Configuring Kerberos
Describes how Kerberos works with MapR tickets.
Configuring Kerberos for Authentication Using MapR Tickets
To use Kerberos to generate MapR Tickets for users, enable Kerberos on the CLDB by creating a Kerberos identity on the Kerberos server used by the cluster and distributing that identity to the other CLDB nodes in the cluster.
If you are using strong encryption with Kerberos with the Oracle JDK, you will require a new Java Cryptography Extension (JCE) policy file.
MapR clusters do not provide Kerberos infrastructure. This section assumes you have a functioning Kerberos realm and your systems have the Kerberos client installed. The tips in this section assume a Linux-based Kerberos environment, and the specific commands for your environment may vary. Please consult with your Kerberos administrator for assistance.
Creating a Kerberos Identity for the CLDB
The CLDB requires a Kerberos server identity, but no other nodes do. By default, this
identity takes the form mapr/<cluster name>
. You can use configure.sh or edit the
mapr-clusters.conf
file to change this default. Use the following
commands in a Linux-based Kerberos environment to set up the identity:
kadmin
: addprinc -randkey mapr/my.cluster.com
: ktadd -k /opt/mapr/conf/mapr.keytab mapr/my.cluster.com
Copy the resulting mapr.keytab
file to the same location on every CLDB
node. The mapr.keytab
file must be owned and readable only by the
mapr
user. You can specify the location of the
mapr.keytab
file in the conf/mapr.login.conf
file. The
default location for mapr.keytab
is /opt/mapr/conf
.
Updating the keytab File
You can use the kadmin
tool to update the server keys that are stored in
the keytab file. Because the server tickets used to authenticate to the CLDB use the new
keys immediately, you must copy the new keytab file to all the CLDB servers in the cluster
immediately after updating the server keys.
To update the keytab file with a new key, run the following command:
kadmin
: ktadd -k /opt/mapr/conf/mapr.keytab mapr/my.cluster.com
The CLDB automatically detects changes to the keytab file on systems that use Java 7 or later. Systems that use Java 6 require a CLDB restart to detect changes to the keytab file.
Starting with the 4.0.1 release of the MapR software, Java 6 is deprecated in favor of Java 7 and Java 8.
Running configure.sh
After a Kerberos principal is created for the CLDB, that principal is added to the
mapr.keytab
file, and the mapr.keytab
file is copied to
all the CLDB servers, Kerberos user authentication is fully enabled for the MapR
cluster.
Two configure.sh
parameters are important for Kerberos:
-K|-kerberosEnable
- lets the rest of the cluster know that Kerberos is enabled, so that clients can auto detect Kerberos tickets and use them to get MapR tickets.-P "<cldbPrincipal>"
- specifies the Kerberos instance which is used to form the CLDB Kerberos principal in the form of mapr/<instance-name>@<realm-name>. Enclose this value in quotes (").
configure.sh
on each MapR cluster node, and each MapR client node that
will communicate with one or more clusters. For more information on , see configure.sh.configure.sh -K -P "<cldbPrincipal>"
Running configure.sh
on each node enters the Kerberos information into the
local clusters.conf
file, so that the following command is all that is
required for the client to access the cluster:
hadoop fs -ls
configure.sh
on each node, the following two commands
are required from the client:maprlogin kerberos
hadoop fs -ls
Kerberos Command Summary
-
kinit: Creates a Kerberos ticket. Prompts the user for userid and password. After
validating, Kerberos creates a ticket file in /tmp that is owned by the user. Use the
-R
option to renew an existing ticket. Kerberos credentials expire in 8-10 hours. Expired credentials must be renewed or replaced. By default, tickets can be renewed for up to 24 hours. - klist: Lists the contents of the user's ticket file.
- kdestroy: Destroys the contents of the user's ticket file. The user is no longer authenticated.
-
kadmin: Used to administer Kerberos. The login for this command is implicitly
<userid>/admin
, since administrator ids typically end in/admin
. - ktutil: Kerberos keytab maintenance utility. Used to combine, or alter Kerberos keytabs.
Disabling Replay Detection for Kerberos Authentication
You can set an option in mapr-clusters.conf
to disable replay detection
for Kerberos runtime authentication.
disableReplayDetection=true
By default, this parameter is set to false
, meaning that MapR clients
enable Kerberos replay detection. Typically, replay detection is enabled to prevent
potential attacks such as the replay of Kerberos packets or multiple login attempts with the
same user ID. Set this parameter to true only if you want MapR clients not to enforce this
detection.
This parameter applies when users attempt an implicit or explicit maprlogin, such as by
using the maprlogin kerberos
command or by submitting jobs and other
operations with kerberosEnable=true
set in the
mapr-clusters.conf
file.
This parameter is used when applications connect to the cluster using Kerberos;
mapr-clusters.conf
only needs to be updated when it is used by such
applications. If all Kerberos access to the cluster is from clients outside the cluster,
only the mapr-clusters.conf
file on those client machines has to be
updated. If Kerberos is used from applications running on the cluster,
mapr-clusters.conf
should be updated there as well.