SSH Cheatsheet

SSHD Commands (Windows)

Command	Description
Start-Service sshd	Starting SSH server
Stop-Service sshd	Stopping SSH server
Restart-Service sshd	Restarting SSH server
Get-Service sshd	Retrieving status of SSH server

info

SSH on Windows logs events to the Windows Event Log. You can use the Event Viewer GUI (eventvwr.msc) or PowerShell commands to view these logs. Typically, you'd be interested in the 'Operational' logs under 'Applications and Services Logs -> OpenSSH'.

SSH Commands (Unix)

Command	Description
ssh username@remost_host	Connect to remote system
scp /path/to/source_file username@remote_host:/path/to/destination	Copy files to a remote system
ssh-keygen	Generate ssh key
ssh-copy-id user@remote_host	Copy public key to server
ssh-add /path/to/private_key	Add private key to SSH agent
eval $(ssh-agent -s)	Start the agent
ssh-add /path/to/private_key	Add keys to the agent
ssh -L local_port:localhost:remote_port user@remote_server	Local port forwarding
ssh -R remote_port:localhost:local_port user@remote_server	Remote port forwarding
sudo systemctl restart sshd	Restart ssh server

Some useful ssh flags

Flag	Description
p	Port
v	Verbose
vvv	Max verbose level

SSH Client

Role: Initiates the SSH communication. Often a user's computer.

• Responsibilities:
  • Establishing a connection to the SSH server.
  • Authenticating itself to the server.
  • Running commands on the server or forwarding traffic.
  • Common Tools/Implementations: ssh (OpenSSH), PuTTY.

SSH Server

Role: Listens for incoming SSH connections and provides services to SSH clients.

• Responsibilities:
  • Authenticating the client.
  • Running commands or services requested by the client.
  • Providing a secure encrypted tunnel for data transfer.
• Common Tools/Implementations: sshd (OpenSSH server)

SSH-Agent

Role: Acts as a key manager for SSH. Keeps private keys loaded into memory for use without requiring the passphrase every time.

• Responsibilities:
  • Safely holding private keys in memory.
  • Using the in-memory keys to authenticate on behalf of the client without exposing the actual key or repeatedly asking for the passphrase.

SSH Key Pair

Role: Consists of a private key and a public key, used for public-key cryptography.

• Responsibilities:
  • Private Key: Must be kept secret. It is used to prove one's identity.
  • Public Key: Can be shared and added to the authorized_keys file on SSH servers to allow for password-less authentication.

SSH Config File

Role: Stores configurations for SSH client-side connections, making it easier to manage multiple SSH connections.

• Responsibilities:
  • Define host-specific configurations (aliases, user names, ports, identity files).
• Location:
  • User-specific: ~/.ssh/config
  • System-wide: /etc/ssh/ssh_config

SSH Tunneling (Port Forwarding)

Role: Securely forward traffic from one network port to another.

• Types:
  • Local Port Forwarding: Forward a local port to a port on the remote server.
  • Remote Port Forwarding: Forward a port from the remote server to a port on the local client or another server.

SSH Daemon Config File

Role: Configuration file for the SSH server (sshd).

• Responsibilities:
  • Define server-specific configurations (port, allowed users, authentication methods).
• Location: /etc/ssh/sshd_config