nss-pam-ldapd - NSS and PAM libraries for name lookups and authentication using LDAP nss-pam-ldapd started as nss-ldapd which was a fork from nss_ldap which was originally written by Luke Howard of PADL Software Pty Ltd. 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. The software was renamed to nss-pam-ldapd when PAM code contributed by Howard Chu for the OpenLDAP nssov module was integrated. Solaris compatibility was developed by Ted C. Cheng of Symas Corporation. http://arthurdejong.org/nss-pam-ldapd/ Copyright (C) 1997-2006 Luke Howard Copyright (C) 2006-2007 West Consulting Copyright (C) 2006-2016 Arthur de Jong Copyright (C) 2009 Howard Chu Copyright (C) 2010 Symas Corporation 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-pam-ldapd library which consists of an NSS module to do name lookups to an LDAP directory server and a PAM module to do authentication to an LDAP server. The NSS part of this library was forked from nss_ldap as provided by Luke Howard of PADL Software Pty Ltd. The PAM module was mostly provided by Howard Chu of the OpenLDAP project. The NSS library allows distributing account, group, host and other configuration information from a central LDAP server. Because LDAP is a hierarchical directory service, information can be organised 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. The PAM library (module) can be used to perform authentication based on information inside the LDAP directory. Both libraries consist of a thin NSS or PAM part that proxies the requests to a local daemon (nslcd) that handles the LDAP lookups. This simplifies the software architecture and fixes some scalability and locking problems in the original design of nss_ldap. It is also possible to use the thin NSS and PAM modules together with the nssov overlay in the OpenLDAP server (slapd). The three parts (NSS module, PAM module, and nslcd server) can be built separately and are not strongly tied together. This means that for instance you can still use pam_ldap and use the NSS module from nss-pam-ldapd or use an alternative implementation of nslcd (for instance with the nssov slapd overlay or the pynslcd implementation). 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. One of those problems were host name lookups through LDAP which could cause deadlocks. Another is that nss_ldap loaded an SSL library into executables that may not be designed to load it (e.g. problem with suid applications). A number of refactoring steps were done 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 was re-added using compatibility wrappers. The most practical improvements 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 its own connection - hostname lookups should now be deadlock-free because the LDAP server name is no longer looked up using the ldap method - avoid problems with TLS connections in suid binaries and other process-local configuration - it is easier to debug because logging in nslcd can be enabled without the need to restart all processes doing name lookups - unavailability timeouts are global instead of per-process comparison to pam_ldap ---------------------- The PAM module that is currently implemented contains functionality for authentication, account management, password management and session management. The nslcd daemon currently implements authentication, authorisation and password modification. The OpenLDAP nssov overlay also implements session functionality. supported C libraries (for NSS module) -------------------------------------- This library currently supports the GNU C Library, the Solaris C library and the FreeBSD C library. supported name databases ------------------------ Currently the following name databases are supported: aliases, ethers, group, hosts, netgroup, networks, passwd, protocols, rpc, services and shadow When using IPv6 ipHostNumber attributes, the address in LDAP must be in the preferred form as defined in section 2.2 of RFC1884, specifically the format as returned by inet_ntop(3). All leading zeros should be omitted and the longest range of zeroes should be replaced with :: (e.g. fe80::218:bff:fe55:c9f). MAC addresses in the macAddress attribute should be in maximal, colon separated hex notation (e.g. 00:00:92:90:ee:e2). automounter map lookups (which are also defined in /etc/nsswitch.conf) are currently not supported because the NSS interface is not used for these. The common autofs implementation (on GNU/Linux) currently uses its own method for getting the maps from LDAP. Although mail aliases are exposed through NSS, most mail servers parse /etc/aliases themselves (bypassing NSS) and getting aliases from LDAP requires some configuration in the mail server. The publickey, bootparams and netmasks are currently 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 PAM implementation ---------------------------- The PAM module is currently only regularly tested on Linux PAM but other PAM implementations should also work. supported LDAP libraries ------------------------ The current version of nss-pam-ldapd has been developed with OpenLDAP 2.4 but other LDAP libraries and older versions of OpenLDAP may also work. unsupported features -------------------- Since nss-pam-ldapd was forked from nss_ldap most of the features that came with nss_ldap are available. The most important differences: - the configuration file formats are not fully compatible - rootbinddn/rootbindpw support is removed and is not likely to return (the rootpwmoddn and rootpwmodpw work differently but accomplish the same thing) For the PAM module some functionality is missing. Comparing it to pam_ldap: - only BIND authentication is supported - only LDAP password modify EXOP is supported as password changing mechanism Some things work a little different in nss-pam-ldapd. For instance the attribute defaults and overrides of nss_ldap are implemented with mapping expressions and pam_ldap's pam_check_*_attr options can be implemented with the pam_authz_search option. INSTALLATION ============ The nss-pam-ldapd library uses autoconf and automake for building. Installing nss-pam-ldapd should be as simple as: % ./configure % make % make install It is a good idea to first go through the options of configure by running: % ./configure --help The last step (make install) should install the libnss_ldap.so.