Maintaining several domains ("zones") can be a hassle. Often, a lot of basic
information is shared between domains (name, mail or web servers, anti-spam
configuration etc.). CNAMEs can help to keep information in a single location,
but are not compatible e.g. with information stored at the apex (the domain name
itelf), and thus are of limited or no use for the above-mentioned shared
information. When creating a new zone, a previous zone can be copied; however,
if later things have to change for these domains, a lot of manual labor is
required, prone to errors. DNS Temple tries to simplify this.
Main site:
$ORIGIN example.com.
$TTL 86400
@ SOA (ns1.example.com. hostmaster.example.com. 2020121901 3600 1800 2419200 300)
NS ns1.example.com.
NS ns2.example.com.
MX 10 mail.example.com.
TXT "v=spf1 mx ~all"
TXT "google-site-verification=zeePiegahyeiVoh4SheiK5ootees2Uy4DaiKawoh"
A 192.0.2.80
AAAA 2001:db8:1234:5678::80
CAA 0 issue "letsencrypt.org"
ns1 A 203.0.113.53
AAAA 2001:db8:1:2::53
ns2 A 198.51.100.53
AAAA 2001:db8:3:4::53
# Web
www A 192.0.2.80
AAAA 2001:db8:1234:5678::80
# Mail
autodiscover CNAME mail
autoconfig CNAME mail
mail A 192.0.2.25
AAAA 2001:db8:1234:5678::25
smtp CNAME mail
imap CNAME mail
dkim._domainkey TXT "v=DKIM1;k=rsa;t=s;s=email;p=MII..."
_dmarc TXT "v=DMARC1; p=none; rua=mailto:[email protected]; fo=1:d:s"
# Cloud
cloud A 192.0.2.90
AAAA 2001:db8:1234:5678::90
One of many secondary sites:
$ORIGIN example.ch.
$TTL 86400
@ SOA (ns1.example.com. hostmaster.example.com. 2020121901 3600 1800 2419200 300)
NS ns1.example.com.
NS ns2.example.com.
MX 10 mail.example.com.
TXT "v=spf1 mx ~all"
TXT "google-site-verification=isei8oox1gahc7oox1ezith9eith2ki8aigh9aiD"
A 192.0.2.80
AAAA 2001:db8:1234:5678::80
CAA 0 issue "letsencrypt.org"
# Web
www A 192.0.2.80
AAAA 2001:db8:1234:5678::80
# Mail
autodiscover CNAME mail
autoconfig CNAME mail
mail A 192.0.2.25
AAAA 2001:db8:1234:5678::25
smtp CNAME mail
imap CNAME mail
dkim._domainkey TXT "v=DKIM1;k=rsa;t=s;s=email;p=MII..."
_dmarc TXT "v=DMARC1; p=none; rua=mailto:[email protected]; fo=1:d:s"
The mail, _dkim, and www entries could be changed to CNAMEs and the SPF
entry could use include:, but many problems would still remain, such as:
- Changing the address of the web server would require changing all the files anyway.
- Changing the list of name servers, certificate authorities, or mail servers cause modification of every file.
SOAserials need to be incremented carefully to avoid hard-to-diagnose problems.- Adding an additional service, such as a secondary mail server, CardDAV, CalDAV, or XMPP would require touching every file.
- Over time, files will diverge, due to some services (such as cloud) appearing
in some zones only or authentication entries (such as
google-site-verification, maybe_domainkey) differing between domains. - You will lose oversight because of all the clutter and differences.
Create a central configuration where shared information is collected:
addresses:
ns1: 203.0.113.53 2001:db8:1:2::53
ns2: 198.51.100.53 2001:db8:3:4::53
mail: 192.0.2.25 2001:db8:1234:5678::25
web: 192.0.2.80 2001:db8:1234:5678::80
cloud: 192.0.2.90 2001:db8:1234:5678::90
variables:
ca: letsencrypt.org
dkimkey: |
"MII..."Create a set of templates using {variable} references, $ADDRESS explosions
(expanding dynamically to a set of A and AAAA records), $INCLUDEs, and
$DEFAULT values for some variables using magic {_domain} and {_serial}
variables:
header.t:
$ORIGIN {_domain}
$TTL 86400
@ SOA (ns1.example.com. hostmaster.example.com. {_serial} 3600 1800 2419200 300)
NS ns1.example.com.
NS ns2.example.com.
CAA 0 issue "{ca}"
mail.t:
$DEFAULT domain {_domain}.
$ADDRESS mail mail
{domain} MX 10 mail.example.com.
