Installing & Configuring OpenLDAP Server On CentOS 6.4

In this post I will try to explain, how to install and configure OpenLDAP Server 2.4 on CentOS 6.4. Here I have a minimal installation of CentOS 6.4 x86_64.

Pre-requisites:

• Working DNS Server : If you don't know how to configure DNS, please click the link for step by step configuration of BIND DNS http://easylinuxtutorials.blogspot.com/2011/11/setting-up-dns-server-in-rhel-6.html
• Server should be synced with NTP Server. Please follow my post for NTP Server configuration
• Disable SELinux

Steps for Installing & Configuring OpenLDAP Server: 

Install OpenLDAP server and client packages
[root@ldap1 ~]# yum install openldap openldap-servers openldap-clients -y

Installation of openldap-servers package gives a template slapd.conf with an example bdb configured. In this example, We will modify the slapd.conf to convert it to cn=config format. cn=config is a new feature of OpenLDAP 2.4 which enables dynamic changes to configuration without requiring to restart.

Copy the example slapd.conf to /etc/openldap/
[root@ldap1 ~]# cp /usr/share/openldap-servers/slapd.conf.obsolete /etc/openldap/slapd.conf

Generate the encrypted password for rootdn to use in /etc/openldap/slapd.conf
[root@ldap1 ~]# slappasswd
New password:
Re-enter new password:
{SSHA}GtG8bcLGeN/rf1iStKFK2pu0C2EZf/RX

Copy the generated password and edit the /etc/openldap/slapd.conf
Note: In the below slapd.conf file changes are highlighted with red colour. 
[root@ldap1 ~]# vim /etc/openldap/slapd.conf
#
# See slapd.conf(5) for details on configuration options.
# This file should NOT be world readable.
#
include         /etc/openldap/schema/corba.schema
include         /etc/openldap/schema/core.schema
include         /etc/openldap/schema/cosine.schema
include         /etc/openldap/schema/duaconf.schema
include         /etc/openldap/schema/dyngroup.schema
include         /etc/openldap/schema/inetorgperson.schema
include         /etc/openldap/schema/java.schema
include         /etc/openldap/schema/misc.schema
include         /etc/openldap/schema/nis.schema
include         /etc/openldap/schema/openldap.schema
include         /etc/openldap/schema/ppolicy.schema
include         /etc/openldap/schema/collective.schema

# Allow LDAPv2 client connections.  This is NOT the default.
allow bind_v2

# Do not enable referrals until AFTER you have a working directory
# service AND an understanding of referrals.
#referral       ldap://root.openldap.org

pidfile         /var/run/openldap/slapd.pid
argsfile        /var/run/openldap/slapd.args

# Load dynamic backend modules
# - modulepath is architecture dependent value (32/64-bit system)
# - back_sql.la overlay requires openldap-server-sql package
# - dyngroup.la and dynlist.la cannot be used at the same time

# modulepath /usr/lib/openldap
# modulepath /usr/lib64/openldap

# moduleload accesslog.la
# moduleload auditlog.la
# moduleload back_sql.la
# moduleload chain.la
# moduleload collect.la
# moduleload constraint.la
# moduleload dds.la
# moduleload deref.la
# moduleload dyngroup.la
# moduleload dynlist.la
# moduleload memberof.la
# moduleload pbind.la
# moduleload pcache.la
# moduleload ppolicy.la
# moduleload refint.la
# moduleload retcode.la
# moduleload rwm.la
# moduleload seqmod.la
# moduleload smbk5pwd.la
# moduleload sssvlv.la
# moduleload syncprov.la
# moduleload translucent.la
# moduleload unique.la
# moduleload valsort.la

# The next three lines allow use of TLS for encrypting connections using a
# dummy test certificate which you can generate by running
# /usr/libexec/openldap/generate-server-cert.sh. Your client software may balk
# at self-signed certificates, however.
#TLSCACertificatePath /etc/openldap/certs
#TLSCertificateFile "\"OpenLDAP Server\""
#TLSCertificateKeyFile /etc/openldap/certs/password

# Sample security restrictions
#       Require integrity protection (prevent hijacking)
#       Require 112-bit (3DES or better) encryption for updates
#       Require 63-bit encryption for simple bind
# security ssf=1 update_ssf=112 simple_bind=64

# Sample access control policy:
#       Root DSE: allow anyone to read it
#       Subschema (sub)entry DSE: allow anyone to read it
#       Other DSEs:
#               Allow self write access
#               Allow authenticated users read access
#               Allow anonymous users to authenticate
#       Directives needed to implement policy:
# access to dn.base="" by * read
# access to dn.base="cn=Subschema" by * read
# access to *
#       by self write
#       by users read
#       by anonymous auth
#
# if no access controls are present, the default policy
# allows anyone and everyone to read anything but restricts
# updates to rootdn.  (e.g., "access to * by * read")
#
# rootdn can always read and write EVERYTHING!

# enable on-the-fly configuration (cn=config)
database config
access to *
        by dn.exact="gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth" manage
        by * none

# enable server status monitoring (cn=monitor)
database monitor
access to *
        by dn.exact="gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth" read
        by dn.exact="cn=Manager,dc=example,dc=com" read
        by * none

#######################################################################
# database definitions
#######################################################################

database        bdb
suffix          "dc=example,dc=com"
checkpoint      1024 15
rootdn          "cn=Manager,dc=example,dc=com"
rootpw          {SSHA}GtG8bcLGeN/rf1iStKFK2pu0C2EZf/RX
loglevel        256
sizelimit       unlimited
# Cleartext passwords, especially for the rootdn, should
# be avoided.  See slappasswd(8) and slapd.conf(5) for details.
# Use of strong authentication encouraged.
# rootpw                secret
# rootpw                {crypt}ijFYNcSNctBYg

# The database directory MUST exist prior to running slapd AND
# should only be accessible by the slapd and slap tools.
# Mode 700 recommended.
directory       /var/lib/ldap

