.. Open Infrastructure: service-tools

.. Copyright (C) 2014-2025 Daniel Baumann <daniel.baumann@open-infrastructure.net>
..
.. SPDX-License-Identifier: GPL-3.0+
..
.. This program is free software: you can redistribute it and/or modify
.. it under the terms of the GNU General Public License as published by
.. the Free Software Foundation, either version 3 of the License, or
.. (at your option) any later version.
..
.. This program is distributed in the hope that it will be useful,
.. but WITHOUT ANY WARRANTY; without even the implied warranty of
.. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.. GNU General Public License for more details.
..
.. You should have received a copy of the GNU General Public License
.. along with this program.  If not, see <https://www.gnu.org/licenses/>.

===================
dehydrated-nsupdate
===================

---------------------------------------
dehydrated hook for dns-01 verification
---------------------------------------

:manual section: 1
:manual group: Open Infrastructure

Synopsis
========

| **dehydrated-nsupdate**

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

**dehydrated** is a client for ACME-based Certificate Authorities, such as LetsEncrypt. It can be used to request and obtain TLS certificates from an ACME-based certificate authority.

The **dehydrated-nsupdate** hook implements the dns-01 verification. It is typically run together with **dehydrated-hook** as:

|
| /etc/dehydrated/hook.d/deploy_challenge.nsupdate
| /etc/dehydrated/hook.d/clean_challenge.nsupdate

Features
========

**dehydrated-nsupdate** has the following features:

Automatic nameserver detection (IPv4 and IPv6)
----------------------------------------------

dehydrated-nsupdate automatically finds and updates all authoritative nameservers for a given record by looking up the records in the DNS by itself, supporting IPv6-only, IPv4-only, and dual-stacked environments.

Proper CNAME support
--------------------

dehydrated-nsupdate follows CNAMEs delegating the TXT record update to another zone.

Handling nameserver subzone shortcuts
-------------------------------------

dehydrated-nsupdate correctly handles authoritative nameserver answers that (wrongly) give shortcut answers for their own zones when using multiple authoritative subzones on the same nameservers.

TSIG support
------------

dehydrated-nsupdate uses TSIG, if provided, to authenticate itself to the nameserver. Additionally to a global TSIG to be used for all record updates, separate TSIGs can individually be specified per record, per zone, and per nameserver.

Proper removal of TXT records
-----------------------------

dehydrated-nsupdate removes records after succesfull verification.

bind9-dnsutils and knot-dnsutils support
----------------------------------------

dehydrated-nsupdate works with both nsupdate (bind9) and knsupdate (knot).

IDN handling
------------

dehydrated-nsupdate works with IDN domains by not expanding the punycode to update the correct records.

Usage
=====

dehydrated-hook(1) is a prerequisite for dehydrated-nsupdate.

Installation
------------

| sudo echo CHALLENGETYPE="dns-01" > /etc/dehydrated/conf.d/zz-challengetype.sh
| sudo ln -s /usr/bin/dehydrated-nsupdate /etc/dehydrated/hook.d/deploy_challenge.nsupdate
| sudo ln -s /usr/bin/dehydrated-nsupdate /etc/dehydrated/hook.d/clean_challenge.nsupdate

Removal
-------

| sudo rm -f /etc/dehydrated/conf.d/zz-challengetype.sh
| sudo rm -f /etc/dehydrated/hook.d/deploy_challenge.nsupdate
| sudo rm -f /etc/dehydrated/hook.d/clean_challenge.nsupdate

Configuration
=============

Depending on the nameserver requirements, dehydrated-nsupdate can send record updates either unauthenticated or using a TSIG (recommended).

A TSIG file consists of one single line containing the key (nsupdate/knsupdate do not allow comments), e.g.:

|
| hmac-sha512:example:/LXPy6U8HAWA+QmvulZWm0owsQgNf8qJ5MNLTvirzvVtDb+PzLKoBmVHjnL6TUffkvRYa7Do448dSIrAuJ1G/A==

Instead of using a global TSIG for all record update, specific TSIGs can be used individually per record, zone, and nameserver.

The lookup hierarchy is the following (first match wins):

|
| /etc/dehydrated/tsig/${record}.key
| /etc/dehydrated/tsig/${zone}.key
| /etc/dehydrated/tsig/${nameserver}.key
| /etc/dehydrated/tsig.key
|
| TSIG_KEYFILE variable in /etc/default/dehydrated-nsupdate/*
| TSIG_KEYFILE variable in /etc/default/dehydrated-nsupdate

In order to explicitly not use a TSIG for a specific record, zone, or nameserver, an empty keyfile or a keyfile with only comments can be used, e.g.:

|
| echo "# disabled" > /etc/dehydrated/tsig/ns1.example.org.key

Files
=====

The following files are used:

/etc/dehydrated/tsig.key:
  default location for global TSIG key to be used.

/etc/dehydrated/tsig/${record}.key, /etc/dehydrated/tsig/${zone}.key, /etc/dehydrated/tsig/${nameserver}.key:
  default locations for specific TSIG keys to be used individually per record, zone, or nameserver.

/etc/default/dehydrated-nsupdate, /etc/default/dehydrated-nsupdate.d/\*:
  configuration file, currently only used for TSIG_KEYFILE variable pointing to the location of the global TSIG key to be used (default: /etc/dehydrated/tsig.key).

See also
========

| dehydrated(1),
| dehydrated-cron(1),
| dehydrated-hook(1).

Homepage
========

More information about service-tools and the Open Infrastructure project can be found on the homepage (https://open-infrastructure.net).

Contact
=======

Bug reports, feature requests, help, patches, support and everything else are welcome on the Open Infrastructure Software Mailing List <software@lists.open-infrastructure.net>.

Debian specific bugs can also be reported in the Debian Bug Tracking System (https://bugs.debian.org).

Authors
=======

service-tools were written by Daniel Baumann <daniel.baumann@open-infrastructure.net> and others.
