nss-ldapd - NSS library for name lookups using LDAP nss-ldapd is a fork from nss_ldap which was originally written by Luke Howard of PADL Software Pty Ltd. http://www.padl.com/OSS/nss_ldap.html In 2006 Arthur de Jong of West Consuling forked the library to split it into a thin NSS part and a server part. Most of the code was rewritten. http://ch.tudelft.nl/~arthur/nss-ldapd/ Copyright (C) 1997-2006 Luke Howard Copyright (C) 2006, 2007 West Consulting Copyright (C) 2006, 2007, 2008 Arthur de Jong This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA INTRODUCTION ============ This is the nss-ldapd library which is an NSS module to do name lookups to an LDAP directory server. This library was forked from nss_ldap as provided by Luke Howard of PADL Software Pty Ltd. The library allows distributing account, group, host and other configuration information from a central LDAP server throughout an organisation. Because LDAP is a hierarchical directory service, you can distribute the information in a manner which reflects an organisational structure. This contrasts with the flat, single domain policy of NIS. LDAP has many of the advantages of NIS+ (security and scalability) without the complexity. The system will work alongside your existing NIS, NIS+, DNS and flat file name services. This library consists of a thin NSS part that communicates with a local daemon that handles the LDAP lookups. This simplifies the architecture and fixes some scalability and locking problems in the original design. improvements over nss_ldap -------------------------- The fork from nss_ldap was done to implement some major design changes to fix some structural problems in the library. The biggest of those problems were host name lookups through LDAP which could cause deadlocks in most cases and some general name lookup problems during booting (when the LDAP server was not started or not yet reachable). With nss-ldapd a number of refactoring steps were taken to simplify the code and improve maintainability. Legacy code was removed and support for non-Linux operating systems was initially removed to make the code more readable. Portability will be re-added once the architecture stabilises. The most practical improvements of nss-ldapd over nss_ldap are: - the LDAP library is not loaded for every process doing LDAP lookups - the number of connections to the LDAP server is limited, because not every process will open it's own connection (this problem is also mitigated by using nscd) - hostname lookups should now be deadlock-free because the LDAP server name is no longer looked up using the ldap method - the setup is easier to debug because logging on the server component can be enabled without affecting "normal" processes This package runs a local daemon that will be enabled during the boot process. This daemon will handle connections to the LDAP server and accept NSS requests from a named socket (/var/run/nslcd/socket). The thin NSS library will proxy requests to the daemon. Note that the package currently cannot be used on the same system alongside nss_ldap. supported C libraries --------------------- This library currently only supports the GNU C Library. Support for other C libraries has been removed in a refactoring step. Compatibility code and support for other C libraries will be added in due time upon request. supported name databases ------------------------ Currently the following name databases are supported: aliases, ethers, group, hosts, netgroup, networks, passwd, protocols, rpc, services and shadow Note that for when using IPv6 hosts entries, the addresses in the LDAP directory must be in their preferred form. The same is true for mac addresses for the ethers database. Otherwise the address->entry lookups will not work. For more details on the preferred form see http://ldap.akbkhome.com/index.php/attribute/ipHostNumber.html and http://ldap.akbkhome.com/index.php/attribute/macAddress.html automounter map lookups (which are also defined in /etc/nsswitch.conf) are not supported because the NSS interface is not used for these. The common autofs implementation (on GNU/Linux) currently uses it's own method for getting the maps from LDAP. Although aliases is exposed through NSS, most mailservers parse /etc/aliases by themselves and getting aliases from LDAP requires some configuration in the mailserver. The publickey, bootparams and netmasks are currently also unsupported. Some investigation should be done if these are needed for anything, which interfaces should be exported and how the LDAP schema part should look like. supported LDAP libraries ------------------------ The current version of nss-ldapd has been developed with OpenLDAP 2.4 but adding support for other LDAP libraries with similar interfaces should not be too hard. unsupported features -------------------- Since nss-ldapd was forked from nss_ldap most of the features that came with nss_ldap are available. However, not all features have extensively tested yet and may cause problems. - attribute value default and overrides have been removed (but may reappear some day if requested) - SSL/TLS support is untested but will be tested when the core code stabilizes - the configuration file formats are not fully compatible - nested groups are currently unsupported - rootbinddn/rootbindpw support is removed and is not likely to return In general, the focus is to have the functionality that is present be well tested and supported. INSTALLATION ============ The nss-ldapd library uses autoconf and automake for building. Installing nss-ldapd should be as simple as: % ./configure % make % make install That said, it is a good idea to go first through the options of configure by running: % ./configure --help The last step (make install) should install the libnss_ldap.so.