v2020 ← v2022dev1: Add sdk user to the sudo group to fix blueman regression

Backport of !355 (merged)

The user account user that is created on the SDK already has sudo powers. However this user account is not part of the sudo group.

With the upgrade of blueman from 2.0.8-1co1 to 2.0.8-1+deb10u1co1 this has was now causing an error dialog saying that "You might not be able to connect to the Bluetooth network via this machine":

https://github.com/blueman-project/blueman/issues/948

It seems that polkit was disabled and the update which came from debian-security to fix CVE-2020-15238 enabled it:

Blueman is a GTK+ Bluetooth Manager. In Blueman before 2.1.4, the DhcpClient method of the D-Bus interface to blueman-mechanism is prone to an argument injection vulnerability. The impact highly depends on the system configuration. If Polkit-1 is disabled and for versions lower than 2.0.6, any local user can possibly exploit this. If Polkit-1 is enabled for version 2.0.6 and later, a possible attacker needs to be allowed to use the org.blueman.dhcp.client action. That is limited to users in the wheel group in the shipped rules file that do have the privileges anyway. On systems with ISC DHCP client (dhclient), attackers can pass arguments to ip link with the interface name that can e.g. be used to bring down an interface or add an arbitrary XDP/BPF program. On systems with dhcpcd and without ISC DHCP client, attackers can even run arbitrary scripts by passing -c/path/to/script as an interface name. Patches are included in 2.1.4 and master that change the DhcpClient D-Bus method(s) to accept BlueZ network object paths instead of network interface names. A backport to 2.0(.8) is also available. As a workaround, make sure that Polkit-1-support is enabled and limit privileges for the org.blueman.dhcp.client action to users that are able to run arbitrary commands as root anyway in /usr/share/polkit-1/rules.d/blueman.rules.

With polkit now being enabled, this snippets becomes relevant:

$ sudo cat /usr/share/polkit-1/rules.d/blueman.rules
// Allow users in sudo or netdev group to use blueman feature requiring root without authentication
polkit.addRule(function(action, subject) {
    if ((action.id == "org.blueman.network.setup" ||
         action.id == "org.blueman.dhcp.client" ||
         action.id == "org.blueman.rfkill.setstate" ||
         action.id == "org.blueman.pppd.pppconnect") &&
        subject.local && subject.active &&
        (subject.isInGroup("sudo") || subject.isInGroup("netdev"))) {
        return polkit.Result.YES;
    }
});

Adding the user to the sudo group would then make blueman happy again.

Task: T7728