Auditing in Oracle 10g Release 2

This article presents an overview of auditing in Oracle 10g Release 2. Many of the topics presented here have been covered in previous articles, but this serves to bring them all together.

Server Setup

Auditing is a default feature of the Oracle server. The initialization parameters that influence its behaviour can be displayed using the SHOW PARAMETER SQL*Plus command.

SQL> SHOW PARAMETER AUDIT

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
audit_file_dest                      string      C:\ORACLE\PRODUCT\10.2.0\ADMIN
                                                 \DB10G\ADUMP
audit_sys_operations                 boolean     FALSE
audit_trail                          string      NONE
SQL>

Auditing is disabled by default, but can enabled by setting the AUDIT_TRAIL static parameter, which has the following allowed values.

AUDIT_TRAIL = { none | os | db | db,extended | xml | xml,extended }

The following list provides a description of each setting:

none or false - Auditing is disabled.
db or true - Auditing is enabled, with all audit records stored in the database audit trial (SYS.AUD$).
db,extended - As db, but the SQL_BIND and SQL_TEXT columns are also populated.
xml- Auditing is enabled, with all audit records stored as XML format OS files.
xml,extended - As xml, but the SQL_BIND and SQL_TEXT columns are also populated.
os- Auditing is enabled, with all audit records directed to the operating system's audit trail.

Note. In Oracle 10g Release 1, db_extended was used in place of db,extended. The XML options are new to Oracle 10g Release 2.

The AUDIT_SYS_OPERATIONS static parameter enables or disables the auditing of operations issued by users connecting with SYSDBA or SYSOPER privileges, including the SYS user. All audit records are written to the OS audit trail.

The AUDIT_FILE_DEST parameter specifies the OS directory used for the audit trail when the os, xml and xml,extended options are used. It is also the location for all mandatory auditing specified by the AUDIT_SYS_OPERATIONS parameter.

To enable auditing and direct audit records to the database audit trail, we would do the following.

SQL> ALTER SYSTEM SET audit_trail=db SCOPE=SPFILE;

System altered.

SQL> SHUTDOWN
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> STARTUP
ORACLE instance started.

Total System Global Area  289406976 bytes
Fixed Size                  1248600 bytes
Variable Size              71303848 bytes
Database Buffers          213909504 bytes
Redo Buffers                2945024 bytes
Database mounted.
Database opened.
SQL>

Audit Options

One look at the AUDIT command syntax should give you an idea of how flexible Oracle auditing is. There is no point repeating all this information, so instead we will look at a simple example.

First we create a new user called AUDIT_TEST.

CONNECT sys/password AS SYSDBA

CREATE USER audit_test IDENTIFIED BY password
  DEFAULT TABLESPACE users
  TEMPORARY TABLESPACE temp
  QUOTA UNLIMITED ON users;

GRANT connect TO audit_test;
GRANT create table, create procedure TO audit_test;

Next we audit all operations by the AUDIT_TEST user.

CONNECT sys/password AS SYSDBA

AUDIT ALL BY audit_test BY ACCESS;
AUDIT SELECT TABLE, UPDATE TABLE, INSERT TABLE, DELETE TABLE BY audit_test BY ACCESS;
AUDIT EXECUTE PROCEDURE BY audit_test BY ACCESS;

These options audit all DDL and DML, along with some system events.

DDL (CREATE, ALTER & DROP of objects)
DML (INSERT UPDATE, DELETE, SELECT, EXECUTE).
SYSTEM EVENTS (LOGON, LOGOFF etc.)

Next, we perform. some operations that will be audited.

CONN audit_test/password

CREATE TABLE test_tab (
  id  NUMBER
);

INSERT INTO test_tab (id) VALUES (1);
UPDATE test_tab SET id = id;
SELECT * FROM test_tab;
DELETE FROM test_tab;

DROP TABLE test_tab;

In the next section we will look at how we view the contents of the audit trail.

View Audit Trail

The audit trail is stored in the SYS.AUD$ table. Its contents can be viewed directly or via the following views:

SELECT view_name
FROM   dba_views
WHERE  view_name LIKE 'DBA%AUDIT%'
ORDER BY view_name;

VIEW_NAME
------------------------------
DBA_AUDIT_EXISTS
DBA_AUDIT_OBJECT
DBA_AUDIT_POLICIES
DBA_AUDIT_POLICY_COLUMNS
DBA_AUDIT_SESSION
DBA_AUDIT_STATEMENT
DBA_AUDIT_TRAIL
DBA_COMMON_AUDIT_TRAIL
DBA_FGA_AUDIT_TRAIL
DBA_OBJ_AUDIT_OPTS
DBA_PRIV_AUDIT_OPTS
DBA_REPAUDIT_ATTRIBUTE
DBA_REPAUDIT_COLUMN
DBA_STMT_AUDIT_OPTS

14 rows selected.

