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Revision as of 16:21, 3 January 2024 by Till (talk | contribs) (→‎Detailed Description: clarify impact and required user behavior)


Set the default MAC address randomization mode for Wi-Fi networks in NetworkManager

This is a proposed Change for Fedora Linux.
This document represents a proposed Change. As part of the Changes process, proposals are publicly announced in order to receive community feedback. This proposal will only be implemented if approved by the Fedora Engineering Steering Committee.

Summary

Adopt stable-ssid as the default MAC address randomization mode for Wi-Fi networks in NetworkManager for Fedora 40, enhancing user privacy without compromising network stability.


Owner


Current status

  • Targeted release: Fedora Linux 40
  • Last updated: 2024-01-03
  • Announced
  • Discussion thread
  • FESCo issue: <will be assigned by the Wrangler>
  • Tracker bug: <will be assigned by the Wrangler>
  • Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

The change involves adding a new file, /usr/lib/NetworkManager/conf.d/22-wifi-mac-addr.conf. This file sets wifi.cloned-mac-address=”stable-ssid” as the default mode for MAC address selection in Wi-Fi connections within NetworkManager for Fedora Linux 40. The stable-ssid mode selects a different MAC address based on the network's SSID and the machine ID and is aimed at enhancing user privacy. This new default value will apply to Wi-Fi profiles in Fedora Linux 40 and later that do not override the default.

The content of the added file is: 

  [connection.22-wifi-mac-addr]
  match-device=type:wifi
  wifi.cloned-mac-address=stable-ssid
   
  [.config]
  enable=nm-version-min:1.45

For further details, please refer to man NetworkManager.conf.

With this config file, the MAC addresses for the Wi-Fi interface will usually change once which can cause problems to connect to wireless networks that restrict access based on MAC addresses and can lead to getting the connecting device to obtain a different IP address. Therefore the settings on the Wi-Fi router might need to be adjusted correspondingly. Alternatively, the profiles or the system can be changed to the previous behavior (see #Upgrade/compatibility impact).

Benefit to Fedora

This change enhances user privacy by addressing the issue of MAC address tracking method used by network operators and advertisers to gather data about users’ movements and device usage patterns. By randomizing MAC addresses, Fedora reduces the potential for this type of passive surveillance, thereby enhancing individual privacy. It aligns Fedora with privacy-focused features present in other modern operating systems. The generated MAC address under the stable-ssid mode is derived from the network’s SSID, a per-host key (from /etc/machine-id and /var/lib/NetworkManager/secret_key), and a per-interface identifier.


Scope

  • Proposal owners:

The merge request is already merged upstream.

  • Other developers: N/A
  • Policies and guidelines: N/A (not needed for this Change)
  • Trademark approval: N/A (not needed for this Change)


Upgrade/compatibility impact

With the adoption of stable-ssid as the default in Fedora 40, existing users may experience changes in their Wi-Fi connection behavior, particularly those whose network setups depend on fixed MAC addresses. It’s crucial for users to be aware that upgrading to Fedora 40 will apply this new MAC address randomization by default. Users needing to maintain consistent MAC addresses for specific networks can address this by following one of these steps:

1. Manually set wifi.cloned-mac-address to permanent for specific profiles using 

  nmcli connection modify [$PROFILE] wifi.cloned-mac-address permanent

2. Create a custom configuration file in /etc/NetworkManager/conf.d/22-wifi-mac-addr.conf, which can be empty or contain specific configurations. This will prevent the default file in /usr/lib from being loaded.

3. Create a higher priority .conf file like /etc/NetworkManager/conf.d/90-wifi-mac-addr.conf with: 

  [connection-90-wifi-mac-addr-conf]
  wifi.cloned-mac-address=permanent

For details on the order in which configuration files are loaded and their priority, refer to man NetworkManager.conf


How To Test

  • Upgrade NetworkManager to version 1.45 or newer implementing the stable-ssid mode
  • Connect to Wi-Fi network using nmcli or the GNOME network settings
  • Use ip link show (replacing [device] with your Wi-Fi device’s name) to check the MAC address assigned to the device.
  • Note the MAC address and reconnect to the same network to confirm that the MAC address remains consistent across sessions.
  • Connect to different Wi-Fi networks and observe the MAC address for each connection.
  • Ensure that the MAC address is derived from the network’s SSID.
  • Manually override the MAC address for a specific Wi-Fi profile using nmcli connection modify [profile] wifi.cloned-mac-address [your-mac-address] to set a specific MAC address
  • Reconnect to the network and use nmcli device show [device] to verify that the specified MAC address is being used.

User Experience

Users will experience an additional layer of privacy without any required action on their part. The change is transparent, with minimal impact on the day-to-day user experience. However, for those with specific network configurations reliant on static MAC addresses, this update may require manual adjustments to network profile settings. Users in such scenarios will need to be aware of the change and how to revert to a fixed MAC address if necessary, ensuring their network connectivity aligns with their requirements.

Dependencies

N/A


Contingency Plan

  • Contingency mechanism: Revert to previous MAC address handling if significant issues arise.
  • Contingency deadline: Beta freeze of Fedora 40.
  • Blocks release? No


Documentation

No documentation change is required.

Release Notes

The change will be mentioned in the Release Notes.

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