[ASA-202012-12] blueman: privilege escalation

[Morten Linderud]

Arch Linux Security Advisory ASA-202012-12
==========================================

Severity: High
Date    : 2020-12-09
CVE-ID  : CVE-2020-15238
Package : blueman
Type    : privilege escalation
Remote  : No
Link    : https://security.archlinux.org/AVG-1259

Summary
=======

The package blueman before version 2.1.4-1 is vulnerable to privilege
escalation.

Resolution
==========

Upgrade to 2.1.4-1.

# pacman -Syu "blueman>=2.1.4-1"

The problem has been fixed upstream in version 2.1.4.

Workaround
==========

As Polkit-1-support is enabled in Arch, it is possible to 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.

Description
===========

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.

Impact
======

A local attacker might be able to escalate privileges.

References
==========

https://bugs.archlinux.org/task/68563
https://github.com/blueman-project/blueman/security/advisories/GHSA-jpc9-mgw6-2xwx
https://bugs.launchpad.net/ubuntu/+source/blueman/+bug/1897287
https://security.archlinux.org/CVE-2020-15238
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