# Indices to maintain for this database
index objectClass                       eq,pres
index ou,cn,mail,surname,givenname      eq,pres,sub
index uidNumber,gidNumber,loginShell    eq,pres
index uid,memberUid                     eq,pres,sub
index nisMapName,nisMapEntry            eq,pres,sub

# Replicas of this database
#replogfile /var/lib/ldap/openldap-master-replog
#replica host=ldap-1.example.com:389 starttls=critical
#     bindmethod=sasl saslmech=GSSAPI
#     authcId=host/ldap-master.example.com@EXAMPLE.COM 

Clean up all content and previous existing LDAP configuration and files, incase if exists. And re-initialize them.
[root@ldap1 ~]# rm -rf /var/lib/ldap/*
[root@ldap1 ~]# rm -rf /etc/openldap/slapd.d/*

Copy the sample DB_CONFIG file to /var/lib/ldap/
[root@ldap1 ~]# cp /usr/share/openldap-servers/DB_CONFIG.example /var/lib/ldap/DB_CONFIG

Check for errors in /etc/openldap/slapd.conf using the below command 
[root@ldap1 ~]# slaptest -u
config file testing succeeded

Convert configuration file into dynamic configuration under /etc/openldap/slapd.d/ directory
[root@ldap1 ~]# slaptest -f /etc/openldap/slapd.conf -F /etc/openldap/slapd.d
config file testing succeeded

Set permission on /var/lib/ldap/ and /etc/openldap/slapd.d/ to ldap
[root@ldap1 ~]# chown -Rf ldap. /etc/openldap/slapd.d/
[root@ldap1 ~]# chown -Rf ldap. /var/lib/ldap/
[root@ldap1 ~]# chmod 700 /var/lib/ldap/
[root@ldap1 ~]# chmod 700 /etc/openldap/slapd.d/

Start the slapd process and service at system bootup 
[root@ldap1 ~]# service slapd start
Starting slapd:                                            [  OK  ]
[root@ldap1 ~]# chkconfig slapd on
  
Confirm the slapd process is running using the below commands
[root@ldap1 ~]# service slapd status
slapd (pid  1301) is running...[root@ldap1 ~]# netstat -ntlup | grep slapd
tcp        0      0 0.0.0.0:389                 0.0.0.0:*                   LISTEN      1301/slapd
tcp        0      0 :::389                      :::*                        LISTEN      1301/slapd
[root@ldap1 ~]# ps -ef | grep slapd
ldap      1301     1  0 08:21 ?        00:00:00 /usr/sbin/slapd -h  ldap:/// ldapi:/// -u ldap
root      1318  1208  0 08:23 pts/1    00:00:00 grep slapd

If you the get the output as above it means, your slapd is running with any problem. All connections to the server from the client are in plain text without encryption. The problem here is if anybody on the network using a packet sniffing tool such as ethereal can view the data that is transmitted between server and client, so he can view all the sensitive information. To eradicate such problem we are going to use slapd with SASL/TLS connection. For this we will use self signed certificates

Enabling encrypted connection for slapd using self-signed certificates

Install the openssl package using yum
[root@ldap1 ~]# yum install openssl -y

Generate the keypair using the below command
[root@ldap1 ~]# openssl req -newkey rsa:1024 -x509 -nodes -out /etc/pki/tls/certs/ldap1_pubkey.pem -keyout /etc/pki/tls/certs/ldap1_privkey.pem -days 3650
Generating a 1024 bit RSA private key
....++++++
....++++++
writing new private key to '/etc/pki/tls/certs/ldap1_privkey.pem'
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [XX]:IN
State or Province Name (full name) []:Andhra Pradesh
Locality Name (eg, city) [Default City]:Hyderabad
Organization Name (eg, company) [Default Company Ltd]:Example Inc.,
Organizational Unit Name (eg, section) []:ITD
Common Name (eg, your name or your server's hostname) []:ldap1.example.com
Email Address []:root@ldap1.example.com

Set permission on the generated certificates to ldap
[root@ldap1 ~]# chown ldap. /etc/pki/tls/certs/ldap1_p*
[root@ldap1 ~]# ll /etc/pki/tls/certs/ldap1_p*
-rw-r--r-- 1 ldap ldap  912 Oct 27 08:40 /etc/pki/tls/certs/ldap1_privkey.pem
-rw-r--r-- 1 ldap ldap 1131 Oct 27 08:40 /etc/pki/tls/certs/ldap1_pubkey.pem

Change the setting for the certificate files in the following config file. It is highlighted with red colour font
[root@ldap1 ~]# vim /etc/openldap/slapd.d/cn\=config/olcDatabase\=\{0\}config.ldif
dn: olcDatabase={0}config
objectClass: olcDatabaseConfig
olcDatabase: {0}config
olcAccess: {0}to *  by dn.base="gidNumber=0+uidNumber=0,cn=peercred,cn=externa
 l,cn=auth" manage  by * none
olcAddContentAcl: TRUE
olcLastMod: TRUE
olcMaxDerefDepth: 15
olcReadOnly: FALSE
olcRootDN: cn=config
olcSyncUseSubentry: FALSE
olcTLSCertificateFile: /etc/pki/tls/certs/ldap1_pubkey.pem
olcTLSCertificateKeyFile: /etc/pki/tls/certs/ldap1_privkey.pem
olcMonitoring: FALSE
structuralObjectClass: olcDatabaseConfig
entryUUID: 4e47724a-d2fd-1032-8616-41f003d9fb12
creatorsName: cn=config
createTimestamp: 20131027024329Z
entryCSN: 20131027024329.230729Z#000000#000#000000
modifiersName: cn=config
modifyTimestamp: 20131027024329Z

Modify the setting for SLAPD as below in file /etc/sysconfig/ldap 
[root@ldap1 ~]# vim /etc/sysconfig/ldap
SLAPD_LDAP=no
SLAPD_LDAPI=no
SLAPD_LDAPS=yes

