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  2. DBMS_FGA

70 DBMS_FGA

The DBMS_FGA package provides fine-grained security functions.

This chapter contains the following topics:

70.1 DBMS_FGA Security Model

You must have the AUDIT_ADMIN role or the EXECUTE privilege on the DBMS_FGA package to create audit policies. DBMS_FGA is an invoker rights package.

To analyze and audit data, you must have the AUDIT_VIEWER role. Because the audit function can potentially capture all user environment and application context values, policy administration should be executable by privileged users only. The policy event handler module is executed with the module owner’s privilege.

70.2 DBMS_FGA Operational Notes

This package is available for only cost-based optimization. The rule-based optimizer may generate unnecessary audit records since audit monitoring can occur before row filtering.

For both the rule-based optimizer and the cost-based optimizer, you can query the SQL_TEXT and SQL_BINDS columns of the UNIFIED_AUDIT_TRAIL view to analyze the SQL text and corresponding bind variables that are issued.

70.3 Summary of DBMS_FGA Subprograms

This table lists the DBMS_FGA subprograms and briefly describes them.

Table 70-1 DBMS_FGA Package Subprograms

Subprogram Description

ADD_POLICY Procedure

Creates an audit policy using the supplied predicate as the audit condition

DISABLE_POLICY Procedure

Disables an audit policy

DROP_POLICY Procedure

Drops an audit policy

ENABLE_POLICY Procedure

Enables an audit policy

70.3.1 ADD_POLICY Procedure

This procedure creates an audit policy using the supplied predicate as the audit condition.

Syntax

DBMS_FGA.ADD_POLICY(
   object_schema      IN  VARCHAR2 DEFAULT NULL, 
   object_name        IN  VARCHAR2, 
   policy_name        IN  VARCHAR2, 
   audit_condition    IN  VARCHAR2 DEFAULT NULL, 
   audit_column       IN  VARCHAR2 DEFAULT NULL, 
   handler_schema     IN  VARCHAR2 DEFAULT NULL, 
   handler_module     IN  VARCHAR2 DEFAULT NULL, 
   enable             IN  BOOLEAN DEFAULT TRUE, 
   statement_types    IN  VARCHAR2 DEFAULT SELECT,
   audit_trail        IN  BINARY_INTEGER DEFAULT NULL,
   audit_column_opts  IN  BINARY_INTEGER DEFAULT ANY_COLUMNS,
   policy_owner       IN  VARCHAR2 DEFAULT NULL);

Parameters

Table 70-2 ADD_POLICY Procedure Parameters

Parameter Description

object_schema

Schema of the object to be audited. If NULL, the current schema is assumed.

object_name

Name of the object to be audited

policy_name

Unique name of the policy. Do not enter special characters such as spaces or commas. If you want to use special characters for the policy name, then enclose the name in quotation marks.

audit_condition

A condition in a row that indicates a monitoring condition. NULL is allowed and acts as TRUE.

audit_column

Columns to be checked for access. These can include OLS hidden columns or object type columns. The default, NULL, causes audit if any column is accessed or affected.

handler_schema

Schema that contains the event handler. The default, NULL, causes the current schema to be used.

handler_module

Function name of the event handler; includes the package name if necessary. This function is invoked only after the first row that matches the audit condition in the query is processed. If the procedure fails with an exception, the user SQL statement will fail as well.

enable

Enables the policy if TRUE, which is the default

statement_types

SQL statement types to which this policy is applicable: INSERT, UPDATE, DELETE, or SELECT only

audit_trail

In an environment that has not yet migrated to unified auditing, the destination (DB or XML) of fine-grained audit records. Also specifies whether to populate the LSQLTEXT and LSQLBIND columns in the FGA_LOG$ system table.

audit_column_opts

Establishes whether a statement is audited when the query references any column specified in the audit_column parameter or only when all such columns are referenced

policy_owner

User who owns the fine-grained auditing policy. However, this setting is not a user-supplied argument. The Oracle Data Pump client uses this setting internally to recreate the fine-grained audit policies appropriately.

