Non-root access to a wifi adapter via ioctl in Linux app - how to grant?

 Providing non-root access to a WiFi adapter via `ioctl` in a Linux application typically involves configuring the permissions and access control of the specific device files and possibly using tools like `sudo` or capabilities. Here's a general approach to achieve this:


1. **Device File Permissions**:

   WiFi adapters are represented as device files under the `/dev` directory. The first step is to adjust the permissions of these device files to allow non-root users to access them. You can use `chmod` to change the permissions, but be cautious about security implications:


   ```bash

   sudo chmod 666 /dev/your_wifi_device

   ```


   However, changing permissions to `666` means anyone can read and write to the device, which may be a security risk. It's better to restrict permissions to specific users or groups if possible.


2. **Add Users to the Appropriate Group**:

   You can create a group for users who should have access to the WiFi device and add users to that group. Then, change the group ownership of the device file accordingly:


   ```bash

   sudo groupadd wifiusers

   sudo usermod -a -G wifiusers username

   sudo chown :wifiusers /dev/your_wifi_device

   sudo chmod 660 /dev/your_wifi_device

   ```


   This approach is more secure than changing permissions to allow all users access to the device.


3. **Setuid or Setcap** (Not Recommended):

   You can use the `setuid` or `setcap` feature to allow a specific application to access the WiFi device with root-like privileges without needing to run as the root user. However, this is generally not recommended, as it poses a security risk. If you must go this route, be very cautious and use this method as a last resort.


   Using `setuid` means that the application will run with the owner's permissions, which could be a security risk if not carefully implemented.


4. **Polkit Rules** (Preferred for Desktop Environments):

   For applications running within a graphical desktop environment (e.g., GNOME, KDE), you can use Polkit (PolicyKit) rules to define fine-grained permissions for various actions, including access to specific hardware devices. You can create custom Polkit rules that allow specific users or groups to access the WiFi device.


   Custom Polkit rules are typically placed in `/etc/polkit-1/rules.d/` or `/usr/share/polkit-1/rules.d/`. Consult your distribution's documentation for specific details on creating these rules.


   Here's a basic example of a Polkit rule:


   ```xml

   <?xml version="1.0" encoding="UTF-8"?>

   <!DOCTYPE policyconfig PUBLIC "-//freedesktop//DTD PolicyKit Configuration 1.0//EN" "http://www.freedesktop.org/standards/PolicyKit/1/policyconfig.dtd">

   <policyconfig>

     <action id="org.freedesktop.devicekit.wifi.scan">

       <description>Access WiFi device for scanning</description>

       <message>Authentication is required to access WiFi device for scanning</message>

       <defaults>

         <allow_any>no</allow_any>

         <allow_inactive>no</allow_inactive>

         <allow_active>yes</allow_active>

       </defaults>

     </action>

   </policyconfig>

   ```


   Be aware that the exact rule may vary based on your specific use case and system configuration.


5. **Additional Considerations**:

   - **Seccomp and AppArmor**: Depending on your Linux distribution, you may also need to consider Seccomp or AppArmor profiles, which restrict system calls and access to resources by applications.

   - **Kernel Modules**: Make sure the appropriate kernel modules are loaded for your WiFi adapter.


Please keep in mind that adjusting permissions and access controls should be done with caution, as it can impact system security. It's generally recommended to restrict access to hardware devices as much as possible and only grant permissions to trusted users and applications.

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