Restart the SLAPD process
[root@ldap1 ~]# service slapd restart
Stopping slapd:                                            [  OK  ]
Starting slapd:                                            [  OK  ] 

Check the service is running on LDAPS port or not
[root@ldap1 ~]# netstat -ntlup | grep slapd
tcp        0      0 0.0.0.0:389                 0.0.0.0:*                   LISTEN      1402/slapd
tcp        0      0 :::389                      :::*                        LISTEN      1402/slapd

Modify the iptables configuration to allow LDAP ports
[root@ldap1 ~]# iptables -I INPUT -p udp -s 192.168.124.0/24 --dport 389 -j ACCEPT
[root@ldap1 ~]# iptables -I INPUT -p tcp -s 192.168.124.0/24 --dport 389 -j ACCEPT
[root@ldap1 ~]# iptables -I INPUT -p udp -s 192.168.124.0/24 --dport 636 -j ACCEPT
[root@ldap1 ~]# iptables -I INPUT -p tcp -s 192.168.124.0/24 --dport 636 -j ACCEPT
[root@ldap1 ~]# service iptables save
iptables: Saving firewall rules to /etc/sysconfig/iptables:[  OK  ]

Create a base for the DIT (Directory Information Tree) using the following file.
[root@ldap1 ~]# vim dit.ldif
# Creates a base for DIT
dn: dc=example,dc=com
objectClass: top
objectClass: dcObject
objectclass: organization
o: Example Organization
dc: Example
description: Example Inc DIT

# Creates a Users OU (Organizational Unit)
dn: ou=Users,dc=example,dc=com
objectClass: organizationalUnit
ou: Users

# Creates a Groups OU
dn: ou=Groups,dc=example,dc=com
objectClass: organizationalUnit
ou: Groups

dn: ou=Admins,dc=example,dc=com
objectClass: organizationalUnit
ou: Admins

# Create a user student1 with some basic info
dn: uid=student1,ou=Users,dc=example,dc=com
uid: student1
cn: student1
sn: 1
objectClass: top
objectClass: posixAccount
objectClass: inetOrgPerson
loginShell: /bin/bash
homeDirectory: /home/student1
uidNumber: 15000
gidNumber: 10000
userPassword: {SSHA}CQG5KHc6b1ii+qopaVCsNa14v9+r14r5
mail: student1@example.com
gecos: Student1 User

# Create a user student2 with some basic info
dn: uid=student2,ou=Users,dc=example,dc=com
uid: student2
cn: student2
sn: 2
objectClass: top
objectClass: posixAccount
objectClass: inetOrgPerson
loginShell: /bin/bash
homeDirectory: /home/student2
uidNumber: 15001
gidNumber: 10000
userPassword: {SSHA}CQG5KHc6b1ii+qopaVCsNa14v9+r14r5
mail: student2@example.com
gecos: Student2 User

# Creates a ldapusers group under Groups OU
dn: cn=ldapusers,ou=Groups,dc=example,dc=com
objectClass: posixGroup
objectClass: top
cn: ldapusers
userPassword: {crypt}x
gidNumber: 10000
memberuid: uid=student1
memberuid: uid=student2

Change the /etc/openldap/ldap.conf file as below
[root@ldap1 ~]# vim /etc/openldap/ldap.conf
#
# LDAP Defaults
#
# See ldap.conf(5) for details
# This file should be world readable but not world writable.
#BASE   dc=example,dc=com
#URI    ldap://ldap.example.com ldap://ldap-master.example.com:666

#SIZELIMIT      12
#TIMELIMIT      15
#DEREF          never

#TLS_CACERTDIR  /etc/openldap/certs
ssl             start_tls
TLS_REQCERT     allow
BASE            dc=example,dc=com
URI             ldaps://ldap.example.com
HOST            192.168.124.251

Populate the DIT with the values in the file dit.ldif
[root@ldap1 ~]# ldapadd -x -D "cn=Manager,dc=example,dc=com" -W -f dit.ldif -H ldaps://ldap1.example.comEnter LDAP Password:
adding new entry "dc=example,dc=com"

adding new entry "ou=Users,dc=example,dc=com"

adding new entry "ou=Groups,dc=example,dc=com"

adding new entry "uid=student1,ou=Users,dc=example,dc=com"

adding new entry "uid=student2,ou=Users,dc=example,dc=com"

adding new entry "cn=ldapusers,ou=Groups,dc=example,dc=com"

Search the DIT using the following command to find the newly added values
[root@ldap1 ~]# ldapsearch -x -b "dc=example,dc=com" -H ldaps://ldap1.example.com
# extended LDIF
#
# LDAPv3
# base <dc=example,dc=com> with scope subtree
# filter: (objectclass=*)
# requesting: ALL
#

# example.com
dn: dc=example,dc=com
objectClass: top
objectClass: dcObject
objectClass: organization
o: Example Organization
dc: Example
description: Example Inc DIT

# Users, example.com
dn: ou=Users,dc=example,dc=com
objectClass: organizationalUnit
ou: Users

# Groups, example.com
dn: ou=Groups,dc=example,dc=com
objectClass: organizationalUnit
ou: Groups

# student1, Users, example.com
dn: uid=student1,ou=Users,dc=example,dc=com
uid: student1
cn: student1
sn: 1
objectClass: top
objectClass: posixAccount
objectClass: inetOrgPerson
loginShell: /bin/bash
homeDirectory: /home/student1
uidNumber: 14583100
gidNumber: 14564100
userPassword:: e1NTSEF9Q1FHNUtIYzZiMWlpK3FvcGFWQ3NOYTE0djkrcjE0cjU=
mail: student1@example.com
gecos: Student1 User