SQL>

The three main views are:

DBA_AUDIT_TRAIL - Standard auditing only (from AUD$).
DBA_FGA_AUDIT_TRAIL - Fine-grained auditing only (from FGA_LOG$).
DBA_COMMON_AUDIT_TRAIL - Both standard and fine-grained auditing.

The most basic view of the database audit trail is provided by the DBA_AUDIT_TRAIL view, which contains a wide variety of information. The following query displays the some of the information from the database audit trail.

COLUMN username FORMAT A10
COLUMN owner    FORMAT A10
COLUMN obj_name FORMAT A10
COLUMN extended_timestamp FORMAT A35

SELECT username,
       extended_timestamp,
       owner,
       obj_name,
       action_name
FROM   dba_audit_trail
WHERE  wner = 'AUDIT_TEST'
ORDER BY timestamp;

USERNAME   EXTENDED_TIMESTAMP                  OWNER      OBJ_NAME   ACTION_NAME
---------- ----------------------------------- ---------- ---------- ----------------------------
AUDIT_TEST 16-FEB-2006 14:16:55.435000 +00:00  AUDIT_TEST TEST_TAB   CREATE TABLE
AUDIT_TEST 16-FEB-2006 14:16:55.514000 +00:00  AUDIT_TEST TEST_TAB   INSERT
AUDIT_TEST 16-FEB-2006 14:16:55.545000 +00:00  AUDIT_TEST TEST_TAB   UPDATE
AUDIT_TEST 16-FEB-2006 14:16:55.592000 +00:00  AUDIT_TEST TEST_TAB   SELECT
AUDIT_TEST 16-FEB-2006 14:16:55.670000 +00:00  AUDIT_TEST TEST_TAB   DELETE
AUDIT_TEST 16-FEB-2006 14:17:00.045000 +00:00  AUDIT_TEST TEST_TAB   DROP TABLE

6 rows selected.

SQL>

When the audit trail is directed to an XML format OS file, it can be read using a text editor or via the V$XML_AUDIT_TRAIL view, which contains similar information to the DBA_AUDIT_TRAIL view.

COLUMN db_user       FORMAT A10
COLUMN object_schema FORMAT A10
COLUMN object_name   FORMAT A10
COLUMN extended_timestamp FORMAT A35

SELECT db_user,
       extended_timestamp,
       object_schema,
       object_name,
       action
FROM   v$xml_audit_trail
WHERE  object_schema = 'AUDIT_TEST'
ORDER BY extended_timestamp;

DB_USER    EXTENDED_TIMESTAMP                  OBJECT_SCH OBJECT_NAM     ACTION
---------- ----------------------------------- ---------- ---------- ----------
AUDIT_TEST 16-FEB-2006 14:14:33.417000 +00:00  AUDIT_TEST TEST_TAB            1
AUDIT_TEST 16-FEB-2006 14:14:33.464000 +00:00  AUDIT_TEST TEST_TAB            2
AUDIT_TEST 16-FEB-2006 14:14:33.511000 +00:00  AUDIT_TEST TEST_TAB            6
AUDIT_TEST 16-FEB-2006 14:14:33.542000 +00:00  AUDIT_TEST TEST_TAB            3
AUDIT_TEST 16-FEB-2006 14:14:33.605000 +00:00  AUDIT_TEST TEST_TAB            7
AUDIT_TEST 16-FEB-2006 14:14:34.917000 +00:00  AUDIT_TEST TEST_TAB           12

6 rows selected.

SQL>

Several fields were added to both the standard and fine-grained audit trails in Oracle 10g, including:

EXTENDED_TIMESTAMP - A more precise value than the exising TIMESTAMP column.
PROXY_SESSIONID - Proxy session serial number when an enterprise user is logging in via the proxy method.
GLOBAL_UID - Global Universal Identifier for an enterprise user.
INSTANCE_NUMBER - The INSTANCE_NUMBER value from the actioning instance.
OS_PROCESS - Operating system process id for the oracle process.
TRANSACTIONID - Transaction identifier for the audited transaction. This column can be used to join to the XID column on the FLASHBACK_TRANSACTION_QUERY view.
SCN - System change number of the query. This column can be used in flashback queries.
SQL_BIND - The values of any bind variables if any.
SQL_TEXT - The SQL statement that initiated the audit action.

The SQL_BIND and SQL_TEXT columns are only populated when the AUDIT_TRAIL parameter is set to db,extended or xml,extended.

Maintenance and Security

Auditing should be planned carefully to control the quantity of audit information. Only audit specific operations or objects of interest. Over time you can refine the level of auditing to match your requirements.

