17 Configuring Kerberos Authentication

Kerberos is a trusted third-party authentication system that relies on shared secrets and presumes that the third party is secure.

Parent topic: Managing Strong Authentication

Enabling Kerberos Authentication

To enable Kerberos authentication for Oracle Database, you must first install it, and then follow a set of configuration steps.

See Also:

Oracle Database Enterprise User Security Administrator's Guide for information on migrating Kerberos users to Kerberos-authenticated enterprise users

Step 1: Install Kerberos

You should install Kerberos Version 5.

The source distribution for notes about building and installing Kerberos provide details. After you install Kerberos, if you are using IBM AIX on POWER systems (64-bit), you should ensure that Kerboros 5 is the preferred authentication method.

  1. Install Kerberos on the system that functions as the authentication server.

    Note:

    After upgrading from a 32-bit version of Oracle Database, the first use of the Kerberos authentication adapter causes an error message: ORA-01637: Packet receive failed.

    Workaround: After upgrading to the 64-bit version of the database and before using Kerberos external authentication method, check for a file named /usr/tmp/oracle_service_name.RC on your computer, and remove it.

  2. For IBM AIX on POWER systems (64-bit), check the authentication method.

    For example:

    /usr/bin/lsauthent

    Output similar to the following may appear:

    Standard Aix
  3. Configure Kerberos 5 as the preferred method.

    For example:

    /usr/bin/chauthent -k5 -std

    This command sets Kerberos 5 as the preferred authentication method (k5) and Standard AIX as the second (std).

  4. To ensure that Kerberos 5 is now the preferred method, check the new configuration. 
    /usr/bin/lsauthent

Kerberos 5
Standard Aix

Step 2: Configure a Service Principal for an Oracle Database Server

You must create a service principal for Oracle Database before the server can validate the identity of clients that authenticate themselves using Kerberos.

  1. Decide on a name for the service principal, using the following format: 
    kservice/kinstance@REALM

    Each of the fields in the service principal specify the following values:

    Service Principal Field Description

    kservice

    A case-sensitive string that represents the Oracle service. This can be the same as the database service name.

    kinstance

    Typically the fully qualified DNS name of the system on which Oracle Database is running.

    REALM

    The name of the Kerberos realm with which the service principal is registered. REALM must always be uppercase and is typically the DNS domain name.

    The utility names in this section are executable programs. However, the Kerberos user name krbuser and the realm EXAMPLE.COM are examples only.

    For example, suppose kservice is oracle, the fully qualified name of the system on which Oracle Database is running is dbserver.example.com and the realm is EXAMPLE.COM. The principal name then is:

    oracle/dbserver.example.com@EXAMPLE.COM
  2. Run kadmin.local to create the service principal. On UNIX, run this command as the root user, by using the following syntax: 
    # cd /kerberos-install-directory/sbin
# ./kadmin.local

    For example, to add a principal named oracle/dbserver.example.com@EXAMPLE.COM to the list of server principals known by Kerberos, you can enter the following:

    kadmin.local:addprinc -randkey oracle/dbserver.example.com@EXAMPLE.COM

Step 3: Extract a Service Key Table from Kerberos

Next, you are ready to extract the service key table from Kerberos and copy it to the Oracle database server/Kerberos client system.

For example, to extract a service key table for dbserver.example.com:

  1. Enter the following to extract the service key table: 
    kadmin.local:  ktadd -k /tmp/keytab oracle/dbserver.example.com
Entry for principal oracle/dbserver.example.com with kvno 2, 
encryption type AES-256 CTS mode with 96-bit SHA-1 HMAC added to keytab WRFILE:
WRFILE:/tmp/keytab

kadmin.local:  exit
  2. To check the service key table, enter the following command: 
    oklist -k -t /tmp/keytab
  3. After the service key table has been extracted, verify that the new entries are in the table in addition to the old ones.

    If they are not, or you need to add more, use kadmin.local to append to them.

    If you do not enter a realm when using ktadd, it uses the default realm of the Kerberos server. kadmin.local is connected to the Kerberos server running on the localhost.

