Configuring Kerberos Authentication for Databases with a Microsoft Windows 2008 R2 Active Directory KDC

This post describes how to configure an Oracle database for Kerberos authentication with Microsoft Windows 2008 R2 Active Directory, and how to configure the Oracle clients.

Topology

Kerberos Server (Microsoft KDC):

  • Host name: addemo1.ziontech.demo
  • Microsoft Windows Server 2008 R2 Enterprise Edition with Service Pack 1
  • Active Directory (incorporating Kerberos Key Distribution Centre (KDC)
  • Realm name: ziontech.demoRealm name: ziontech.demo

Oracle Database:

  • Host name: db1.ziontech.demo Host name: db1.ziontech.demo
  • Oracle Enterprise Linux 6Oracle Enterprise Linux 6
  • Oracle11g R2 Server Enterprise Edition with Oracle Advanced Security Option (ASO) with 11.2.0.4

Oracle Client:

  • Host name: win7a.ziontech.demoHost name: win7a.ziontech.demo
  • Microsoft Windows 7 64 bitMicrosoft Windows 7 64 bit
  • Oracle11g R2 64 bit Client installation with Oracle Advanced Security Option (ASO) with 11.2.0.4

ASO approach in this post works only with Oracle Database and Clients 11.2.0.2 patchset or higher

 

Section 1: On AD machine

1.1 Create two users (principals in Kerberos terminology)

testuser1, which will be used to connect to DB from client

testuser1

Second for Oracle DB server,

db1

→ Check password never expires option for sever principals

1.2 Create Key Table in Windows 2008 R2

The final step on the Windows 2008 R2 server is to extract a key table for the database server principal. This is done using the KTPASS.EXE tool.

ktpass.exe -princ [email protected] -mapuser ZIONTECHDEMO\db1.ziontech.demo -crypto all -pass Welcome9 -out c:\keytab

The resulting keytab file should then be transferred to the machine running the Oracle Database

There is a process on how to validate keytab (read this post). Using this approach, we can avoid lot of troubleshooting upfront by ensuring that the KVNO value is compatible.

As mentioned in above referenced post, perform following ldapsearch query to obtain msDS-KeyVersionNumber from Active Directory.

ldapsearch -h ad.ziontech.demo -p 389 -D "[email protected]" -w "Welcome1" -b "DC=ziontech,DC=demo" -s sub servicePrincipalName=oracle/db1.ziontech.demo msDS-KeyVersionNumber

The output will look like:

CN=db1,CN=Users,DC=ziontech,DC=demo
msDS-KeyVersionNumber=6

Then, increment value of msDS-KeyVersionNumber by 1 and pass it as a value to the parameter -kvno in ktpass command.

We can even specify specific supported algorithm(s) for crypto parameter and use this version of ktpass instead of above.

ktpass.exe -princ [email protected] -mapuser ZIONTECHDEMO\db1.ziontech.demo -crypto AES256-CTS-HMAC-SHA1-96 -pass Welcome9 -ptype KRB5_NT_PRINCIPAL -kvno 7 -out c:\keytab

Section 2: On DB machine

2.1 Verify that the system settings remote_os_authent=false and os_authent_prefix=”” are configured correctly:

SQL> select value from v$parameter where name = 'os_authent_prefix';
SQL> select value from v$parameter where name = 'remote_os_authent';

If you see something like ops$ for os_authent_prefix, it has to be changed to null using following process:

op1

SQL> create pfile='/tmp/pfile.txt' from spfile;
SQL> shutdown immediate;

Add this to the “/tmp/pfile.txt” file:

os_authent_prefix=''

Recreate the pfile:

SQL> sqlplus / as sysdba
SQL> create spfile from pfile='/tmp/pfile.txt';
SQL> startup

op2

 

2.2 Configure SQLNET for Kerberos

Modify sqlnet.ora with following configuration:

NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)
ADR_BASE = /app/db1

SQLNET.KERBEROS5_KEYTAB=/app/kerberos/keytab
SQLNET.KERBEROS5_CONF=/app/kerberos/krb5.conf
SQLNET.KERBEROS5_CONF_MIT=TRUE
SQLNET.AUTHENTICATION_KERBEROS5_SERVICE=oracle
SQLNET.AUTHENTICATION_SERVICES=(BEQ,KERBEROS5)

 

Create /app/kerberos/krb5.conf with following content:

[libdefaults]
default_realm = ZIONTECH.DEMO

[realms]
ZIONTECH.DEMO = {
kdc = addemo1.ziontech.demo:88
}

[domain_realm]
.ziontech.demo = ZIONTECH.DEMO
ziontech.demo = ZIONTECH.DEMO

 

2.3 Create test user on Database

create user "[email protected]" identified externally;
grant create session to "[email protected]";

This username must be created in uppercase and must have the realm (Active Directory domain) specified.This username must be created in uppercase and must have the realm (Active Directory domain) specified.

Section 3: On Client Machine

  • Login to Windows 7 client as testuser1 to ZIONTECH.DEMO domain
  • Since client Windows PC is a member of Active Directory Domain, and the user has logged into the Windows machine as a domain user, user should be able to connect to Oracle Database without need for Oracle client.
  • Client is already installed under default location:  C:\app\testuser1\product\11.2.0\client_1\

Modify sqlnet.ora to contain following information:

NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)

SQLNET.KERBEROS5_CC_NAME=OSMSFT://
SQLNET.AUTHENTICATION_SERVICES= (beq,kerberos5)
SQLNET.KERBEROS5_CONF =c:\kerberos\krb5.conf
SQLNET.KERBEROS5_CONF_MIT = true

 

Create krb5.conf in the location defined above:

SQLNET.KERBEROS5_CC_NAME=c:\kerberos\cc
SQLNET.AUTHENTICATION_SERVICES= (beq,kerberos5)
SQLNET.KERBEROS5_CONF =c:\kerberos\krb5.conf
SQLNET.KERBEROS5_CONF_MIT = true

 

Create tnsnames.ora

DB1 =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = db1.ziontech.demo)(PORT = 1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = db1.ziontech.demo)
)
)

 

Connect to Database using SQLplus.

sqlplus1

User is automatically logged on to database as Oracle Client uses the internal Windows credentials cache.

  

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