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Basic Security Measures for Oracle

This article is based on Oracle Database Security Checklist and Metalink Note:340009.1 and presents some basic steps to increase the security of your Oracle database servers.

Default Oracle Passwords

By default Oracle creates a number of schemas, each with a default password. Although many of these users are locked, it is still good practice to switch to non-default passwords in case the are unlocked by mistake. In addition, regular users often switch their passwords to match their username. Both of these situations represent a security risk.

Pete Finnigan has an Oracle Default Password Auditing Tool that checks for default passwords, and users whose passwords match their usernames. This is pretty handy to pick up any loose ends. To use this tool, download and extract the zip file. Run the osp_install.sql script to install the password checker and the ops_exec.sql file to run it.

Password Management

The Oracle database includes a range of functionilty to help secure database users. Unused accounts should be locked, while accounts that are used intermittantly should be unlocked as needed.
ALTER USER scott ACCOUNT UNLOCK;

-- Use the schema.

ALTER USER scott ACCOUNT LOCK;
Password aging, expiration and history is managed via profiles, as shown below.
CONN sys/password AS SYSDBA

CREATE PROFILE my_profile LIMIT
  FAILED_LOGIN_ATTEMPTS 3  -- Account locked after 3 failed logins.
  PASSWORD_LOCK_TIME 5     -- Number of days account is locked for. UNLIMITED required explicit unlock by DBA.
  PASSWORD_LIFE_TIME 30    -- Password expires after 90 days.
  PASSWORD_GRACE_TIME 3    -- Grace period for password expiration.
  PASSWORD_REUSE_TIME 120  -- Number of days until a specific password can be reused. UNLIMITED means never.
  PASSWORD_REUSE_MAX 10    -- The number of changes required before a password can be reused. UNLIMITED means never.
/

ALTER USER scott PROFILE my_profile;
The PASSWORD_REUSE_TIME and PASSWORD_REUSE_MAX parameters work in conjunction, so if either is set to unlimited password reuse is prevented.

Password complexity is enforced using a verification function. This must accept three parameters (username, password and old_password) and return a boolean value, where the value TRUE signifies the password is valid. The example below forces the password to be at least 8 characters long.
CREATE OR REPLACE FUNCTION my_varification_function (
  username      VARCHAR2,
  password      VARCHAR2,
  old_password  VARCHAR2)
  RETURN BOOLEAN AS
BEGIN
  IF LENGTH(password) < 8 THEN
    RETURN FALSE;
  ELSE
    RETURN TRUE;
  END IF;
END my_varification_function;
/
Once the function is compiled under the SYS schema it can be referenced by the PASSWORD_VERIFY_FUNCTION parameter of a profile. 
ALTER PROFILE my_profile LIMIT
  PASSWORD_VERIFY_FUNCTION my_varification_function;
The code below assigns the completed profile to a user and tests it.
SQL> ALTER USER scott PROFILE my_profile;

User altered.

SQL> ALTER USER scott IDENTIFIED BY small;
ALTER USER scott IDENTIFIED BY small
*
ERROR at line 1:
ORA-28003: password verification for the specified password failed
ORA-28003: password verification for the specified password failed


SQL> ALTER USER scott IDENTIFIED BY much_bigger;

User altered.

SQL>
A more complete example of a password varification function is provided by the "$ORACLE_HOME/rdbms/admin/utlpwdmg.sql" script.

If you have trouble thinking of strong passwords, try using a password generator like RandPass.com. It creates random strong passwords with a phonetic sound, making them easier to remember.

Revoke Job-Related Privileges

Prior to Oracle 10g, every user with access to the DBMS_JOB package had the ability to schedule database jobs. In these versions this does not represent an obvious security risk, but it allows users to schedule untuned and intensive operations that can reduce database performance. For this reason I suggest removing public access to the DBMS_JOB package.
REVOKE EXECUTE ON dbms_job FROM PUBLIC;
Oracle 10g Release 1 (10.1.0) introduced a new scheduler, along with the concept of external jobs. This scheduler is secured with two new privileges (CREATE JOB and CREATE ANY JOB), neither of which are granted by default. At first this seems like an improvement, but the ability to create a job as any user allows the grantee full access to the SYS user and its privileges. I see no reason to ever grant a user the CREATE ANY JOB privilege, and I would avoid granting the CREATE JOB privilege if possible.