  4. If the Kerberos service key table is on the same system as the Kerberos client, you can move it. If the service key table is on a different system from the Kerberos client, you must transfer the file with a program such as FTP. If using FTP, transfer the file in binary mode.

    The following example shows how to move the service key table on a UNIX platform:

    # mv /tmp/keytab /etc/v5srvtab

    The default name of the service file is /etc/v5srvtab.

  5. Verify that the owner of the Oracle database server executable can read the service key table (/etc/v5srvtab in the previous example).

    To do so, set the file owner to the Oracle user, or make the file readable by the group to which Oracle belongs.

    Do not make the file readable to all users. This can cause a security breach.

Step 4: Install an Oracle Database Server and an Oracle Client

After you extract a service key table from Kerberos, you are ready to install the Oracle Database server and an Oracle client.

  • See the Oracle Database operating system-specific installation documentation for instructions on installing the Oracle database server and client software.

Step 5: Configure Oracle Net Services and Oracle Database

After you install the Oracle Database server and client, you can configure Oracle Net Services on the server and client.

Step 6: Configure Kerberos Authentication

You must set the required parameters in the Oracle database server and client sqlnet.ora files.

Be aware that in a multitenant environment, the settings in the sqlnet.ora file apply to all pluggable databases (PDBs).

Step 6A: Configure Kerberos on the Client and on the Database Server

First, you must configure Kerberos authentication service parameters on the client and on the database server.

  1. Start Oracle Net Manager.

    • (UNIX) From $ORACLE_HOME/bin, enter the following command at the command line:

      netmgr

    • (Windows) Select Start, Programs, Oracle - HOME_NAME, Configuration and Migration Tools, then Net Manager.

  2. Expand Oracle Net Configuration, and from Local, select Profile.
  3. From the Naming list, select Network Security.

    The Network Security tabbed window appears.

  4. Select the Authentication tab.
  5. From the Available Methods list, select KERBEROS5.
  6. Move KERBEROS5 to the Selected Methods list by clicking the right arrow (>).
  7. Arrange the selected methods in order of use.

    To do so, select a method in the Selected Methods list, then click Promote or Demote to position it in the list. For example, if you want KERBEROS5 to be the first service used, move it to the top of the list.

  8. Select the Other Params tab.
  9. From the Authentication Service list, select KERBEROS(V5).
  10. Type Kerberos into the Service field.
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    Description of the illustration GUID-397D9D5F-438E-4E11-8EE1-EC06EE28C648-default.gif

    This field defines the name of the service Oracle Database uses to obtain a Kerberos service ticket. When you provide the value for this field, the other fields are enabled.

  11. Optionally enter values for the following fields:

    • Credential Cache File

    • Configuration File

    • Realm Translation File

    • Key Table

    • Clock Skew

    See the Oracle Net Manager online Help, and Step 6C: Set sqlnet.ora Parameters (Optional), for more information about the fields and the parameters they configure.

  12. From the File menu, select Save Network Configuration.

    The sqlnet.ora file is updated with the following entries in addition to any optional choices that you may have made in the previous step:

    SQLNET.AUTHENTICATION_SERVICES=(KERBEROS5)
SQLNET.AUTHENTICATION_KERBEROS5_SERVICE=kservice

Step 6B: Set the Initialization Parameters

Next, you are ready to set the OS_AUTHENT_PREFIX initialization parameter.

  1. Locate the init.ora file.

    By default, the init.ora file is located in the ORACLE_HOME/dbs directory (or the same location of the data files) on Linux and UNIX systems, and in the ORACLE_HOME\database directory on Windows.

  2. In the init.ora file, set the value of OS_AUTHENT_PREFIX to null in the init.ora initialization parameter file.

    For example:

    OS_AUTHENT_PREFIX=""

    Set this value to null because Kerberos user names can be long, and Oracle user names are limited to 30 characters. Setting this parameter to null overrides the default value of OPS$.

Note:

You can create external database users that have Kerberos user names of more than 30 characters. See Step 8: Create an Externally Authenticated Oracle User for more information.

Step 6C: Set sqlnet.ora Parameters (Optional)

You can set optional sqlnet.ora parameters, in addition to the required parameters, for better security.