# student2, Users, example.com
dn: uid=student2,ou=Users,dc=example,dc=com
uid: student2
cn: student2
sn: 2
objectClass: top
objectClass: posixAccount
objectClass: inetOrgPerson
loginShell: /bin/bash
homeDirectory: /home/student2
uidNumber: 14583101
gidNumber: 14564100
userPassword:: e1NTSEF9Q1FHNUtIYzZiMWlpK3FvcGFWQ3NOYTE0djkrcjE0cjU=
mail: student2@example.com
gecos: Student2 User

# ldapusers, Groups, example.com
dn: cn=ldapusers,ou=Groups,dc=example,dc=com
objectClass: posixGroup
objectClass: top
cn: ldapusers
userPassword:: e2NyeXB0fXg=
gidNumber: 14564100
memberUid: uid=student1
memberUid: uid=student2

# search result
search: 2
result: 0 Success

# numResponses: 8
# numEntries:7

Configure Rsyslog to log the LDAP to LOCAL4
[root@ldap1 ~]# vim /etc/rsyslog.conf
# At the end of file write the below
local4.*                        /var/log/ldap
[root@ldap1 ~]# service rsyslog restart

Now all LDAP log will be in the file  /var/log/ldap

Client Side Configuration

Configure the client to allow LDAP users to log into the system 
[root@client ~]# yum install openldap-clients sssd -y
[root@client ~]# vim /etc/openldap/ldap.conf
ssl     start_tls
TLS_REQCERT    allow
TLS_CACERTDIR /etc/openldap/cacerts
BASE    dc=example,dc=com
URI     ldaps://ldap1.example.com
HOST    192.168.124.251

Copy the LDAP public certificate into the client system at /etc/openldap/cacerts
[root@client ~]# scp ldap:/etc/pki/tls/certs/ldap.pem /etc/openldap/cacerts

Create a sssd.conf file at this location /etc/sssd/sssd.conf
[root@client ~]# vim /etc/sssd/sssd.conf
[sssd]
config_file_version = 2
services = nss, pam
domains = default

[nss]
filter_users = root,ldap,named,avahi,haldaemon,dbus,radiusd,news,nscd

[pam]

[domain/default]
ldap_tls_reqcert = never
auth_provider = ldap
ldap_schema = rfc2307bis
krb5_realm = EXAMPLE.COM
ldap_search_base = dc=example,dc=com
ldap_group_member = uniquemember
id_provider = ldap
ldap_id_use_start_tls = True
chpass_provider = ldap
ldap_uri = ldaps://ldap1.example.com/
ldap_chpass_uri = ldaps://.ldap1.example.com/
krb5_kdcip = ldap1.example.com
cache_credentials = True
ldap_tls_cacertdir = /etc/openldap/cacerts
entry_cache_timeout = 600
ldap_network_timeout = 3
krb5_server = ldap1.example.com

Configure the System to use LDAP authentication 
[root@client ~]# authconfig-tui
  
Click Next
  
Click OK
Starting sssd:                                             [  OK  ]
[root@client ~]# authconfig --enablesssd --enablesssdauth --enablelocauthorize --enablemkhomedir --update
[root@client ~]# getent passwd student1
student1:*:15000:10000:Student1 User:/home/student1:/bin/bash
[root@client ~]# id student1
uid=15000(student1) gid=10000(ldapusers) groups=10000(ldapusers)

 Now login to the system with any LDAP user
[root@client ~]# su - student1
Creating directory '/home/student1'.
[student1@client ~]$ pwd
/home/student1

Troubleshooting: 
Incase you get error as below:
bdb_db_open: database "dc=example,dc=com": db_open(/var/lib/ldap/id2entry.bdb) failed: No such file or directory (2).

Then initialize DB files for content in /var/lib/ldap directory
[root@ldap1 ~]# echo "" | slapadd -f /etc/openldap/slapd.conf 
After this again run the command
[root@ldap1 ~]# slaptest -f /etc/openldap/slapd.conf -F /etc/openldap/slapd.d

Multi-Master Replication Of OpenLDAP Server on CentOS 6.4

In this post I will try to explain how to configure multi-master replication of OpenLDAP Server on CentOS 6.4

In my previous post, I have shown you how to configure OpenLDAP Server with SASL/TLS.

If you dont know how to configure, please visit this link 

http://linuxadminforu.blogspot.in/2014/06/installing-configuring-openldap-server.html

Some important point about multi-master replication: 

• In previous releases of OpenLDAP, replication was discussed in terms of a master server and some slave servers.
• In OpenLDAP version 2.4.x, it support multi-master replication model.
• The LDAP Sync Replication engine, syncrepl for short, is a consumer-side replication engine that enables the consumer LDAP server to maintain a shadow copy of a DIT.
• A provider replicates directory updates to consumers. 
• Consumers receive replication updates from providers.
• In simple, layman terms, Provider means Master, Consumer means Slave.
• In multi-master all providers acts as consumers.
• In multi-master replication, syncrepl supports two synchronization operations, i.e. refreshOnly and refreshAndPersist.
• In refreshOnly mode synchronization, the provider uses a pull-based synchronization where the consumer servers need not be tracked and no history information is maintained.
• In refreshAndPersist mode of synchronization, the provider uses a push-based synchronization. The provider keeps track of the consumer servers that have requested the persistent search and sends them necessary updates as the provider replication content gets modified.

