In Ubuntu 16.04, randomize WiFi MAC addresses with a daily rotation - /etc/NetworkManager/dispatcher.d/pre-up.d/randomize-mac-addresses.sh

randomize-mac-addresses.sh

#!/bin/sh

# /etc/NetworkManager/dispatcher.d/pre-up.d/randomize-mac-addresses.sh

# INSTALL
#
# > curl -L 'https://gist.github.com/paulfurley/46e0547ce5c5ea7eabeaef50dbacef3f/raw/56ee5dd5f40dec93b8f7438cbdeda5475ea3b5d2/randomize-mac-addresses.sh' |sudo tee /etc/NetworkManager/dispatcher.d/pre-up.d/randomize-mac-addresses.sh
# > sudo chmod +x /etc/NetworkManager/dispatcher.d/pre-up.d/randomize-mac-addresses.sh

# Configure every saved WiFi connection in NetworkManager with a spoofed MAC
# address, seeded from the UUID of the connection and the date eg:
# 'c31bbcc4-d6ad-11e7-9a5a-e7e1491a7e20-2017-11-20'

# This makes your MAC impossible(?) to track across WiFi providers, and
# for one provider to track across days.

# For craptive portals that authenticate based on MAC, you might want to
# automate logging in :)

# Note that NetworkManager >= 1.4.1 (Ubuntu 17.04+) can do something similar
# automatically.

# See https://www.paulfurley.com/randomize-your-wifi-mac-address-on-ubuntu-1604-xenial/


export PATH=$PATH:/usr/bin:/bin

LOG_FILE=/var/log/randomize-mac-addresses

echo "$(date): $*" > ${LOG_FILE}

WIFI_UUIDS=$(nmcli --fields type,uuid connection show |grep 802-11-wireless |cut '-d ' -f3)

for UUID in ${WIFI_UUIDS}
do
    UUID_DAILY_HASH=$(echo "${UUID}-$(date +%F)" | md5sum)

    RANDOM_MAC="02:$(echo -n ${UUID_DAILY_HASH} | sed 's/^\(..\)\(..\)\(..\)\(..\)\(..\).*$/\1:\2:\3:\4:\5/')"

    CMD="nmcli connection modify ${UUID} wifi.cloned-mac-address ${RANDOM_MAC}"

    echo "$CMD" >> ${LOG_FILE}
    $CMD &
done

wait

Thoughts on being able to exclude certain networks, based on UUID? For example, I prefer keeping the same MAC for both my home and work wifi.

The approach I took was to change the UUID of all these "excluded networks" to have the same leading 8 characters. This way the UUIDs are all still different but I can exclude any network by simply changing the UUID in /etc/NetworkManager/system-connections/<network_name> to begin with these 8 characters.

As an example, here is the modified code, excluding comments and blank lines:

#!/usr/bin/env bash
export PATH=$PATH:/usr/bin:/bin
LOG_FILE=/var/log/randomize-mac-addresses
echo "$(date): $*" > ${LOG_FILE}
WIFI_UUIDS=$(nmcli --fields type,uuid connection show |grep 802-11-wireless |cut '-d ' -f3)
EXCLUDE_UUID="exclude1"
for UUID in ${WIFI_UUIDS}
do
  if [[ "${UUID%%-*}" != "${EXCLUDE_UUID}" ]]; then
    UUID_DAILY_HASH=$(echo "${UUID}-$(date +%F)" | md5sum)
    RANDOM_MAC="02:$(echo -n ${UUID_DAILY_HASH} | sed 's/^\(..\)\(..\)\(..\)\(..\)\(..\).*$/\1:\2:\3:\4:\5/')"
    CMD="nmcli connection modify ${UUID} wifi.cloned-mac-address ${RANDOM_MAC}"
    echo "$CMD" >> ${LOG_FILE}
    $CMD &
  fi
done
wait

An example of a UUID that would keep its default MAC address could be:

exclude1-c816-43f3-802e-9916c0ea9c7c
(Naturally, "exclude1" can be any 8 characters you prefer....)

There are probably better ways to do this but I'm curious what others think of the underlying idea. Thanks!

This might be a related post, for the NetworkManager at least: https://blogs.gnome.org/thaller/tag/randomize-mac-address/, https://blogs.gnome.org/thaller/2016/08/26/mac-address-spoofing-in-networkmanager-1-4-0/

and

https://fedoramagazine.org/randomize-mac-address-nm/

Is it possible to also change the mac address with this script every few hours? How to change the script to do that?