Directory Services: LDAP

• We will be using a virtual machine in the faculty's cloud.
• Create a VM
• When creating a virtual machine in the Launch Instance window:
  • Select Boot from image in Instance Boot Source section
  • Select Centos 7 in Image Name section
  • Select the m1.small flavor.
• The username for connecting to the VM is student

We will be working entirely on the VM. In order to setup and manage LDAP on our server, we will be using 389-ds. This tools offers a more user-friendly way of managing LDAP, rather than using cumbersome CLI commands.

Add in the /etc/hosts file an entry for our future hostname. This will be necessary for ldap to work. We will be using the scgc.ro domain in this laboratory and the server will be identified by server.scgc.ro.

10.9.x.y  server.scgc.ro

In order for 389-ds to function properly, some default Linux limitations have to be changed. Add the following lines in /etc/sysctl.conf

net.ipv4.tcp_keepalive_time = 300
net.ipv4.ip_local_port_range = 1024 65000
fs.file-max = 64000

These are needed to allow more connections to the LDAP server. To reload these settings run the following command:

sysctl -p

Also add the following lines in the /etc/security/limits.conf file:

*               soft     nofile          8192   
*               hard     nofile          8192

This will allow 389-ds to open up to 8192 processes, if needed. You will need to relogin for these change to take place.

Finally, add the following line to the /etc/pam.d/login file.

session    required     /lib/security/pam_limits.so

We will also need a user account for LDAP. Create a new account and set a password for it.

[root@server ~]# useradd ldapadmin
[root@server ~]# passwd ldapadmin

Before we install the 389-ds, we need to add the Extra Packages for Enterprise Linux(EPEL), as the 389-ds available in the default packages is too basic for our needs. Too install EPEL, run the following command:

[root@server ~]# yum install epel-release

After this we are ready to install 389-ds using the command:

[root@server ~]# yum install 389-ds

Now it’s time to configure LDAP server. Run the following command to configure 389 directory server.

[root@server ~]# setup-ds-admin.pl

Please read the instructions carefully before entering the information required.

==============================================================================
This program will set up the 389 Directory and Administration Servers.

It is recommended that you have "root" privilege to set up the software.
Tips for using this program:
  - Press "Enter" to choose the default and go to the next screen
  - Type "Control-B" then "Enter" to go back to the previous screen
  - Type "Control-C" to cancel the setup program

Would you like to continue with set up? [yes]: #press Enter

==============================================================================
Your system has been scanned for potential problems, missing patches,
etc.  The following output is a report of the items found that need to
be addressed before running this software in a production
environment.

389 Directory Server system tuning analysis version 14-JULY-2016.

NOTICE : System is x86_64-unknown-linux3.10.0-123.9.3.el7.x86_64 (1 processor).

Would you like to continue? [yes]: #press Enter

==============================================================================
Choose a setup type:

   1. Express
       Allows you to quickly set up the servers using the most
       common options and pre-defined defaults. Useful for quick
       evaluation of the products.

   2. Typical
       Allows you to specify common defaults and options.

   3. Custom
       Allows you to specify more advanced options. This is 
       recommended for experienced server administrators only.

To accept the default shown in brackets, press the Enter key.

Choose a setup type [2]: #press Enter

==============================================================================
Enter the fully qualified domain name of the computer
on which you're setting up server software. Using the form
<hostname>.<domainname>
Example: eros.example.com.

To accept the default shown in brackets, press the Enter key.

Warning: This step may take a few minutes if your DNS servers
can not be reached or if DNS is not configured correctly.  If
you would rather not wait, hit Ctrl-C and run this program again
with the following command line option to specify the hostname:

    General.FullMachineName=your.hostname.domain.name

Computer name [server]: server.scgc.ro

==============================================================================
The servers must run as a specific user in a specific group.
It is strongly recommended that this user should have no privileges
on the computer (i.e. a non-root user).  The setup procedure
will give this user/group some permissions in specific paths/files
to perform server-specific operations.

If you have not yet created a user and group for the servers,
create this user and group using your native operating
system utilities.

System User [dirsrv]: ldapadmin
System Group [dirsrv]: ldapadmin

==============================================================================
Server information is stored in the configuration directory server.
This information is used by the console and administration server to
configure and manage your servers.  If you have already set up a
configuration directory server, you should register any servers you
set up or create with the configuration server.  To do so, the
following information about the configuration server is required: the
fully qualified host name of the form
<hostname>.<domainname>(e.g. hostname.example.com), the port number
(default 389), the suffix, the DN and password of a user having
permission to write the configuration information, usually the
configuration directory administrator, and if you are using security
(TLS/SSL).  If you are using TLS/SSL, specify the TLS/SSL (LDAPS) port
number (default 636) instead of the regular LDAP port number, and
provide the CA certificate (in PEM/ASCII format).

If you do not yet have a configuration directory server, enter 'No' to
be prompted to set up one.