Usage Notes

  • A table or view can have a maximum of 256 fine-grained audit policies applied to it.

  • If object_schema is not specified, the current schema is assumed.

  • An FGA policy should not be applied to out-of-line columns such as LOB columns.

  • Each audit policy is applied to the query individually. However, at most one audit record may be generated for each policy, no matter how many rows being returned satisfy that policy's audit_condition. In other words, whenever any number of rows being returned satisfy an audit condition defined on the table, a single audit record will be generated for each such policy.

  • If a table with an FGA policy defined on it receives a Fast Path insert or a vectored update, the hint is automatically disabled before any such operations. Disabling the hint allows auditing to occur according to the policy's terms. (One example of a Fast Path insert is the statement INSERT-WITH-APPEND-hint.)

  • The audit_condition must be a boolean expression that can be evaluated using the values in the row being inserted, updated, or deleted. The expression can also use functions, such as the USER or SYS_CONTEXT functions.

    The expression must not combine conditions using operators such as AND and OR. audit_condition can be NULL (or omitted), which is interpreted as TRUE, but it cannot contain the following elements:

    • Subqueries or sequences

    • The following attributes of the USERENV namespace when accessed using the SYS_CONTEXT function:

      • CURRENT_SQL

      • CURRENT_SQL_LENGTH

      • CURRENT_BIND

    • Any use of the pseudo columns LEVEL, PRIOR, or ROWNUM.

    Specifying an audit condition of "1=1" to force auditing of all specified statements ("statement_types") affecting the specified column ("audit_column") is no longer needed to achieve this purpose. A NULL value for audit_condition causes audit to happen even if no rows are processed, so that all actions on a table with this policy are audited.

  • The audit_condition is evaluated using the privileges of the user who creates the policy.

  • For the audit_condition setting, do not include functions, which execute the auditable statement on the same base table, in the audit_condition setting. For example, suppose you create a function that executes an INSERT statement on the HR.EMPLOYEES table. The policy audit_condition contains this function and it is for INSERT statements (as set by the statement_types parameter). When the policy is used, the function executes recursively until the system has run out of memory. This can raise the error ORA-1000: maximum open cursors exceeded or ORA-00036: maximum number of recursive SQL levels (50) exceeded.

  • Do not issue the DBMS_FGA.ENABLE_POLICY or DBMS_FGA.DISABLE_POLICY statement from a policy function in a condition.

  • The audit function (handler_module) is an alerting mechanism for the administrator. The required interface for such a function is as follows: 

    PROCEDURE fname ( object_schema VARCHAR2, object_name VARCHAR2, policy_name VARCHAR2 )  AS ...

    where fname is the name of the procedure, object_schema is the name of the schema of the table audited, object_name is the name of the table to be audited, and policy_name is the name of the policy being enforced. The audit function will be executed with the function owner's privilege.

  • If you have migrated to unified auditing, then omit the audit_trail parameter because the audit records will automatically be written to the unified audit trail.

  • Be aware that sensitive data, such as credit card information, can be recorded in clear text.

  • The audit_trail parameter, if used, specifies both where the fine-grained audit trail will be written and whether it is to include the query's SQL Text and SQL Bind variable information (typically in columns named LSQLTEXT and LSQLBIND):

    • If audit_trail includes XML, then fine-grained audit records are written to XML-format operating system files stored in the directory specified by an AUDIT_FILE_DEST statement in SQL. (The default AUDIT_FILE_DEST is $ORACLE_BASE/admin/$DB_UNIQUE_NAME/adump on Unix-based systems, and $ORACLE_BASE\admin\$DB_UNIQUE_NAME\adump on Windows systems.)

    • If audit_trail includes DB instead, then the audit records are written to the SYS.FGA_LOG$ table in the database. However, for read-only databases, Oracle Database writes the fine-grained audit records to XML files, regardless of the audit_trail settings.

    • If audit_trail includes EXTENDED, then the query's SQL Text and SQL Bind variable information are included in the audit trail.

