11 April,19 at 11:49 AM
Pre-Requisites
The pre-requisites are the same as the previous post. Because for the SSO plugin to work we need an AD account to create a keytab, we've added some additional steps.
Obtaining the AD Principal
A keytab file is usually tied to an AD principal; all Centrified systems have one; but in this case, we will have a service account and there are two ways to do this:
Naming conventions
Because we're talking about AD accounts here, your organization may (hopefully) have a naming standard, if not, you have to keep in mind that you need to be able to identify the purpose of the AD account in AD. A naming convention like this: [instanceName-server] is simple enough and descriptive. In this example, my instance is db2inst1 and the server is engcen8, therefore my AD account will be called db2inst-engcen8.
Container OU
If your AD admin is not messy, most likely they will have an OU designated for Service Accounts. In fact, if you worked with Centrify Professional Services, there should be an OU under UNIX with the same name.
AD Account creation
When you request the account, the AD sysadmin will create an account like this:
Typically the best practices for service accounts are to set the password to never expire, and that the account can't change it.
Issue #1 - At this point, the password for this service account is known at least by one person. This will go away once the keytab is adopted, the password will be randomized.
Now there are two things that can happen - the AD admin can grant you temporary full control of the account until you run adkeytab, or can just type in their password in the adequate moment.
Verify the account
Use adquery user and the -A option and inspect the UPN and cn. Here's the truncated output:
$ adquery user -A db2inst1-engcen8 dn:CN=db2inst1-engcen8,CN=Service-Accounts,DC=centrifyimage,DC=vms samAccountName:db2inst1-engcen8 userPrincipalName:db2inst1-engcen8@centrifyimage.vms canonicalName:centrifyimage.vms/Service-Accounts/db2inst1-engcen8
Issue # 2, the account is missing a servicePrincipalName (SPN),
Issue # 3, the the userPrincipalName is in a non-MIT Kerberos friendly format.
This means that we need
Adopt the keytab and modify the account attributes
Based on the information above, our adkeytab command looks like this (elevating with dzdo to write to the target folder):
$ dzdo adkeytab --adopt --principal db2inst1/engcen8.centrifyimage.vms@CENTRIFYIMAGE.VMS --upn db2inst1-engcen8@CENTRIFYIMAGE.VMS --user dwirth -V --keytab /home/db2inst1/db2inst1-engcen8.keytab db2inst1-engcen8
Here's the command output (truncated)
dwirth@CENTRIFYIMAGE.VMS's password: Adding managed account keys to configuration file: db2inst1-engcen8 Changing account 'db2inst1-engcen8' password with user 'dwirth@CENTRIFYIMAGE.VMS' credentials. Key Version = 3 Success: Adopt Account: db2inst1-engcen8
Inspect the account post-adkeytab
$ adquery user -A db2inst1-engcen8 dn:CN=db2inst1-engcen8,CN=Service-Accounts,DC=centrifyimage,DC=vms userPrincipalName:db2inst1-engcen8@CENTRIFYIMAGE.VMS servicePrincipalName:db2inst1/engcen8.centrifyimage.vms
Notice how now the UPN was modified and how the account has a servicePrincipalName.
Make sure the keytab file has the right permissions
The owner of the keytab should be the instance account.
$ chown db2inst1:db2iadm1 /home/db2inst1/db2inst1-engcen8.keytab
At this point, all we need to do is rerun the setupdb2.sh script and follow the prompts to add the SSO plugin; because we don't want to deactivate the existing ones, we will run option 1 again and point to the previously created keytab.
$ dzdo /usr/share/centrifydc/bin/setupdb2.sh inst=db2inst1 Is db2inst1 a DB2 server install? Enter y for yes, n for no [y]: y db2inst1 is a 64 bit instance DB2 server and client setup will be done. Is this DB2 version 9.5 or later? Enter y for yes, n for no [n]: y Which DB2 auth method do you want to use? [1] Username/Password and Single sign-on [2] Single Sign-on only [3] Username/Password only [4] Skip this step Select a number from the menu [1]: Select a number from the menu [1]: 1 Use the CentrifyDC group plugin? Enter y for yes, n for no [y]: y Do you want to configure the instance user db2inst1 as a service account? You must do this step if you want to use the GSS-Plugin. If you already did this step for this instance, select the option to indicate the keytab file name. [1] Use adkeytab to create a service account in Active Directory and keytab file. NOTE: You need to specify a user name with administrator privileges on the domain to use adkeytab. [2] Provide the name of an already existing keytab file. [3] Skip this step Select a number from the menu [1]: 2 What is the name of the keytab file? Full path please. [ /home/db2inst1/db2inst1.keytab ]: /home/db2inst1/db2inst1-engcen8.keytab What group should be used as the group owner of this file? All DB2 instances that you want to use the username/password plugin must be in this group. [db2iadm1]: *********** adkeytab setup (required for GSS-plugin) *********** Using /home/db2inst1/db2inst1-engcen8.keytab for the keytab file for instance: db2inst1 # db2set DB2ENVLIST=KRB5_KTNAME adkeytab setup successfully! ******* Installing the plugins into instance: db2inst1 ******* Installing client side auth plugin # rm -f sqllib/security32/plugin/client/centrifydc_db2gsskrb5.so # cp /usr/share/centrifydc/lib/libcentrifydc_db2gsskrb5.so sqllib/security32/plugin/client/centrifydc_db2gsskrb5.so Continuing will stop the DB2 instance: db2inst1, update the configuration and then start the instance. Continue? y New configuration: Group Plugin (GROUP_PLUGIN) = centrifydc_db2group GSS Plugin for Local Authorization (LOCAL_GSSPLUGIN) = centrifydc_db2gsskrb5 Server List of GSS Plugins (SRVCON_GSSPLUGIN_LIST) = centrifydc_db2gsskrb5 Server Userid-Password Plugin (SRVCON_PW_PLUGIN) = centrifydc_db2userpass Server Connection Authentication (SRVCON_AUTH) = GSS_SERVER_ENCRYPT Database manager authentication (AUTHENTICATION) = SERVER Starting instance # db2start SQL1063N DB2START processing was successful. The plugins for DB2 instance: db2inst1 were set up successfully!
I recommend a reboot at this point.
$ klist Ticket cache: FILE:/tmp/krb5cc_1627391058 Default principal: dwirth@CENTRIFYIMAGE.VMS Valid starting Expires Service principal 11/16/14 22:19:10 11/17/14 08:19:13 krbtgt/CENTRIFYIMAGE.VMS@CENTRIFYIMAGE.VMS renew until 11/17/14 22:19:10
$ db2 db2 => connect to sample Database Connection Information Database server = DB2/LINUXX8664 10.5.0 SQL authorization ID = DWIRTH Local database alias = SAMPLE db2 => quit
$ klist
Ticket cache: FILE:/tmp/krb5cc_1627391058
Default principal: dwirth@CENTRIFYIMAGE.VMS
Valid starting Expires Service principal
11/16/14 22:19:10 11/17/14 08:19:13 krbtgt/CENTRIFYIMAGE.VMS@CENTRIFYIMAGE.VMS
renew until 11/17/14 22:19:10
11/16/14 22:22:36 11/17/14 08:19:13 db2inst1/engcen8.centrifyimage.vms@CENTRIFYIMAGE.VMS
renew until 11/17/14 22:19:10
And there you have it, just like magic!
(10 minutes, 15 seconds)