The database audit trail must be deleted, or archived, on a regular basis to prevent the SYS.AUD$ table growing to an unnacceptable size.Only DBAs should have maintenance access to the audit trail. Auditing modifications of the data in the audit trail itself can be achieved using the following statement:

AUDIT INSERT, UPDATE, DELETE ON sys.aud$ BY ACCESS;

The OS and XML audit trails are managed through the OS. These files should be secured at the OS level by assigning the correct file permissions.

Fine Grained Auditing (FGA)

Fine grained auditing extends Oracle standard auditing capabilities by allowing the user to audit actions based on user-defined predicates. It is independant of the AUDIT_TRAIL parameter setting and all audit records are stored in the FGA_LOG$ table, rather than the AUD$ table. The following example illustrates how fine grained auditing is used.

First, create a test table.

CONN audit_test/password

CREATE TABLE emp (
 empno     NUMBER(4) NOT NULL,
 ename     VARCHAR2(10),
 job       VARCHAR2(9),
 mgr       NUMBER(4),
 hiredate  DATE,
 sal       NUMBER(7,2),
 comm      NUMBER(7,2),
 deptno    NUMBER(2)
);

INSERT INTO emp (empno, ename, sal) VALUES (9999, 'Tim', 1);
INSERT INTO emp (empno, ename, sal) VALUES (9999, 'Larry', 50001);
COMMIT;

The following policy audits any queries of salaries greater than £50,000.

CONN sys/password AS sysdba

BEGIN
  DBMS_FGA.add_policy(
    object_schema   => 'AUDIT_TEST',
    object_name     => 'EMP',
    policy_name     => 'SALARY_CHK_AUDIT',
    audit_condition => 'SAL > 50000',
    audit_column    => 'SAL');
END;
/

Querying both employees proves the auditing policy works as expected.

CONN audit_test/password
SELECT sal FROM emp WHERE ename = 'Tim';
SELECT sal FROM emp WHERE ename = 'Larry';

CONN sys/password AS SYSDBA
SELECT sql_text
FROM   dba_fga_audit_trail;

SQL_TEXT
------------------------------------------
SELECT sal FROM emp WHERE ename = 'Larry'

1 row selected.

SQL>

Extra processing can be associated with an FGA event by defining a database procedure and associating this to the audit event. The following example assumes the FIRE_CLERK procedure has been defined:

BEGIN
  DBMS_FGA.add_policy(
    object_schema   => 'AUDIT_TEST',
    object_name     => 'EMP',
    policy_name     => 'SALARY_CHK_AUDIT',
    audit_condition => 'SAL > 50000',
    audit_column    => 'SAL',
    handler_schema  => 'AUDIT_TEST',
    handler_module  => 'FIRE_CLERK',
    enable          => TRUE);
END;
/

The DBMS_FGA package contains the following procedures:

ADD_POLICY
DROP_POLICY
ENABLE_POLICY
DISABLE_POLICY

In Oracle9i fine grained auditing was limited queries, but in Oracle 10g it has been extended to include DML statements, as shown by the following example.

-- Clear down the audit trail.
CONN sys/password AS SYSDBA
TRUNCATE TABLE fga_log$;
SELECT sql_text FROM dba_fga_audit_trail;

no rows selected.

-- Apply the policy to the SAL column of the EMP table.
BEGIN
  DBMS_FGA.add_policy(
    object_schema   => 'AUDIT_TEST',
    object_name     => 'EMP',
    policy_name     => 'SAL_AUDIT',
    audit_condition => NULL, -- Equivalent to TRUE
    audit_column    => 'SAL',
    statement_types => 'SELECT,INSERT,UPDATE,DELETE');
END;
/

-- Test the auditing.
CONN audit_test/password
SELECT * FROM emp WHERE empno = 9998;
INSERT INTO emp (empno, ename, sal) VALUES (9998, 'Bill', 1);
UPDATE emp SET sal = 10 WHERE empno = 9998;
DELETE emp WHERE empno = 9998;
ROLLBACK;

-- Check the audit trail.
CONN sys/password AS SYSDBA
SELECT sql_text FROM dba_fga_audit_trail;

SQL_TEXT
--------------------------------------
SELECT * FROM emp WHERE empno = 9998
INSERT INTO emp (empno, ename, sal) VALUES (9998, 'Bill', 1)
UPDATE emp SET sal = 10 WHERE empno = 9998
DELETE emp WHERE empno = 9998

4 rows selected.

-- Drop the policy.
CONN sys/password AS SYSDBA
BEGIN
  DBMS_FGA.drop_policy(
    object_schema   => 'AUDIT_TEST',
    object_name     => 'EMP',
    policy_name     => 'SAL_AUDIT');
END;
/

For more information see:

Hope this helps. Regards Tim...

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