ldap2dns

# LDAP to DNS gateway

ldap2dns is a program to read DNS (Domain Name Service) records from an LDAP directory and format them into flat files suitable for TinyDNS (or Bind).

ldap2dns reduces all kind of administration overhead: No more flat file editing, no more zone file editing. After having installed ldap2dns, the administrator only has to modify the data stored in the LDAP directory.
Optionally access control can be configured for each zone, GUIs can be more easily implemented, and add all other kind of zone and resource record information can be managed without interfering with the DNS server.
ldap2dns is designed to write ASCII data files used by tinydns from the djbdns package, but also may be used to write zone db files used by named as found in the BIND package.

ldap2dns is known to compile and run under Linux and Solaris using GCC or Sun Studio C Compiler.

Often it is desirable to store DNS information in a database rather than in flat text files. This can greatly help to reduce administration overhead since associate information such as billing contact, account management, etc. can be stored and processed inside the same database. Also due to the nature of DNS, information must be stored redundantly on two or more hosts. The classical data replication through zone transfer is unreliable, insecure and difficult to administer.
To solve this problem some proprietary attempts have been proposed to store DNS information in relational databases. The nature of DNS, however, is hierarchical and such should the database be. Using a relational database to store DNS information is undesirable, because it becomes difficult to store free form information. Within a hierachical data scheme, the administrator might define more than one IP-address for each canonical name. To implement such a feature in a relational database without breaking the normalization rules, one would have to add another table.
One of the most widely spread hierarchical database protocols is LDAP. ldap2dns retrieves DNS information stored in an LDAP directory service and generates a file suitable for name-servers.
The two most-widely-used domain name service daemons, named and tinydns are supported.
ldap2dns specifically has been designed to work with tinydns and is the favored name server daemon for the author of this program. ldap2dns can also generate files suitable for named version 8 (and possibly version 9), but this feature is not well supported.
There is a RFC for a format description how to store DNS information in LDAP. This paper a draft RFC which expired in February 1999, looks as if it has been specially designed to be used by named. This scheme does not have strict attribute-value-pair mapping, making it difficult to be used by user interfaces. It also lacks of an implementation (or I have never heard of any).
Since tinydns is going another descriptive way the original author implemented a similar object-scheme more suitable for tinydns.

- Install an LDAP server such as openldap. Other LDAP implementations may work but have not been tested. If you are building from source you will need to also install the development libraries and include files. On most package based systems these would be the -devel packages (example: openldap-devel).
- Install djbdns or BIND. Configuring the nameserver to automatically start and work in your environment is beyond the scope of this document.
- Install ldap2dns
  From RPM:

      $ sudo rpm -Uhv ldap2dns.rpm

  Replace "ldap2dns.rpm" with the file you have downloaded.
  Now that you have it installed, skip to Usage to continue.
  To build ldap2dns from source:
  Unpack the package and build it:

      $ gzcat ldap2dns.tar.gz | tar x
      $ cd ldap2dns-version
      $ make
      $ sudo make install

- Copy the file ldap2dns.schema into the directory /etc/openldap/schema. Add the following line to Your slapd.conf file:

      include         /etc/openldap/schema/ldap2dns.schema

  Now restart your LDAP server.

Note: If you are running OpenLDAP 2.0 or earlier look for appropriate schema files for your version in the deprecated/ subdirectory. These files are known to work as of ldap2dns 0.3.5 but are no longer supported for future feature updates.

- Start to populate your LDAP server with DNS information. As a first test do

      $ ldapadd -D "binddn" -w password < example.ldif

  Replace 'myorg' and 'binddn' with whatever is appropriate on Your system. Start a search and see if something was added

      $ ldapsearch -D "binddn" "objectclass=dnsrrset"

- Test ldap2dns

      $ ./ldap2dns -D "binddn" [ -b "searchbase" ] [ -w passwd ] -o data -o db -L

  This should create a 'data' file, a 'corp.local.db' file and should print the DNS content.
  Note: The data file is text data which can be processed with tinydns-data. corp.local.db is the file as used by named. If You are using bind, You also have to adopt the file /etc/named.conf and You have to restart named.

