Ubuntu Manpage: /etc/dkim-rotate/instance.zone - dkim-rotate configuration file

NAME

       /etc/dkim-rotate/instance.zone - dkim-rotate configuration file

INTRODUCTION

The config file for each instance is /etc/dkim-rotate/instance.zone for any instance.
(When scanning for instances, only ones matching [a-z][-_0-9a-z]* are considered.)

Conventionally, the usual default instance is /etc/dkim-rotate/dkim.conf.

Each configuration file is, broadly speaking, in DNS zonefile syntax.

The config file should contain a SOA, suitable NS records, and any other records thought
desirable.

The string ;!SERIAL must appear, immediately after some digits. It should appear once, in
the SOA. dkim-rotate will replace the digits with a suitable serial number. The config
file value is also used as the starting point for a new instance.

dkim-rotate will make a DNS zone out of this file, adding an DKIM TXT RR for each
selector. (Directly in the zone, i.e., the generated zonefile will contain for example a
TXT ...).

The zonefile’s prevailing TTL applies to the generated RRS, and can therefore be adjusted
using the nameserver’s $TTL feature.

The config file should not normally contain MX records, because the dkim-rotate-managed
zonefile should usually be a different zone to your principal mail domain zone(s). (See
the Principles of Operation in dkim-rotate(7).)

$ORIGIN may be used to cause the dkim-rotate-generated RRs to appear as sub-labels of a
sub-domain.

The config file also contains some special directives, on lines starting with !, which
contain the configuration for dkim-rotate. These will be stripped out so that they don’t
appear in the output zonefile gneerated by dkim-rotate.

The parameters for an existing instance may safely be adjusted. (Although, reducing
max_selector does not take full effect immediately.)

IMPORTANT DIRECTIVES

       ! pub_url url-string
              URL at which our published private keys are available.  This should be a public URL
              at which the directory instance_var_dir/pub/ is accessible.

              This is used:

              • For a n= field in the generated DKIM TXT RRs.

              • For the header_note and various url outputs in the MTA config.

              • To check that a key we are trying to reveal is actually revealed.

              A  warning  will  be  generated  if  a  supposedly-revealed  key is found not to be
              accessible.

              - can be used to indicate “none”.  This will also suppress the  corresponding  note
              in the generated TXT RRs, and the informational outputs in the MTA configuration.

       ! mta_group identifier

              Group that ought to be able to access DKIM private keys
              This should be a group which the MTA will have
              when it wishes to make a signature.

              For an Exim installation on Debian, `Debian-exim` is correct.

              This is used for the group ownership of
               `/var/lib/dkim-rotate/INSTANCE/priv`.

              The permissions `0750` will be used
              if dkim-rotate needs to create the directory.
              (Otherwise dkim-rotate will just check that the directory
              doesn't have global execute.)

              If `mta_group` is set to `-`,
              dkim-rotate will skip the chgrp,
              and (if it is creating the directory) create as `0700`.

              (Within the `priv/` directory,
              the files have a world-readable mode,
              so it is the directory permission which controls access.)

TUNING DIRECTIVES

! max_selector selector
Indicates number of CNAMEs (selectors) to use. selector should be a lowercase
letter (indicating that a to selector inclusive can be used) or a positive integer
(incidating that that many should be used). (If this number is revised downwards
after deployment, it may take a little while for the extra names to stop being
used.)

Default is 12 (or, equivalently, l).

If the configuration for an existing instance is changed, to reduce max_selector,
it will take a little while for dkim-rotate to stop using of the to-be-abolished
selectors:

While the number of selectors in use is more than configured, dkim-rotate will
print warnings. dkim-rotate --status can be used to verify whether old selectors
are no longer in use, and therefore whether it is OK to remove associated DNS
aliases etc.

! dns_lag duration
Time after successful installation of new zonefile, and nameserver reload, after
which the new DNS entries are expected to be visible to all clients.

duration is a number (possibly with decimal fraction) followed by one of the units
s m h d w.

Default is 4h.

! email_lag duration
Time after successful installation of new MTA configuration, and config reload,
after which we will assume that all messages signed with the key indicated by the
previous configration have been delivered, or bounced.

Default is 88h.

! instance_var_dir directory
Where to store statefiles, MTA configuration, zone files, etc. Default is
/var/lib/dkim-rotate/instance.

If instance specified on the command line as a pathname, there is no default for
instance_var_dir: it must then be specified in the config file.

! dkim_txt tag list

The values for the `TXT` RR, in domainkeys tag-list format,
not including the `p=`.
(see [RFC6376](https://datatracker.ietf.org/doc/html/rfc6376#section-3.6.1)).

dkim-rotate will append `; n=...; p=...` to this.
Default is `v=DKIM1; h=sha256; s=email.
where NOTE

! rsa_bits integer

Number of bits in generated RSA keys.
(Currently, only RSA is supported.)
Defaults to 2048.

! dns_reload shell command

Command to run to reload the nameserver,
after the zonefile has been updated.
Default: `rndc reload >/dev/null`.

! mta_reload shell command

Command to run to reload the MTA,
after the DKIM signing configuration has been updated.
Default: `true` (meaning, nothing needs to be done).

AUTHOR

       Copyright 2022 Ian Jackson and contributors to dkim-rotate.
       There is NO WARRANTY.
       SPDX-License-Identifier: GPL-3.0-or-later

NAME

INTRODUCTION

IMPORTANT DIRECTIVES

TUNING DIRECTIVES

AUTHOR

SEE ALSO