Warning Livedoc is no longer being updated and will be deprecated shortly. Please refer to https://documentation.tjhsst.edu.

NSS LDAP

From Livedoc - The Documentation Repository
Revision as of 12:01, 13 August 2008 by William Yang (talk | contribs) (Administration/Management: Added some previously used longish commands.)
Jump to: navigation, search

LDAP is used to store NSS (Name Service Switch) information for the UNIX passwd and group databases. All information about network users, such as UNIX uid/gid, home directory, shell, and other group membership is handled through NSS.

History

Previously, the CSL used NIS to store network user information. However, when the decision was made to integrate CSL accounts and authentication with Windows Active Directory (previously all CSL accounts were managed separately and required an application form to receive), LDAP was chosen to replace NIS as the backend for the NSS database.

Integrated authentication using LDAP and Kerberos was initially deployed in lab 231 during the spring of 2006. Sun Directory Server 5.2 was used at the time, replicated from sol across what are now known as chuku and ekhi. During the summer following, LDAP was moved into a VMWare virtual machine known as daystar in order to run LDAP on a faster system. However, for reasons not completely understood, the VM subsequently developed problems during the fall of 2006 and resulted in NSS becoming painfully slow on both rockhopper (at that time used for all of lab 231 and 16 LTSP nodes in the CSL) and the rest of the CSL workstations. In order to remedy the situation, /etc/passwd was rapidly deployed as a flatfile across all affected systems. Hesiod was subsequently set up as the NSS database for the remainder of the school year and the beginning of the next.

During the winter of 2007-08, NSS was switched back to LDAP following various discussions. (Need more information.) LDAP was configured on chuku and mihr, running Sun Directory Server 6.

Current

NSS LDAP is currently used by nearly all *NIX systems managed by the CSL. It is running in LDOMs ldap1 and ldap2.

Configuring LDAP on clients

Linux

  • libnss-ldap (or similar) needs to be installed.
  • Edit /etc/libnss-ldap.conf:
    • Setup LDAP servers 198.38.16.59:388, 198.38.16.12:388, and 198.38.16.13:388.
    • Use search base: dc=csl,dc=tjhsst,dc=edu.
    • Set bind_timelimit to 2
    • Set bind_policy to soft
    • Set nss_base_passwd to ou=people,
    • Set nss_base_group to ou=group,
  • Edit /etc/nsswitch.conf to use "files ldap" for the passwd and group databases. The two lines should look like this:
passwd:     files ldap
group:      files ldap
  • You may need to restart nscd.

Solaris

WARNING: There was at least one point in the history of Sun Directory Server where setting up the LDAP client on the LDAP server was not supported because the client was started before the server was, causing a halt in system boot because of a failure to initialize the client. I'm not sure if this is still the case, but if it is, you will need an init script to disable the client in SMF until the server starts, and then restart the client after the server starts. In the CSL, this is easily done by installing the STJinitd-sunds package.

  • Run the following command:
/usr/sbin/ldapclient manual -a credentialLevel=anonymous \
 -a defaultSearchBase="dc=csl,dc=tjhsst,dc=edu" \
 -a defaultSearchScope=sub \
 -a defaultServerList="198.38.16.12:388 198.38.16.13:388" \
 -a followReferrals="TRUE" \
 -a preferredServerList="198.38.16.59:388" \
 -a serviceSearchDescriptor=passwd:ou=people,dc=csl,dc=tjhsst,dc=edu \
 -a serviceSearchDescriptor=group:ou=group,dc=csl,dc=tjhsst,dc=edu
  • On most CSL systems: You are done.
  • On stock Solaris systems (and possibly some CSL systems):
    • The ldapclient command has installed an nsswitch.conf that assumes you use LDAP for everything. And I mean EVERYTHING. But that's rarely the case anywhere. So cp /etc/nsswitch.dns /etc/nsswitch.conf. Then edit /etc/nsswitch.conf to use "files ldap" for passwd and group. See Linux section above for sample of what this will look like.
    • pkill nscd to restart it (Solaris 10), or restart it some other way.

Admin-only access

Follow the above directions, but wherever you see an ou=people, replace it with an ou=sysadmins. Only sysadmins with LDAP entries in ou=sysadmins will be able to access that system. Note that additional access control can, and is often, managed by using hostname groups (i.e. the LDAP POSIX group named after the hostname of the system). This is currently not done on Solaris systems, but is done on most Linux systems.