  • Optionally, set the parameters listed in the following table on both the client and the Oracle database server.

Table 17-1 Kerberos-Specific sqlnet.ora Parameters

Parameter Description

SQLNET.KERBEROS5_CC_NAME=pathname_to_credentials_cache_file|OS_MEMORY

Specifies the complete path name to the Kerberos credentials cache (CC) file. The default value is operating system-dependent. For UNIX, it is /tmp/krb5cc_userid.

Using the OS_MEMORY option indicates that an OS-managed memory credential cache is used for the credential cache file. The only value currently supported for this is OSMSFT (for Microsoft Windows).

You can use the following formats to specify a value for SQLNET.KERBEROS5_CC_NAME:

  • SQLNET.KERBEROS5_CC_NAME=complete_path_to_cc_file

    For example:

    SQLNET.KERBEROS5_CC_NAME=/tmp/kcache

    SQLNET.KERBEROS5_CC_NAME=D:\tmp\kcache

  • SQLNET.KERBEROS5_CC_NAME=FILE:complete_path_to_cc_file

    For example:

    SQLNET.KERBEROS5_CC_NAME=FILE:/tmp/kcache

  • SQLNET.KERBEROS5_CC_NAME=OSMSFT:

    Use this value if you are running Windows and using a Microsoft KDC.

You can also set this parameter by using the KRB5CCNAME environment variable, but the value set in the sqlnet.ora file takes precedence over the value set in KRB5CCNAME.

For example:

SQLNET.KERBEROS5_CC_NAME=/usr/tmp/krbcache

SQLNET.KERBEROS5_CLOCKSKEW=number_of_seconds_accepted_as_network_delay

This parameter specifies how many seconds can pass before a Kerberos credential is considered out-of-date. It is used when a credential is actually received by either a client or a database server. An Oracle database server also uses it to decide if a credential needs to be stored to protect against a replay attack. The default is 300 seconds.

For example:

SQLNET.KERBEROS5_CLOCKSKEW=1200

SQLNET.KERBEROS5_CONF=pathname_to_Kerberos_configuration_file|AUTO_DISCOVER

This parameter specifies the complete path name to the Kerberos configuration file. The configuration file contains the realm for the default KDC (key distribution center) and maps realms to KDC hosts. The default is operating system-dependent. For UNIX, it is /krb5/krb.conf.

Using the AUTO_DISCOVER option in place of the configuration file enables Kerberos clients to auto-discover the KDC.

For example:

SQLNET.KERBEROS5_CONF=/krb/krb.conf
SQLNET.KERBEROS5_CONF=AUTO_DISCOVER

SQLNET.KERBEROS5_CONF_LOCATION=path_to_Kerberos_configuration_directory

This parameter indicates that the Kerberos configuration file is created by the system, and does not need to be specified by the client. The configuration file uses DNS lookup to obtain the realm for the default KDC, and maps realms to KDC hosts.

For example:

SQLNET.KERBEROS5_CONF_LOCATION=/krb

SQLNET.KERBEROS5_KEYTAB=path_to_Kerberos_principal/key_table

This parameter specifies the complete path name to the Kerberos principal/secret key mapping file. It is used by the Oracle database server to extract its key and decrypt the incoming authentication information from the client. The default is operating system-dependent. For UNIX, it is /etc/v5srvtab.

For example:

SQLNET.KERBEROS5_KEYTAB=/etc/v5srvtab

SQLNET.KERBEROS5_REALMS=path_to_Kerberos_realm_translation_file

This parameter specifies the complete path name to the Kerberos realm translation file. The translation file provides a mapping from a host name or domain name to a realm. The default is operating system-dependent. For UNIX, it is /etc/krb.realms.

For example:

SQLNET.KERBEROS5_REALMS=/krb5/krb.realms

Step 7: Create a Kerberos User

You must create the Kerberos user on the Kerberos authentication server where the administration tools are installed.

The realm must already exist.

Note:

The utility names in this section are executable programs. However, the Kerberos user name krbuser and realm EXAMPLE.COM are examples only. They can vary among systems.

  • Run /krb5/admin/kadmin.local as root to create a new Kerberos user, such as krbuser.

