1. Introduction
===============
The dynamic LDAP back-end is a plug-in for BIND that provides an LDAP
database back-end capabilities. For now, it requires that BIND is patched
to support dynamic loading of database back-ends. You can get a patch
for your version here:
http://github.com/mnagy/bind-dynamic_db/downloads
Hopefully, the patch will once be included in the official BIND release.
Because of bug in dns_db_unregister() in older BIND versions, BIND >= 9.7.0a1
is required.
2. Features
===========
* support for dynamic updates
* SASL authentication
* SyncRepl (RFC 4533) for run-time synchronization with LDAP server
* read-query performance nearly same as with plain BIND
* AXFR and IXFR zone transfers are supported
3. Installation
===============
To install the LDAP back-end, extract the tarball and go to the unpacked
directory. Then follow these steps:
$ ./configure --libdir=<libdir>
$ make
Where <libdir> is a directory where your libdns is installed. This is
typically going to be /usr/lib or /usr/lib64 on 64 bit systems.
If configure script complains that it "Can't obtain libdns version",
please verify you have installed bind development files (package bind9-dev
or bind-devel) and you exported correct CPPFLAGS via
"export CPPFLAGS=`isc-config.sh --cflags`" command.
Then, to install, run this as root:
# make install
This will install the file ldap.so into the <libdir>/bind/ directory.
4. LDAP schema
==============
You can find the complete LDAP schema in the documentation directory. An
example zone ldif is available in the doc directory.
4.1 Zone (idnsZone) attributes
------------------------------
* idnsAllowDynUpdate
Allow dynamic update of records in this zone. If attribute doesn't exist,
value "dyn_update" from plugin configuration will be used.
* idnsAllowQuery
Specifies BIND9 zone ACL element. This attribute can be set multiple
times and are merged together to the one ACL.
Example:
idnsAllowQuery: 127.0.0.1
idnsAllowQuery: ::1
idnsAllowQuery: 192.168.1.0/24
In the example above clients with 127.0.0.1 and ::1 IP addresses and
clients from the 192.168.1.0/24 network are allowed to obtain records
from the zone.
You can specify IPv4/IPv6 address, IPv4/IPv6 network address in CIDR
format and "any" or "none" keywords. The "!" prefix (for example
!192.168.1.0/24) means negation of the ACL element.
If not set then zone inherits global allow-query from named.conf.
* idnsAllowTransfer
Uses same format as idnsAllowQuery. Allows zone transfers for matching
clients.
If not set then zone inherits global allow-transfer from named.conf.
* idnsAllowSyncPTR
Allow synchronization of A/AAAA records in zone with PTR records in reverse
zone. Reverse zone must have Dynamic update allowed.
(See idnsAllowDynUpdate attribute and dyn_update configuration parameter.)
* idnsForwardPolicy (default "first")
Specifies BIND9 zone forward policy. Proprietary value "none"
is equivalent to "forwarders {};" in BIND configuration,
i.e. effectively disables forwarding and ignores idnsForwarders
attribute.
Value "none" disables forwarding for given zone and ignores
global forwarders. Zone with forward policy "none" is considered
as type "master", not "forward".
Values "first" and "only" are relevant in conjunction with a valid
idnsForwarders attribute. Their meaning is same as in BIND9.
* idnsForwarders
Defines multiple IP addresses to which queries will be forwarded and
effectively creates "forward" zones.
It is multi-value attribute: Each IP address (and optional port) has to
be in own value. BIND9 syntax for "forwarders" is required.
Optional port can be specified by adding " port <number>" after IP
address. IPv4 and IPv6 addresses are supported.
Examples: "1.2.3.4" or "1.2.3.4 port 553" or "A::B" or "A::B port 553"
Zones with idnsForwarders attribute specified and forward policy other
than "none" are considered as "forward" zones. All records in LDAP
belonging to those zones are ignored and all queries are forwarded.
* idnsSOAserial
SOA serial number. It is automatically incremented after each change
in LDAP. External changes done by other LDAP clients are detected via
RFC 4533 (so-called syncrepl).
If serial number is lower than current UNIX timestamp, then
it is set to the timestamp value. If SOA serial is greater or equal
to current timestamp, then the serial is incremented by one.
(This is equivalent to BIND option 'serial-update-method unix'.)
In multi-master LDAP environments it is recommended to make
idnsSOAserial attribute non-replicated (locally significant).
It is recommended not to use multiple masters for single slave zone
if SOA serial is locally significant because serial numbers between
masters aren't synchronized. It will cause problems with zone
transfers from multiple masters to single slave.
5. Configuration
================
To configure dynamic loading of back-end, you must put a "dynamic-db"
clause into your named.conf. The clause must then be followed by a
string denoting the name. The name is not that much important, it is
passed to the plug-in and might be used for example, for logging
purposes. Following after that is a set of options enclosed between
curly brackets.
The most important option here is "library". It names a shared object
file that will be opened and loaded. The "arg" option specifies a string
that is passed directly to the plugin. You can specify multiple "arg"
options. The LDAP back-end follows the convention that the first word of
this string is the name of the setting and the rest is the value.