Do you want to register this software with an existing
configuration directory server? [no]: #press Enter 

==============================================================================
Please enter the administrator ID for the configuration directory
server.  This is the ID typically used to log in to the console.  You
will also be prompted for the password.

Configuration directory server
administrator ID [admin]: #press Enter
Password:
Password (confirm): 

==============================================================================
The information stored in the configuration directory server can be
separated into different Administration Domains.  If you are managing
multiple software releases at the same time, or managing information
about multiple domains, you may use the Administration Domain to keep
them separate.

If you are not using administrative domains, press Enter to select the
default.  Otherwise, enter some descriptive, unique name for the
administration domain, such as the name of the organization
responsible for managing the domain.

Administration Domain [scgc.ro]: #press Enter

==============================================================================
The standard directory server network port number is 389.  However, if
you are not logged as the superuser, or port 389 is in use, the
default value will be a random unused port number greater than 1024.
If you want to use port 389, make sure that you are logged in as the
superuser, that port 389 is not in use.

Directory server network port [389]: #press Enter

==============================================================================
Each instance of a directory server requires a unique identifier.
This identifier is used to name the various
instance specific files and directories in the file system,
as well as for other uses as a server instance identifier.

Directory server identifier [server]: #press Enter

==============================================================================
The suffix is the root of your directory tree.  The suffix must be a valid DN.
It is recommended that you use the dc=domaincomponent suffix convention.
For example, if your domain is example.com,
you should use dc=example,dc=com for your suffix.
Setup will create this initial suffix for you,
but you may have more than one suffix.
Use the directory server utilities to create additional suffixes.

Suffix [dc=scgc, dc=ro]: #press Enter

==============================================================================
Certain directory server operations require an administrative user.
This user is referred to as the Directory Manager and typically has a
bind Distinguished Name (DN) of cn=Directory Manager.
You will also be prompted for the password for this user.  The password must
be at least 8 characters long, and contain no spaces.
Press Control-B or type the word "back", then Enter to back up and start over.

Directory Manager DN [cn=Directory Manager]: #press Enter
Password: 
Password (confirm): 

==============================================================================
The Administration Server is separate from any of your web or application
servers since it listens to a different port and access to it is
restricted.

Pick a port number between 1024 and 65535 to run your Administration
Server on. You should NOT use a port number which you plan to
run a web or application server on, rather, select a number which you
will remember and which will not be used for anything else.

Administration port [9830]: #press Enter

==============================================================================
The interactive phase is complete.  The script will now set up your
servers.  Enter No or go Back if you want to change something.

Are you ready to set up your servers? [yes]: 
Creating directory server . . .
Your new DS instance 'server' was successfully created.
Creating the configuration directory server . . .
Beginning Admin Server creation . . .
Creating Admin Server files and directories . . .
Updating adm.conf . . .
Updating admpw . . .
Registering admin server with the configuration directory server . . .
Updating adm.conf with information from configuration directory server . . .
Updating the configuration for the httpd engine . . .
Starting admin server . . .
The admin server was successfully started.
Admin server was successfully created, configured, and started.
Exiting . . .
Log file is '/tmp/setupGq9QqD.log'

To start 389-ds on reboot, run the following commands:

[root@server ~]# systemctl enable dirsrv.target
Created symlink from /etc/systemd/system/multi-user.target.wants/dirsrv.target to /usr/lib/systemd/system/dirsrv.target.
[root@server ~]# systemctl enable dirsrv-admin
Created symlink from /etc/systemd/system/multi-user.target.wants/dirsrv-admin.service to /usr/lib/systemd/system/dirsrv-admin.service.

To check that LDAP is working we can use either CLI commands or the 389-ds GUI.

To check from CLI, run the following command:

[root@server ~]# ldapsearch -x -b "dc=scgc,dc=ro"
# extended LDIF
#
# LDAPv3
# base <dc=scgc,dc=ro> with scope subtree
# filter: (objectclass=*)
# requesting: ALL
#

# scgc.ro
dn: dc=scgc,dc=ro
objectClass: top
objectClass: domain
dc: scgc

# Directory Administrators, scgc.ro
dn: cn=Directory Administrators,dc=scgc,dc=ro
objectClass: top
objectClass: groupofuniquenames
cn: Directory Administrators
uniqueMember: cn=Directory Manager

# Groups, scgc.ro
dn: ou=Groups,dc=scgc,dc=ro
objectClass: top
objectClass: organizationalunit
ou: Groups

# People, scgc.ro
dn: ou=People,dc=scgc,dc=ro
objectClass: top
objectClass: organizationalunit
ou: People

# Special Users, scgc.ro
dn: ou=Special Users,dc=scgc,dc=ro
objectClass: top
objectClass: organizationalUnit
ou: Special Users
description: Special Administrative Accounts

# Accounting Managers, Groups, scgc.ro
dn: cn=Accounting Managers,ou=Groups,dc=scgc,dc=ro
objectClass: top
objectClass: groupOfUniqueNames
cn: Accounting Managers
ou: groups
description: People who can manage accounting entries
uniqueMember: cn=Directory Manager