1) Copy the LDAP1 server public key file to the LDAP2 server and LDAP2 server public key file to LDAP1 server in this location /etc/openldap/certs
[root@ldap1 ~]# scp ldap2:/etc/pki/tls/certs/ldap2pub.pem  /etc/openldap/certs/
[root@ldap1 ~]# scp /etc/pki/tls/certs/ldap1pub.pem ldap2:/etc/openldap/certs/

2) Set the permissions on the copied public key files to ldap on LDAP1 and LDAP2 Servers
[root@ldap1 ~]# chown ldap. /etc/openldap/certs/ldap2pub.pem
[root@ldap2 ~]# chown ldap. /etc/openldap/certs/ldap1pub.pem

3) Configure /etc/openldap.slapd.conf as below on both LDAP1 and LDAP2 Servers
[root@ldap1 ~]# vim /etc/openldap/slapd.conf
#
# See slapd.conf(5) for details on configuration options.
# This file should NOT be world readable.
#

include         /etc/openldap/schema/corba.schema
include         /etc/openldap/schema/core.schema
include         /etc/openldap/schema/cosine.schema
include         /etc/openldap/schema/duaconf.schema
include         /etc/openldap/schema/dyngroup.schema
include         /etc/openldap/schema/inetorgperson.schema
include         /etc/openldap/schema/java.schema
include         /etc/openldap/schema/misc.schema
include         /etc/openldap/schema/nis.schema
include         /etc/openldap/schema/openldap.schema
include         /etc/openldap/schema/ppolicy.schema
include         /etc/openldap/schema/collective.schema

# Allow LDAPv2 client connections.  This is NOT the default.
allow bind_v2

# Do not enable referrals until AFTER you have a working directory
# service AND an understanding of referrals.
#referral       ldap://root.openldap.org

pidfile         /var/run/openldap/slapd.pid
argsfile        /var/run/openldap/slapd.args

# Load dynamic backend modules
# - modulepath is architecture dependent value (32/64-bit system)
# - back_sql.la overlay requires openldap-server-sql package
# - dyngroup.la and dynlist.la cannot be used at the same time

# modulepath /usr/lib/openldap
# modulepath /usr/lib64/openldap

# moduleload accesslog.la
# moduleload auditlog.la
# moduleload back_sql.la
# moduleload chain.la
# moduleload collect.la
# moduleload constraint.la
# moduleload dds.la
# moduleload deref.la
# moduleload dyngroup.la
# moduleload dynlist.la
# moduleload memberof.la
# moduleload pbind.la
# moduleload pcache.la
# moduleload ppolicy.la
# moduleload refint.la
# moduleload retcode.la
# moduleload rwm.la
# moduleload seqmod.la
# moduleload smbk5pwd.la
# moduleload sssvlv.la
moduleload syncprov.la
# moduleload translucent.la
# moduleload unique.la
# moduleload valsort.la

# The next three lines allow use of TLS for encrypting connections using a
# dummy test certificate which you can generate by running
# /usr/libexec/openldap/generate-server-cert.sh. Your client software may balk
# at self-signed certificates, however.
#TLSCACertificatePath /etc/openldap/certs
#TLSCertificateFile "\"OpenLDAP Server\""
#TLSCertificateKeyFile /etc/openldap/certs/password
TLSCertificateFile "/etc/pki/tls/certs/ldap1pub.pem"
TLSCertificateKeyFile "/etc/pki/tls/certs/ldap1key.pem"

# Sample security restrictions
#       Require integrity protection (prevent hijacking)
#       Require 112-bit (3DES or better) encryption for updates
#       Require 63-bit encryption for simple bind
# security ssf=1 update_ssf=112 simple_bind=64

# Sample access control policy:
#       Root DSE: allow anyone to read it
#       Subschema (sub)entry DSE: allow anyone to read it
#       Other DSEs:
#               Allow self write access
#               Allow authenticated users read access
#               Allow anonymous users to authenticate
#       Directives needed to implement policy:
# access to dn.base="" by * read
# access to dn.base="cn=Subschema" by * read
# access to *
#       by self write
#       by users read
#       by anonymous auth
#
# if no access controls are present, the default policy
# allows anyone and everyone to read anything but restricts
# updates to rootdn.  (e.g., "access to * by * read")
#
# rootdn can always read and write EVERYTHING!

# enable on-the-fly configuration (cn=config)
database config
access to *
        by dn.exact="gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth" manage
        by * none

# enable server status monitoring (cn=monitor)
database monitor
access to *
        by dn.exact="gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth" read
        by dn.exact="cn=Manager,dc=example,dc=com" read
        by * none

#######################################################################
# database definitions
#######################################################################

database        bdb
suffix          "dc=example,dc=com"
checkpoint      1024 15
rootdn          "cn=Manager,dc=example,dc=com"
rootpw          {SSHA}5h1vaYgy7fOLash39ZFKLQ3TOzqNYk/g
loglevel        256
sizelimit       unlimited
# Cleartext passwords, especially for the rootdn, should
# be avoided.  See slappasswd(8) and slapd.conf(5) for details.
# Use of strong authentication encouraged.
# rootpw                secret
# rootpw                {crypt}ijFYNcSNctBYg

# The database directory MUST exist prior to running slapd AND
# should only be accessible by the slapd and slap tools.
# Mode 700 recommended.
directory       /var/lib/ldap

# Indices to maintain for this database
index objectClass                       eq,pres
index ou,cn,mail,surname,givenname      eq,pres,sub
index uidNumber,gidNumber,loginShell    eq,pres
index uid,memberUid                     eq,pres,sub
index nisMapName,nisMapEntry            eq,pres,sub

# Replicas of this database
#replogfile /var/lib/ldap/openldap-master-replog
#replica host=ldap-1.example.com:389 starttls=critical
#     bindmethod=sasl saslmech=GSSAPI
#     authcId=host/ldap-master.example.com@EXAMPLE.COM

# Multi master replication
ServerID        1 "ldaps://ldap1.example.com"
ServerID        2 "ldaps://ldap2.example.com"
overlay         syncprov
syncprov-checkpoint     10 1
syncprov-sessionlog     100
syncrepl        rid=1
                provider="ldaps://ldap1.example.com"
                type=refreshAndPersist
                interval=00:00:00:10
                retry="5 10 60 +" 
                timeout=1
                schemachecking=off
                searchbase="dc=example,dc=com"
                scope=sub 
                bindmethod=simple
                tls_cacert=/etc/pki/tls/certs/ldap1pub.pem
                binddn="cn=Manager,dc=example,dc=com"
                credentials="redhat"
syncrepl        rid=2
                provider="ldaps://ldap2.example.com"
                type=refreshAndPersist
                interval=00:00:00:10
                retry="5 10 60 +"  
                timeout=1 
                schemachecking=off
                scope=sub 

                searchbase="dc=example,dc=com"
                bindmethod=simple
                tls_cacert=/etc/openldap/certs/ldap2pub.pem
                binddn="cn=Manager,dc=example,dc=com"
                credentials="redhat"
MirrorMode      on
 
