (see option -u).

-R Use this option only if you really know what you do! OnionCat generates a random local onion_id.
With this option it is not necessary to add a hidden service to the Tor configuration file torrc.
One might use OnionCat services within Tor as usually but it is NOT possible to receive incoming
connections. If you plan to also receive connections (e.g. because you provide a service or you
use software which opens sockets for incoming connections like Bitorrent) you MUST configure a
hidden service and supply its hostname to OnionCat on the command line. Please note that this
option does only work if the remote OC does not run in unidirectional mode which is default since
SVN version 555 (see option -U).

-s port
Set OnionCat's virtual hidden service port to port. This should usually not be changed.

-t (IP|[IP:]port)
Set Tor SOCKS IP and/or port. If no IP is specified 127.0.0.1 will be used, if no port is
specified 9050 will be used as defaults. IPv6 addresses must be escaped by square brackets.
The special parameter "none" disables OnionCat from making outbound connections. This shall be
used only in special test scenarios.

-T tun_dev
TUN device file to open for creation of TUN interface. It defaults to /dev/net/tun on Linux and
/dev/tun0 on most other OSes, or /dev/tap0 if TAP mode is in use. Setup of a TUN device needs root
permissions. OnionCat automatically changes userid after the TUN device is set up correctly.

-U Deactivate unidirectional mode. Before SVN version 555 OnionCat ran only in bidirectional mode.
This is that a connection to another OC was used for outgoing and incoming packets. Since this
could be a security risk under certain conditions, unidirectional mode was implemented in SVN r555
and set to default. With this option bidirectional mode can be enabled again. Please note that
this does not interoperate with option -R if the remote OC is working in unidirectional mode.

-u username
username under which ocat should run. The uid is changed as soon as possible after tun device
setup.

TAP DEVICE
Usually OnionCat opens a TUN device which is a layer 3 interface. With option -p OnionCat opens a TAP
device instead which is a virtual ethernet (layer 2) interface.

NOTES

       This man page is still not finished...

FILES

       $HOME/.ocat/connect_log

AUTHOR

       Concepts,  software,  and  man  page  written  by  Bernhard  R.  Fischer  <bf@abenteuerland.at>.  Package
       maintenance  and  additional support by Ferdinand Haselbacher, Daniel Haslinger <creo-ocat@blackmesa.at>,
       and Wim Gaethofs.

COPYRIGHT

       Copyright 2008-2013 Bernhard R. Fischer.

       This file is part of OnionCat.

       OnionCat is free software: you can redistribute it and/or modify it under the terms of  the  GNU  General
       Public License as published by the Free Software Foundation, version 3 of the License.

       OnionCat  is  distributed  in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the
       implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.   See  the  GNU  General  Public
       License for more details.

       You  should  have  received  a  copy  of  the GNU General Public License along with OnionCat. If not, see
       <http://www.gnu.org/licenses/>.