    For example, to create a Kerberos user is UNIX-specific:

    # /krb5/admin/kadmin.local
kadmin.local: addprinc krbuser
Enter password for principal: "krbuser@example.com": (password does not display)
Re-enter password for principal: "krbuser@example.com": (password does not display)
kadmin.local: exit

Step 8: Create an Externally Authenticated Oracle User

Next, you are ready to create an externally authenticated Oracle user.

  1. Log in to SQL*Plus as a user who has the CREATE USER privilege. 
    sqlplus sec_admin - Or, CONNECT sec_admin@hrpdb
Enter password: password
  2. Ensure that the OS_AUTHENT_PREFIX is set to null ("").
  3. Create an Oracle Database user account that corresponds to the Kerberos user. Enter the Oracle user name in uppercase and enclose it in double quotation marks.

    For example:

    CREATE USER "KRBUSER@EXAMPLE.COM" IDENTIFIED EXTERNALLY; 
GRANT CREATE SESSION TO "KRBUSER@EXAMPLE.COM";

    If the user's Kerberos principal name is longer than 30 characters, and up to 1024 characters, then create the user by using the following syntax:

    CREATE USER db_user_name IDENTIFIED EXTERNALLY AS 'kerberos_principal_name';

    For example:

    CREATE USER KRBUSER IDENTIFIED EXTERNALLY AS 'KerberosUser@example.com';

Note:

The database administrator should ensure that two database users are not identified externally by the same Kerberos principal name.

Step 9: Get an Initial Ticket for the Kerberos/Oracle User

Before you can connect to the database, you must ask the Key Distribution Center (KDC) for an initial ticket.

  • To request an initial ticket, run the following command on the client:

    % okinit username

    If you want to enable credentials that can be used across database links, then include the -f option and provide the Kerberos password when prompted.

    % okinit -f
Password for krbuser@EXAMPLE.COM:(password does not display)

Utilities for the Kerberos Authentication Adapter

The Oracle Kerberos authentication adapter utilities are designed for an Oracle client with Oracle Kerberos authentication support installed.

okinit Utility Options for Obtaining the Initial Ticket

The okinit utility obtains and caches Kerberos tickets.

This utility is typically used to obtain the ticket-granting ticket, using a password entered by the user to decrypt the credential from the key distribution center (KDC). The ticket-granting ticket is then stored in the user's credential cache.

The following table lists the options available with okinit. To use the functionality that is described in this table, you must set the sqlnet.ora SQLNET.KERBEROS5_CONF_MIT parameter to TRUE. (Note that SQLNET.KERBEROS5_CONF_MIT is deprecated, but is retained for backward compatibility for okinit.)

Table 17-2 Options for the okinit Utility

Option Description

-f | -F

Requests forwardable or non-forwardable tickets. This option is necessary to follow database links.

-l lifetime

Specifies the lifetime of the ticket-granting ticket and all subsequent tickets. By default, the ticket-granting ticket is good for eight (8) hours, but shorter or longer-lived credentials may be desired. The KDC can ignore this option or put site-configured limits on what can be specified. The lifetime value is a string that consists of a number qualified by w (weeks), d (days), h (hours), m (minutes), or s (seconds), as in the following example:

okinit -l 2wld6h20m30s

The example requests a ticket-granting ticket that has a lifetime of 2 weeks, 1 day, 6 hours, 20 minutes, and 30 seconds.

-s start_time

Specifies the duration of the delay before the ticket can become valid. Tickets are issued with the invalid flag set.

-r renewable_life

Requests renewable tickets with a total lifetime of renewable_life

-p | -P

Requests proxiable or non-proxiable tickets

-a

Requests tickets that are restricted to the local address of the host

-A

Requests tickets not restricted by address

-E

Treats the principal name as an enterprise name

-v

Requests that the ticket-granting ticket in the cache be passed to the KDC for validation. If the ticket is within the requested time range, then the cache is replaced with the validated ticket.