    • For example:

      • Setting audit_trail to DBMS_FGA.DB sends the audit trail to the SYS.FGA_LOG$ table in the database and omits SQL Text and SQL Bind.

      • Setting audit_trail to DBMS_FGA.DB + DBMS_FGA.EXTENDED sends the audit trail to the SYS.FGA_LOG$ table in the database and includes SQL Text and SQL Bind.

      • Setting audit_trail to DBMS_FGA.XML writes the audit trail in XML files sent to the operating system and omits SQL Text and SQL Bind.

      • Setting audit_trail to DBMS_FGA.XML + DBMS_FGA.EXTENDED writes the audit trail in XML files sent to the operating system and includes SQL Text and SQL Bind.

    The audit_trail parameter appears in the ALL_AUDIT_POLICIES view.

  • You can change the operating system destination using the following command:

    ALTER SYSTEM SET AUDIT_FILE_DEST =  New Directory DEFERRED

  • On many platforms, XML audit files are named process_name_processId.xml, for example, ora_2111.xml. Alternatively,l on Windows, the XML audit files are named process_name_ThreadId.xml (or process_name_ProcessId.xml if the process is not running as a thread).

  • The audit_column_opts parameter establishes whether a statement is audited

    • when the query references any column specified in the audit_column parameter (audit_column_opts = DBMS_FGA.ANY_COLUMNS), or

    • only when all such columns are referenced (audit_column_opts = DBMS_FGA.ALL_COLUMNS).

    The default is DBMS_FGA.ANY_COLUMNS.

    The ALL_AUDIT_POLICIES view also shows audit_column_opts.

  • When audit_column_opts is set to DBMS_FGA.ALL_COLUMNS, a SQL statement is audited only when all the columns mentioned in audit_column have been explicitly referenced in the statement. And these columns must be referenced in the same SQL-statement or in the sub-select.

    All these columns must refer to a single table/view or alias.

    If a SQL statement selects the columns from different table aliases, the statement will not be audited.

  • Every XML audit record contains the elements AUDIT_TYPE and EXTENDED_TIMESTAMP, with the latter printed in UTC zone (with no timezone information). Values retrieved using V$XML_AUDIT_TRAIL view are converted to session timezone and printed.

  • For SQL_TEXT and SQL_BIND element values (CLOB type columns), the dynamic view shows only the first 4000 characters. The underlying XML file may have more than 4000 characters for such SQL_TEXT and SQL_BIND values.

  • For large numbers of XML audit files, querying V$XML_AUDIT_TRAIL is faster when they are loaded into a database table using SQL*Loader or a similar tool. XML audit files are larger than the equivalent written to OS files when AUDIT_TRAIL=OS.

  • Error handling is the same as when AUDIT_TRAIL=OS. If any error occurs in writing an audit record to disk, including the directory identified by AUDIT_FILE_DEST being full, the auditing operation fails. An alert message is logged.

  • The policy event handler module will be executed with the module owner's privilege.

  • Do not create recursive fine-grained audit handlers. For example, suppose you create a handler that executes an INSERT statement on the HR.EMPLOYEES table. The policy that is associated with this handler is for INSERT statements (as set by the statement_types parameter). When the policy is used, the handler executes recursively until the system has run out of memory. This can raise the error ORA-1000: maximum open cursors exceeded or ORA-00036: maximum number of recursive SQL levels (50) exceeded. See also Oracle Database Security Guide with regard to Creating a Fine-Grained Audit Policy.

  • The fine-grained audit handler module should not have explicit COMMIT, ROLLBACK, and DDL statements mentioned in it.

  • The values for the audit_trail parameter (XML and XML+EXTENDED) cause fine-grained auditing records to be written to operating system files in XML format. A dynamic view, V$XML_AUDIT_TRAIL, makes such audit records from XML files available to DBAs through SQL query, providing enhanced usability. Querying this view causes all XML files (all files with an.xml extension) in the AUDIT_FILE_DEST directory to be parsed and presented in relational table format.