External jobs present an equally large threat as they allow access to the full power of the underlying operating system, including OS authentication connections to the database. In Oracle 10g Release 1 there is no distinction between an internal job and an external job as far as privileges are concerned, so even the CREATE JOB privilege represents a massive security breach. In Oracle 10g Release 2 (10.2.0) this situation is improved by the addition of the CREATE EXTERNAL JOB privilege, allowing access to internal and external jobs to be granted separately. Even so, access to the scheduler should be guarded very carefully.

Revoke Unnecessary Privileges

As a rule of thumb, you should grant users the smallest number of privileges necessary to do their job.

Meatlink Note:340009.1 discusses the Oracle Voyager Worm and suggests that removal of excessive privileges may prevent attacks from happening in the first place, or spreading from a compromised system.
REVOKE CREATE DATABASE LINK FROM connect;
REVOKE EXECUTE ON utl_tcp FROM public;
REVOKE EXECUTE ON utl_smtp FROM public;
REVOKE EXECUTE ON utl_http FROM public;
REVOKE EXECUTE ON utl_mail FROM public;
REVOKE EXECUTE ON utl_inaddr FROM public;
REVOKE EXECUTE ON utl_file FROM public;
REVOKE EXECUTE ON dbms_java FROm public;
In the same way, granting excessive numbers of roles may be dangerous. Instead create you own roles that contain only necessary privileges.

Securing the Listener

The TNS listener should be password protected using the lsnrctl utility or the netmgr GUI. When using the lsnrctl utility, the change_password command is used to set the password for the first time, or to change an existing password.
LSNRCTL> change_password
Old password:
New password:
Reenter new password:
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=myserver.mydomain)(PORT=1521)))
Password changed for LISTENER
The command completed successfully
LSNRCTL>
The "Old password:" value should be left blank if the password is being set for the first time. Once the new password is set, the configuration should be saved using the save_config command.
LSNRCTL> save_config
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=myserver.mydomain)(PORT=1521)))
Saved LISTENER configuration parameters.
Listener Parameter File   /u01/app/oracle/product/10.1.0/db_1/network/admin/listener.ora
Old Parameter File   /u01/app/oracle/product/10.1.0/db_1/network/admin/listener.bak
The command completed successfully
LSNRCTL>
Once the password is set, subsequent attempts to perform privileged operations such as save_config and stop will fail unless the password is set using the set password command.
LSNRCTL> set password
Password:
The command completed successfully
LSNRCTL>
The image below shows the same operation being performed by the Oracle Net Manager (netmgr) GUI.

Setting the listener password using Net Manager (netmgr).

In addition to password protection, Meatlink Note:340009.1 suggests changing the TNS listener default port from 1521 to a different port. This will certainly help prevent generic attacks where worms are specifically targeting port 1521, but will only cause a minor delay for a targeted hack where open ports are scanned.

The TNS listener port settings are configured by editing the "$ORACLE_HOME/network/admin/listener.ora" file and restarting, or reloading, the listener. In addition, the LDAP entries or local "$ORACLE_HOME/network/admin/tnsnames.ora" file entries of any clients must be modified to reflect the changes.

Client access to the server can be restricted by adding the following entries to the "$ORACLE_HOME/network/admin/protocol.ora" file.
tcp.validnode_checking = YES
tcp.excluded_nodes = {list of IP addresses}
tcp.invited_nodes = {list of IP addresses}
This may work OK in a 3-tier architecture where only a small number of applicaton servers connect to the database.

Miscellaneous

For more information see:
Hope this helps. Regards Tim...

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