4) Convert the slapd.conf to cn=config format and re-initialize the slapd.d folder 
on LDAP1 and LDAP2 Servers
[root@ldap1 ~]# rm -rf /etc/openldap/slapd.d/* 
[root@ldap1 ~]# slaptest -u 
[root@ldap1 ~]# slaptest -f /etc/openldap/slapd.conf -F /etc/openldap/slapd.d/ 

5) Change the permissions on the /etc/openldap/slapd.d/ to ldap on LDAP1 and LDAP2 Servers
[root@ldap1 ~]# chown -R ldap. /etc/openldap/slapd.d/

6) Restart the slapd service on LDAP1 and LDAP2 Servers
[root@ldap1 ~]# service slapd restart

7) Check whether replication is working or not by adding an entry into DIT on both servers, the entry should be visible by ldapsearch on both server if it is added on anyone of them. 

8) If there is any problem in replication check the log file /var/log/ldap for more information and troubleshooting.

Configuration terms used in /etc/openldap/slapd.conf for replication

• rid -> replica ID for servers, which should be numeric and unique for each server
• provider -> URI of ldap server which will be the master server
• type -> type of synchronization between LDAP servers for replication
• interval -> time interval for initial synchronization process i.e. 10 secs here
• retry -> retry the synchronization process if incase consumer is not available i.e. retry 10 times every 5 seconds, if it fails and then every 60 sec it will continue
• timeout -> timeout incase of failure in retry i.e. 1 sec
• schemachecking -> off means will not check for schema during schema
• searchbase -> search base that will be replicated to the other server
• scope -> sub means all the sub DNs will be replicated
• bindmethod -> connection type for replication process
• binddn -> the user authorized for replication process
• credentials -> user password for the user initiating the replication process

Implementing Password Policies in OpenLDAP Server On CentOS 6.4

In this post I am going to show you how to configure password policies in OpenLDAP server. The ppolicy overlay module provides some better functionalities for enforcing password policies within our OpenLDAP Server domain.

ppolicy module and schema is by installed by default with openldap-servers package in CentOS 6.4

Copy the below text into /etc/openldap/slapd.conf at the end of the file 
[root@ldap1 ~]# vim /etc/openldap/slapd.conf
# Uncomment the module in the modules section
moduleload ppolicy.la  
# Password Policy Configuration
overlay ppolicy
ppolicy_default "cn=default,ou=Policies,dc=example,dc=com"
ppolicy_use_lockout
ppolicy_hash_cleartext

# ACL Entry for Password Policies
access to attrs=userPassword
        by self write
        by anonymous auth
        by * none
access to *
        by self write
        by * read

Convert the slapd.conf to cn=config format and re-initialize the slapd.d folder
[root@ldap1 ~]# rm -rf /etc/openldap/slapd.d/* 
[root@ldap1 ~]# slaptest -u 
[root@ldap1 ~]# slaptest -f /etc/openldap/slapd.conf -F /etc/openldap/slapd.d/

Change the permissions on the /etc/openldap/slapd.d/ to ldap
[root@ldap1 ~]# chown -R ldap. /etc/openldap/slapd.d/  

Restart the slapd service
[root@ldap1 ~]# service slapd restart 

Create a LDIF file with the details as below
[root@ldap1 ~]# vim pwdpolicy.ldif
# Creates a Policies OU (Organizational Unit)
dn: ou=Policies,dc=example,dc=com
objectClass: organizationalUnit
ou: Policies

# Creates a Policy object in Policies OU (Organizational Unit)
dn: cn=default,ou=Policies,dc=example,dc=com
objectClass: top
objectClass: device
objectClass: pwdPolicy
cn: default
pwdAttribute: userPassword
pwdMaxAge: 3888000
pwdExpireWarning: 604800
pwdInHistory: 3
pwdCheckQuality: 1
pwdMinLength: 8
pwdMaxFailure: 5
pwdLockout: TRUE
pwdLockoutDuration: 86400
pwdGraceAuthNLimit: 0
pwdFailureCountInterval: 0
pwdMustChange: TRUE
pwdAllowUserChange: TRUE
pwdSafeModify: FALSE 

Add the ldif file created to the DIT using ldapadd command
[root@ldap1 ~]# ldapadd -x -D "cn=manager,dc=example,dc=com" -wredhat -f pwdpolicy.ldif

Password policy is turned on for all accounts
 
The above definition of password policy as below
pwdMaxAge: Number of days users password is valid for i.e 3888000 seconds (45 days)
pwdExpireWarning: No. of days before to warn the user (7 days)
pwdInHistory: No. of password that are kept in history which can't be used continously
pwdCheckQuality: If it is 0, we can use plain passwords, if it is 1 then password should be complex i.e. combination of numbers and alpahbets and special characters
pwdMinLength: Defines the minimum number of characters for setting the password. It can't be less than 8 characters here
pwdMaxFailure: If user tries to enter incorrect password for 5 times then his/her account will be locked
pwdLockoutDuration: Defines the time the account will be locked ie. 1 day. This setting will be valid only if pwdLockout is set to TRUE

For more information and settings on password policy please refer to this link below
http://www.zytrax.com/books/ldap/ch6/ppolicy.html

Monitor & Record all Shell Commands & Send Logs to Centralized RSyslog Server

In this post I will show how to record all the users activity i.e. shell commands that are executed and will send that logs to the centralized log server.

In this demo I have a couple of CentOS 6.3 x86_64 machines with minimal installation.

