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111 lines
6.0 KiB
Markdown
111 lines
6.0 KiB
Markdown
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Anonymizing your MAC Address
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============================
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Although it is not the only metadata broadcast by network hardware, changing the default [MAC Address](https://en.wikipedia.org/wiki/MAC_address) of your hardware could be [an important step in protecting privacy](https://tails.boum.org/contribute/design/MAC_address/#index1h1).
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Qubes OS 4.1 and higher already anonymize all Wifi MAC addresses [by default](https://github.com/QubesOS/qubes-core-agent-linux/blob/master/network/nm-31-randomize-mac.conf) - they change during every Wifi session.
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So there is **no need** to apply any of the below instructions if you're only interested in Wifi connections. Users requiring Ethernet MAC address anonymization may want to read on.
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## Randomize a single connection
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Right click on the Network Manager icon of your NetVM in the tray and click 'Edit Connections..'.
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Select the connection to randomize and click Edit.
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Select the Cloned MAC Address drop down and set to Random or Stable.
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Stable will generate a random address that persists until reboot, while Random will generate an address each time a link goes up.
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Save the change and reconnect the connection (click on Network Manager tray icon and click disconnect under the connection, it should automatically reconnect).
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## Randomize all Ethernet and Wifi connections
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These steps should be done inside a template to be used to create a NetVM as it relies on creating a config file that would otherwise be deleted after a reboot due to the nature of AppVMs.
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Write the settings to a new file in the `/etc/NetworkManager/conf.d/` directory, such as `00-macrandomize.conf`.
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The following example enables Wifi and Ethernet MAC address randomization while scanning (not connected), and uses a randomly generated but persistent MAC address for each individual Wifi and Ethernet connection profile.
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~~~
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[device]
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wifi.scan-rand-mac-address=yes
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[connection]
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wifi.cloned-mac-address=stable
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ethernet.cloned-mac-address=stable
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connection.stable-id=${CONNECTION}/${BOOT}
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#use random IPv6 addresses per session / don't leak MAC via IPv6 (cf. RFC 4941):
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ipv6.ip6-privacy=2
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~~~
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* `stable` in combination with `${CONNECTION}/${BOOT}` generates a random address that persists until reboot.
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* `random` generates a random address each time a link goes up.
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To see all the available configuration options, refer to the man page: `man nm-settings`
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Next, create a new NetVM using the edited template and assign network devices to it.
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Finally, shutdown all VMs and change the settings of sys-firewall, etc. to use the new NetVM.
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You can check the MAC address currently in use by looking at the status pages of your router device(s), or inside the NetVM with the command `sudo ip link show`.
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## Anonymize your hostname
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DHCP requests _may_ also leak your hostname to your LAN. Since your hostname is usually `sys-net`, other network users can easily spot that you're using Qubes OS.
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Unfortunately `NetworkManager` currently doesn't provide an option to disable that leak globally ([Gnome Bug 768076](https://bugzilla.gnome.org/show_bug.cgi?id=768076)). However the below alternatives exist.
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### Prevent hostname sending
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`NetworkManager` can be configured to use `dhclient` for DHCP requests. `dhclient` has options to prevent the hostname from being sent. To do that, add a file to your `sys-net` template (usually the Fedora or Debian base template) named e.g. `/etc/NetworkManager/conf.d/dhclient.conf` with the following content:
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```
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[main]
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dhcp=dhclient
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```
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Afterwards edit `/etc/dhcp/dhclient.conf` and remove or comment out the line starting with `send host-name`. If the file does not exist, you may be fine already.
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In any case it makes sense to double check your results on e.g. your home router, `wireshark` or `tcpdump`.
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If you want to decide per connection, `NetworkManager` also provides an option to not send the hostname:
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Edit the saved connection files at `/rw/config/NM-system-connections/*.nmconnection` and add the `dhcp-send-hostname=false` line to both the `[ipv4]` and the `[ipv6]` section.
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### Randomize the hostname
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Alternatively you may use the following code to assign a random hostname to a VM during each of its startup. Please follow the instructions mentioned in the beginning to properly install it.
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```.bash
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#!/bin/bash
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set -e -o pipefail
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#
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# Set a random hostname for a VM session.
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#
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# Instructions:
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# 1. This file must be placed and made executable (owner: root) inside the template VM of your network VM such that it will be run before your hostname is sent over a network.
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# In a Fedora template, use `/etc/NetworkManager/dispatcher.d/pre-up.d/00_hostname`.
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# In a Debian template, use `/etc/network/if-pre-up.d/00_hostname`.
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# 2. Execute `sudo touch /etc/hosts.lock` inside the template VM of your network VM.
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# 3. Execute inside your network VM:
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# `sudo bash -c 'mkdir -p /rw/config/protected-files.d/ && echo -e "/etc/hosts\n/etc/hostname" > /rw/config/protected-files.d/protect_hostname.txt'`
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#NOTE: mv is atomic on most systems
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if [ -f "/rw/config/protected-files.d/protect_hostname.txt" ] && rand="$RANDOM" && mv "/etc/hosts.lock" "/etc/hosts.lock.$rand" ; then
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name="PC-$rand"
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echo "$name" > /etc/hostname
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hostname "$name"
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#NOTE: NetworkManager may set it again after us based on DHCP or /etc/hostname, cf. `man NetworkManager.conf` @hostname-mode
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#from /usr/lib/qubes/init/qubes-early-vm-config.sh
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if [ -e /etc/debian_version ]; then
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ipv4_localhost_re="127\.0\.1\.1"
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else
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ipv4_localhost_re="127\.0\.0\.1"
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fi
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sed -i "s/^\($ipv4_localhost_re\(\s.*\)*\s\).*$/\1${name}/" /etc/hosts
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sed -i "s/^\(::1\(\s.*\)*\s\).*$/\1${name}/" /etc/hosts
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fi
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exit 0
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```
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Assuming that you're using `sys-net` as your network VM, your `sys-net` hostname should now be `PC-[number]` with a different `[number]` each time your `sys-net` is started.
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Please note that the above script should _not_ be added to [/rw/config/rc.local](https://www.qubes-os.org/doc/config-files/)) as that is executed only _after_ the network fully started.
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