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 f TXT ...).

The zonefile’s prevailing TTL applies to the generated RRS, and can therefore be adjusted using the name‐
server’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 con‐
figuration 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 there‐
fore 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 configuration 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-ro‐
tate/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`.

! 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