OpenWrt based Wi-Fi MAC scanner

You will be able in 3 minutes:

Setup your own Wi-Fi MAC addresses scanner with OpenWrt.
Setup FTP upload server which will collect all data from all routers.

Parsing final data not covered by this article.
You can do it with a programming language you prefer.
You can use PuTTY to connect to your router with SSH protocol.

We're using OpenWrt version 19.07.2 but fell free to use any other OpenWrt version.

Please note, you already should have Internet configured on router to proceed.

Please note, you have to change upload.maccollector.com to your own hostname with FTP server on it.

Installing OpenWrt on Wi-Fi router

Not covering here.

Installing dependent software packages on OpenWrt

Invoke following command one-by-one in router's console:

opkg update
opkg install procps-ng-pkill
opkg install wireless-tools
opkg install aircrack-ng
opkg install lftp
opkg install screen
opkg install nano
#following is optional (useful for debug):
opkg install diffutils
opkg install tcpdump

Creating MAC scanner script

We create it in on-boot place so script will be invoked automatically after each reboot.
Do not foter to change upload.maccollector.com to your host before pasting it to the router's console.

cat <<'EOF'> /etc/rc.d/S99wifi
#!/bin/sh

export PATH="/usr/sbin/:/sbin/:$PATH"
set -xv


#########################
cat <<'EOFAA'> /root/wifi.sh
#!/bin/sh

export PATH="/usr/sbin/:/sbin/:$PATH"
set -xv


ifconfig wlan0 down
#iwconfig obsolete, see https://openwrt.org/docs/guide-user/network/wifi/wireless-tool/wireless.utilities
iwconfig wlan0 mode monitor
ifconfig wlan0 up

MYHOST=$(grep 'option hostname' /etc/config/system|awk '{print $3}'| tr -d "'");

pkill airodump-ng
rm -fv /tmp/outfile-*


while [ ! -e /tmp/stop ]; do
date
airodump-ng wlan0 -w /tmp/outfile --background 1 --output-format csv & PID=$!
sleep 300;
kill $PID;
pkill airodump-ng
sleep 1;

lftp -u ftp:ftp -e "cd upload; put /tmp/outfile-01.csv -o outfile_${MYHOST}_`date '+%Y-%m-%d-%H-%M-%S'`.csv; bye;" upload.maccollector.com ;
cat /dev/null > /tmp/outfile-01.csv ;
rm -fv /tmp/outfile-*

done

EOFAA
#########################

chmod 755 /root/wifi.sh

screen -S wifi -d -m /bin/sh /root/wifi.sh

EOF

chmod 755 /etc/rc.d/S99wifi

Configuring interfaces file

Edit /etc/config/wireless with: vi or nano.
as described below:

vi /etc/config/wireless

Found block starting with following line:
config wifi-device 'radio0'

and comment out (append # before it) following line
(should be last line in block), change it form:
        option disabled '1'
to:
#        option disabled '1'

Found block starting with following line:
config wifi-iface 'default_radio0'

and append following line
(should be appended as a last line in block):
        option disabled '1'

Following block should be added to the bottom of file:
config wifi-iface 'wifinet0'
        option device 'radio0'
        option network 'lan'
        option mode 'monitor'
        option hidden '1'

Also make few blank lines after this block.

Now comprehensive example of how things will looks like:

root@OpenWrt:~# cat /etc/config/wireless

config wifi-device 'radio0'
        option type 'mac80211'
        option channel '11'
        option hwmode '11g'
        #THIS SHOULD BE KEEP AS ORIGINAL HIST LINE MAY VARY FOR YOU: option path 'platform/ar934x_wmac'
        option htmode 'HT20'
#COMMENT THIS OUT:
#        option disabled '1'

#this block will be ther already:
config wifi-iface 'default_radio0'
        option device 'radio0'
        option network 'lan'
        option mode 'ap'
        option ssid 'OpenWrt'
        option encryption 'none'
#APPEND IT HERE:
        option disabled '1'


#This block should be added to the bottom:
config wifi-iface 'wifinet0'
        option device 'radio0'
        option network 'lan'
        option mode 'monitor'
        option hidden '1'

root@OpenWrt:~#

Post-setup steps

Reboot the router and setup Linux FTP server to receiving router's data.

reboot

Setup collecting FTP server

We will use vsftpd as the FTP sever.
In this example we are using vsftpd version 3.0.2.

cp -aiv /etc/vsftpd.conf /etc/vsftpd.conf-`\date -I`
cat <<'EOF'> /etc/vsftpd.conf

listen=NO
listen_ipv6=YES
use_localtime=YES
#secure_chroot_dir=/var/run/vsftpd/empty
secure_chroot_dir=/srv/ftp
#secure_chroot_dir=/srv
rsa_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
rsa_private_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
ssl_enable=NO


pam_service_name=vsftpd
ftp_username=ftp

anonymous_enable=YES
local_enable=YES
write_enable=YES
local_umask=022

anon_umask=000

anon_upload_enable=YES
anon_mkdir_write_enable=YES
dirmessage_enable=YES
xferlog_enable=YES
connect_from_port_20=YES
#very short of data
#xferlog_std_format=YES
chroot_local_user=NO
chroot_list_enable=NO

#listen=YES
#listen_ipv6=YES


pasv_enable=YES
pasv_min_port=49152
pasv_max_port=65535

#pam_service_name=vsftpd

userlist_enable=YES
tcp_wrappers=YES


anon_other_write_enable=YES
anon_root=/srv/ftp
#anon_root=/srv
#anon_root=/
no_anon_password=YES
hide_ids=YES


#ls: Login failed: 500 OOPS: vsftpd: refusing to run with writable root inside chroot()
allow_writeable_chroot=YES

max_clients=100500

userlist_file=/etc/vsftpd/allowed_list

#google: vsftpd user ftp 530 Permission denied
#https://www.thegeekdiary.com/error-530-permission-denied-when-user-logs-in-to-vsftpd-server-via-ftp/
userlist_deny=NO

xferlog_enable=YES
log_ftp_protocol=YES
#syslog_enable=YES
xferlog_file=/var/log/vsftpd.log 


download_enable=NO
dirlist_enable=NO

EOF

cat <<'EOF'> /etc/vsftpd/allowed_list 
ftp

EOF

chown root:root /etc/vsftpd/
chmod 755 /etc/vsftpd/

chown root:root /etc/vsftpd/allowed_list
chmod 644 /etc/vsftpd/allowed_list

#chown root:adm /var/log/vsftpd.log
chmod 777 /var/log/vsftpd.log

chown root:root /srv/ /srv/ftp/
chmod 755 /srv/ /srv/ftp/

chown ftp:ftp /srv/ftp/upload/
chmod 755 /srv/ftp/upload/

You can change router's name

To be able to differentiate one router from other routers you can set unique name to each of it:

vi /etc/config/system
reboot

All done

Now you're all set.
Just reload vsftpd.