-R

 Requests renewal of the ticket-granting ticket

-k [-t keytab_file]

Requests a ticket, which is obtained from a key in the local host’s keytab

-n

Requests anonymous processing

-C

 Requests canonicalization of the principal name, and enables the KDC to reply with a different client principal from the one that was requested

-c cache_name

Specifies the name of a cache as a cache location. For UNIX, the default is /tmp/krb5cc_uid. You can also specify the alternate credential cache by using the SQLNET.KERBEROS5_CC_NAME parameter in the sqlnet.ora file.

-I input_cache

Specifies the name of a credential cache that already contains a ticket. When it obtains that ticket, if the information about how the ticket was obtained is stored in cache, then the same information will be used to affect how new credentials are obtained.

-T armor_cache

If supported by the KDC, this cache is used to armor the request, preventing offline dictionary attacks and enabling the use of additional pre-authentication mechanisms.

-X attribute[=value

 Specifies a pre-authentication attribute and value. Specifies one of the following values:

  • X509_user_identity=value specifies where to find the user’s X509 identity information

  • X509_anchors=value specifies where to find trusted X509 anchor information

  • flag_RSA_PROTOCOL[=yes] specifies the use of RSA rather than the default Diffie-Hellman protocol

-e

Specifies a number representing the Kerberos encryption type to use.

This option can be used to request a particular Kerberos encryption type key for the session. If you specify more than one encryption type, then the KDC chooses the common and strongest encryption type from the list.

The following values are allowed:

  • 1 for DES-CBC-CRC

  • 3 for DES-CBC-MD5

  • 16 for DES3-CBC-SHA1

  • 18 for AES256-CTS

  • 23 for RC4-HMAC

The following example requests for the AES256-CTS encryption type:

okinit -e 1 -e 18 krbuser@REALM

Note that you can repeat the option to request multiple encryption types.

-?

List command line options.

oklist Utility Options for Displaying Credentials

The oklist utility displays the list of tickets held.

The following table lists the available oklist options. To use the functionality that is described in this table, you must set the sqlnet.ora SQLNET.KERBEROS5_CONF_MIT parameter to TRUE. (Note that SQLNET.KERBEROS5_CONF_MIT is deprecated, but is retained for backward compatibility for oklist.)

Table 17-3 Options for the oklist Utility

Option Description

-f

Show flags with credentials. Relevant flags are:

  • I, credential is a ticket-granting ticket

  • F, credential is forwardable

  • f, credential is forwarded.

-c

Specify an alternative credential cache. In UNIX, the default is /tmp/krb5cc_uid. The alternate credential cache can also be specified by using the SQLNET.KERBEROS5_CC_NAME parameter in the sqlnet.ora file.

-k

List the entries in the service table (default /etc/v5srvtab) on UNIX. The alternate service table can also be specified by using the SQLNET.KERBEROS5_KEYTAB parameter in the sqlnet.ora file.

-e

Displays the encryption types of the session key and the ticket for each credential in the credential cache, or each key in the keytab file.

-l

If a cache collection is available, displays a table summarizing the caches present in the collection.

-A

If a cache collection is available, displays the contents of all of the caches in the collection

-s

Runs utility without producing output. Utility will exit with status 1 if the cache cannot be read or is expired, else with status 0

-a

Displays a list of addresses in the credential

-n

Shows numeric addresses instead of reverse-resolving addresses

-C

Lists configuration data that has been stored in the credentials cache when klist encounters it. By default, configuration data is not listed.

-t

Displays the time entry timestamps for each keytab entry in the keytab file

-K

Displays the value of the encryption key in each keytab entry in the keytab file

-V

Displays the Kerberos version number and exit.

The show flag option (-f) displays additional information, as shown in the following example:

% oklist -f
04-Aug-2015 21:57:51   28-Aug-2015 05:58:14
krbtgt/EXAMPLE.COM@EXAMPLE.COM
Flags: FI

okdstry Utility Options for Removing Credentials from the Cache File

The okdstry (okdestroy) utility removes credentials from the cache file.

The following table lists the available okdstry options. To use the functionality that is described in this table, you must set the sqlnet.ora SQLNET.KERBEROS5_CONF_MIT parameter to TRUE. (Note that SQLNET.KERBEROS5_CONF_MIT is deprecated, but is retained for backward compatibility for okdstry.)