* file and the daemon (nslcd). The boot process needs to be manually modified to start the daemon at the right time. CONFIGURATION ============= After installation the name service switch configuration file (/etc/nsswitch.conf) needs to be modified to do name lookups using the new module. Also, the nss-ldapd configuration file (specified at configure time) needs to be modified to contain to the correct LDAP configuration. Editing nsswitch.conf consist mostly of adding ldap in the list of lookup methods in the right place. See the nsswitch.conf(5) manual page for details on the format. As an example the file could look a little like this: # the following contain normal unix user and group information passwd: files ldap group: files ldap shadow: files ldap # hostname lookups through ldap before dns should work now hosts: files ldap dns networks: files ldap # normal flat-file definitions protocols: files ldap services: files ldap ethers: files ldap rpc: files ldap netgroup: ldap # whether alias lookups really use NSS depends on the mail server aliases: files ldap Furthermore a configuration file (by default /etc/nss-ldapd.conf) needs to be made. The location of this file can be specified with configure. See the shipped manual page for details on the format and options. It should at least contain something like: # the location of LDAP server uri ldap://localhost/ # search base for all queries. base dc=example,dc=net service discovery through DNS ----------------------------- nss-ldapd supports looking up LDAP server names through DNS SRV records as specified in RFC 2782. However, Priority and Weight are not considered separately and a single list of servers in added as if they had been specified with uri options in the configuration file. To use this feature specify DNS as an uri in the configuration file and include something like the following in your zone: _ldap._tcp SRV 10 0 389 ldapserver LDAP SCHEMA =========== nss-ldapd supports a wide range of possible LDAP schema configurations. Furthermore it can be customized heavily. The LDAP schema used is described in RFC 2307. Groups with distinguished name members (instead of login names) (RFC 2307bis) are also supported, although use of memberUid has much better performance (see below for details). default attributes ------------------ This paragraph describes the mapping between the NSS lookups and the LDAP database. The mapping may be modified by changeging the nss-ldapd.conf configuration file. See the nss-ldapd.conf(5) manual page for details. aliases (objectClass=nisMailAlias) cn - alias name rfc822MailMember - members of the alias (recipients) ethers (objectClass=ieee802Device) cn - host name macAddress - ethernet address group (objectClass=posixGroup) cn - group name userPassword - password gidNumber - gid memberUid - members (user names) uniqueMember - members (DN values) hosts (objectClass=ipHost) cn - host name (and aliases) ipHostNumber - addresses netgroup (objectClass=nisNetgroup) cn - netgroup name nisNetgroupTriple - triplets describing netgroup entries memberNisNetgroup - reference to other netgroup networks (objectClass=ipNetwork) cn - network name ipNetworkNumber - network address ipNetmaskNumber - network netmask passwd (objectClass=posixAccount) uid - account name userPassword - password uidNumber - uid gidNumber - gid gecos - gecos cn - gecos (if gecos is unset) homeDirectory - home directory loginShell - shell protocols (objectClass=ipProtocol) cn - protocol name ipProtocolNumber - protocol number rpc (oncRpc) cn - rpc name oncRpcNumber - rpc number services (objectClass=ipService) cn - service name ipServicePort - service port ipServiceProtocol - service protocol shadow (objectClass=shadowAccount) uid - use name userPassword - password shadowLastChange - last change of password shadowMax - days before password may be changed shadowMin - days after which password must be changed shadowWarning - expiry warning shadowInactive - account is disabled if no password is changed shadowExpire - account expiration shadowFlag - reserved field using Microsoft Active Directory -------------------------------- When using Microsoft Active Directory server (typically on Microsoft Windows 2000) some changes need to be made to the nss-ldapd.conf configuration file. The included sample configuration file has some commented out attribute mappings for such a set-up. group membership ---------------- Currently, two ways of specifying group membership are supported. The first, by using the memberUid attribute, is the simplest and by far the fastest (takes the least amount of lookups). This attributes maps to user names with the same values as the uid attribute would hold for posixAccount entries. The second method is to use DN values in the uniqueMember attribute (attribute names can be changed by using the attribute mapping options as described in the manual page). This is potentially a lot slower because in the worst case every DN has to be looked up in the LDAP server to find the proper value for the uid attribute. If the DN value already contains a uid value (e.g. uid=arthur, dc=example, dc=com) the lookup is skipped and the value from the DN is used. A cache is maintained that holds on to DN to uid translations for 15 minutes (see DN2UID_CACHE_TIMEOUT in nslcd/passwd.c). In all cases, duplicate users are returned only once. Currently, having nested groups by uniqueMember values pointing to other groups, as well as the memberOf attribute in posixAccount entries are unsupported. MISC NOTES ========== Most values in the NSS databases are considered case-sensitive (e.g. the user "Foo" is a different user from "foo"). Values in an LDAP database are however case-insensitive. This may cause problems in some corner cases, especially when nscd is used for caching. For example, when doing a lookup for the user "Foo" the user "foo" will be returned if it exists in the database. REPORTING BUGS ============== If you find any bugs or missing features please send email to arthur@ch.tudelft.nl If you are using the Debian package you are encouraged to use the BTS. Please include as much information as needed (platform, output of configure if compilation fails, output of the failure, etc). Patches are more than welcome (also see the file HACKING).