Tuesday, 27 February 2018

Tunna: A Set of Tools Which Will Wrap And Tunnel Any TCP Communication Over HTTP

Tunna: A Set of Tools Which Will Wrap And Tunnel Any TCP Communication Over HTTP

Tunna: A Set of Tools Which Will Wrap And Tunnel Any TCP Communication Over HTTP

It can be used to bypass network restrictions in fully firewalled environments.


TLDR: Tunnels TCP connections over HTTP

In a fully firewalled (inbound and outbound connections restricted - except the webserver port)

The webshell can be used to connect to any service on the remote host. This would be a local connection on a local port at the remote host and should be allowed by the firewall.

The webshell will read data from the service port wrap them over HTTP and send it as an HTTP response to the local proxy.

The local proxy will unwrap and write the data to it's local port where the client program would be connected.

When the local proxy receives data on the local port, it will send them over to the webshell as an HTTP Post.

The webshell will read the data from the HTTP Post and put them on the service port

and repeat Only the webserver port needs to be open (typically 80/443) The whole communication (Externally) is done over the HTTP protocol.


python proxy.py -u <remoteurl> -l <localport> [options]


--help, -h show this help message and exit

--url=URL, -u URL url of the remote webshell

--lport=LOCAL_PORT, -l LOCAL_PORT local listening port

--verbose, -v Verbose (outputs packet size)

--buffer=BUFFERSIZE, -b BUFFERSIZE* HTTP request size (some webshels have limitations on the size)

No SOCKS Options

Options are ignored if SOCKS proxy is used

--no-socks, -n Do not use Socks Proxy

--rport=REMOTE_PORT, -r REMOTE_PORT remote port of service for the webshell to connect to

--addr=REMOTE_IP, -a REMOTE_IP address for remote webshell to connect to (default =

Upstream Proxy Options

Tunnel connection through a local Proxy

--up-proxy=UPPROXY, -x UPPROXY Upstream proxy (http://proxyserver.com:3128)

--auth, -A Upstream proxy requires authentication

Advanced Options

--ping-interval=PING_DELAY, -q PING_DELAY webshprx pinging thread interval (default = 0.5)

--start-ping, -s Start the pinging thread first - some services send data first (eg. SSH)

--cookie, -C Request cookies

--authentication, -t Basic authentication

See limitations

Example usage: python proxy.py -u -l 8000 -v

# This will start a Local SOCKS Proxy Server at port 80000
# This connection will be wrapped over HTTP and unwrapped at the remote server

python proxy.py -u -l 8000 -x -A -v

# This will start a Local SOCKS Proxy Server at port 80000
# It will connect through a Local Proxy ( that requires authentication
# to the remote Tunna webshell

python proxy.py -u -l 4444 -r 3389 -b 8192 -v --no-socks

# This will initiate a connection between the webshell and Remote host RDP (3389) service
# The RDP client can connect on localhost port 4444
# This connection will be wrapped over HTTP


The ability to upload a webshell on the remote server
This is a POC code and might cause DoS of the server.
All efforts to clean up after execution or on error have been made (no promises)

Based on local tests:
* JSP buffer needs to be limited (buffer option):
4096 worked in Linux Apache Tomcat
1024 worked in XAMPP Apache Tomcat (slow)
* More than that created problems with bytes missing at the remote socket
eg: ruby proxy.rb -u -l 4444 -r 3389 -b 1024 -v

* Sockets not enabled by default php windows (IIS + PHP)

* Return cariages on webshells (outside the code):
get sent on responses / get written on local socket --> corrupt the packets

* PHP webshell for windows: the loop function DoS'es the remote socket:
sleep function added -> works but a bit slow
* PHP webshell needs new line characters removed at the end of the file (after "?>")
as these will get send in every response and confuse Tunna



conn.jsp Tested on Apache Tomcat (windows + linux)
conn.aspx Tested on IIS 6+8 (windows server 2003/2012)
conn.php Tested on LAMP + XAMPP + IIS (windows + linux)


webserver.py Tested with Python 2.6.5


proxy.py Tested with Python 2.6.5

Technical Details

Architecture descisions
Data is sent raw in the HTTP Post Body (no post variable)

Instructions / configuration is sent to the webshell as URL parameters (HTTP Get)
Data is sent in the HTTP body (HTTP Post)

Websockets not used: Not supported by default by most of webservers
Asyncronous HTTP responses not really possible
  • Proxy queries the server constantly (default 0.5 seconds)


1st packet initiates a session with the webshell - gets a cookie back eg: http://webserver/conn.ext?proxy

2nd packet sends connection configuration options to the webshell eg: http://webserver/conn.ext?proxy&port=4444&ip=

IP and port for the webshell to connect to
This is a threaded request:
  • In php this request will go into an infinate loop 
  • to keep the webshell socket connection alive
  • In other webshells [OK] is received back


A local socket is going to get created where the client program is going to connect to Once the client is connected the pinging thread is initiated and execution starts. Any data on the socket (from the client) get read and get sent as a HTTP Post request Any data on the webshell socket get sent as a response to the POST request.


Because HTTP responses cannot be asyncronous. This thread will do HTTP Get requests on the webshell based on an interval (default 0.5 sec) If the webshell has data to send, it will (also) send it as a reply to this request Otherwise it sends an empty response.

In general: Data from the local proxy get send with HTTP Post There are Get requests every 0.5 sec to query the webshell for data If there is data on the webshell side get send over as a response to one of these requests.


The webshell connects to a socket on the local or a remote host. Any data written on the socket get sent back to the proxy as a reply to a request (POST/GET) Any data received with a post get written to the socket.

All requests need to have the URL parameter "proxy" set to be handled by the webshell (http://webserver/conn.ext?proxy)

Kills all threads and closes local socket Sends proxy&close to webshell: Kills remote threads and closes socket

The SOCKS support is an addon module for Tunna. Locally is a seperate thread that handles the connection requests and traffic adds a header that specifies the port and the size of the packet and forwards it to Tunna. Tunna sends it over to the remote webserver, removes the HTTP headers and forwards the packet to the remote SOCKS proxy.

The remote SOCKS proxy initiates the connection and mapps the received port to the local port. If the remote SOCKS proxy receives data from the service, it looks at the mapping table and finds the port it needs to respond to, adds the port as a header so the local SOCKS proxy will know where to forward the data. Any traffic from the received port will be forwarded to the local port and vice versa.

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