Table 17-4 Options for the okdstry Utility

Option Description

—A

Destroys all caches in the collection, if a cache collection is available

—q

Runs quietly. Normally okdstry beeps if it fails to destroy the user’s tickets. This flag suppresses this behavior.

—c cache_name

Uses cache_name as the credentials (ticket) cache name and location. For UNIX, the default is /tmp/krb5cc_uid. You can also specify the alternate credential cache by using the SQLNET.KERBEROS5_CC_NAME parameter in the sqlnet.ora file.

okcreate Utility Options for Automatic Keytab Creation

The okcreate utility automates the creation of keytabs from either the KDC or a service endpoint.

The following table lists the available okcreate options.

Table 17-5 okcreate Utility Options for Automatic Keytab Creation

Option Description

-name service_name

Specifies the service name of the kerberized service for which to get a keytab.The default is oracle.

—hosts path-to_hosts_list

Specifies either a comma-separated list of hosts for which to get the keytab, or the path to a text file that contains a list of the hosts. The default is none.

—out path_to_output

Specifies the output path to store the resulting keytabs. The default is the current directory.

Ensure that this directory is readable only by the root user. Never send keytabs over the network in clear text.

—k

For use if the operation is performed on the KDC. Do not use this option if you are using —s.

—s

For use if the operation is performed on a Kerberized service. Do not use this option if you are using —k.

-u KDC_username

Specifies the user name for the KDC. Only use this setting on a Kerberized service endpoint.

If you specify the —s and omit this setting, then okcreate prompts for the KDCuser@KDCmachine.

-r

Specifies the Kerberos realm

—p

Specifies the Kerberos principal

-q

Specifies the Kerberos query

—d

Specifies the KDC database name

—e

Specifies the salt list to be used for any new keys that are created

—m

Specifies to prompt for the KDC master password

Connecting to an Oracle Database Server Authenticated by Kerberos

After Kerberos is configured, you can connect to an Oracle database server without using a user name or password.

  • Use the following syntax to connect to the database without using a user name or password:

    $ sqlplus /@net_service_name

In this specification, net_service_name is an Oracle Net Services service name. For example:

$ sqlplus /@oracle_dbname

See Also:

Oracle Database Heterogeneous Connectivity User's Guide for information about external authentication

Configuring Interoperability with a Windows 2008 Domain Controller KDC

You can configure Oracle Database to interoperate with a Microsoft Windows 2008 domain controller key distribution center (KDC).

About Configuring Interoperability with a Windows 2008 Domain Controller KDC

Oracle Database complies with MIT Kerberos.

This enables Oracle Database to interoperate with tickets that are issued by a Kerberos Key Distribution Center (KDC) on a Windows 2008 domain controller. This process enables Kerberos authentication with an Oracle database.

Step 1: Configure Oracle Kerberos Client for Windows 2008 Domain Controller

You can configure the Oracle Kerberos client to interoperate with a Microsoft Windows 2008 Domain Controller KDC.

Step 1A: Create the Client Kerberos Configuration Files

You must configure a set of client Kerberos configuration files that refer to the Windows 2008 domain controller as the Kerberos KDC.

  • Create the krb.conf and krb5.realms files. Oracle Database provides a default krb5.conf file, which you must modify for your site.

    The krb5.conf file is located in the location indicated by the SQLNET.KERBEROS_CONF parameter.

For example, assuming that the Windows 2008 domain controller is running on a node named sales3854.us.example.com:

  • krb.conf file

    For example:

    SALES3854.US.EXAMPLE.COM
SALES3854.US.EXAMPLE.COM 
sales3854.us.example.com admin server

  • krb5.conf file

    For example:

    [libdefaults]
default_realm=SALES.US.EXAMPLE.COM
[realms]
SALES.US.EXAMPLE.COM= { kdc=sales3854.us.example.com:88 }
[domain_realm]
.us.example.com=SALES.US.EXAMPLE.COM

  • krb5.realms file

    For example:

    us.example.com SALES.US.EXAMPLE.COM

Step 1B: Specify the Oracle Configuration Parameters in the sqlnet.ora File

The sqlnet.ora file has Kerbose 5–specific parameters.

