Month: September 2018

Show NAT type and external IP

PyStun is an nice Python STUN client which will help you to detect your NAT type and your external IP address. Here now a simple tutorial for usage.

Requirements

  • min. Python 2.7.x installed
  • Python virtualenv installed

Preparation

# create project and change directory
$ mkdir -p Projects/NAT && cd Projects/NAT

# create virtualenv and activate it
$ virtualenv .env && . .env/bin/activate

# install pystun
$ pip install pystun

# check pystun version (optional)
$ pystun --version

Run pystun

# run pystun with STUN host and STUN port
$ pystun -H stun.12connect.com -P 3478
NAT Type: Restric NAT
External IP: 178.81.75.18
External Port: 54320

# run pystun with STUN host and STUN port
$ pystun -H stun4.l.google.com -P 19302
NAT Type: Full Cone
External IP: 178.81.75.18
External Port: 54320

NAT Variations

On ietf.org you will find very detailed documentation on STUN.

Wifi Monitor Mode Basics

There are several ways to enable monitor mode for Wifi interfaces. Depending to your OS, installed packages, installed drivers and the Wifi model these methods are available and/or useful. In this tutorial I will explain three different ways.

3 different ways

The first example enables the monitor mode via iwconfig. To start/stop the interface the ip command is used, but you could also use ifconfig command.

# disable interface
$ ip link set wlan0 down

# enable monitor mode
$ iwconfig wlan0 mode monitor

# check interface status (optional)
$ iwconfig wlan0 | grep -i mode | awk '{print $4}'

# enable device
$ ip link set wlan0 up

The second example enables monitor mode via airmon-ng. The explicit start or stop of the interface is not necessary here. Attention, this method will change the name of the interface.

# stop interfering processes
$ airmon-ng check kill

# enable monitor mode
$ airmon-ng start wlan0

# check interface status (optional)
$ iwconfig wlan0mon | grep -i mode | awk '{print $4}'

The third example enables monitor mode via iw. To start/stop the interface the ifconfig command is used, but you could also use ip command.

# disable interface
$ ifconfig wlan0 down

# enable monitor mode
$ iw wlan0 set monitor control

# check interface status (optional)
$ iw dev | grep -i type | awk '{print $2}'

# enable device
$ ifconfig wlan0 up

It may happen that your interface crashes during the scan. In that case, you should choose a different method. If none of the shown examples works properly, it could be due to the Network Manager. In this case, turn it off. Attention, this action is then valid for all interfaces and can disturb your internet connection.

# stop network manager
$ systemctl stop NetworkManager

Troubleshoot SELinux Centos7 Apache

On my test environment, I had an permission denied issue with a simple HTML file. Shit all permissions looking good … but wait a minute SELinux was activated and I did not want to disable it. Here is the simple solution.

Example

# check SELinux status
$ sestatus

# check SELinux security context
$ ls -lahZ /var/www/html/
...
-rw-r--r--. root root unconfined_u:object_r:user_tmp_t:s0 demo.html
-rw-r--r--. root root unconfined_u:object_r:httpd_sys_content_t:s0 index.html
...

# change the SELinux security context (use RFILE's security context)
$ chcon --reference /var/www/html/index.html /var/www/html/demo.html

Cool … the problem is solved. All pages are visible without permission issues. It also works recursively if several files are affected.

# change security context recursive
$ chcon -Rv --type=httpd_sys_content_t /var/www/html