It acts like a deamon and offers two simple stream sockets, one for input and one for the output traffic manipulations. Over this sockets, to every packet, it's always appended its size (16bit), and Janus expects to receive data back with this precise format. The code is a portable and optimized rewrite of a first idea implemented in SniffJoke software written by Claudio Agosti. Janus overrides the actual routing table, creating a fake gateway with the aim to block packets after the kernel (on outgoing traffic) and before the kernel (on incoming traffic). Janus registers a fake ARP entry with the aim to block packets after the kernel (on outgouing traffic) and before the kernel (on incoming traffic)
found your operating system between those implemented in os-confs/
starting janus, with the correct symlink /etc/janus/current-os poiting to your selected os-confs file, contains the appropriate checks.
If you're using a package, could have provided itself with the appropriate dependencies.
root@linux# ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:24:d6:64:65:4d
inet addr:10.0.0.240 Bcast:10.0.0.255 Mask:255.255.255.0
inet6 addr: fe80::224:d6ff:fe63:664c/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:142050 errors:0 dropped:0 overruns:0 frame:0
TX packets:139827 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:70261831 (67.0 MiB) TX bytes:19672354 (18.7 MiB)
root@linux# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 10.196.136.1 0.0.0.0 UG 0 0 0 eth0
10.196.135.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
10.196.136.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
94.23.192.28 10.196.136.1 255.255.255.255 UGH 0 0 0 eth0
94.228.214.57 10.196.135.1 255.255.255.255 UGH 0 0 0 eth1
root@linux# arp -n
Address HWtype HWaddress Flags Mask Iface
10.196.136.1 ether 00:18:84:82:d6:2e CM eth0
#Example of Janus usage: root@linux# janus Janus connection diverter is starting with the following parameters: . connection is waiting in 127.0.0.1. port 30201 is serving incoming traffic, 10203 outgoing Janus is now going in foreground, use SIGTERM to stop it.
root@linux# route -n
Address HWtype HWaddress Flags Mask Iface
10.196.136.1 ether 00:24:d6:64:65:4d CM eth0
% This is a proof of concept written in Erlang that implements a simple Janus Client.
% It shows how simple is the Janus interface executing a simple packet-echo.
%
% Usage: erl -compile janus_client_poc && erl --noshell -s janus_client_poc start
%
-module(janus_client_poc).
-export([start/0]).
start() ->
JanusHost = "127.0.0.1",
JanusPort1 = 10203,
JanusPort2 = 30201,
spawn(fun() -> connect(JanusHost, JanusPort1) end),
spawn(fun() -> connect(JanusHost, JanusPort2) end).
connect(Host, Port) ->
{ok, Socket} = gen_tcp:connect(Host, Port, [{active,false}, {packet,0}]),
echo_loop(Socket).
echo_loop(Socket) ->
case gen_tcp:recv(Socket, 0) of
{ok, Data} ->
% potential packet mangling activity
io:format("Hello, World!~n"),
gen_tcp:send(Socket, Data),
echo_loop(Socket);
{error, _} ->
ok
end.
Janus binary /usr/local/sbin/janus
Janus man page /usr/local/man/man1/janus.1
Official Janus page: https://github.com/evilaliv3/janus
$ gpg --keyserver pgp.mit.edu --recv-key D9A950DE
$ gpg --fingerprint --list-keys D9A950DE
pub 1024D/D9A950DE 2009-05-10 [expires: 2014-05-09]
Key fingerprint = C1ED 5C8F DB6A 1C74 A807 5695 91EC 9BB8 D9A9 50DE
uid Giovanni Pellerano <giovanni.pellerano@evilaliv3.org>
sub 4096g/50A7F150 2009-05-10 [expires: 2014-05-09]
$ gpg --keyserver pgp.mit.edu --recv-key C6765430
$ gpg --fingerprint --list-keys C6765430
pub 1024D/C6765430 2009-08-25 [expires: 2011-08-25]
Key fingerprint = 341F 1A8C E2B4 F4F4 174D 7C21 B842 093D C676 5430
uid vecna <vecna@s0ftpj.org>
uid vecna <vecna@delirandom.net>
sub 3072g/E8157737 2009-08-25 [expires: 2011-08-25]