LDAP Server Software

Both of the below applications are part of Sun Java System Directory Server Enterprise Edition 6.

NOTE: If the database needs to be rebuilt from scratch and data reloaded from LDIF dumps, you may need to get Identity Synchronization to "prepare" Directory Server as it needs to modify the schema with new object classes and attribute types.

Sun Java System Directory Server

  • Sun's implementation of an LDAP server.
  • Can fully integrate with nsswitch for all NSS databases (currently only using passwd and group).
  • Currently running in one-way replication on ldap1 (master) and ldap2.
  • For installation and configuration notes, see Sun Java System Directory Server.

Sun Java System Identity Synchronization for Windows

  • Connects and synchronizes users from Active Directory to Sun Directory Server and maps/synchronizes specified attributes (currently only one-way from AD to Sun).
  • For installation and configuration notes, see Identity Synchronization for Windows.

Directory Structure

  • Everything below is relative to a root dn of dc=csl,dc=tjhsst,dc=edu.
  • The subtree ou=Services and entry uid=PSWConnector are used by Identity Synchronization. Please do not touch those entries.
  • Groups are referenced by cn (i.e. cn=allaccess,ou=group,dc=csl,dc=tjhsst,dc=edu). Users are referenced by uid (i.e. uid=wyang,ou=2008,ou=students,ou=people,dc=csl,dc=tjhsst,dc=edu).

ou=group

This subtree contains POSIX groups. Currently we have 3 major classes of groups:

  • Primary: Each LDAP user's default group is one of these. There are a few subclasses:
    • Students/graduation year: The name of each group is TJ and then a two digit year, except in the case of 2000, which has name TJ2K. The gidnumber is the four digit graduation year.
    • "Adult" users: Staff members are assigned to group "faculty" with gidnumber 1984. Separating parents/external users into a separate group would be advisable, but they presently share the "faculty" group.
    • "users": This is presently used for all LDAP user entries in the ou=sysadmins subtree (see below).
  • Host/VM access control: Each of these groups (gid starting at 1000) has the hostname of the system that it is designed to control access for. The group has a list of users that should be granted login access to that system; however, some of the systems listed may not necessarily have group control implemented, rendering the LDAP group's membership moot. The group is not used to grant root access on a system; that is controlled independent of LDAP at this time. The members of the "allaccess" group (gid 1337) are grant login access on all systems that have the LDAP group access control scheme configured.
  • System/service groups: These are primarily used by the Solaris systems, but can also be used by others. It is sometimes easier to ensure that any particular group used by a system service will have the same ID across multiple systems by adding it to LDAP, hence the existence of this class of groups. These have gids starting at 5000.

There are some miscellaneous groups scattered in there. For instance, "commons_mm" (gid 8000) is the primary group for all music card users.

ou=people

This is the subtree used for the NSS passwd database on all general use systems. It is itself made up of several more sub-ous. The major ones are listed below. Others may be created as needed (for example, the josti2008 ou contains temporary users that were created for a JOSTI 2008 interactive user experience in one particular presentation; although the users are still in LDAP, they cannot login because their Kerberos credentials are expired).

ou=legacy

Most NIS users were loaded into this ou so legacy accounts could still have their uids looked up, and previous admins that retained their Kerberos accounts can still log in. Some NIS users were not imported because their username already existed in one of the other ous.

ou=parents

Parents that have login access for website editing or for whatever other purpose go here. Some parents may actually be in ou=legacy if they were created during the NIS era.

ou=special

This contains things that don't belong in any other category. Some system service users go here (see "System/service groups" in the ou=group section above for why we do this). Music card users also go here, although they could also have their own ou since there seem to be enough of them nowadays.

  • IMPORTANT: Most users that are added here should also be added to the ou=special in ou=sysadmins (see below).

ou=staff

Well yes...faculty and staff have their own ou. Naturally.

ou=students

No student users go directly in here; they go into another subou under this ou by graduation year first. At time of writing, ous exist for 2006 through 2050 (most of these latter ones are empty).

ou=sysadmins

This contains...well...sysadmins. The distinction from ou=people is primarily for access control on non-general-use servers.

ou=special

This is basically a copy of ou=special from above. The difference is that non-general-use servers are configured to see this ou=special, while general-use systems see the one in ou=people. For example, it is important to have the music card users here and above since music card users are logged in to on a general use system, but the NFS server, which is non-general use, also needs to be able to look up the username and uid.

