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Red Hat Linux Active Directory Integration


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Red Hat Linux Active Directory Integration

Can Linux boxes exist in a Windows Active Directory domain? The answer has been yes for a long time. However until very recently this has been a very painful and tedious process. Exporting certifications, trial and error config files, changing security settings on domain controller, a major headache.

Thankfully RedHat has actually realized this was a problem. It’s funny that while Server 2012 is already released RedHat just not added a simple method to integrate authentication with a Windows Active Directory domain.

Windows-Server-2008-R2_ad_authentication

We are a release behind, better now than ever.

redhat_ad_authentication_sssd-300x97.png

The real OS of choice.

NOTE: All Sample Configs are located at the bottom of this page.

To start this article ONLY applied to:

  • Red Hat Enterprise Linux 6.4

CENTOS 6.4

You can find out your verion by using

cat /etc/system-release (CENTOS)cat/etc/redhat-release (Red Hat)

If you are not familiar with SSSD(System Security Services Daemon) then I suggest you do some reading before you dive into this article. Also this is more gear towards Linux admins and not Windows admins. With these new changes you won’t have access your windows admin for anything, well unless you need that domain admin access of course.

BEFORE WE DO ANYTHING ALWAYS BACKUP YOUR CONFIGS

authconfig --savebackup=mybackup

First to get started let’s check what version of SSSD you have installed on your box.

NOTE: If a domain name is in CAPS it is on purpose. This was not done for show.

rpm -q sssd

You will need at least SSSD 1.9.2 for this.

Let’s go ahead and setup all of the nessesary nss and pam config files.


authconfig --enablesssd --ldapserver=ldap://dc1.youdomain.com --ldapbasedn="dc=YOURDOMAIN,dc=COM" --enablerfc2307bis --enablesssdauth --krb5kdc=dc1.youdomain.com --krb5realm=YOURDOMAIN.COM --disableforcelegacy --enablelocauthorize --enablemkhomedir --updateallvi /etc/krb5.conf[logging]

default = FILE:/var/log/krb5libs.log

kdc = FILE:/var/log/krb5kdc.log

admin_server = FILE:/var/log/kadmind.log[libdefaults]

default_realm = YOURDOMAIN.COM

dns_lookup_realm = false

dns_lookup_kdc = false

ticket_lifetime = 24h

renew_lifetime = 7d

forwardable = true#These encryption types are required for ntvlmi and krb5i(packet signing)default_tgs_enctypes = rc4-hmac aes256-cts-hmac-sha1-96 aes128-cts-hmac-sha1-96default_tkt_enctypes = rc4-hmac aes256-cts-hmac-sha1-96 aes128-cts-hmac-sha1-96permitted_enctypes = rc4-hmac aes256-cts-hmac-sha1-96 aes128-cts-hmac-sha1-96

[realms]

YOURDOMAIN.COM = {

kdc = domaincontroller.yourdomain.com:88

admin_server = domaincontroller.yourdomain.com:749

default_domain = yourdomain.com

}[domain_realm]

.yourdomain.com = YOURDOMAIN.COM

yourdomain.com = YOURDOMAIN.COM

Next


vi /etc/samba/smb.conf[global]

workgroup = YOURDOMAIN

client signing = yes

client use spnego = yes

kerberos method = secrets and keytab

log file = /var/log/samba/%m.log

realm = YOURDOMAIN.COM

security = adsvi /etc/sssd/sssd.conf[sssd]

config_file_version = 2

services = nss, pam

domains = YOURDOMAIN.COM[nss]

nss_filter_groups = root

nss_filter_users = root

nss_entry_cache_timeout = 30

nss_enum_cache_timeout = 30

[domain/YOURDOMAIN.COM]id_provider = ad

ad_server=domaincontroller.yourdomain.com

ad_domain=yourdomain.com

Now you will need a active directory account with administrator privledges to add a machines to the domain. Before you run kinit make sure you update your time with a domain controller.


ntpdate dc1.youdomain.com

Once Time is synced continue with..


kinit administrator

Type your password.

Confirm that you have received a kerberos ticket but using

klist

If you do not see any tickets please refer to your logs. SSSD is some what helpful inside /var/log/messages

Now we have a ticket we need to add this machine to the domain.


net ads join -k

If you receive a success message your new linux box should be inside active directory inside the default Computers Group. Verify with an Active Directory Admin to make sure your server object was created. Let’s run:


service sssd restart

If you did not receive any warning messages inside /var/log/messages we should be good to go.

Test by running


id yourusernamead

and


getent passwd yourusernamead

You should be able to look up accounts at this point.

Now the best part of this. Let’s setup Putty and SSHD to use your kerberos key to authenticate into your linux box. As you noted inside our sssd.conf we have added root accounts not to use AD authentication.

First let’s make some changes to our SSHD configs.


vi /etc/ssh/sshd_conf

Make sure you have this line un commented


GSSAPIAuthentication yesvi /etc/ssh/ssh_confGSSAPIAuthentication yes GSSAPIDelegateCredentials yes

Also before trying to use Putty make sure you have a newer release and make sure your authentication settings are setup as follows:

Putty_Config_AD_Linux.png

Make sure this is enabled.

Now open a new session to your linux box. Type in your active directory username and press enter. If kerberos negotiation is successful you will NOT be prompted for a password.

Happy Shelling

Sample Config Files

ssh_conf

sshd_conf

If you are a RedHat subscriber you can read their article on this subject here.

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