This documentation will explain how to use Active Directory as Kerberos server, and provide transparent authentication for one or multiple AD domains.
You can use Kerberos in LL::NG with the following authentication modules:
We will use the following values in our examples
It is mandatory that LL::NG servers and AD servers have the same time. It is recommended to use NTP to do this.
The auth.example.com must be registered in the DNS server (which is Active Directory). The reverse DNS of auth.example.com must return the portal IP.
SSL is not mandatory, but it is strongly recommended. Your portal URL should be https://auth.example.com.
Type about:config
in a tab and search for trusted
. Then edit the property network.negotiate-auth.trusted-uris
and set value example.com
.
Add https://auth.example.com
as trusted site.
Check into security parameters that Kerberos authentication is allowed.
On LL::NG server, edit /etc/krb5.conf
:
[libdefaults] default_realm = EXAMPLE.COM dns_lookup_kdc = false dns_lookup_realm = no ticket_lifetime = 24h forwardable = yes renewable = true [realms] EXAMPLE.COM = { kdc = ad.example.com admin_server = ad.example.com } [domain_realm] .example.com = EXAMPLE.COM example.com = EXAMPLE.COM
You can check that Kerberos is working by trying to get a ticket for a user of the domain (for example coudot):
kinit coudot@EXAMPLE.COM
You should be prompted to enter password. Then list the tickets:
klist -e
You should see a krbtgt ticket:
Valid starting Expires Service principal 06/04/15 15:43:24 06/05/15 01:43:29 krbtgt/EXAMPLE.COM@EXAMPLE.COM renew until 06/05/15 15:43:24, Etype (skey, tkt): aes256-cts-hmac-sha1-96, aes256-cts-hmac-sha1-96
You can then close the Kerberos session:
kdestroy
You have to run this command on Active Directory:
ktpass -princ HTTP/auth.example.com@EXAMPLE.COM -mapuser KERB_AUTH@EXAMPLE.COM -crypto DES-CBC-MD5 -ptype KRB5_NT_PRINCIPAL -mapOp set -pass <PASSWORD> -out c:\auth.keytab
The file auth.keytab
should then be copied (with a secure media) to the Linux server (for example in /etc/lemonldap-ng
).
Change rights on keytab file:
chown apache /etc/lemonldap-ng/auth.keytab chmod 600 /etc/lemonldap-ng/auth.keytab
You can check the validity of the keytab file by trying to request a service ticket, and compare the result with the keytab content.
Open a Kerberos session (like done in the previous step):
kinit coudot@example.com
Request a service ticket:
kvno HTTP/auth.example.com@EXAMPLE.COM
The result of the command should be:
HTTP/auth.example.com@EXAMPLE.COM: kvno = 3
Read the service ticket:
klist -e
You should see this kind of ticket:
06/04/15 16:28:49 06/05/15 02:28:11 HTTP/auth.example.com@EXAMPLE.COM renew until 06/05/15 16:28:07, Etype (skey, tkt): arcfour-hmac, arcfour-hmac
You can close the Kerberos session:
kdestroy
Now you can compare the above result with the same request done trough the keytab file:
klist -e -k -t /etc/lemonldap-ng/auth.keytab
The result of the command should be:
Keytab name: FILE:/etc/lemonldap-ng/auth.keytab KVNO Timestamp Principal ---- ----------------- -------------------------------------------------------- 3 01/01/70 01:00:00 HTTP/auth.example.com@EXAMPLE.COM (arcfour-hmac)
The important things to check are:
The two domains must be defined in /etc/krb5.conf
:
[libdefaults] default_realm = EXAMPLE.COM dns_lookup_kdc = false dns_lookup_realm = no ticket_lifetime = 24h forwardable = yes renewable = true [realms] EXAMPLE.COM = { kdc = ad.example.com admin_server = ad.example.com default_domain = EXAMPLE.COM } ACME.COM = { kdc = ad.acme.com admin_server = ad.acme.com } [domain_realm] .example.com = EXAMPLE.COM example.com = EXAMPLE.COM .acme.com = ACME.COM acme.com = ACME.COM
You should then be able to open a Kerberos session on each domain:
kinit coudot@EXAMPLE.COM klist -e kdestroy
kinit coudot@ACME.COM klist -e kdestroy
You need to obtain a keytab for each node on each domain. This means the ktpass commands should be run on both AD.
Then you will have 2 keytab files for each node, for example:
You need to concatenate the keytab files, thanks to ktutil
command:
ktutil ktutil: read_kt node1-example.keytab ktutil: read_kt node1-acme.keytab ktutil: write_kt /etc/lemonldap-ng/auth.keytab ktutil: quit
You can then remove the original keytab files and protect the final keytab file:
chown apache /etc/lemonldap-ng/auth.keytab chmod 600 /etc/lemonldap-ng/auth.keytab
You can check these documentations to get more information: