Day08.md

Day 8: Introduction & Basic SSH Connection

Concept:

The first step is learning how to establish a basic, password-authenticated SSH connection to a remote server. The core of Paramiko's client functionality is the SSHClient object. For security, an SSH client must verify the identity of the server it connects to. We'll use AutoAddPolicy for simplicity, which automatically trusts unknown host keys (convenient for testing, but insecure for production).

Code Example:

This script connects to a remote server and prints the connection banner.

import paramiko
import getpass # To securely ask for a password

# --- Connection Details ---
hostname = 'your_server_ip_or_hostname'
port = 22
username = 'your_username'

# Use getpass to avoid hardcoding the password
try:
    password = getpass.getpass(f"Enter password for {username}@{hostname}: ")
except Exception as error:
    print('ERROR', error)
    exit()

# --- Create SSH Client ---
client = paramiko.SSHClient()

# !! IMPORTANT !!
# This line automatically adds the server's host key.
# In a real-world application, you should verify the host key.
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())

try:
    # --- Connect to the Server ---
    print(f"Connecting to {hostname}...")
    client.connect(hostname=hostname, port=port, username=username, password=password)
    
    # If connection is successful, the server often sends a banner
    banner = client.get_transport().get_banner()
    if banner:
        print("\n--- Server Banner ---")
        print(banner)
        print("---------------------\n")
    
    print("✅ Connection successful!")

except paramiko.AuthenticationException:
    print("❌ Authentication failed. Please check your credentials.")
except paramiko.SSHException as sshException:
    print(f"❌ Unable to establish SSH connection: {sshException}")
except Exception as e:
    print(f"❌ An error occurred: {e}")
finally:
    # --- Close the Connection ---
    print("Closing connection.")
    client.close()

Day 8 Challenge: 🎯

Set up a simple SSH server using a Docker container or a virtual machine (like Vagrant with VirtualBox). Alternatively, you can use a public test server like telehack.com (user/pass not required). Modify the script above to connect to your test server.