Status changed to 'Confirmed' because the bug affects multiple users.
** Changed in: network-manager (Ubuntu)
Status: New => Confirmed
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https://bugs.launchpad.net/bugs/1599949
Title:
NetworkManager Sets Wrong DNS Server When OpenVPN tun0 starts if ipv6
on underlying interface in Ubuntu 16.04
Status in network-manager package in Ubuntu:
Confirmed
Bug description:
In Ubuntu 16.04 when I start an OpenVPN tunnel via the NetworkManager
GUI over an outer interface for which only IPv4 is configured, only
the DNS server that is reachable through the new tun0 interface is
configured by network manager. This is correct, no DNS leakage outside
the tunnel occurs.
However, if I start OpenVPN and use an outer interface (over which
tun0 flows) that has both IPv4 and IPv6 configured, the NetworkManager
reports the DNS server of the outer interface and the DNS server of
the tun0 interface to dnsmasq/resolvconf. This leads to DNS leakage
outside tun0 and is a security issue as DNS queries are done inside
and outside the tunnel. Here's the interesting part in syslog:
-----
Jul 7 20:02:40 wlm NetworkManager[4694]: <warn> [1467914560.9893] device
(tun0): failed to disable userspace IPv6LL address handling
Jul 7 20:02:40 wlm NetworkManager[4694]: <info> [1467914560.9897] device
(tun0): state change: ip-config -> ip-check (reason 'none') [70 80 0]
Jul 7 20:02:40 wlm NetworkManager[4694]: <info> [1467914560.9913] device
(tun0): state change: ip-check -> secondaries (reason 'none') [80 90 0]
Jul 7 20:02:40 wlm NetworkManager[4694]: <info> [1467914560.9917] device
(tun0): state change: secondaries -> activated (reason 'none') [90 100 0]
Jul 7 20:02:40 wlm NetworkManager[4694]: <info> [1467914560.9963] policy:
set 'tun0' (tun0) as default for IPv4 routing and DNS
Jul 7 20:02:41 wlm NetworkManager[4694]: <info> [1467914560.9967] dns-mgr:
Writing DNS information to /sbin/resolvconf
Jul 7 20:02:41 wlm systemd[1]: Starting Network Manager Script Dispatcher
Service...
Jul 7 20:02:41 wlm dnsmasq[16825]: setting upstream servers from DBus
Jul 7 20:02:41 wlm dnsmasq[16825]: using nameserver 10.8.0.1#53
Jul 7 20:02:41 wlm dnsmasq[16825]: using nameserver 192.168.42.1#53
Jul 7 20:02:41 wlm dbus[878]: [system] Successfully activated service
'org.freedesktop.nm_dispatcher'
Jul 7 20:02:41 wlm nm-dispatcher: req:1 'vpn-up' [tun0]: new request (1
scripts)
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Only 10.8.0.1 should be configured at this point. 192.168.42.1 should
NOT be configure (and is not if the outer interface is IPv4 only!
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