updated readme.md to include ssh server configuration steps.

payloads/library/remote-access/SSH-remote-access/readme.md

@@ -29,5 +29,85 @@ is that this tool is susceptible to detection via NIDS. Multiple outbound connec
 utilization raises suspicion of potential attack, however this is only a concern for more sophisticated 
 targets.
 
+---
 
-Use at your own risk. Don't do bad things.
+# SSH Server Configuration
+
+---
+
+This payload requires an SSH server be operational somewhere on the internet. Typically, a password
+is required to acquire shell access to these servers. This is a pain if you're trying to do everything
+automatically, so openssh allows for cryptographic pubkey authentication. More on this here: 
+https://www.redhat.com/sysadmin/key-based-authentication-ssh
+
+Firstly, for security reasons you may want to create a user account specifically for this payload.
+The reasoning is if the squirrel is lost or stolen someone has a key to your server, to mitigate this
+threat, if the squirrel is lost in a contested environment, deleting the user will block access.
+
+On most linux systems, the command is either 'useradd' or 'adduser', but this is distro specific.
+After you create the user and are prompted with the new user password, bear in mind to save it because
+you will need it during the pubkey installation process.
+
+    useradd squirrel
+
+Password-less authentication to a specific user account can be obtained by first enabling this in 
+the openssh configuration file. This file is most commonly found in /etc/ssh/sshd_config and changing the line
+'PubkeyAuthentication no' to 'PubkeyAuthentication yes'. Or, if your version does not have this,
+you can append this line near the top of the configuration file under the authentication category, like so:
+
+    # Authentication:
+
+    #LoginGraceTime 2m
+    #PermitRootLogin prohibit-password
+    #StrictModes yes
+    #MaxAuthTries 6
+    #MaxSessions 10
+    
+    PubkeyAuthentication yes
+    
+    # Expect .ssh/authorized_keys2 to be disregarded by default in future.
+    AuthorizedKeysFile      .ssh/authorized_keys .ssh/authorized_keys2
+    
+Also ensure that your AuthorizedKeysFile is present in your new users home directory.
+
+
+Secondly, on an SSH client, you will need to generate the key. For the sake of demonstration,
+we will use RSA 2048-bit keys, but you can use any of the following, such as dsa, ecdsa, ed25519 and rsa.
+
+Keep in mind that the squirrel is a tiny computer and may have trouble with higher-bit symmetrical keys
+like RSA 4096. If you are noticing performance problems, ecdsa and ed25519 are 'as secure' as RSA but require
+less intensive computations to encrypt and decrypt data. Choose your poison.
+
+here's the command to generate a key and place it in the current working directory. When you create it,
+it's best if you don't leave a password since this file will need to be readable without your input.
+so when prompted for a password just press 'enter' in the terminal. Note that this will create two files.
+First, the private key, then the pubkey.
+
+    ssh-keygen -t rsa -b 4096 -f id_rsa
+
+After we generate the SSH key, we need to install it on our remote SSH server. We can do this by entering the following
+into a terminal in the same directory. This will prompt the user for the password.
+
+    ssh-copy-id -i id_rsa squirrel@<ssh_server_ip>
+
+To test the connection, you can enter this into the terminal:
+    
+    ssh -i id_rsa squirrel@<ssh_server_ip>
+
+After confirming that the key-based authentication works, now it's time to configure the squirrel.
+In arming mode, secure copy the key to the /root/.ssh/ directory in the squirrel by running:
+
+    scp id_rsa root@172.16.32.1:/root/.ssh/id_rsa
+
+You will be prompted for a password and then the file will be uploaded.
+
+Then, you need to connect to the ssh server at least once so the squirrel adds this server to the list
+of known_hosts. More on this on the ssh man page. While in the squirrel, execute this:
+
+    ssh -i /root/.ssh/id_rsa squirrel@<ssh_server_ip>
+
+you will be prompted whether or not to add the host signature to known hosts, enter 'y'. Then,
+configure the payload to use your ssh user and IP address, then the payload should make the squirrels
+ssh server available at 127.0.0.1 on port 2222 on the ssh server.
+
+Goes without saying, but use at your own risk. Don't do bad things.