1) Rsyslog is installed by default on CentOS machines, incase its not installed, install the Rsyslog package on both Client and Server.
[root@server ~]# yum install rsyslog -y
[root@client ~]# yum install rsyslog -y 
 
2) Edit the /etc/bashrc to record the shell commands that are executed
[root@client ~]# vim /etc/bashrc
Add this line to the end of file
remoteip=$(who am i | awk '{print $5}' | sed "s/[()]//g" )
export PROMPT_COMMAND='RETRN_VAL=$?;logger -p local3.debug "$(whoami)  $remoteip  [$$]: $(history 1 | sed "s/^[ ]*[0-9]\+[ ]*//" ) [$RETRN_VAL]"' 

3) Configure the Rsyslog server to capture the local3 to a log file
[root@client ~]# vim /etc/rsyslog.conf
local3.*                /var/log/user-activity.log

4) Restart the Rsyslog server
[root@client ~]# service rsyslog restart

5) Log off and log back in to check the result in the file /var/log/user-activity.log
[root@client ~]# cat /var/log/user-activity.log
Oct  7 00:18:20 ad root: root  192.168.124.1   [4927]: service postfix stautus [2]
Oct  7 00:18:25 ad root: root  192.168.124.1   [4927]: service postfix status [0]
Oct  7 00:19:10 ad root: root  192.168.124.1  [4991]: exit [0]
Oct  7 00:19:16 ad root: root  192.168.124.1  [4991]: service postfix status [0]
Oct  7 00:19:23 ad root: root  192.168.124.1  [4991]: service sendmail status [1]
Oct  7 00:20:05 ad root: root  192.168.124.1  [4991]: date [0]
Oct  7 00:20:06 ad root: root  192.168.124.1  [4991]: pwd [0]
Oct  7 00:20:10 ad root: root  192.168.124.1  [4991]: history  [0]
Oct  7 00:20:15 ad root: root  192.168.124.1  [4991]: service named status [0]
Oct  7 00:20:21 ad root: root  192.168.124.1  [4991]: service named restart [0]
Oct  7 00:20:49 ad root: root  192.168.124.1  [4991]: cp -v /home/ahmed/* /root [0]
Oct  7 00:21:03 ad root: root  192.168.124.1  [4991]: ll [0]
Oct  7 00:21:16 ad root: root  192.168.124.1  [4991]: cat su [0]
Oct  7 00:21:31 ad root: ahmed  192.168.124.1  [5135]: exit [0]
Oct  7 00:21:32 ad root: ahmed  192.168.124.1  [5135]: redhat [127]
Oct  7 00:21:35 ad root: ahmed  192.168.124.1  [5135]: who am i [0]
Oct  7 00:21:38 ad root: ahmed  192.168.124.1  [5135]: ls [0]
Oct  7 00:21:46 ad root: ahmed  192.168.124.1  [5135]: rm * [0]
Oct  7 00:21:49 ad root: root  192.168.124.1  [4991]: su - ahmed [0]

6) To Centralize the logs do the following on the centralized Rsyslog server
[root@server ~]# vim /etc/rsyslog.conf
Uncomment the below lines
$ModLoad imudp
$UDPServerRun 514

$ModLoad imtcp
$InputTCPServerRun 514

[root@server ~]# vim /etc/rsyslog.d/remotesrv.conf
if $hostname contains 'client' then /var/log/servers/client.log
if $hostname contains 'client' then ~

7) Restart the server and configure iptables to accept the rsyslog connections
[root@server ~]# service rsyslog restart
[root@server ~]# iptables -A INPUT -m state --state NEW -m tcp -p tcp --dport 514 -j ACCEPT
[root@server ~]# iptables -A INPUT -m state --state NEW -m udp -p udp --dport 514 -j ACCEPT
[root@server ~]# service iptables save

8) On Client Side configure the following
[root@client ~]# vim /etc/rsyslog.conf
$ModLoad imudp
$UDPServerRun 514
$AllowedSender UDP, 127.0.0.1, 192.168.124.0/24

$ModLoad imtcp
$InputTCPServerRun 514
$AllowedSender TCP, 127.0.0.1, 192.168.124.0/24

local3.*        @@192.168.124.250:514

9) Restart the Rsyslog service on the client side as well
[root@client ~]# service rsyslog restart

10) Logoff and Log back in and run some commands that will be recorded on the server at the defined location here it is /var/log/servers/clients.log

Deploying Operating Systems Using Cobbler - PXE Boot

Cobbler is a Linux installation server that allows for rapid setup of network installation environments. It glues together and automates many associated Linux tasks so you do not have to hop between many various commands and applications when deploying new systems, and, in some cases, changing existing ones. Cobbler can help with provisioning, managing DNS and DHCP, package updates, power management, configuration management orchestration, and much more.

Here in my example, my machine name is cobbler and its IP is 192.168.75.222 and its running CentOS 6.5 x86_64 version 

1) For simplicity and testing purposes, disable SELinux
[root@cobbler ~]# vim /etc/sysconfig/selinux
selinux=disabled

2) Reboot your system after applying SELinux Changes

3) Install the EPEL Repo for Cobbler Packages
[root@cobbler ~]# rpm -ivh http://epel.mirror.net.in/epel/6/i386/epel-release-6-8.noarch.rpm

4) Install the following packages
[root@cobbler ~]# yum install dhcp cobbler pykickstart mod_python tftp -y

5) Enable xinetd tftp and rsync services
[root@cobbler ~]# vim /etc/xinetd.d/tftp
disable = no                    <- Change this line to "no"

[root@cobbler ~]# vim /etc/xinetd.d/rsync
disable = no                    <- Change this line to "no"

6) Start the xinetd, httpd, cobbler services and start the necessary at boot time
[root@cobbler ~]# for i in xinetd httpd cobblerd; do service $i restart; chkconfig $i on; done;
[root@cobbler ~]# chkconfig tftp on 
[root@cobbler ~]# chkconfig rsync on

