Kerberos High Availability Functionality Testing

[#1]

Is there a way to test MIT kerberos high availability functionality?Any approaches?

thanks in advance.

[#2 · Accepted solution]

@harish

Yes for sure, that's doable I am assuming you have set up 2 kdc's on different networks but accessible to the cluster,

Assumptions:

You MUST have successfully configure the 2 master and slave KDC's

my realm =REALM
Master host=master-kdc.test.com
Slave host=slave-kdc.test.com 

Contents of /var/kerberos/krb5kdc/kpropd.acl:

host/master-kdc.test.com@REALM
host/slave-kdc.test.com@REALM 

# Create the configuration for kpropd on both the Master and Slave KDC hosts:

# Create /etc/xinetd.d/krb5_prop with the following contents.

service krb_prop
{
        disable         = no
        socket_type     = stream
        protocol        = tcp
        user            = root
        wait            = no
        server          = /usr/sbin/kpropd
} 

# Configure xinetd to run as a persistent service on both the Master and Slave KDC hosts:

# systemctl enable xinetd.service
# systemctl start xinetd.service 

# Copy the following files from the Master KDC host to the Slave KDC host:

/etc/krb5.conf 
/var/kerberos/krb5kdc/kadm5.acl 
/var/kerberos/krb5kdc/kdc.conf 
/var/kerberos/krb5kdc/kpropd.acl 
/var/kerberos/krb5kdc/.k5.REALM 

# Perform the initial KDC database propagation to the Slave KDC:

# kdb5_util dump /usr/local/var/krb5kdc/slave_datatrans 
# kprop -f /usr/local/var/krb5kdc/slave_datatrans slave-kdc.REALM 

# Start the Slave KDC :

# systemctl enable krb5kdc 
# systemctl start krb5kdc 

# Script to propagate the updates from the Master KDC to the Slave KDC. Create a cron job, or the like, to run this script on a frequent basis.

#!/bin/sh 
#/var/kerberos/kdc-slave-propogate.sh 
kdclist = "slave-kdc.customer.com" 
  /sbin/kdb5_util dump /usr/local/var/krb5kdc/slave_datatrans 
  for kdc in $kdclist 
  do 
 /sbin/kprop -f /usr/local/var/krb5kdc/slave_datatrans $kdc 
done 

How to test the KDC HA is to shut down the master KDC as start the slave KDC note both KDC's should NEVER be running at the same time, the crontab script should do the propagation of all changes in the KDC database in the master to the slave.

CAUTION

Run the kprop before shutting down the master KDC then to test the kdc HA log on to the cluster linux CLI follow the below steps my steps I am using the root user

Switch user to hive/spark/Yarn etc

# su - hive 

Check if the hive user still has valid Kerberos ticket The below output shows the hive user still has a valid ticket

$ klist 
Ticket cache: FILE:/tmp/krb5cc_507 
Default principal: hdfs-host1@{REALM} 
Valid starting 		Expires 		Service principal 
12/28/16 22:57:11 	12/29/16 22:57:11 	krbtgt/{REALM}@{REALM} 		renew until 12/28/16 22:57:11 
12/28/16 22:57:11 	12/29/16 22:57:11 	HTTP/host1.test.com@{REALM} 	renew until 12/28/16 22:57:11 
12/28/16 22:57:11 	12/29/16 22:57:11 	HTTP/host1.com@{REALM} 		renew until 12/28/16 22:57:11 

# Destroy the Kerberos tickets as user hive

$ kdestroy 

Running the previous command shouldn't give you any lines, now try getting a valid ticket by running the following command format {kinit -kt $keytab $principal}

$ kinit -kt /etc/security/keytabs/hive.keytab {PRINCIPAL} 

Repeating the klist should give the hive user a valid ticket this will validate that the HA is functioning well.

[#3]

Thank for your information @Geoffrey Shelton Okot

[#4]

Hi @Geoffrey Shelton Okot,

While testing Kerberos High Availability ,i stopped Master KDC server..and started kadmin on slave, and created a new principal (on slave).when i tried to get kerberos ticket for new principal ,it is failing with below error.

Error: kinit: Client 'user@RXSKNY.HDP.XX.COM' not found in Kerberos database while getting initial credentials

Any thoughts on this?

Thanks.

[#5]

@harish

Was the creation successful without errors? If so can you list the principals in the slave KDC

On the slave

# kadmin.local
kadmin:  listprincs

Is your slave KDC also in the krb5.conf?

In the format.

[realms]
  EXAMPLE.COM = {
    ...
    kdc = kdc1.example.com
    kdc = kdc2.example.com
    ...
  }

Because multiple KDCs may exist for an installation (failover, high availability, etc, Ambari should allow a user to specify multiple KDC hosts to be set while enabling Kerberos and updating the Kerberos service's configuration.

This should be done by allowing kerberos-env/kdc_host to accept a (comma-)delimited list of hosts and then parsing that list properly when building the krb5.conf file where each kdc_host item generates an entry in the relevant realm block

kerberos-env

And in Ambari your kerberos.env should have an entry the

{
  ...
 "kdc_hosts" : "kdc1.example.com, kdc2.example.com"
  ...
}

Some Ambari KDC documentation

To backup a KDC database to a file, use krb5_util_dump.

# kdb5_util dump kdcfile 

To restore the KDC database from the dump file created in the above step, do the following:

# kdb5_util load kdcfile

Please revert

[#6]

Hi @Geoffrey Shelton Okot

The new principal creation was successful and i can listprincs it with no issues.After enabling kerberos HA ,i had added secondary host in ambari,now every krb5.conf file is updated with two hosts like above.But the the new principal created on slave after disabling master KDC is failing with no credentials found error.

thanks.

[#7]

Hi @Geoffrey Shelton Okot

The principal creation was successful and i added secondary host in ambari after enabling Kerberos HA,every krb5.conf file in the cluster is modified with two KDC hosts as you mentioned above.But the new principal created on slave KDC(after disabling master) is not working as expected.

Thanks.

[#8]

@harish

Can you share with me exactly how you created the new principal and keytab? I would like to see the syntax remember to garble sensitive info.

Also remember to add a new entry in the cron kprop to also propagate the newly create principal in the slave KDC database to the Primary so in case you switch back everything is in sync !!

[#9]

Hey @Shelton, 

Thank you so much this article helps me a lot to configure KDC HA in Cloudera  6.1.1 CDH. The only one issue I am facing right now is when I stop my Master KDC and create a new principal using slave KDC it works fine but when I UP Master KDC the new created principal is deleted because it back to its previous state can you please share the script or cron tab configuration for syncing both KDC if one down than other will syn newly created principal when ever its up.

[#10]

@USMAN_HAIDER 

When you create a new Principal in the slave KDC you should also have a  crontab  that will propagate it to the master

#!/bin/sh 
#/var/kerberos/kdc-master-propogate.sh 
kdclist = "slave-kdc.customer.com" 
  /sbin/kdb5_util dump /usr/local/var/krb5kdc/master_datatrans 
  for kdc in $kdclist 
  do 
 /sbin/kprop -f /usr/local/var/krb5kdc/master_datatrans $kdc 
done 

This way the  principals will be sync'ed