Two object-classes have been defined. DNSzone stores all the information to define a DNS zone, such as the SOA (Start Of Authority), serial numbers etc. DNSrrset is used to store the information for a single resource record, such as the domain name, IP-addresses, class and type.
Here are the tables:

#### DNSzone

This object-class represents a DNS zone. It is the container for all the resource records within a zone. Zones can be primary or secondary. If used in conjunction with tinydns zones are always primary. Secondary zones don't make sense anyway! In addition to being a container, the zone object has attributes related to the management of the zone. These include the zone's SOA information. Each zone-object can have none to many children of class DNSrrset.

ATTRIBUTE | VALUE | Comment
--- | --- | ---
objectclass | DNSzone | required
cn | common name | required
DNSzonename | Name of the zone | required, multivalued
DNSserial | Serial number of SOA | optional
DNSrefresh | Refresh time of SOA | optional, only used for zone transfers
DNSretry | Retry time of SOA | optional, only used for zone transfers
DNSexpire | Expire time of SOA | optional, only used for zone transfers
DNSminimum | Minimum time to live | optional, only used for zone transfers
DNSadminmailbox | Hostmaster's contact address | optional
DNSzonemaster | Primary nameserver for this zone | optional
DNStype | SOA | must be SOA
DNSclass | IN | must be IN
DNSttl | time to live | optional, only used with tinydns
DNStimestamp | timestamp | optional, only used with tinydns

- DNSzonename: This field is required to describe the zone's domain name, for instance myorg.com. More than one DNSzonename my be specified for a DNSzone so that the same host is accessable with different zonenames.
- DNSserial: This is the serial number as used for BIND's zone transfers. Here it is used to inform ldap2dns that it has to rebuild its data-file. Without increasing the serial number ldap2dns will ignore all modifications until it is restarted.
- DNSrefresh, DNSretry, DNSexpire, DNSminimum: You may safly ignore these numbers if You don't do zone-transfers. Since Your secondary nameserver will connect to the LDAP server the same way Your primary does, You don't need zone-transfers anyway.
- DNSzonemaster: Here you specify the canonical name of your primary nameserver.
- DNSadminmailbox: This is the contact address of Your DNS-administrator. The first dot is converted to a @.
- DNStype: Must be SOA (Start Of Authority)
- DNSclass: Must be IN (Internet, or do still use Chaosnet?)
- DNSttl: This is the time-to-live value as used by tinydns. If TTL is nonzero (or omitted), the timestamp is a starting time from whereon this zone's information is valid. If TTL is zero, the timestamp is an ending time (``time to die'').
- DNStimestamp: This is the timestamp as used by tinydns. It represents a string as external TAI64 timestamp, printed as 16 lowercase hexadecimal characters

#### DNSrrset

The Resource Record Set represents all of the resource records for a given host name within a zone. It must be a child of a DNSzone object.

ATTRIBUTE | VALUE | Comment
--- | --- | ---
objectclass | DNSrrset | required
cn | common name | required
DNSdomainname | Name of this record | optional, relative to zonename
DNSipaddr | IP address | optional, mutivalued
DNScname | Canonical name | optional, without ending dot relative to zonename
DNSpreference | integer | optional, only used for MX records
DNStype | A, CNAME, NS, MX, PTR or TXT | must be any valid record type
DNSclass | IN | must be IN
DNSttl | time to live | optional, only used with tinydns
DNStimestamp | timestamp | optional, only used with tinydns
DNSsrvpriority | SRV Priority | optional, defaults to 0 for SRV records
DNSsrvweight | SRV Weight | optional, defaults to 0 for SRV records
DNSsrvport | SRV Port | Required for SRV records

- DNSrrset: This object-class must be a direct child of DNSzone. Its dn should be specified as

      cn=domainname,cn=zonename,...

