SSH

SSH Reference.txt

SSH

ifconfig --------------------------------------------------------------------- Find Address

sudo apt-get install openssh-server -------------------------------------------- Install the openssh-server package
sudo cp /etc/ssh/sshd_config /etc/ssh/sshd_config.factory-defaults ------------- Make a copy of the default SSH configura=on
                                                                                 and rename it as factory default
mkdir /home/username/.ssh ------------------------------------------------------ Created a for generated key will live
mkdir ~/.ssh ------------------------------------------------------------------- Create a directory for generated key will live
sudo chmod a-w /etc/ssh/sshd_config.factory-defaults --------------------------- modify its permissions chmod 700
chmod 700 ~/.ssh --------------------------------------------------------------- change folder permissions Method 2
700 ~/.ssh && cat >> ~/.ssh/authorized_keys" ------------------------------------ change folder permissions Method 3

Configure
sudo Vim /etc/ssh/sshd_config -------------------------------------------------- Edit configura=on file
PasswordAuthentication no ------------------------------------------------------- Disable password authentication
PermitRootLogin no  ------------------------------------------------------------- A common attack is to attempt to use root to log into a server with SSH
PermitRootLogin prohibit-password
RSAAuthentication yes
IgnoreRhosts yes  --------------------------------------------------------------- To disable rhosts:
HostbasedAuthentication no ------------------------------------------------------ SSH's host-based authentication is more secure than rhosts authentication
RhostsAuthentication no
port 22
~/.ssh/authorized_keys key loca=on
sudo service ssh restart -------------------------------------------------------- Restart ssh in order to take up changes

## Set UP ##
Step 1: Create public and private keys on server
ssh-keygen -t rsa -------------------------------------------------------------- Generate key
cat /Users/me/.ssh/id_rsa.pub -------------------------------------------------- See and or copy id_rsa.pub 

id_rsa -------------------------------------------------------------------------- The private key. DO NOT SHARE THIS FILE!
id_rsa.pub ---------------------------------------------------------------------- The associated public key. This can be shared freely without consequence.

Step 2: Copy the public key to remote-host using ssh-copy-id
ssh-copy-id -i ~/.ssh/mykey <user>@<host IP> ----------------------------------- Install it as an authorized key on the server

Step 3: Login to remote-host without entering the password
ssh <user>@<IP>

Step 4: Restart

sudo restart ssh --------------------------------------------------------------restart the SSH service.
sudo service ssh restart ------------------------------------------------------restart the SSH service if above fails.
sudo systemctl restart ssh ----------------------------------------------------restart the SSH service.



Understanding ~/.ssh/config entries

Host : Defines for which host or hosts the configuration section applies. The section ends with a new Host section or the end of the file. 
       A single * as a pattern can be used to provide global defaults for all hosts.

HostName : Specifies the real host name to log into. Numeric IP addresses are also permitted.

User : Defines the username for the SSH connection.

IdentityFile : Specifies a file from which the user’s DSA, ECDSA or DSA authentication identity is read. The default is ~/.ssh/identity for 
               protocol version 1, and ~/.ssh/id_dsa, ~/.ssh/id_ecdsa and ~/.ssh/id_rsa for protocol version 2.

ProxyCommand : Specifies the command to use to connect to the server. The command string extends to the end of the line, and is executed with 
               the user’s shell. In the command string, any occurrence of %h will be substituted by the host name to connect, %p by the port, 
               and %r by the remote user name. The command can be basically anything, and should read from its standard input and write to its 
              standard output. This directive is useful in conjunction with nc(1) and its proxy support. For example, the following directive 
              would connect via an HTTP proxy at 192.1.0.253:

ProxyCommand /usr/bin/nc -X connect -x 192.1.0.253:3128 %h %p

LocalForward : Specifies that a TCP port on the local machine be forwarded over the secure channel to the specified host and port from the remote 
               machine. The first argument must be [bind_address:]port and the second argument must be host:hostport.

Port : Specifies the port number to connect on the remote host.

Protocol : Specifies the protocol versions ssh(1) should support in order of preference. The possible values are 1 and 2.

ServerAliveInterval : Sets a timeout interval in seconds after which if no data has been received from the server, ssh(1) will send a message through 
                      the encrypted channel to request a response from the server. See blogpost “Open SSH Server connection drops out after few or N 
                      minutes of inactivity” for more information.

ServerAliveCountMax : Sets the number of server alive messages which may be sent without ssh(1) receiving any messages back from the server. If this 
                      threshold is reached while server alive messages are being sent, ssh will disconnect from the server, terminating the session.


sudo apt-get install openssh-server  ------------------------------------------  install the SSH server on your server
sudo apt-get install openssh-client  ------------------------------------------  install the SSH client on your desktop
cd ~/.ssh ---------------------------------------------------------------------  client machine
ssh-keygen -t rsa  ------------------------------------------------------------  generate SSH keys on your client machine
mkdir -p ~/.ssh/  -------------------------------------------------------------  On the server, create the folder for SSH
scp -P "ssh-port" ~/.ssh/id_dsa.pub username@serverip-address:~/.ssh ----------  client machine, copy the public key file to your server
cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys  ------------------------------  Change the filename and permissions:
chmod 700 .ssh
chmod 600 .ssh/authorized_keys
rm .ssh/id_rsa.pub
ssh -P "ssh-port" username@serverip-address ------------------------------------ Log on