Configuring an Oracle client to interoperate with a Windows 2008 domain controller KDC uses the same sqlnet.ora file parameters that are used for Kerberos on the client and on the database server. These parameters are described in Step 6A: Configure Kerberos on the Client and on the Database Server.

  • Set the following parameters in the sqlnet.ora file on the client:

    SQLNET.KERBEROS5_CONF=pathname_to_Kerberos_configuration_file
SQLNET.KERBEROS5_CONF_MIT=TRUE
SQLNET.AUTHENTICATION_KERBEROS5_SERVICE=Kerberos_service_name
SQLNET.AUTHENTICATION_SERVICES=(BEQ,KERBEROS5)

Note:

  • The SQLNET.KERBEROS5_CONF_MIT parameter has been deprecated, but is retained for backward compatibility for the okint, oklist, and okdstry utilities.

  • Ensure that the SQLNET.KERBEROS5_CONF_MIT parameter is set to TRUE because the Windows 2008 operating system is designed to interoperate only with security services that are based on MIT Kerberos version 5.

Step 1C: Specify the Listening Port Number

The Windows 2008 domain controller KDC listens on UDP/TCP port 88.

  • Ensure that the system file entry for kerberos5 is set to UDP/TCP port 88.

    For the UNIX environment, ensure that the first kerberos5 entry in the /etc/services file is set to 88.

Step 2: Configure a Windows 2008 Domain Controller KDC for the Oracle Client

Next, you are ready to configure a Microsoft Windows 2008 Domain Controller KDC to interoperate with an Oracle Client.

See Also:

Microsoft documentation for information about how to create users in Active Directory.

Step 2A: Create the User Account

You must create a user account for the Microsoft Windows 2008 Domain Controller KDC.

  • On the Windows 2008 domain controller, create a new user account for the Oracle client in Microsoft Active Directory.

Step 2B: Create the Oracle Database Principal User Account and Keytab

After you create the user account, you are ready to create the Oracle Database principal user account.

After you create this account on the Windows 2008 domain controller, you must use the okcreate utility to register it with the principal keytab. You can run this utilty on the same KDC to create all the service keytabs rather than creating them individually, or you can run okcreate from a service endpoint that connects to the KDC, run the ncessary commands, and then copy the resulting keytab back to the service endpoint.
  1. Create a new user account for the Oracle database in Microsoft Active Directory.

    For example, if the Oracle database runs on the host sales3854.us.example.com, then use Active Directory to create a user with the user name sales3854.us.example.com and the password oracle.

    Do not create a user as host/hostname.dns.com, such as oracle/sales3854.us.example.com, in Active Directory. Microsoft's KDC does not support multipart names like an MIT KDC does. An MIT KDC allows multipart names to be used for service principals because it treats all principals as user names. However, Microsoft’s KDC does not.

  2. Run the okcreate command to create a keytab that will use this user account. The syntax is as follows: 
    okcreate (-s [-u KDCuser@KDCmachine] | -k) 
  [-name service_name] [-hosts path_to_host_list] 
  [-out path_to_output] [-r realm] [-p principal] 
  [-q query] [-d dbname] [-e enc:salt...] [-m] 
  [-x db_args]

    See okcreate Utility Options for Automatic Keytab Creation for details about the okcreate options.

    For example:

    okcreate -s -u kdcuser1@kdcmachine1 -name oracle 
  -hosts sales3854.us.example.com 
  -out /OSsecured/keytablocation
  3. Copy the extracted keytab file to the host computer where the Oracle database is installed.

    For example, the keytab that was created in the previous step can be copied to /krb5/v5svrtab.

See Also:

Detailed information about Windows 2008 interoperability with Kerberos 5 that is available at the following URL:

http://technet.microsoft.com/hi-in/windowsserver/2000/bb735396(en-us).aspx

Step 3: Configure Oracle Database for a Windows 2008 Domain Controller KDC

You must configure the Oracle database for the domain controller on the host computer where the Oracle database is installed.

Step 3A: Set Configuration Parameters in the sqlnet.ora File

You must first set configuration parameters for the database.

