Notes

Network Services

2 min read

Need the ability to communicate with other computers over the network, connect, transfer files, analyze traffic, identify any vulnerabilities; learn how to configure such services during a penetration testing. Focus on key services essential for admins, users and pentesters.

SSH (Secure Shell)

Purpose: Secure data and command transmission.
Key Tool: OpenSSH (most common SSH server). Configuration: Edit /etc/ssh/sshd_config to adjust login methods, connection limits, and host key settings.

workstation@htb[/htb]$ sudo apt install openssh-server -y
workstation@htb[/htb]$ systemcl status ssh
 
ssh.service - OpenBSD Secure Shell server
     Active: active (running) since Sun 2023-02-12 21:15:27 GMT; 1min 22s ago
   Main PID: 7740 (sshd)
     CGroup: /system.slice/ssh.service
             └─7740 sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups

NFS (Network File System)

Purpose: Share/manage remote files as if local. Configuration File: /etc/exports

workstation@htb[/htb]$ sudo apt install nfs-kernel-server -y
workstation@htb[/htb]$ systemctl status nfs-kernel-server
 
nfs-server.service - NFS server and services
     Active: active (exited) since Sun 2023-02-12 21:35:17 GMT; 13s ago
    Process: 9234 ExecStartPre=/usr/sbin/exportfs -r (code=exited, status=0/SUCCESS)

Permission:

  • rw: read and write to shared directory
  • ro: read only to shared directory
  • no_root_squash: prevents root from being restricted
  • root_squash: root is also considered as normal user
  • async: transfer data asynchronously faster but inconsistent
  • sync: Synchronizes the transfer slower but consistent
work@htb:~$ mkdir nfs_sharing
work@htb:~$ echo '/home/cry0l1t3/nfs_sharing hostname(<choices>)' >> /etc/export 
 
work@htb:~$ mkdir ~/target_nfs
work@htb:~$ mount 10.129.12.17:/home/john/dev_scripts ~/target_nfs
work@htb:~$ tree ~/target_nfs
 
target_nfs/
├── css.css
├── html.html
├── javascript.js
├── php.php
└── xml.xml

Web Servers

Apache Purpose: Host web applications and analyze traffic. Configuration File: /etc/apache2/apache2.conf

workstation@htb[/htb]$ sudo apt install apache2 -y
workstation@htb[/htb]$ echo '''
<Directory /var/www/html>  
	Options Indexes FollowSymLinks  
	AllowOverride All  
	Require all granted  
</Directory> ''' >> /var/www/html/index.html

Python Web Server Purpose: Lightweight alternative for file transfers.

workstation@htb[/htb]$ python3 -m http.server
workstation@htb[/htb]$ python3 -m http.server --directory /path/to/files

VPN (Virtual Private Network) Purpose: Secure remote network connections via encryption.

  • Popular Tools: OpenVPN, L2TP/IPsec, PPTP, SSTP, SoftEther.
  • Usage for Penetration Testing: Enables secure remote access to internal networks.
  • Installation:
workstation@htb[/htb]$ sudo apt install openvpn -y
workstation@htb[/htb]$ sudo openvpn --config internal.ovpn

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