7) Download the network boot-loaders for cobbler
[root@cobbler ~]# cobbler get-loaders

8) Change the default template of the dhcp file included with cobbler to match your network
[root@cobbler ~]# cp /etc/cobbler/dhcp.template /etc/cobbler/dhcp.template.org
[root@cobbler ~]# vim /etc/cobbler/dhcp.template
allow booting;
allow bootp;
ignore client-updates;
set vendorclass = option vendor-class-identifier;
option pxe-system-type code 93 = unsigned integer 16;
subnet 192.168.75.0 netmask 255.255.255.0 {
     option routers             192.168.75.1;
     option subnet-mask         255.255.255.0;
     range dynamic-bootp        192.168.75.100 192.168.75.254;
     default-lease-time         21600;
     max-lease-time             43200;
     next-server                192.168.75.222;
     class "pxeclients" {
          match if substring (option vendor-class-identifier, 0, 9) = "PXEClient";
          if option pxe-system-type = 00:02 {
                  filename "ia64/elilo.efi";
          } else if option pxe-system-type = 00:06 {
                  filename "grub/grub-x86.efi";
          } else if option pxe-system-type = 00:07 {
                  filename "grub/grub-x86_64.efi";
          } else {
                  filename "pxelinux.0";
          }
     }

9) Change the cobbler setting file according to the below
[root@cobbler ~]# vim /etc/cobbler/settings
manage_dhcp: 1
next_server: 192.168.75.222
server: 192.168.75.222

10) Mount your CentOS 6.5 DVD to a mount point, here I am mounting on /mnt
[root@cobbler ~]# mount /dev/sr0 /mnt

11) Import the Distro details into cobbler using the below command (It takes time to copy the distro data into /var/www/cobbler/. So be patient)
[root@cobbler ~]# cobbler import --path=/mnt --name=CentOS_6.5_x86_64

12) Copy the default anaconda-ks.cfg to the default location of cobbler kickstart files
[root@cobbler ~]# cp anaconda-ks.cfg /var/lib/cobbler/kickstarts/centos65.ks

13) Modify the centos65.ks file to the following or according to your requirement
[root@cobbler ~]# vim /var/lib/cobbler/kickstarts/centos65.ks
install
url --url http://192.168.75.222/cobbler/ks_mirror/CentOS_6.5_x86_64/
lang en_US.UTF-8
zerombr
keyboard us
network --onboot yes --device eth0 --bootproto dhcp --noipv6
rootpw  --iscrypted $6$4t6CgzQlwQKVFUEb$.mWJx35kMLobSabwpoKzlVpTvmTjxapy5GjSJdWkWANgV9J0SE4tm/oYMQjOYFdAyp5FgpevxXmzyy5/3xcHS.
firewall --service=ssh
authconfig --enableshadow --passalgo=sha512
selinux --enforcing
timezone Asia/Kolkata
bootloader --location=mbr --driveorder=sda --append="crashkernel=auto rhgb quiet"

clearpart --linux --drives=sda
repo --name="CentOS"  --baseurl=cdrom:sr0 --cost=100
%packages --nobase
@core
%end

14) Add the distro information to the cobbler for PXE Boot
[root@cobbler ~]# cobbler distro add --name=CentOS_6.5_x86_64 --kernel=/var/www/cobbler/ks_mirror/CentOS_6.5_x86_64/isolinux/vmlinuz --initrd=/var/www/cobbler/ks_mirror/CentOS_6.5_x86_64/isolinux/initrd.img 

15) Add the kickstart profile to the distro
[root@cobbler ~]# cobbler profile add --name=CentOS_6.5_KS --distro=CentOS_6.5_x86_64 --kickstart=/var/lib/cobbler/kickstarts/centos65.ks 

16) Restart and synchronize the changes that were made into cobbler
[root@cobbler ~]# service cobblerd restart 
[root@cobbler ~]# cobbler sync

17) Configure the firewall to allow ports 80 (HTTP) and 69 (TFTP) 
[root@cobbler ~]# iptables -I INPUT -p tcp -s 192.168.75.0/24 -d 192.168.75.222 --dport 80 -j ACCEPT
[root@cobbler ~]# iptables -I INPUT -p udp -s 192.168.75.0/24 -d 192.168.75.222 --dport 69 -j ACCEPT
[root@cobbler ~]# service iptables save

18) Restart the below services once again to make sure all the changes are applied to the services 
[root@cobbler ~]# for i in xinetd httpd cobblerd; do service $i restart; chkconfig $i on; done;

19) Boot a new linux machine and make sure it boots via Network and at the menu prompt select the CentOS_6.5_KS option


 

HOWTO: backup a mysql db on the command line

To backup a single mysql database, use the following command:

:~$ mysqldump -u my_user_name -p db_name > backup_of_my_db.sql

If compression is needed, the command changes like this:

:~$ mysqldump -u my_user_name -p db_name  | gzip -9 > backup_of_my_db.sql.gz

To extract the compressed .gz file, use the following gunzip command:

:~$ gunzip backup_of_my_db.sql.gz

HOWTO: killing a TTY session using the command line

HOWTO: killing a TTY session using the command line

Recently one of my PuTTY sessions froze, and I decided to try and kill it using the command line, instead of simply closing the window.

This is the complete procedure:
I opened another PuTTY session
using the who command I found the name of the frozen TTY

myuser@ubuntu:~$ w
14:21:07 up 119 days, 12 min, 2 users, load average: 0.06, 0.05, 0.05
USER  TTY   FROM        LOGIN@ IDLE  JCPU  PCPU  WHAT
user1 pts/0 192.168.x.x 13:02  1:36  1.81s 0.10s sshd: user1 [priv]
user1 pts/2 192.168.x.x 14:21  0.00s 0.46s 0.00s w
myuser@ubuntu:~$

using ps and grep i found its PID
ps -u root | grep -i pts/0
finally, I killed the blocked session:

kill -9