- DNSdomainname This is the partial domain-name, ie. the part in front of the zone-name.
- DNSipaddr: This specifies the IP-address in dotted format. It can be used for DNSrrset's of type A, NS, MX or PTR. DNSipaddr is multivalued to specifiy more than one IP-address for a service. If used in DNSrrset's with DNStype = PTR it overrides the old-fashioned form used in DNSdomainname such as 13.178.23.in-addr.arpa for reverse lookups.
- DNScname: Whenever there is a mapping of a domain-name to a canonical name, use this attribute. DNScname may be used for DNSrrset's with DNStype CNAME, NS, MX, PTR or TXT. If the last character of a CNAME is a dot its name is considered absolute. If it does not contain a dot, its name is prepended to the zone-name.
- DNSpreference: This number is the mail-exchange preference as used by BIND.
- DNStype: This must be A, CNAME, NS, MX, PTR or TXT. It specifies the DNSrrset type.
- DNSclass: Must be IN
- DNSttl: This is the time-to-live value as used by tinydns. If TTL is non-zero (or omitted), the time-stamp is a starting time from where-on this zone's information is valid. If TTL is zero, the timestamp is an ending time (``time to die'').
- DNStimestamp: This is the timestamp as used by tinydns. It represents a string as external TAI64 time-stamp, printed as 16 lowercase hexadecimal characters
- DNSsrvpriority: Integer representing the relative priority of this DNS SRV record. See menandmice.com for more information about DNS SRV records.
- DNSsrvweight: DNS SRV record weight field. Integer
- DNSsrvport: DNS SRV record port number. Integer

ldap2dns and ldap2dnsd recognize the following options:

    -D binddn specify the distinguished name to bind to the LDAP directory
    -w bindpasswd use bindpasswd as password for simple authentication
    -b searchbase use searchbase as starting point for search instead default
    -o data generate a "data" file to be processed by tinydns-data
    -o db for each zone generate a "<zonename>.db" file to be used by named
    -L[filename] print output in LDIF format to [filename] or stdout for reimport
    -h host specify the hostname of LDAP directory. Default is localhost
    -p port portnumber to connect to LDAP directory. Defaults is 389
    -H ldapURI URI for LDAP server (examples: ldap://hostname or ldaps://hostname:636)
    -v run in verbose mode
    -vv even more verbose
    -V print version and exit
    -u numsecs update DNS data every numsecs.
    -t timeout timeout for LDAP searches, in seconds
    -M reclimit Limit LDAP results to reclimit number of records.

ldap2dns and ldap2dnsd recognize the following environment variables:
TINYDNSDIR: Specifies the directory where ldap2dns writes its data file.
LDAP2DNS_UPDATE: Specifies the update intervall as the -u command line option would.
LDAP2DNS_OUTPUT: Specifies the default output, as the -o command line option would. ldap2dns and ldap2dnsd use the following parameters from /etc/ldap.conf if not specified on the command line: BASE: The LDAP search base.
HOST: The LDAP server.
PORT: The LDAP port.
If You are a tinydns user, run ldap2dns in /services/tinydns/root.
If You are an openldap user, the command line switches are the same as for ldapsearch or ldapadd.

    $ ldap2dns -D "binddn" [ -w passwd ] -b "searchbase" \
    -o data -e "cd /var/tinydns/root && /usr/bin/tinydns-data"

This generates a data file which is converted into a data.cdb by tinydns-data as soon as ldap2dns detects a modification in the LDAP directory. The password is required if You restrict read queries to authenticated users only. Test with

    $ dnsq any corp.local ipaddr

Replace ipaddr with whatever You configured tinydns to listen to. If You are a BIND user, run ldap2dns in /var/named with

    $ ldap2dns -D "binddn" -w passwd -b "searchbase" \
    -o db -e "kill -HUP `cat /var/run/named-pid`"

Do not forget to add You primary definition to your named.conf file. Your named should be restarted automatically as soon as ldap2dns detects a modification in the LDAP directory. If bind is not restarted, do so with