Administration/Management

See Sun Java System Directory Server for general ways to administer Sun Directory Server.

Scripts

Currently there are a few bash scripts to help with administration. They are currently located on the Sun administrative volume in the "ds" directory.

update_nssldap.sh

This is the big one. While Identity Synchronization will create the new LDAP entries when new AD user objects are created, it doesn't know how to fill in all the POSIX values, such as uid and home directory. So we have a script that can fill them in. This script iterates on all accounts that do not have the posixAccount objectClass set yet.

This script must be run by someone with AFS admin. It must be run on a system that has the AFS client and tools installed as it handles the AFS side of user-creation as well. It currently must also be run on a system with both the Sun LDAP tools in /usr/bin and the OpenLDAP tools in /usr/local/bin. Perhaps someone should try and rewrite the script to only need one set of tools. Currently it is recommended to run this script on arcturus. The NSS LDAP Manager password will also be needed to gain admin-level access to LDAP. (Again, maybe someone wants to implement GSSAPI or other binding mechanism that allows users to be admins without knowing the Manager password.)

Should the active NSS LDAP database become lost or corrupted and no backups workable, requiring a rebuild from scratch, historical NSS data will be lost. However, the update_nssldap.sh script knows how to retrieve user information from AFS using pts, so users and home directories will not be duplicated if they already exist in AFS. This feature depends on usernames being unique for all time, which they should be by now.

Home directories are created from a skeleton found at /afs/csl.tjhsst.edu/service/skel. Adjust the afs_server and afs_vicep variables to control what server and partition new homedir volumes are created on. Some other variables may also be of interest, such as quota and host.

If the directory structure of AFS or LDAP ever changes for either students or staff, this script will need to be reviewed and updated, otherwise things will fail and/or get created in the wrong places!

backup.sh

The name says it all. The database is dumped out in a dumps subdirectory. Each backup operation creates 2 LDIFs, one for the data and another for ACIs. Files are created with the format hostname.dumpYYYYMMDDHHmmss, with an ending of acis.ldif or .ldif, depending on the contents.

This script may be run from any Solaris system that has the Sun LDAP client tools in /usr/bin. Again, Manager access will be needed. Dumps will be sent to the dumps directory in whatever your current working directory is; traditionally dumps have been kept in ds/dumps on the Sun admin volume.

If the LDAP server changes, this script will need to be updated.

group_manage.sh

This script makes it easy to add users to groups. It can be cumbersome to use for a lot of users, so you might find it easier to read the code and generate your own LDIF to import to the LDAP server if handling many users. It does NOT create or delete groups, nor does it remove users from groups. To perform those operations, the script will need to be written to do more, or you will need to use one of the two below methods.

This script may be run from any Solaris system that has the Sun LDAP client tools in /usr/bin. Again, Manager access will be needed. See update_nssldap.sh section for comment on using GSSAPI or other binding for other users to make changes to LDAP. If that's implemented, group administration should be delegatable so, for instance, shodan's administrator can add users to the shodan group without being able to add users to the fiordland group.

If the LDAP server or directory structure changes, this script will need to be updated.

Some potentially useful commands

Here are a few complex commands that have been used in the past that may come in handy at one point or another in the future. Note that the commands assume you understand the command syntax; they are usually incomplete by themselves, or they may be out-of-date: To look up users that have a home directory but don't exist in LDAP:

for i in `ls -1`; do if [ "`ldapsearch -h chuku -p 388 -x -b ou=2011,ou=students,ou=people,dc=csl,dc=tjhsst,dc=edu -LLL uid=$i  dn`" = "" ]; then echo $i; fi;done

To look up users that are in LDAP but are missing a home directory:

for i in `ldapsearch -h chuku -p 388 -x -b ou=2011,ou=students,ou=people,dc=csl,dc=tjhsst,dc=edu -LLL uid=* dn|cut -d"=" -f2|cut -d"," -f1`; do if [ ! -d $i ] ; then echo $i;fi; done

To count tombstones (see Sun docs for what this means): ldapsearch -h chuku -p 388 -x -b dc=csl,dc=tjhsst,dc=edu -D "cn=Directory Manager" -WLLL objectclass=nstombstone dn|grep dn|wc -l

See Also