Commit 2e8e4723 authored by Tomek Mrugalski's avatar Tomek Mrugalski 🛰

[#160] Running non-rooted kea described

parent e190cf5e
......@@ -516,3 +516,82 @@ code, at the "configure" step (see :ref:`configure`), enter:
.. include:: hammer.rst
Running Kea from non-root account on Linux
Both Kea DHCPv4 and DHCPv6 servers perform operations that in general require root access
privileges. In particular, DHCPv4 opens raw sockets and both DHCPv4 and DHCPv6 open UDP sockets on
privileged ports. However, with some extra system configuration, it is possible to run Kea from
non-root accounts.
First, a regular user account must be created:
.. code-block:: console
useradd admin
Then, change the binaries ownership and group to new user. Note your path may be different. Please
refer to the ``--prefix`` parameter passed to the configure script.:
.. code-block:: console
chown -R admin /opt/kea
chgrp -R admin /opt/kea
chown -R admin /var/log/kea-dhcp4.log
chgrp -R admin /var/log/kea-dhcp4.log
chown -R admin /var/log/kea-dhcp6.log
chgrp -R admin /var/log/kea-dhcp6.log
Assuming you are using systemd, you also should modify its service file
(e.g. /etc/systemd/system/kea-dhcp6.service):
.. code-block:: console
The most important step is to set capabilities of the binaries. Refer to `man capabilities` to get
more information.
.. code-block:: console
setcap 'cap_net_bind_service=+ep' /opt/kea/sbin/kea-dhcp4
setcap 'cap_net_raw=+ep' /opt/kea/sbin/kea-dhcp4
setcap 'cap_net_bind_service=+ep' /opt/kea/sbin/kea-dhcp6
After this step is complete, the admin user should be able to run Kea. Note that DHCPv4 server by
default opens raw sockets. If your network is only using relayed traffic, you can instruct Kea to
use regular UDP sockets (refer to ``dhcp-socket-type`` parameter in the
:ref:`dhcp4-interface-configuration` section) and the ``cap_net_raw`` capability can be skipped.
.. note::
An alternative approach to avoiding running Kea with root privileges assumes instructing Kea to
use non-privileged (greater than 1024) posts and redirecting traffic. This, however, will work
only for relayed traffic. This approach in general is considered experimental and not tested
enough for deployment in production environment. Use with care!
To use this approach, configure the server to listen on other non privileged port (eg: 1547
and 1548) by running the process with ``-p`` option in ``/etc/systemd/system/kea-dhcp4.service``:
.. code-block:: console
ExecStart=/opt/kea/sbin/kea-dhcp4 -d -c /etc/kea/kea-dhcp4.conf -p 2067
and ``/etc/systemd/system/kea-dhcp4.service``:
.. code-block:: console
ExecStart=/opt/kea/sbin/kea-dhcp6 -d -c /etc/kea/kea-dhcp6.conf -p 1547
and then configure port redirection with iptables and ip6tables for new ports (eg: 1547
and 1548). Make sure you replace ens4 with your specific interface name.
.. code-block:: console
iptables -t nat -A PREROUTING -i ens4 -p udp --dport 67 -j REDIRECT --to-port 2067
ip6tables -t nat -A PREROUTING -i ens4 -p udp --dport 2068 -j REDIRECT --to-port 68
ip6tables -t nat -A PREROUTING -i ens4 -p udp --dport 547 -j REDIRECT --to-port 1547
ip6tables -t nat -A PREROUTING -i ens4 -p udp --dport 1548 -j REDIRECT --to-port 548
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