    Audit records stored in operating system files can be more secure than database-stored audit records because access can require file permissions that DBAs do not have. Operating system storage for audit records also offers higher availability, since such records remain available even if the database is temporarily inaccessible.

    The DBA_COMMON_AUDIT_TRAIL view includes the contents of the V$XML_AUDIT_TRAIL dynamic view for standard and fine-grained audit records.

    Note that the V$XML_AUDIT_TRAIL view is populated only if unified auditing is not enabled. If you have enabled unified auditing, then you can query the UNIFIED_AUDIT_TRAIL data dictionary view for the audit trail records.

See Also:

Oracle Database Security Guide for an example of creating an email alert handler for a fine-grained audit policy

Examples 

DBMS_FGA.ADD_POLICY (
   object_schema      =>  'scott', 
   object_name        =>  'emp', 
   policy_name        =>  'mypolicy1', 
   audit_condition    =>  'sal < 100', 
   audit_column       =>  'comm,sal', 
   handler_schema     =>   NULL, 
   handler_module     =>   NULL, 
   enable             =>   TRUE, 
   statement_types    =>  'INSERT, UPDATE', 
   audit_column_opts  =>   DBMS_FGA.ANY_COLUMNS,
   policy_owner       =>  'sec_admin);

70.3.2 DISABLE_POLICY Procedure

This procedure disables an audit policy.

Syntax

DBMS_FGA.DISABLE_POLICY(
   object_schema  IN  VARCHAR2, 
   object_name    IN  VARCHAR2, 
   policy_name    IN  VARCHAR2);

Parameters

Table 70-3 DISABLE_POLICY Procedure Parameters

Parameter Description

object_schema

Schema of the object to be audited. If NULL, the current schema is assumed.

object_name

Name of the object to be audited

policy_name

Unique name of the policy

The default value for object_schema is NULL. If NULL, the current schema is assumed.

Examples

DBMS_FGA.DISABLE_POLICY (
object_schema   =>  'scott',
object_name     =>  'emp',
policy_name     =>  'mypolicy1');

70.3.3 DROP_POLICY Procedure

This procedure drops an audit policy.

Syntax

DBMS_FGA.DROP_POLICY(
   object_schema  IN  VARCHAR2, 
   object_name    IN  VARCHAR2, 
   policy_name    IN  VARCHAR2);

Parameters

Table 70-4 DROP_POLICY Procedure Parameters

Parameter Description

object_schema

Schema of the object to be audited. If NULL, the current schema is assumed.

object_name

Name of the object to be audited

policy_name

Unique name of the policy

Usage Notes

The DBMS_FGA procedures cause current DML transactions, if any, to commit before the operation unless they are inside a DDL event trigger. With DDL transactions, the DBMS_FGA procedures are part of the DDL transaction. The default value for object_schema is NULL. If NULL, the current schema is assumed.

Note:

Oracle Database automatically drops the audit policy if you remove the object specified in the object_name parameter of the DBMS_FGA.ADD_POLICY procedure, or if you drop the user who created the audit policy.

Examples

DBMS_FGA.DROP_POLICY (
object_schema   =>  'scott',
object_name     =>  'emp',
policy_name     =>  'mypolicy1');

70.3.4 ENABLE_POLICY Procedure

This procedure enables an audit policy.

Syntax

DBMS_FGA.ENABLE_POLICY(
   object_schema  IN  VARCHAR2,
   object_name    IN  VARCHAR2,
   policy_name    IN  VARCHAR2,
   enable         IN  BOOLEAN);

Parameters

Table 70-5 ENABLE_POLICY Procedure Parameters

Parameter Description

object_schema

Schema of the object to be audited. If NULL, the current schema is assumed.

object_name

Name of the object to be audited

policy_name

Unique name of the policy

enable

Defaults to TRUE to enable the policy

Examples

DBMS_FGA.ENABLE_POLICY (
object_schema    =>  'scott',
object_name      =>  'emp',
policy_name      =>  'mypolicy1',
enable           =>   TRUE);