TXT "v=spf1 mx ~all"
autodiscover.{domain} CNAME mail
autoconfig.{domain} CNAME mail
smtp.{domain} CNAME mail
imap.{domain} CNAME mail
dkim._domainkey.{domain} TXT "v=DKIM1;k=rsa;t=s;s=email;p={dkimkey}"
_dmarc.{domain} TXT "v=DMARC1; p=none; rua=mailto:[email protected]; fo=1:d:s"
web.t:
$ADDRESS web @
$ADDRESS web www
common.t:
$INCLUDE header.t
$INCLUDE mail.t
$INCLUDE web.t
These configuration templates will be shared among the zones, resulting in much more compact files:
$INCLUDE common.t
$INCLUDE mail.t domain=noreply
$ADDRESS ns1 ns1
$ADDRESS ns2 ns2
$ADDRESS cloud cloud
@ TXT "google-site-verification=zeePiegahyeiVoh4SheiK5ootees2Uy4DaiKawoh"
$INCLUDE common.t
$ADDRESS ns1 ns1
$ADDRESS ns2 ns2
$ADDRESS cloud cloud
@ TXT "google-site-verification=isei8oox1gahc7oox1ezith9eith2ki8aigh9aiD"
The BIND syntax is augmented to achieve the power of variables, modules, and functions. The changes, however, are minimal, to retain familiarity.
Behind the scenes, scoped variables and include parameters do all the work:
Each $INCLUDE creates a new context, initialized with the variables of the
parent file and the parameters passed in the $INCLUDE statement.
The new or extended statements are:
$DEFAULT: Setting default values for variables,$INCLUDE: Create a child context and include the file, and$ADDRESS: Simplify the handling of addresses, whether IPv4, IPv6 or groups thereof.
The configuration file is structured as follows:
config:
serial: <`online`|`dateserial`|`unixtime`|any integer>
skip: <comma-separated list of `empty`, `comment`>
extensions:
in: <extension on input file names>
out: <extension for output file names>
addresses:
<name1>: <addresses1…>
<name2>: <addresses2…>
...
variables:
<name1>: <value1>
<name2>: <value2>
...skip suppresses the output of empty and/or comment lines (starting with
;).
The in extension is removed from the input file names, if present, and the
out extension is appended. The basename is also used to set the _domain
variable, below.
Serial number modes are as follows:
online: Queries the name servers and increments; but uses at least the value thatdateserialwould produce. For this, existingSOAserials are obtained by querying the local resolver and an authoritative name server. Highest priority for authoritative name server is given to the master name (MNAME) extracted from theSOArecord returned by the local resolver, with the remainingNSentries as fallbacks. The minimum SOA corresponds to whatdate -u +%Y%m%d00would return.dateserial: Uses theYYYYMMDD00formatunixtime(default): Uses the current second since start of the epoch- An integer, e.g.
1: Use this integer as the serial number
Variable names in curly brackets ({}) are expanded directly when reading the
line from the input file (the entire Python format() specification is
supported). Only after that, lines are parsed; i.e., whitespace or quotes have
no special significance to dnstemple and cannot be escaped (at least as of
now).
The following special variables are automatically set:
_config: The file name the YAML configuration has been read from._domain: The domain name, as determined by the basename of the top-level file, i.e., the file specified on the command line, after removing theinextension._serial: A serial number usable for theSOArecord.
All variable names starting with _ are reserved.
One of the important reasons for using dnstemple is to make addressing more
dynamic. This is similar to a variable, but with extra possibilities:
- Be able to change addresses in multiple zone files, even if
CNAMEs are not possible (e.g., at the apex) - Reduce inter-zone dependencies: Have the same address in multiple zones,
without causing multiple lookups (i.e., follow the
CNAME) when resolving or requiring the other zone to be ready. - Handle IPv4 and IPv6 addresses using the same syntax (no deciding between
AandAAAA) - Support multiple addresses for a name (IPv4+IPv6, but also multiple of each) without having to add/drop lines in the zone file
Addresses are defined similar to variables, but with the following distinctions:
-
They are defined in the
addressblock -
They are used with the
$ADDRESSdirective, which expands them into any number ofAandAAAArecords, as appropriate -
They can be defined recursively, e.g. for fail-over/load-balancing setups:
addresses: server1: 192.0.2.11 2001:db8:1234:5678::11 server2: 192.0.2.12 farm: server1 server2
There is no need to use variable notation. Anything not an IPv4 or IPv6 address will be recursively looked up as an address, up to 5 levels deep.
Of course, variables could also be included using the standard
{}variable notation, but then the reference is to thevariablessection.
Include the given file. The set of variables available to the included file is the set of variables available to the parent, plus the variables passed as parameters. This is similar to how parameters would be passed to functions.
Separation is done at all whitespace, after variable substitution, without consideration of quotes or escape characters. So do not try to include whitespace into variable values.
Create one line for each of the addresses listed for the named address parameter
specified in the configuration file. Both IPv4 and IPv6 addresses can be mixed
arbitrarily and will be prefixed with A or AAAA, as appropriate. Typically,
the prefix will just be a name, but can also contain TTL information; in fact,
anything that could precede the A or AAAA.
If the specified variable is undefined or empty, set it to the value given.