  • Specify values for the following parameters in the sqlnet.ora file for the database server:

    SQLNET.KERBEROS5_CONF=pathname_to_Kerberos_configuration_file
SQLNET.KERBEROS5_KEYTAB=pathname_to_Kerberos_principal/key_table
SQLNET.KERBEROS5_CONF_MIT=TRUE
SQLNET.AUTHENTICATION_KERBEROS5_SERVICE=Kerberos_service_name
SQLNET.AUTHENTICATION_SERVICES=(BEQ,KERBEROS5)

Note:

  • The SQLNET.KERBEROS5_CONF_MIT parameter has been deprecated, but is retained for backward compatibility for the okint, oklist, and okdstry utilities.

  • Ensure that the SQLNET.KERBEROS5_CONF_MIT parameter is set to TRUE because the Windows 2008 operating system is designed to interoperate only with security services that are based on MIT Kerberos version 5.

  • Be aware that in a multitenant environment, the settings in the sqlnet.ora file apply to all PDBs.

Step 3B: Create an Externally Authenticated Oracle User

After you set the configuration parameters, you are ready to create an externally authenticated Oracle user.

See Also:

Step 6: Configure Kerberos Authentication for information about using Oracle Net Manager to set the sqlnet.ora file parameters.

Step 4: Obtain an Initial Ticket for the Kerberos/Oracle User

Before a client can connect to the database, the client must request an initial ticket.

Note:

The user does not need to explicitly request for an initial ticket, using the okinit command, when using the Windows native cache.

If the Oracle client is running on Microsoft Windows 2008 or later, the Kerberos ticket is automatically retrieved when the user logs in to Windows.

See Also:

Microsoft documentation for details about the Kerbtray.exe utility, which can be used to display Kerberos ticket information for a system

Configuring Kerberos Authentication Fallback Behavior

You can configure fallback behavior (password-based authentication) in case the Kerberos authentication fails.

After you have configured Kerberos authentication for Oracle clients to use Kerberos authentication to authenticate to an Oracle database, there are cases where you may want to fall back to password-based authentication. An example would be if you have fixed user database links in the Oracle database.
  • To enable Kerberos authentication to fall back to password-based authentication, set the SQLNET.FALLBACK_AUTHENTICATION parameter to TRUE in the sqlnet.ora files on both the client and server.
    The default of this parameter is FALSE. This means that by default, the connection fails when Kerberos authentication fails.

See Also:

Oracle Database Net Services Reference for more information about the SQLNET.FALLBACK_AUTHENTICATION parameter

Troubleshooting the Oracle Kerberos Authentication Configuration

Oracle provides guidance for common Kerberos configuration problems.

Common problems are as follows:

  • If you cannot get your ticket-granting ticket using okinit:

    • Ensure that the default realm is correct by examining the krb.conf file.

    • Ensure that the KDC is running on the host specified for the realm.

    • Ensure that the KDC has an entry for the user principal and that the passwords match.

    • Ensure that the krb.conf and krb.realms files are readable by Oracle.

    • Ensure that the TNS_ADMIN environment variable is pointing to the directory containing the sqlnet.ora configuration file.

  • If you have an initial ticket but still cannot connect:

    • After trying to connect, check for a service ticket.

    • Check that the sqlnet.ora file on the database server side has a service name that corresponds to a service known by Kerberos.

    • Check that the clocks on all systems involved are set to times that are within a few minutes of each other or change the SQLNET.KERBEROS5_CLOCKSKEW parameter in the sqlnet.ora file.

  • If you have a service ticket and you still cannot connect:

    • Check the clocks on the client and database server.

    • Check that the v5srvtab file exists in the correct location and is readable by Oracle. Remember to set the sqlnet.ora parameters.

    • Check that the v5srvtab file has been generated for the service named in the sqlnet.ora file on the database server side.

  • If everything seems to work fine, but then you issue another query and it fails:

    • Check that the initial ticket is forwardable. You must have obtained the initial ticket by running the okinit utility.

    • Check the expiration date on the credentials. If the credentials have expired, then close the connection and run okinit to get a new initial ticket.