# HR Managers, Groups, scgc.ro
dn: cn=HR Managers,ou=Groups,dc=scgc,dc=ro
objectClass: top
objectClass: groupOfUniqueNames
cn: HR Managers
ou: groups
description: People who can manage HR entries
uniqueMember: cn=Directory Manager

# QA Managers, Groups, scgc.ro
dn: cn=QA Managers,ou=Groups,dc=scgc,dc=ro
objectClass: top
objectClass: groupOfUniqueNames
cn: QA Managers
ou: groups
description: People who can manage QA entries
uniqueMember: cn=Directory Manager

# PD Managers, Groups, scgc.ro
dn: cn=PD Managers,ou=Groups,dc=scgc,dc=ro
objectClass: top
objectClass: groupOfUniqueNames
cn: PD Managers
ou: groups
description: People who can manage engineer entries
uniqueMember: cn=Directory Manager

# search result
search: 2
result: 0 Success

# numResponses: 10
# numEntries: 9

The -x parameter uses simple authentication. In this case the connection is anonymous. The -b parameter specifies the node in the LDAP tree/directory to traverse.

To start the 389-ds GUI run the following command (from student user):

[student@server ~]$ 389-console -a http://server.scgc.ro:9830

If everything is configured correctly, the following GUI should pop up:

Login as admin with password used at setup. To see the LDAP entries, go to Users and Groups tab and press Search.

Using the GUI from the previous subtask, add a User to LDAP to the People Organizational Unit. Use your name for the User data. Hint: User and Groups, Create

Use ldapsearch to verify that the User is added.

We want to use LDAP for different Linux tasks, such as user administration or hostnames. In order, to achieve this we will need the nss-pam-ldapd package(yum install nss-pam-ldapd). The nss-pam-ldapd package allows LDAP directory servers to be used as a primary source of name service information. The file contains options, one on each line, defining the way NSS lookups and PAM actions are mapped to LDAP lookups.

We have to specify the LDAP server and base DN for the authentication system to know where to get the data. We can use the following command for this:

authconfig --enableldap --enableldapauth --ldapserver=ldap://server.scgc.ro:389/ --ldapbasedn="dc=scgc,dc=ro" --update

Let us now add a new user from LDAP. To do this we will use the GUI interface. Create a new user and enable the Posix User Attributes from the Posix User section. For UID and GID use unused values.

After adding the user we can now check that we can login.

[root@server ~]# getent passwd han
han:*:1500:1500:Han Solo:/home/han:/bin/bash
[root@server ~]# su han
bash-4.2$ id
uid=1500(han) gid=1500 groups=1500 context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023

Edit the User created at 1.4 to also be a Linux user.

When authenticating as a new user through LDAP, the home directory will not automatically be created. This can be problematic. In order to solve this issue, we can configure pam to create the home directory on the first login. For this you need to add the following line in the /etc/pam.d/login file.

session    required     pam_mkhomdir.so skel=/etc/skel umask=0027

We will need to enable this functionality by running the command:

[root@server ~]# authconfig --enablemkhomedir --update

Now when logging in for the first time, the home directories should be created.

Add a group from LDAP in which you will include the user created previously. Create a Group in the Groups organizational unit. Don't forget to add Posix attributes.

Name resolving can be done using different resources (e.g. DNS, files such as /etc/hosts). The way in which name resolving is performed is specified in the /etc/nsswitch.conf file, in particular the hosts component. We can also use LDAP for name resolving. In order to this we first need to add ldap to the /etc/nsswitch.conf file.

hosts:      files dns ldap

We will follow the schema used to add hostnames from CLI through LDAP. This is presented in detail here.

Firstly, we will create a new Organizational Unit for the hosts from the GUI. Select the Base DN as the Organizational Unit. The name of our new OU will be Hosts.

After creating our OU for our hosts, we will need more advanced functionality, so we will use the Directory Server from the Servers and Applications tabs. In the Directory Server, in the Directory tab, we will select the Hosts from scgc. Right clicking will bring up a menu from which we will select New… and Other. From the list we will select iphost. We will add a new host for the server IP.

After this the new host should be configured.

[root@server ~]# getent hosts
127.0.0.1       localhost localhost.localdomain localhost4 localhost4.localdomain4
127.0.0.1       localhost localhost.localdomain localhost6 localhost6.localdomain6
10.9.109.77     server.scgc.ro server
10.9.109.77     ldaphost
[root@server ~]# ping ldaphost -c 1
PING ldaphost (10.9.109.77) 56(84) bytes of data.
64 bytes from server.scgc.ro (10.9.109.77): icmp_seq=1 ttl=64 time=0.046 ms

--- ldaphost ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.046/0.046/0.046/0.000 ms

Using the same methods from task 2, add entries for the following entities (all entities will be Posix):

• group starwars
  • user Han Solo
  • user Yoda
  • user Leia Organa
  • user Luke Skywalker
• group lotr
  • user Gandalf
  • user Frodo Baggins
• hostname hogwarts (for the server IP)