* and pam_ldap.so files and the daemon (nslcd). The proper location of the NSS and PAM modules are guessed. The boot process needs to be modified to start the nslcd daemon at the right time. It is recommended to create a dedicated user for the nslcd daemon. Configure this user in /etc/nslcd.conf using the uid and gid options. CONFIGURATION ============= After installation, the name service switch configuration file (/etc/nsswitch.conf) needs to be modified to do name lookups using the new module. This 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 Configuring PAM differs a little from platform to platform but this is a minimal set-up for files under /etc/pam.d: auth sufficient pam_unix.so auth sufficient pam_ldap.so use_first_pass auth required pam_deny.so account required pam_unix.so account sufficient pam_ldap.so account required pam_permit.so session required pam_unix.so session optional pam_ldap.so password sufficient pam_unix.so nullok md5 shadow use_authtok password sufficient pam_ldap.so try_first_pass password required pam_deny.so Lastly, a configuration file for nslcd (by default /etc/nslcd.conf) needs to be made. See the shipped manual page for details on the format and options. It should at the very 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-pam-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-pam-ldapd supports a wide range of possible LDAP schema configurations and it can be customized heavily. The LDAP schema used is described in RFC 2307. Groups using the member attribute that hold distinguished names (RFC 2307bis) are also supported (but see group membership below for more information). default attributes ------------------ This paragraph describes the mapping between the NSS lookups and the LDAP database. The mapping may be modified by changing the nslcd.conf configuration file. See the nslcd.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 (by default mapped to "*") gidNumber - gid memberUid - members (user names) member - 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 passwd (objectClass=posixAccount) uid - account name userPassword - password (by default mapped to "*") uidNumber - uid gidNumber - gid gecos - gecos 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 - date of last password change shadowMin - days before password may be changed again shadowMax - days after which password must be changed shadowWarning - days before max password age to present a warning shadowInactive - days after max password age that account is disabled shadowExpire - account expiration date shadowFlag - reserved field using Microsoft Active Directory -------------------------------- When using Microsoft Active Directory server some changes need to be made to the nslcd.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 number of lookups). The attribute values are user names (same as the uid attribute for posixAccount entries) and are returned without further processing. The second method is to use DN values in the member 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 LDAP server supports the deref control (provided by the deref overlay in OpenLDAP) the DN to uid expansing is performed by the LDAP server. If the DN value already contains a uid value (e.g. uid=arthur, dc=example, dc=com) a further lookup is skipped and the uid value from the DN is used. For other DN values an extra lookup is performed to expand it to a uid. These lookups are cached and are configurable with the cache dn2uid configuration option. The member attribute may also contain the DN of another group entry. These nested groups are parsed recursively depending on the nss_nested_groups option. Currently, the memberOf attribute in posixAccount entries is unsupported. case sensitivity ---------------- Most values in NSS databases are considered case-sensitive (e.g. the user "Foo" is a different user from the user "foo"). Most values in an LDAP database are however considered case-insensitive. nss-pam-ldapd tries to solve this problem by adding an extra filtering layer to ensure that when looking for the user "foo" it will not consider a user "Foo" that is found in LDAP. For the group, netgroup, passwd, protocols, rpc, services and shadow maps the matches will be checked case-sensitively and for aliases, ethers, hosts and networks matches will be case-insensitive (this seems to be what Glibc is doing currently in flat files). Only searching for groups by user is done case-insensitive. In all cases the case-use in the LDAP directory is returned. This behaviour can be disabled with the ignorecase configuration option but may be a security risk. Note that having entries that only differ in case is a bad idea and will likely get you in trouble. One example of such a problem is that the DN uid=test,dc=example,dc=com is considered the same in LDAP as uid=TEST,dc=example,dc=com. REPORTING BUGS ============== If you find any bugs or missing features please send email to nss-pam-ldapd-users@lists.arthurdejong.org If you are using a packaged version of nss-pam-ldapd you are encouraged to use the distributor's bug tracking system. Please include as much information as possible (platform, output of configure if compilation fails, error messages, output of nslcd -d, etc). Patches are more than welcome (also see the file HACKING).