5.1 Configuration options
-------------------------
List of configuration options follows:
5.1.1 LDAP connection
---------------------
uri
The Uniform Resource Identifier pointing to the LDAP server we
wish to connect to. This string is directly passed to the
ldap_initialize(3) function. This option is mandatory.
Example: ldap://ldap.example.com
connections (default 2)
Number of connections the LDAP driver should try to establish to
the LDAP server. It's best if this matches the number of threads
BIND creates, for performance reasons. However, your LDAP server
configuration might only allow certain number of connections per
client.
base
This is the search base that will be used by the LDAP back-end
to search for DNS zones. It is mandatory.
auth_method (default "none")
The method used to authenticate to the LDAP server. Currently
supported methods are "none", "simple" and "sasl". The none
method is effectively a simple authentication without password.
bind_dn (default "")
Distinguished Name used to bind to the LDAP server. If this is
empty and the auth_method is set to "simple", the LDAP back-end
will fall-back and use the "none" authentication method.
password (default "")
Password for simple and SASL authentication. If the authentication
method is set to "simple" and the password is empty, the LDAP
driver will fall-back to the "none" authentication method.
sasl_mech (default "GSSAPI")
Name of the SASL mechanism to be used for negotiation.
sasl_auth_name
The user name to be used for SASL authentication.
sasl_user
The user name to be used for SASL proxy authorization.
sasl_password
The password to use for the SASL authentication.
sasl_realm
The SASL realm name.
krb5_keytab
Path to the kerberos keytab containing service credentials to be used
for SASL authentication. Append the "FILE:" prefix to the file path.
(FILE:/etc/named.keytab, for example)
krb5_principal
Kerberos principal of the service, used for SASL authentication.
If not set then it is copied from "sasl_user" option. Principal
is loaded from file specified in "krb5_keytab" option.
timeout (default 10)
Timeout (in seconds) of the queries to the LDAP server. If the LDAP
server don't respond before this timeout then lookup is aborted and
BIND returns SERVFAIL. Value "0" means infinite timeout (no timeout).
reconnect_interval (default 60)
Time (in seconds) after that the plugin should try to connect to LDAP
server again in case connection is lost and immediate reconnection
fails.
ldap_hostname (default "")
Sets hostname of the LDAP server. When it is set to "", actual
/bin/hostname is used. Please prefer "uri" option, this option should be
used only in special cases, for example when GSSAPI authentication
is used and named service has Kerberos principal different from
/bin/hostname output.
5.1.2 Special DNS features
--------------------------
fake_mname (default "")
Ignore value of the idnsSOAmName (primary master DNS name) attribute
and use this value instead. This allows multiple BIND processes to share
one LDAP database and every BIND reports itself as a primary master in
SOA record, for example.
sync_ptr (default no)
Set this option to "yes" if you would like to keep PTR record
synchronized with coresponding A/AAAA record for all zones.
If this option is set to "no", the LDAP driver will check
the idnsAllowSyncPTR attribute which specifies the synchronization
policy for PTR records in a zone. When an A/AAAA record is deleted
the PTR record must point to the same hostname.
dyn_update (default no)
Set this option to "yes" if you would like to allow dynamic zone updates.
This setting can be overridden for each zone individually
by idnsAllowDynUpdate attribute.
5.1.3 Plumbing
--------------
verbose_checks (default no)
Set this option to "yes" if you would like to log all failures
in internal CHECK() macros. This option is recommended only for
debugging purposes. It could produce huge amount of log messages
on a loaded system!
directory (default is
"dyndb-ldap/<current instance name from dynamic-db directive>")
Specifies working directory for plug-in. The path has to be writeable
by named because plug-in will create sub-directory for each zone.
These sub-directories will contain temporary files like zone dump, zone
journal, zone keys etc.
The path is relative to "directory" specified in BIND options.
5.2 Sample configuration
------------------------
Let's take a look at a sample configuration:
options {
directory "/var/named/";
};
dynamic-db "my_db_name" {
library "ldap.so";
arg "uri ldap://ldap.example.com";
arg "base cn=dns, dc=example, dc=com";
arg "auth_method none";
};
With this configuration, the LDAP back-end will try to connect to server
ldap.example.com with simple authentication, without any password. It
will then do an LDAP subtree search in the "cn=dns,dc=example,dc=com"
base for entries with object class idnsZone, for which the
idnsZoneActive attribute is set to True. For each entry it will find, it
will register a new zone with BIND. The LDAP back-end will keep each
record it gets from LDAP in its memory.
Working directory for the plug-in will be "/var/named/dyndb-ldap/my_db_name/",
so hypothetical zone "example.com" will use sub-directory
"/var/named/dyndb-ldap/my_db_name/example.com/".
5.3 Configuration in LDAP
-------------------------
Some options can be configured in LDAP as idnsConfigObject attributes.
Value configured in LDAP has priority over value in configuration file.
(This behavior will change in future versions!)
Following options are supported (option = attribute equivalent):
forwarders = idnsForwarders (BIND native option)
forward = idnsForwardPolicy (BIND native option)
sync_ptr = idnsAllowSyncPTR
Forward policy option cannot be set without setting forwarders at the same time.
6. License
==========
This package is licensed under the GNU General Public License, version 2
only. See file COPYING for more information.