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:
https://github.com/spacekpe/bind-dynamic_db
Hopefully, the patch will once be included in the official BIND release.
BIND >= 9.9.0 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
* DNSSEC in-line signing is supported, including dynamic updates
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.
Alternatively, the latest version can be obtained from Git repository.
You can use following commands to prepare latest source tree for compilation:
$ git clone https://git.fedorahosted.org/git/bind-dyndb-ldap.git
$ cd bind-dyndb-ldap
$ autoreconf -fvi
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 Master zone (idnsZone)
--------------------------
Object class idnsZone is equivalent to type "master" statement in named.conf.
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 as one string.
Example 1: idnsAllowQuery: 192.0.2.1;
In the first example above, only the client with 192.0.2.1 IP address
is allowed to query records from the zone.
Example 2: idnsAllowQuery: !192.0.2.33; 192.0.2.0/24;
In the second example, queries from client 192.0.2.33 are refused
but queries from all other clients in the 192.0.2.0/24 network
are allowed.
You can specify IPv4/IPv6 address, IPv4/IPv6 network address in CIDR
format, and "any" or "none" keywords. The "!" prefix (for example
!192.0.2.33) 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.
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 recursive queries will be
forwarded. This is equivalent to "forwarders" statement in "master"
zone configuration.
I.e. local BIND replies authoritatively to queries when possible
(including authoritative NXDOMAIN answers) so forwarding affects only
queries made by BIND to answer recursive queries which cannot be
answered locally. Please see
https://lists.isc.org/pipermail/bind-users/2006-January/060810.html
https://lists.isc.org/pipermail/bind-users/2011-March/083244.html
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"
* idnsName
Absolute name of DNS zone. It is recommended to use names with trailing
period, e.g. "example.com."
* idnsSecInlineSigning (default FALSE)
DNSSEC in-line signing configuration. Value TRUE is equivalent to
following zone configuration in named.conf (default BIND values):
auto-dnssec maintain;
sig-validity-interval 2592000; # 30 days
# re-sign interval will be 648000 seconds = 7.5 days
sig-signing-signatures 10;
sig-signing-nodes 10;
sig-signing-type 65534;
update-check-ksk yes;
dnssec-loadkeys-interval 60; # minutes
key-directory "<plugin-instance-dir>/<zone-name>/keys";
There is no way to change those values at this moment.
* 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.
* idnsZoneActive
Boolean which speicifies if particular DNS zone should be visible
to clients or not. This attribute can be changed at run-time.
Inactive zones are loaded into memory in the same way as active zones.
The only difference is that inactive zones are not added to DNS view
used by bind-dyndb-ldap.
Zone will be re-added to DNS view if idnsActiveZone attribute is
changed to TRUE so the change should be almost immediate.
Usual zone maintenance (serial number maintenance, DNSSEC in-line
signing etc.) is done for all zones, no matter if the zone
is active or not. This allows us to maintain zone journal so IXFR
works correctly even after zone re-activation.
* nSEC3PARAMRecord
NSEC3PARAM resource record definition according to RFC5155.
Zone without NSEC3PARAM RR will use NSEC by default.
4.2 Forward zone (idnsForwardZone)
----------------------------------
Object class idnsForwardZone is equivalent to type "forward" statement
in named.conf.
Attributes:
* idnsForwarders
Defines multiple IP addresses to which all queries for sub-tree of DNS
will be forwarded. This is equivalent to "forwarders" statement in
"forward" zone configuration.
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"
* 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.
Values "first" and "only" are relevant in conjunction with a valid
idnsForwarders attribute. Their meaning is same as in BIND9.
* idnsName
Absolute name of DNS zone. It is recommended to use names with trailing
period, e.g. "example.com."
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.
See section 6 (DNSSEC) for examples.
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 use RFC 4533 refresh&persist search in the "cn=dns,dc=example,dc=com"
base for entries with object class idnsZone and idnsRecord.
For each idnsZone entry it will find, it will register a new zone with BIND.
For each idnsRecord entry it will create domain name in particular zone.
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/master/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. DNSSEC support
=================
In-line signing support in this plugin allows to use this BIND feature
for zones in LDAP.
Signatures are automatically generated by plugin during zone loading
and signatures are never written back to LDAP. DNSKEY, RRSIG, NSEC and NSEC3
records in LDAP are ignored because they are automatically managed by BIND.
NSEC3 can be enabled by writting NSEC3PARAM RR to particular zone object
in LDAP.
Dynamic updates made to in-line signed zones are written back to LDAP as usual
and respective signatures are automatically re-generated as necessary.
Key management has to be handled by user, i.e. user has to
generate/delete keys and configure key timestamps as appropriate.
Key directory for particular DNS zone is automatically configured to value:
<plugin-instance-dir>/master/<zone-name>/keys
<plugin-instance-dir> is described in section 5.1.3 of this file.
<zone-name> is (transformed) textual representation of zone name without
trailing period.
Zone name will be automatically transformed before usage:
- root zone is translated to '@' to prevent collision with filesystem '.'
- digits, hyphen and underscore are left intact
- letters of English alphabet are downcased
- all other characters are escaped using %ASCII_HEX form, e.g. '/' => '%2F'
- final dot is omited
- labels are separated with '.'
Example:
* BIND directory: "/var/named"
* bind-dyndb-ldap directory: "dyndb-ldap"
* LDAP instance name: "ipa"
* DNS zone: "example.com."
* Resulting keys directory: "/var/named/dyndb-ldap/ipa/master/example.com/keys"
* DNS zone: "TEST.0/1.a."
* Resulting keys directory: "/var/named/dyndb-ldap/ipa/master/test.0%2F1.a/keys"
Make sure that keys directory and files is readable by user used for BIND.
7. License
==========
This package is licensed under the GNU General Public License, version 2
only. See file COPYING for more information.