    # kill -HUP PID

Now run

    $ nslookup - localhost
    > ns1.corp.local

Note that nslookup only works with tinydns if your nameserver resolves its IP-address backwards.
When ldap2dns is invoked as ldap2dnsd, the program starts as backgound-daemon and continuously checks for modifications in the LDAP directory. If the the daemon sees a modification in the DNSserial numbers it updates the data or .db files, depending what kind of output was configured. This check is done about once a minute and is configurable.
The command-line options for ldap2dnsd are the same as for ldap2dns. Use the -u option to modify the update interval. You may also use -u on ldap2dns to start as a foreground daemon. This is useful if You want to run ldap2dns from daemontools.
These instructions assume you will be running ldap2dns under daemontoolsb> and that tinydns is also running under daemontools. These instructions also assume you are using Dan Bernstein's standard directory locations. Make sure you change the below examples to match your environment.
Start by creating the a non-root user to run your ldap2dns and associated logging mechanism:

    # groupadd -r ldap2dns
    # useradd -r -d /dev/null -s /bin/false -c "ldap2dns Daemon" \
     -g ldap2dns ldap2dns
    # groupadd -r l2dnslog
    # useradd -r -d /dev/null -s /bin/false -c "ldap2dns Logger" \
     -g l2dnslog l2dnslog

Next configure the ldap2dns area to be managed by daemontools. Typically this is /etc/ldap2dns

    # cd /etc
    # ldap2tinydns-conf ldap2dns l2dnslog /etc/ldap2dns /etc/tinydns/root

The syntax is close to tinydns-conf except that you will also need to specify the path to the root directory for tinydns. This is the directory that holds the data file.
Next edit the file /etc/ldap2dns/run and optionally the environment variables in /etc/ldap2dns/env as necessary for your environment. This may include configuring a base DN, a bind DN, a password, and an interval.
When everything is ready configured properly create a symlink from /etc/ldap2dns into /service. This action will cause daemontools to launch ldap2dns.

    # ln -s /etc/ldap2dns /service/ldap2dns

After a few seconds daemontools starts ldap2dnsd which itself generates data files whenever a modification is commited into the LDAP directory.
A perl-script import.pl is contained in this package. Edit the first lines of the script to conform to Your configuration. If You have installed the Perl packages Net::LDAP and Net::DNS skip the following lines, otherwise do

    # perl -MCPAN -e 'shell'
    (...snip...)
    > install Net::DNS
    > install Net::LDAP

Now check that Your nameserver allows zone transfers to your host and run the import script:

    $ echo 'primary mydomain.org ' | ./import.pl

for a single domain or

    # cat named.boot | ./import.pl

to populate Your LDAP directory.
Use the supplied data2ldap.pl in the scripts/ directory

    $ data2ldap.pl data data.ldif ou=DNS,dc=example,dc=com

More to come...
A browser-based administration toolkit, which connects directly to the LDAP-directory service.

- Write a man page.
- named.conf should be created automatically.

This program is Copyright 1999-2004 Jacob Rief and 2005-2006 Ben Klang
This program is licensed under the GPL version 2
ldap2dns was originally written by Jacob Rief (jacob.rief@tiscover.com). It is now maintained by Ben Klang (bklang@alkaloid.net). If you run ldap2dns on a production nameserver, please send the maintainer an email and mention on what OS and with which nameserver you do so.
Disclaimer: The author and all contributors disclaim any kind of warranty or liability or suitability for any purpose. By running this software you agree that you are a competent systems administrator and will bear the responsibility for your actions.

#### Latest Release: ldap2dns version 0.4.1

Released October 19, 2006
ChangeLog

#### Developer Access:

The bleeding edge of ldap2dns is in the Alkaloid Networks subversion repository found at https://svn.alkaloid.net/gpl/ldap2dns/trunk.
Following the Subversion standard, releases are kept in /gpl/ldap2dns/tags and branches are in /gpl/ldap2dns/branches.